USER-DEFINED CLASSES AND ADTS - Java Programming: From Problem Analysis to Program Design - page 496

EXAMPLE 8-4

In this example, we give the complete definition of the class Circle , which was briefly
discussed in the beginning of this chapter.
public class Circle
{

private double radius;

//Default constructor
//Sets the radius to 0
Circle()
{

radius = 0;

}

//Constructor with a parameter
//Sets the radius to the value specified by the parameter r.
Circle( double r)
{

radius = r;

}

//Method to set the radius of the circle.
//Sets the radius to the value specified by the parameter r.
public void setRadius( double r)
{

radius = r;

}

//Method to return the radius of the circle.
//Returns the radius of the circle.
public double getRadius()
{

return radius;

}

//Method to compute and return the area of the circle.
//Computes and returns the area of the circle.
public double area()
{

return Math.PI * Math.PI * radius;

}

//Method to compute and return the perimeter of the circle.
//Computes and returns the area of the circle.
public double perimeter()
{

return 2 * Math.PI * radius;

}

//Method to return the radius, area, perimeter of the circle
//as a string.