LinkedListQueue.java

package com.learn.queue;

public class LinkedListQueue {
    // 队列的队首和队尾
    private Node head = null;
    private Node tail = null;

    // 入队
    public void enqueue(String value) {
        if (tail == null) {
            Node newNode = new Node(value, null);
            head = newNode;
            tail = newNode;
        } else {
            tail.next = new Node(value, null);
            tail = tail.next;
        }
    }

    // 出队
    public String dequeue() {
        if (head == null) return null;

        String value = head.data;
        head = head.next;
        if (head == null) {
            tail = null;
        }
        return value;
    }


    private class Node {
        private String data;
        private Node next;

        public Node(String data, Node next) {
            this.data = data;
            this.next = next;
        }

    }
}