One of the top-rated java code obfuscator on the market is that available from Zelix Klassmaster. You can get familiar with its many impressive features through downloading a demo version for 30 days. Be aware however, that the evaluation version will flow obfuscate only one or two methods in each class. Should you decide to purchase, it can be done through a license agreement on a per machine or site basis. Their pricing structure is geared towards small developers and discounts are available based on the number of  sites and machines per license. For more details you can go to zelix.com