// generics/LinkedStack.java

// (c)2017 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// A stack implemented with an internal linked structure

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<>(); // End sentinel

public void push(T item) {

top = new Node<>(item, top);

}

public T pop() {

T result = top.item;

if(!top.end())

top = top.next;

return result;

}

public static void main(String[] args) {

LinkedStack<String> lss = new LinkedStack<>();

for(String s : "Phasers on stun!".split(" "))

lss.push(s);

String s;

while((s = lss.pop()) != null)

System.out.println(s);

}

}

/* Output:

stun!

on

Phasers

*/