Intro to Java Collections

This entry is part 7 of 13 in the series Intro to Java

I don’t want to get too deep into every little thing in the collections classes here. In fact, you already know a fair bit about them, because we have used them with some of our Animal class examples. This is more an overview of some of the basic Collections classes.

What do they look like?

There are three main types of collections: Lists, Maps, and Sets. Technically you could try to argue that Map doesn’t extend Collection, so therefore it is not a Collection, but I think of it as part of the group.
They are used for groups of objects, or exactly as its name would imply, collections of objects.


A List is just that, a list of objects. The List interface provides a way to add, remove and get objects from a list. It however is just an interface. ArrayList is one of the more popular concrete collections that implements the List interface. Each implementation of the List interface may behave slightly different, but once you understand how a List works, you have a good start on understanding any List.
Continue reading