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Friday, January 14, 2011

Java FAQ's Volume1

1)What is OOPs?
Ans: Object oriented programming organizes a program around its data,i.e.,objects and a set of well defined interfaces to that data.An object-oriented program can be characterized as data controlling access to code.
2)what is the difference between Procedural and OOPs?
Ans: a) In procedural program, programming logic follows certain procedures and the instructions are executed one after another. In OOPs program, unit of program is object, which is nothing but combination of data and code.
b) In procedural program,data is exposed to the whole program whereas in OOPs program,it is accessible with in the object and which in turn assures the security of the code.
3)What are Encapsulation, Inheritance and Polymorphism?
Ans: Encapsulation is the mechanism that binds together code and data it manipulates and keeps both safe from outside interference and misuse.Inheritance is the process by which one object acquires the properties of another object.Polymorphism is the feature that allows one interface to be used for general class actions.
4)What is the difference between Assignment and Initialization?
Ans: Assignment can be done as many times as desired whereas initialization can be done only once.
5)What are Class, Constructor and Primitive data types?
Ans: Class is a template for multiple objects with similar features and it is a blue print for objects. It defines a type of object according to the data the object can hold and the operations the object can perform. Constructor is a special kind of method that determines how an object is initialized when created.
Primitive data types are 8 types and they are:
byte, short, int, long
float, double
boolean
char

6)What is an Object and how do you allocate memory to it?
Ans: Object is an instance of a class and it is a software unit that combines a structured set of data with a set of  operations for inspecting and manipulating that data. When an object is created using new operator, memory is allocated to it.
7)What is the difference between constructor and method?  Ans: Constructor will be automatically invoked when an object is created whereas method has to be called explicitly.
8)What are methods and how are they defined?
Ans: Methods are functions that operate on instances of classes in which they are defined. Objects can communicate with each other using methods and can call methods in other classes.Method definition has four parts. They are name of the method, type of object or primitive type the method returns, a list of parameters and the body of the method. A method’s signature is a combination of the first three parts mentioned above.
9)What is the use of bin and lib in JDK?
Ans: Bin contains all tools such as javac, appletviewer, awt tool, etc., whereas lib contains API and all packages.
10)What is casting?
Ans: Casting is used to convert the value of one type to another.
11)How many ways can an argument be passed to a subroutine and explain them?
Ans: An argument can be passed in two ways. They are passing by value and passing by reference.Passing by value: This method copies the value of an argument into the formal parameter of the subroutine.Passing by reference: In this method, a reference to an argument (not the value of the argument) is passed to the parameter.
12)What is the difference between an argument and a parameter?
Ans: While defining method, variables passed in the method are called parameters. While using those methods, values passed to those variables are called arguments.
13)What are different types of access modifiers?
Ans: public: Any thing declared as public can be accessed from anywhere.
private: Any thing declared as private can’t be seen outside of its class.
protected: Any thing declared as protected can be accessed by classes in the same package and subclasses in the other packages.
default modifier : Can be accessed only to classes in the same package.
14)What is final, finalize() and finally?
Ans: final : final keyword can be used for class, method and variables.A final class cannot be subclassed and it prevents other programmers from subclassing a secure class to invoke insecure methods.A final method can’ t be overriddenA final variable can’t change from its initialized value.finalize( ) : finalize( ) method is used just before an object is destroyed and can be called just prior to garbage collecollection   finally : finally, a key word used in exception handling, creates a block of code that will be
executed after a try/catch block has completed and before the code following the try/catch block. The finally block will execute whether or not an exception is thrown. For example, if a method opens a file upon exit, then you will not want the code that closes the file to be bypassed by the exception-handling mechanism. This finally keyword is designed to address this
contingency.      
15)What is UNICODE?
Ans: Unicode is used for internal representation of characters and strings and it uses 16 bits to represent each other.
16)What is Garbage Collection and how to call it explicitly?
Ans: When an object is no longer referred to by any variable, java automatically reclaims memory used by that object. This is known as garbage collection.System.gc() method may be used to call it explicitly.
17)What is  finalize() method ?
Ans: finalize () method is used just before an object is destroyed and can be called just prior to garbage collection.
18)What are Transient and Volatile Modifiers?
Ans: Transient: The transient modifier applies to variables only and it is not stored as part of its object’s Persistent state. Transient variables are not serialized.Volatile: Volatile modifier applies to variables only and it tells the compiler that the variable modified by volatile can be changed unexpectedly by other parts of the program.
19)What is method overloading and method overriding?
Ans: Method overloading: When a method in a class having the same method name with different arguments is said to be method overloading.
Method overriding : When a method in a class having the same method name with same arguments is said to be method overriding.
20)What is difference between overloading and overriding?
Ans: a) In overloading, there is a relationship between methods available in the same class whereas in overriding, there is relationship between a superclass method and subclass method.
b) Overloading does not block inheritance from the superclass whereas overriding blocks inheritance from the superclass.
c) In overloading, separate methods share the same name whereas in overriding,subclass method replaces the superclass.
d) Overloading must have different method signatures whereas overriding  must have same signature.

21) What is meant by Inheritance and what are its advantages?
Ans: Inheritance is the process of inheriting all the features from a class. The advantages of inheritance are reusability of code and accessibility of variables and methods of the super class by subclasses.
22)What is the difference between this() and super()?
Ans: this() can be used to invoke a constructor of the same class whereas super() can be used to invoke a super class constructor.
23)What is the difference between superclass and subclass?

Ans: A super class is a class that is inherited whereas sub class is a classthat does the inheriting.

24) What modifiers may be used with top-level class?
Ans: public, abstract and final can be used for top-level class.
25)What are inner class and anonymous class?
Ans: Inner class  : classes defined in other classes, including those defined in methods are called  inner classes. An inner class can have any accessibility including private.Anonymous class : Anonymous class is a class defined inside a method without a name and is instantiated and declared in the same place and cannot have explicit constructors.
26)What is a package?
Ans: A package is a collection of classes and interfaces that provides a high-level layer of access protection and name space management.

27)   What is a reflection package? 

Ans: java.lang.reflect package has the ability to analyze itself in runtime.

28)   What is interface and its use?

Ans:Interface is similar to a class which may contain method’s signature only but not bodies and  it is
a formal set of method and constant declarations that must be defined by the class that implements it.
Interfaces are useful for:
a)Declaring methods that one or more classes are expected to implement
b)Capturing similarities between unrelated classes without forcing a class relationship.
c)Determining an object’s programming interface without revealing the actual body of the class.

29)   What is an abstract class?

Ans: An abstract class is a class designed with implementation gaps for subclasses to fill in and is deliberately incomplete. 

30)   What is the difference between Integer and int?

Ans: a) Integer is a class defined in the java.lang package, whereas int is a primitive data type defined in the Java language itself. Java does not automatically convert from one to the other.
b) Integer can be used as an argument for a method that requires an object, whereas int can be used for
calculations.

31)   What is a cloneable interface and how many methods does it contain?

Ans- It is not having any method because it is a TAGGED or MARKER interface.

32)   What is the difference between abstract class and interface?

Ans: a) All the methods declared inside an interface are abstract whereas abstract class must have at least one abstract method and others may be concrete or abstract.
b) In abstract class, key word abstract must be used for the methods whereas interface we need not use that keyword for the methods.
c) Abstract class must have subclasses whereas interface can’t have subclasses.

33)   Can you have an inner class inside a method and what variables can you access?

Ans: Yes, we can have an inner class inside a method and final variables can be accessed.

34)   What is the difference between String and String Buffer?

Ans: a) String objects are constants and immutable whereasStringBuffer objects are not.
b) String class supports constant strings whereas StringBuffer class supports growable and modifiable strings.

35)   What is the difference between Array and vector?

Ans: Array is a set of related data type and static whereas vector is a growable array of objects and dynamic.

36)   What is the difference between exception and error?

Ans: The exception class defines mild error conditions that your program encounters.Ex: Arithmetic Exception, FilenotFound exception Exceptions can occur when try to open the file, which does not exist
·       the network connection is disrupted
·       operands being manipulated are out of prescribed ranges
·       the class file you are interested in loading is missing
The error class defines serious error conditions that you should not  attempt to recover from. In most cases it is advisable to let the program terminate when such an error is encountered.
Ex: Running out of memory error, Stack overflow error.

37)   What is the difference between process and thread?

Ans: Process is a program in execution whereas thread is a separate path of execution in a program.

38)   What is multithreading and what are the methods for inter-thread communication and what is the class in which these methods are defined?

Ans: Multithreading is the mechanism in which more than one thread run independent of each other within the process.
wait (), notify () and notifyAll() methods can be used for inter-thread communication and these methods are in Object class.
wait( ) : When a thread executes a call to wait( ) method, it surrenders the object lock and enters into a waiting state.
notify( ) or notifyAll( ) : To remove a thread from the waiting state, some other thread must make a call to  notify( ) or notifyAll( ) method on the same object.
39)   What is the class and interface in java to create thread and which is the most advantageous method?
Ans: Thread class and Runnable interface can be used to create threads and using Runnable interface is the most advantageous method to create threads because we need not extend thread class here.

40)   What are the states associated in the thread?

Ans: Thread contains ready, running, waiting and dead states.

41)   What is synchronization?

Ans: Synchronization is the mechanism that ensures that only one thread is accessed the resources at a time.

42)   When you will synchronize a piece of your code?

Ans: When you expect your code will be accessed by different threads and these threads may change a particular data causing data corruption.

43)   What is deadlock?

Ans: When two threads are waiting each other and can’t precede the program is said to be deadlock.

44)   What is daemon thread and which method is used to create the daemon thread?

Ans: Daemon thread is a low priority thread which runs intermittently in the back ground doing the garbage collection operation for the java runtime system. setDaemon method is used to create a daemon thread.

45)   Are there any global variables in Java, which can be accessed by other part of your program?

Ans: No, it is not the main method in which you define variables. Global variables is not possible because concept of encapsulation is eliminated here.
46)What is an applet?
Ans: Applet is a dynamic and interactive program that runs inside a web page displayed by a java capable browser.
47)What is the difference between applications and applets?
Ans: a)Application must be run on local machine whereas applet needs no explicit installation on local machine.
b)Application must be run explicitly within a java-compatible virtual machine whereas applet loads and runs itself automatically in a java-enabled browser.
d)Application starts execution with its main method whereas applet starts execution with its init method.
e)Application can run with or without graphical user interface whereas applet must run within a graphical user interface.
48)How does applet recognize the height and  width?
Ans:Using getParameters()  method.

49)When do you use codebase in applet?
Ans:When the applet class file is not in the same directory, codebase is used.
50)What is the lifecycle of an applet?
Ans:init( ) method        -  Can be called when an applet is first loaded
         start( ) method      -  Can be called each time an applet is started
         paint( ) method     -  Can be called when the applet is minimized or maximized
         stop( ) method      -  Can be used when the browser moves off the applet’s page
destroy( ) method -  Can be called when the browser is finished with the applet
51)How do you set security in applets?
Ans: using  setSecurityManager() method

52)   What is an event and what are the models available for event handling?

Ans: An event is an event object that describes a state of change in a source. In other words, event occurs when an
action is generated, like pressing button, clicking mouse, selecting a list, etc.
There are two types of models for handling events and they are:
a)     event-inheritance model and b) event-delegation model

53)   What are the advantages of the event-delegation  model over the event-inheritance model?

Ans: The event-delegation model has two advantages over the event-inheritance model. They are:
a)It enables event handling by objects other than the ones that generate the events. This allows a clean separation between a component’s design and its use.
b)It performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to be repeatedly process unhandled events as is the case of the event-inheritance.
54)What is source and listener ?
Ans: source : A source is an object that generates an event. This occurs when the internal state of that object changes in some way.
listener : A listener is an object that is notified when an event occurs. It has two major requirements. First, it must have been registered with one or more sources to receive notifications about specific types of events. Second, it must implement methods to receive and process these notifications. 

55)   What is adapter class?

Ans: An adapter class provides an empty implementation of all methods in an event listener interface. Adapter classes are useful when you want to receive and process only some of the events that are handled by a particular event listener interface. You can define a new class to act listener by extending one of the adapter classes and implementing only those events in which you are interested.For example, the MouseMotionAdapter class has two methods, mouseDragged( )and mouseMoved(). The
signatures of these empty are exactly as defined in the  MouseMotionListener interface. If you are interested in only mouse drag events, then you could simply extend MouseMotionAdapter and implement mouseDragged( ) .
56)What is meant by controls and what are different types of controls in AWT?
Ans: Controls are components that allow a user to interact with your application and the AWT supports the following types of controls:Labels, Push Buttons, Check Boxes, Choice Lists, Lists, Scrollbars, Text Components.These controls are subclasses of Component.

57)   What is the difference between choice and list?

Ans: A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices and only one item may be selected from a choice.A List may be displayed in such a way that several list items are visible and it supports the selection of one or more list items.

58)   What is the difference between scrollbar and scrollpane?

Ans: A Scrollbar is a Component, but not a Container whereas Scrollpane is a Conatiner and handles its own events and perform its own scrolling.
59)   What is a layout manager and what are different types of layout managers available in java.awt?
Ans: A layout manager is an object that is used to organize components in a container. The different layouts are available are FlowLayout, BorderLayout, CardLayout, GridLayout and GridBagLayout,Null layout/Custom layout

60)   How are the elements of different layouts organized?

Ans: FlowLayout: The elements of a FlowLayout are organized in a top to bottom, left to right fashion. BorderLayout: The elements of a BorderLayout are organized at the borders (North, South, East and West) and the center of a container.
CardLayout: The elements of a CardLayout are stacked, on top of the other, like a deck of cards.GridLayout: The elements of a GridLayout are of equal size and are laid out using the square of a grid. GridBagLayout: The elements of a GridBagLayout are organized according to a grid. However, the elements are of different size and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.

