How can I build a jar for a previous Java version?

Question

I am trying to compile my code and run it on a different server. The problem is my JRE version is Java version "1.6.0_13" and that on the server is Java version "1.4.2".

This gives me "unrecognized class file version" exception when I try to run the jar on the server. I cannot compile my code on the server because of various dependencies I will have to set up.

So I need to know if there is a way to "use Eclipse" [this is easier than command line since it takes care of dependencies] and compile my stuff using 1.4.2 instead 1.6.0_13. Do I have to uninstall my JRE from my machine, then reinstall previous version and then compile or is there an elegant and cleaner way?

Answer 1

Eclipse Mars (4.5.1)

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Change JDK compliance

Window > Preferences > Java > Compiler > JDK Compliance > change Compiler compliance level:

If you want to change other details, you can uncheck "Use default compliance settings".

Press OK and in the "Compiler Settings Changed" window choose:

• Yes if you want to build all projects from the workspace:

  

• No if you want to build only one/some project(s) later

  • Select the project (click on the left side - E.g.: in the Package Explorer) > Project > Build Project

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Export jar

Right click on the project (from the left side - E.g.: in the Package Explorer) > Export... > type "jar" to filter the options you have > choose what you want (probably JAR file or Runnable JAR file) > Next > add the details > Finish