As per most IDE's they can be a bit memory intensive.

An alternate IDE to use that is not as memory intensive is eclipse. I only recommend netbeans as it is slightly easier to use especially if you want to make a GUI (graphical user interface) for your application.

Eclipse is less memory intensive and is my preffered IDE to use but it will be a lot more complicated to use for first time coders.

But if you find netbeans keeps locking then install the latest Eclispe version and use that instead.