题目链接:https://buuoj.cn/challenges#Java%E9%80%86%E5%90%91%E8%A7%A3%E5%AF%86

题目是个.class文件，拖进jd-gui里,看到java源码

是个简单的加密，写个脚本跑一下

key = [ 180, 136, 137, 147, 191, 137, 147, 191, 148, 136, 133, 191, 134, 140, 129, 135, 191, 65 ]
flag = ""
for i in key:
    flag += chr(i - ord("@") ^ 0x20)
print(flag)

flag:This_is_the_flag_!