Please take a look at the todo part and help with the following code! Thank you so much!

package fp;

import java.math.BigDecimal;

import java.util.ArrayList;

import java.util.Comparator;

import java.util.Map;

import java.util.function.$*$;

import java.util.stream.Collectors;

import java.util.List;

class ExerciseNotCompletedException extends RuntimeException $\{$

public ExerciseNotCompletedException$()\{$

super$("$Exercise is not completed yet"$)$;

$\}$

$\}$

$/**$

$*\{$@link HW$\}$ is an exercise class. Each method returns a functional interface and it should be implemented

$*$ using either lambda or a method reference. Every method that is not implemented yet throws

$*\{$@link ExerciseNotCompletedException$\}.$

$*$

$*$ TODO: remove exception and implement each method of this class using lambda or method reference

$*$