How to use file masking in IntelliJ IDEA (Updated)
Intellij Idea is a popular Java IDE. But usually, a java project may contain different kinds of files as well. For example in my case, we were using proto files in our application.
So while searching a function name in the proto file, you might also get java files.
For this, we can use file masking.
To open finder, click command + shift + f
Select file masking option
and type *.proto
After that, you will only get proto files in the search.

Update
In earlier versions, just typing .proto would have worked. But now after the update, we need to write *.proto to get the same result.