Hi Ann,
Thank you so much for the reply and sorry for too much delay in the reply.Actually it was a typo in sonar.source. I used exact sonar.sources in the configuration but it didnt work.
I have defined sonar.sources in build.gradle file as:

Still it shows “The project is empty”.
I don’t know whether it is analyzing my project or not. And if it is analyzing then why it is not showing any bug, vulnerability or defect etc.