OOGreeting_Greeter.java

package OOGreeting;
//Objectr Oriented way

public class Greeter {

    public void greet(Greeting greeting) {
        greeting.perform();
    }

    public static void main(String[] args) {

        Greeter greeter = new Greeter();

        //Greeting helloWorldGreeting = new HelloWorldGreeting();

        //Both give same result. Lambda is shorter
        Greeting lamdaGreeting = () -> System.out.println("Hello Lambda");

        Greeting innerClassGreeting = new Greeting() {
            @Override
            public void perform() {
                System.out.println("Hello Inner Class");
            }
        };

       greeter.greet(lamdaGreeting);
       greeter.greet(innerClassGreeting);
    }
}

/*interface MyAdd {
    int add(int a, int b);
}*/

OOGreeting_Greeting.java

package OOGreeting;

public interface Greeting {
    public void perform();
}

OOGreeting_HelloWorldGreeting.java

package OOGreeting;

public class HelloWorldGreeting implements Greeting {

    @Override
    public void perform() {
        System.out.println("Hello Interface");
    }
}