Use immutable collection factory methods

marcphilipp · marcphilipp · commit 64de9f0bbe97 · 2025-05-24T19:45:29.000+02:00
diff --git a/junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/extension/MutableExtensionRegistry.java b/junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/extension/MutableExtensionRegistry.java
@@ -18,8 +18,6 @@
 import java.lang.reflect.Member;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -53,13 +51,14 @@ public class MutableExtensionRegistry implements ExtensionRegistry, ExtensionReg
 
 	private static final Logger logger = LoggerFactory.getLogger(MutableExtensionRegistry.class);
 
-	private static final List<Extension> DEFAULT_STATELESS_EXTENSIONS = Collections.unmodifiableList(Arrays.asList(//
+	private static final List<Extension> DEFAULT_STATELESS_EXTENSIONS = List.of( //
 		new DisabledCondition(), //
 		new AutoCloseExtension(), //
 		new TimeoutExtension(), //
 		new RepeatedTestExtension(), //
 		new TestInfoParameterResolver(), //
-		new TestReporterParameterResolver()));
+		new TestReporterParameterResolver() //
+	);
 
 	/**
 	 * Factory for creating and populating a new root registry with the default
diff --git a/junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/extension/TimeoutDurationParser.java b/junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/extension/TimeoutDurationParser.java
@@ -22,8 +22,6 @@
 import static java.util.regex.Pattern.UNICODE_CASE;
 
 import java.time.format.DateTimeParseException;
-import java.util.Collections;
-import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
@@ -37,19 +35,16 @@ class TimeoutDurationParser {
 
 	private static final Pattern PATTERN = Pattern.compile("([1-9]\\d*) ?((?:[nμm]?s)|m|h|d)?",
 		CASE_INSENSITIVE | UNICODE_CASE);
-	private static final Map<String, TimeUnit> UNITS_BY_ABBREVIATION;
 
-	static {
-		Map<String, TimeUnit> unitsByAbbreviation = new HashMap<>();
-		unitsByAbbreviation.put("ns", NANOSECONDS);
-		unitsByAbbreviation.put("μs", MICROSECONDS);
-		unitsByAbbreviation.put("ms", MILLISECONDS);
-		unitsByAbbreviation.put("s", SECONDS);
-		unitsByAbbreviation.put("m", MINUTES);
-		unitsByAbbreviation.put("h", HOURS);
-		unitsByAbbreviation.put("d", DAYS);
-		UNITS_BY_ABBREVIATION = Collections.unmodifiableMap(unitsByAbbreviation);
-	}
+	private static final Map<String, TimeUnit> UNITS_BY_ABBREVIATION = Map.of( //
+		"ns", NANOSECONDS, //
+		"μs", MICROSECONDS, //
+		"ms", MILLISECONDS, //
+		"s", SECONDS, //
+		"m", MINUTES, //
+		"h", HOURS, //
+		"d", DAYS //
+	);
 
 	TimeoutDuration parse(CharSequence text) throws DateTimeParseException {
 		Matcher matcher = PATTERN.matcher(text);
diff --git a/junit-jupiter-params/src/main/java/org/junit/jupiter/params/ResolverFacade.java b/junit-jupiter-params/src/main/java/org/junit/jupiter/params/ResolverFacade.java
@@ -11,7 +11,6 @@
 package org.junit.jupiter.params;
 
 import static java.lang.System.lineSeparator;
-import static java.util.Collections.unmodifiableList;
 import static java.util.Objects.requireNonNull;
 import static java.util.stream.Collectors.joining;
 import static java.util.stream.Collectors.toList;
@@ -584,7 +583,7 @@ public Optional<ParameterDeclaration> getFirst() {
 
 		@Override
 		public List<ParameterDeclaration> getAll() {
-			return unmodifiableList(new ArrayList<>(this.declarationsByIndex.values()));
+			return List.copyOf(this.declarationsByIndex.values());
 		}
 
 		@Override
diff --git a/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/ConversionSupport.java b/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/ConversionSupport.java
@@ -10,8 +10,6 @@
 
 package org.junit.platform.commons.support.conversion;
 
-import static java.util.Arrays.asList;
-import static java.util.Collections.unmodifiableList;
 import static org.apiguardian.api.API.Status.EXPERIMENTAL;
 import static org.junit.platform.commons.util.ReflectionUtils.getWrapperType;
 
@@ -31,7 +29,7 @@
 @API(status = EXPERIMENTAL, since = "1.11")
 public final class ConversionSupport {
 