61)   Which containers use a Border layout as their default layout?      

Ans:  Window, Frame and Dialog classes use a BorderLayout as their layout.

62)   Which containers use a Flow layout as their default layout?

Ans: Panel and Applet classes use the FlowLayout as their default layout.

63)   What are wrapper classes?

Ans: Wrapper classes are classes that allow primitive types to be accessed as objects.

64)   What are Vector, Hashtable, LinkedList and Enumeration?

Ans: Vector : The Vector class provides the capability to implement a growable array of objects.Hashtable : The Hashtable class implements a Hashtable data structure. A Hashtable indexes and stores objects in a dictionary using hash codes as the object’s keys. Hash codes are integer values that identify objects.
LinkedList: Removing or inserting elements in the middle of an array can be done using LinkedList. A
LinkedList stores each object in a separate link whereas an array stores object references in consecutive locations.
Enumeration: An object that implements the Enumeration interface generates a series of elements, one at a time. It has two methods, namely hasMoreElements( ) and nextElement( ). HasMoreElemnts( ) tests if this enumeration has more elements and nextElement method returns successive elements of the series.

65)   What is the difference between set and list?

Ans: Set stores elements in an unordered way but does not contain duplicate elements, whereas list stores elements in an ordered way but may contain duplicate elements.

66)   What is a stream and what are the types of Streams and classes of the Streams?

Ans: A Stream is an abstraction that either produces or consumes information. There are two types of Streams and they are:
Byte Streams: Provide a convenient means for handling input and output of bytes.Character  Streams:  Provide a convenient means for handling input & output of characters.Byte Streams classes: Are defined by using two abstract classes, namely InputStream and OutputStream.Character Streams classes: Are defined by using two abstract classes, namely Reader and Writer.

67)   What is the difference between Reader/Writer and InputStream/Output Stream?

Ans: The Reader/Writer class is character-oriented and the InputStream/OutputStream class is byte-oriented.

68)   What is an I/O filter?

Ans: An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.

69)   What is serialization and deserialization?

Ans: Serialization is the process of writing the state of an object to a byte stream.Deserialization is the process of restoring these objects.

70)   What is JDBC?

Ans: JDBC is a set of Java API for executing SQL statements. This API consists of a set of  classes and interfaces
to enable programs to write pure Java Database applications.
71)   What are drivers available?
Ans:  a)     JDBC-ODBC Bridge driver
       b)      Native API Partly-Java driver
c) JDBC-Net Pure Java driver
d) Native-Protocol Pure Java driver

72)   What is the difference between JDBC and ODBC?

Ans:  a)     ODBC is for Microsoft and JDBC is for Java applications.
b)     ODBC can’t be directly used with Java because it uses a C interface.
c)     ODBC  makes use of pointers which have been removed totally from Java.
d) ODBC mixes simple and advanced features together and has complex options for simple queries. But JDBC is designed to keep things simple while allowing advanced capabilities when required.
e) ODBC requires manual installation of the ODBC driver manager and driver on all client machines. JDBC drivers are written in Java and JDBC code is automatically installable, secure, and portable on all platforms.
f) JDBC API is a natural Java interface and is built on ODBC. JDBC retains some of the basic features of ODBC.

73)   What are the types of JDBC Driver Models and explain them?

Ans: There are two types of  JDBC Driver Models and they are:
a) Two tier model and b) Three tier modelTwo tier model: In this model, Java applications interact directly with the database. A JDBC driver is required to communicate with the particular database management system that is being accessed. SQL statements are sent to the database and the results are given to user. This model is referred to as client/server configuration where user is the client and the machine that has the database is called as the server.
Three tier model: A middle tier is introduced in this model. The functions of this model are:
a) Collection of SQL statements from the client and handing it over to the database,
b) Receiving results from database to the client and
c) Maintaining control over accessing and updating of the above.

74)   What are the steps involved for making a connection with a database or how do you connect to a database?

Ans: a)    Loading the driver : To load the driver, Class.forName( ) method is used.
                     Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
                When the driver is loaded, it registers itself with the java.sql.DriverManager class as an available  database driver.
b) Making a connection with database : To open a connection to a given database, DriverManager.getConnection( ) method is used.
Connection con = DriverManager.getConnection (“jdbc:odbc:somedb”, “user”,  “password”);
c) Executing SQL statements : To execute a SQL query, java.sql.statements class is used.  
createStatement( ) method of Connection to obtain a new Statement object.
Statement stmt  = con.createStatement( );
A query that returns data can be executed using the executeQuery( ) method of  Statement. This method
executes the statement and returns a java.sql.ResultSet that encapsulates the retrieved data:
ResultSet rs = stmt.executeQuery(“SELECT * FROM some table”);
d) Process the results : ResultSet returns one row at a time. Next( ) method of ResultSet  object can be called to move to the next row.  The getString( ) and getObject( ) methods are used for retrieving  column values:
while(rs.next( ) ) {
String event = rs.getString(“event”);
Object count = (Integer) rs.getObject(“count”);

75)   What type of driver did you use in project?

Ans: JDBC-ODBC Bridge driver (is a driver that uses native(C language) libraries and makes calls to an existing
ODBC driver to access a database engine).

76)   What are the types of statements in JDBC?

Ans: Statement                -- To be used createStatement() method for executing single SQL statement
PreparedStatement  -- To be used preparedStatement() method for executing same SQL statement over and
over
CallableStatement    -- To be used prepareCall( ) method for multiple SQL statements over and over

77)   What is stored procedure?

Ans: Stored procedure is a group of SQL statements that forms a logical unit and performs a particular task. Stored Procedures are used to encapsulate a set of operations or queries to execute on database. Stored procedures can be compiled and executed with different parameters and results and may have any combination of input/output parameters.

78)   How to create and call stored procedures?

Ans:   To create stored procedures: Create procedure procedurename (specify in, out and in out parameters)

BEGIN

Any multiple SQL statement;
END;
To call stored procedures:
CallableStatement  csmt  = con.prepareCall(“{call procedure name(?,?)}”);
csmt.registerOutParameter(column no., data type);
csmt.setInt(column no., column name)
csmt.execute( ); 
        

79)   What is servlet?

Ans: Servlets are modules that extend request/response-oriented servers, such as java-enabled web servers.For example, a servlet might be responsible for taking data in an HTML order-entry form and applying the business logic used to update a company’s order database.

80)   What are the classes and  interfaces for servlets?

Ans: There are two packages in servlets and they are javax.servlet and javax.servlet.http.
Javax.servlet contains:
               Interfaces                       Classes
               Servlet                            Generic Servlet
               ServletRequest               ServletInputStream
               ServletResponse             ServletOutputStream
               ServletConfig                 ServletException
               ServletContext                UnavailableException
SingleThreadModel
Javax.servlet.http contains:
               Interfaces                                 Classes
               HttpServletRequest                  Cookie
               HttpServletResponse                HttpServlet
               HttpSession                               HttpSessionBindingEvent
               HttpSessionContext                  HttpUtils
HttpSeesionBindingListener

81)   What is the difference between an applet and a servlet?

Ans: a)     Servlets are to servers what applets are to browsers.
b) Applets must have graphical user interfaces whereas servlets have no graphical user interfaces.

82)   What is the difference between doPost and doGet methods?

Ans: a) doGet() method is used to get information, while doPost( ) method is used for posting information.
b) doGet() requests can’t send large amount of information and is limited to 240-255 characters. However, doPost( )requests passes all of its data, of unlimited length.
c) A doGet( ) request is appended to the request URL in a query string and this allows the exchange is visible to the client, whereas a doPost() request passes directly over the  socket connection as part of its HTTP request body and the exchange are invisible to the client.

83)   What is the life cycle of a servlet?

Ans: Each Servlet has the same life cycle:
a) A server loads and initializes the servlet by init( ) method.
b) The servlet  handles zero or more client’s requests through service( ) method.
c) The server removes the servlet through destroy() method.        

84)   Who is loading the init() method of servlet?

Ans: Web server

85)   What are the different servers available for developing and deploying Servlets?

Ans:  a)    Java Web Server
      b)       JRun
g) Apache Server
h) Netscape Information Server
i)  Web Logic       

86)   How many ways can we track client  and what are they?

Ans: The servlet API provides two ways to track client state and they are:
a)     Using Session tracking and b) Using Cookies.

87)   What is session tracking and how do you track a user session in servlets?

Ans: Session tracking is a mechanism that servlets use to maintain state about a series requests from the same user across some period of time. The methods used for session tracking are:
a) User Authentication - occurs when a web server restricts access to some of its resources to only those clients that log in using a recognized username and password
b) Hidden form fields - fields are added to an HTML form that are not displayed in the client’s browser. When the form containing the fields is submitted, the fields are sent back to the server
c) URL rewriting - every URL that the user clicks on is dynamically modified or rewritten to include extra information. The extra information can be in the form of extra path information, added parameters or some custom, server-specific URL change.
d) Cookies - a bit of information that is sent by a web server to a browser and which can later be read back from that browser.
e) HttpSession- places a limit on the number of sessions that can exist in memory. This limit is set in the session.maxresidents property

88)   What is Server-Side Includes (SSI)?

Ans: Server-Side Includes allows embedding servlets within HTML pages using a special servlet tag. In many servlets that support servlets, a page can be processed by the server to include output from servlets at certain points inside the HTML page. This is accomplished using a special internal SSINCLUDE, which processes the servlet tags. SSINCLUDE servlet will be invoked whenever a file with an. shtml extension is requested. So HTML files that include  server-side includes must be stored with an .shtml extension.

89)   What are cookies and how will you use them?

Ans: Cookies are a mechanism that a servlet uses to have a client hold a small amount of state-information associated with the user.
a)     Create a cookie with the Cookie constructor:
public Cookie(String name, String value)
b) A servlet can send a cookie to the client by passing a Cookie object to the addCookie() method of HttpServletResponse:public void HttpServletResponse.addCookie(Cookie cookie)
c) A servlet retrieves cookies by calling the getCookies() method of HttpServletRequest:
public Cookie[ ] HttpServletRequest.getCookie( ).

90)   Is it possible to communicate from an applet to servlet and how many ways and how?

Ans: Yes, there are three ways to communicate from an applet to servlet and they are:
a) HTTP Communication(Text-based and object-based)
b) Socket Communication
c) RMI Communication
(You can say, by using URL object open the connection to server and get the InputStream from
URLConnection  object).
Steps involved for applet-servlet communication:
1)     Get the server URL.
URL url = new URL();
2)     Connect to the host
URLConnection Con = url.openConnection();
3)     Initialize the connection
Con.setUseCatches(false):
Con.setDoOutput(true);
Con.setDoInput(true);
4)     Data will be written to a byte array buffer so that we can tell the server the length of the data.
ByteArrayOutputStream byteout  = new ByteArrayOutputStream();
5)     Create the OutputStream to be used to write the data to the buffer.
DataOutputStream out = new DataOutputStream(byteout);

91)   What is connection pooling?

Ans: With servlets, opening a database connection is a major bottleneck because we are creating and tearing down a new connection for every page request and the time taken to create connection will be more. Creating a connection pool is an ideal approach for a complicated servlet. With a connection pool, we can duplicate only the resources we need to duplicate rather than the entire servlet. A connection pool can also  intelligently manage the size of the pool and make sure each connection remains valid. A number of connection pool packages are currently available. Some like DbConnectionBroker are freely available from Java Exchange Works by creating an object that dispenses connections and connection Ids on request.The ConnectionPool class maintains a Hastable, using Connection objects as keys and Boolean values as stored values. The Boolean value indicates whether a connection is in use or not. A program calls getConnection( ) method of the ConnectionPool for getting  Connection object it can use; it calls returnConnection( ) to give the connection back to the pool.

92)   Why should we go for interservlet communication?

Ans: Servlets running together in the same server communicate with each other in several ways.The three major reasons to use interservlet communication are:
a) Direct servlet manipulation - allows to gain access to the other currently loaded servlets and perform certain tasks (through the ServletContext object)
b) Servlet reuse - allows the servlet to reuse the public methods of another servlet.
c) Servlet collaboration - requires to communicate with each other by sharing specific information (through method invocation)

93)   Is it possible to call servlet with parameters in the URL?

Ans: Yes. You can call a servlet with parameters in the syntax as (?Param1 = xxx || m2 = yyy).

94)   What is Servlet chaining?

Ans: Servlet chaining is a technique in which two or more servlets can cooperate in servicing a single request.In servlet chaining, one servlet’s output is piped to the next servlet’s input. This process continues until the last servlet is reached. Its output is then sent back to the client.

95)   How do servlets handle multiple simultaneous requests?

Ans: The server has multiple threads that are available to handle requests. When a request comes in, it is assigned to a thread, which calls a service method (for example: doGet(), doPost( ) and service( ) ) of the servlet. For this reason, a single servlet object can have its service methods called by many threads at once.

96)   What is the difference between TCP/IP and UDP?

Ans: TCP/IP is a two-way communication between the client and the server and it is a reliable and there is a confirmation regarding reaching the message to the destination. It is like a phone call. UDP is a one-way communication only between the client and the server and it is not a reliable and there is no confirmation regarding reaching the message to the destination. It is like a postal mail.

97)   What is Inet address?

Ans: Every computer connected to a network has an IP address. An IP address is a number that uniquely identifies each computer on the Net. An IP address is a 32-bit number.

98)   What is Domain Naming Service(DNS)?

Ans: It is very difficult to remember a set of numbers(IP address) to connect to the Internet. The Domain Naming Service(DNS) is used to overcome this problem. It maps one particular IP address to a string of characters.For example, www.mascom.com implies com is the domain name reserved for US commercial sites, moscom is the name of the company and www is the name of the specific computer, which is mascom’s server.

99)   What is URL?

