Question

Can I inspect java code and determine what runtime it will be able to run on? For instance I want to make sure all applications in our environment are using Sun SE6 and JDK 1.6.

Answer 1

When you run the “javap -verbose” on any class, you will get a major and a minor version numbers. Following is a mapping between major+minor to an actual java jre version.

major  minor Java platform version 
45       3           1.0
45       3           1.1
46       0           1.2
47       0           1.3
48       0           1.4
49       0           1.5
50       0           1.6

If you want to programatically get the class version, you can follow this link:
Java API to find out the JDK version a class file is compiled for?