public double getRotationAngle() {
        return this.rotationAngle; 
    }
    
    /**
     * Sets the rotation angle.  The angle is measured clockwise in radians.
     * 
     * @param angle  the angle (in radians).
     * 
     * @see #getRotationAngle()
     */
    public void setRotationAngle(double angle) {
        this.rotationAngle = angle;