Similar to a Java Class but Different – Interfaces

While Java Interfaces have been around since Java 1.0. Java version 1.8 (8) enhanced interfaces providing inhertible default methods, static methods and more.

A class must implement all methods that an interface defines, a class can inherit from multiple interfaces using the implements key word with multiple interfaces separated by commas.

interface FirstInterface {
  public void firstMethod();
}

interface SecondInterface {
  public void secondMethod();
}

public class MyClass implements FirstInterface, SecondInterface {
  public void firstMethod() {
    System.out.println("Implemented firstMethod of FirstInterface");
  }

  public void secondMethod() {
    System.out.println("Implemented secondMethod of SecondInterface");
  }

  public static void main(String[] args) {
    MyClass myObj = new MyClass();
    myObj.firstMethod();
    myObj.secondMethod();
  }
}