-	private static final List<StringToObjectConverter> stringToObjectConverters = unmodifiableList(asList( //
+	private static final List<StringToObjectConverter> stringToObjectConverters = List.of( //
 		new StringToBooleanConverter(), //
 		new StringToCharacterConverter(), //
 		new StringToNumberConverter(), //
@@ -40,7 +38,7 @@ public final class ConversionSupport {
 		new StringToJavaTimeConverter(), //
 		new StringToCommonJavaTypesConverter(), //
 		new FallbackStringToObjectConverter() //
-	));
+	);
 
 	private ConversionSupport() {
 		/* no-op */
diff --git a/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/StringToCommonJavaTypesConverter.java b/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/StringToCommonJavaTypesConverter.java
@@ -10,8 +10,6 @@
 
 package org.junit.platform.commons.support.conversion;
 
-import static java.util.Collections.unmodifiableMap;
-
 import java.io.File;
 import java.net.MalformedURLException;
 import java.net.URI;
@@ -20,7 +18,6 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.Currency;
-import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
 import java.util.UUID;
@@ -30,25 +27,19 @@
 
 class StringToCommonJavaTypesConverter implements StringToObjectConverter {
 
-	private static final Map<Class<?>, Function<String, ?>> CONVERTERS;
-
-	static {
-		Map<Class<?>, Function<String, ?>> converters = new HashMap<>();
-
+	private static final Map<Class<?>, Function<String, ?>> CONVERTERS = Map.of( //
 		// java.io and java.nio
-		converters.put(File.class, File::new);
-		converters.put(Charset.class, Charset::forName);
-		converters.put(Path.class, Paths::get);
+		File.class, File::new, //
+		Charset.class, Charset::forName, //
+		Path.class, Paths::get,
 		// java.net
-		converters.put(URI.class, URI::create);
-		converters.put(URL.class, StringToCommonJavaTypesConverter::toURL);
+		URI.class, URI::create, //
+		URL.class, StringToCommonJavaTypesConverter::toURL,
 		// java.util
-		converters.put(Currency.class, Currency::getInstance);
-		converters.put(Locale.class, Locale::new);
-		converters.put(UUID.class, UUID::fromString);
-
-		CONVERTERS = unmodifiableMap(converters);
-	}
+		Currency.class, Currency::getInstance, //
+		Locale.class, Locale::new, //
+		UUID.class, UUID::fromString //
+	);
 
 	@Override
 	public boolean canConvertTo(Class<?> targetType) {
diff --git a/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/StringToJavaTimeConverter.java b/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/StringToJavaTimeConverter.java
@@ -10,7 +10,7 @@
 
 package org.junit.platform.commons.support.conversion;
 
-import static java.util.Collections.unmodifiableMap;
+import static java.util.Map.entry;
 
 import java.time.Duration;
 import java.time.Instant;
@@ -26,33 +26,29 @@
 import java.time.ZoneId;
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Function;
 
 import org.junit.platform.commons.util.Preconditions;
 
 class StringToJavaTimeConverter implements StringToObjectConverter {
 
-	private static final Map<Class<?>, Function<String, ?>> CONVERTERS;
-	static {
-		Map<Class<?>, Function<String, ?>> converters = new HashMap<>();
-		converters.put(Duration.class, Duration::parse);
-		converters.put(Instant.class, Instant::parse);
-		converters.put(LocalDate.class, LocalDate::parse);
-		converters.put(LocalDateTime.class, LocalDateTime::parse);
-		converters.put(LocalTime.class, LocalTime::parse);
-		converters.put(MonthDay.class, MonthDay::parse);
-		converters.put(OffsetDateTime.class, OffsetDateTime::parse);
-		converters.put(OffsetTime.class, OffsetTime::parse);
-		converters.put(Period.class, Period::parse);
-		converters.put(Year.class, Year::parse);
-		converters.put(YearMonth.class, YearMonth::parse);
-		converters.put(ZonedDateTime.class, ZonedDateTime::parse);
-		converters.put(ZoneId.class, ZoneId::of);
-		converters.put(ZoneOffset.class, ZoneOffset::of);
-		CONVERTERS = unmodifiableMap(converters);
-	}
+	private static final Map<Class<?>, Function<String, ?>> CONVERTERS = Map.ofEntries( //
+		entry(Duration.class, Duration::parse), //
+		entry(Instant.class, Instant::parse), //
+		entry(LocalDate.class, LocalDate::parse), //
+		entry(LocalDateTime.class, LocalDateTime::parse), //
+		entry(LocalTime.class, LocalTime::parse), //
+		entry(MonthDay.class, MonthDay::parse), //
+		entry(OffsetDateTime.class, OffsetDateTime::parse), //
+		entry(OffsetTime.class, OffsetTime::parse), //
+		entry(Period.class, Period::parse), //
+		entry(Year.class, Year::parse), //
+		entry(YearMonth.class, YearMonth::parse), //
+		entry(ZonedDateTime.class, ZonedDateTime::parse), //
+		entry(ZoneId.class, ZoneId::of), //
+		entry(ZoneOffset.class, ZoneOffset::of) //
+	);
 
