关于java:队列循环队列与非循环队列Java版

import java.awt.Font;
import java.util.Scanner;
import javax.management.RuntimeErrorException;
public class CircleArrayQueueDemo {

public static void main(String[] args) {
    // 创立队列
    CircleArrayQueue circleArrayQueue = new CircleArrayQueue(4);
    char key = ' ';
    Scanner scanner = 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): 增加数据到队列");
        System.out.println("g(get): 从队列取出数据");
        System.out.println("h(head): 查看队列头的数据");
        key = scanner.next().charAt(0);
        switch (key) {
        case 's':
            circleArrayQueue.showQueue();
            break;
        case 'e':
            circleArrayQueue.showQueue();
            break;
        case 'a':
            System.out.println("输出一个数");
            int value = scanner.nextInt();
            circleArrayQueue.addQueue(value);
            break;
        case 'g':
            try {int res = circleArrayQueue.getQueue();
                System.out.printf("取出的数据是 %d\n",res);
            }catch (Exception e) {System.out.println(e.getMessage());
            }
            break;
        case 'h':
            try {int res = circleArrayQueue.headQueue();
                System.out.printf("队列头的数据是 %d\n",res);
            }catch (Exception e) {System.out.println(e.getMessage());
            }
            break;
        default:
            scanner.close();
            loop = false;
            break;
        }
    }
    System.out.println("程序退出");
}

}
// 队列
class CircleArrayQueue{

private int maxsize;
private int front;
private int rear;
private int[] arr;
// 结构器
public CircleArrayQueue(int arrmaxsize) {
    maxsize = arrmaxsize;
    front = 0;
    rear = 0;
    arr = new int[maxsize];
}
// 判满
public boolean isFull() {return (rear+1)%maxsize == front;
}
// 判空
public boolean isEmpty() {return rear == front;}
// 入队
public void addQueue(int n) {if(isFull()) {System.out.println("队列已满，不能再增加！");
        return;
    }
    // 增加数据
    arr[rear] = n;
    //rear[农产品期货](https://www.gendan5.com/cf/af.html) 后移
    rear = (rear + 1) % maxsize;
}
// 出队
public int getQueue() {if(isEmpty()) {throw new RuntimeException("队列为空，不可取出元素！");
    }
    // 取值
    int value = arr[front];
    //front 后移
    front = (front + 1)%maxsize;
    return value;
}
// 遍历
public void showQueue() {if(isEmpty()) {System.out.println("队列为空!");
        return;
    }
    for(int i = front; i < front +  size(); i++) {System.out.printf("arr[%d]=%d\n",i % maxsize, arr[i % maxsize]);
    }
}
// 求队列无效数据的个数
public int size() {return (rear + maxsize - front) % maxsize;
}
// 显示队头元素
public int headQueue() {if(isEmpty()) {throw new RuntimeException("队列为空，不可取出元素！");
    }
    return arr[front];
}

}