Getting user's name in Android

I would like to get the user's name in my app so that it can provide a personalized message during it's first run like,

Hey %user's name,

..

Since the app will be paid and primarily available on Google Play Store, i would have all the information about the user as in their synced gmail account. But how do i go about writing code for it?

As suggested by cricket_007, Google Sign-In API provides the user's display name.