Thread: Sphere (Volume/Surface Area)

A question (not homework, a question from a book, don't worry) asks me to create a program to work out the volume and surface area of a sphere.

The surface area part works fine, it is the volume which comes up with the wrong answers. I can't see anything wrong with the formula so I assuming it must be a coding error on my part. Also feel free to criticise general coding standards. The more it hurts the more it helps

Thanks

public class Sphere {
 
	public double diameter;
	private double radius, volume, surfaceArea;
 
	public Sphere() {
		diameter = 1;	
	}
 
	public void setDiameter (double value) {
		diameter = value;
	}
 
	public double getDiameter() {
		return diameter;
	}
 
	private double radius() {
		radius = diameter / 2;
		return radius;
	}
 
	private double volume() {
		volume = (4/3) * Math.PI * Math.pow(radius(), 3);
		return volume;
	}
 
	private double surfaceArea() {
		surfaceArea = 4 * Math.PI * Math.pow(radius(), 2);
		return surfaceArea;
	}
 
	public String toString() {
		String result = "Volume: " + Double.toString(volume()) + " Surface area: " + Double.toString(surfaceArea());
 
		return result;
	}
 
 
}

public class MultiSphere {
 
	public static void main(String[] args) {
 
		Sphere sph1, sph2;
 
		sph1 = new Sphere();
		sph2 = new Sphere();
 
		sph1.setDiameter(4);
		sph2.setDiameter(10);
 
		System.out.println(sph1);
		System.out.println(sph2);
 
	}
}

Thank you for pointing that out. I didn't notice it. By changing part of the code to this:

private double volume() {
		volume = 1.33333333 * Math.PI * Math.pow(radius(), 3);
		return volume;

The program works. I have just done some quick reading on the subject but don't really get how I can implement a solution. Could you give a pointer towards a good explanation if you know of one.

Thank you, that works a treat