 	@Override
 	public boolean canConvertTo(Class<?> targetType) {
diff --git a/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/StringToNumberConverter.java b/junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/StringToNumberConverter.java
@@ -10,34 +10,28 @@
 
 package org.junit.platform.commons.support.conversion;
 
-import static java.util.Collections.unmodifiableMap;
-
 import java.math.BigDecimal;
 import java.math.BigInteger;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Function;
 
 import org.junit.platform.commons.util.Preconditions;
 
 class StringToNumberConverter implements StringToObjectConverter {
 
-	private static final Map<Class<?>, Function<String, ?>> CONVERTERS;
-	static {
-		Map<Class<?>, Function<String, ?>> converters = new HashMap<>();
-		converters.put(Byte.class, Byte::decode);
-		converters.put(Short.class, Short::decode);
-		converters.put(Integer.class, Integer::decode);
-		converters.put(Long.class, Long::decode);
-		converters.put(Float.class, Float::valueOf);
-		converters.put(Double.class, Double::valueOf);
+	private static final Map<Class<?>, Function<String, ?>> CONVERTERS = Map.of( //
+		Byte.class, Byte::decode, //
+		Short.class, Short::decode, //
+		Integer.class, Integer::decode, //
+		Long.class, Long::decode, //
+		Float.class, Float::valueOf, //
+		Double.class, Double::valueOf, //
 		// Technically, BigInteger and BigDecimal constructors are covered by
 		// FallbackStringToObjectConverter, but we have explicit conversion
 		// configured for them anyway.
-		converters.put(BigInteger.class, BigInteger::new);
-		converters.put(BigDecimal.class, BigDecimal::new);
-		CONVERTERS = unmodifiableMap(converters);
-	}
+		BigInteger.class, BigInteger::new, //
+		BigDecimal.class, BigDecimal::new //
+	);
 
 	@Override
 	public boolean canConvertTo(Class<?> targetType) {
diff --git a/junit-platform-commons/src/main/java/org/junit/platform/commons/util/AnnotationUtils.java b/junit-platform-commons/src/main/java/org/junit/platform/commons/util/AnnotationUtils.java
@@ -25,7 +25,6 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Parameter;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -295,7 +294,7 @@ public static <A extends Annotation> List<A> findRepeatableAnnotations(@Nullable
 		Set<A> found = new LinkedHashSet<>(16);
 		findRepeatableAnnotations(element, annotationType, containerType, inherited, found, new HashSet<>(16));
 		// unmodifiable since returned from public, non-internal method(s)
-		return Collections.unmodifiableList(new ArrayList<>(found));
+		return List.copyOf(found);
 	}
 
 	private static <A extends Annotation> void findRepeatableAnnotations(AnnotatedElement element,
diff --git a/junit-platform-commons/src/main/java/org/junit/platform/commons/util/ExceptionUtils.java b/junit-platform-commons/src/main/java/org/junit/platform/commons/util/ExceptionUtils.java
@@ -171,7 +171,7 @@ public static List<Throwable> findNestedThrowables(Throwable rootThrowable) {
 			}
 		}
 
-		return Collections.unmodifiableList(new ArrayList<>(visited));
+		return List.copyOf(visited);
 	}
 
 }
diff --git a/junit-platform-commons/src/main/java/org/junit/platform/commons/util/ReflectionUtils.java b/junit-platform-commons/src/main/java/org/junit/platform/commons/util/ReflectionUtils.java
@@ -1150,7 +1150,7 @@ public static List<Class<?>> findNestedClasses(Class<?> clazz, Predicate<Class<?
 			candidates.add(nestedClass);
 			return true;
 		});
-		return Collections.unmodifiableList(new ArrayList<>(candidates));
+		return List.copyOf(candidates);
 	}
 
 	/**
diff --git a/junit-platform-engine/src/main/java/org/junit/platform/engine/TestTag.java b/junit-platform-engine/src/main/java/org/junit/platform/engine/TestTag.java
@@ -14,9 +14,6 @@
 
 import java.io.Serial;
 import java.io.Serializable;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.HashSet;
 import java.util.Objects;
 import java.util.Set;
 
@@ -54,8 +51,7 @@ public final class TestTag implements Serializable {
 	 * <li>{@code !}: <em>exclamation point</em></li>
 	 * </ul>
 	 */
-	public static final Set<String> RESERVED_CHARACTERS = Collections.unmodifiableSet(
-		new HashSet<>(Arrays.asList(",", "(", ")", "&", "|", "!")));
+	public static final Set<String> RESERVED_CHARACTERS = Set.of(",", "(", ")", "&", "|", "!");
 
