// 判斷隊(duì)列是否為空
    public boolean isEmpty() {
        return rear == front;
    }

package circle;
import java.util.Scanner;
public class CircleArrayQueue {
    public static void main(String[] args) {
        System.out.println("-----測(cè)試循環(huán)隊(duì)列-----");
        // 創(chuàng)建一個(gè)隊(duì)列
        CircleArray circleArray = new CircleArray(4);
        char key = ' '; //接受用戶(hù)輸入
        Scanner scanner = new Scanner(System.in);
        boolean loop = true;
        // 輸出一個(gè)菜單
        while (loop) {
            System.out.println("s(show): 顯示隊(duì)列");
            System.out.println("e(exit): 退出程序");
            System.out.println("a(add): 添加數(shù)據(jù)到隊(duì)列");
            System.out.println("g(get): 從隊(duì)列取出數(shù)據(jù)");
            System.out.println("h(head): 顯示隊(duì)首的數(shù)據(jù)");
            key = scanner.next().charAt(0); // 接收一個(gè)字符
            switch (key) {
                case 's':
                    circleArray.showQueue();
                    break;
                case 'a':
                    System.out.println("請(qǐng)要添加的數(shù)");
                    int value = scanner.nextInt();
                    circleArray.addQueue(value);
                    break;
                case 'g':
                    try {
                        int res = circleArray.getQueue();
                        System.out.printf("取出的數(shù)據(jù)是：%d", res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h':
                    try {
                        int headValue = circleArray.showHeadQueue();
                        System.out.printf("隊(duì)首數(shù)據(jù)是：%d", headValue);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e':
                    scanner.close();
                    loop = false;
                    break;
            }
        }
        System.out.println("退出程序");
    }
}
class CircleArray {
    //表示數(shù)組最大容量
    private int maxSize;
    // 隊(duì)列頭，由之前調(diào)整為指向隊(duì)列第一個(gè)元素
    private int front;
    // 隊(duì)列尾，由之前調(diào)整為指向隊(duì)列最后一個(gè)元素的后一個(gè)位置，為了空出一個(gè)元素位置
    private int rear;
    // 用于存放數(shù)據(jù)的數(shù)組
    private int[] arr;
    // 構(gòu)造器
    public CircleArray(int arrMaxSize) {
        maxSize = arrMaxSize;
        arr = new int[maxSize];
        front = 0;
        rear = 0;
    }
    // 判斷隊(duì)列是否已經(jīng)存滿(mǎn)
    public boolean isFull() {
        return (rear + 1) % maxSize == front;
    }
    // 判斷隊(duì)列是否為空
    public boolean isEmpty() {
        return rear == front;
    }
    // 添加數(shù)據(jù)到隊(duì)列
    public void addQueue(int num) {
        // 判斷隊(duì)列是否滿(mǎn)了
        if (isFull()) {
            System.out.println("隊(duì)列已滿(mǎn)，不可加入數(shù)據(jù)");
            return;
        }
        arr[rear] = num;
        // 將rear后移，要考慮取模
        rear = (rear + 1) % maxSize;
    }
    // 拿出隊(duì)列數(shù)據(jù)
    public int getQueue() {
        // 判斷隊(duì)列是否空
        if (isEmpty()) {
            // 拋出異常
            throw new RuntimeException("隊(duì)列為空，不可取數(shù)據(jù)");
        }
        int tempValue = arr[front];
        front = (front + 1) % maxSize; //也要考慮取模，防止front不停的增加，導(dǎo)致越界
        return tempValue;
    }
    // 顯示隊(duì)列所有數(shù)據(jù)
    public void showQueue() {
        // 遍歷
        if (isEmpty()) {
            System.out.println("隊(duì)列為空");
            return;
        }
        // 從front開(kāi)始遍歷，遍歷多少個(gè)實(shí)際存的元素即可
        for (int i = front; i < front + CircleQueueSize(); i++) {
            System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);
        }
    }
    // 求出當(dāng)前隊(duì)列有效數(shù)據(jù)的個(gè)數(shù)
    public int CircleQueueSize() {
        return (rear - front + maxSize) % maxSize;
    }
    // 顯示隊(duì)里的隊(duì)首數(shù)據(jù)
    public int showHeadQueue() {
        if (isEmpty()) {
            // 拋出異常
            throw new RuntimeException("隊(duì)列為空，不可取數(shù)據(jù)");
        }
        return arr[front];
    }
}