How can we use this and super keywords in method reference in Java?

The method reference is similar to a lambda expression that refers to a method without executing it and "::" operator can be used to separate a method name from the name of an object or class in a method reference.

The methods can be referenced with the help of this and super keywords in Java. The super keyword can be used as a qualifier to invoke the overridden method in a class or an interface.

syntax

this::instanceMethod
TypeName.super::instanceMethod

Example

import java.util.function.Function;

interface Defaults {
   default int doMath(int a) {
      return 2 * a;
   }
}
public class Calculator implements Defaults {
   @Override
   public int doMath(int a) {
      return a * a;
   }
   public void test(int value) {
      Function<Integer, Integer> operator1 = this::doMath;
      System.out.println("this::doMath() = " + operator1.apply(value));

      Function<Integer, Integer> operator2 = Defaults.super::doMath;
      System.out.println("Defaults.super::doMath() = " + operator2.apply(value));
   }
   public static void main(String[] args) {
      Calculator calc = new Calculator();
      calc.test(10);
   }
}

Output

this::doMath() =  100
Defaults.super::doMath() = 20