I'm using Netbeans IDE on tiny screen of my laptop, so I don't want to waste space for its titlebar. Is there any option in menus or command line that can remove it?
One option (and most probably the only option) is to put NB into full screen mode. To do this you can use the View > Full Screen menu item (Alt + Shift + Enter).
Note that I'm running on Windows and I can't really say what Gnome will do with this.