Ans: URL stands for Uniform Resource Locator and it points to resource files on the Internet.URL has four components:
http://www.Pentafour.com:80/index.html http - protocol name, Pentafour - IP address or host name, 80 - port number and index.html - file path.

100) What is RMI and steps involved in developing an RMI object?

Ans: Remote Method Invocation (RMI) allows java object that executes on one machine and to invoke the method
of a Java object to execute on another machine.The steps involved in developing an RMI object are:
a) Define the interfaces
b) Implementing these interfaces
c) Compile the interfaces and their implementations with the java compiler
d) Compile the server implementation with RMI compiler
e) Run the RMI registry
f) Run the application

101) What is RMI architecture?

Ans: - RMI architecture consists of four layers and each layer performs specific functions:
            a) Application layer             ---- contains the actual object definition
            b) Proxy layer                      ---- consists of stub and skeleton
c) Remote Reference layer  ---- gets the stream of bytes from the transport layer and sends it to the                                                                   proxy  layer
d) Transportation layer        ---- responsible for handling the actual machine-to-machine communication

102) what is UnicastRemoteObject?

Ans: All remote objects must extend UnicastRemoteObject, which provides functionality that is needed to make objects available from remote machines.

103) Explain the methods, rebind( ) and lookup() in Naming class?

Ans: rebind( ) of the Naming class(found in java.rmi) is used to update the RMI registry on the server machine.
Naming. rebind(“AddServer”, AddServerImpl); lookup() of the Naming class accepts one argument, the rmi URL and returns a  reference to an object of type AddServerImpl.

104) What is a Java Bean?

Ans: A Java Bean is a software component that has been designed to be reusable in a variety of different environments.  

105) What  is  a Jar file?

Ans: Jar file allows to efficiently deploying a set of classes and their associated resources. The elements in a jar file
are compressed, which makes downloading a Jar file much faster than separately downloading several uncompressed files.
The package java.util.zip contains classes that read and write jar files.

106) What is BDK?

Ans: BDK, Bean Development Kit is a tool that enables to create, configure and connect a set of set of Beans and
it can be used to test Beans without writing a code.

107) What is JSP?

Ans: JSP is a dynamic scripting capability for web pages that allows Java as well as a few special tags to be embedded into a web file (HTML/XML, etc). The suffix traditionally ends with .jsp to indicate to the web server that the file is a JSP files. JSP is a server side technology - you can’t do any client side validation with it.The advantages are:
a) The JSP assists in making the HTML more functional.  Servlets on the other hand allow outputting of
HTML but it is a tedious process.
b) It is easy to make a change and then let the JSP capability of the web server you are using deal with
compiling it into a servlet and running it.

108) What are JSP scripting elements?

Ans: JSP scripting elements lets to insert Java code into the servlet that will be generated from the current JSP page. There are three forms:
a) Expressions of the form <%= expression %> that are evaluated and inserted into the output,
b) Scriptlets of the form <% code %> that are inserted into the servlet’s service method, and
c) Declarations of the form <%! Code %> that are inserted into the body of the servlet class, outside of any existing methods.

109) What are JSP Directives?

Ans: A JSP directive affects the overall structure of the servlet class. It usually has the following form:
<%@ directive attribute=”value” %>
However, you can also combine multiple attribute settings for a single directive, as follows:
<%@ directive  attribute1=”value1”
attribute 2=”value2”
              ...
attributeN =”valueN” %>
There are two main types of directive: page, which lets to do things like import classes, customize the servlet   superclass, and the like; and include, which lets to insert a file into the servlet class at the time the JSP file is translated into a servlet

110) What are Predefined variables or implicit objects?

Ans: To simplify code in JSP expressions and scriptlets, we can use eight automatically defined variables, sometimes called implicit objects. They are request, response, out, session, application, config,pageContext, and page.

111) What are JSP ACTIONS?

Ans: JSP actions use constructs in XML syntax to control the behavior of the servlet engine. You can dynamically insert a file, reuse JavaBeans components, forward the user to another page, or generate HTML for the Java plugin. Available actions include:
?      jsp:include - Include a file at the time the page is requested.
?      jsp:useBean - Find or instantiate a JavaBean.
?      jsp:setProperty  - Set the property of a JavaBean.
?      jsp:getProperty - Insert the property of a JavaBean into the output.
?      jsp:forward - Forward the requester to a newpage.
?      Jsp: plugin - Generate browser-specific code that makes an OBJECT or EMBED

112) How do you pass data (including JavaBeans) to a JSP from a servlet?

Ans: (1) Request Lifetime: Using this technique to pass beans, a request dispatcher (using either “include” or  
forward”) can be called. This bean will disappear after processing this request has been completed.
Servlet:
request.setAttribute(“theBean”, myBean);
RequestDispatcher rd =   getServletContext().getRequestDispatcher(“thepage.jsp”);
rd.forward(request, response);
JSP PAGE:
(2)       Session Lifetime: Using this technique to pass beans that are relevant to a particular session  
(such as in individual user login) over a number of requests. This bean will disappear when the 
session is invalidated or it times out, or when you remove it.
Servlet:
HttpSession session = request.getSession(true);   //Default false
session.putValue(“theBean”, myBean);
/* You can do a request dispatcher here,
or just let the bean be visible on the
next request */
JSP Page:

3) Application Lifetime: Using this technique to pass beans that are relevant to all servlets and JSP pages in a particular app, for all users. For example, I use this to make a JDBC connection pool object available to the various servlets   and JSP pages in my apps. This bean will disappear when the servlet engine is shut down, or when you remove it.
Servlet:
GetServletContext(). setAttribute(“theBean”, myBean);
JSP PAGE:

113) How can I set a cookie in JSP?

Ans: response.setHeader(“Set-Cookie”, “cookie string”);
To give the response-object to a bean, write a method setResponse
(HttpServletResponse response)
·       to the bean, and in jsp-file:
<%
bean.setResponse (response);
%>

114) How can I delete a cookie with JSP?

Ans: Say that I have a cookie called “foo,” that I set a while ago & I want it to go away. I simply:
         <%
Cookie killCookie = new Cookie(“foo”, null);
killCookie.setPath(“/”);
killCookie.setMaxAge(0);
response.addCookie(killCookie);
         %>

115) How are Servlets and JSP Pages related?

Ans: JSP pages are focused around HTML (or XML) with Java codes and JSP tags inside them. When a web server that has JSP support is asked for a JSP page, it checks to see if it has already compiled the page into a servlet. Thus, JSP pages become servlets and are transformed into pure Java and then compiled, loaded into the server and executed.

3
2)What are the design goals of the Enterprise JavaBeansTM architecture?
The Enterprise JavaBeans specification defines a standard architecture for implementing the business logic of multi-tier applications as reusable components
In addition to Enterprise JavaBeans components, the architecture defines three other entities:servers,containers, and clients.
This architecture incorporates several design goals: Enterprise JavaBeans servers are designed to wrap around legacy systems to provide fundamental services for “containers and the components they contain”
Enterprise JavaBeans containers are designed to handle details of “component” life-cycle, transaction, and security management Component developers are free to focus on business logic, since containers provide services automatically by interceding in component method calls. A simple set of callback interfaces are all that a developer needs to implement to participate in container provided services.  A client’s view of an Enterprise JavaBean remains the same regardless of the container it is deployed in. Any container in which an Enterprise JavaBean is deployed presents the same interfaces to the client. This extends to containers from different vendors, running against different servers and different databases, on diverse systems on a network. This client transparency ensures wide scalability for multi-tier applications.

4
1)What is Enterprise JavaBeans?
a)EJB architecture is component architecture for the develeopment and deployment of component-based distributed business applications.EJB the widely adopted serverside component architecture for Java2 platform,Enterprise ediition(J2EE),versatile,reusable and portable across middleware.
2)Is Ejb a product?
a)No, Ejb is a specification,Enterprise JavBeans defines the EJB component architecture and the interfaces between the EJB enabled server and the component.
3)who are ejb product owners?
a)EJB is not a product it is a  specification implemented by Sun with participation from many key vendors in the industry.Vendors like IBM,BEA,Sun and Oracle  etc., are providing products that implement the EJB specification.
4)what are the main features in EJB?
a) EJB architecture is inherently transactional,distributed,portable,multiered and secure.
EJB components are serverside components written entirely in the java.
EJB components contain business logic only no system level programing.
    System level services such as transactions,security,Life cycle,threading,persistence,etc are    automatically managed by the EJB Component by the EJB server.
    EJB architecture is wire-protocol neutral Any protocol can be utilized:HTTP,IIOP,DCOM etc.

5)what is current EJB version?
a)EJB2.0 is currently int he Expert Group phase of the JCP(Java Community process) specification development.
6)what are the key features to be included in EJB 2.0?
a)Integration with JMS.Message Driven bean has been introduced.
b)CMP for Entity bean was replaced with CMR.
c)Integration with Corba Interoperability protocol.

7)What about RMI/IIOP?
a)

8)How Client  contact  the Bean?
a)The Client view is provided through two interface—the home interface and the remote interface.These interfaces
are provided by classes constructed by the container when a bean is deployed, based on information provided by the bean
9)why doesn’t the client interact with an EnterPrise JavaBean directly?
a)To the client. there appears to be direct interaction with an EnterPrise JavaBean through the home and remote interface.The Container interacts between client and component,Completely concealing both bean instance and its own actions from the clients.
10)What methods are developers required to implement the Enterprise JavaBeans  Architecture?
a)There are three categoriesof EJB methods.First, the bean implements methods to those in its home interface containeing methods,second abean implements business logic methods corresponding to those prvided by its remote interface.Finally a bean implements methods for interacting with the container.But these methods are not intended for client access, they are hidden by the container.
11)What are the basic types of Enterprise JavaBeans?
a)There are two types of Enterprise beans- session beans and entity beans represending different types of business logic abstactions.
Sesssion beans represent behaviors associated with client sessions,they are generally implemented to perform a sequence of tasks with in the context of a transaction.A Session bean is a logical extension of the client program, running process on the Clients behalf remotely on the server.
Entity beans reprsent specific  data or collection of data, such as a row
in a relatiopnal database. Entity bean methods provided operations for action on the data represented by the bean.An entity bean is persistent,it servives as long as its data remains in the database.

12)How does a Client find and connect to a specific enterprise bean?
a)A client accesses an  Enterprise JavaBean by looking up the class implemnting its home interface by name through JNDI.It then uses methods of the home interface to acquire access to an instance of the class implementing the remote interface.
13)How does a Client find and connect to a specific enterprise bean write the coding?
a) Context ct=new InitialContext();
HaiHome home=(HaiHome)ct.lookup(“hai”);
HaiRemote remote=home.create();

then remote.Business methods..
14)What general services does a container  provide for an Enterprise JavaBean component?
a) A Container provides Enterprise JavaBeans Components with services of several types First it provides services for lifecycle management and instance pooling/cache Pooling(SFSB), including creation,activation,passvation, and destroy.Secod it interacts methods in a bean to enforce transction and security constraints.It enforce policies and restrictions on bean instances, such as reentrance rules security polices , and some others.

15)What classes and interfaces does a session bean developer define?
a)The Session bean developer defines the home and remote interfce that represent the client views of the bean.Developers also create a class that implements both SessionBean and SessionSynchronization interfaces , as well as methods corresponding to those in the beans home and remote interfaces.
16)what are main interfaces in EJB required ?
a)javax.ejb pacakage contains mainly SessionBean,EntityBean Interfaces
17)What are abstract methods in SessionBean ?
a)
public void setSessionContext(SessionContext ct)
public void ejbActivate()
public void ejbPassivate()
public void ejbRemove()

18)What are the abstract methods in EntityBean ?
a)
public void setEntityContext(EntityContext ct)
public void unSetEntityContext()
public void ejbActivate()
public void ejbPassivate()
public void ejbRemove()
public void ejbLoad()
public void ejbStore()
   
19)What are types in SessionBeans?
a) SessionBeans are mainly  two types Stateless and Stateful

20)what are distinction between a stateless and stateful?
a) Stateless beans are beans that don’t maintain state across method  calls.They are generally intended to perform individual operations  automatically.Any instance of stateless bean can be used by any client at any timeStateful session beans maintain state within and between transactions   Each Stateful session bean is associated with a specific  client.Containers can automatically save and retrieve a beans state in the process of managing instance pools of stateful beans.
21)How do Stateful Session beans maintain consistency across transaction updates?
a) Stateful session beans maintain data consistency by updating their fields each time a transaction is committed.To keep informed of changes in transation status, a stateful session bean implements the SessionSynchronization interface.The Container then calls methods of this interface as it initiates and completes transactions involving the bean.
22)Can’t stateful session beans persistent?
a)Session beans are not designed to be persistent, whether stateful or stateless.A stateful session bean instance typically can’t survive system failures and other destructive events.
23) Is it possible to maintain persistence temporarly in stateful sessiionbeans?
a)yes,it is possible using Handle
24)What Classes and interfaces does an entity bean developer provide?
a) The Entity bean developer defines the home and remote interfaces that represent the cleint view of the bean.Developers also create a class that implements the EntityBean interface, as well as methods corresponding to those in the bean’s home and remote interface.
In addition to defininf create methods in the EJBHome interface,  the entity bean develpoers must also implement finder methods.
25)What are types in EntityBeans?
a) EntityBeans are mainly  two types BeanManaged and ContainerMAnaged
26)what’s a finder method?
a)A finder method provides a way to access an  entity bean by its contents.
  Finder methods are designed to be  introspected and displayed by   devleopment and deployment tools.  The principal finder method that must be implement by all entity  bean is finderByPrimaryKey.In addition to this method the developer must also implement a   primaryKey class to provide each entity bean with a unique,serializable identity.

27)What is the difference between container-managed and beanmanaged persistence?
a)In bean managed persistenece, the bean is entirely responsible for storing and retriving its instance data.The EntityBean interface provides methods for the container to notify an instance when it needs to store or retrieve its data.
  In container managed persistence, entity bean data is automatically maintained by the container using a mechanism of its choosing.

