Product Version = NetBeans IDE 8.2 (Build 201609300101)
Operating System = Windows 7 version 6.1 running on amd64
Java; VM; Vendor = 1.8.0_101
Runtime = Java HotSpot(TM) 64-Bit Server VM 25.101-b13

Reproducibility: Happens every time

STEPS:
When having open files in editor, changing project group (Menu File->Project Groups...) doesn't change opened files in Editor. I've actually 2 projects groups as I'm working on 2 different projects. Sometimes, it keeps opened files and opens new files from new selected project group. Depending on order of Project Groups, it open or not the file from new project group, so having opened files from 2 project groups.

ACTUAL:
When changing project group, It doesn't close opened files in previous selected project proup and/or doesn't open files from new project groups.

EXPECTED:
Keep list of opened project groups files and open them automatically when selecting a project group. At the same time, save opened files in previous selected opened group and close them. So changing project let continue where we stopped working, with same opened files.