Java用LinkedList实现栈

import java.util.LinkedList;

public class MyStack {
	private LinkedList ll=new LinkedList();
	public void push(Object o)
	{
		ll.addFirst(o);
	}
	public Object pop()
	{
		if(ll.isEmpty())
		{
			System.out.println("栈为空，不能出栈！");
			return null;
		}
		return ll.removeFirst();
	}
	public Object peek()
	{
		return ll.getFirst();
	}
	public boolean empty()
	{
		return ll.isEmpty();
	}
	public static void main(String []args)
	{
		MyStack ms=new MyStack();
		ms.push("one");
		ms.push("two");
		ms.push("three");
		System.out.println(ms.pop());
		System.out.println(ms.peek());
		System.out.println(ms.pop());
		System.out.println(ms.empty());
	}
}

three
two
two
false