Delete from asset folder ("Hello World Android App")

I tried to run the “Hello World” Android application and everything goes correctly.
I deleted the file from the assets folder and the application continues to run correctly. How is it possible that the model was found if it was deleted?
Sorry for the stupid question and for my bad English

Cause the java app has builded before you deleted the file

so if I want to change the model what should I do to delete the old one?

Not only re-run the app but also rebuild it

I’ve already done it and it doesn’t work. I even tried to delete the app and download it again, immediately delete the and run it for the first time, incredibly it works. I am desperate