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 Q791. What will be the output of following code ?

Base Interface

public interface BaseInterface {
   int i = 4;
}

Derived Interfaces

public interface DerivedInterface1 extends BaseInterface{
   int i = 5;
}

public interface DerivedInterface2 extends BaseInterface{
   int i=6;
}

Implementing Class

public class Class implements DerivedInterface1,DerivedInterface2 {
int i=10;   

public static void main(String[] args){
      System.out.println(new Class().i);
   }
}

What will be the output upon executing main and Why ?		Core Java
Ans. 10

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   Like         Discuss         Correct / Improve     interfaces  coding  code      intermediate

 Q792. What will be the output of following code ?

Base Interface

public interface BaseInterface {
   int i = 4;
}

Derived Interfaces

public interface DerivedInterface1 extends BaseInterface{
   int i = 5;
}

public interface DerivedInterface2 extends BaseInterface{
   int i=6;
}

Implementing Class

public class Class implements DerivedInterface1,DerivedInterface2 {
   public static void main(String[] args){
      System.out.println(BaseInterface.i);
   }
}

What will be the output upon executing main and Why ?		Core Java
Ans. It will print 4 because member elements of an interface are implicitly static and hence the concept of overriding doesn't work.


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   Like         Discuss         Correct / Improve     interfaces  coding  code  extending interfaces  diamond interfaces     Asked in 1 Companies      intermediate

 Q793. How and Why Strings are interned in Java ?Core Java
Ans. String class has a public method intern() that returns a canonical representation for the string object. String class privately maintains a pool of strings, where String literals are automatically interned.

these are automatically interned so as to have efficient String comparison using == operator instead of equals which is usually slower.

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   Like         Discuss         Correct / Improve     string  string pool  string intern     Asked in 1 Companies

 Q794. What are callback methods ?Core Java
Ans. Component methods called by the container to notify the component of the events

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   Like         Discuss         Correct / Improve          Asked in 1 Companies

 Q795. What is an applet ?Core Java
Ans. Applet is a J2EE component or a tiny application that gets executed in a widget engine ( like browser )

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   Like         Discuss         Correct / Improve     applet

 Q796. What does the Web module contains ?Java EE
Ans. JSP files, media files and deployment descriptor ( web.xml )

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   Like         Discuss         Correct / Improve     j2ee  j2ee web module

 Q797. What are the different J2EE modules ?Java EE
Ans. 1. Application Client Module
2. Web Module
3. EJB
4. Resource Adapter

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   Like         Discuss         Correct / Improve     j2ee  j2ee modules

 Q798. What is the difference between

File f = new File("homexyz.txt");

and

File f = File.createTempFile("xyz",".txt","home"); ?		Core Java
Ans. First will not create physical file in storage whereas the second will.

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   Like         Discuss         Correct / Improve     file handling  File.createTempFile  file handling      intermediate        rare

 Q799. What are the benefits of creating immutable objects ?Core Java
Ans. 1. Security and Safety - They can be shared across multiple threads as they are thread safe. Moreover, it protects then from bad state due to interception by the other code segment. One such problem due to mutability and access by alternate code segment could be the change of hash code and then the impact on its search with hash collections.

2. Reuse - In some cases they can be reused as only one copy would exist and hence it can be relied upon. For example - String Pool

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   Like         Discuss         Correct / Improve     immutable  immutability objects     Asked in 1 Companies      Intermediate        frequent

Usually asked to entry level software developers.
  Q800. Write a program to swap two variables without using thirdCore Java
Ans. public static void main(String[] args) {
   int num1 = 1;   
   int num2 = 2;
   num1 = num1^num2;
   num2 = num1^num2;
   num1 = num1^num2;
   System.out.print("num1 = " + num1 +", num2 = "+num2);
}

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   Like         Discuss         Correct / Improve     code  coding     Asked in 37 Companies      basic        frequent

 Q801. What is memory leak ? How Java helps countering memory leaks compared to C++ ?Core Java
Ans. Memory Leak is a situation wherein we have a reserved memory location but the program has lost its reference and hence has no way to access it.

Java doesn't have concept of Pointers, Moreover Java has concept of Garbage collection that frees up space in heap that has lost its references.

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   Like         Discuss         Correct / Improve     memory leak  garbage collection      intermediate        frequent

 Q802. Can we override wait() or notify() methods?Core Java
Ans. wait and notify are declared final in object class and hence cannot be overridden.

