Java Project #1 : The Sphere Problem

This is a straightforward problem. This little ditty computes the volume and surface area of a sphere. Java is fun, no?

/**
 * SphereProblem reads the radius of a sphere from the user and computes its volume and surface area, then prints them out..
 * 
 * @author (Andrew Samuels) 
 * @version (02-01-2010)
 */
//import scanner class
import java.util.Scanner;

public class SphereProblem
{

    public static void main(String[] args)
    {
        //initialize variables
        double radius; //radius of a sphere
        double volume; //volume of a sphere
        double area; //area of a sphere
        double PI = 3.1415;
        
        //create scanner
        Scanner keyboard = new Scanner(System.in);
        
        //input radius from the user
        System.out.print("Please enter radius of a sphere: ");
        radius = keyboard.nextDouble();
        
        //calculate volume
        volume = (4/3)*PI*radius*radius*radius;
    
        //calculate area
        area = 4*PI*radius*radius;
        
        //print volume
        System.out.println("Volume of sphere is: " + volume);
        
        //print area
        System.out.println("Area of sphere is: " + area);
        
    }
}