Add file to ZIP in Java program

Hi all,
I already found a lot of documentations of how to ZIP files in Java with the java.util.zip package, like: http://java.sun.com/developer/technicalArticles/Programming/compression/
This algorithm works fine when you always want to create a fresh ZIP file where put your current files in.
But I have the following problem: I already have a ZIP file with lots of files in it, and I want to add another file to this ZIP! Unfortunately I did not find any solution of how to do this in a java program - any ideas? Is it possible at all?
Thanks for all answers
nocomm

Maybe this will help.
http://home.mindspring.com/~thornton.rose/articles/ZipJar/part2.html
At the bottom of this link is a algorithm for updating a file in a JAR that can be used for ZIP.
It looks to me that the only way to add a new file to a ZIP is to:
1) Create a Temporary ZIP
2) Add new file to ZIP
3) Open old Zip
4) Read each ZIP Entry in turn and write to temporary ZIP
5) If all goes well then deleted old ZIP and rename temporary ZIP to the correct filename
You will have a ZIP with all the old files in and the new file.

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