为什么在找不到指定元素后，控制台什么都不输出

Question

public static void main(String[] args) {
        int[] arr = new int[]{1, 2, 3, 4, 8, 46, 54, 59, 72, 77, 85, 91, 100};
        int res = 80;
        int head = 0;//初始的首索引
        int end = arr.length - 1;//初始的尾索引
        boolean isFlag = true;//找没找到的标识符
        while (head <= end) {
            int middle = (end - head) / 2;
            if (res == arr[middle]) {
                System.out.println("找到了，需查找的数值位置为" + middle);
                isFlag = false;
                break;
            } else if (arr[middle] > res  ) {
                end = middle - 1;
            } else {
                head = middle + 1;
            }
        }
        if(isFlag){
            System.out.println("很遗憾没有找到！");
        }

    }

Answer 1

middle计算、要保证是数据源的中间值
我稍微改了一下代码、自己体会

int[] arr = new int[]{1, 2, 3, 4, 8, 46, 54, 59, 72, 77, 85, 91, 100};
int res = 80;
int head = 0;//初始的首索引
int end = arr.length - 1;//初始的尾索引
boolean isFlag = true;//找没找到的标识符
int middle = 0;
while (head <= end) {
  middle = middle+(end - head) / 2;
  if (res == arr[middle]) {
    System.out.println("找到了，需查找的数值位置为" + middle);
    isFlag = false;
    break;
  } else if (arr[middle] > res  ) {
    end = middle - 1;
  } else {
    head = middle + 1;
  }
}
if(isFlag){
  System.out.println("很遗憾没有找到！");
}