What is the application called "Momentics"? It occupies 4.2 GB of my hard disk. Can I delete it? I think it may come from eclipse for java programming. But I don't use java programming anymore. Can I delete "Momentics" and reinstall it if I need it?
Momentics is a QNX product designed for developing apps for Blackberry devices. If you don't use this software you'd be fine to delete or uninstall this application. It's not apart of the operating system and obviously has no use to you.

Everyone who has commented, especially @user3439894 has essential said the same thing. Can confirm for professional experience as both an Apple Certified Tech and a Software Engineer that this software is not necessary unless you want to build apps for Blackberry devices

http://www.qnx.com/content/qnx/en/products/tools/qnx-momentics.html