一个基本的栈java实现

public class ResizingArrayStack<Item> implements Iterable<Item> {
	private int N;

	private Item[] a = (Item[]) new Object[10];

	public Item pop() {
		Item item = a[--N];
		a[N] = null;
		if (N > 0 && N == a.length / 4) {
			resize(a.length / 2);
		}
		return item;
	}

	public void push(Item item) {
		if (N == a.length) {
			resize(a.length * 2);
		}
		a[N++] = item;
	}

	private void resize(int newSize) {
		Item[] temp = (Item[]) new Object[newSize];
		for (int i = 0; i < N; i++) {
			temp[i] = a[i];
		}
		a = temp;
	}

	public Boolean isEmpty() {
		return N == 0;
	}

	public int size() {
		return N;
	}

	@Override
	public Iterator<Item> iterator() {
		return new ReverseArrayIterator();
	}

	private class ReverseArrayIterator implements Iterator<Item> {
		private int i;

		@Override
		public boolean hasNext() {
			return i > 0;
		}

		@Override
		public void remove() {
			
		}

		@Override
		public Item next() {
			return a[--i];
		}
	}


}