Java Programming

I have a question about protecting the source code contained of a jar File. Does compressing the source (thats what the option is called in eclipse) when creating a jar help protect all source code, or is it still vunrable to quick and easy decompilation?

If the answer to the first question is yes, then what good java obfuscators exist? I did some googling and http://www.e-t.com/jshrink.html seemed to be a great choice, but i never used it so i am not sure, and would like to hear some comments from the knoledgabe people on this website. Thanks.