Application

According to Meier at Kindle locations 2459-2461, you define your own application implementation when you need to:

• Respond to application level events broadcast by the Android run time such as low memory conditions.
• Transfer objects between application components.
• Manage and maintain resources used by several application components.

Declaration

You declare your application in the manifest and the application class will be automatically instantiated when the application is run.

It's best practice to declare your application as a singleton.