数组模拟环形队列

package cn.redis.demo.datastructuresandalgorithms.datastructure;

import java.util.Scanner;

/**
 * 数组模拟环形队列
 *
 * @author hq
 * Created in 2020/8/23 21:44
 */
public class ArrayToQueue {

    public static void main(String[] args) {
        ArrayQueue arrayQueue = new ArrayQueue(3);
        boolean flag = true;
        while (flag) {
            System.out.println("a 添加，g 获取，s查询,exit 退出");
            Scanner scanner = new Scanner(System.in);
            System.out.println("请输入一个字母：");
            String next = scanner.next();
            switch (next) {
                case "a":
                    try {
                        System.out.println("请输入一个数字：");
                        arrayQueue.add(scanner.nextInt());
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    break;
                case "g":
                    try {
                        arrayQueue.get();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    break;
                case "s":
                    try {
                        arrayQueue.show();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    break;
                case "exit":
                    flag = false;
                    break;
            }

        }
    }
}


/**
 * java取模(取余)%运算
 * 莫不尽 取本身
 * 本质是：m % n = m - (int)(m / n) * n
 * 注意：余值结果符号和 m (被模数) 符号有关，m为负数则余值为负数，m为正数则余值为正数
 * 例如：-187 % 100 = -187 - (int)(-187/100) * 100
 * =-187 + 1 * 100
 * =-187 +  100
 * =-87
 * 12 % 5 = 12 - (int)(12 / 5) * 5
 * =12 - 2 * 5
 * =2
 */

//编写一个 arrayQueue类

class ArrayQueue {
    private int maxSize; //表示数组的最大容量
    private int front; //列队头
    private int rear; //列队尾
    private int[] arr; //该数组用于存放数据，模拟列队

    public ArrayQueue(int maxSize) {
        this.maxSize = maxSize;
        arr = new int[this.maxSize];

    }

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

    //判断列队是否为空
    public boolean isEmpty() {
        return rear == front;
    }

    //添加队列
    public void add(int n) throws Exception {
        if (isFull()) {
            throw new Exception("列队已满");
        }
        arr[rear] = n;
        rear = (rear + 1) % maxSize;
    }

    //获取队列中数据
    public int get() throws Exception {
        if (isEmpty()) {
            throw new Exception("队列为空");
        }
        int value = arr[front];
        front = (front + 1) % maxSize;
        return value;
    }

    //显示队列中的所有元素
    public void show() throws Exception {
        if (isEmpty()) {
            throw new Exception("队列为空");
        }
        for (int i : arr) {
            System.out.println(i);
        }
    }
}