Polish

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/jmx/DefaultEndpointObjectNameFactoryTests.java

@@ -101,7 +101,6 @@ public class DefaultEndpointObjectNameFactoryTests {
 	public void generateObjectNameWithUniqueNamesDeprecatedPropertyMismatchMainProperty() {
 		this.environment.setProperty("spring.jmx.unique-names", "false");
 		this.properties.setUniqueNames(true);
-
 		this.thrown.expect(IllegalArgumentException.class);
 		this.thrown.expectMessage("spring.jmx.unique-names");
 		this.thrown.expectMessage("management.endpoints.jmx.unique-names");

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/http/codec/CodecsAutoConfiguration.java

@@ -72,10 +72,8 @@ public class CodecsAutoConfiguration {
 
 		@Bean
 		public CodecCustomizer loggingCodecCustomizer(InsightsProperties properties) {
-			return (configurer) -> {
-				configurer.defaultCodecs().enableLoggingRequestDetails(
-						properties.getWeb().isLogRequestDetails());
-			};
+			return (configurer) -> configurer.defaultCodecs().enableLoggingRequestDetails(
+					properties.getWeb().isLogRequestDetails());
 		}
 
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/KafkaStreamsAnnotationDrivenConfiguration.java

@@ -56,15 +56,12 @@ class KafkaStreamsAnnotationDrivenConfiguration {
 		Map<String, Object> streamsProperties = this.properties.buildStreamsProperties();
 		if (this.properties.getStreams().getApplicationId() == null) {
 			String applicationName = environment.getProperty("spring.application.name");
-			if (applicationName != null) {
-				streamsProperties.put(StreamsConfig.APPLICATION_ID_CONFIG,
-						applicationName);
-			}
-			else {
+			if (applicationName == null) {
 				throw new InvalidConfigurationPropertyValueException(
 						"spring.kafka.streams.application-id", null,
 						"This property is mandatory and fallback 'spring.application.name' is not set either.");
 			}
+			streamsProperties.put(StreamsConfig.APPLICATION_ID_CONFIG, applicationName);
 		}
 		return new KafkaStreamsConfiguration(streamsProperties);
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskExecutionAutoConfiguration.java

@@ -17,7 +17,6 @@
 package org.springframework.boot.autoconfigure.task;
 
 import java.util.concurrent.Executor;
-import java.util.stream.Collectors;
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -66,14 +65,16 @@ public class TaskExecutionAutoConfiguration {
 	@ConditionalOnMissingBean
 	public TaskExecutorBuilder taskExecutorBuilder() {
 		TaskExecutionProperties.Pool pool = this.properties.getPool();
-		return new TaskExecutorBuilder().queueCapacity(pool.getQueueCapacity())
-				.corePoolSize(pool.getCoreSize()).maxPoolSize(pool.getMaxSize())
-				.allowCoreThreadTimeOut(pool.isAllowCoreThreadTimeout())
-				.keepAlive(pool.getKeepAlive())
-				.threadNamePrefix(this.properties.getThreadNamePrefix())
-				.customizers(this.taskExecutorCustomizers.stream()
-						.collect(Collectors.toList()))
-				.taskDecorator(this.taskDecorator.getIfUnique());
+		TaskExecutorBuilder builder = new TaskExecutorBuilder();
+		builder = builder.queueCapacity(pool.getQueueCapacity());
+		builder = builder.corePoolSize(pool.getCoreSize());
+		builder = builder.maxPoolSize(pool.getMaxSize());
+		builder = builder.allowCoreThreadTimeOut(pool.isAllowCoreThreadTimeout());
+		builder = builder.keepAlive(pool.getKeepAlive());
+		builder = builder.threadNamePrefix(this.properties.getThreadNamePrefix());
+		builder = builder.customizers(this.taskExecutorCustomizers);
+		builder = builder.taskDecorator(this.taskDecorator.getIfUnique());
+		return builder;
 	}
 
 	@Bean(name = APPLICATION_TASK_EXECUTOR_BEAN_NAME)

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskSchedulingAutoConfiguration.java

@@ -16,8 +16,6 @@
 
 package org.springframework.boot.autoconfigure.task;
 
