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Implementing Interfaces3:19 with Ben Deitch
In this video we'll create and implement the 'Chattable' interface!
All right, were you able to create a talking teacup? 0:00 Either way, here's how I did it. 0:03 First, we need to make an interface to hold the chat method. 0:05 To do this, I'll right click on the package, pick New, 0:09 Java class, then I'll name it Chattable. 0:14 Change the kind from class to interface, and hit Okay. 0:20 Now that I've got my interface, inside I just need to declare the chat method. 0:25 So String chat, and there we go. 0:31 But before we move on, just a few quick notes. 0:37 First, notice this green I icon, which tells us that the file is an interface. 0:41 Second, even though IntelliJ makes this look so 0:48 official with the green I icon, remember these are all just .java files. 0:52 So if we wanted to change this from an interface and 0:57 to a class, there's nothing stopping us. 0:59 Finally, if you chose a different name for your interface, 1:05 there's a shortcut we can use to rename it everywhere in the project. 1:07 This way, you can just change it in one place, and 1:11 IntelliJ will change it in the rest. 1:14 If you'd like to rename your interface, put your cursor on it, and 1:17 use Shift+F6 to bring up the rename option. 1:20 You can also right+click, refactor, and rename. 1:25 Now it's time to use our interface. 1:31 We need to update the Person class, update the Shopkeeper class, and 1:33 create our new Teacup class. 1:37 Let's start with the Person class. 1:40 To implement our interface, 1:42 we just need to add implements Chattable after the class name. 1:44 Then, since all interface methods are public, 1:50 we'll need to update our Person's chat method to be public. 1:53 Which we can do using Alt+Enter. 2:00 Also, even though the override annotation is optional, and 2:03 we don't have any errors, we should still add it. 2:07 So let's add a line here and add the override annotation, 2:11 because this method is overriding from the chat method in Chattable. 2:14 Moving on to the Shopkeeper class, 2:20 all we would need to do here is make the chat function public. 2:22 However, since we used Alt+Enter to fix it in the Person class, 2:26 IntelliJ has already fixed that for us. 2:29 Finally, let's create the Teacup class. 2:33 Let's right click on the package, and choose New, Java Class. 2:37 Then let's name it Teacup, and hit Enter. 2:42 Now that we've got the class, 2:45 let's make it implement our Chattable interface with implements and Chattable. 2:47 And let's wrap it up by using Alt+Enter to implement the chat method. 2:53 And let's make out Teacup say something like, hi, I'm a Teacup. 3:02 Now I'm sure we can all agree that this code just feels a bit better. 3:08 But to help drive that point home, 3:13 let's look at a couple examples in the next video. 3:15
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