Tool to read and display Java .class versions

Use the javap tool that comes with the JDK. The -verbose option will print the version number of the class file.

> javap -verbose MyClass
Compiled from "MyClass.java"
public class MyClass
  SourceFile: "MyClass.java"
  minor version: 0
  major version: 46
...

To only show the version:

WINDOWS> javap -verbose MyClass | find "version"
LINUX  > javap -verbose MyClass | grep version