public class LinkQueue<T> {// 定义内部类Node, Node实例代表链队列的节点private class Node {// 保存节点的数据private T data;// 指向下个节点的引用private Node next;// 无参数的构造器public Node() {}// 初始化全部属性的构造器public Node(T data, Node next) {this.data = data;this.next = next;}}// 保存该链队列的头节点private Node front;// 保存该链队列的尾节点private Node rear;// 保存该链队列中已包含的节点数private int size;// 创建空链队列public LinkQueue() {// 空链队列，front和rear都是nullfront = null;rear  = null;}// 以指定数据元素来创建链队列，该链队列只有一个元素public LinkQueue(T element) {front = new Node(element, null);// 只有一个节点，front、rear都指向该节点rear = front;size++;}// 返回链队列的长度public int length() {return size;}// 将新元素加入队列public void add(T element) {// 如果该链队列还是空链队列if (front == null) {front = new Node(element, null);// 只有一个节点,front、rear都指向该节点rear = front;} else {// 创建新节点Node newNode = new Node(element, null);// 让尾节点的next指向新增的节点rear.next = newNode;// 以新节点作为新的尾节点rear = newNode;}size++;}// 删除队列front端的元素public T remove() {Node oldFront = front;front = front.next;oldFront.next = null;size--;return oldFront.data;}// 访问链式队列中最后一个元素public T element() {return rear.data;}// 判断链式队列是否为空队列public boolean empty() {return size == 0;}// 清空链public void clear() {// 将front、rear两个节点赋为nullfront = null;rear  = null;size  = 0;}public String toString() {if (empty()) {return "[]";} else {StringBuilder sb = new StringBuilder("[");for (Node current = front; current != null; current = current.next) {sb.append(current.data.toString() + ", ");}int len = sb.length();return sb.delete(len - 2, len).append("]").toString();}}
}

public class LinkQueueTest {public static void main(String[] args) {LinkQueue<String> queue = new LinkQueue<String>("aaaa");queue.add("bbbb");queue.add("cccc");System.out.println("链队列初始化元素：" + queue.toString());queue.remove();System.out.println("删除一个元素后队列：" + queue.toString());queue.add("dddd");System.out.println("再次添加元素后的队列：" + queue);queue.remove();queue.add("eeee");System.out.println(queue);}
}