class ArrayQueue {
	private int maxSize; // 數(shù)組的最大容量
	private int front; // 隊(duì)列頭
	private int rear; // 隊(duì)列尾
	private int[] arr; // 存放數(shù)據(jù), 模擬隊(duì)列
 
	// 創(chuàng)建構(gòu)造器，初始化
	public ArrayQueue(int arrMaxSize) {
		maxSize = arrMaxSize;
		arr = new int[maxSize];
		front = -1; // front 是指向隊(duì)列頭的前一個(gè)位置
		rear = -1;  // rear  是指向隊(duì)列尾的數(shù)據(jù)(最后一個(gè)數(shù)據(jù))
	}
 
	// 判斷隊(duì)列是否已滿
	public boolean isFull() {
		return rear == maxSize - 1;
	}
 
	// 判斷隊(duì)列是否為空
	public boolean isEmpty() {
		return rear == front;
	}
 
	// 添加數(shù)據(jù)
	public void addQueue(int n) {
		if (isFull()) {
			System.out.println("隊(duì)列已滿，不能再添加數(shù)據(jù)了！");
			return;
		}
		rear++; // 讓rear 后移
		arr[rear] = n;
	}
 
	// 獲取數(shù)據(jù)
	public int getQueue() {
		if (isEmpty()) {
			// 通過拋出異常
			throw new RuntimeException("隊(duì)列為空，無(wú)數(shù)據(jù)可取！");
		}
		front++; // front后移
		return arr[front];
 
	}
 
	// 顯示隊(duì)列的所有數(shù)據(jù)
	public void showQueue() {
        if (isEmpty()) {
			System.out.println("隊(duì)列空的，沒有數(shù)據(jù)~~");
			return;
		}
		for (int i = 0; i < arr.length; i++) {
			System.out.printf("arr[%d]=%d\n", i, arr[i]);
		}
	}
 
	// 顯示隊(duì)列的頭部指向的下一個(gè)
	public int headQueue() {
		if (isEmpty()) {
			throw new RuntimeException("隊(duì)列為空，沒有數(shù)據(jù)~~");
		}
		return arr[front + 1];
	}
}

		//創(chuàng)建一個(gè)隊(duì)列
		ArrayQueue queue = new ArrayQueue(3);
		char key = ' '; 
		Scanner scanner = new Scanner(System.in);//
		boolean loop = true;
		//輸出一個(gè)菜單選項(xiàng)
		while(loop) {
			System.out.println("s(show): 顯示隊(duì)列");
			System.out.println("e(exit): 退出程序");
			System.out.println("a(add): 添加數(shù)據(jù)到隊(duì)列");
			System.out.println("g(get): 從隊(duì)列取出數(shù)據(jù)");
			System.out.println("h(head): 查看隊(duì)列頭的數(shù)據(jù)");
			key = scanner.next().charAt(0);//接收一個(gè)字符
			switch (key) {
			case 's': //顯示隊(duì)列所有數(shù)據(jù)
				queue.showQueue();
				break;
			case 'a': //添加數(shù)據(jù)
				System.out.println("輸出一個(gè)數(shù)");
				int value = scanner.nextInt();
				queue.addQueue(value);
				break;
			case 'g': //依次取出數(shù)據(jù)
				try {
					int res = queue.getQueue();
					System.out.printf("取出的數(shù)據(jù)是%d\n", res);
				} catch (Exception e) {
					// TODO: handle exception
					System.out.println(e.getMessage());
				}
				break;
			case 'h': //查看隊(duì)列頭指向
				try {
					int res = queue.headQueue();
					System.out.printf("隊(duì)列頭的數(shù)據(jù)是%d\n", res);
				} catch (Exception e) {
					// TODO: handle exception
					System.out.println(e.getMessage());
				}
				break;
			case 'e': //退出程序
				scanner.close();
				loop = false;
				break;
			default:
				break;
			}
		}
		
		System.out.println("程序退出~~");
	}