This document discusses dependency injection in Android applications. It begins by providing an example of how dependency injection improves testability by removing tight coupling between classes. It then addresses some common questions that arise regarding dependency injection principles. The document emphasizes that dependency injection is an architectural pattern that involves separating classes into functional and construction sets. When implemented properly, dependency injection provides benefits like easier code reuse, better maintainability, and improved testability. While an overkill for small projects, it is considered one of the most beneficial patterns for larger object-oriented applications. The document concludes by offering best practices for implementing dependency injection.