Let's create a simple mobile messenger application. The idea of the application is to check the logged-in user's contacts list and then if anyone from those contacts is using the application, it will show them in a list from where the user can start messaging them in the application. The application will allow you to send one-to-one messages to one of the user's contacts and, on the other end, the user can view it and reply. This would be a good start as we will learn many important things to build applications.
Let's break down the problem statement, which will be easy for us to build the application: