How to make abstract class in Java?

Asked By Ramiz Raja 0 points N/A Posted on - 08/08/2011

In C++ we can make an abstract class by making all the methods pure virtual so that its object can not be instantiated.

How can we make a Java class abstract so that its object can not be instantiated?

Please tell me the easiest way to do it. 

 

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Answered By cesear 0 points N/A #110783

How to make abstract class in Java?

Hi,

it's very easy  I'll show you two examples you will understand :

Eg1 :

we have this class

abstract public class FormeGeometric1{

double posX,posY ;

void deplacer(double x ,double Y) {

posX=x;

posY=Y;

}

void afficherPosition () {

System.out.println ("position : ("+posX+","+posY+")");

}

abstract double surface ()

abstract double perimeter

}

This class is Abstract because the two methods surface and perimeter are abstract

this class is no instantiated

Eg2 :

we have this class :

public class Cercel7 extends FormeGeometric1 {

double r;

Cercel7(Double x , double y , double ray) {

posX=x;

posY=y;

r=ray;

}

double surface () {

return Math.PI*Math.pow(rayon,2.);

}

double perimeter () {

return 2*r*Math.PI

}}

an Abstract class allow us to define the shared characteristics of different  object classes

Here is a joined picture it will clear the vision

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Answered By lakshmi 0 points N/A #110784

How to make abstract class in Java?

The Easiest way to do it is

let us take  a simple abstract class

 

public abstract class Abstract

{

//default constructor

public Abstract

{

System.out.println("Abstract Object is Created");

}//end of constructor

}//end of class

 

Now let us Take Main class

public class AbstractDemo

{

public static void main(String args[])

{

//Creating the Object to Abstract class

Abstract abs=new Abstract();

System.out.println("In the Main method");

}//end of main method

}//end of class

compile

javac Abstract.java

it will compile successfully

then 

javac AbstractDemo.java

Then you will get an error 

similar to this like, cannot instantiate abstract class

this is because we declared class as Abstract

then try the same example by removing the abstract in Abstract class then u will find the difference

 

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• Posted on - 09/12/2011
• Question Category: Java