// Here is a partial implementation of that interface. Many
// implementations may find this a useful starting point. 
public abstract class AbstractRectangularShape implements RectangularShape {
    // The position and size of the shape
    protected double x, y, w, h;

    // Default implementations of some of the interface methods
    public void setSize(double width, double height) { w = width; h = height; }
    public void setPosition(double x, double y) { this.x = x; this.y = y; }
    public void translate (double dx, double dy) { x += dx; y += dy; }
}