Method reference in Java 8

Question

public class Car {

    private int maxSpeed;

    public Car(int maxSpeed) {
        this.maxSpeed = maxSpeed;
    }

    public int getMaxSpeed() {
        return maxS         


        

Answer 1

If you want to create a method reference for a method that takes no parameters, such as a method already bound to an instance, you should use a Supplier, not a Function:

Function f1 = Car::getMaxSpeed;

Car carx = new Car(42);
Supplier f2 = carx::getMaxSpeed; 

In the method reference carX::getMaxSpeed, the "implicit" this-parameter of the function is already bound to carx, so you are left with a no-parameter-function (which, by the way, can not be used in a Comparator), and in Java 8, a no-parameter-function is just a Supplier.

Similarly, if you have a method that returns void, you end up with a Comsumer:

Consumer f3 = carx::setMaxSpeed;