Replace Collectors.toList() with Stream.toList()

Modernize stream collection operations by replacing Collectors.toList()
with Stream.toList() introduced in Java 16.

Changes:
- 17 files updated across multiple modules
- Removed unused Collectors import statements where applicable
- Retained Collectors import where joining() or toCollection() is used

Motivation:
- Conciseness: stream.toList() is shorter and more readable
- Performance: Avoids creating an intermediate Collector object
- Immutability: toList() returns an unmodifiable list
- Modern Java: Aligns with Java 16+ idioms since the project requires Java 17

Signed-off-by: Eunseo Song <[email protected]>

Author: eunseo9311

initializr-actuator/src/main/java/io/spring/initializr/actuate/stat/ProjectRequestDocumentFactory.java

@@ -20,7 +20,6 @@
 import java.util.List;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.actuate.stat.ProjectRequestDocument.ClientInformation;
 import io.spring.initializr.actuate.stat.ProjectRequestDocument.DependencyInformation;
@@ -90,11 +89,11 @@ public ProjectRequestDocument createDocument(ProjectRequestEvent event) {
 		List<String> dependencies = new ArrayList<>(request.getDependencies());
 		List<String> validDependencies = dependencies.stream()
 			.filter((id) -> metadata.getDependencies().get(id) != null)
-			.collect(Collectors.toList());
+			.toList();
 		document.setDependencies(new DependencyInformation(validDependencies));
 		List<String> invalidDependencies = dependencies.stream()
 			.filter((id) -> (!validDependencies.contains(id)))
-			.collect(Collectors.toList());
+			.toList();
 		if (!invalidDependencies.isEmpty()) {
 			document.triggerError().triggerInvalidDependencies(invalidDependencies);
 		}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/gradle/GradleProjectGenerationConfiguration.java

@@ -17,7 +17,6 @@
 package io.spring.initializr.generator.spring.build.gradle;
 
 import java.util.List;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.buildsystem.BuildItemResolver;
 import io.spring.initializr.generator.buildsystem.gradle.GradleBuild;
@@ -71,8 +70,7 @@ public GradleProjectGenerationConfiguration(IndentingWriterFactory indentingWrit
 	@Bean
 	public GradleBuild gradleBuild(ObjectProvider<BuildItemResolver> buildItemResolver,
 			ObjectProvider<BuildCustomizer<?>> buildCustomizers) {
-		return createGradleBuild(buildItemResolver.getIfAvailable(),
-				buildCustomizers.orderedStream().collect(Collectors.toList()));
+		return createGradleBuild(buildItemResolver.getIfAvailable(), buildCustomizers.orderedStream().toList());
 	}
 
 	@SuppressWarnings("unchecked")

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/build/maven/MavenProjectGenerationConfiguration.java

@@ -17,7 +17,6 @@
 package io.spring.initializr.generator.spring.build.maven;
 
 import java.util.List;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.buildsystem.BuildItemResolver;
 import io.spring.initializr.generator.buildsystem.maven.MavenBuild;
@@ -59,8 +58,7 @@ MavenWrapperContributor mavenWrapperContributor() {
 	@Bean
 	public MavenBuild mavenBuild(ObjectProvider<BuildItemResolver> buildItemResolver,
 			ObjectProvider<BuildCustomizer<?>> buildCustomizers) {
-		return createBuild(buildItemResolver.getIfAvailable(),
-				buildCustomizers.orderedStream().collect(Collectors.toList()));
+		return createBuild(buildItemResolver.getIfAvailable(), buildCustomizers.orderedStream().toList());
 	}
 
 	@SuppressWarnings("unchecked")

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/MainSourceCodeProjectContributor.java

@@ -20,7 +20,6 @@
 import java.nio.file.Path;
 import java.util.List;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.language.CompilationUnit;
 import io.spring.initializr.generator.language.SourceCode;
@@ -84,24 +83,22 @@ public void contribute(Path projectRoot) throws IOException {
 
