Make Code compatible with JDK 17

autograder-core/src/main/java/de/firemage/autograder/core/check/api/CollectionAddAll.java

@@ -3,10 +3,10 @@
 import de.firemage.autograder.core.LocalizedMessage;
 import de.firemage.autograder.core.ProblemType;
 import de.firemage.autograder.core.check.ExecutableCheck;
+import de.firemage.autograder.core.check.api.UseEnumValues.CtEnumFieldRead;
 import de.firemage.autograder.core.integrated.IntegratedCheck;
 import de.firemage.autograder.core.integrated.SpoonUtil;
 import de.firemage.autograder.core.integrated.StaticAnalysis;
-import de.firemage.autograder.core.check.api.UseEnumValues.CtEnumFieldRead;
 import spoon.reflect.code.CtBlock;
 import spoon.reflect.code.CtExpression;
 import spoon.reflect.code.CtForEach;
@@ -200,7 +200,7 @@ private void checkAddAll(CtForEach ctFor) {
 
             // handle edge case where the variable is implicitly cast in the invocation (Character in List, but char in iterable)
             List<CtTypeReference<?>> actualTypeArguments = ctInvocation.getTarget().getType().getActualTypeArguments();
-            if (!actualTypeArguments.isEmpty() && !ctFor.getVariable().getType().equals(actualTypeArguments.getFirst())) {
+            if (!actualTypeArguments.isEmpty() && !ctFor.getVariable().getType().equals(actualTypeArguments.get(0))) {
                 return;
             }
 

autograder-core/src/main/java/de/firemage/autograder/core/check/comment/UnnecessaryComment.java

@@ -42,7 +42,11 @@ private void checkComments(Collection<? extends CtComment> comments) {
     }
 
     private static boolean isStandaloneComment(CtComment ctComment) {
-        return ctComment.getParent() instanceof CtElement ctElement && !ctElement.getComments().contains(ctComment);
+        var parent = ctComment.getParent();
+        if (parent == null) {
+            return false;
+        }
+        return !parent.getComments().contains(ctComment);
     }
 
     @Override
@@ -71,7 +75,7 @@ public void process(CtElement element) {
                         .map(CtComment.class::cast)
                         .collect(Collectors.toCollection(ArrayList::new));
 
-                    followingComments.addFirst(ctComment);
+                    followingComments.add(0, ctComment);
 
                     checkComments(followingComments);
                     return;

autograder-core/src/main/java/de/firemage/autograder/core/check/oop/LeakedCollectionCheck.java

@@ -40,6 +40,7 @@
 import spoon.reflect.visitor.filter.TypeFilter;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -210,7 +211,9 @@ private static List<CtExpression<?>> findPreviousAssignee(CtVariableRead<?> ctVa
 
         boolean foundPreviousAssignment = false;
         CtStatement currentStatement = ctVariableRead.getParent(CtStatement.class);
-        for (CtStatement ctStatement : SpoonUtil.getEffectiveStatements(ctExecutable.getBody()).reversed()) {
+        var reversedStatements = new ArrayList<>(SpoonUtil.getEffectiveStatements(ctExecutable.getBody()));
+        Collections.reverse(reversedStatements);
+        for (CtStatement ctStatement : reversedStatements) {
             if (!foundPreviousAssignment) {
                 if (ctStatement == currentStatement) {
                     foundPreviousAssignment = true;
@@ -249,7 +252,7 @@ && isParameterOf(ctVariableDeclaration, ctExecutable)) {
             List<CtExpression<?>> previousAssignees = findPreviousAssignee(ctVariableRead);
 
             if (!previousAssignees.isEmpty()) {
-                return findParameterReference(previousAssignees.getFirst(), ctExecutable);
+                return findParameterReference(previousAssignees.get(0), ctExecutable);
             }
 
             return Option.some((CtParameter<?>) ctVariableDeclaration);
@@ -412,13 +415,11 @@ private <T> void checkCtType(CtType<T> ctType) {
                         ctTypeMember = fixRecordAccessor(ctRecord, ctMethod);
                     }
 
-                    switch (ctTypeMember) {
-                        case CtConstructor<?> ctConstructor -> checkCtExecutableAssign(ctConstructor);
-                        case CtMethod<?> ctMethod -> {
-                            checkCtExecutableReturn(ctMethod);
-                            checkCtExecutableAssign(ctMethod);
-                        }
-                        default -> {}
+                    if (ctTypeMember instanceof CtConstructor<?> ctConstructor) {
+                        checkCtExecutableAssign(ctConstructor);
+                    } else if (ctTypeMember instanceof CtMethod<?> ctMethod) {
+                        checkCtExecutableReturn(ctMethod);
+                        checkCtExecutableAssign(ctMethod);
                     }
                 }
             }

autograder-core/src/main/java/de/firemage/autograder/core/check/oop/MethodShouldBeStatic.java

@@ -22,7 +22,6 @@
 
 import java.util.Map;
 
-
 @ExecutableCheck(reportedProblems = { ProblemType.METHOD_SHOULD_BE_STATIC, ProblemType.METHOD_SHOULD_BE_STATIC_NOT_PUBLIC})
 public class MethodShouldBeStatic extends IntegratedCheck {
     /**
@@ -48,12 +47,14 @@ private boolean isThisTypeAccess(CtTargetedExpression<?, ?> ctTargetedExpression
 
         @Override
         public boolean matches(CtElement element) {
-            return switch (element) {
-                case CtFieldAccess<?> ctFieldAccess -> this.isThisTypeAccess(ctFieldAccess);
-                case CtInvocation<?> ctInvocation -> this.isThisTypeAccess(ctInvocation);
-                case CtExecutableReferenceExpression<?, ?> ctExecutableReferenceExpression -> this.isThisTypeAccess(ctExecutableReferenceExpression);
-                default -> false;
-            };
+            if (element instanceof CtFieldAccess<?> ctFieldAccess) {
+                return this.isThisTypeAccess(ctFieldAccess);
+            } else if (element instanceof CtInvocation<?> ctInvocation) {
+                return this.isThisTypeAccess(ctInvocation);
+            } else if (element instanceof CtExecutableReferenceExpression<?, ?> ctExecutableReferenceExpression) {
+                return this.isThisTypeAccess(ctExecutableReferenceExpression);
+            }
+            return false;
         }
     }
 

autograder-core/src/main/java/de/firemage/autograder/core/check/structure/DuplicateCode.java

@@ -34,7 +34,6 @@
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.SequencedSet;
 import java.util.Set;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
@@ -97,11 +96,11 @@ public void add(CtStatement ctStatement) {
         }
 
         public CtStatement getFirst() {
-            return this.statements.getFirst();
+            return this.statements.get(0);
         }
 
         public CtStatement getLast() {
-            return this.statements.getLast();
+            return this.statements.get(this.statements.size() - 1);
         }
 
         public List<CtStatement> statements() {
@@ -113,8 +112,8 @@ public Iterator<CtStatement> iterator() {
             return this.statements().iterator();
         }
 
-        private SequencedSet<CtVariable<?>> declaredVariables() {
-            SequencedSet<CtVariable<?>> declaredVariables = new LinkedHashSet<>();
+        private Set<CtVariable<?>> declaredVariables() {
+            Set<CtVariable<?>> declaredVariables = new LinkedHashSet<>();
 
             for (CtStatement ctStatement : this) {
                 if (ctStatement instanceof CtVariable<?> ctVariable) {

autograder-core/src/main/java/de/firemage/autograder/core/check/utils/Option.java

