### TL;DR
* Rename the spaces.
* Fix the signature.
* Decrypt the string constants.
* Recover the function name of InvokeDynamic
* Recover the integer constants.
* Read the bytecode, the bytecode, and the bytecodes.
* Decrypt the flag

Original writeup (https://github.com/sasdf/ctf-tasks-writeup/blob/master/writeup/2018/HackIT/coffee_overflow/README.md).