A simple way in Jcreator is to add a bat file as external tool:
configure->option->tools->new->program than add a bat file like this:
makeJar.bat1 2 3 4 5
| pushd cd classes jar cf output.jar * popd pause |
once you have done it, simply add this external tools to your toolbar:
right click on
toolbar->customise select categorie "Tools" drag first tools icon to your toolbar.
you may also use/customise this tools
http://www.java-gaming.org/forums/index.php?topic=17584.0 to make exacly what you want as for example read filename from a txt file as requiered by your first post.