Netbeans refuses to auto suggest known classes for imports

Today I came across the same problem. It happens that it actually is very easy to exclude a class from code completion if you click in the wrong place while working.

To solve it (netbeans 8.2) go to

Tools - Options -> Editor tab

Then select Code Completion Tab

In the drop Down select JAVA (in my case it was Java)

You will find a box bellow titled Package/Classes In the EXCLUDE tab you probably will find the packages marked to be excluded from code completion. Just remove the ones you want back.

I had the same problem a couple minutes ago... Terrible. The same problem has been reported here:

Bug 235712

The solution which I've found there was sufficient - simply delete the Netbeans cache...

In order to do this, go to Help ==> About . Then go to the directory with cache and delete all you find in the "index" catalog.

After restarting the NB, everything was cool.