28)How is an entity bean created?
a)An entity bean can be created in two ways: by direct action of the client in which a create method is called on the bean’s home interfce or some other action that adds data to the database that the bean type represents.
29)How does the clent get a reference to an existing entitybean?
a)A client can get a reference to an existiing entity bean in several ways:
   Receiving the bean as paramater in a method call
   Looking the bean uo through a finder method of hte home interface
30) How does a container manages access from multiple transactions on an entiy bean?
a)Container can acquire an exclusive lock on the instances’s sate in the database and serializable acess from multiple transaction to this instance.

31)How do u determine whether two entity beans are the same?
a)By invoking the EntityBen.isIdentical method.This method should be  implemented by the entitybean developer to determine when two reference are to the same object.

32)What are the transaction management benefits of the Enterprise JavaBeans architectur?
a)The Enterprise JavaBeans architecture provides automatic support for distributed transations in component based applications.Such distributed transactions can automatically update data in multiple databases.

33) Does Enterprise JavaBeans allow alternatives to container-manged transactions?
a)In addition to container-managed transactions, an Enterprise JavaBeans can participate in client-managed and bean-manged transactions.

34)What transaction attributes do Enterprise JavaBean containers support?
a) A container supports the following value for the transaction attribute of an Enterprise JavaBean.

TX_NOT_SUPPORTED
TX_BEAN_MANAGED
TX_REQUIRED
TX_SUPPORTS
TX_REQUIRES_NEW  
TX_MANDATORY

35)Explaine the Transaction attributed?
a)A container supports the following value for the transaction attribute of an Enterprise JavaBean.
TX_NOT_SUPPORTED    NOTSUPPORTED
The bean runs outside the context of a transaction.Existing transactions are suspended for the duration of method calls.
TX_BEAN_MANAGED      NEVER
The bean demarks its own transactions boundaries  through the JTA UserTransation interface.
TX_REQUIRED           REQUIRED
Method calls require a transaction context.If one exists ,it will be used;if none exists,one will be created
TX_SUPPORTS            SUPPORTS
Method calls use the current  transaction context if one exists,but don’t create one if none exists.
TX_REQUIRES_NEW     REQUIRESNEW
Continers create new transactions before each method call on the bean, and commit transacions before returing.
TX_MANDATORY
Method calls require a transacion context.If none exists, an exception is thrown.
36)What levels of transaction isolation does the Enterprise JavaBeans specification support?
a)The Enterprise JavaBeans specification defines four supported levels of transaction isolation:
TRANSACION_READ_COMMITED
TRANSACION_READ_UNCOMMITED
TRANSACION_REPETABLE_READ
TRANSACION_READ_SERIALIZABLE

  EJB COMPONENTS DON’T SUPPORT THE JDBC ISOLATION LEVEL   TRANSACTION_NONE 

37)What is the relationship betwen Enterprise Java
Beans component architecture and XML technology?
a)EJB defines a standard for portable business logic and XML technology defines a standard for portable data.

38)How do you configure a session bean for bean-manged transactions?
a) By set transaction-type in the xml file.

39)How do you configure a session bean for bean-manged transactions?
a) By set transaction-attribute in the xml file or int he deployment descriptor.
41)Is is possible for an EJB client to marshall an object of class java.lang.Class to an EJB?
a)Technically yes, spec. compliant NO! “The enterprise bean must not attempt to query a class to

42)Is it possible to write two EJB’s that share the same Remote and Home interfaces, and have different bean classes?
if so, what are the advantages/disadvantages?
a)Sharing interfaces might be possible, but not trivial.
If you deploy with Sun Deployment Tool 1.2.1 you will get a
java.lang.ClassCastException: MyBean2EJB_EJBObjectImpl ...
43)Is it possible to specify multiple JNDI names when deploying an EJB?
a)No. To achieve this you have to deploy your EJB multiple times each specifying a different JNDI name. ..
44)What is the status of the UML-EJB Mapping Specification ?
a)It is currently > in the expert group stage, meaning that the CAll For > Experts (CAFE) was issued and replies were received. ...
45)Is it legal to have static initializer blocks in EJB?
a)Although technically it is legal,static initializer blocks are used to execute some piece of code before executing any constructor or method while instantiating ...
46)In CMP how can I define a finder method equivalent to a ‘SELECT * FROM BANKS ‘
Weblogic 5.1.0 - Define the following Finder syntax in your weblogic-ejb-jar.xml deployment descriptor.
 
 
47)Is it possible to access a CORBA object from a EJB?  a)I am using VisiBroker 4.0 for my CORBA objects and J2EE 1.2.1 for my EJB.  then These properties can be set on the commandline (using -Dorg. or using a file named orb.properties. Java:API:EJB, Java:API:CORBA Robert Castaneda ...

48)How can we interact with COM/DCOM components from a EJB component ?
a)A list of tools that integrate Java with the Microsoft platform is
available here. These tools can be used, as long as they stay within
the EJB specification requirements .

49)Is it possible to stop the execution of a method before completion
in a SessionBean?
a)Threads inside an EJB, One possible solution (that requires coding) would be to setting the transaction 
50)   What is a major difference SessionBean and EntityBean?
a) *SB’s state can be shared by only one client at a time. - persistence storage device is .ser file
*EB’s state can be shared by multiple clients, because as its persistence storage device is DB.
*Used to maintain client’s state persistent in the SB’s instance vars
51)   What is the TX operational  difference SessionBean and EntityBean?

a) SB may or may not be used for TX operational operations,even they are used for TXs bean developer itself responsible to update the bean values into DB.
b)EBs are specially designed for TX operations where bean develope is only responsible for updating bean values,
where the bean values were updated into DB by executing one additional funtion called ejbStore().
52)Who execute TX operation funtion?
a)Container for every regular intervals and  interval time is the refreshMinutes property in JDBC Connection Pool Management.
53)   What is the TX operational  difference SessionBean and EntityBean?
a) SB may or may not be used for TX operational operations,
even they are used for TXs bean developer itself responsible to update the bean values into DB.
b)EBs are specially designed for TX operations
where bean develope is only responsible for updating bean values,
where the bean values were updated into DB by executing one additional funtion called ejbStore().

54)which beans are TX which are not?
a)
*SB are used for TX & Non Tx operations
*EBs are only used for TX operations.

55)what is the Entitybean flow control?
a)
1) Client obtains Home object reference.
2) Client to obtains Remote reference uses h.findByPrimaryKey(Object o)
Note: In place of Object any Object sub class type of reference can be passed as an argument.
3) The request of client received by HomeImpl class findByPrimaryKey(o)

b) It then checks the number of instance created in the container with the max beans in cache value,
if instances are less then container creates one new EJB instance
56)what are the Factors that influences ejbStore()?
a)
1) For every refereshMinutes interval
2) Before ejbPassivate()
3) Before ejbRemove()
57)In EBs the DB state is more consistent than SBs why?
a) by executing ejbLoad() & ejbStore()

58)       In EBs the DB state is more consistent than SBs why?
a) by executing ejbLoad() & ejbStore()

59)       what are the Factors that influences ejbLoad()?
a)
1) next to ejbFindByPrimaryKey()
2) after ejbActivate()
3) There is one property in DD file under called
600
Class c=Class.forName(“qualified classname”);
Object o=c.newInstance();
SBank sb=(simplebank.SBank)o;
sb.setEntitycContext(ec);
sb.ejbFindByPrimaryKey(i);
For the result of above funtion execution if bean doesn’t throws FinderException the container returns Remote object , if Exception found the same exception thrown back to the client.


5
The Industry-Backed Server-Side Component Architecture
Since its introduction over two years ago, Enterprise JavaBeansTM technology has maintained unprecedented momentum among platform providers and enterprise development teams alike. That’s because the EJBTM server-side component model simplifies development of middleware components that are transactional, scalable, and portable. Enterprise JavaBeans servers reduce the complexity of developing middleware by providing automatic support for middleware services such as transactions, security, database connectivity, and more.
As an example, consider transaction management. In the past, developers have had to either write and maintain transaction management code, or rely on third-party transaction management systems, generally provided through proprietary, vendor specific APIs. In contrast, Enterprise JavaBeans technology enables components to participate in transactions—including distributed transactions—simply by specifying which objects and methods are transactional. The EJB server itself handles the underlying transaction management details, so developers can focus specifically on the business purpose of the objects and methods. And because EJB technology is based on the Java programming language, components can be deployed on any platform and operating system that supports the Enterprise JavaBeans standard, and any operting system.
The Enterprise JavaBeans technology model delivers benefits that address the most pressing concerns of enterprise development teams. These include reduced time to market for mission-critical applications, effortless scalability and portability, reduced reliance on hard to find developer skill sets, and an overall increase in developer productivity. EJB technology reduces the cost of developing enterprise scale applications, while protecting an organization’s existing investment in IT resources.

6
1)Who is EJB technology for?

EJB technology benefits a number of audiences:
Enterprise customers that build and/or deploy EJB-based applications - gain development productivity, can choose from a wide selection of EJB servers, create business logic that runs everywhere and is architecture independent, all this while protecting their existing IT investment!
ISVs and SIs that develop EJB components or applications based on EJB components - Invest in business logic that is widely deployable, across any OS and middleware, don’t need to choose one vendor-specific server platform. Like enterprise customers they also benefit from productivity gains and architecture independence
The EJB specification itself is mostly targeted at the EJB server vendors - It is the blueprint that instructs these vendors on how to build an EJB server that EJB components can execute on successfully

2)What are the design goals of the Enterprise JavaBeansTM architecture?
The Enterprise JavaBeans specification defines a standard architecture for implementing the business logic of multi-tier applications as reusable components. In addition to Enterprise JavaBeans components, the architecture defines three other entities: servers, containers, and clients. This architecture incorporates several design goals:

Enterprise JavaBeans servers are designed to wrap around legacy systems to provide fundamental services for containers and the components they contain.
Enterprise JavaBeans containers are designed to handle details of component life-cycle, transaction, and security management. By interceding between clients and components at the method call level, containers can manage transactions that propagate across calls and components, and even across containers running on different servers and different machines. This mechanism simplifies development of both component and clients.
Component developers are free to focus on business logic, since containers provide services automatically by interceding in component method calls. A simple set of callback interfaces are all that a developer needs to implement to participate in container provided services.
A client’s view of an Enterprise JavaBean remains the same regardless of the container it is deployed in. Any container in which an Enterprise JavaBean is deployed presents the same interfaces to the client. This extends to containers from different vendors, running against different servers and different databases, on diverse systems on a network. This client transparency ensures wide scalability for multi-tier applications.
Along with container managed transactions, the Enterprise JavaBeans architecture enables component- and client-managed transactions. Containers can participate in component or client initiated transactions to enforce transaction rules across method call and component boundaries. Components can also specify transaction types by method, enabling them to mix transaction types within a single object.
A variety of Enterprise JavaBean attributes, including the default component transaction type, can be specified at either development or deployment time, and enforced through mechanisms built into the container architecture.
The Enterprise JavaBeans architecture is based on the Java programming language, so enterprise Beans take full advantage of the “write once, run anywhereTM” standard.
3)What’s the client view of an Enterprise JavaBeans component?
The client view is provided through two interfaces—the home interface and the remote interface. These interfaces are provided by classes constructed by the container when a bean is deployed, based on information provided by the bean. The home interface provides methods for creating a bean instance, while the remote interface provides the business logic methods for the component. By implementing these interfaces, the container can intercede in client operations on a bean, and offers the client a simplified view of the component.
4)Why doesn’t the client interact with an Enterprise JavaBean directly?
To the client, there appears to be direct interaction with an Enterprise Java Bean through the home and remote interfaces. However, Enterprise JavaBeans architecture is designed to enable clients and components to exist in different runtimes on different systems on a network. The container intercedes between client and component, completely concealing both the bean instance and its own actions from the clients.
5)What methods are developers required to implement the Enterprise JavaBeans architecture?
There are three categories of Enterprise JavaBeans methods. First, the bean implements methods corresponding to those in its home interface—methods largely for creating, locating and accessing instances of the bean. Second, a bean implements business logic methods corresponding to those provided by its remote interface. Finally, a bean implements methods for interacting with the container. Since these methods aren’t intended for client access, they are hidden by the container.
6)What specific services does a container provide for an entity bean?
As with session beans, the tools for a container generate additional classes for an entity bean at deployment time to implement the home and remote interfaces. These classes enable the container to intercede in all client calls on the same entity bean. The container also generates the serializable Handle class, providing a way to identify the entity bean within a specific life cycle. These classes can be implemented to mix in container-specific code for performing customized operations and functionality. In addition to these custom classes, each container provides a class to provide metadata to the client. Finally, where specified by a particular bean, a container manages persistence of selected fields of the entity bean.
7)What’s the difference between container-managed and bean-managed persistence?
In container-managed persistence, entity bean data is automatically maintained by the container using a mechanism of its choosing. For example, a container implemented on top of an RDBMS may manage persistence by storing each bean’s data as a row in a table. Or, the container may use Java programming language serialization for persistence. When a bean chooses to have its persistence container managed, it specifies which of its fields are to be retained.
In bean-managed persistence, the bean is entirely responsible for storing and retrieving its instance data. The EntityBean interface provides methods for the container to notify an instance when it needs to store or retrieve its data.
8)How is an entity bean created?
An entity bean can be created in two ways: by direct action of the client in which a create method is called on the bean’s home interface, or by some other action that adds data to the database that the bean type represents. In fact, in an environment with legacy data, entity objects may “exist” before an Enterprise JavaBean is even deployed.
9)How does the client get a reference to an existing entity bean?
A client can get a reference to an existing entity bean in several ways:
receiving the bean as a parameter in a method call
looking the bean up through a finder method of the home interface
obtaining the bean as a handle, a runtime specific identifier generated for a bean automatically by the container
10)How do you determine whether two entity beans are the same?
By invoking the EntityBean.isIdentical method. This method should be implemented by the entity bean developer to determine when two references are to the same object. Note that the equals and hashCode methods of Object are undefined for entity beans, since clients don’t directly access bean instances within a container.
11)How does a container manage access from multiple transactions on an entity bean?
Containers manage multiple transactions in one of two ways. First, the container can instantiate multiple instances of the bean and let the transaction management of the DBMS handle transaction processing issues. Or, the container can acquire an exclusive lock on the instance’s state in the database, and serialize access from multiple transactions to this instance.
12)How do enterprise beans handle concurrent and loopback calls on entity beans?
Concurrent calls in the same transaction context on the same Enterprise JavaBean component are illegal and may lead to unpredictable results. A bean can be marked as non-reentrant by its deployment descriptor. This allows the container to detect and prevent illegal concurrent calls from clients. On the other hand, some entity beans may require loopback calls: that is, calls where bean A is invoked, in turn invoking bean B, which then invokes a method call on bean A. This kind of concurrency is tricky and is best avoided.
TRANSACTION SUPPORT
14)What are the transaction management benefits of the Enterprise JavaBeans architecture?
The Enterprise JavaBeans architecture provides automatic support for distributed transactions in component based applications. Such distributed transactions can atomically update data in multiple databases, possibly even distributed across multiple sites. The Enterprise JavaBeans model shifts the complexities of managing these transactions from the application developer to the container provider.
Does Enterprise JavaBeans allow alternatives to container-managed transactions?
In addition to container-managed transactions, an Enterprise JavaBean can participate in client-managed and bean-managed transactions.
15)What transaction attributes do Enterprise JavaBean containers support?
A container supports the following values for the transaction attribute of an Enterprise JavaBean.
Not Supported
The bean runs outside the context of a transaction. Existing transactions are suspended for the duration of method calls.
Required
Method calls require a transaction context. If one exists, it will be used; if none exists, one will be created.
Supports
Method calls use the current transaction context if one exists, but don’t create one if none exists.
Requires New
Containers create new transactions before each method call on the bean, and commit transactions before returning.

