As some of you may have noticed, we've recently opened a new repository in the Code Tools project for small utilities which can be used to gather info about the OpenJDK code base and builds. ¹

The latest addition is a utility for analyzing the class file versions in a collection of class files. I've posted an example set of results from analyzing the class files in an OpenJDK build on Linux. ². Most of the files are version 52 files as you would expect, but there is a surprising number of version 51 and 50 files, as well as a handful of v45.3 files as well. Digging deeper, it turns out that Nashorn is still using version 51 class files, and the Serviceability Agent is still using version 50 class files and one 45.3 class file, leaving the remainder of the 45.3 class files coming from RMI.

For more info on the different class file versions, see Joe Darcy's class file version decoder rIng.

Thanks to Stuart Marks for planting the seed for the class file version tool.

1. See the project page, repo, and mail archive.
2. http://cr.openjdk.java.net/~jjg/cfv-summary/open/