Applied checkstyle rules

tests/samples-messaging-integration/src/main/java/com/example/BookListener.java

@@ -49,6 +49,6 @@ public class BookListener {
 	 */
 	public void bookDeleted(BookDeleted bookDeleted) {
 		log.info("Deleting book [ "+ bookDeleted + "]");
-		bookSuccessfullyDeleted.set(true);
+		this.bookSuccessfullyDeleted.set(true);
 	}
 }

tests/samples-messaging-integration/src/main/java/com/example/BookService.java

@@ -41,7 +41,7 @@ public class BookService {
 	 */
 	public void returnBook(BookReturned bookReturned) {
 		log.info("Returning book " + bookReturned);
-		outputChannel.send(MessageBuilder.withPayload(bookReturned)
+		this.outputChannel.send(MessageBuilder.withPayload(bookReturned)
 				.setHeader("BOOK-NAME", bookReturned.bookName).build());
 	}
 }