数组模拟队列

package com.xkp.data.datasructure.queue;


import java.util.ArrayList;
import java.util.Scanner;

/**
 * author: xkp
 */
public class ArrayQueueDemo {

  //队列 初始化 头部front 为-1 ，尾部rear 为-1 ，新增时front 不变，rear增加，取数据时候rear不变 front增加
    //缺点 放满的数据取出来后再放报错
    /**
     * 头部
     */
    private  int front;

    private  int rear;

    private int maxSize;

    private int[] arr ;


    public ArrayQueueDemo( int arrMaxSize) {
        maxSize=arrMaxSize;
        //指向队列第一个数据的前一个位子
        this.front = -1;
        //指向队列最后股一个位置
        this.rear = -1;
        arr=new int[maxSize];
    }
    //队列是否为空
    public boolean isEmpty(){
        //队列为空的时候 front==rear
        return  front==rear;
    }
    //队列是否已满
    public boolean isFull(){
        return  rear==maxSize-1;
    }

    public  void addQueue(int n){
        if (isFull()){
            System.out.println("队列已满");
            return;
        }
        rear++;
        arr[rear]=n;
    }

    public int getQueue(){
        //判断队列是否为空
        if(isEmpty()){
            throw new RuntimeException("队列为空");
        }
        front++;
        return arr[front];
    }

    public  void showQueue(){
        if(isEmpty()){
            System.out.println("队列为空");
            return;
        }
        for (int i = 0; i <arr.length; i++) {
            System.out.printf("arr[%d]=%d\n",i,arr[i]);
        }
    }


    //显示队列头部数据
    public int peekQueue(){
        if(isEmpty()){
            throw  new RuntimeException("数据为空");
        }
        return  arr[front+1];

    }

    public static void main(String[] args) {
        ArrayQueueDemo arrayQueueDemo=new ArrayQueueDemo(3);
        char key=' ';
        Scanner scanner=new Scanner(System.in);
        boolean flag=true;
        while (flag){
            System.out.println("s(show): 显示队列");
            System.out.println("e(exit): 退出程序");
            System.out.println("a(add): 添加数字");
            System.out.println("g(get): 获取队列值");
            System.out.println("p(peek): 查看队列头数据");
            key=scanner.next().charAt(0);
            switch (key){
                case 's':
                    arrayQueueDemo.showQueue();
                    break;
                case 'e':
                  scanner.close();
                    return;

                case 'a':
                    try {
                        System.out.println("请输入一个数");
                        int value = scanner.nextInt();
                        arrayQueueDemo.addQueue(value);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;

                case 'g':
                    try {
                        int res = arrayQueueDemo.getQueue();
                        System.out.println("获取到的数据"+res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }

                    break;
                case 'p':
                    try {
                        int res =  arrayQueueDemo.peekQueue();
                        System.out.println("获取的头部数据"+ res);
                    } catch (Exception e) {
                        System.out.println(e.getMessage());
                    }
                    break;

            }


        }
    }
}