Summary

In this chapter, we looked at how to use simple Java arrays to store substantial amounts of data, provided it is of the same type. We also used ArrayList, which is like an array with loads of extra features. Furthermore, we found out that both arrays and ArrayList are polymorphic, which means that a single array (or ArrayList) can hold multiple different objects, as long as they are all derived from the same parent class.

We also learned about the HashMap class, which is also a data storage solution, but which allows access in different ways.

In the next chapter, we will learn about Adapter and RecyclerView to put our theory into practice and enhance our Note to Self app.