Java 8 : Method References

This is a new concept introduced with Java 8. We refer method reference with “::” (i.e. double colon) operator. This will used to replace lamba expressions like in below code.

import java.util.ArrayList;

import java.util.List;

public class MethodReference {

       public static void main(String[] args) {

              List numbers = new ArrayList<>();

              numbers.add(7);

              numbers.add(4);

              numbers.add(1);

              numbers.add(8);

              numbers.add(5);

              numbers.add(2);

              numbers.add(9);

              numbers.add(6);

              numbers.add(3);

              numbers.add(0);

              //numbers.sort((a,b)->Integer.compare(a,b));

              numbers.sort(Integer::compare);

//numbers.forEach(number -> System.out.println(number));

              numbers.forEach(System.out::println);;

       }

}

This helps you to call in following instances:

 object :: instanceMethod

·         Class :: staticMethod

·         Class :: instanceMethod

And it is also valid to use ‘super’ or ‘this’ with method reference.

public class Greeter {

       public void greet(){

              System.out.println("Hello World!");

       }

}

public class ConcurrenceGreeter extends Greeter {

       @Override

       public void greet() {

              Thread greet = new Thread(super::greet);

              greet.start();

              Thread bye = new Thread(this::bye);

              bye.start();

       }

      

       public void bye(){

              System.out.println("See you again.");

       }

       public static void main(String[] args) {

              Greeter greeter = new ConcurrenceGreeter();

              greeter.greet();

       }

}