diff --git a/core/spring-boot/src/main/java/org/springframework/boot/ApplicationInfoPropertySource.java b/core/spring-boot/src/main/java/org/springframework/boot/ApplicationInfoPropertySource.java
index a4feb10f9bc..46482deabb7 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/ApplicationInfoPropertySource.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/ApplicationInfoPropertySource.java
@@ -44,7 +44,7 @@ class ApplicationInfoPropertySource extends MapPropertySource implements OriginL
 		super(NAME, getProperties(readVersion(mainClass)));
 	}
 
-	ApplicationInfoPropertySource(String applicationVersion) {
+	ApplicationInfoPropertySource(@Nullable String applicationVersion) {
 		super(NAME, getProperties(applicationVersion));
 	}
 
diff --git a/core/spring-boot/src/main/java/org/springframework/boot/DefaultPropertiesPropertySource.java b/core/spring-boot/src/main/java/org/springframework/boot/DefaultPropertiesPropertySource.java
index ee19df5bfa5..5b4dfb4b450 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/DefaultPropertiesPropertySource.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/DefaultPropertiesPropertySource.java
@@ -69,7 +69,7 @@ public class DefaultPropertiesPropertySource extends MapPropertySource {
 	 * @param action the action used to consume the
 	 * {@link DefaultPropertiesPropertySource}
 	 */
-	public static void ifNotEmpty(Map<String, Object> source,
+	public static void ifNotEmpty(@Nullable Map<String, Object> source,
 			@Nullable Consumer<DefaultPropertiesPropertySource> action) {
 		if (!CollectionUtils.isEmpty(source) && action != null) {
 			action.accept(new DefaultPropertiesPropertySource(source));
diff --git a/core/spring-boot/src/main/java/org/springframework/boot/ResourceBanner.java b/core/spring-boot/src/main/java/org/springframework/boot/ResourceBanner.java
index 5807f168a7d..8fc468fb31d 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/ResourceBanner.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/ResourceBanner.java
@@ -155,7 +155,7 @@ public class ResourceBanner implements Banner {
 		return environment.getProperty("spring.application.version");
 	}
 
-	protected String getBootVersion() {
+	protected @Nullable String getBootVersion() {
 		return SpringBootVersion.getVersion();
 	}
 
diff --git a/core/spring-boot/src/main/java/org/springframework/boot/context/annotation/Configurations.java b/core/spring-boot/src/main/java/org/springframework/boot/context/annotation/Configurations.java
index b1a642f25a4..26ac171e52b 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/context/annotation/Configurations.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/context/annotation/Configurations.java
@@ -88,7 +88,7 @@ public abstract class Configurations {
 	 * @since 3.4.0
 	 */
 	protected Configurations(@Nullable UnaryOperator<Collection<Class<?>>> sorter, Collection<Class<?>> classes,
-			Function<Class<?>, String> beanNameGenerator) {
+			@Nullable Function<Class<?>, String> beanNameGenerator) {
 		Assert.notNull(classes, "'classes' must not be null");
 		this.sorter = (sorter != null) ? sorter : UnaryOperator.identity();
 		Collection<Class<?>> sorted = this.sorter.apply(classes);
diff --git a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataActivationContext.java b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataActivationContext.java
index 22c15a748e5..cefc7a1f58f 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataActivationContext.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataActivationContext.java
@@ -52,7 +52,7 @@ class ConfigDataActivationContext {
 	 * @param cloudPlatform the cloud platform
 	 * @param profiles the profiles
 	 */
-	ConfigDataActivationContext(@Nullable CloudPlatform cloudPlatform, Profiles profiles) {
+	ConfigDataActivationContext(@Nullable CloudPlatform cloudPlatform, @Nullable Profiles profiles) {
 		this.cloudPlatform = cloudPlatform;
 		this.profiles = profiles;
 	}
diff --git a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentContributor.java b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentContributor.java
index a5e9ef3b991..4bea1170b5a 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentContributor.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentContributor.java
@@ -440,9 +440,10 @@ class ConfigDataEnvironmentContributor implements Iterable<ConfigDataEnvironment
 	 * @param environmentUpdateListener the environment update listener
 	 * @return a new {@link ConfigDataEnvironmentContributor} instance
 	 */
-	static ConfigDataEnvironmentContributor ofUnboundImport(ConfigDataLocation location, ConfigDataResource resource,
-			boolean profileSpecific, ConfigData configData, int propertySourceIndex,
-			ConversionService conversionService, ConfigDataEnvironmentUpdateListener environmentUpdateListener) {
+	static ConfigDataEnvironmentContributor ofUnboundImport(@Nullable ConfigDataLocation location,
+			@Nullable ConfigDataResource resource, boolean profileSpecific, ConfigData configData,
+			int propertySourceIndex, ConversionService conversionService,
+			ConfigDataEnvironmentUpdateListener environmentUpdateListener) {
 		PropertySource<?> propertySource = configData.getPropertySources().get(propertySourceIndex);
 		ConfigData.Options options = configData.getOptions(propertySource);
 		options = environmentUpdateListener.onConfigDataOptions(configData, propertySource, options);
diff --git a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessor.java b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessor.java
index d3b37d23bc5..3120313173c 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessor.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessor.java
@@ -160,7 +160,7 @@ public class ConfigDataEnvironmentPostProcessor implements EnvironmentPostProces
 	 * {@link ConfigDataEnvironmentUpdateListener} that can be used to track
 	 * {@link Environment} updates.
 	 */
-	public static void applyTo(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
+	public static void applyTo(ConfigurableEnvironment environment, @Nullable ResourceLoader resourceLoader,
 			@Nullable ConfigurableBootstrapContext bootstrapContext, Collection<String> additionalProfiles,
 			ConfigDataEnvironmentUpdateListener environmentUpdateListener) {
 		DeferredLogFactory logFactory = Supplier::get;
diff --git a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataProperties.java b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataProperties.java
index fe3a5ae77d1..3727de94854 100644
--- a/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataProperties.java
+++ b/core/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigDataProperties.java
@@ -27,6 +27,7 @@ import org.springframework.boot.context.properties.bind.Bindable;
 import org.springframework.boot.context.properties.bind.Binder;
 import org.springframework.boot.context.properties.bind.Name;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
+import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -99,14 +100,14 @@ class ConfigDataProperties {
 
 		private final @Nullable CloudPlatform onCloudPlatform;
 
-		private final String[] onProfile;
+		private final String @Nullable [] onProfile;
 
 		/**
 		 * Create a new {@link Activate} instance.
 		 * @param onCloudPlatform the cloud platform required for activation
 		 * @param onProfile the profile expression required for activation
 		 */
-		Activate(@Nullable CloudPlatform onCloudPlatform, String[] onProfile) {
+		Activate(@Nullable CloudPlatform onCloudPlatform, String @Nullable [] onProfile) {
 			this.onProfile = onProfile;
 			this.onCloudPlatform = onCloudPlatform;
 		}
@@ -137,6 +138,7 @@ class ConfigDataProperties {
 		}
 
 		private boolean matchesActiveProfiles(Predicate<String> activeProfiles) {
+			Assert.state(this.onProfile != null, "'this.onProfile' must not be null");
 			return org.springframework.core.env.Profiles.of(this.onProfile).matches(activeProfiles);
 		}