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

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
AleksandrKudashkin
On the page xv there is an instruction to run bin/setup from the main folder. I downloaded the source code today (12/03/21) and can’t see...
New
joepstender
The generated iex result below should list products instead of product for the metadata. (page 67) iex&gt; product = %Product{} %Pento....
New
leonW
I ran this command after installing the sample application: $ cards add do something --owner Brian And got a file not found error: Fil...
New
curtosis
Running mix deps.get in the sensor_hub directory fails with the following error: ** (Mix) No SSH public keys found in ~/.ssh. An ssh aut...
New
fynn
This is as much a suggestion as a question, as a note for others. Locally the SGP30 wasn’t available, so I ordered a SGP40. On page 53, ...
New
adamwoolhether
I’m not quite sure what’s going on here, but I’m unable to have to containers successfully complete the Readiness/Liveness checks. I’m im...
New
jonmac
The allprojects block listed on page 245 produces the following error when syncing gradle: “org.gradle.api.GradleScriptException: A prob...
New
kolossal
Hi, I need some help, I’m new to rust and was learning through your book. but I got stuck at the last stage of distribution. Whenever I t...
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

Other popular topics Top

New
PragmaticBookshelf
Machine learning can be intimidating, with its reliance on math and algorithms that most programmers don't encounter in their regular wor...
New
PragmaticBookshelf
Brace yourself for a fun challenge: build a photorealistic 3D renderer from scratch! In just a couple of weeks, build a ray tracer that r...
New
AstonJ
Or looking forward to? :nerd_face:
498 14002 274
New
AstonJ
There’s a whole world of custom keycaps out there that I didn’t know existed! Check out all of our Keycaps threads here: https://forum....
New
AstonJ
Do the test and post your score :nerd_face: :keyboard: If possible, please add info such as the keyboard you’re using, the layout (Qw...
New
PragmaticBookshelf
Learn different ways of writing concurrent code in Elixir and increase your application's performance, without sacrificing scalability or...
New
PragmaticBookshelf
Author Spotlight Rebecca Skinner @RebeccaSkinner Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New
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

Latest in Functional Programming in Java, Second Edition

Functional Programming in Java, Second Edition Portal

Sub Categories: