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
Working through the steps (checking that the Info,plist matches exactly), run the demo game and what appears is grey but does not fill th...
New
Title: Web Development with Clojure, Third Edition, pg 116
Hi - I just started chapter 5 and I am stuck on page 116 while trying to star...
New
When I try the command to create a pair of migration files I get an error.
user=> (create-migration "guestbook")
Execution error (Ill...
New
Title: Hands-On Rust (Chap 8 (Adding a Heads Up Display)
It looks like
.with_simple_console_no_bg(SCREEN_WIDTH*2, SCREEN_HEIGHT*2...
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
Hey there,
I’m enjoying this book and have learned a few things alredayd. However, in Chapter 4 I believe we are meant to see the “>...
New
The markup used to display the uploaded image results in a Phoenix.LiveView.HTMLTokenizer.ParseError error.
lib/pento_web/live/product_l...
New
I’m a newbie to Rails 7 and have hit an issue with the bin/Dev script mentioned on pages 112-113.
Iteration A1 - Seeing the list of prod...
New
It seems the second code snippet is missing the code to set the current_user:
current_user: Accounts.get_user_by_session_token(session["...
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
@AstonJ prompted me to open this topic after I mentioned in the lockdown thread how I started to do a lot more for my fitness.
https://f...
New
This looks like a stunning keycap set :orange_heart:
A LEGENDARY KEYBOARD LIVES ON
When you bought an Apple Macintosh computer in the e...
New
Small essay with thoughts on macOS vs. Linux:
I know @Exadra37 is just waiting around the corner to scream at me “I TOLD YOU SO!!!” but I...
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
Intensively researching Erlang books and additional resources on it, I have found that the topic of using Regular Expressions is either c...
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
Author Spotlight
Erin Dees
@undees
Welcome to our new author spotlight! We had the pleasure of chatting with Erin Dees, co-author of ...
New
Author Spotlight:
VM Brasseur
@vmbrasseur
We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
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
This is a very quick guide, you just need to:
Download LM Studio: https://lmstudio.ai/
Click on search
Type DeepSeek, then select the o...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /ruby
- /wasm
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /emacs
- /haskell
- /java
- /svelte
- /onivim
- /typescript
- /kotlin
- /crystal
- /c-plus-plus
- /tailwind
- /react
- /gleam
- /ocaml
- /elm
- /flutter
- /vscode
- /ash
- /html
- /opensuse
- /centos
- /php
- /deepseek
- /zig
- /scala
- /sublime-text
- /lisp
- /textmate
- /react-native
- /debian
- /nixos
- /agda
- /kubuntu
- /arch-linux
- /django
- /deno
- /ubuntu
- /revery
- /nodejs
- /spring
- /manjaro
- /diversity
- /lua
- /julia
- /markdown
- /slackware








