java.lang.UnsupportedClassVersionError: : Unsupported major.minor version 51.0
Root cause:
Project/Program would have compiled in some version and trying to run in some different version of jdk.
Possible Solutions:
In Eclipse, right click on the project Properties -> Java Compilers
and change the compiler compliance level to 1.5/1.6/1.7 and try.
Please comment if you found any other solutions for the same problem.