Mandatory
Method calls require a transaction context. If none exists, an exception is thrown.
Never
Method calls require that no transaction context be present. If one exists, an exception is thrown.
16)How do bean-managed transactions work?
When a bean with bean managed transactions is invoked, the container suspends any current transaction in the client’s context. In its method implementation, the bean initiates the transaction through the JTA UserTransaction interface. In stateful beans, the container associates the bean instance with the same transaction context across subsequent method calls until the bean explicitly completes the transaction. However, stateless beans aren’t allowed to maintain transaction context across method calls. Each method invocation must complete any transaction it initiates.

ENTERPRISE JAVABEANS AND OTHER TECHNOLOGIES
17)What’s the relationship between Enterprise JavaBeans component architecture and CORBA?
The Enterprise JavaBeans specification is intended to support compliance with the range of CORBA standards, current and proposed.
A Bean’s remote and home interfaces are RMI compliant, and thus can interact with CORBA objects via RMI/IIOP, Sun and IBM’s forthcoming adaptation of RMI that conforms with the CORBA-standard IIOP protocol.
As a companion to the Enterprise JavaBeans specification, Sun Microsystems has defined a standard mapping from Enterprise Java Beans API to CORBA IDL.
JTA, the transaction API prescribed by the Enterprise JavaBeans specification for bean-managed transactions, is designed to layer easily over the OMG OTS transaction standard. 
18)What’s the relationship between Enterprise JavaBeans component architecture and XML technology?
The two technologies are complementary: Enterprise JavaBeans defines a standard for portable business logic and XML technology defines a standard for portable data.
19)What’s the relationship between the Enterprise JavaBeans architecture and JTA?
The Enterprise JavaBeans architecture is intended to conceal transactional complexities from the component developer. Thus, developers and deployers writing to Enterprise JavaBeans architecture don’t need to access transaction management programmatically. However, in the case of bean- or client-managed transactions, the developer can call methods of JTA to initiate and complete transactions. JTA defines the Java programming language interfaces related to transaction management on the Java platform, conformant with the OMG/OTS standard.
The JTA UserTransaction interface is intended to be provided by containers to enable both bean-managed and client-managed transactions.
20)What’s the relationship between Enterprise JavaBeans and JDBC/SQLJ?
An entity bean can implement data persistence in one of two ways: bean-managed or container-managed. In the case of bean-managed persistence, the implementor of an entity bean stores and retrieves the information managed by the bean by means of direct database calls. For these, the bean can use either JDBC or SQLJ. The one tradeoff of this approach is that it makes it harder to adapt bean managed persistence to alternate data sources.
In the case of container-managed persistence, the container provider may implement access to the database using these APIs. The container provider can offer tools to map instance variable of an entity bean to calls to an underlying database. This approach makes it easier to use Beans with different databases.
Session beans also typically access the data they manage using JDBC or JSQL.

NEW FEATURES IN THE ENTERPRISE JAVABEANS 2.0 SPECIFICATION
21)How does the Enterprise JavaBeans 2.0 Specification support messaging?
The EJB 2.0 Specification defines JMS support through a new type of enterprise bean, the message-driven bean. A message-driven bean is invoked by the EJB container as the result of the arrival of a JMS message. To a client, the message-driven bean is a JMS consumer that implements some business logic on the server. Clients communicate with message-driven beans by sending messages to a JMS Destination (either a Queue or a Topic) for which the message-driven bean is a MessageListener.
Message driven beans are distinct from both Entity and Session beans. They have neither home nor remote interfaces. Instead, they implement the javax.jms.MessageListener interface.

22)What new features are provided to support container-managed persistence for Entity beans?
The EJB 2.0 Specification defines a new mechanism for modeling persistent data with Entity beans, and a new query language for Entity beans.
Features to support persistent data models include new abstract classes for both Entity beans and dependent objects. These classes can be implemented to define complex models for persistent data. EJB 2.0 also defines new deployment descriptor elements to define the^Mabstract schema supported by a bean. These allow the bean developer to specify the data model at development time, then allow a container’s deployment tools to automatically^Mgenerate the appropriate helper classes at deployment time. This provides additional platform-independence while supporting a richer representation of the data underlying an Entity bean.
In addition, EJB 2.0 defines the EJB QL, a query language that enables developers^Mto traverse the data model of Entity beans independently of the language used^Mby the underlying database. ^MEJB QL uses the abstract schema of entity beans, their dependent objects, and the^Mrelationships between these objects for its data model. The syntax of EJB QL is similar to that of SQL.
EJB QL enables Bean Providers to write two types of query methods:
Finder methods in the home interface to enable entity bean clients to select specific entity objects.
Select methods which allow a bean internal access to related data without exposing^Mthat data directly to the client.
23)How does EJB 2.0 improve support for interoperability between EJB containers and other J2EE products?
The EJB 2.0 public draft specification includes requirements on EJB container/server providers which enable interoperability for invocations on enterprise beans. These requirements enable communication with J2EE clients including JavaServer Pages, Servlets, Application Clients as well as with enterprise beans in other EJB containers. The goal of these features is to allow enterprise bean invocations to work even when client components and enterprise beans are deployed in J2EE products from different vendors. Support for interoperability between components includes transaction propagation, naming services and security services.
The interoperability mechanisms in EJB 2.0 are based on the IIOP protocol from the Object Management Group. The extensions supporting distributed transaction propagation, security (using SSL) and naming service access are all based on OMG standards. J2EE container products may also use vendor-specific protocols in addition to IIOP.

7

Is is possible for an EJB client to marshall an object of class java.lang.Class to an EJB?
Technically yes, spec. compliant NO! - refer to section 18.1.2 of the EJB 1.1 specification (page 273). “The enterprise bean must not attempt to query a class to ...

Is it possible to write two EJB’s that share the same Remote and Home interfaces, and have different bean classes?
if so, what are the advantages/disadvantages?
Sharing interfaces might be possible, but not trivial.
If you deploy with Sun Deployment Tool 1.2.1 you will get a
java.lang.ClassCastException: MyBean2EJB_EJBObjectImpl ...

Is it possible to specify multiple JNDI names when deploying an EJB?
No. To achieve this you have to deploy your EJB multiple times each
specifying a different JNDI name. Java:API:EJB Andrea Pompili ...

What is the status of the UML-EJB Mapping Specification (JSR 26)?
Thank you for your interest in JSR-000026. It is currently > in the expert group stage, meaning that the CAll For > Experts (CAFE) was issued and replies were received. ...

Is it legal to have static initializer blocks in EJB?
Although technically it is legal, static initializer blocks are used to execute some piece of code before executing any constructor or method while instantiating ...

In CMP how can I define a finder method equivalent
to a ‘SELECT * FROM TABLE’? [RC - Please give reference
to the particular AppServer you are using]
Weblogic 5.1.0 - Define the following Finder syntax in your weblogic-ejb-jar.xml deployment descriptor. All ...

Is it possible to access a CORBA object from a EJB? I am using VisiBroker 4.0 for my CORBA objects and J2EE 1.2.1 for my EJB.
These properties can be set on the commandline (using -Dorg. or using a file named orb.properties. Java:API:EJB, Java:API:CORBA Robert Castaneda ...

How can we interact with COM/DCOM components from a EJB component ?
A list of tools that integrate Java with the Microsoft platform is
available here. These tools can be used, as long as they stay within
the EJB specification requirements ...
Is it possible to stop the execution of a method before completion in a SessionBean?
Threads inside an EJB, refer to section 18.1.2 of the EJB 1.1 specification. One possible solution (that requires coding) would be to set the transaction that the ...

Is it legal to have static initializer blocks in EJB?
Is it legal to have static initializer blocks in EJB? Java:API:EJB ravi srivatsav ...

8
Interview Based Questions
1. What are the types of ServletEngines?
Standalone ServletEngine:A standalone engine is a server that includes built-in support for servlets.
Add-on ServletEngine:Its a plug-in to an existing server.It adds servlet support to a server that was not originally designed with servlets in mind.
Embedded ServletEngine:
2.What is the difference between a Generic Servlet and Http Servlet?
Generic Servlet                                       Http Servlet
Class which internally implements        An abstract class which acts as a child class both for Servlet and ServletConfig      GenericServlet and in addition provides interfaces. some additional methods
like doGet(),doPost(),doDelete() & doPut().

3.What is a Session Id?
It is a unique id assigned by the server to the user when a user first accesses a site or an application ie. when a request is made.
4. List out Differences between CGI Perl and Servlet?

Servlet                                                     CGI

Platform independent                             Platform dependent.
Language dependent                               Language independent.

5. What is Bootstrapping in RMI?

Dynamic loading of stubs and skeletons is known as Boot Strapping.
6. What are different types of Exceptions?.
Runtime exceptions, Errors, Program Exceptions
7. What are types of applets?.
Trusted Applets: Applets with predefined security
Untrusted Applets: Applets without any security

8. When does an Exception occur?.

Whenever an error occurs in an Application,(either at compile time)or runtime,it raises an Exception.
9. What is servlet tunnelling?.
Used in applet to servlet communications, a layer over http is built so as to enable object serialization.
10.       What is a cookie?.

Cookies are a way for a server to send some information to a client to store and for the server to later retrieve its data from that client.Web browser supports 20 cookies/host of 4kb each.
11.What is the frontend in Java?.Also what is Backend?.
Frontend: Applet
Backend : Oracle, Ms-Access(Using JDBC).

12.   Define a JSP?.
Java Server Pages includes scripplets of Servletcode in an Html page.This creates dynamism in the other-wise static HTML.A JSP is a document that describes how to process a request to creeate response.
13.   The length of an identifier is (waiting for reply)
14.   Stored procedures can be called by Callable Statement.
15.   Stack class implements LIFO(Last In First Out).
16.   Servlet Class defines init.
17.   Reference of any instance variable inside a static method is legal if declared static.
18.   What will a read() function do?.
A method in Input Stream.It reads a single byte or an array of bytes.Returns no of bytes read or -1 if EOF(End of file)is reached.
19.To implement a Throwable array,which class is used.
Vector
LinkedList
Stack
ArrayList - Answer(To be Confirmed)

20.   The method for precompiled SQL Statement in JDBC is prepareStatement().
21.   Static binding occurs at
Compile Time
Runtime
Both at compile and runtime.

22.   Virtual Methods are default in
Java
C
C++ - Answer
All

23.   Storage space in java is of the form
Stack
Queue
Heap
List

24.   What is java code embedded in a web page known as
Applets
Servlets
scriptlets
snippets

25.   Which of the following attributes are compulsory with an tag?.  code,height & width.
26.   What does ‘CODEBASE’ in an applet tag specify?.
Files absolute path.
27.   What are AccessSpecifiers & Access Modifiers.
Access Specifiers: Give access previleges to outside applications or users. They are :-
Public: any one can access
private:only class members can access.cannot be inherited.
protected: can be accessed by a derived class.
default: can access data from the current directory.

Access Modifiers: Which gives additional meaning to data, methods and classes.
(i)        Final: cannot be modified at any point of time.

28.   Tools provided by JDK
(i)        javac - compiler
(ii)       java - interpretor
(iii)      jdb - debugger
(iv)      javap - Disassembles
(v)       appletviewer - Applets
(vi)      javadoc - documentation generator
(vii)     javah - ‘C’ header file generator

29.Hostile Applets:Its an applet which when downloaded attempts to exploit your system’s resources in an inappropriate manner.It performs or causes you to perform an action which you would not otherwise care to perform.
30.RemoteObjects: Objects that have methods that can be called accross virtual machines are Remote Objects.An object becomes Remote by implementing Remote Interface.
31.Compiling: Conversion of Programmer-readable Text into Bytecodes,which are platform independent,is known as Compiling.
32.Java Primitive Data Types:
Byte-8-bit
short-16-bit
int-32-bit
Long-64-bit
Float-32-bit floating point
Double-64-bit floating point
Char-16-bit Unicode

33.What is a unicode?Unicode is a standard that supports International Characters.
34. What are blocks?.
They are statements appearing within braces {}.

