Is there an easy way to put music in a java applet? Preferably streaming so that it doesn't need to be preloaded.
You might try something like this, though as the author said he didn't stream so it stuttered. You'd want to preload a certain amount of the sound before feeding it to the Line.
This site may help you, it contains a lot of examples of how to use the Java sound API (loading, playing, streaming, recording...).