Here you can find the source of createConcurrentStack()
public static <E> Queue<E> createConcurrentStack()
//package com.java2s; //License from project: Apache License import java.util.Collections; import java.util.Deque; import java.util.Queue; public class Main { public static <E> Queue<E> createConcurrentStack() { return (Queue<E>) Collections.asLifoQueue(newConcurrentNonBlockingDeque()); }/*from w w w. j a va2s. com*/ public static <E> Deque<E> newConcurrentNonBlockingDeque() { return new java.util.concurrent.ConcurrentLinkedDeque<E>(); } }