35. What are types of Java applications?.
(i) Standalone applications(No browser).
(ii) Applets(Browser).

36. What is the method that gets invoked first in a stand alone application?.
The main()method.
37. What is throwing an Exception?.
The act of passing an Exception Object to the runtime system is called Throwing an Exception.
38. What are the packages in JDK?.
There are 8 packages
(i) java.lang(ii)java.util(iii)java.io(iv)java.applet(v) java.awt
(vi) java.awt.image(vii)java.awt.peer(viii)java.awt.net
39. What is a thread?.
Its a single sequential stream of execution.

40. What is runnable?.
Its an Interface through which Java implements Threads.The class can extend from any class but if it implements Runnable,Threads can be used in that particular application.
41. What is preemptive and Non-preemptive Time Scheduling?.
Preemptive: Running tasks are given small portions of time to execute by using time-slicing.
Non-Preemptive: One task doesn’t give another task a chance to run until its finished or has normally yielded its time.
42. What is synchronization?.
Two or more threads trying to access the same method at the same point of time leads to synchronization.If that particular method is declared as synchronized only one thread can access it at a time. Another thread can access it only if the first thread’s task is complete.
43. What are the various thread priorities?.
(i)  Min-Priority-value(1).
(ii) Normal-Priority-value(5).
(iii)Max-Priority-value(10).

44.What is Inter-Thread communication?.
To exchange information between two threads.

45.The package java.applet.* has only one class.
46.BorderLayout is the default layout of Dialog object.
47.executeQuery() returns ResultSet.
48.Throwable class is a sub-class of object and implements Serializable.
49.Super class of TextArea and TextField is TextComponent.
50. Skeletons are server side proxies and stubs are client side proxies.
51. GridBagConstraints class helps in positioning of parameters of a component within an object laidout using GridBagLayout.
52. Netscape introduced JScript language - True
53. EventDelegation model was introduced by JDK 1.1 - False
54. StringTokenizer provides two constructors - False
55. java.applet is one of the smallest package in Java API - True
56. Drag and Drop API consist of java.awt.dnd package - False
57. What is IP?.
IP is Internet Protocol. It is the network protocol which is used to send information from one computer to another over the network over the internet in the form of packets.
58. What is a port?.
A port is an 16-bit address within a computer.Ports for some common Internet Application protocols.
File Transfer Protocol-21.
Telnet Protocol-23.
Simple Mail Transfer Protocol-25.
Hypertext Transfer Protocol-80.

59.What is hypertext?.
Sockets are endpoints of Internet Communication.They are associated with a host address and a port address.Clients create client sockets and connect them to server sockets.
UDP is a connectionless protocol.
MIME(Multipurpose Internet Mail Extension) is a general method by which the content of different types of Internet objects can be identified.
61. What is an abstract class?.
A class which cannot be Instantiated.

62.ServletRunner options are:
·       p-port number(8080).
·       b-backlog connections(50).
·       m-maximum no.of connection handlers(100).
·       t-connection timeout in milliseconds
·       d-servlet directory (current directory)
·       s-servlet properties file

63.How many standard ports are available?.
1024.

64.What is a policy?.
It’s an abstract class for representing the system security policy for a Java application environment(specifying which permissions are available for code from various sources). Java security properties file resides in /lib/security/java.security directory. Value of “policy.provider” should be changed.
65.       What are different ways of Session-Tracking?.
(i)    User-Authorization
(ii)   Hidden Files
(iii)  Persistant Cookies
(iv)  URL Rewriting.

66.       If the browser does not support cookies or if they are disabled, how is session tracking done?.

Session tracking is done by URL Rewriting.
·       Multiple requests can be handled by a servlet and it also can synchronize them.ex: On-line conferencing.
·       Servlets have no Graphic User Interface.
·       We can synchronize the service() method for a major performance impact as multiple requests are involved in case of servlets.
·       We can make a servlet handle a single client/request by implementing single threadmodel interface.

67.       What is a Swing?.
It is a GUI component with a pluggable look and feel.
68.       What is default Look-and-Feel of a Swing Component?.
Java Look-and-Feel.
69.       Awt Components and Swing Components can be inter-mingled in an Application - False
70.       What are the features coming with JFC?.
(i)    Pluggable Look-and-Feel
(ii)   Accessibility API
(iii)  Java 2D/API(JDK 1.2).
(iv)  Drag and Drop Support(JDK 1.2)

71.       What does x mean in javax.swing?.              
Extension of java.
72.       Images can be displayed on Swing Components
·       True
73.       Borders can be changed or added for a LightWeight Components
·       True
74.       Swing Components are always rectangular
·       False
75.       When Swing components overlap with Heavyweight components, it is the latter that is on the top
·       True

76.       What are the components which are termed to be Heavy-weight, available in Light-weight component?.
77.       What are invisible components?.
They are light weight components that perform no painting, but can take space in the GUI.
78.       What is the default layout for a ContentPane in JFC?.
BorderLayout.
79.       What are the borders provided by Swing?.
(i) Simple                (ii) Matte         iii) Titled iv) Compound.
80.       What does Realized mean?.
Realized mean that the component has been painted on screen or that is ready to be painted. Realization can take place by invoking any of these methods.
setVisible(true), show() or pack().
81.       What is a convertor?.
Its an application that converts distance measurements between metric and U.S units.
82. What is the return type of interrupt method?.          void.
83. What is the superclass of exception?.              Throwable.
84.       What is servlet exception?.                    It indicates that there is a problem in the servlet.
85.       What is the difference between a Canvas and a Scroll Pane?.
Canvas                                                            ScrollPane

Its a component                                                      Its a container.

A rectangular area where the application              Implements horizontal and vertical
can draw or trap input events.                                scrolling.

86.       What are the restrictions imposed by a Security Manager on Applets?.

i)  cannot read or write files on the host that’s executing it.
ii) cannot load libraries or define native methods.
iii)   cannot make network connections except to the host that it came from
iv)    cannot start any program on the host that’s executing it.
v) cannot read certain system properties.
vi)    windows that an applet brings up look different than windows that an application brings up.

87. Can we access a database using applets?.                        Yes.
88. What is the default HttpRequest method?.                      doGet().
89.       What is the life cycle of a servlet?.
Removing Handling zero or more client requests.Loading and Initializing.
90.       RPC stands for Remote Procedure Call.
91.       The three layers in RMI are Application Layer,RemoteReferenceLayer and Network Layer.

Directions for questions 1-10: Expand the following terms (HexaWare)
1. ODBC Ans. Open Database Connectivity.
2. HTML Ans. Hyper Text Markup Language
3. RISC   Ans. Reduced Instruction Set Computing
4. ASCII  Ans. American Standard Code For Information Interchange
5.ANSI    Ans. American National Standard Institute.
6. XML   Ans. Extended Markup Language
7. FLOPS Ans. Floating Point Operating Per Second
8. SQL             Ans. Sequential Query Language
9. QBE    Ans. Query By Example
10. ALE  Ans. Address Latch Enable
11. What is lagging in DBMS ?     Ans. Reduced Redundancy.
Directions 12 to 20: For the following questions find the odd man out
12. Unix
OS/2
CMOS
MSDOS       Ans. CMOS
13. Oracle
Informix
Sybase
LISP    Ans. LISP
14. Laser
Inkjet
Dotmatirx
Mouse Ans. Mouse
15. Dir
Cls
Csh
      Copy Ans. Csh
16. Bit
Byte
Nibble
Digit    Ans. Digit
17. Hard Disk
Floppy Drive
CD ROM
Cache  Ans. Cache
18. SQL
QUEL
QBE
ORACLE    Ans. Oracle
19. C++
JAVA
VC++
PASCAL     Ans. PASCAL
20. Projection Operation
Selection Operation
Intersection
Set Difference Operation           Ans. Intersection
21. Which of the following is a universal gate ?
(a) OR
(b) AND
© XOR
(d) NOR  Ans. NOR
22. The default back end of the VB is
(a) Oracle
(b) Sybase
© Informics    Ans. Sybase
23. What is meant by Superconductivity?     Ans. No reistance
24. Viscosity                                   Ans. Friction
25. What is the Lock Based Protocol used for?     Ans. Concurrency Control in DBMS
Directions for question 25 to 32: Convert the decimal numbers on the left to the required form
25. 9’s complement of 28       Ans. 71
26. Binary of 58              Ans. 111010
27. Octal of 359              Ans.547
28. Hexadecimal of 650 Ans.28A
29. BCD of 18                 Ans.0001 1000
30. BCD of 34.8              Ans.0011 0100.1000
31. Excess-3 code of 6    Ans.1001
32. Excess-3 code of 9    Ans.1100
33.  If Ax + By = 1F16; Cx + Dy = 2510 .Find the value of x and y
34. Semaphore is used for
(a) synchronization
(b) dead-lock avoidence
© box
(d) none                                           Ans.  A
35. For addressing 1 MB memory, the  number of address lines required,
(a)11
(b)16
©22
(d) 24                                                      Ans.  b
36. Which of the following remains in memory temporarily
(a) Resident portion of COMMAND.COM
(b) Transient portion of COMMAND.COM
© API
(d) Disk BIOS                                         Ans.  b
37. Pick the odd man out
(a) IO.SYS
(b) MSDOS.SYS
© ROM-BIOS
(d) COMMAND.COM                           Ans.  C
38. OS/2 is a
(a) Single User OS
(b) Multi User OS
© Multi Tasking OS
(d) None of these                                    Ans.  C
39. Bootstrap loader program is a program belonging to
(a) ROM startup software
(b) ROM extension software
© ROM BIOS software
(d) ROM Basic software                         Ans.  A
40. The entry of starting cluster of a file is present in
(a) Boot Parameters
(b) Directory
© FAT
(d) Partition Table and master boot program         Ans.  C

10. In a square, all the mid points are joined. The inner square is shaded.
If the area of the square is A, what is the area of the shaded area?
J2EE JavaLive Chat Transcripts   

Q: What is the JavaTM 2 Platform, Enterprise Edition (J2EE)?
Java 2 Platform, Enterprise Edition (J2EE) is a platform that enables solutions for developing, deploying and managing multi-tier server-centric applications. J2EE utilizes Java 2 Platform, Standard Edition to extend a complete, stable, secure, fast Java platform to the enterprise level. It delivers value to the enterprise by enabling a platform which significantly reduces the cost and complexity of developing multi-tier solutions, resulting in services that can be rapidly deployed and easily enhanced.
Q: What are the main benefits of J2EE?
J2EE provides the following:
A unified platform for building, deploying and managing enterprise-class software without locking users into a vendor specific-architecture and saves IT time.
A platform that will allow enterprise-class application the ability to run anywhere.
A platform with a complete range of readily available enterprise-class services.
A single easy-to-learn blueprint programming model for J2EE.
A platform that is built upon and leverages existing IT investments and guarantees that enterprise-class software will work on multiple platforms.
Q: What technologies are included in J2EE?
The primary technologies in J2EE are: Enterprise JavaBeansTM, JavaServer PagesTM, servlets, the Java Naming and Directory InterfaceTM (JNDI), the Java Transaction API (JTA), CORBA, and the JDBCTM data access API.
Q: How does J2EE relate to Enterprise JavaBeans technology?
Enterprise JavaBeans (EJB) technology is the basis of J2EE. EJB technology provides the scaleable architecture for executing business logic in a distributed computing environment. J2EE makes the life of an enterprise developer easier by combining the EJB component architecture with other enterprise technologies to solutions on the Java platform for seamless development and deployment of server side applications.
Q: Who needs J2EE?
ISVs need J2EE because it gives them a blueprint for providing a complete enterprise computing solution on the Java platform. Enterprise developers need J2EE because writing distributed business applications is hard, and they need a high-productivity solution that allows them to focus only on writing their business logic and having a full range of enterprise-class services to rely on, like transactional distributed objects, message oriented middleware, and naming and directory services.
Q: Will J2EE be available under the community source program?
Yes. When the Java 2 SDK, Enterprise Edition is released, it will be available under Sun’s Community Source Licensing program. For more information on Sun’s community source program see http://www.sun.com/communitysource.
Q: Are there compatibility tests for J2EE?
Yes. A full compatibility test suite will be available when the reference implementation ships. This test suite will test compatibility across Enterprise JavaBeans technology, servlets and JavaServer Pages technology.
Q: What is the J2EETM Blueprints?
The J2EETM Blueprints are the best practices philosophy for the design and building of J2EE-based applications. The design guidelines document provides 2 things. First, it provides the philosophy of building n-tier applications on the Java 2 platform. Second, it provides a set of design patterns for designing these applications, as well as a set of examples or recipes on how to build the applications.
Q: What happened to the J2EE application programming model?
The J2EE application programming model has qualified as part of the Sun BluePrintsTM best practices program, and has been renamed the “J2EETM Blueprints”
Q: What is the purpose of the Reference Implementation?
The purpose of the reference implementation is to validate the specifications. In short, it is to prove that the specifications can be implemented.
Q: Why don‘t you allow the binary reference implementation to be deployed or redistributed?
We do not allow the binary reference implementation to be deployed or redistributed at the request of our partners. The J2EE reference implementation is essentially a full-featured application server. To make it available on the market would provide a product that competes with the companies that we want to adopt the technology. In this light, we set up the licensing terms to honor this request.
Q: Is XML supported in J2EE?
XML is an essential component in the J2EE platform. J2EE will provide a framework for business-to-business data interchange using XML. Currently, JavaServer Pages framework can be used to generate and consume XML between servers or between server and client. In addition, Enterprise JavaBeans component architecture uses XML to describe its deployment properties, giving Enterprise JavaBeans data portability in addition to its code portability. For more info, see http://java.sun.com/xml/.
10
1. What releases of Java technology are currently available? What do they contain?
The Java programming language is currently shipping from Sun Microsystems, Inc. as the Java Development Kit (JDKTM). All Sun releases of the JDK software are available from the JDK software home page (http://java.sun.com/products/jdk/).
Each release of the Java Development Kit (JDK) contains:
·       Java Compiler
·       Java Virtual Machine*
·       Java Class Libraries
·       Java AppletViewer
·       Java Debugger and other tools
·       Documentation (in a separate download bundle)
To run Java 1.0 applets, use Netscape Navigator 3.x or other browsers that support Java applets. To run Java 1.1.x applets, use HotJavaTM 1.x or Netscape Navigator 4.x or other browsers that support the newest version of the Java API.
2. What are the security problems I’ve heard about JavaScript technology scripts?
JavaScript technology is a scripting language used with Netscape Navigator. There have been reports of privacy problems with JavaScript technology, and Netscape is committed to addressing those concerns. JavaScript technology cannot be used to invoke Java applets. The privacy problems reported with JavaScript technology are not present in Java applets.
3. Why developers should not write programs that call ‘sun’ packages
Java Software supports into the future only classes in java.* packages, not sun.* packages. In general, API in sun.* is subject to change at any time without notice. For more details, see the article Why Developers Should Not Write Programs That Call ‘sun’ Packages.
4. Where did the Java name come from? What does it stand for?
The name was chosen during one of several brainstorming sessions held by the Java software team. We were aiming to come up with a name that evoked the essence of the technology—liveliness, animation, speed, interactivity, and more. “Java” was chosen from among many, many suggestions. The name is not an acronym, but rather a reminder of that hot, aromatic stuff that many programmers like to drink lots of.
11
JAVA / J2EE  Questions

