I need an OpenSource API in Java, which can encode *.wav and *.au formats to MP3 and vice-versa.
I have evaluated Java Sound API and LameOnJ, but they do not meet m
There may not be an adequate answer for you, yet, as the MP3 format requires the authors of decoder/encoders to obtain a license from the Fraunhofer Institute.
I think the the LAME library is distributed from a country that does not respect these IP issues, but it took a considerably amount of legal hackery to get this far.
For any other libraries - for example one written in Java, the authors need to get a similar license. Where cost is an issue - e.g. in an Open Source project, then this is enough of a disincentive to starting.
For more details see this wikipedia article.
If LAME4J is not stable enough for you, then I'm afraid your options are probably: