Is there any way to tell NetBeans to execute a specific action when saving a file? e.g. removing unused imports while saving a source file?
A:
This was an interesting question... as I believe you would have to write a custom NetBeans plugin to do what you're wanting (the functionality isn't available out-of-the-box), and I've been looking for an excuse to explore NetBeans plugin development.
However, after spending a couple of hours reading tutorials and crawling through the javadocs... it's become clear that this subject is quite a big bite to chew, and probably way more involved than you're wanting.
I think the BEST suggestion is forget about removing unused imports at save-time, and instead perform this step at build-time. NetBeans offers great integration with Ant and/or Maven (for build purposes it's basically just a GUI wrapper around those tools), and there are a number of Ant tasks out there that can do what you're wanting. See:
http://ant.apache.org/external.html
(look for the "CleanImports" and "Importscrubber" tasks)
If your NetBeans project(s) are Maven-based, then you can always plug in one of these Ant tasks there using the AntRun plugin for Maven.
If you're not used to dealing with Ant or Maven directly in NetBeans, then just switch to the "Files" tab and look at your project's root directory. If its a Maven project, the build script will be named pom.xml. Otherwise, your project will generally be Ant-based and the build script will be named build.xml. The documentation for these items above should make it fairly clear how to move forward from there.
I notice that those two Ant tasks haven't been updated in awhile, so if you run into issues you might want to check out the very popular and up-to-date PMD system, which has its own documentation for integrating with NetBeans. However, the issue there is PMD is primarily for generating reports... I don't know if it can be used to actually take action and change source files.
Steve Perkins
2010-10-01 17:00:48