java实现_用数组实现栈

//引自<算法>第四版 栈的实现代码class Queue<Item>{private Item[] a;private int N = 0;public Queue(int n){a = (Item[]) new Object[n];}public boolean isEmpty(){return N==0;}public Item pop(){Item item = a[--N];a[N] = null;        //动态改变数组大小        if(N > 0 && N < a.length * 0.25){resize(a.length/2);}return item;}public void push(Item item){if(N == a.length){resize(2*a.length);}a[N++] = item;}        public void resize(int max){Item[] temp = (Item[]) new Object[max];for(int i=0; i<N; i++){temp[i] = a[i];}a = temp;}public int size(){return N;}}