1、源码

CircleArrayQueue

package com.study.queue;
//使用数组模拟一个队列
public class CircleArrayQueue {
        private int maxSize;//表示数组的最大容量
        private int front;//队列头,初始值为0
        private int rear;//队列尾，初始值为0
        private int[] arr;//该数组用于存放数据，模拟队列
        //创建队列构造器
        public CircleArrayQueue(int arrMaxSize) {
            maxSize = arrMaxSize;
            arr = new int[maxSize];
        }
        //判断队列是否满
        public boolean isFull() {
            return (rear+1)%maxSize==front;
        }
        //判断队列是否空
        public boolean isEmpty() {
            return front == rear;
        }
        //添加数据到队列
        public void addQueue(int n) {
            if (isFull()) {
                System.out.println("队列满，不能加数据");
                return;
            }
            arr[rear] = n;
            rear = (rear+1)%maxSize;
        }
        //获取队列的数据
        public int getQueue() {
            if (isEmpty()) {
                throw new RuntimeException("队列空，不能去数据");
            }
            int value= arr[front];
            front = (front+1)%maxSize;
            return value;
        }
        //显示队列所有数据
        public void show() {
            if (isEmpty()) {
                System.out.println("队列空，没有数据");
                return;
            }
            for (int i = front; i < front + size(); i++) {
                System.out.println(arr[i%maxSize]);
            }
        }
        //求出当前数组有效数据的个数
        public int size(){
            return (rear+maxSize-front)%maxSize;
        }
        //显示队列的头数据
        public int headQueue() {
            if (isEmpty()) {
                throw new RuntimeException("队列空，没有数据");
            }
            return arr[front];
        }
}

CircleArrayQueueDemo

package com.study.queue;
import java.util.Scanner;
public class CircleArrayQueueDemo {
    public static void main(String[] args) {
        CircleArrayQueue queue = new CircleArrayQueue(4);
        String key = null;
        Scanner scanner = new Scanner(System.in);
        boolean loop = true;
        System.out.println("s(show),显示队列");
        System.out.println("e(exit),退出程序");
        System.out.println("a(add),添加数据到队列");
        System.out.println("g(get),从队列中获取数据");
        System.out.println("h(head),显示队列头的数据");
        while (loop) {
            key = scanner.nextLine();
            switch (key) {
                case "s":
                    queue.show();
                    break;
                case "a":
                    System.out.println("输入一个数");
                    int value = scanner.nextInt();
                    queue.addQueue(value);
                    break;
                case "g":
                    try {
                        int res = queue.getQueue();
                        System.out.println("取出的数据是" + res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "h":
                    try {
                        int res = queue.headQueue();
                        System.out.println("队列头的数据是" + res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case "e":
                    scanner.close();
                    loop = false;
                    break;
                default:
                    break;
            }
        }
        System.out.println("程序退出");
    }
}

2、运行结果

通过环形队列，可以解决数组只能使用一次的问题

3、总结

尾索引的下一个为头索引时表示队列满，即将队列容量空出一个作为约定,这个在做判断队列满的时候需要注意 (rear + 1) % maxSize == front [满]
rear == front [空]