Possible duplicate:Changing the Java Platform Netbeans Runs on
Here is the default JDK image (which is 1.6) and the JDK that I want to install by default (which is 1.7)
http://tinypic.com/view.php?pic=35ldlye&s=5
If I remember correctly, you need to set the netbeans_jdkhome property in the netbeans configuration file. It should be in your etc/netbeans.conf file.
netbeans_jdkhome
etc/netbeans.conf