Add JDK 6 to the Platform List (if necessary)

It may be necessary to add JDK 6 to the IDE's list of available platforms. To do this, choose Tools Java Platform Manager as shown in the following figure:
Selecting the Java Platform Manager from the Tools Menu
If you don't see JDK 6 (which might appear as 1.6 or 1.6.0) in the list of installed platforms, click "Add Platform", navigate to your JDK 6 install directory, and click "Finish". You should now see this newly added platform:
The Java Platform ManagerTo set this JDK as the default for all projects, you can run the IDE with the --jdkhome switch on the command line, or by entering the path to the JDK in the netbeans_j2sdkhome property of your INSTALLATION_DIRECTORY/etc/netbeans.conf file.
To specify this JDK for the current project only, select Hello World App in the Projects pane, choose File "Hello World App" Properties, click on Libraries, then select JDK 6 under the Java Platform pulldown menu. You should see a screen similar to the following:
The IDE is now configured for JDK 6.