You've seen how objects combine state and behavior, and how we can construct them and protect their private state. In this lesson we'll put all of those capabilities to use in modeling a real-world entity! After all, that's one of the things that Java objects are for...
First, as a warm-up, let's construct the imperative logic that we need to check the board. We'll then use this later in our solution!
As our example we'll model a game of tic-tac-toe. Whenever we model something using a Java class, we want to consider:
Note that frequently these considerations overlap. We may need to add state to support some action that we realize that we want our class to support. But, anyway, we'll get there. Let's get started!
But before we can even start designing our class, we need to choose a name! That's not as simple as it sounds! Frequently deciding on a name can encourage you to give some initial productive consideration to exactly what it is that you're modeling...
First, let's think about what a
class modeling a tic-tac-toe game needs to store.
Let's work through that together and begin designing our classes instance variables:
With an initial set of instance variables, let's think through various things that we want our game model to be able to do. This is not a complete list! You may have other ideas of what to add:
Now let's have some fun implementing these features! Note that, as we go, we may find places where we need to add state, or create some helper functions. We'll see!
Cool! You designed and implemented your first interesting Java class. That was fun! Don't worry—you'll get a lot more practice.
Before we finish this lesson, I want to introduce you to a brand new Java feature. It's so new, that it's not an official part of Java yet—it's still in so-called preview mode in Java 15, which just came out. However, it's really exciting, and provides a much simpler way of working with classes.
Need more practice? Head over to the practice page.