Natify is an abandoned project, now three years old, made "quick and dirty" and without serious effort.
It translates compiled Java Bytecode to Java-interoperable C Sourcecode, making it harder to modify and read.
The effectiveness of such a translation is of multiplicative nature, proving its benefits only when combined with a Java-level obfuscation beforehand or a binary-level obfuscation (e.g. Tyrmida or VMProtect) afterwards.
The translation is only ~95% correct, so if you are crazy enough to do anything about that, feel free to do so, pain and glory await equally.