More Java Collections – Meet Java Hashmap

Java HashMaps are neat. They are part of the Java Collections and a kind of cousin to ArrayList which we have now used in two projects (this will be the third). They basically encapsulate really useful data storage techniques that would otherwise be quite technical for us to code successfully for ourselves.

We will get practical with HashMap in the next section when we discuss a problem regarding storing Bitmap instances in our GameObject instances. HashMap will be the second part (Singletons are the first part) of the solution to this problem.

I thought it would be worth taking a first look at HashMap on its own.

Suppose, we want to store the data of lots of characters from an RPG type game and each different character is represented by an object of type Character.

We could use some of the Java tools we already know about like arrays or ArrayList. However, Java HashMap is also similar to these things but with HashMap we can give a unique key...