class Duilie{     private LinkedList link;     Duilie(){         link = new LinkedList();     }     public void myAdd(Object obj){         link.addFirst(obj);     }     public Object myGet(){         return link.removeLast();//改为removeLast这样就可以是堆栈和队列的转换     }     public boolean isNull(){         return link.isEmpty();     } } public class LinkedListTest {     public static void main(String[] args) {         Duilie dl = new Duilie();         dl.myAdd("java01");         dl.myAdd("java02");         dl.myAdd("java03");         dl.myAdd("java04");         while (!dl.isNull()){             System.out.println(dl.myGet());         }     } }