package Queue;

/*
 @author: Roderland
 @create: 2020年08月11日---17:54
*/
public class MyLinkedQueue<E> {

 private Node<E> head;

 private Node<E> tail;

 private class Node<E> {
 E value;
 Node<E> next;

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

 public Node(E value, Node<E> next) {
 this.value = value;
 this.next = next;
 }
 }

 public boolean isEmpty() { return head==null; }

 public void push(E value) {
 Node<E> node = new Node<>(value);
 if (isEmpty()) head=tail=node;
 else {
 tail.next=node;
 tail=node;
 }
 }

 public E peek() {
 checkEmpty();
 return head.value;
 }

 public E pop() {
 checkEmpty();
 E o = head.value;
 head = head.next;
 return o;
 }

 private void checkEmpty() {
 if (isEmpty()) throw new IndexOutOfBoundsException("队列空");
 }
}