循环队列

package com.example.datastructure;
/**
 * 使用顺序表（数组）实现循环队列
 * 初始化：head = tail = 0;
 * 入队： tail = (tail+1)%N
 * 出队： head = (head+1)%N
 * 判断队列空： head== tail
 * 判断队列满： (tail+1)%N == head
 * 队列长度： (N+tail-head)%N
 * */
public class LoopQueue {

    Object[] queue;
    int len;
    int head = 0 , tail = 0;

    public LoopQueue(int len) {
        this.queue = new Object[len];
        this.len = len;
    }


    /**
     * 入队
     * 队列满的条件：(tail+1)%len == head
    * */
    public Object enQueue(Object o){
        if ((tail+1)%len == head){
            System.out.println("queue is full");
            return null;
        }
        queue[tail] = o;
        tail = (tail+1)%len; // tail 回卷++,
        return o;
    }

    /**
     * 出队
     * 队列空的条件： head == tail
     * */
    public Object deQueue(){
        if (head == tail){
            System.out.println("Queue is empty");
            return null;
        }
        Object o = queue[head];
        head = (head+1) % len;
        return o;
    }

    public int size(){
        return (this.len+tail-head)%this.len;
    }


    public static void main(String[] args) {
        LoopQueue queue = new LoopQueue(100);
        for (int i = 0; i < 7; i++) {
            queue.enQueue(i);
        }
        System.out.println(queue.size());
        for (int i = 0; i < 7; i++) {
            System.out.println(queue.deQueue());
        }
        System.out.println(queue.size());
    }
}