public class LinkedStack<T> {
//末端哨兵
private static class Node<U> {
Node<U> next;
U item;
Node() {
next = null;
item = null;
}
public Node(Node<U> next, U item) {
this.next = next;
this.item = item;
}
public boolean end() {
return next == null && item == null;
}
}
private Node<T> top = new Node<>();
public void push(T item){
top = new Node<>(top, item);
}
public T pop(){
T item = top.item;
if(!top.end())
top = top.next;
return item;
}
public static void main(String[] args) {
LinkedStack<String> stack = new LinkedStack<>();
for (String s: "sss aaa qqq".split(" ")) {
stack.push(s);
}
String s;
while ((s = stack.pop()) != null){
System.out.println(s);
}
}
}
采取了内部类定义一个末端哨兵来判断栈是否为空。