diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/ContextIdApplicationContextInitializer.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/ContextIdApplicationContextInitializer.java
index f8aae8e15e..f7e6e0ceee 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/ContextIdApplicationContextInitializer.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/ContextIdApplicationContextInitializer.java
@@ -72,7 +72,7 @@ public class ContextIdApplicationContextInitializer
 	/**
 	 * The ID of a context.
 	 */
-	class ContextId {
+	static class ContextId {
 
 		private final AtomicLong children = new AtomicLong(0);
 
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigFileApplicationListener.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigFileApplicationListener.java
index f796359dc2..485c5fa75f 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigFileApplicationListener.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/ConfigFileApplicationListener.java
@@ -248,7 +248,7 @@ public class ConfigFileApplicationListener implements EnvironmentPostProcessor,
 	 * {@link BeanFactoryPostProcessor} to re-order our property sources below any
 	 * {@code @PropertySource} items added by the {@link ConfigurationClassPostProcessor}.
 	 */
-	private class PropertySourceOrderingPostProcessor implements BeanFactoryPostProcessor, Ordered {
+	private static class PropertySourceOrderingPostProcessor implements BeanFactoryPostProcessor, Ordered {
 
 		private ConfigurableApplicationContext context;
 
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/info/InfoProperties.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/info/InfoProperties.java
index 17cb796911..18e5bc951b 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/info/InfoProperties.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/info/InfoProperties.java
@@ -121,7 +121,7 @@ public class InfoProperties implements Iterable<InfoProperties.Entry> {
 	/**
 	 * Property entry.
 	 */
-	public final class Entry {
+	public static final class Entry {
 
 		private final String key;
 
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/java/JavaLoggingSystem.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/java/JavaLoggingSystem.java
index 0b04ee7751..e79b751006 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/java/JavaLoggingSystem.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/java/JavaLoggingSystem.java
@@ -168,7 +168,7 @@ public class JavaLoggingSystem extends AbstractLoggingSystem {
 		this.configuredLoggers.clear();
 	}
 
-	private final class ShutdownHandler implements Runnable {
+	private static final class ShutdownHandler implements Runnable {
 
 		@Override
 		public void run() {
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java
index cf7de8cd5a..0ddaa7c66f 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/util/LambdaSafe.java
@@ -279,12 +279,10 @@ public final class LambdaSafe {
 		 * @param invoker the invoker used to invoke the callback
 		 */
 		public void invoke(Consumer<C> invoker) {
-			this.callbackInstances.forEach((callbackInstance) -> {
-				invoke(callbackInstance, () -> {
-					invoker.accept(callbackInstance);
-					return null;
-				});
-			});
+			this.callbackInstances.forEach((callbackInstance) -> invoke(callbackInstance, () -> {
+				invoker.accept(callbackInstance);
+				return null;
+			}));
 		}
 
 		/**