gistfile1.java

public class ArrayQueueADT {
    private Object[] elements = new Object[10];
	private int end = 5;
	private int start = 5;
	private int size = 0;
	
	public static void enqueue(ArrayQueueADT queue, Object element) {
		assert element != null;
		ensureCapacity(queue,queue.size+1);
		queue.elements[queue.end] = element;
		if (queue.end - 1 >= 0) {
			queue.end = queue.end - 1;
		}
		else {
			queue.end = queue.elements.length - 1;
		}
		queue.size++;
	}
	
	private static void ensureCapacity(ArrayQueueADT queue, int capacity) {
		if (queue.elements.length <= capacity) {
			Object[] e = new Object[2 * capacity];
			for (int i = 0; i <= queue.start; i++) {
				e[i] = queue.elements[i];
			}
			for (int i = queue.end + capacity; i < 2 * capacity; i++) {
				e[i] = queue.elements[i - capacity];
			}
			queue.end = queue.end + capacity;
			queue.elements = e;
		}
	}
	
	public static Object dequeue(ArrayQueueADT queue) {
		assert queue.size > 0;
		Object result = queue.elements[queue.start];
		if (queue.start - 1 >= 0) {
			queue.start = queue.start - 1;
		}
		else {
			queue.start = queue.elements.length - 1;
		}
		queue.size--;
		return result;
	}
	
	public static Object peek(ArrayQueueADT queue) {
		assert queue.size > 0;
		return queue.elements[queue.start];
	}
	
	public static boolean isEmpty(ArrayQueueADT queue) {
		return queue.size == 0;
	}
	
	public static int size(ArrayQueueADT queue) {
		return queue.size;
	}
}