Java Lambda:return and not return And Ordinary Function same same as classname

package com.xiuye.lambda;

@FunctionalInterface
interface Fn {
 void f();
}

@FunctionalInterface
interface FnRet<T> {
 T f();
}

public class AmbiguousLambda2 {

 //it's OK();
 void AmbiguousLambda2(){
  log("Ordinay function");
 }

 public static void f(Fn f) {
  f.f();
 }

 public static <T> void f(FnRet<T> fr) {
  fr.f();
 }

 static <T> void log(T t) {
  System.out.println(t);
 }

 public static void main(String[] args) {
  AmbiguousLambda2 al = new AmbiguousLambda2();
  al.AmbiguousLambda2();
  f(()->log("not returned"));
  f(()->{log("returned");return 100;});
 }

}

Ordinay function
not returned
returned