队列满，则进行♻️循环处理。

    1. /**
    2.  * 先进先出
    3.  *
    4.  * @author luobo.cs@raycloud.com
    5.  * @since 2021/7/25 10:47 上午
    6.  */
    7. public class ArrayListQueue<E> {
    10.     private final Object[] elements;
    12.     private int tail;
    13.     private int head;
    14.     private int size = 0;
    16.     private final int initialCapacity;
    18.     public ArrayListQueue(int initialCapacity) {
    19.         this.initialCapacity = initialCapacity;
    20.         this.elements = new Object[this.initialCapacity];
    21.         tail = 0;
    22.         head = 0;
    23.     }
    25.     public int size() {
    26.         return size;
    27.     }
    29.     /**
    30.      * 添加
    31.      */
    32.     public void push(E e) {
    33.         if (e == null) {
    34.             throw new NullPointerException("element can't be null");
    35.         }
    36.         if (size >= initialCapacity) {
    37.             throw new ArrayIndexOutOfBoundsException("queue is full");
    38.         }
    39.         elements[tail] = e;
    40.         tail++;
    41.         size++;
    42.         if (tail >= initialCapacity) {
    43.             tail = 0;
    44.         }
    45.         if (size >= initialCapacity) {
    46.             size = initialCapacity;
    47.         }
    48.     }
    50.     @SuppressWarnings("unchecked")
    51.     public E poll() {
    52.         final Object element = elements[head];
    53.         if (element == null) {
    54.             return null;
    55.         }
    56.         elements[head] = null;
    57.         head++;
    58.         size--;
    59.         if (head >= initialCapacity) {
    60.             head = 0;
    61.         }
    62.         if (size <= 0) {
    63.             size = 0;
    64.         }
    65.         return (E) element;
    66.     }
    68.     public static void main(String[] args) {
    69.         ArrayListQueue<String> queue = new ArrayListQueue<>(3);
    70.         queue.push("11");
    71.         queue.push("22");
    72.         queue.push("33");
    73.         System.out.println(queue.poll());
    74.         System.out.println(queue.poll());
    75.         System.out.println(queue.poll());
    76.         System.out.println(queue.poll());
    77.         queue.push("44");
    78.         queue.push("55");
    79.         queue.push("66");
    80.         System.out.println(queue.poll());
    81.         System.out.println(queue.poll());
    82.         System.out.println(queue.poll());
    83.     }
    84. }