LeetCode 上 关于问题：622. 设计循环队列，老师，我参照之前咱们写的LoopQueue代码，写了一套，但是在获取队列尾部元素的时候有点问题，tail和tail+1有点被绕晕了，回去查看了一下PDF文档，还是不明白这地方，希望老师能帮我解释一下，tail这个位置，到底存放不存放元素，tail+1的位置存不存放元素，现在对这两个位置的概念，有点模糊，我先贴一下我的代码：

public class MyCircularQueue {

private int[] array;//利用数据来实现
private int front, tail;//头部和尾部的数组向量坐标
private int size;

/**
 * Initialize your data structure here. Set the size of the queue to be k.
 */
public MyCircularQueue(int capacity) {
    this.array = new int[capacity + 1];//要空出一个元素来,不参与size计数，只是为了front和tail后续位置的不重叠，实际容量为capacity
    this.front = this.tail = 0;
    this.size = 0;
}

/**
 * Insert an element into the circular queue. Return true if the operation is successful.
 */
public boolean enQueue(int value) {
    if (!this.isFull()) {
        this.array[tail] = value;
        this.tail = (tail + 1) % array.length;
        this.size++;
        return true;
    }
    return false;
}

/**
 * Delete an element from the circular queue. Return true if the operation is successful.
 */
public boolean deQueue() {
    //把front往前挪一个位置
    if (!this.isEmpty()) {
        front = (front + 1) % array.length;
        this.size--;
        return true;
    }
    return false;
}

/**
 * Get the front item from the queue.
 */
public int Front() {
    return this.array[front];
}

/**
 * Get the last item from the queue.
 */
public int Rear() {// 1 2 3 4
    return this.array[tail % array.length];
}

/**
 * Checks whether the circular queue is empty or not.
 */
public boolean isEmpty() {
    return this.front == this.tail;

}

public String toString() {
    //此处的理解，需要加深
    StringBuilder loopQueue = new StringBuilder();
    loopQueue.append(String.format("LoopQuene:size=%d\n", size));
    loopQueue.append("front[");
    for (int i = front; i != tail; i = (i + 1) % array.length) {
        loopQueue.append(array[i]);
        if ((i + 1) % array.length != tail) {
            loopQueue.append(",");
        }
    }
    loopQueue.append("]tail");
    return loopQueue.toString();
}

/**
 * Checks whether the circular queue is full or not.
 */
public boolean isFull() {
    return ((this.tail + 1) % array.length) == this.front;
}

public static void main(String[] args) {
    MyCircularQueue circularQueue = new MyCircularQueue(3); // 设置长度为3

    System.out.println(circularQueue.enQueue(1));
    ;  // 返回true

    System.out.println(circularQueue.enQueue(2));
    ;  // 返回true

    System.out.println(circularQueue.enQueue(3));
    ;  // 返回true
    System.out.println(circularQueue.toString());
    System.out.println(circularQueue.enQueue(4));
    ;  // 返回false,队列已满

    System.out.println(circularQueue.Rear());
    ;  // 返回3

    System.out.println(circularQueue.isFull());
    ;  // 返回true

    System.out.println(circularQueue.deQueue());
    ;  // 返回true
    System.out.println(circularQueue.toString());
    System.out.println(circularQueue.enQueue(4));
    ;  // 返回true
    System.out.println(circularQueue.toString());
    System.out.println(circularQueue.Rear());
    ;  // 返回4
}