13.a. create an abstract class Shape

a) Write a java program to create an abstract class named Shape that contains an empty method named numberOfSides ( ).Provide three classes named Trapezoid, Triangle and Hexagon such that each one of the classes extends the class Shape. Each one of the classes contains only the method numberOfSides ( ) that shows the number of sides in the given geometrical figures.

import javax.swing.*;

abstract class Shape

{

public abstract void numberOfSides();

}

class Trapezoid extends Shape

{

public void numberOfSides()

{

JOptionPane.showMessageDialog(null,"TRAPEZOID -- Number of sides in trapezoid is 4 (Of which two

are parallel and with no angles)");

}

}

class Triangle extends Shape

{

public void numberOfSides()

{

JOptionPane.showMessageDialog(null,"TRIANGLE -- Number of sides in Triangle is 3 ");

}

}

class Hexagon extends Shape

{

public void numberOfSides()

{

JOptionPane.showMessageDialog(null,"HEXAGON -- Number of sides in Hexagon is 6 ");

}

}

class ShapeDemo

{

public static void main(String[] args)

{

JOptionPane.showMessageDialog(null,"Some of the Geometrical figures are as follows " );

Trapezoid t=new Trapezoid();

Triangle tg=new Triangle();

Hexagon h=new Hexagon();

t.numberOfSides();

tg.numberOfSides();

h.numberOfSides();

}

}