Java Interview Questions

Example:

import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;

public class SetExample {

    public static void main(String[] args) {

        // Set example with implement TreeSet
        Set<String> s=new TreeSet<String>();

        s.add("b");
        s.add("a");
        s.add("b");

        Iterator it=s.iterator();

        while(it.hasNext())
        {
          String value=(String)it.next();

          System.out.println("Value :"+value);
        }
    }
}

Output

Set Value :a
Set Value :b

set ignore the duplicate value.

Monday, 29 August 2011

what is an interface? java interview questions ...

Ans:

An interface is a named collection of method declarations and constant declarations.

here we only declare the methods not a implementation.

it's implemented by a class using implements keyword.

syntax:

        interface interface name{

           //declaration of methods and constants

         }

        class class name implements{



            //implementation codes

        }

what is inheritance? java interview questions ...

Ans:

Java Inheritance defines an is-a relationship between a superclass and its subclasses.

The child class can use the methods and variables of the superclass and add to them its own methods and variables .

The keyword extends is used by the sub class to inherit the features of super class .

Using inheritance we can achieve the concepts of reusability.

syntax:

             class A{

              //class A codes

            }

             class B{

             //class B codes and also use class A members

             }

what is encapsulation? java interview questions ...

Ans:

java encapsulation is wrapping up of the data into single unit.

The process of hiding all the details of an object that do not contribute to its essential characteristics

for example if we declare the members(variable or method) public then we access the members into anywhere, but if we declare the private then we cant access the members out of class this is called encapsulation.

what is abstraction? java interview questions ...

Ans:

Java Abstraction means to show only the necessary details to the client of the object .

without knowing the background of details we use.

it is usually accomplished through the use of base classes with virtual functions , each derived function provides the details that implement the behavior behind that abstraction

what is an object? java interview questions ...

Ans:

Object is a run time entity.

A set of data combined with methods for manipulating

that data.

Three properties characterize objects:

Identity
State
Behavior

Syntax:

     ClassName object ;

                  (or)

     ClassName object = new ClassName;

what is java? (or) define java? java interview questions ...

Ans:

java is a high level programming language developed by James Gosling for Sun Microsystems.

java was originally called OAK ,later the name changed.

java is a neutral platform language(support all platform).

java is a Object Oriented Programming language.

java mainly developed by mobile device and internet.

Advantages:

Easy to Use

Reliability

Secure

Platform Independent