Fix code style issues

Author: kobylynskyi

src/main/java/com/kobylynskyi/graphql/codegen/mapper/InputValueDefinitionToParameterMapper.java

@@ -3,8 +3,6 @@
 import com.kobylynskyi.graphql.codegen.model.MappingContext;
 import com.kobylynskyi.graphql.codegen.model.NamedDefinition;
 import com.kobylynskyi.graphql.codegen.model.ParameterDefinition;
-import graphql.language.Directive;
-import graphql.language.DirectivesContainer;
 import graphql.language.InputValueDefinition;
 
 import java.util.List;
@@ -30,12 +28,6 @@ public InputValueDefinitionToParameterMapper(ValueMapper valueMapper,
         this.dataModelMapper = dataModelMapper;
     }
 
-    private static boolean isDeprecated(DirectivesContainer<?> node) {
-        return node.getDirectives().stream()
-                .map(Directive::getName)
-                .anyMatch(Deprecated.class.getSimpleName()::equalsIgnoreCase);
-    }
-
     /**
      * Map input value definition to a Freemarker-understandable data model type
      *

src/main/java/com/kobylynskyi/graphql/codegen/model/DeprecatedDefinition.java

@@ -6,7 +6,7 @@
  */
 public class DeprecatedDefinition {
 
-    private final static String DEFAULT_MSG = "No longer supported";
+    private static final String DEFAULT_MSG = "No longer supported";
 
     // For different languages, real implementation.
     private final String annotation;

src/main/java/com/kobylynskyi/graphql/codegen/model/MultiLanguageDeprecated.java

@@ -9,10 +9,13 @@
  */
 public class MultiLanguageDeprecated {
 
-    private final static String REASON = "reason";
-    private final static String SCALA_ANNOTATION = "deprecated";
-    private final static String JAVA_ANNOTATION = "Deprecated";
-    private final static String KOTLIN_ANNOTATION = "Deprecated";
+    private static final String REASON = "reason";
+    private static final String SCALA_ANNOTATION = "deprecated";
+    private static final String JAVA_ANNOTATION = "Deprecated";
+    private static final String KOTLIN_ANNOTATION = "Deprecated";
+
+    private MultiLanguageDeprecated() {
+    }
 
     public static DeprecatedDefinition getLanguageDeprecated(GeneratedLanguage generatedLanguage, Directive directive) {
         String msg = null;