分析Java非阻塞算法Lock-Free的实现

public class Node<E> {
    public final E item;
    public Node<E> next;

    public Node(E item){
        this.item=item;
    }
}

public class ConcurrentStack<E> {

    AtomicReference<Node<E>> top= new AtomicReference<>();

    public void push(E item){
        Node<E> newNode= new Node<>(item);
        Node<E> oldNode;
        do{
            oldNode=top.get();
            newNode.next= oldNode;
        }while(!top.compareAndSet(oldNode, newNode));
    }

    public E pop(){
        Node<E> oldNode;
        Node<E> newNode;
        do {
            oldNode = top.get();
            if(oldNode == null){
                return null;
            }
            newNode=oldNode.next;
        }while(!top.compareAndSet(oldNode, newNode));
        return oldNode.item;
    }

}

public class LinkedNode<E> {
    public final E item;
    public final AtomicReference<LinkedNode<E>> next;

    public LinkedNode(E item, LinkedNode<E> next){
        this.item=item;
        this.next=new AtomicReference<>(next);
    }
}

public class LinkedQueue<E> {
    private final LinkedNode<E> nullNode= new LinkedNode<>(null, null);
    private final AtomicReference<LinkedNode<E>> head= new AtomicReference<>(nullNode);
    private final AtomicReference<LinkedNode<E>> tail= new AtomicReference<>(nullNode);

    public boolean put(E item){
    LinkedNode<E> newNode = new LinkedNode<>(item, null);
    while (true){
        LinkedNode<E> currentTail= tail.get();
        LinkedNode<E> tailNext= currentTail.next.get();
        if(currentTail == tail.get()){
            if (tailNext != null) {
                //有其他的线程已经插入了一个节点，但是还没有将tail指向最新的节点
                tail.compareAndSet(currentTail, tailNext);
            }else{
                //没有其他的线程插入节点，那么做两件事情：1. 插入新节点，2.将tail指向最新的节点
                if(currentTail.next.compareAndSet(null, newNode)){
                    tail.compareAndSet(currentTail, newNode);
                }
            }
        }
    }
    }
}