style: fix checkstyle

src/main/java/mate/academy/bookstore/controller/BookController.java

@@ -20,7 +20,6 @@
 import org.springframework.web.bind.annotation.ResponseStatus;
 import org.springframework.web.bind.annotation.RestController;
 
-
 @RestController
 @RequestMapping("/api/books")
 @AllArgsConstructor
@@ -40,7 +39,8 @@ public ResponseEntity<SuccessResponse<BookDto>> getBookById(@PathVariable Long i
     }
 
     @PostMapping
-    public ResponseEntity<SuccessResponse<BookDto>> createBook(@Valid @RequestBody BookRequestDto bookDto) {
+    public ResponseEntity<SuccessResponse<BookDto>> createBook(
+            @Valid @RequestBody BookRequestDto bookDto) {
         return ResponseHandler.getSuccessResponse(
                 bookService.save(bookDto),
                 HttpStatus.CREATED);

src/main/java/mate/academy/bookstore/response/ErrorResponse.java

@@ -6,7 +6,7 @@
 
 @Getter
 public class ErrorResponse extends GeneralResponse {
-    private List<Message> errors;
+    private final List<Message> errors;
 
     public record Message(String field, String message) {
     }

src/main/java/mate/academy/bookstore/response/GeneralResponse.java

@@ -7,11 +7,11 @@
 
 @Getter
 public abstract class GeneralResponse {
-    private boolean success;
-    private int status;
+    private final boolean success;
+    private final int status;
 
     @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd-MM-yyyy hh:mm:ss")
-    private Date timestamp;
+    private final Date timestamp;
 
     public GeneralResponse(HttpStatus status) {
         this.timestamp = new Date();

src/main/java/mate/academy/bookstore/response/SuccessResponse.java

@@ -5,7 +5,7 @@
 
 @Getter
 public class SuccessResponse<T> extends GeneralResponse {
-    private T data;
+    private final T data;
 
     public SuccessResponse(T data, HttpStatus status) {
         super(status);