循环队列

import java.util.Scanner;

/**
 * @Author SerMs
 * @Date 2022/3/20 18:39
 * @Version 1.0
 */
public class CircleArrayQueueDemo {
    public static void main(String[] args) {
        System.out.println("测试数组模拟环形队列的案例~~~~~");
        //创建一个队列
        CircleArray circleArray = new CircleArray(4); //说明设置4.其队列的有效数据最大是3
        char key = ' '; //接收用户输入
        Scanner scanner = new Scanner(System.in);
        boolean loop = true;
        //输出一个菜单
        while (loop) {
            System.out.println("s(show): 显示队列");
            System.out.println("e(exit): 推出队列");
            System.out.println("a(add): 添加数据到队列");
            System.out.println("g(get): 从队列取出数据");
            System.out.println("h(head): 查看队列头的数据");
            key = scanner.next().charAt(0); //接收一个字符
            switch (key) {
                case 's':
                    try {
                        circleArray.showQueue();
                        break;
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                        break;
                    }
                case 'a':
                    System.out.println("请输入一个数");
                    int value = scanner.nextInt();
                    circleArray.addQueue(value);
                    break;
                case 'g': //取出数据
                    try {
                        int res = circleArray.getQueue();
                        System.out.printf("取出的数据是: %d\n", res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h':
                    try {
                        int res = circleArray.headQueue();
                        System.out.printf("队列头数据是:%d\n", res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e':
                    scanner.close();
                    loop = false;
                    break;
                default:
                    break;
            }
        }
        System.out.println("退出队列~~~");
    }
}

class CircleArray {
    private int maxSize;  //表示数组的最大容量
    //front的初始值=0 也就是说arr[front]就是队列的第一个元素
    private int front;  //队列头
    //rear的初始值=0 rear指向队列的最后一个元素的后一个位置,因为希望空出一个空间作为约定
    private int rear;   //队列尾
    private int[] arr; //该数组用于存放数据,模拟队列

    //创建队列构造器

    public CircleArray(int arrMaxSize) {
        this.maxSize = arrMaxSize;
        this.arr = new int[this.maxSize];
    }

    //判断队列是否满
    public boolean isFull() {
        return (rear + 1) % maxSize == front;
    }

    //判断队列是否为空
    public boolean isEmpty() {
        return rear == front;
    }

    //添加数据到队列
    public void addQueue(int n) {
        if (isFull()) {
            System.out.println("队列满,不能加入数据~~~");
        }
        //直接将数据加入
        arr[rear] = n;
        //将rear后移,必须考虑取模
        rear = (rear + 1) % maxSize;
    }

    //获取队列的数据,出队列
    public int getQueue() {
        //判断队列是否为空
        if (isEmpty()) {
            throw new RuntimeException("队列为空,不能获取数据");
        }
        //分析出front是指向队列的第一个元素
        //1.先把front对应的值保存到临时变量
        //2.将front后移 考虑取模
        //3.将临时保存的变量返回
        int value = arr[front];
        front = (front + 1) % maxSize;
        return value;
    }

    //显示所有数据
    public void showQueue() {
        //遍历
        if (isEmpty()) {
            throw new RuntimeException("队列为空,不能获取数据");
        }
        //思路:从front开始遍历,遍历多少个元素
        //
        for (int i = front; i < front + size(); i++) {
            System.out.printf("arr[%d] = %d\n", i % maxSize, arr[i % maxSize]);
        }
    }

    //求出当前队列有效数据的个数
    public int size() {
        return (rear + maxSize - front) % maxSize;
    }

    //显示队列头数据,不是取出数据
    public int headQueue() {
        //判断
        if (isEmpty()) {
            throw new RuntimeException("队列为空,没有数据~~~~");
        }
        return arr[front];
    }
}