Behavior of Functional Interface and Method Reference

Question

What happens when the reference of a method which belongs to a variable is destroyed?

public class Hey{
    public double bar;

    public Hey(){
        bar         


        

Answer 1

Your method reference is essentially equivalent to doing this:

Hey hey = new Hey();
Function square = new DoubleDoubleFunction(hey);

where the class DoubleDoubleFunction is defined like this

class DoubleDoubleFunction implements Function {
    private final Hey hey;

    public DoubleDoubleFunction(Hey hey) {
        this.hey = hey;
    }

    @Override
    public Double apply(Double num) {
        return hey.square(num);
    }
}

In other words, square holds a reference to the Hey.

I don't know about eclipse, but with IntelliJ you can easily translate method references and lambdas into anonymous / static nested / inner classes to see what's going on. I find this a very instructive thing to do.