lambda pazzle

Forrest.java

package lambda.puzzle;

// source: http://arhipov.blogspot.ru/2014/02/java-8-lambdas-unintentional-puzzle.html
public class Forrest {
    public Runnable wrooom(){
        return () -> { System.out.println("Hello, lambda!"); };
    }

    public static void main(String[] args) {
        Runnable runnable = new Forrest().wrooom();
        runnable.run(); // print "Hello, lambda!"

        Runnable runnable2 = new Forrest()::wrooom;
        runnable2.run(); // print nothing
    }
}