I\'m developing with Android Studio/IntelliJ IDEA.
I have enabled the inspection check called "Constant conditions & exceptions" that shows a warning if
You can look into the link that Peter Gromov mention in his answer.
Created some simple classes that resemble your setup:
A class with a method annotated with @Nullable:

The TextUtil class with it's isEmpty method:

And finally the main class calling the TextUtil#isEmpty:

Now if you enter the File -> Settings... and go to Inspections ->Constant conditions & exceptions part you can change the Configure Assert/Check Methods to cater for your isEmpty method:

Add a new IsNull check method:

Enter the TextUtil class, isEmpty method and CharSequence parameter:

This gives this Assert/Check Method Configuration window:

Press Ok and then Ok again to go back to the editor view and you'll see that the inspection disappeared:

You are actually telling IntelliJ that the isEmpty method is doing a null check on the str parameter.