Linkedlist和Array實現Stack

LinkedList實現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實現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;
	}
}