队列——链式队列

public class LinkedQueue<E> {

    private Node<E> head = null;

    /**
     * 入队
     *
     * @param e
     * @return
     */
    public boolean enqueue(E e) {
        Node<E> node = new Node<>(e);
        if (head == null) {
            head = node;
        } else {
            Node tmpNode = this.head;
            while (tmpNode.nextNode != null) {
                tmpNode = tmpNode.nextNode;
            }
            tmpNode.nextNode = node;
        }
        return true;
    }

    /**
     * 出队
     *
     * @return
     */
    public E dequeue() {
        if(head == null) {
            return null;
        }
        Node<E> node = head;
        head = node.nextNode;
        return node.getT();
    }

    private class Node<T> {

        private T t;
        private Node nextNode;

        public Node(T t) {
            this.t = t;
        }

        public T getT() {
            return t;
        }

        public void setT(T t) {
            this.t = t;
        }
    }
}