-import java.util.stream.Collectors;
-
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
@@ -55,9 +53,11 @@ public class TaskSchedulingAutoConfiguration {
 	@ConditionalOnMissingBean
 	public TaskSchedulerBuilder taskSchedulerBuilder(TaskSchedulingProperties properties,
 			ObjectProvider<TaskSchedulerCustomizer> taskSchedulerCustomizers) {
-		return new TaskSchedulerBuilder().poolSize(properties.getPool().getSize())
-				.threadNamePrefix(properties.getThreadNamePrefix()).customizers(
-						taskSchedulerCustomizers.stream().collect(Collectors.toList()));
+		TaskSchedulerBuilder builder = new TaskSchedulerBuilder();
+		builder = builder.poolSize(properties.getPool().getSize());
+		builder = builder.threadNamePrefix(properties.getThreadNamePrefix());
+		builder = builder.customizers(taskSchedulerCustomizers);
+		return builder;
 	}
 
 }

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -5879,9 +5879,9 @@ The following code shows a typical example:
 ----
 
 
+
 [[boot-features-webclient-runtime]]
 === WebClient Runtime
-
 Spring Boot will auto-detect which `ClientHttpConnector` to drive `WebClient`, depending
 on the libraries available on the application classpath.
 
@@ -5901,6 +5901,7 @@ You can learn more about the
 options in the Spring Framework reference documentation].
 
 
+
 [[boot-features-webclient-customization]]
 === WebClient Customization
 There are three main approaches to `WebClient` customization, depending on how broadly you

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/task/TaskExecutorBuilder.java

@@ -18,7 +18,6 @@ package org.springframework.boot.task;
 
 import java.time.Duration;
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.Set;
@@ -59,11 +58,9 @@ public class TaskExecutorBuilder {
 
 	private final TaskDecorator taskDecorator;
 
-	private final Set<TaskExecutorCustomizer> taskExecutorCustomizers;
+	private final Set<TaskExecutorCustomizer> customizers;
 
-	public TaskExecutorBuilder(TaskExecutorCustomizer... taskExecutorCustomizers) {
-		Assert.notNull(taskExecutorCustomizers,
-				"TaskExecutorCustomizers must not be null");
+	public TaskExecutorBuilder() {
 		this.queueCapacity = null;
 		this.corePoolSize = null;
 		this.maxPoolSize = null;
@@ -71,14 +68,13 @@ public class TaskExecutorBuilder {
 		this.keepAlive = null;
 		this.threadNamePrefix = null;
 		this.taskDecorator = null;
-		this.taskExecutorCustomizers = Collections.unmodifiableSet(
-				new LinkedHashSet<>(Arrays.asList(taskExecutorCustomizers)));
+		this.customizers = null;
 	}
 
-	public TaskExecutorBuilder(Integer queueCapacity, Integer corePoolSize,
+	private TaskExecutorBuilder(Integer queueCapacity, Integer corePoolSize,
 			Integer maxPoolSize, Boolean allowCoreThreadTimeOut, Duration keepAlive,
 			String threadNamePrefix, TaskDecorator taskDecorator,
-			Set<TaskExecutorCustomizer> taskExecutorCustomizers) {
+			Set<TaskExecutorCustomizer> customizers) {
 		this.queueCapacity = queueCapacity;
 		this.corePoolSize = corePoolSize;
 		this.maxPoolSize = maxPoolSize;
@@ -86,7 +82,7 @@ public class TaskExecutorBuilder {
 		this.keepAlive = keepAlive;
 		this.threadNamePrefix = threadNamePrefix;
 		this.taskDecorator = taskDecorator;
-		this.taskExecutorCustomizers = taskExecutorCustomizers;
+		this.customizers = customizers;
 	}
 
 	/**
@@ -98,7 +94,7 @@ public class TaskExecutorBuilder {
 	public TaskExecutorBuilder queueCapacity(int queueCapacity) {
 		return new TaskExecutorBuilder(queueCapacity, this.corePoolSize, this.maxPoolSize,
 				this.allowCoreThreadTimeOut, this.keepAlive, this.threadNamePrefix,
-				this.taskDecorator, this.taskExecutorCustomizers);
+				this.taskDecorator, this.customizers);
 	}
 
 	/**
@@ -113,7 +109,7 @@ public class TaskExecutorBuilder {
 	public TaskExecutorBuilder corePoolSize(int corePoolSize) {
 		return new TaskExecutorBuilder(this.queueCapacity, corePoolSize, this.maxPoolSize,
 				this.allowCoreThreadTimeOut, this.keepAlive, this.threadNamePrefix,
-				this.taskDecorator, this.taskExecutorCustomizers);
+				this.taskDecorator, this.customizers);
 	}
 
