Linkedlist和Array实现Stack

LinkedList实现Stack

public Class Stack<Item>{private Node first = null;private class Node{Item item;Node next;    }public boolean isEmpty(){ return first == null;}public void push(Item item){Node second = first;first = new Node();first.item = item;first.next = second;}public Item pop(){Item item = first.item;first = first.next;return item;}}

Array实现Stack

public Class Stack<Item>{private Item[] s;private int N = 0;public Stack(int cap){s= new Item[cap];    }public boolean isEmpty(){ return N==0;}public void push(Item item){s[N++] = item;}public Item pop(){Item item = s[N-1];s[N-1] = null;N--;return item;}}