Java Interfaces

Interfaces:

package main.java; public interface MyInterface { public void myMethod(); // The code for this function is not defined here }

package main.java; public class MyImplementation1 implements MyInterface { public void myMethod () { System.out.println( "My implementation of interface" ); } }

package main.java; public class MyImplementation2 implements MyInterface { public void myMethod () { System.out.println( "My alternative implementation of interface" ); } }

- Applying an interface requires that a class has the named functions defined

- It's similar to inheritance but you use the "implements keyword instead of "extends"

- This is useful if you want to make an array of different classes that share the function(s) specified in the interface

- Multiple interfaces can be applied to a class (just add the other interfaces after "implements", separating each with a comma)

Grouping Objects With a Shared Interface

package main.java; public class MainClass { public static void main (String [] args) { // Create array of various types of objects that implement the same interface MyInterface1 [] objs = new MyInterface1 [2]; objs[0] = new MyImplementation1 (); objs[1] = new MyImplementation2 (); // Then you can call the shared function on each of them for (MyInterface item : myList) { item.myMethod(); } } }

- This is useful if you have a variety of class types, but you need them all to answer to perform a certain action in their own way (such as 'display')

Challenge

Create two classes (Teacher and Student) that apply an interface requiring them to have a getId function. Then, define that function within each of the classes. Finally, create an array that contains objects of both class types (Teacher and Student).

Quiz

Completed