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package com.example;

import java.util.Arrays;
import java.util.Scanner;

/**
 * @Author Gao Xiaozhuang
 * @Date 2020/7/27  18:40
 * @WARN 要写注释
 * @Version 1.0
 * @Description
 */
public class ArrayQueueDemo {
    public static void main(String[] args) {
        ArrayQueue arrayQueue = new ArrayQueue(3);
        char key = ' ';
        Scanner sc = new Scanner(System.in);
        boolean loop = true;
        while (loop) {
            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");
            System.out.println("g(get):从队列取出数据");
            System.out.println("h(head):查看队列头数据");
            key = sc.next().charAt(0);
            switch (key) {
                case 's':
                    arrayQueue.showQueue();
                    break;
                case 'a':
                    System.out.println("请输入：");
                    int value = sc.nextInt();
                    arrayQueue.addQueue(value);
                    break;
                case 'g':
                    try {
                        System.out.println("取出的数据是：" + arrayQueue.getQueue());
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h':
                    try {
                        System.out.println("取出的数据是：" + arrayQueue.headQueue());
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e':
                    loop = false;
                    break;
                default:
                    break;
            }
        }
        System.out.println("程序退出");

    }
}

/**
 * 使用数组模拟队列
 */

class ArrayQueue {
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;

    /**
     * 创建队列构造器
     */
    public ArrayQueue(int arrMaxSize) {
        maxSize = arrMaxSize;
        arr = new int[maxSize];
        front = -1;
        rear = -1;
    }

    public boolean isFull() {
        return rear == maxSize - 1;
    }

    public boolean isEmpty() {
        return rear == front;
    }

    public void addQueue(int n) {
        if (isFull()) {
            System.out.println("队列满，不可加入");
            return;
        }
        rear++;
        arr[rear] = n;
    }

    public int getQueue() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空，不能取数据");
        }
        front++;
        return arr[front];
    }

    public void showQueue() {
        if (isEmpty()) {
            System.out.println("队列为空，不可遍历");
        }
        System.out.println(Arrays.toString(arr));
    }

    public int headQueue() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空，没有队头");
        }
        return arr[front + 1];
    }
}

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package com.example;

import java.util.Arrays;
import java.util.Scanner;

/**
 * @Author Gao Xiaozhuang
 * @Date 2020/7/27  19:27
 * @WARN 要写注释
 * @Version 1.0
 * @Description环形队列 思路：
 * 1.front变量的含义做一个调整：front就指向队列的第一个元素，也就是arr[front]就是队列的第一个元素
 * front初始值为 0  rear初始值为 0
 * 2.rear变量的含义做一个调整：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
 * 3.当队列满时，条件是(rear+1)%maxSize=front
 * 4.当队列空时，rear=front
 * 5.队列中有效的数据的个数为  (rear+maxSize-front)%maxSize
 */
public class CircleQueueDemo {
    public static void main(String[] args) {
       CircleArrayQueue circleArrayQueue = new CircleArrayQueue(4);
        char key = ' ';
        Scanner sc = new Scanner(System.in);
        boolean loop = true;
        while (loop) {
            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");
            System.out.println("g(get):从队列取出数据");
            System.out.println("h(head):查看队列头数据");
            key = sc.next().charAt(0);
            switch (key) {
                case 's':
                    circleArrayQueue.showQueue();
                    break;
                case 'a':
                    System.out.println("请输入：");
                    int value = sc.nextInt();
                    circleArrayQueue.addQueue(value);
                    break;
                case 'g':
                    try {
                        System.out.println("取出的数据是：" + circleArrayQueue.getQueue());
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'h':
                    try {
                        System.out.println("取出的数据是：" + circleArrayQueue.headQueue());
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;
                case 'e':
                    loop = false;
                    break;
                default:
                    break;
            }
        }
        System.out.println("程序退出");

    }
}

class CircleArrayQueue {
    private int maxSize;
    private int front;
    private int rear;
    private int[] arr;

    /**
     * 创建队列构造器
     */
    public CircleArrayQueue(int arrMaxSize) {
        maxSize = arrMaxSize;
        arr = new int[maxSize];
    }

    public boolean isFull() {
        return (rear + 1) % maxSize == front;
    }

    public boolean isEmpty() {
        return rear == front;
    }

    public void addQueue(int n) {
        if (isFull()) {
            System.out.println("队列满，不可加入");
            return;
        }
        arr[rear] = n;
        rear = (rear + 1) % maxSize;
    }

    public int getQueue() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空，不能取数据");
        }
        int value = arr[front];
        front = (front + 1) % maxSize;
        return value;
    }

    public void showQueue() {
        if (isEmpty()) {
            System.out.println("队列为空，不可遍历");
        }
        for (int i = front; i < front + size(); i++) {
            System.out.printf("arr[%d]=%dn", i % maxSize, arr[i % maxSize]);
        }
    }

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

    public int headQueue() {
        if (isEmpty()) {
            throw new RuntimeException("队列为空，没有队头");
        }
        return arr[front];
    }
}