Java基础之数组模拟循环队列

package com.ArrayQueue;

import java.util.Scanner;

public class CircleArrayQueueDemo {
    public static void main(String args[]){
        int maxSize = 4;
        CircleArrayQueue queue = new CircleArrayQueue(maxSize);
        Scanner scanner = new Scanner(System.in);
        char key;
        boolean loop = true;
        while (loop) {
            //根据输入的不同字母，进行对应的操作
            System.out.println("a(add):添加一个数据");
            System.out.println("g(get):取出一个数据");
            System.out.println("h(head):展示头部数据");
            System.out.println("s(show):展示所有数据");
            System.out.println("q(quit):退出程序");
            //因为判满条件的缘故，队列的最大容量实为maxSize-1
            System.out.printf("(队列的最大容量为：%d)\n",maxSize-1);
            key = scanner.next().charAt(0);//接收一个字符
            try {
                switch (key) {
                    case 'a':
                        System.out.println("请输入一个数：");
                        int value = scanner.nextInt();
                        queue.addQueue(value);
                        System.out.println("数据添加成功。");
                        break;
                    case 'g':
                        System.out.printf("取出的数据为：%d\n", queue.getQueue());
                        break;
                    case 'h':
                        queue.headQueue();
                        break;
                    case 's':
                        queue.showQueue();
                        break;
                    case 'q':
                        scanner.close();
                        loop = false;
                        System.out.println("程序已退出。");
                        break;
                    default:
                        break;
                }
            } catch (RuntimeException e) {
                System.out.println(e.getMessage());
            }
        }
    }
}

class CircleArrayQueue{
    private int maxSize;
    private int front;//指向头元素所在位置
    private int rear;//指向尾元素所在位置的下一个位置
    private int arr[];//存放数据的数组

    //构造器，传入数组最大容量值
    public CircleArrayQueue(int size){
        maxSize = size;
        front = 0;
        rear = 0;
        //虽然数组最大容量为maxSize，但实际用于存储的只有maxSize-1
        arr = new int[maxSize];
    }
    //判空条件：front == rear
    public boolean isEmpty(){
        return front == rear;
    }
    //判满条件：(rear+1)%maxSize == front
    public boolean isFull(){
        return (rear+1)%maxSize == front;
    }
    //添加数据，入队
    public void addQueue(int n){
        //判满
        checkFull();
        arr[rear] = n;
        rear = (rear+1)%maxSize;
    }
    //取出数据，出队
    public int getQueue(){
        //判空
        checkEmpty();
        int value = arr[front];
        front = (front+1)%maxSize;
        return value;
    }
    //队列中的有效值个数
    public int size(){
        return (rear-front+maxSize)%maxSize;
    }
    //展示队列的所有数据
    public void showQueue(){
        //判空
        checkEmpty();
        for(int i=front;i<front+size();i++){
            System.out.printf("arr[%d]=%d\n",i%maxSize,arr[i%maxSize]);
        }
        System.out.printf("当前front=%d,rear=%d\n",front,rear);
    }
    //展示位于队列头部的元素值，不改变front的指向
    public void headQueue(){
        //判空
        checkEmpty();
        System.out.printf("头部数据是：%d\n",arr[front]);
    }
    //检测出队列为空时，打印当前front，rear的值，抛出异常
    public void checkEmpty(){
        if (isEmpty()) {
            System.out.printf("当前front=%d,rear=%d\n",front,rear);
            throw new RuntimeException("队列为空,不能取数据");
        }
    }
    //检测出队列满时，打印当前front，rear的值，抛出异常
    public void checkFull(){
        if(isFull()){
            System.out.printf("当前front=%d,rear=%d\n",front,rear);
            throw new RuntimeException("队列已满，不能添加数据");
        }
    }
}