Building from source in Netbeans results in major minor version error

Hello, I have already downloaded JDK 8 and told NetBeans to compile with it. Everything compiles fine with no errors. But when I replace the original .jar lib with the resultant lib and try to run spark, I get the major minor version error. I know what this error typically means but I can't fiugre out why I'm getting it. Any help is appreciated.