(Thanks to Pradeep (srivastava_pradeep@yahoo.com) for his valuable update for our members!)
1. What is Entity Bean and Session Bean ?
2. What are the methods of Entity Bean?
3. How does Stateful Session bean store its state ?
4. Why does Stateless Session bean not store its stateeven though it has ejbActivate and ejbPassivate ?
5. What are the services provided by the container ?
6. Types of transaction ?
7. What is bean managed transaction ?
8. Why does EJB needs two interface( Home and Remote Interface) ?
9. What are transaction attributes ?
10. What is the difference between Container managed persistent bean and Bean managed persistent entity bean ?
11. What is J2EE ?
12. What is JTS ?
13. How many entity beans used and how many tables canu use in EJB
14. project
15. What is scalable,portability in J2EE?
16. What is Connection pooling?Is it advantageous?
17. Method and class used for Connection pooling ?
18. How to deploy in J2EE(i.e Jar,War file) ?
19. How is entity bean created using Container managed entity bean ?
20. Sotware architechture of EJB ?
21. In Entity bean will the create method in EJB home and ejbCreate

22. In Entity bean have the same parameters ?
23. What methods do u use in Servlet – Applet communication ?

24. What are the types of Servlet ?
25. Difference between HttpServlet and GenericServlets ?

26. Difference between doGet and doPost ?
27. What are the methods in HttpServlet?
28. What are the types of SessionTracking?
29. What is Cookie ? Why is Cookie used ?
30. If my browser does not support Cookie,and my server sends a cookie instance What will happen ?
31. Why do u use Session Tracking in HttpServlet ?
32. Can u use __javaScript in Servlets ?
33. What is the capacity the doGet can send to the server ?
34. What are the type of protocols used in HttpServlet?
35. Difference between TCP/IP and IP protocol ?
36. Why do you use UniCastRemoteObject in RMI ?
37. How many interfaces are used in RMI?
38. Can Rmi registry be written in the code, withouthaving to write

39. it in the command prompt and if yes where?
40. Why is Socket used ?
41. What are the types of JDBC drivers ?
42. Explain the third driver(Native protocol driver) ?
43. Which among the four driver is pure Java driver ?
44. What are the Isolation level in JDBC transaction ?
45. How do you connect with the database ?
46. How do you connect without the Class.forName (“ “)?
47. What does Class.forName return ?
48. What are the types of statement ?
49. Why is preparedStatement,CallableStatement used for?

50. In real time project which driver did u use ?
51. Difference between AWT and Swing compenents ?
52. Is there any heavy weight component in Swings ?
53. Can the Swing application if you upload in net, be compatible with your browser?
54. What should you do get your browser compatiblewith swing components?
55. What are the methods in Applet ?
56. When is init(),start() called ?
57. When you navigate from one applet to another what are the methods called?
58. What is the difference between Trusted and Untrusted Applet ?
59. What is Exception ?
60. What are the ways you can handle exception ?
61. When is try,catch block used ?
62. What is finally method in Exceptions ?
63. What are the types of access modifiers ?
64. What is protected and friendly ?
65. What are the other modifiers ?
66. Is synchronised modifier ?
67. What is meant by polymorphism ?
68. What is inheritance ?
69. What is method Overloading ? What is this in OOPS?
70. What is method Overriding ? What is it in OOPS ?
71. Does java support multi dimensional arrays ?
72. Is multiple inheritance used in Java ?
73. How do you send a message to the browser in__JavaScript ?
74. Does __javascript support multidimensional arrays ?
75. Why is XML used mainly?
76. Do use coding for database connectivity in XML?
77. What is DTD ?
79. Is there any tool in java that can create reports?
80. What is meant by Java ?
81. What is meant by a class ?
82. What is meant by a method ?
83. What are the OOPS concepts in Java ?
84. What is meant by encapsulation ? Explain with anexample
85. What is meant by inheritance ? Explain with anexample
 86. What is meant by polymorphism ? Explain with an example
87. Is multiple inheritance allowed in Java ? Why ?
88. What is meant by Java interpreter ?
89. What is meant by JVM ?
90. What is a compilation unit ?
91. What is meant by identifiers ?
92. What are the different types of modifiers ?
93. What are the access modifiers in Java ?
94. What are the primitive data types in Java ?
95. What is meant by a wrapper class ?
96. What is meant by static variable and static method?
97. What is meant by Garbage collection ?
98. What is meant by abstract class
99. What is meant by final class, methods and variables ?
100. What is meant by interface ?
101. What is meant by a resource leak ?
102. What is the difference between interface and abstract class ?
103. What is the difference between public private,protected and static
104. What is meant by method overloading ?
105. What is meant by method overriding ?
106. What is singleton class ?
107. What is the difference between an array and a vector ?
108. What is meant by constructor ?
109. What is meant by casting ?
110. What is the difference between final, finally and finalize ?
111. What is meant by packages ?
112. What are all the packages ?
113. Name 2 calsses you have used ?
114. Name 2 classes that can store arbitrary number of objects ?
115. What is the difference between java.applet.* and java.applet.Applet ?
116. What is a default package ?
117. What is meant by a super class and how can you call a super class ?
118. What is anonymous class ?
119. Name interfaces without a method ?
120. What is the use of an interface ?
121. What is a serializable interface ?
122. How to prevent field from serialization ?
123. What is meant by exception ?
124. How can you avoid the runtime exception ?
125. What is the difference between throw and throws ?
126. What is the use of finally ?
127. Can multiple catch statements be used in exceptions ?
128. Is it possible to write a try within a try statement ?
129. What is the method to find if the object exited or not ?
130. What is meant by a Thread ?
131. What is meant by multi-threading ?
132. What is the 2 way of creating a thread ? Which is the best way and  why?
133. What is the method to find if a thread is active or not ?
134. What are the thread-to-thread communcation ?
135. What is the difference between sleep and suspend ?
136. Can thread become a member of another thread ?
137. What is meant by deadlock ?
138. How can you avoid a deadlock ?
139. What are the three typs of priority ?
140. What is the use of synchronizations ?
141. Garbage collector thread belongs to which priority ?
142. What is meant by time-slicing ?
143. What is the use of ‘this’ ?
144. How can you find the length and capacity of a string buffer ?
145. How to compare two strings ?
146. What are the interfaces defined by Java.lang ?
147. What is the purpose of run-time class and system class
148. What is meant by Stream and Types ?
149. What is the method used to clear the buffer ?
150. What is meant by Stream Tokenizer ?
151. What is serialization and de-serialisation ?
152. What is meant by Applet ?
153. How to find the host from which the Applet has originated ?
154. What is the life cycle of an Applet ?
155. How do you load an HTML page from an Applet ?
156. What is meant by Applet Stub Interface ?
157. What is meant by getCodeBase and getDocumentBase method ?
158. How can you call an applet from a HTML file
159. What is meant by Applet Flickering ?
160. What is the use of parameter tag ?
161. What is audio clip Interface and what are all the methods in it ?
162. What is the difference between getAppletInfo and getParameterInfo ?
163. How to communicate between applet and an applet ?
164. What is meant by event handling ?
165. What are all the listeners in java and explain ?
166. What is meant by an adapter class ?
167. What are the types of mouse event listeners ?
168. What are the types of methods in mouse listeners?
169. What is the difference between panel and frame ?
170. What is the default layout of the panel and frame?
171. What is meant by controls and types ?
172. What is the difference between a scroll bar and ascroll panel.
173. What is the difference between list and choice ?
174. How to place a component on Windows ?
175. What are the different types of Layouts ?
176. What is meant by CardLayout ?
177. What is the difference between GridLayout andGridBagLayout
178. What is the difference between menuitem andcheckboxmenu item.
179. What is meant by vector class, dictionary class ,hash table class,and property class ?
180. Which class has no duplicate elements ?
181. What is resource bundle ?
182. What is an enumeration class ?
183. What is meant by Swing ?
184. What is the difference between AWT and Swing ?
185. What is the difference between an applet and a Japplet
186. What are all the components used in Swing ?
187. What is meant by tab pans ?
188. What is the use of JTree ?
189. How can you add and remove nodes in Jtree.
190. What is the method to expand and collapse nodes in a Jtree ?
191. What is the use of JTable ?
192. What is meant by JFC ?
193. What is the class in Swing to change the appearance of the Frame in Runtime.
194. How to reduce flicking in animation ?
195. What is JDBC ?
196. How do you connect to the database ? What are the steps ?
197. What are the drivers available in JDBC ? Explain
198. How can you load the driver ?
199. What are the different types of statement s ?
200. How can you created JDBC statements ?
201. How will you perform transactions using JDBC ?
202. What are the two drivers for web apllication?
203. What are the different types of 2 tier and 3 tier architecture ?
204. How can you retrieve warning in JDBC ?
205. What is the exception thrown by JDBC ?
206. What is meants by PreparedStatement ?
207. What is difference between PreparedStatement and Statement ?
208. How can you call the stored procedures ?
209. What is meant by a ResultSet ?
210. What is the difference between ExecuteUpdate and ExecuteQuery ?
211. How do you know which driver is connected to a database ?
212. What is DSN and System DSN and differentiate these two ?
213. What is meant by TCP, IP, UDP ?
214. What is the difference between TCP and UDP ?
215. What is a proxy server ?
216. What is meant by URL
217. What is a socket and server sockets ?
218. When MalformedURLException and UnknownHost Exception throws ?
219. What is InetAddress ?
220. What is datagram and datagram packets anddatagram sockets ?
221. Write the range of multicast socket IP address ?
222. What is meant by a servlet ?
223. What are the types of servlets ? Explain
224. What is the different between a Servlet and aCGI.
225. What is the difference between 2 types of Servlets ?
226. What is the type of method for sending request from HTTP server ?
227. What are the exceptions thrown by Servlets ? Why?
229. What is the life cycle of a servlet ?
230. What is meant by cookies ?
231. What is HTTP Session ?
232. What is the difference between GET and POST   methods ?
233. How can you run a Servlet Program ?
234. How to commuincate between an applet and a servlet ?
235. What is a Servlet-to-Servlet communcation ?
236. What is Session Tracking ?
237. What are the security issues in Servlets ?
238. What is HTTP Tunneling
239. How do you load an image in a Servlet ?
240. What is Servlet Chaining ?
241. What is URL Rewriting ?
242. What is context switching ?
243. What is meant by RMI ?
244. Explain RMI Architecture ?
245. What is meant by a stub ?
246. What is meant by a skelotn ?
247. What is meant by serialisation and deserialisation ?
248. What is meant by RRL ?
249. What is the use of TL ?
250. What is RMI Registry ?
251. What is rmic ?
252. How will you pass parameter in RMI ?
253. What exceptions are thrown by RMI ?
254. What are the steps involved in RMI ?
255. What is meant by bind(), rebind(), unbind() and lookup() methods
256. What are the advanatages of RMI ?
257. What is JNI ?
258. What is Remote Interface ?
259. What class is used to create Server side object ?
260. What class is used to bind the server object with RMI Registry ?
261. What is the use of getWriter method ?
262. What is meant by Javabeans ?
263. What is JAR file ?
264. What is meant by manifest files ?
265. What is Introspection ?
266. What are the steps involved to create a bean ?
267. Say any two properties in Beans ?
268. What is persistence ?
269. What is the use of beaninfo ?
270. What are the interfaces you used in Beans ?
271. What are the classes you used in Beans ?
272. What is the diffrence between an Abstract class and Interface ?
273. What is user defined exception ?
274. What do you know about the garbate collector ?
275. What is the difference between C++ & Java ?
276. Explain RMI Architecture?
277. How do you communicate in between Applets &Servlets ?
278. What is the use of Servlets ?
279. What is JDBC? How do you connect to the Database?
280. In an HTML form I have a Button which makes us to open another page in 15 seconds. How will do you that ?
281. What is the difference between Process and Threads ?
282. What is the difference between RMI & Corba ?
283. What are the services in RMI ?
284. How will you initialize an Applet ?
285. What is the order of method invocation in anApplet ?
286. When is update method called ?
287. How will you pass values from HTML page to theServlet ?
288. Have you ever used HashTable and Dictionary ?
289. How will you communicate between two Applets ?
290. What are statements in JAVA ?
291. What is JAR file ?
292. What is JNI ?
293. What is the base class for all swing components ?
294. What is JFC ?
295. What is Difference between AWT and Swing ?
296. Considering notepad/IE or any other thing asprocess, What will Happen if you start notepad or IE 3 times?
297.  Where 3 processes are started or 3 threads arestarted ?
298. How does thread synchronization occurs inside a monitor ?
299. How will you call an Applet using a Java Script function ?
300. Is there any tag in HTML to upload and download files ?
301. Why do you Canvas ?
302. How can you push data from an Applet to Servlet ?
303. What are 4 drivers available in JDBC ?
304. How you can know about drivers and database information ?
305. If you are truncated using JDBC, How can you know ..that how much
Data is truncated ?And What situation , each of the 4 drivers used ?
306. How will you perform transaction using JDBC ?
307. In RMI, server object first loaded into the memory and then the stub
308. Reference is sent to the client ? or whether astub reference is directly sent to the client ?
309. Suppose server object is not loaded into thememory, and the Client request for it , what will happen?
310. What is serialization ?
311. Can you load the server object dynamically? If so, what are the Major 3 steps involved in it ?
312. What is difference RMI registry and OSAgent ?
313. To a server method, the client wants to send a value 20, with this value exceeds to 20,. a message should be sent to the
client ? What will you do for achieving for this ?
314. What are the benefits of Swing over AWT ?
315. Where the CardLayout is used ?
316. What is the Layout for ToolBar ?
317. What is the difference between Grid and GridbagLayout ?
318. How will you add panel to a Frame ?
319. What is the corresponding Layout for Card in Swing ?
320. What is light weight component ?
321. Can you run the product development on all operating systems ?
322. What is the webserver used for running the Servlets ?
323. What is Servlet API used for conneting database ?
324. What is bean ? Where it can be used ?
325. What is difference in between Java Class and Bean?
326. Can we send object using Sockets ?
327. What is the RMI and Socket ?
328. How to communicate 2 threads each other ?
329. What are the files generated after using IDL to Java Compilet ?
330. What is the protocol used by server and client ?
331. Can I modify an object in CORBA ?
332. What is the functionality stubs and skeletons ?
333. What is the mapping mechanism used by Java to identify IDL language ?
334. Diff between Application and Applet ?
335. What is serializable Interface ?
336. What is the difference between CGI and Servlet ?
337. What is the use of Interface ?
338. Why Java is not fully objective oriented ?
339. Why does not support multiple Inheritance ?
340. What it the root class for all Java classes ?
341. What is polymorphism ?
342. Suppose If we have variable ‘ I ‘ in run method,If I can create one or More thread each thread will occupy a separate
copy or same variable will be shared ?
343. In servlets, we are having a web page that isinvoking servlets
344. Username and password ? which is cheks in the database ?

