ArchRule: Prevent ForEach (as not functional)

pom.xml

@@ -59,6 +59,7 @@
     <autograder.version>0.6.2</autograder.version>
     <jgit.version>7.0.0.202409031743-r</jgit.version>
     <junit.version>5.11.1</junit.version>
+    <archunit.version>1.3.0</archunit.version>
     <versions-maven-plugin.version>2.17.1</versions-maven-plugin.version>
   </properties>
 
@@ -93,6 +94,17 @@
       <artifactId>okhttp</artifactId>
       <version>${okhttp.version}</version>
     </dependency>
+    <dependency>
+      <groupId>com.tngtech.archunit</groupId>
+      <artifactId>archunit</artifactId>
+      <version>${archunit.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.tngtech.archunit</groupId>
+      <artifactId>archunit-junit5</artifactId>
+      <version>${archunit.version}</version>
+    </dependency>
 
     <!-- Autograder -->
     <dependency>

src/main/java/edu/kit/kastel/sdq/artemis4j/grading/AnnotationMerger.java

@@ -62,7 +62,7 @@ static List<Annotation> mergeAnnotations(
             }
 
             // Further partition the annotations by their remaining classifiers:
-            annotationsForClassifier.stream()
+            Map<String, List<Annotation>> map = annotationsForClassifier.stream()
                     .collect(Collectors.groupingBy(
                             annotation -> {
                                 List<String> classifiers = annotation.getClassifiers();
@@ -75,11 +75,11 @@ static List<Annotation> mergeAnnotations(
                                 }
                             },
                             LinkedHashMap::new,
-                            Collectors.toList()))
-                    .values()
-                    .stream()
-                    .flatMap(list -> merge(list, targetNumberOfAnnotations, locale).stream())
-                    .forEach(result::add);
+                            Collectors.toList()));
+
+            for (List<Annotation> list : map.values()) {
+                result.addAll(merge(list, targetNumberOfAnnotations, locale));
+            }
         }
 
         return result;

src/main/java/edu/kit/kastel/sdq/artemis4j/grading/ClonedProgrammingSubmission.java

@@ -1,7 +1,6 @@
 /* Licensed under EPL-2.0 2024. */
 package edu.kit.kastel.sdq.artemis4j.grading;
 
-import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -112,7 +111,13 @@ public void close() throws ArtemisClientException {
 
     private static void deleteDirectory(Path path) throws IOException {
         try (var dirStream = Files.walk(path)) {
-            dirStream.map(Path::toFile).sorted(Comparator.reverseOrder()).forEach(File::delete);
+            var filesInDirectory = dirStream
+                    .map(Path::toFile)
+                    .sorted(Comparator.reverseOrder())
+                    .toList();
+            for (var file : filesInDirectory) {
+                file.delete();
+            }
         }
     }
 }

src/test/java/edu/kit/kastel/sdq/artemis4j/ArchitectureTest.java

@@ -0,0 +1,28 @@
+/* Licensed under EPL-2.0 2024. */
+package edu.kit.kastel.sdq.artemis4j;
+
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.*;
+
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+
+import com.tngtech.archunit.junit.AnalyzeClasses;
+import com.tngtech.archunit.junit.ArchTest;
+import com.tngtech.archunit.lang.ArchRule;
+
+@AnalyzeClasses(packages = "edu.kit.kastel.sdq.artemis4j")
+class ArchitectureTest {
+
+    @ArchTest
+    static final ArchRule noForEachInCollectionsOrStream = noClasses()
+            .should()
+            .callMethod(Stream.class, "forEach", Consumer.class)
+            .orShould()
+            .callMethod(Stream.class, "forEachOrdered", Consumer.class)
+            .orShould()
+            .callMethod(List.class, "forEach", Consumer.class)
+            .orShould()
+            .callMethod(List.class, "forEachOrdered", Consumer.class)
+            .because("Lambdas should be functional. ForEach is typically used for side-effects.");
+}