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  • Karthik Rajagopalan thinks this is interesting:

Because activities are constantly being stopped and started for a variety of reasons, there’s no way for your activity to know if it’s being started for the very first time in the run of your application. The Application class’s onCreate method, on the other hand, is called only when your app is being initialized. As such, it can be a good place to take actions that should happen only when your application is first started.

From

Cover of Beginning Android Programming: Develop and Design

Note

Why Application is used?