jarscan is a command line tool that scans archives for a certain entry. It scans recursively in subdirectories and also archives in archives. You can also use jarscan to search for file content, for the compiler version of .class files or for doubled classes. It is designed to be also used as a library.
Documentation of all features you will find at the Tutorial.
If you miss features or you found a bug feel free to create an issue at JIRA.
If you want to join our project read the Info_for_developers.
19.11.2011 After all the trouble we had, moving to kenai.com and back to java.net we are online again now with a new release. jarscan 2.2 has a new feature for Java developers. With the -j option every "." is converted to "/" in the searchString. So if you have a ClassNotFoundException you can just copy the path to the console.