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
Following the steps described in Chapter 6 of the book, I’m stuck with running the migration as described on page 84:
bundle exec sequel...
New
Many tasks_proj/tests directories exist in chapters 2, 3, 5 that have tests that use the custom markers smoke and get, which are not decl...
New
Hi everyone!
There is an error on the page 71 in the book “Programming machine learning from coding to depp learning” P. Perrotta. You c...
New
Hi Jamis,
I think there’s an issue with a test on chapter 6. I own the ebook, version P1.0 Feb. 2019.
This test doesn’t pass for me:
...
New
Hello! On page xix of the preface, it says there is a community forum "… for help if your’re stuck on one of the exercises in this book… ...
New
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
In case this helps anyone, I’ve had issues setting up the rails source code. Here were the solutions:
In Gemfile, change
gem 'rails'
t...
New
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
Title: Build a Weather Station with Elixir and Nerves: Problem connecting to Postgres with Grafana on (page 64)
If you follow the defau...
New
I’ve got to the end of Ch. 11, and the app runs, with all tabs displaying what they should – at first. After switching around between St...
New
Other popular topics
Ruby, Io, Prolog, Scala, Erlang, Clojure, Haskell. With Seven Languages in Seven Weeks, by Bruce A. Tate, you’ll go beyond the syntax—and...
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
Use WebRTC to build web applications that stream media and data in real time directly from one user to another, all in the browser.
...
New
Hi folks,
I don’t know if I saw this here but, here’s a new programming language, called Roc
Reminds me a bit of Elm and thus Haskell. ...
New
This is going to be a long an frequently posted thread.
While talking to a friend of mine who has taken data structure and algorithm cou...
New
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
I have always used antique keyboards like Cherry MX 1800 or Cherry MX 8100 and almost always have modified the switches in some way, like...
New
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc.
However, I don’t...
New
This is cool!
DEEPSEEK-V3 ON M4 MAC: BLAZING FAST INFERENCE ON APPLE SILICON
We just witnessed something incredible: the largest open-s...
New
Open-source implementation of the classic GTA engine now running directly in your browser. Experience the reVC technology demo on DOS.Zon...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /wasm
- /ruby
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /java
- /clojure
- /emacs
- /haskell
- /typescript
- /svelte
- /onivim
- /kotlin
- /c-plus-plus
- /crystal
- /tailwind
- /react
- /gleam
- /ocaml
- /elm
- /vscode
- /flutter
- /html
- /ash
- /deepseek
- /zig
- /opensuse
- /centos
- /php
- /scala
- /react-native
- /lisp
- /textmate
- /sublime-text
- /nixos
- /debian
- /agda
- /deno
- /django
- /kubuntu
- /arch-linux
- /nodejs
- /spring
- /ubuntu
- /revery
- /manjaro
- /lua
- /diversity
- /julia
- /quarkus
- /markdown









