dtonhofer

dtonhofer

Functional Programming in Java, Second Edition: Functional Programming in Java, Second Edition: JUnit code improvements for Chapter 11, pages 193 ff “Refactoring Data Grouping Operations”

As usual, but the original code to be refactored was just too evil and had to be fixed.

package chapter11;

import org.junit.jupiter.api.Test;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.toSet;
import static org.junit.jupiter.api.Assertions.assertAll;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class DataGroupingOperationsTest {

    interface Scores {

        Map<Integer, Set<String>> namesForScores(final Map<String, Integer> scores);

    }

    public static class ScoresBefore implements Scores {

        public Map<Integer, Set<String>> namesForScores(final Map<String, Integer> scores) {
            final Map<Integer, Set<String>> result = new HashMap<>();
            for (Map.Entry<String, Integer> entry : scores.entrySet()) {
                final String name = entry.getKey();
                final Integer score = entry.getValue();
                if (!result.containsKey(score)) {
                    result.put(score, new HashSet<>());
                }
                result.get(score).add(name);
            }
            return result;
        }
    }

    public static class ScoresAfter implements Scores {

        public Map<Integer, Set<String>> namesForScores(final Map<String, Integer> scores) {
            return scores.keySet().stream()
                    .collect(groupingBy(scores::get, toSet()));
        }
    }

    private static void commonNamesForScoresTests(final Scores scores) {
        assertAll(
                () -> assertEquals(Map.of(), scores.namesForScores(Map.of())),
                () -> assertEquals(
                        Map.of(1, Set.of("Jill")), scores.namesForScores(Map.of("Jill", 1))),
                () -> assertEquals(
                        Map.of(1, Set.of("Jill"), 2, Set.of("Paul")),
                        scores.namesForScores(Map.of("Jill", 1, "Paul", 2))),
                () -> assertEquals(
                        Map.of(1, Set.of("Jill", "Kate"), 2, Set.of("Paul")),
                        scores.namesForScores(Map.of("Jill", 1, "Paul", 2, "Kate", 1)))
        );
    }

    @Test
    void scoresBefore() {
        commonNamesForScoresTests(new ScoresBefore());
    }

    @Test
    void scoresAfter() {
        commonNamesForScoresTests(new ScoresAfter());
    }
}

Where Next?

Popular Pragmatic Bookshelf topics Top

New
herminiotorres
Hi @Margaret , On page VII the book tells us the example and snippets will be all using Elixir version 1.11 But on page 3 almost the en...
New
jeremyhuiskamp
Title: Web Development with Clojure, Third Edition, vB17.0 (p9) The create table guestbook syntax suggested doesn’t seem to be accepted ...
New
Chrichton
Dear Sophie. I tried to do the “Authorization” exercise and have two questions: When trying to plug in an email-service, I found the ...
New
swlaschin
The book has the same “Problem space/Solution space” diagram on page 18 as is on page 17. The correct Problem/Solution space diagrams ar...
New
New
akraut
The markup used to display the uploaded image results in a Phoenix.LiveView.HTMLTokenizer.ParseError error. lib/pento_web/live/product_l...
New
rainforest
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
New
tkhobbes
After some hassle, I was able to finally run bin/setup, now I have started the rails server but I get this error message right when I vis...
New
roadbike
From page 13: On Python 3.7, you can install the libraries with pip by running these commands inside a Python venv using Visual Studio ...
New

Other popular topics Top

PragmaticBookshelf
Andy and Dave wrote this influential, classic book to help their clients create better software and rediscover the joy of coding. Almost ...
New
PragmaticBookshelf
Free and open source software is the default choice for the technologies that run our world, and it’s built and maintained by people like...
New
Rainer
My first contact with Erlang was about 2 years ago when I used RabbitMQ, which is written in Erlang, for my job. This made me curious and...
New
New
AstonJ
We’ve talked about his book briefly here but it is quickly becoming obsolete - so he’s decided to create a series of 7 podcasts, the firs...
New
PragmaticBookshelf
Author Spotlight Jamis Buck @jamis This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
AstonJ
If you want a quick and easy way to block any website on your Mac using Little Snitch simply… File &gt; New Rule: And select Deny, O...
New
PragmaticBookshelf
Develop, deploy, and debug BEAM applications using BEAMOps: a new paradigm that focuses on scalability, fault tolerance, and owning each ...
New
AstonJ
This is cool! DEEPSEEK-V3 ON M4 MAC: BLAZING FAST INFERENCE ON APPLE SILICON We just witnessed something incredible: the largest open-s...
New
CommunityNews
Open-source implementation of the classic GTA engine now running directly in your browser. Experience the reVC technology demo on DOS.Zon...
New

Latest in Functional Programming in Java, Second Edition

Functional Programming in Java, Second Edition Portal

Sub Categories: