checkstyle FinalClassCheck

fixes

fixModifiers after fixFinal

Revert CachingSessionFactory

Class is spied in tests.

checkstyle - Import Rules

checkstyle InterfaceIsType

checkstyle InnerTypeLast

checkstyle OneStatementPerLine

CovariantEquals
OneTopLevelClass

* Revert `'\n'` -> `System.lineSeparator()` in the Gradle scripts to meet Git `autocrlf = true` on Windows
* Fix timing issue with the `LastModifiedFileListFilterTests`, when the `age = 1` might not be enough for the file object when we have some delay before checking

spring-integration-file/src/main/java/org/springframework/integration/file/HeadDirectoryScanner.java

@@ -57,7 +57,7 @@ public class HeadDirectoryScanner extends DefaultDirectoryScanner {
 	}
 
 
-	private static class HeadFilter implements FileListFilter<File> {
+	private static final class HeadFilter implements FileListFilter<File> {
 
 		private final int maxNumberOfFiles;
 

spring-integration-file/src/main/java/org/springframework/integration/file/remote/RemoteFileTemplate.java

@@ -548,7 +548,7 @@ public class RemoteFileTemplate<F> implements RemoteFileOperations<F>, Initializ
 		return directoryPath;
 	}
 
-	private class StreamHolder {
+	private final class StreamHolder {
 
 		private final InputStream stream;
 

spring-integration-file/src/main/java/org/springframework/integration/file/remote/RemoteFileUtils.java

@@ -30,7 +30,7 @@ import org.springframework.integration.file.remote.session.Session;
  * @since 3.0
  *
  */
-public class RemoteFileUtils {
+public final class RemoteFileUtils {
 
 	private RemoteFileUtils() {}
 

spring-integration-file/src/main/java/org/springframework/integration/file/remote/session/CachingSessionFactory.java

@@ -157,7 +157,7 @@ public class CachingSessionFactory<F> implements SessionFactory<F>, DisposableBe
 		this.pool.removeAllIdleItems();
 	}
 
-	public class CachedSession implements Session<F> {
+	public class CachedSession implements Session<F> { //NOSONAR (final)
 
 		private final Session<F> targetSession;