I wrote ferris-magic-number because I needed to know what version of Java was used to compile all of the .class files in a directory.

Update Main.java to point to a directory on your file system that contains a bunch of .class files. When executed, the application will walk the entire directory tree and determine the Java version used to compile every .class file it encounters. The application then generates two reports.

1. A summary report shows a count of .class files for each Java version found.
2. A detailed report lists every .class file for each Java version found.

See https://mjremijan.blogspot.com/2020/02/discovering-magic-version-number-of.html for more details.

Use this project in combination with https://github.com/mjremijan/ferris-war-exploder to get a directory full of .class files.