When I tried to run my main in netbeans I got this error
java exception in thread "main" java.lang.UnsupportedClassVersionError
I'm using netbeans 7 (macbook) ..what I tried to google the error and some people said that the Java Runtime is diffrnet than the JDK .. how can I solve this error in mac

Did you download the latest version of JDK?

That usually means you are using an old version of the runtime with a class that was compiled for a later version. Simply download and install the latest Java Runtime (JRE) (execute only) or JDK (build/compile/debug/run - includes the JRE)