More advanced persistence

Let's think about what we need to do. We want to save a bunch of notes to the internal storage. Being more specific, we want to store a selection of strings and related Boolean values. These strings and Boolean values represent the user's note title, the note's text, and whether it is a to-do, important, or an idea.

Given what we already know about the SharedPreferences class, at first glance this might not seem especially challenging – until we dig a little deeper into our requirements. What if the user loves our app and ends up with 100 notes? We would need 100 identifiers for key-value pairs. Not impossible, but starting to get awkward.

Now consider that we want to enhance the app and give the user the ability to add dates to them. Android has a Date class that is perfect for this. It would be reasonably straightforward to then add neat features such as reminders to our app. But when it comes to saving data, suddenly, things...