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   Like         Discuss         Correct / Improve     object class methods  wait  notify

 Q803. Can we have only try block in java ?Core Java
Ans. No, It should be followed by either catch or finally.

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   Like         Discuss         Correct / Improve     try  exception handling

 Q804. Does Java supports Default arguments ?Core Java
Ans. No

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 Q805. Explain dot(.) operator ?Core Java
Ans. Its used to access the object properties using the object reference or class properties using the Class Name. Moreover its used to access the classes and Interfaces of a package.

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   Like         Discuss         Correct / Improve     operators

 Q806. What is a class and object ?

or

How would you explain a fresher the concept of class and object in simple terms ?		Core Java
Ans. Class is a template using which objects are created in memory. It's kind of a mold using which objects with body / state are made.


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   Like         Discuss         Correct / Improve     class  object  class vs object     Asked in 4 Companies      basic        frequent

 Q807. Have you heard of SiteMesh ?Java EE
Ans. Sitemesh is a web page layout and decoration framework by OpenSymphony. SiteMeshFilter can intercept the requests and then build UI components (based on configuration) then renders the final page.

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   Like         Discuss         Correct / Improve     sitemesh

 Q808. What is the difference between filter and filter-mappings xml tag within deployment descriptor ?Java EE
Ans. filter tag speficies the filter name and respective class for handling filter action whereas filter mapping maps the filter to the url patterns ( specifying the url that needs to be intercepted )

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   Like         Discuss         Correct / Improve     deployment descriptor  web.xml  filters  filter mapping

 Q809. What is a Servlet Filter ?Java EE
Ans. It's an object that can intercept http request and response and hence we can take appropriate action on those requests.

There are different types of filters based on Specifications like

Authentication
Logging
Encryption
Tokenizing

etc

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   Like         Discuss         Correct / Improve     servlets  servlet filters     Asked in 3 Companies      basic        frequent

 Q810. Do you feel that its useless to define hashCode method for a class ?Core Java
Ans. Yes its useless if we are not going to use its objects within Hash collection, For example - HashSet , HashMap. HashCode is used internally by these collections for Search.

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   Like         Discuss         Correct / Improve     hashcode  hash collections  search

 Q811. How can be restrict creation of more than n objects in Java ?Core Java
Ans. We can follow the same design which we follow in singleton Classes. We can have a static counter that will keep the count of number of objects already created, We can keep the constructor private and being called through the static method. We can keep incrementing the counter before calling the constructor and put a check to call only if it's lesser than n.

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 Q812. What are the cursors available in Java ?Core Java
Ans. Enumeration
Iterator
List iterator

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   Like         Discuss         Correct / Improve     cursors  iterator

 Q813. Which memory segment holds String Pool in Java ?Core Java
Ans. String Pool resides in runtime constant Pool which is a part of Heap memory segment.

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   Like         Discuss         Correct / Improve     string pool  memory management      Expert        rare

 Q814. how to access the methods of an inner class?Core Java
Ans. It depends on the type of inner class

To access non static inner class method

new OuterClass().new InnerClass().getMethod();

To access static method of static inner class

new OuterClass.InnerClass().getMethod();

  Sample Code for inner class

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   Like         Discuss         Correct / Improve     inner classes  nested aclasses     Asked in 1 Companies      Intermediate        frequent

 Q815. What is Shutdown hook ?Core Java
Ans. Shutdown hook is a thread that is invoked before the JVM is shut down. we can use it perform resource cleaning task.

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 Q816. Difference between shallow copy and object cloning ?Core Java
Ans. Shallow copy is one of the way for object cloning, other being deep copy.

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   Like         Discuss         Correct / Improve     cloning  shallow copy  object cloning      basic

 Q817. Can we convert a numeric IP address to a web host name ?Java EE
Ans. Yes, using InetAddress.getByName("<IP Address>").getHostName();

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   Like         Discuss         Correct / Improve     ip address to hostname  INETAddress      intermediate

 Q818. What is an IO Filter ?Core Java
Ans. It's an object that reads from one stream and writes to another.

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   Like         Discuss         Correct / Improve     java io  io filter      intermediate

 Q819. What is the difference between the Reader/Writer java.io hierarchy and the Stream class hierarchy?Core Java
Ans. The Reader/Writer hierarchy is character oriented, whereas the Stream class hierarchy is byte oriented.

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   Like         Discuss         Correct / Improve     java io  streams      intermediate

 Q820. What kind of thread is garbage collection thread ?Core Java
Ans. Daemon thread

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   Like         Discuss         Correct / Improve     garbage collection      intermediate
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