int initialDegrees;
    int heading;


    /**
     * Constructor for objects of class CompassHeading
     */
    public CompassHeading(int initialDegrees)
    {
        // initialise instance variables
        if (initialDegrees<0 || initialDegrees>360) {
            throw new IllegalArgumentException("heading out of bounds");
        }
        else {
            heading = initialDegrees;
        }