I'm sure I'm the last Mac Java developer here to figure this out so I'm posting it not so much for you but for future generations intrepid googlers to find.
Netbeans is a great IDE and I'm really starting to warm up to it (starting to warm up to IDEs in general, actually). One of my big complaints so far has been the lack of Javadocs in the code completion popup window. Since I had some extra time today I thought I'd finally figure it out.
The reason Netbeans doesn't have javadoc code completion on the Mac, but does on other operating systems, is that Apple doesn't ship the
src.jar by default. This is the jar which contains the source code to Java (at least the public APIs, go to the jdk project for the rest), and more importantly: all of the Javadocs. No
src.jar, no javadocs. So the simple remedy is to install them. Here's how you do it: