I revise many posts about this topic , i note that Ubuntu should install NetBeans under:
ln -s /usr/local/netbeans-y.y/
/usr/local and i don't find any netbeans known that i have installed two versions of NetBeans
Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.Visit Stack Exchange
Ask Ubuntu is a question and answer site for Ubuntu users and developers. It only takes a minute to sign up.Sign up to join this community
It depends on your installation process. If you dont install it as root, it should be located at ~/netbeans-x.x otherwise it is at /usr/local/netbeans-x.x.
Great . i found it . It is under your home directory :
$ ls ~ |grep net netbeans-6.5 netbeans-8.0