 	/**
@@ -128,7 +124,7 @@ public class TaskExecutorBuilder {
 	public TaskExecutorBuilder maxPoolSize(int maxPoolSize) {
 		return new TaskExecutorBuilder(this.queueCapacity, this.corePoolSize, maxPoolSize,
 				this.allowCoreThreadTimeOut, this.keepAlive, this.threadNamePrefix,
-				this.taskDecorator, this.taskExecutorCustomizers);
+				this.taskDecorator, this.customizers);
 	}
 
 	/**
@@ -140,7 +136,7 @@ public class TaskExecutorBuilder {
 	public TaskExecutorBuilder allowCoreThreadTimeOut(boolean allowCoreThreadTimeOut) {
 		return new TaskExecutorBuilder(this.queueCapacity, this.corePoolSize,
 				this.maxPoolSize, allowCoreThreadTimeOut, this.keepAlive,
-				this.threadNamePrefix, this.taskDecorator, this.taskExecutorCustomizers);
+				this.threadNamePrefix, this.taskDecorator, this.customizers);
 	}
 
 	/**
@@ -151,7 +147,7 @@ public class TaskExecutorBuilder {
 	public TaskExecutorBuilder keepAlive(Duration keepAlive) {
 		return new TaskExecutorBuilder(this.queueCapacity, this.corePoolSize,
 				this.maxPoolSize, this.allowCoreThreadTimeOut, keepAlive,
-				this.threadNamePrefix, this.taskDecorator, this.taskExecutorCustomizers);
+				this.threadNamePrefix, this.taskDecorator, this.customizers);
 	}
 
 	/**
@@ -162,7 +158,7 @@ public class TaskExecutorBuilder {
 	public TaskExecutorBuilder threadNamePrefix(String threadNamePrefix) {
 		return new TaskExecutorBuilder(this.queueCapacity, this.corePoolSize,
 				this.maxPoolSize, this.allowCoreThreadTimeOut, this.keepAlive,
-				threadNamePrefix, this.taskDecorator, this.taskExecutorCustomizers);
+				threadNamePrefix, this.taskDecorator, this.customizers);
 	}
 
 	/**
@@ -173,7 +169,7 @@ public class TaskExecutorBuilder {
 	public TaskExecutorBuilder taskDecorator(TaskDecorator taskDecorator) {
 		return new TaskExecutorBuilder(this.queueCapacity, this.corePoolSize,
 				this.maxPoolSize, this.allowCoreThreadTimeOut, this.keepAlive,
-				this.threadNamePrefix, taskDecorator, this.taskExecutorCustomizers);
+				this.threadNamePrefix, taskDecorator, this.customizers);
 	}
 
 	/**
@@ -181,15 +177,13 @@ public class TaskExecutorBuilder {
 	 * applied to the {@link ThreadPoolTaskExecutor}. Customizers are applied in the order
 	 * that they were added after builder configuration has been applied. Setting this
 	 * value will replace any previously configured customizers.
-	 * @param taskExecutorCustomizers the customizers to set
+	 * @param customizers the customizers to set
 	 * @return a new builder instance
 	 * @see #additionalCustomizers(TaskExecutorCustomizer...)
 	 */
-	public TaskExecutorBuilder customizers(
-			TaskExecutorCustomizer... taskExecutorCustomizers) {
-		Assert.notNull(taskExecutorCustomizers,
-				"TaskExecutorCustomizers must not be null");
-		return customizers(Arrays.asList(taskExecutorCustomizers));
+	public TaskExecutorBuilder customizers(TaskExecutorCustomizer... customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
+		return customizers(Arrays.asList(customizers));
 	}
 
 	/**
@@ -197,52 +191,46 @@ public class TaskExecutorBuilder {
 	 * applied to the {@link ThreadPoolTaskExecutor}. Customizers are applied in the order
 	 * that they were added after builder configuration has been applied. Setting this
 	 * value will replace any previously configured customizers.
-	 * @param taskExecutorCustomizers the customizers to set
+	 * @param customizers the customizers to set
 	 * @return a new builder instance
 	 * @see #additionalCustomizers(TaskExecutorCustomizer...)
 	 */
-	public TaskExecutorBuilder customizers(
-			Collection<? extends TaskExecutorCustomizer> taskExecutorCustomizers) {
-		Assert.notNull(taskExecutorCustomizers,
-				"TaskExecutorCustomizers must not be null");
+	public TaskExecutorBuilder customizers(Iterable<TaskExecutorCustomizer> customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
 		return new TaskExecutorBuilder(this.queueCapacity, this.corePoolSize,
 				this.maxPoolSize, this.allowCoreThreadTimeOut, this.keepAlive,
-				this.threadNamePrefix, this.taskDecorator,
-				Collections.unmodifiableSet(new LinkedHashSet<TaskExecutorCustomizer>(
-						taskExecutorCustomizers)));
+				this.threadNamePrefix, this.taskDecorator, append(null, customizers));
 	}
 
