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());
}
}
Popular Pragmatic Bookshelf topics
I thought that there might be interest in using the book with Rails 6.1 and Ruby 2.7.2. I’ll note what I needed to do differently here.
...
New
Title: Hands-on Rust: question about get_component (page 295)
(feel free to respond. “You dug you’re own hole… good luck”)
I have somet...
New
Hi Travis! Thank you for the cool book! :slight_smile:
I made a list of issues and thought I could post them chapter by chapter. I’m rev...
New
I found an issue in Chapter 7 regarding android:backgroundTint vs app:backgroundTint.
How to replicate:
load chapter-7 from zipfile i...
New
When trying to run tox in parallel as explained on page 151, I got the following error:
tox: error: argument -p/–parallel: expected one...
New
Hi all,
currently I wonder how the Tailwind colours work (or don’t work).
For example, in app/views/layouts/application.html.erb I have...
New
@mfazio23
I’m following the indications of the book and arriver ad chapter 10, but the app cannot be compiled due to an error in the Bas...
New
Hello faithful readers! If you have tried to follow along in the book, you are asked to start up the dev environment via dx/build and ar...
New
I just bought this book to learn about Android development, and I’m already running into a major issue in Ch. 1, p. 20: “Update activity...
New
@mfazio23
Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New
Other popular topics
If it’s a mechanical keyboard, which switches do you have?
Would you recommend it? Why?
What will your next keyboard be?
Pics always w...
New
Algorithms and data structures are much more than abstract concepts. Mastering them enables you to write code that runs faster and more e...
New
Design and develop sophisticated 2D games that are as much fun to make as they are to play. From particle effects and pathfinding to soci...
New
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
poll
poll
Be sure to check out @Dusty’s article posted here: An Introduction to Alternative Keyboard Layouts It’s one of the best write-...
New
I am asking for any distro that only has the bare-bones to be able to get a shell in the server and then just install the packages as we ...
New
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
New
Author Spotlight
Jamis Buck
@jamis
This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
Author Spotlight
Rebecca Skinner
@RebeccaSkinner
Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New
Explore the power of Ash Framework by modeling and building the domain for a real-world web application.
Rebecca Le @sevenseacat and ...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /wasm
- /ruby
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /emacs
- /java
- /haskell
- /svelte
- /onivim
- /typescript
- /kotlin
- /c-plus-plus
- /crystal
- /tailwind
- /react
- /gleam
- /ocaml
- /elm
- /flutter
- /vscode
- /ash
- /html
- /opensuse
- /zig
- /centos
- /deepseek
- /php
- /scala
- /react-native
- /lisp
- /sublime-text
- /textmate
- /nixos
- /debian
- /agda
- /django
- /deno
- /kubuntu
- /arch-linux
- /nodejs
- /ubuntu
- /revery
- /spring
- /manjaro
- /diversity
- /lua
- /julia
- /markdown
- /v








