//Point.java
  // Definition of class Point
  public class Point {
     protected int x, y; // coordinates of the Point
    
     public Point() {setPoint( 0, 0 ); } // no-argument constructor
    
     public Point( int a, int b ) { setPoint( a, b ); } // constructor
    
     public void setPoint( int a, int b ) // Set x and y coordinates of Point
     {  x = a;
        y = b;}
    
     public int getX() {return x; }  // get x coordinate
     public int getY() {return y; } // get y coordinate
     public String toString() { return "[" + x + ", " + y + "]"; } // convert the point into a String representation
  } // end of Class Point
 -----------------------------------
  //Test.java
  // to test class Point
  public class Test {
     public static void main( String args[] )
     {
        Point p = new Point( 72, 115 );
        String output;
        output = "X coordinate is " + p.getX() + "\nY coordinate is " + p.getY();
        p.setPoint( 10, 10 );
        // use implicit call to p.toString()
        output += "\n\nThe new location of p is " + p;
        System.out.println("Demonstrating Class Point\n" + output);
        System.exit( 0 );
     } // end of main method
  }  // end of Class Test
  ----------------------------
  //Circle.java
  // Definition of class Circle
  public class Circle extends Point {  // inherits from Point
     protected double radius;
     public Circle() // no-argument constructor
     {  // implicit call to superclass constructor
        setRadius( 0);}
    
     public Circle(double r, int a, int b ) // Constructor
     {  super( a, b);  // call the superclass constructor
        setRadius( r);}

     
     public void setRadius( double r ) // Set radius of Circle
        { radius = ( r >= 0.0 ? r : 0.0 ); }
     
     public double getRadius() { return radius; } // Get radius of Circle
     
     public double area() { return Math.PI * radius * radius; } // Calculate area of Circle
    
     public String toString() // convert the Circle to a String
        {return "Center = " + super.toString() + "; Radius = " + radius;}
  } // end of class Circle
  ----------------------------
  //Test.java
  // to test class Circle
  import java.text.DecimalFormat;
  public class Test {
     public static void main( String args[] )
     {
        Circle c = new Circle( 2.5, 37, 43 );
        DecimalFormat precision2 = new DecimalFormat( "0.00" );
        String output;
        output = "X coordinate is " + c.getX() + "\nY coordinate is " + c.getY() + "\nRadius is " + c.getRadius();
        // getX() and gety() are inherited from class Point, getRadius() and setRadius() are defined in Class Circle
		 c.setRadius(4.25 );  
        c.setPoint( 2, 2);  // setPoint() inherited from class Point
        output += "\n\nThe new location and radius of c are\n" + c +
           "\nArea is " + precision2.format( c.area() );   // area() of class Circle
        System.out.println("Demonstrating Class Circle\n" + output);
        System.exit(0);
     } // end of main method
  } // end of Class Test
  ------------------------------------
  //Cylinder.java
  // Definition of class Cylinder
  public class Cylinder extends Circle {
     protected double height;  // height of Cylinder
       public Cylinder() // No-argument constructor
     {  // implicit call to superclass constructor here
        setHeight( 0 ); }
    
       public Cylinder(double h, double r, int a, int b ) // constructor
     {  super( r, a, b);
        setHeight( h );
     }
       public void setHeight( double h ) { height = ( h >= 0 ? h : 0 ); } // Set height of Cylinder
         
       public double getHeight() { return height; }  // Get height of Cylinder


       public double area() // Calculate area of Cylinder (i.e., surface area)
          { return 2 * super.area() + 2 * Math.PI * radius * height;} 
       // this overrides area() in class Circle; area() is class Cylinder defined using area() from base class
       
       public double volume() { return super.area() * height; } // Calculate volume of Cylinder using area() method of 
       // class Circle
    
       public String toString() {return super.toString() + "; Height = " + height;} 
// Convert the Cylinder to a String using the toString method of class Circle
  } // end of Class Cylinder
 -----------------------------
  //Test.java
  // Application to test class Cylinder
  import java.text.DecimalFormat;
  public class Test {public static void main( String args[] )
     {
        Cylinder c = new Cylinder( 5.7, 2.5, 12, 23 );
        DecimalFormat precision2 = new DecimalFormat( "0.00" );
        String output;
        output = "X coordinate is " + c.getX() + "\nY coordinate is " + c.getY() +
                "\nRadius is " + c.getRadius() + "\nHeight is " + c.getHeight();
        c.setHeight( 10);
        c.setRadius(4.25 );
        c.setPoint( 2, 2);
        output += "\n\nThe new location, radius " + "and height of c are\n" + c + "\nArea is " + precision2.format( c.area() ) +
          "\nVolume is " + precision2.format( c.volume() );
        System.out.println("Demonstrating Class Cylinder\n" + output);
        System.exit(0);
     } // end of main method
  } // end of Class Test

Revised: November 18, 2008