public Item delete(int i) {
		// TODO Auto-generated method stub
		if (i < 0 || i >= n) 
			throw new IllegalArgumentException("参数i非法");
		Item item = items[i]; 
		for (int k = i+1; k < n; k++) {
			items[k-1] = items[k];
		}
		n--;
		if (n <= items.length/4) resize(items.length/2);
		return item;
	}