The default look-and-feel for the NetBeans IDE does not render optimally in newer versions of Gnome (borders do not display on menus). The Nimbus look-and-feel looks nicer. If you’d like to automatically start NetBeans with Nimbus, use the following on the command line:

/bin/sh "/path/to/netbeans/bin/netbeans" --laf Nimbus

Note: NetBeans 8.0+ allows you to specify the look-and-feel in the settings.