catching NPEs isn't a good practice. This should be solved at the point where the NPE occurs if possible.

catching NPEs isn't a good practice. This should be solved at the point where the NPE occurs if possible.

+1 - catching a NPE is almost always the bad solution. If something can validly be null, there should be a null check. If something is believed to not to be null, and it is null, the source that is incorrectly providing null should be fixed.

In this case, I have a question: if the selectedProject/selectedRoot are null, will this code be called again/the results be refreshed when they are set to non-null?

Thanks @mbien and @lahodaj ! I will make the changes to check for null directly and handle it gracefully rather than catching the NPE. @lahodaj To answer your question yes this code will be called again when selectedProject/selectedRoot is non null or is changed .