LAMEOnJ is a 100% Java library mapping in Java the complete C API of LAME, the popular MP3 encoder and decoder. The Java-native impedance is solved with JNIEasy, JNIEasy is free for non profit uses (there is an alternative commercial license).
Version 1.2 adds a new Object Oriented API for decoding MP3 data to PCM/WAV using LAME under the hood.
The decoding API was ever present in LAMEOnJ since version 1.0 because the LAME API is fully wrapped. But this low level API is tricky, the OOP version simplifies how to decode chunks of MP3 data to WAV/PCM (of course the typical one call method is provided too).
LAMEOnJ runs on the same x86 platforms supported by JNIEasy: Windows, Linux, Mac OS X and Solaris.
The distribution does not include LAME binaries. Windows versions are easy to find, in Unixes compiling LAME from source code is easy (anyway contact with me if you don't know).
LAMEOnJ is open source LGPL licensed and hosted on SourceForge.net