數據結構之棧(用list實現)

棧(stack)這種數據結構用得相當那個廣泛。用list實現相當方便。特點就是FILO(先進，後出)

public class MyStack {
	private MyLinkedList lists;
	
	public MyStack(){
		lists=new MyLinkedList();
	}
	
	//將新元素壓入棧中，位居棧頂
	public void push(int num){
		lists.addFirst(num);
	}
	
	//將棧頂元素彈出棧
	public void pop(){
		if(lists.size()==0)
			throw new NullPointerException();
		lists.deleteFirst();
	}
	
	//獲取棧頂元素，並不刪除
	public int top(){
		if(lists.size()==0)
			throw new NullPointerException();
		return lists.getFirst();
	}
	
	public boolean isEmpty(){
		return lists.size()==0;
	}