一个Thiking泛型的例子，突然发现理解了List<String>的原理

package com.liuc.test.think.chapter15;

public class LinkedStack<T> {

private static class Node<U>{
U item;
Node<U> next;
Node(){
item=null; next=null;
}
Node(U item,Node<U> next){
this.item=item;
this.next=next;
}

boolean end(){
return item==null&&next==null;
}

}
private Node<T> top=new Node<T>();
public void push(T item){
top=new Node<T>(item, top);
}

public T pop(){
T result=top.item;
if(!top.end()){
top=top.next;
}
return result;
}
/**
* @param args
*/
public static void main(String[] args) {
LinkedStack<String> lss=new LinkedStack<String>();
for(String s:"Phrasers on stun!".split(" ")){
lss.push(s);
}
String s;
while((s=lss.pop())!=null){
System.out.println(s);
}

}

}