There is nothing in the
Java Sound API (the classes in javax.sound and subpackages) that supports MP3 files, so you won't find anything there. The Java Sound API does have a pluggable architecture, so that people could add support for file formats such as MP3, so it is possible that someone wrote an MP3 support module, you'd have to search Internet for that.
There is an MP3 plugin for JMF (Java Media Framework, the Java multimedia API):
Java MP3 PlugIn. Ofcourse you need to have JMF installed to be able to use this (JMF is an add-on package, it is not part of the standard Java installation).
Other options:
JLayer mp3info You can find more with Google yourself.