My smack application server for GCM gives me this error "Exception in thread "main" java.lang.UnsupportedClassVersionError: org/jivesoftware/smack/XMPPException : Unsupported major.minor version 51.0"

I am trying to implement an application server with ccs/xmpp connection for google cloud messaging enabled android app by following this android tutorial on android developers site GCM Cloud Connection Server (XMPP) | Android Developers , but unfortunately when I am trying to run my desktop application, this error is showing. I don’t know what is the cause of this error “Exception in thread “main” java.lang.UnsupportedClassVersionError: org/jivesoftware/smack/XMPPException : Unsupported major.minor version 51.0”. Please help me to solve this. Thanks. Note: I am using smack 4.0.6

A google search for “Unsupported major.minor version 51.0” yields: java - Unsupported major.minor version 51.0 - Stack Overflow. You need at least Java 7 to run Smack 4.

thank you very much, I already solve it.