 	/**
 	 * Add {@link TaskExecutorCustomizer TaskExecutorCustomizers} that should be applied
 	 * to the {@link ThreadPoolTaskExecutor}. Customizers are applied in the order that
 	 * they were added after builder configuration has been applied.
-	 * @param taskExecutorCustomizers the customizers to add
+	 * @param customizers the customizers to add
 	 * @return a new builder instance
 	 * @see #customizers(TaskExecutorCustomizer...)
 	 */
 	public TaskExecutorBuilder additionalCustomizers(
-			TaskExecutorCustomizer... taskExecutorCustomizers) {
-		Assert.notNull(taskExecutorCustomizers,
-				"TaskExecutorCustomizers must not be null");
-		return additionalCustomizers(Arrays.asList(taskExecutorCustomizers));
+			TaskExecutorCustomizer... customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
+		return additionalCustomizers(Arrays.asList(customizers));
 	}
 
 	/**
 	 * Add {@link TaskExecutorCustomizer TaskExecutorCustomizers} that should be applied
 	 * to the {@link ThreadPoolTaskExecutor}. Customizers are applied in the order that
 	 * they were added after builder configuration has been applied.
-	 * @param taskExecutorCustomizers the customizers to add
+	 * @param customizers the customizers to add
 	 * @return a new builder instance
 	 * @see #customizers(TaskExecutorCustomizer...)
 	 */
 	public TaskExecutorBuilder additionalCustomizers(
-			Collection<? extends TaskExecutorCustomizer> taskExecutorCustomizers) {
-		Assert.notNull(taskExecutorCustomizers,
-				"TaskExecutorCustomizers must not be null");
+			Iterable<TaskExecutorCustomizer> customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
 		return new TaskExecutorBuilder(this.queueCapacity, this.corePoolSize,
 				this.maxPoolSize, this.allowCoreThreadTimeOut, this.keepAlive,
 				this.threadNamePrefix, this.taskDecorator,
-				append(this.taskExecutorCustomizers, taskExecutorCustomizers));
+				append(this.customizers, customizers));
 	}
 
 	/**
@@ -288,18 +276,15 @@ public class TaskExecutorBuilder {
 		map.from(this.threadNamePrefix).whenHasText()
 				.to(taskExecutor::setThreadNamePrefix);
 		map.from(this.taskDecorator).to(taskExecutor::setTaskDecorator);
-
-		if (!CollectionUtils.isEmpty(this.taskExecutorCustomizers)) {
-			for (TaskExecutorCustomizer customizer : this.taskExecutorCustomizers) {
-				customizer.customize(taskExecutor);
-			}
+		if (!CollectionUtils.isEmpty(this.customizers)) {
+			this.customizers.forEach((customizer) -> customizer.customize(taskExecutor));
 		}
 		return taskExecutor;
 	}
 
-	private static <T> Set<T> append(Set<T> set, Collection<? extends T> additions) {
+	private <T> Set<T> append(Set<T> set, Iterable<? extends T> additions) {
 		Set<T> result = new LinkedHashSet<>((set != null) ? set : Collections.emptySet());
-		result.addAll(additions);
+		additions.forEach(result::add);
 		return Collections.unmodifiableSet(result);
 	}
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/task/TaskSchedulerBuilder.java

@@ -17,7 +17,6 @@
 package org.springframework.boot.task;
 
 import java.util.Arrays;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.Set;
@@ -45,22 +44,19 @@ public class TaskSchedulerBuilder {
 
 	private final String threadNamePrefix;
 
-	private final Set<TaskSchedulerCustomizer> taskSchedulerCustomizers;
+	private final Set<TaskSchedulerCustomizer> customizers;
 
-	public TaskSchedulerBuilder(TaskSchedulerCustomizer... taskSchedulerCustomizers) {
-		Assert.notNull(taskSchedulerCustomizers,
-				"TaskSchedulerCustomizers must not be null");
+	public TaskSchedulerBuilder() {
 		this.poolSize = null;
 		this.threadNamePrefix = null;
-		this.taskSchedulerCustomizers = Collections.unmodifiableSet(
-				new LinkedHashSet<>(Arrays.asList(taskSchedulerCustomizers)));
+		this.customizers = null;
 	}
 
 	public TaskSchedulerBuilder(Integer poolSize, String threadNamePrefix,
 			Set<TaskSchedulerCustomizer> taskSchedulerCustomizers) {
 		this.poolSize = poolSize;
 		this.threadNamePrefix = threadNamePrefix;
-		this.taskSchedulerCustomizers = taskSchedulerCustomizers;
+		this.customizers = taskSchedulerCustomizers;
 	}
 
