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copied!<p>I guess that "remove them one by one and check if the application still compiles and works" is not the expected answer :)</p> <hr> <p>(EDIT: While the approach suggested above can be a bit automated, it remains somehow painfull and there must be an alternative, at least for compile-time dependencies. After some googling, I found <a href="http://www.kirkk.com/main/Main/JarAnalyzer" rel="nofollow noreferrer">Jar Analyzer</a> which seems to be a nice tool for this work as explained in this <a href="http://tfnico.blogspot.com/2009/04/reason-2-clean-up-your-jar-files.html" rel="nofollow noreferrer">blog post</a>:</p> <blockquote> <p>Jar Analyzer scans for compile dependencies, meaning that it can create a tree of which JAR-files are needed to compile which JAR-files that are needed to compile these JAR-files, and so on. You get a very nice report/graph which shows you all the JAR-files and why they are in there.</p> <p>You can also see the JAR-files that don't have any connection to your code, remove them and their children. What I found in our libs folder was that about 20% of the 150 JAR files in our libs folder were unused at compile time, and these were potential JARs to be removed.</p> <p><strong>The big aber is that you don't get any hint on which JAR-files are used only at runtime by means of discovery and reflection. And this is where the real work begins.</strong></p> <p>The only way to find out whether a JAR file is used at runtime is basically to take it out, start up your application and test every functionality. If you have an application of moderate size, performing a 100% regression test takes many hours. So in practice, I ended up doing alot of guessing, quick and dirty testing, and asking around to find out which of the runtime dependencies were actually in use.</p> </blockquote> <p>It seems pretty easy to use: download, unzip and run the tool on a directory containing all jars. Or use the provided Ant task.)</p>

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