upgrading to next jdk version

[trupti nigam]

My module is running fine with jdk 1.3 version in production, but few people want, all the modules to be upgraded to jdk version 1.6. Obviuously we will be testing it against this version before deploying to prod, but I would like to know why would we go for new version when we do not see any new issues with the modules deployed in prod with old jdk version.

[Mazer Lao Tzu]

Well, version 1.3 has passed its End of Life a while ago. Although old versions of java don't seem to become unstable on newer systems and upgraded environments, this does typically mean that you won't be able to get bug-fixes (via newer versions) for whatever libraries your code is using. Some of the development tools out there have started depending on newer syntax and JVM supported functionality. Although I generally prefer to stay up-to-date with software, the only pressing concerns I would have is if you are doing new development in the module.
There are some performance and scalability reasons to upgrade to version 1.6 which may or may not be all too important for your module.

[Campbell Ritchie]

If I remember correctly, you may have problems if you have used words like assert and enum as identifiers, because they are keywords in Java6. You may also get confusion if there is anywhere that your code might be interpreted as using boxing and unboxing.

But those are all problems for the compiler. I think that old .class files which have already been compiled can remain unchanged, as long as you don't attempt to edit or re-compile them.