I am developing a security software and want to obfuscate my java code so it will become impossible to reverse engineer. What is the most reliable java obfuscator ?
First, you really need to keep in mind that it's never impossible to reverse-engineer something. Everything is hackable. A smart developer using a smart IDE can already get far enough.
Well, you can find here a list. ProGuard is pretty good. I've used it myself, but only to "minify" Java code.