Welcome back! Next we continue our journey with interfaces. In the last lesson we examined how to use interfaces. Now we’ll look at how to provide them in our own classes, and the kind of amazing things that this can unleash. Let’s go!
Last time we focused on using interfaces. In this lesson we’ll discuss implementing them ourselves. Along the way we’ll also discuss more about exactly how interfaces are so powerful.
As we begin to focus on using interfaces, it makes sense to think about an interface as a contract.
implement an interface in one of your classes, you agree not only to provide certain methods, but also that these methods will do certain things!
Let’s return to our favorite Java interface—
Comparable—for an example of how to read an interface like a contract.
Keep in mind that we can use this interface in Kotlin even though it is provided by Java!
Now, let’s put what we’ve learned to use by designing a new
class and making it
Another important way to think about interfaces is as something called an abstraction barrier.
An abstraction barrier separates two parts of a program or system in ways that allow them to develop independently.
Again, let’s return to
Comparable to discuss exactly how that works!
Create a public class
LastOdd that implements the following interface:
This is a distinction that can be tricky for people. So let’s go through an example together and discuss the differences.
Create a public class
RunningTotal that implements the following interface:
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Rachel Kroll has a few talks up online, but they’re long. So instead, please just read and enjoy this short piece commenting on code complexity. “Code runs on people. Please keep it simple.”
Need more practice? Head over to the practice page.