@@ -20,21 +20,25 @@ static <T> Option<T> none() {
     }
 
     default T unwrap() {
-        return switch (this) {
-            case Some<T> (var value) -> value;
-            case None<T> ignored -> throw new IllegalStateException("Expected Some value, but got None.");
-        };
+        if (this instanceof Some<T> someValue) {
+            return someValue.value;
+        } else if (this instanceof None<T>) {
+            throw new IllegalStateException("Expected Some value, but got None.");
+        }
+        throw new IllegalArgumentException();
     }
 
     default boolean isSome() {
         return this instanceof Some;
     }
 
     default <U> Option<U> map(Function<T, U> function) {
-        return switch (this) {
-            case Some<T>(var value) -> new Some<>(function.apply(value));
-            case None<T> ignored -> new None<>();
-        };
+	if (this instanceof Some<T> someValue) {
+            return new Some<>(function.apply(someValue.value));
+        } else if (this instanceof None<T>) {
+            return new None<>();
+        }
+         throw new IllegalArgumentException();
     }
 
     /**
@@ -43,17 +47,21 @@ default <U> Option<U> map(Function<T, U> function) {
      * @return the value or null
      */
     default T nullable() {
-        return switch (this) {
-            case Some<T>(var value) -> value;
-            case None<T> ignored -> null;
-        };
+        if (this instanceof Some<T> someValue) {
+            return someValue.value;
+        } else if (this instanceof None<T>) {
+            return null;
+        }
+        throw new IllegalArgumentException();
     }
 
     default Stream<T> stream() {
-        return switch (this) {
-            case Some<T>(var value) -> Stream.of(value);
-            case None<T> ignored -> Stream.empty();
-        };
+        if (this instanceof Some<T> someValue) {
+            return Stream.of(someValue.value);
+        } else if (this instanceof None<T>) {
+            return Stream.empty();
+        }
+        throw new IllegalArgumentException();
     }
 
     @Override

autograder-core/src/main/java/de/firemage/autograder/core/integrated/SpoonUtil.java

@@ -8,7 +8,6 @@
 import de.firemage.autograder.core.integrated.evaluator.fold.FoldUtils;
 import de.firemage.autograder.core.integrated.evaluator.fold.InlineVariableRead;
 import de.firemage.autograder.core.integrated.evaluator.fold.RemoveRedundantCasts;
-import org.apache.commons.io.FilenameUtils;
 import spoon.processing.FactoryAccessor;
 import spoon.reflect.CtModel;
 import spoon.reflect.code.BinaryOperatorKind;
@@ -55,6 +54,8 @@
 import spoon.reflect.reference.CtTypeReference;
 import spoon.reflect.reference.CtVariableReference;
 
+import org.apache.commons.io.FilenameUtils;
+
 import java.io.File;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
@@ -1176,7 +1177,7 @@ private static <T> int referenceIndexOf(List<T> list, T element) {
      */
     public static Optional<CtStatement> getPreviousStatement(CtStatement ctStatement) {
         List<CtStatement> previousStatements = getPreviousStatements(ctStatement);
-        return previousStatements.isEmpty() ? Optional.empty() : Optional.of(previousStatements.getLast());
+        return previousStatements.isEmpty() ? Optional.empty() : Optional.of(previousStatements.get(previousStatements.size() - 1));
     }
 
     public static List<CtStatement> getPreviousStatements(CtStatement ctStatement) {

autograder-core/src/main/java/de/firemage/autograder/core/integrated/UsesFinder.java

@@ -40,7 +40,7 @@
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
-import java.util.SequencedSet;
+import java.util.Set;
 import java.util.stream.Stream;
 
