Fix Checkstyle violations

spring-session-core/src/main/java/org/springframework/session/MapReactorSessionRepository.java

@@ -16,16 +16,15 @@
 
 package org.springframework.session;
 
-import org.springframework.session.events.SessionDeletedEvent;
-import org.springframework.session.events.SessionExpiredEvent;
-import reactor.core.publisher.Mono;
-
 import java.time.Duration;
-import java.util.Collection;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
+import reactor.core.publisher.Mono;
+
+import org.springframework.session.events.SessionDeletedEvent;
+import org.springframework.session.events.SessionExpiredEvent;
+
 /**
  * A {@link SessionRepository} backed by a {@link Map} and that uses a
  * {@link MapSession}. By default a {@link ConcurrentHashMap} is
@@ -80,7 +79,7 @@ public class MapReactorSessionRepository implements ReactorSessionRepository<Ses
 			throw new IllegalArgumentException("sessions cannot be null");
 		}
 		this.sessions = new ConcurrentHashMap<>();
-		for(Session session : sessions) {
+		for (Session session : sessions) {
 			this.performSave(session);
 		}
 	}
@@ -96,7 +95,7 @@ public class MapReactorSessionRepository implements ReactorSessionRepository<Ses
 			throw new IllegalArgumentException("sessions cannot be null");
 		}
 		this.sessions = new ConcurrentHashMap<>();
-		for(Session session : sessions) {
+		for (Session session : sessions) {
 			this.performSave(session);
 		}
 	}

spring-session-core/src/main/java/org/springframework/session/MapSession.java

@@ -94,7 +94,7 @@ public final class MapSession implements Session, Serializable {
 				session.getAttributeNames().size());
 		for (String attrName : session.getAttributeNames()) {
 			Object attrValue = session.getAttribute(attrName);
-			if(attrValue != null) {
+			if (attrValue != null) {
 				this.sessionAttrs.put(attrName, attrValue);
 			}
 		}

spring-session-core/src/main/java/org/springframework/session/ReactorSessionRepository.java

@@ -53,6 +53,7 @@ public interface ReactorSessionRepository<S extends Session> {
 	 * </p>
 	 *
 	 * @param session the {@link Session} to save
+	 * @return indicator of operation completion
 	 */
 	Mono<Void> save(S session);
 
@@ -70,6 +71,7 @@ public interface ReactorSessionRepository<S extends Session> {
 	 * Deletes the {@link Session} with the given {@link Session#getId()} or does nothing
 	 * if the {@link Session} is not found.
 	 * @param id the {@link Session#getId()} to delete
+	 * @return indicator of operation completion
 	 */
 	Mono<Void> delete(String id);
 }

spring-session-core/src/main/java/org/springframework/session/Session.java

@@ -16,12 +16,12 @@
 
 package org.springframework.session;
 
-import org.springframework.util.Assert;
-
 import java.time.Duration;
 import java.time.Instant;
 import java.util.Set;
 
+import org.springframework.util.Assert;
+
 /**
  * Provides a way to identify a user in an agnostic way. This allows the session to be
  * used by an HttpSession, WebSocket Session, or even non web related sessions.

spring-session-core/src/main/java/org/springframework/session/web/http/HttpSessionAdapter.java

@@ -16,17 +16,18 @@
 
 package org.springframework.session.web.http;
 
-import org.springframework.session.Session;
-
-import javax.servlet.ServletContext;
-import javax.servlet.http.HttpSession;
-import javax.servlet.http.HttpSessionContext;
 import java.time.Duration;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.NoSuchElementException;
 import java.util.Set;
 
+import javax.servlet.ServletContext;
+import javax.servlet.http.HttpSession;
+import javax.servlet.http.HttpSessionContext;
+
+import org.springframework.session.Session;
+
 /**
  * Adapts Spring Session's {@link Session} to an {@link HttpSession}.
  *

spring-session-core/src/test/java/org/springframework/session/MapReactorSessionRepositoryTests.java

@@ -16,9 +16,6 @@
 
 package org.springframework.session;
 
-import org.junit.Before;
-import org.junit.Test;
-
 import java.time.Duration;
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
@@ -26,6 +23,9 @@ import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 
+import org.junit.Before;
+import org.junit.Test;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -86,7 +86,7 @@ public class MapReactorSessionRepositoryTests {
 
 	@Test(expected = IllegalArgumentException.class)
 	public void constructorMapWhenNullThenThrowsIllegalArgumentException() {
-		Map<String,Session> sessions = null;
+		Map<String, Session> sessions = null;
 		new MapReactorSessionRepository(sessions);
 	}
 
@@ -145,4 +145,4 @@ public class MapReactorSessionRepositoryTests {
 		assertThat(session.getMaxInactiveInterval())
 				.isEqualTo(expectedMaxInterval);
 	}
-}
+}

spring-session-core/src/test/java/org/springframework/session/MapSessionTests.java

@@ -16,13 +16,13 @@
 
 package org.springframework.session;
 
-import org.junit.Before;
-import org.junit.Test;
-
 import java.time.Duration;
 import java.time.Instant;
 import java.util.Set;
 
+import org.junit.Before;
+import org.junit.Test;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class MapSessionTests {

spring-session-core/src/test/java/org/springframework/session/security/SpringSessionBackedSessionRegistryTest.java

@@ -16,12 +16,19 @@
 
 package org.springframework.session.security;
 
+import java.time.Instant;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.ArgumentCaptor;
 import org.mockito.InjectMocks;
 import org.mockito.Mock;
 import org.mockito.junit.MockitoJUnitRunner;
+
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.context.SecurityContextImpl;
 import org.springframework.security.core.session.SessionInformation;
@@ -30,14 +37,10 @@ import org.springframework.session.FindByIndexNameSessionRepository;
 import org.springframework.session.MapSession;
 import org.springframework.session.Session;
 
-import java.time.Instant;
-import java.util.Collections;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
-
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.mockito.BDDMockito.*;
+import static org.mockito.BDDMockito.mock;
+import static org.mockito.BDDMockito.verify;
+import static org.mockito.BDDMockito.when;
 
 /**
  * Tests for {@link SpringSessionBackedSessionRegistry}.