Method convert

java/Chapter 14/Question14_6/CircularArray.java:13–18

(int index)

	}
	
	private int convert(int index) {
		if (index < 0) {
			index += items.length;
		}
		return (head + index) % items.length;
	}
	
	public void rotate(int shiftRight) {
		head = convert(shiftRight);