 /**
@@ -80,13 +80,16 @@ private static UsesFinder getFor(FactoryAccessor factoryAccessor) {
      */
     @SuppressWarnings("rawtypes")
     public static CtElementStream<CtElement> getAllUses(CtNamedElement element) {
-        return switch (element) {
-            case CtVariable variable -> UsesFinder.variableUses(variable).asUntypedStream();
-            case CtTypeParameter typeParameter -> UsesFinder.typeParameterUses(typeParameter).asUntypedStream();
-            case CtExecutable executable -> UsesFinder.executableUses(executable).asUntypedStream();
-            case CtType type -> UsesFinder.typeUses(type).asUntypedStream();
-            default -> throw new IllegalArgumentException("Unsupported element: " + element.getClass().getName());
-        };
+        if (element instanceof CtVariable variable) {
+            return UsesFinder.variableUses(variable).asUntypedStream();
+        } else if (element instanceof CtTypeParameter typeParameter) {
+            return UsesFinder.typeParameterUses(typeParameter).asUntypedStream();
+        } else if (element instanceof CtExecutable executable) {
+            return UsesFinder.executableUses(executable).asUntypedStream();
+        } else if (element instanceof CtType type) {
+            return UsesFinder.typeUses(type).asUntypedStream();
+        }
+        throw new IllegalArgumentException("Unsupported element: " + element.getClass().getName());
     }
 
     public static CtElementStream<CtVariableAccess<?>> variableUses(CtVariable<?> variable) {
@@ -161,8 +164,8 @@ private static class UsesScanner extends CtScanner {
         private final Map<CtTypeParameter, List<CtTypeParameterReference>> typeParameterUses = new IdentityHashMap<>();
         private final Map<CtExecutable, List<CtElement>> executableUses = new IdentityHashMap<>();
         private final Map<CtType, List<CtTypeReference>> typeUses = new IdentityHashMap<>();
-        private final Map<CtType, SequencedSet<CtType>> subtypes = new IdentityHashMap<>();
-        private final Map<CtType, SequencedSet<CtType>> supertypes = new IdentityHashMap<>();
+        private final Map<CtType, Set<CtType>> subtypes = new IdentityHashMap<>();
+        private final Map<CtType, Set<CtType>> supertypes = new IdentityHashMap<>();
 
         // Caches the current instanceof pattern variables, since Spoon doesn't track them yet
         // We are conservative: A pattern introduces a variable until the end of the current block

autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralElement.java

@@ -12,11 +12,11 @@ public boolean equals(Object otherObject) {
         if (this == otherObject) {
             return true;
         }
-        if (!(otherObject instanceof StructuralElement(var otherElement))) {
+        if (!(otherObject instanceof StructuralElement<?> otherStructuralElement)) {
             return false;
         }
 
-        return StructuralEqualsVisitor.equals(this.element, otherElement);
+        return StructuralEqualsVisitor.equals(this.element, otherStructuralElement.element);
     }
 
     @Override

autograder-core/src/main/java/de/firemage/autograder/core/integrated/structure/StructuralEqualsVisitor.java

@@ -19,7 +19,6 @@
 import spoon.support.visitor.equals.EqualsVisitor;
 
 import java.util.LinkedHashSet;
-import java.util.SequencedSet;
 import java.util.Set;
 import java.util.function.Predicate;
 import java.util.function.UnaryOperator;
@@ -32,7 +31,7 @@ public final class StructuralEqualsVisitor extends EqualsVisitor {
         CtRole.COMMENT, CtRole.COMMENT_CONTENT, CtRole.COMMENT_TAG, CtRole.COMMENT_TYPE
     );
 
-    private final SequencedSet<Difference> differences;
+    private final Set<Difference> differences;
 
     public record Difference(CtRole role, Object left, Object right) {}
 
@@ -218,7 +217,7 @@ protected boolean fail(CtRole role, Object element, Object other) {
      *
      * @return the differences
      */
-    public SequencedSet<Difference> differences() {
+    public Set<Difference> differences() {
         return new LinkedHashSet<>(this.differences);
     }
 }

pom.xml

@@ -38,7 +38,7 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 
-        <java.version>21</java.version>
+        <java.version>17</java.version>
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <maven.compiler.release>${java.version}</maven.compiler.release>