参考：https://mp.weixin.qq.com/s/vn3KiV-ez79FmbZ36SX9lg

int[] arr = {1,6,7,8,4,3,5,2};

        for (int i = 0; i < arr.length-1; i++) {
            for (int j = 0; j < arr.length-1-i; j++) {
                 if(arr[j] > arr[j+1]){
                     int temp = arr[j+1];
                     arr[j+1] = arr[j];
                     arr[j] = temp;
                 }

            }
        }