From ca7e278e930c277c704c15072b12073400997d57 Mon Sep 17 00:00:00 2001
From: Colin DAMON <cdamon@ippon.fr>
Date: Fri, 18 Jun 2021 10:09:50 +0200
Subject: [PATCH] Java memoizers implementation
---
.gitlab-ci.yml | 1 +
java-memoizers/.gitlab-ci.yml | 11 ++++
java-memoizers/pom.xml | 29 +++++++++
java-memoizers/readme.md | 9 +++
.../java/fr/craft/memoizer/Memoizers.java | 42 +++++++++++++
.../java/fr/craft/memoizer/MemoizersTest.java | 63 +++++++++++++++++++
readme.md | 1 +
7 files changed, 156 insertions(+)
create mode 100644 java-memoizers/.gitlab-ci.yml
create mode 100644 java-memoizers/pom.xml
create mode 100644 java-memoizers/readme.md
create mode 100644 java-memoizers/src/main/java/fr/craft/memoizer/Memoizers.java
create mode 100644 java-memoizers/src/test/java/fr/craft/memoizer/MemoizersTest.java
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 97907d02..0c16d1af 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -39,3 +39,4 @@ include:
- local: "/java-monades/.gitlab-ci.yml"
- local: "/java-diamond/.gitlab-ci.yml"
- local: "/diamond-ts/.gitlab-ci.yml"
+ - local: "/java-memoizers/.gitlab-ci.yml"
diff --git a/java-memoizers/.gitlab-ci.yml b/java-memoizers/.gitlab-ci.yml
new file mode 100644
index 00000000..bf70e5c6
--- /dev/null
+++ b/java-memoizers/.gitlab-ci.yml
@@ -0,0 +1,11 @@
+package-java-memoizers:
+ variables:
+ PROJECT_FOLDER: "java-memoizers"
+ extends: .java
+ only:
+ refs:
+ - master
+ - merge_requests
+ changes:
+ - ".gitlab-common-ci.yml"
+ - "java-memoizers/**/*"
diff --git a/java-memoizers/pom.xml b/java-memoizers/pom.xml
new file mode 100644
index 00000000..04edddc2
--- /dev/null
+++ b/java-memoizers/pom.xml
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+
+ <parent>
+ <version>1.0.0</version>
+ <groupId>fr.ippon.kata</groupId>
+ <artifactId>java-parent</artifactId>
+ <relativePath>../java-parent</relativePath>
+ </parent>
+
+ <version>1.0.0-SNAPSHOT</version>
+ <artifactId>java-memoizers</artifactId>
+
+ <name>JavaMemoizers</name>
+
+ <developers>
+ <developer>
+ <email>arey@ippon.fr</email>
+ <name>Anthont REY</name>
+ </developer>
+ <developer>
+ <email>cdamon@ippon.fr</email>
+ <name>Colin DAMON</name>
+ </developer>
+ </developers>
+</project>
diff --git a/java-memoizers/readme.md b/java-memoizers/readme.md
new file mode 100644
index 00000000..bd80d3bf
--- /dev/null
+++ b/java-memoizers/readme.md
@@ -0,0 +1,9 @@
+# Java memoizer
+
+Implémentation de memoizers en Java
+
+- **Auteurs** : Anthony REY et Colin DAMON
+- **Date** : 18/06/2021
+- **Langage** : Java
+- **Niveau** : Enervé
+- **Replay** : [Twitch](https://www.twitch.tv/videos/1059837117)
diff --git a/java-memoizers/src/main/java/fr/craft/memoizer/Memoizers.java b/java-memoizers/src/main/java/fr/craft/memoizer/Memoizers.java
new file mode 100644
index 00000000..52c14a61
--- /dev/null
+++ b/java-memoizers/src/main/java/fr/craft/memoizer/Memoizers.java
@@ -0,0 +1,42 @@
+package fr.craft.memoizer;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public final class Memoizers {
+
+ private Memoizers() {}
+
+ public static <Result> Supplier<Result> of(Supplier<Result> supplier) {
+ return () -> of(dummy -> supplier.get()).apply(null);
+ }
+
+ public static <Input, Result> Function<Input, Result> of(Function<Input, Result> function) {
+ return new MemoizedFunction<>(function);
+ }
+
+ private static class MemoizedFunction<Input, Result> implements Function<Input, Result> {
+
+ private final Function<Input, Result> function;
+ private final Map<MemoizedInput<Input>, MemoizedResult<Result>> results = new ConcurrentHashMap<>();
+
+ public MemoizedFunction(Function<Input, Result> function) {
+ this.function = function;
+ }
+
+ @Override
+ public Result apply(Input input) {
+ return results.computeIfAbsent(new MemoizedInput<>(input), this::toMemoizedResult).result();
+ }
+
+ private MemoizedResult<Result> toMemoizedResult(MemoizedInput<Input> input) {
+ return new MemoizedResult<>(function.apply(input.input()));
+ }
+
+ private static record MemoizedInput<Input>(Input input) {}
+
+ private static record MemoizedResult<Result>(Result result) {}
+ }
+}
diff --git a/java-memoizers/src/test/java/fr/craft/memoizer/MemoizersTest.java b/java-memoizers/src/test/java/fr/craft/memoizer/MemoizersTest.java
new file mode 100644
index 00000000..856cca95
--- /dev/null
+++ b/java-memoizers/src/test/java/fr/craft/memoizer/MemoizersTest.java
@@ -0,0 +1,63 @@
+package fr.craft.memoizer;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import org.junit.jupiter.api.Test;
+
+class MemoizersTest {
+
+ @Test
+ void shouldGetFunctionResult() {
+ Function<Double, Double> memoizer = Memoizers.of(d -> d * d);
+
+ assertThat(memoizer.apply(2D)).isEqualTo(4D);
+ }
+
+ @Test
+ void shouldMemoizeFunctionResult() {
+ AtomicInteger result = new AtomicInteger();
+
+ Function<Object, Integer> memoizer = Memoizers.of(d -> result.incrementAndGet());
+
+ assertThat(memoizer.apply(1)).isEqualTo(memoizer.apply(1));
+ assertThat(memoizer.apply(1)).isNotEqualTo(memoizer.apply(2));
+ }
+
+ @Test
+ void shouldMemoizeNullResult() {
+ NullFactory factory = new NullFactory();
+ Function<Object, String> memoizer = Memoizers.of(factory);
+
+ memoizer.apply(1);
+ memoizer.apply(1);
+
+ assertThat(factory.callsCount()).isEqualTo(1);
+ assertThat(memoizer.apply(1)).isNull();
+ }
+
+ @Test
+ void shouldMemoizeSupplier() {
+ Supplier<String> supplier = Memoizers.of(() -> "Pouet");
+
+ assertThat(supplier.get()).isEqualTo("Pouet");
+ }
+
+ private static class NullFactory implements Function<Object, String> {
+
+ private final AtomicInteger callsCount = new AtomicInteger();
+
+ public int callsCount() {
+ return callsCount.get();
+ }
+
+ @Override
+ public String apply(Object input) {
+ callsCount.incrementAndGet();
+
+ return null;
+ }
+ }
+}
diff --git a/readme.md b/readme.md
index 2da8b836..92959e14 100644
--- a/readme.md
+++ b/readme.md
@@ -86,6 +86,7 @@ Un kata de code est un petit exercice pensé pour s'entrainer jusqu'à maitriser
- [Concurrence en Java](/java-concurrence)
- [Try monade](/try-monade)
+- [Memoizers](/java-memoizers)
### Bon Chance
--
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