[ubuntu] Java driving me crazy!

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http://ubuntuforums.org – Hello gentlemen I am having an issue with Java and have been for days now. I am trying to run a .jar program (obviously) and nothing happends. However when I run java -jar jarfile.jar I get this print out. UnsupportedClassVersionError: project1/MainProject : Unsupported major.minor version 51.0. I have tried uninstalling openJDK6 and reinstalling. I have tried installing openJDK7 with and without JDK6. I have tried oasisJAVA 7u5. Nothing has worked for me so far. Thank you for the future efforts. (Hardware)