What version of javac built my jar?

Question

How can I tell what version of the Java compiler was used to build a jar? I have a jar file, and it could have been built in any one of three JDKs. We need to know exactly

Answer 1

Here is Java's way to find this information.

Windows: javap -v | findstr major
Unix: javap -v | grep major

For example:
> javap -v Application | findstr major   major version: 51