Let's pause before moving on to get more practice with Kotlin's collections—the lists, maps, and sets that are so useful for solving problems. We'll also learn how we can combine these collections together to build more interesting data structures. Let's get started!
In the past lessons we've seen how to create and use several standard Kotlin collections:
These collections are quite useful on their own! However, they can also be combined to great effect. Let's see an example.
You can combine
Sets in many interesting ways to build data structures to solve problems.
You can create
But generally, it's more common for the top-level data structure to be a
We'll get some practice working with these on this lesson's practice and homework problems.
One thing you may have noticed is that Kotlin's
null checking doesn't work so well in some cases on maps.
Let's briefly discuss why this is, and what we can do about it.
We'll spend the rest of the lesson working on some problems that test our understanding of how to nest collections.
First, we're asked to parse a
List<String> into a
Let's do an example of that together, which you can use as a starting point for the practice problem that follows.
Today's homework problem is a challenge! Your goal is to complete the implementation of the Hawaiian Word translator you began earlier this semester. Since this problem is more difficult than other homework problems, we're giving you an extra day to complete it. And, at the end of the day, please remember that this is just one problem, and you have homework drops.
We'll also get you started with a walkthrough to help you think about how to approach this problem.
Note that the problem asks you to throw an exception in certain cases, something that we have not yet covered. The walkthrough describes how to do that.
Need more practice? Head over to the practice page.