 	@SuppressWarnings("unchecked")
 	private void customizeMainApplicationType(T mainApplicationType) {
-		List<MainApplicationTypeCustomizer<?>> customizers = this.mainTypeCustomizers.orderedStream()
-			.collect(Collectors.toList());
+		List<MainApplicationTypeCustomizer<?>> customizers = this.mainTypeCustomizers.orderedStream().toList();
 		LambdaSafe.callbacks(MainApplicationTypeCustomizer.class, customizers, mainApplicationType)
 			.invoke((customizer) -> customizer.customize(mainApplicationType));
 	}
 
 	@SuppressWarnings("unchecked")
 	private void customizeMainCompilationUnit(C compilationUnit) {
 		List<MainCompilationUnitCustomizer<?, ?>> customizers = this.mainCompilationUnitCustomizers.orderedStream()
-			.collect(Collectors.toList());
+			.toList();
 		LambdaSafe.callbacks(MainCompilationUnitCustomizer.class, customizers, compilationUnit)
 			.invoke((customizer) -> customizer.customize(compilationUnit));
 	}
 
 	@SuppressWarnings("unchecked")
 	private void customizeMainSourceCode(S sourceCode) {
-		List<MainSourceCodeCustomizer<?, ?, ?>> customizers = this.mainSourceCodeCustomizers.orderedStream()
-			.collect(Collectors.toList());
+		List<MainSourceCodeCustomizer<?, ?, ?>> customizers = this.mainSourceCodeCustomizers.orderedStream().toList();
 		LambdaSafe.callbacks(MainSourceCodeCustomizer.class, customizers, sourceCode)
 			.invoke((customizer) -> customizer.customize(sourceCode));
 	}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/ServletInitializerContributor.java

@@ -17,7 +17,6 @@
 package io.spring.initializr.generator.spring.code;
 
 import java.util.List;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.language.CompilationUnit;
 import io.spring.initializr.generator.language.SourceCode;
@@ -59,8 +58,7 @@ public void customize(SourceCode<TypeDeclaration, CompilationUnit<TypeDeclaratio
 
 	@SuppressWarnings("unchecked")
 	private void customizeServletInitializer(TypeDeclaration servletInitializer) {
-		List<ServletInitializerCustomizer<?>> customizers = this.servletInitializerCustomizers.orderedStream()
-			.collect(Collectors.toList());
+		List<ServletInitializerCustomizer<?>> customizers = this.servletInitializerCustomizers.orderedStream().toList();
 		LambdaSafe.callbacks(ServletInitializerCustomizer.class, customizers, servletInitializer)
 			.invoke((customizer) -> customizer.customize(servletInitializer));
 	}

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/TestSourceCodeProjectContributor.java

@@ -20,7 +20,6 @@
 import java.nio.file.Path;
 import java.util.List;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.language.CompilationUnit;
 import io.spring.initializr.generator.language.SourceCode;
@@ -80,15 +79,14 @@ public void contribute(Path projectRoot) throws IOException {
 	@SuppressWarnings("unchecked")
 	private void customizeTestApplicationType(TypeDeclaration testApplicationType) {
 		List<TestApplicationTypeCustomizer<?>> customizers = this.testApplicationTypeCustomizers.orderedStream()
-			.collect(Collectors.toList());
+			.toList();
 		LambdaSafe.callbacks(TestApplicationTypeCustomizer.class, customizers, testApplicationType)
 			.invoke((customizer) -> customizer.customize(testApplicationType));
 	}
 
 	@SuppressWarnings("unchecked")
 	private void customizeTestSourceCode(S sourceCode) {
-		List<TestSourceCodeCustomizer<?, ?, ?>> customizers = this.testSourceCodeCustomizers.orderedStream()
-			.collect(Collectors.toList());
+		List<TestSourceCodeCustomizer<?, ?, ?>> customizers = this.testSourceCodeCustomizers.orderedStream().toList();
 		LambdaSafe.callbacks(TestSourceCodeCustomizer.class, customizers, sourceCode)
 			.invoke((customizer) -> customizer.customize(sourceCode));
 	}

initializr-generator-test/src/main/java/io/spring/initializr/generator/test/project/ProjectAssetTester.java