Suppose the second page also If we want to verify the same information whethe it will connect to the database or it will be
used previous information?
345. What are virtual functions ?
349. Write down how will you create a binary Tree ?
350. What are the traverses in Binary Tree ?
351. Write a program for recursive Traverse ?
352. What are session variable in Servlets ?
353. What is client server computing ?
354. What is Constructor and Virtual function? Can we call Virtual Funciton in a constructor ?
355. Why we use OOPS concepts? What is its advantage ?
356. What is the middleware ? What is the functionality of Webserver ?
357. Why Java is not 100 % pure OOPS ? ( EcomServer )
358. When we will use an Interface and Abstract class?
359. What is an RMI?
360. How will you pass parameters in RMI ? Why u serialize?
361. What is the exact difference in between Unicast and Multicast object ? Where we will use ?
362. What is the main functionality of the Remote Reference Layer ?
363. How do you download stubs from a Remote place ?
364. What is the difference in between C++ and Java ?can u explain in detail?
365. I want to store more than 10 objects in a remote server ? Which Methodology will follow ?
366. What is the main functionality of the Prepared Statement ?
367. What is meant by static query and dynamic query ?
368. What are the Normalization Rules ? Define theNormalization ?
369. What is meant by Servelet? What are theparameters of the service Method ?
370. What is meant by Session ? Tell me something about HTTPSession Class ?
381. How do you invoke a Servelt? What is the difference in between DoPost and doGet methods ?
382. What is the difference in between the HTTPServlet and Generic Servlet?
383. Expalin their methods ? Tell me their parameter names also ?
384. Have you used threads in Servelet ?
385. Write a program on RMI and JDBC using StoredProcedure ?
386. How do you sing an Applet ?
387. In a Container there are 5 components. I want to display the all The components names, how will you do that one ?
388. Why there are some null interface in java ? Whatdoes it mean ?
389. Give me some null interfaces in JAVA ?
390. Tell me the latest versions in JAVA related areas?
391. What is meant by class loader ? How many typesare there? When will we use them ?
392. How do you load an Image in a Servlet ?
393. What is meant by flickering ?
394. What is meant by distributed Application ? Why we are using that in our applications ?
395. What is the functionality of the stub ?
396. Have you used any version control ?
397. What is the latest version of JDBC ? What are thenew features are added in that ?
398. Explain 2 tier and 3 -tier Architecture ?
399. What is the role of the webserver ?
400. How have you done validation of the fileds in your project ?
401. What is the main difficulties that you are faced in your project ?
402. What is meant by cookies ? Explain ?
403. Problem faced in your earlier project
404. How OOPS concept is achieved in Java
405. Features for using Java
406. How does Java 2.0 differ from Java 1.0
407. Public static void main - Explain
408. What are command line arguments
409. Explain about the three-tier model
410. Difference between String & StringBuffer
411. Wrapper class. Is String a Wrapper Class
412. What are the restriction for static method
413. Purpose of the file class
414. Default modifier in Interface
415. Difference between Interface & Abstract class
416. Can abstract be declared as Final
417. Can we declare variables inside a method as Final Variables
418. What is the package concept and use of package
419. How can a dead thread be started
420. Difference between Applet & Application
421. Life cycle of the Applet
422. Can Applet have constructors
423. Differeence between canvas class & graphics class
424. Explain about Superclass & subclass
425. Difference between TCP & UDP
426. What is AppletStub
427. Explain Stream Tokenizer
428. What is the difference between two types of threads
429. Checked & Unchecked exception
430. Use of throws exception
431. What is finally in exception handling
432. Vector class
433. What will happen to the Exception object afterexception handling two types of multi-tasking two ways to create the
thread Synchronization I/O Filter
434. How can you retrieve warnings in JDBC
435. Can applet in different page communicate with each other
436. Four driver Manager
437. Features of JDBC 20
438. Explain about stored procedures
439. Servlet Life cycle
440. Why do you go for servlet rather than CGI
441. How to generate skeleton & Stub classes
442. Explain lazy activation
443. Firewalls in RMI

12
JAVA
1. What  are  concepts  of  OOPS  and  how  are  they  implemented  in  Java?
2. What  is  dynamic  binding?
3. How  to  implement  RMI  in  Java?
4. What  is  Object  Serialization  and  how  it  can  be  used?
5. What  are  the  common  problems  you  have  faced  while  implementing  Java?
6. How  can  you  debug  the  Java  code?
7. How  can  you  cast  objects?  When  you  call a  method  while  casting  to  the
parent,  which  method  will  be  called.
8. How  can  you  call  parent  methods?
9. How  swing  components  are  different  from  AWT?  How  can  you  draw  usingSwing  components?
10. What  is  1.1 AWT  event  handling?  How  can  a  listener  identify  that  the  event  came  from  a  particular  object?
11. What  is  finalize  method?  When  is  it  called?
12. When  you  are  opening  the  file,  what  are  the  exceptions  that  are  to  be  caught?
13. In  socket  programming  how  does  server  know  that  a  client  is  connected  to  it?
14. Can  you  declare  a  static  variable  in  a  method?
15. What  is  thread  deadlock?  How  do  you  resolve  it?
16. How  can  you  take  string  into  InputStream?
17. How  can  you  print  nodes  of  a  Binary  tree?
18. How  can  you  eliminate  duplicates  from  an  array?
19. How  can  you  reverse  a  string?
20. What  are  interfaces?
21. What  are  inner  classes?  Can  you  call  a  private  data  from  an  inner  class?
22. If  you  do  not  want  to  implement  all  the  methods  in  an  interface,  what  will you  do?
23. How  can  you  implement  a  multithreaded  applet?
24. How  can  you  connect  to  a  remote  database  using  Applet?  (on  servlets)
25. How  can  you  convert  a  string  to  long?
26. What  is  finally  keyword?
27. What  are  abstract  classes?
28. As  a  developer  what  care  do  you  take  to  improve  the  performance?
29. What  are  hot spots  in  Java  programming?
30. JDBC
31. What  are  the  runtime  exceptions  in  Java  that  you  get  frequently?
32. Can  you  have  a  constructor  in  abstract  class?
33. Can  you  call  a  constructor  within  a  constructor?
34. How  do  you  compare  two  strings?
35. Can  you  extend  more  than  one  interface?
36. What  are  the  common  JDBC  problems  that  you  have  got?
37. What  drivers  have  you  used?
38. How  can  you  get  all  the  data  from  a  table  into  a  buffer?
39. What  are  different  ways  to  register  a  driver?
40. Socket  programming
41. Multiple  server
42. Event  handling  in  AWT 1.1
43. Inner  classes
44. Gridbag Layout
45. What  are  the  debugging  tools  you  used?
46. How  can  you  sort  dates?
47. How  can  you  insert  data  into  long  row  column  of  database?
48. What  is  the  difference  between  database  null  and  Java  null?


SQL
1. Write  a  query  to  list  Ename  and  MgrName  from  EMP  table.
2. Can  you  define  foreign  key  with  a  key  from  the  same  table?
3. Is  it  recommended  to  define  indexes  on  a  foreign  key?
4. When  do  you  create  an  index?
5. Write  a  query  to  find  out  top  two  salary  holders.
6. Top  two  salary  holders  in  each  department
7. What  is  an  outer  join?
8. What  is  correlated  subquery?
9. What  is  the  difference  between  Union,  Unionall,  Minus,  and  Intersect?
10. How  primary  key  is  implemented  in  Oracle?
11. ER  diagrams?
12. What  is  denormalization?
13. What  are  different  triggers  and  procedures  of   ?
14. What  is  procedure  overloading?
15. What  are  restrictions  on  triggers?
16. What  is  table  mutation?  How  do  you  avoid  it?
17. What  are  cursor  attributes?
18. How  can  you  find  out  whether  a  row  is  updated  or  not?
19. How  do  you  debug  PL/SQL  code?
20. Exception  handling  in  PL/SQL
21. PL/SQL  tables  and  records.
22. Global  variables  in  packages.
23. Master  detail  relationship.
24. How  can  you  tune  SQL  statements?
25. What  is  the  restriction  on  varchar  variable  on  procedure?
26. What  are  restrictions  on  long  row?
27. How  can  you  eliminate  duplicates?
28. Can  you  create  an  index  on  sex  column  where  there  is  M or F?
29. Normalization
30. How  can  you  determine  SGA  site?

13
JAVA and EJB - INTERVIEW QUESTIONS

1.What is Entity Bean and Session Bean ?
2.What are the methods of Entity Bean?
3.How does Stateful Session bean store its state ?
4.Why does Stateless Session bean not store its state even though it has ejbActivate and ejbPassivate ?
5.What are the services provided by the container ?
6.Types of transaction ?
7.What is bean managed transaction ?
8.Why does EJB needs two interface( Home and Remote Interface) ?
9.What are transaction attributes ?
10.What is the difference between Container managed persistent bean and Bean managed persistent entity bean ?
11.What is J2EE ?
12.What is JTS ?
13.How many entity beans used and how many tables can u use in EJB project ?
14.What is scalable,portability in J2EE?
15.What is Connection pooling?Is it advantageous?
16.Method and class used for Connection pooling ?
17.How to deploy in J2EE(i.e Jar,War file) ?
18.How is entity bean created using Container managed entity bean ?
Sotware architechture of EJB ?
19.In Entity bean will the create method in EJB home and ejbCreate in Entity bean have the same parameters ?
20.What methods do u use in Servlet – Applet communication ?
21.What are the types of Servlet ?
22.Difference between HttpServlet and Generic Servlets ?
23.Difference between doGet and doPost ?
24.What are the methods in HttpServlet?
25.What are the types of SessionTracking?
26.What is Cookie ? Why is Cookie used ?
27.If my browser does not support Cookie,and my server sends a cookie instance What will happen ?
28.Why do u use Session Tracking in HttpServlet ?
29.Can u use javaScript in Servlets ?
30.What is the capacity the doGet can send to the server ?
31.What are the type of protocols used in HttpServlet ?
32.Difference between TCP/IP and IP protocol ?
33.Why do you use UniCastRemoteObject in RMI ?
34.How many interfaces are used in RMI?
35.Can Rmi registry be written in the code, without having to write it in the command prompt and if yes where?
36.Why is Socket used ?
37.What are the types of JDBC drivers ?
38.Explain the third driver(Native protocol driver) ?
39.Which among the four driver is pure Java driver ?
40.What are the Isolation level in JDBC transaction ?
41.How do you connect with the database ?
42.How do you connect without the Class.forName (“ “) ?
43.What does Class.forName return ?
44.What are the types of statement ?
45.Why is preparedStatement,CallableStatement used for?
46.In real time project which driver did u use ?
47.Difference between AWT and Swing compenents ?
48.Is there any heavy weight component in Swings ?
49.Can the Swing application if you upload in net, be compatible with your browser?
50.What should you do get your browser compatible with swing components?
51.What are the methods in Applet ?

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