These two packages have all relevant classes that will assist you to write a program to convert sound formats.
While that's true in general, I don't think it helps here because neither WMA nor MP3 are supported by javax.sound. MP3 capabilities can be added as described here. Not sure about WMA, though. File formats that that are used almost exclusively on Windows tend to be not well supported in the Java world.
Also, both MP3 and WMA are sampled formats, so the javax.sound.midi package will not be involved.