@@ -21,7 +21,6 @@
 import java.util.Map;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.project.MutableProjectDescription;
 import io.spring.initializr.generator.project.ProjectAssetGenerator;
@@ -122,7 +121,7 @@ private ProjectAssetGenerator<ProjectStructure> runAllAvailableContributors() {
 				.createProjectDirectory(context.getBean(ProjectDescription.class));
 			List<ProjectContributor> projectContributors = context.getBeanProvider(ProjectContributor.class)
 				.orderedStream()
-				.collect(Collectors.toList());
+				.toList();
 			for (ProjectContributor projectContributor : projectContributors) {
 				projectContributor.contribute(projectDirectory);
 			}

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GradleBuildWriter.java

@@ -101,7 +101,7 @@ protected List<StandardGradlePlugin> extractStandardPlugin(GradleBuild build) {
 			.values()
 			.filter(StandardGradlePlugin.class::isInstance)
 			.map(StandardGradlePlugin.class::cast)
-			.collect(Collectors.toList());
+			.toList();
 	}
 
 	/**
@@ -138,8 +138,7 @@ private static String sourceCompatibilityAsNumber(GradleBuildSettings settings)
 	}
 
 	protected final void writeRepositories(IndentingWriter writer, GradleBuild build) {
-		writeNestedCollection(writer, "repositories", build.repositories().items().collect(Collectors.toList()),
-				this::repositoryAsString);
+		writeNestedCollection(writer, "repositories", build.repositories().items().toList(), this::repositoryAsString);
 	}
 
 	protected abstract String repositoryAsString(MavenRepository repository);
@@ -224,7 +223,7 @@ private void writeBoms(IndentingWriter writer, GradleBuild build) {
 		List<BillOfMaterials> boms = build.boms()
 			.items()
 			.sorted(Comparator.comparingInt(BillOfMaterials::getOrder).reversed())
-			.collect(Collectors.toList());
+			.toList();
 		writer.println();
 		writer.println("dependencyManagement {");
 		writer.indented(() -> writeNestedCollection(writer, "imports", boms, this::bomAsString));
@@ -326,7 +325,7 @@ private Collection<Dependency> filterDependencies(DependencyContainer dependenci
 		return dependencies.items()
 			.filter((dep) -> filter.test(dep.getScope()))
 			.sorted(getDependencyComparator())
-			.collect(Collectors.toList());
+			.toList();
 	}
 
 	@SafeVarargs

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/GroovyDslGradleBuildWriter.java

@@ -19,7 +19,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.function.BiFunction;
-import java.util.stream.Collectors;
 
 import io.spring.initializr.generator.buildsystem.BillOfMaterials;
 import io.spring.initializr.generator.buildsystem.Dependency;
@@ -76,7 +75,7 @@ protected void writePlugins(IndentingWriter writer, GradleBuild build) {
 	}
 
 	private List<GradlePlugin> extractApplyPlugins(GradleBuild build) {
-		return build.plugins().values().filter(GradlePlugin::isApply).collect(Collectors.toList());
+		return build.plugins().values().filter(GradlePlugin::isApply).toList();
 	}
 
 	private String pluginAsString(StandardGradlePlugin plugin) {

initializr-generator/src/main/java/io/spring/initializr/generator/buildsystem/gradle/KotlinDslGradleBuildWriter.java

@@ -101,7 +101,7 @@ protected void writeConfigurations(IndentingWriter writer, GradleConfigurationCo
 			return;
 		}
 		writer.println("configurations {");
-		List<String> customConfigurations = configurations.names().collect(Collectors.toList());
+		List<String> customConfigurations = configurations.names().toList();
 		writer.indented(() -> configurations.customizations()
 			.forEach((configuration) -> writeConfiguration(writer, configuration, customConfigurations)));
 		writer.println("}");