 	/**
@@ -70,7 +66,7 @@ public class TaskSchedulerBuilder {
 	 */
 	public TaskSchedulerBuilder poolSize(int poolSize) {
 		return new TaskSchedulerBuilder(poolSize, this.threadNamePrefix,
-				this.taskSchedulerCustomizers);
+				this.customizers);
 	}
 
 	/**
@@ -80,7 +76,7 @@ public class TaskSchedulerBuilder {
 	 */
 	public TaskSchedulerBuilder threadNamePrefix(String threadNamePrefix) {
 		return new TaskSchedulerBuilder(this.poolSize, threadNamePrefix,
-				this.taskSchedulerCustomizers);
+				this.customizers);
 	}
 
 	/**
@@ -88,15 +84,13 @@ public class TaskSchedulerBuilder {
 	 * applied to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the
 	 * order that they were added after builder configuration has been applied. Setting
 	 * this value will replace any previously configured customizers.
-	 * @param taskSchedulerCustomizers the customizers to set
+	 * @param customizers the customizers to set
 	 * @return a new builder instance
 	 * @see #additionalCustomizers(TaskSchedulerCustomizer...)
 	 */
-	public TaskSchedulerBuilder customizers(
-			TaskSchedulerCustomizer... taskSchedulerCustomizers) {
-		Assert.notNull(taskSchedulerCustomizers,
-				"TaskSchedulerCustomizers must not be null");
-		return customizers(Arrays.asList(taskSchedulerCustomizers));
+	public TaskSchedulerBuilder customizers(TaskSchedulerCustomizer... customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
+		return customizers(Arrays.asList(customizers));
 	}
 
 	/**
@@ -104,48 +98,44 @@ public class TaskSchedulerBuilder {
 	 * applied to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the
 	 * order that they were added after builder configuration has been applied. Setting
 	 * this value will replace any previously configured customizers.
-	 * @param taskSchedulerCustomizers the customizers to set
+	 * @param customizers the customizers to set
 	 * @return a new builder instance
 	 * @see #additionalCustomizers(TaskSchedulerCustomizer...)
 	 */
 	public TaskSchedulerBuilder customizers(
-			Collection<? extends TaskSchedulerCustomizer> taskSchedulerCustomizers) {
-		Assert.notNull(taskSchedulerCustomizers,
-				"TaskSchedulerCustomizers must not be null");
+			Iterable<TaskSchedulerCustomizer> customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
 		return new TaskSchedulerBuilder(this.poolSize, this.threadNamePrefix,
-				Collections.unmodifiableSet(new LinkedHashSet<TaskSchedulerCustomizer>(
-						taskSchedulerCustomizers)));
+				append(null, customizers));
 	}
 
 	/**
 	 * Add {@link TaskSchedulerCustomizer taskSchedulerCustomizers} that should be applied
 	 * to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the order that
 	 * they were added after builder configuration has been applied.
-	 * @param taskSchedulerCustomizers the customizers to add
+	 * @param customizers the customizers to add
 	 * @return a new builder instance
 	 * @see #customizers(TaskSchedulerCustomizer...)
 	 */
 	public TaskSchedulerBuilder additionalCustomizers(
-			TaskSchedulerCustomizer... taskSchedulerCustomizers) {
-		Assert.notNull(taskSchedulerCustomizers,
-				"TaskSchedulerCustomizers must not be null");
-		return additionalCustomizers(Arrays.asList(taskSchedulerCustomizers));
+			TaskSchedulerCustomizer... customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
+		return additionalCustomizers(Arrays.asList(customizers));
 	}
 
