public class Circle {
  public double radius;

  /* "Default" constructor */
  public Circle() {
  }

  /* Constructor that takes a radius */
  public Circle(double r) {
    radius = r;
  }

  /* Area method */
  public double getArea() {
   return Math.PI*radius*radius;
  }

  /* Circumference method */
  public double getCircumference() {
   return 2.0*Math.PI*radius;
  }

  /* Diameter method */
  public double getDiameter() {
   return 2.0*radius;
  }

  /* Radius method */
  public double getRadius() {
   return radius;
  }
}