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

On Windows do the following:

1. Unzip or extract the JAR file using WinZip / Java JAR command.
2. Drag and Drop one of the class files into your Eclipse Java project.
3. Open the class file.

Now Eclipse will show the exact major and minor version.