public class Planet implements Measureable
{
  private int number;
  private double radius;

  public Planet(int n, double r)
  {
    number = n;
    radius = r;
  }

  // The value or size of the planet will be its volume.
  public double getValue()
  {
    return 4.0/3 * Math.PI * radius * radius * radius;
  }

  public String toString()
  {
    return "Planet #" + number + ", radius = " + radius;
  }
}