Circle class!

Seems like I am the only one who is posting in the java section =(
Well its not that I have the problems , I am just want you to look over my code and tell me what you think. You know, I just need a professional advice. I will delete the problem text so people wont cheat on the homework.

The problem:

        Circle Class Write a Circle class that has the following fields: • radius: a double • PI: a final double initialized with the value 3.14159 The class should have the following methods: • Constructor. Accepts the radius of the circle as an argument. • Constructor. A no-arg constructor that sets the radius field to 0.0. • setRadius. A mutator method for the radius field. • getRadius. An accessor method for the radius field. • getArea. Returns the area of the circle, which is calculated as area = PI * radius * radius • getDiameter. Returns the diameter of the circle, which is calculated as diameter = radius * 2 • getCircumference. Returns the circumference of the circle, which is calculated as circumference = 2 * PI * radius Write a program that demonstrates the Circle class by asking the user for the circle's radius, creating a Circle object, and then reporting the circle's area, diameter, and circumference.



My solution:

THE CIRCLE CLASS


/*
 * The Circle class hold data about a circle.
 *
 */

/**
 *
 * @author Alexander Trowell
 */
public class Circle
{
    // Fields

    private double radius;               // Radius of the circle
    final private double PI = 3.14159;   // The value of the PI

    /**
     * Constructor
     *
     * @param radius The circles radius
     */
   
    public Circle(double radius)
    {
        this.radius = radius;
    }

    /**
     * Constructor No arg constructor that the sets the radius field to 0.0
     */
   
    public Circle()
    {
        radius = 0.0;
    }
   
/**
 * The setRadius method sets the Circles radius
 * @param radius returns radius of the circle
 */
   
    public void setRadius(double radius)
    {
        this.radius = radius;
    }
   
    /**
     * The getRadius method
     * @return the radius of the circle
     */
   
    public double getRadius()
    {
        return radius;
    }
   
    /**
     * The getArea method
     * @return the area of the circle
     */
   
    public double getArea()
    {
       return PI * radius * radius;
    }
   
    /**
     * The getDiameter method
     * @return the diameter of the circle
     */
   
    public double getDiameter()
    {
     return radius * 2;
    }
   
    /**
     * The getCircumference method
     * @return the circumference of the circle
     */
   
    public double getCircumference()
    {
        return 2 * PI * radius;
    }
}

Main MEHOD



import java.util.Scanner;


/**
 *
 * @author Alexander Trowell
 */
public class CircleDemo {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
      
        double radius; // To hold a radius
       
        // Create a Scanner object for keyboard input
        Scanner scan = new Scanner(System.in);
       
        // Get the number for the radius
        System.out.println("Please enter the circle's radius");
        radius = scan.nextDouble();
       
        // Create an instance of the Circle class,
        // passing the data that was entered as arguments
        // to the constructor.
 
        Circle circle1 = new Circle(radius);
       
       
        // Output
        System.out.println("The area of the circle with radius of "+radius+" is "+ circle1.getArea()
                +" with diameter of "+circle1.getDiameter()+" and with circumference of "+circle1.getCircumference());
    }
}