First we will redevelop the Point class, then we will develop the Circle class and then we will test them.

Now the code for Point.java should be copied into a new directory.

// Point.java
// Setting a point

package edu.quinnipiac.javaProgs.geometry;

public class Point
{
protected int x, y;

// No argument constructor
public Point()
{
// implicit call to superclass constructor occurs here
setPoint(0,0);
}

// Constructor
public Point(int a, int b)
{
// implicit call to superclass constructor occurs here
setPoint(a,b);
}

// Set the x and y coordinates of Point
public void setPoint(int a, int b)
{
x = a;
y = b;
}

// get x coordinate
public int getX()
{
return x;
}

// get y coordinate
public int getY()
{
return y;
}

// convert the point into a String representation
public String toString()
{
return "[" + x + ", " + y + "]";
}
}

Now we want to test this class we've developed after making sure we use the 

javac -d c:\jdk1.2.1\jre\classes Point.java

to create the package class.

Now you want to test this with TestPoint.java.

// TestPoint.java
// Application to test class Point

import javax.swing.JOptionPane;
import edu.quinnipiac.javaProgs.geometry.Point;

public class TestPoint
{
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 = output + "\n\nThe new location of p is " + p;

JOptionPane.showMessageDialog(null, output, "Demonstrating Class Point", JOptionPane.INFORMATION_MESSAGE);

System.exit(0);
}
}

Now we are going to take this even further by developing a Cylinder class by inheriting the Circle class.  You want to copy the following code and call it Cylinder.java.

// Cylinder.java

package edu.quinnipiac.javaProgs.geometry;

public class Cylinder extends Circle
{
protected double height;

// No-argument constructor
public Cylinder()
{
// implicit call to superclass constructor
setHeight(0);
}

// Constructor
public Cylinder(double h, double r, int a, int b)
{
super(r,a,b);
setHeight(h);
}

// Set height of cylinder
public void setHeight(double h)
{
if (h >= 0)
height = h;
else
height = 0;
}

// Get height of cylinder
public double getHeight()
{
return height;
}

// Calculate surface area of the cylinder
public double area()
{
return 2 * super.area() + (2 * Math.PI * radius * height);
}

// Calculate volume of Cylinder
public double volume()
{
return super.area() * height;
}

// Convert the cylinder to a string
public String toString()
{
return super.toString() + "; Height = " + height;
}
}

Because you are creating a package you need to make sure you use the compile command with the path and the -d.  

Now you need to execute the TestCylinder.java application.

// TestCylinder.java

import javax.swing.JOptionPane;
import java.text.DecimalFormat;
import edu.quinnipiac.javaProgs.geometry.Cylinder;

public class TestCylinder
{
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 = 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());

JOptionPane.showMessageDialog(null, output, "Demonstrating Class Cylinder",
JOptionPane.INFORMATION_MESSAGE);

System.exit(0);

}
}

This makes use of a fairly elaborate system of packaging and inheritance.