 	/**
 	 * Determine if the supplied tag name is valid with regard to the supported
diff --git a/junit-platform-engine/src/main/java/org/junit/platform/engine/support/descriptor/CompositeTestSource.java b/junit-platform-engine/src/main/java/org/junit/platform/engine/support/descriptor/CompositeTestSource.java
@@ -10,11 +10,9 @@
 
 package org.junit.platform.engine.support.descriptor;
 
-import static java.util.Collections.unmodifiableList;
 import static org.apiguardian.api.API.Status.STABLE;
 
 import java.io.Serial;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
@@ -57,7 +55,7 @@ public static CompositeTestSource from(Collection<? extends TestSource> sources)
 	private CompositeTestSource(Collection<? extends TestSource> sources) {
 		Preconditions.notEmpty(sources, "TestSource collection must not be null or empty");
 		Preconditions.containsNoNullElements(sources, "individual TestSources must not be null");
-		this.sources = unmodifiableList(new ArrayList<>(sources));
+		this.sources = List.copyOf(sources);
 	}
 
 	/**
diff --git a/junit-platform-launcher/src/main/java/org/junit/platform/launcher/core/ClasspathAlignmentChecker.java b/junit-platform-launcher/src/main/java/org/junit/platform/launcher/core/ClasspathAlignmentChecker.java
@@ -10,11 +10,9 @@
 
 package org.junit.platform.launcher.core;
 
-import static java.util.Collections.unmodifiableList;
 import static java.util.Comparator.comparing;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -33,7 +31,7 @@
 class ClasspathAlignmentChecker {
 
 	// VisibleForTesting
-	static final List<String> WELL_KNOWN_PACKAGES = unmodifiableList(Arrays.asList( //
+	static final List<String> WELL_KNOWN_PACKAGES = List.of( //
 		"org.junit.jupiter.api", //
 		"org.junit.jupiter.engine", //
 		"org.junit.jupiter.migrationsupport", //
@@ -49,7 +47,7 @@ class ClasspathAlignmentChecker {
 		"org.junit.platform.suite.engine", //
 		"org.junit.platform.testkit", //
 		"org.junit.vintage.engine" //
-	));
+	);
 
 	static Optional<JUnitException> check(LinkageError error) {
 		ClassLoader classLoader = ClassLoaderUtils.getClassLoader(ClasspathAlignmentChecker.class);
diff --git a/junit-platform-launcher/src/main/java/org/junit/platform/launcher/listeners/discovery/CompositeLauncherDiscoveryListener.java b/junit-platform-launcher/src/main/java/org/junit/platform/launcher/listeners/discovery/CompositeLauncherDiscoveryListener.java
@@ -12,8 +12,6 @@
 
 import static org.junit.platform.commons.util.CollectionUtils.forEachInReverseOrder;
 
-import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 import org.junit.platform.engine.DiscoveryIssue;
@@ -33,7 +31,7 @@ class CompositeLauncherDiscoveryListener implements LauncherDiscoveryListener {
 	private final List<LauncherDiscoveryListener> listeners;
 
 	CompositeLauncherDiscoveryListener(List<LauncherDiscoveryListener> listeners) {
-		this.listeners = Collections.unmodifiableList(new ArrayList<>(listeners));
+		this.listeners = List.copyOf(listeners);
 	}
 
 	@Override
diff --git a/junit-platform-launcher/src/main/java/org/junit/platform/launcher/listeners/session/CompositeLauncherSessionListener.java b/junit-platform-launcher/src/main/java/org/junit/platform/launcher/listeners/session/CompositeLauncherSessionListener.java
diff --git a/junit-platform-reporting/src/main/java/org/junit/platform/reporting/legacy/xml/XmlReportWriter.java b/junit-platform-reporting/src/main/java/org/junit/platform/reporting/legacy/xml/XmlReportWriter.java

Original file line number	Diff line number	Diff line change
`@@ -171,7 +171,7 @@ public static List<Throwable> findNestedThrowables(Throwable rootThrowable) {`
`171`	`171`	`}`
`172`	`172`	`}`
`173`	`173`
`174`		`- return Collections.unmodifiableList(new ArrayList<>(visited));`
	`174`	`+ return List.copyOf(visited);`
`175`	`175`	`}`
`176`	`176`
`177`	`177`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1150,7 +1150,7 @@ public static List<Class<?>> findNestedClasses(Class<?> clazz, Predicate<Class<?`
`1150`	`1150`	`candidates.add(nestedClass);`
`1151`	`1151`	`return true;`
`1152`	`1152`	`});`
`1153`		`- return Collections.unmodifiableList(new ArrayList<>(candidates));`
	`1153`	`+ return List.copyOf(candidates);`
`1154`	`1154`	`}`
`1155`	`1155`
`1156`	`1156`	`/**`