 	/**
 	 * Add {@link TaskSchedulerCustomizer taskSchedulerCustomizers} that should be applied
 	 * to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the order that
 	 * they were added after builder configuration has been applied.
-	 * @param taskSchedulerCustomizers the customizers to add
+	 * @param customizers the customizers to add
 	 * @return a new builder instance
 	 * @see #customizers(TaskSchedulerCustomizer...)
 	 */
 	public TaskSchedulerBuilder additionalCustomizers(
-			Collection<? extends TaskSchedulerCustomizer> taskSchedulerCustomizers) {
-		Assert.notNull(taskSchedulerCustomizers,
-				"TaskSchedulerCustomizers must not be null");
+			Iterable<TaskSchedulerCustomizer> customizers) {
+		Assert.notNull(customizers, "Customizers must not be null");
 		return new TaskSchedulerBuilder(this.poolSize, this.threadNamePrefix,
-				append(this.taskSchedulerCustomizers, taskSchedulerCustomizers));
+				append(this.customizers, customizers));
 	}
 
 	/**
@@ -169,18 +159,15 @@ public class TaskSchedulerBuilder {
 		PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
 		map.from(this.poolSize).to(taskScheduler::setPoolSize);
 		map.from(this.threadNamePrefix).to(taskScheduler::setThreadNamePrefix);
-
-		if (!CollectionUtils.isEmpty(this.taskSchedulerCustomizers)) {
-			for (TaskSchedulerCustomizer customizer : this.taskSchedulerCustomizers) {
-				customizer.customize(taskScheduler);
-			}
+		if (!CollectionUtils.isEmpty(this.customizers)) {
+			this.customizers.forEach((customizer) -> customizer.customize(taskScheduler));
 		}
 		return taskScheduler;
 	}
 
-	private static <T> Set<T> append(Set<T> set, Collection<? extends T> additions) {
+	private <T> Set<T> append(Set<T> set, Iterable<? extends T> additions) {
 		Set<T> result = new LinkedHashSet<>((set != null) ? set : Collections.emptySet());
-		result.addAll(additions);
+		additions.forEach(result::add);
 		return Collections.unmodifiableSet(result);
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/task/TaskExecutorBuilderTests.java

@@ -47,13 +47,6 @@ public class TaskExecutorBuilderTests {
 
 	private TaskExecutorBuilder builder = new TaskExecutorBuilder();
 
-	@Test
-	public void createWhenCustomizersAreNullShouldThrowException() {
-		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskExecutorCustomizers must not be null");
-		new TaskExecutorBuilder((TaskExecutorCustomizer[]) null);
-	}
-
 	@Test
 	public void poolSettingsShouldApply() {
 		ThreadPoolTaskExecutor executor = this.builder.queueCapacity(10).corePoolSize(4)
@@ -85,14 +78,14 @@ public class TaskExecutorBuilderTests {
 	@Test
 	public void customizersWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskExecutorCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.customizers((TaskExecutorCustomizer[]) null);
 	}
 
 	@Test
 	public void customizersCollectionWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskExecutorCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.customizers((Set<TaskExecutorCustomizer>) null);
 	}
 
@@ -135,14 +128,14 @@ public class TaskExecutorBuilderTests {
 	@Test
 	public void additionalCustomizersWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskExecutorCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.additionalCustomizers((TaskExecutorCustomizer[]) null);
 	}
 
 	@Test
 	public void additionalCustomizersCollectionWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskExecutorCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.additionalCustomizers((Set<TaskExecutorCustomizer>) null);
 	}
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/task/TaskSchedulerBuilderTests.java

@@ -43,13 +43,6 @@ public class TaskSchedulerBuilderTests {
 
 	private TaskSchedulerBuilder builder = new TaskSchedulerBuilder();
 
-	@Test
-	public void createWhenCustomizersAreNullShouldThrowException() {
-		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
-		new TaskSchedulerBuilder((TaskSchedulerCustomizer[]) null);
-	}
-
 	@Test
 	public void poolSettingsShouldApply() {
 		ThreadPoolTaskScheduler scheduler = this.builder.poolSize(4).build();
@@ -66,14 +59,14 @@ public class TaskSchedulerBuilderTests {
 	@Test
 	public void customizersWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.customizers((TaskSchedulerCustomizer[]) null);
 	}
 
 	@Test
 	public void customizersCollectionWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.customizers((Set<TaskSchedulerCustomizer>) null);
 	}
 
@@ -108,14 +101,14 @@ public class TaskSchedulerBuilderTests {
 	@Test
 	public void additionalCustomizersWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.additionalCustomizers((TaskSchedulerCustomizer[]) null);
 	}
 
 	@Test
 	public void additionalCustomizersCollectionWhenCustomizersAreNullShouldThrowException() {
 		this.thrown.expect(IllegalArgumentException.class);
-		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.thrown.expectMessage("Customizers must not be null");
 		this.builder.additionalCustomizers((Set<TaskSchedulerCustomizer>) null);
 	}