This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
You can use a professional obfuscation tool such as Dash-O-Pro which will render any decompiled class pretty much un-readable (apart from to the odd UberGeek or two) but there are drawbacks 1) Very Expensive 2) For every Obfuscator - there is a De-Obfuscator in the pipeline
Its not what you do, its the way you say you've done it.