How to quit android application programmatically

Question

I Found some codes for quit an Android application programatically. By calling any one of the following code in onDestroy() will it quit application entirely?

Answer 1

It's not a good decision, cause it's against the Android's application processing principles. Android doesn't kill any process unless it's absolutely inevitable. This helps apps start faster, cause they're always kept in memory. So you need a very special reason to kill your application's process.