Lucy's Note of Coding

import java.util.Scanner;

public class Test {

  public static void main(String[] args) {

    CircularQueue queue = new CircularQueue(3);
    Scanner scanner = new Scanner(System.in);
    char choice = ' ';
    boolean loop = true;

    while (loop) {
      System.out.println("選擇(s)_show，顯示佇列");
      System.out.println("選擇(a)_add，新增佇列");
      System.out.println("選擇(g)_get，取出佇列的值");
      System.out.println("選擇(h)_head，顯示佇列頭的值");
      System.out.println("選擇(e)_exit，退出程式");
      choice = scanner.next().charAt(0);

      switch (choice) {
        case 's' :
          try {
            queue.showQueue();
          } catch (Exception e) {
            System.out.println(e.getMessage());
          }
          break;
        case 'a' :
          System.out.println("請輸入一個數");
          int value = scanner.nextInt();
          try {
            queue.addQueue(value);
          } catch (Exception e) {
            System.out.println(e.getMessage());
          }
          break;
        case 'g' :
          try {
            int res = queue.getQueue();
            System.out.printf("取出的資料為%d\n", res);
          } catch (Exception e) {
            System.out.println(e.getMessage());
          }
          break;
        case 'h' :
          try {
            int headQueue = queue.getHeadQueue();
            System.out.printf("headQueue = %d\n", headQueue);
          } catch (Exception e) {
            System.out.println(e.getMessage());
          }
          break;
        case 'e' :
          scanner.close();
          loop = false;
          break;
        default :
          break;
      }
    }
  }
}

/**
 * 陣列模擬環形佇列
 */
   class CircularQueue {

    // declare fields
    private int length; // queue length
    private int front; // an index of before head queue
    private int rear; // the end of queue
    private int[] arr; // to store values

    // declare a constructor, aim to new an array
    CircularQueue(int length) {
      this.length = length;
      this.arr = new int[length];
//      this.front = 0;
//      this.rear = 0;
    }

    private boolean isFull() {
      return length == getCircularQueueNum();
    }

    private boolean isEmpty() {
      return front == rear;
    }

    // declare a function for addQueue
    public void addQueue(int value) {
     if(isFull()) {
       throw new ArrayIndexOutOfBoundsException("佇列已滿，不能新增資料");
     }
     // add data
     arr[rear % length] = value;
     rear++;
    }

    public int getQueue() {
      if (isEmpty()) {
        throw new RuntimeException("佇列無資料~~");
      }
      // get data
      int temp = arr[front % length];
      front++;
      return temp;
    }

    public int getHeadQueue() {
      if (isEmpty()) {
        throw new RuntimeException("佇列無資料~~");
      }
      return arr[front % length];
    }

    public void showQueue() {
      if (isEmpty()) {
        throw new RuntimeException("佇列無資料~~");
      }

      for (int i = front; i < front + getCircularQueueNum(); i++) {
        System.out.printf("arr[%d] = %d\n", i % length, arr[i % length]);
      }
    }


    public int getCircularQueueNum() {
      int n; // current number of value in CircularQueue
      if (rear < front) {
        n = rear + length - front;
      } else {
        n = rear - front;
      }
      return n;
    }

  }

如有敘述錯誤，還請不吝嗇留言指教，thanks!