diff --git a/src/main/java/org/codelibs/fess/FessBoot.java b/src/main/java/org/codelibs/fess/FessBoot.java
index edfe41686..7489d86a9 100644
--- a/src/main/java/org/codelibs/fess/FessBoot.java
+++ b/src/main/java/org/codelibs/fess/FessBoot.java
@@ -86,7 +86,7 @@ public class FessBoot extends TomcatBoot {
                 .asDevelopment(isNoneEnv()).bootAwait();
     }
 
-    public static void shutdown(String[] args) {
+    public static void shutdown(final String[] args) {
         System.exit(0);
     }
 
diff --git a/src/main/java/org/codelibs/fess/api/json/JsonApiManager.java b/src/main/java/org/codelibs/fess/api/json/JsonApiManager.java
index 1122c60a4..46463e432 100644
--- a/src/main/java/org/codelibs/fess/api/json/JsonApiManager.java
+++ b/src/main/java/org/codelibs/fess/api/json/JsonApiManager.java
@@ -316,10 +316,10 @@ public class JsonApiManager extends BaseApiManager {
             return;
         }
 
-        String seed = request.getParameter("seed");
-        String[] tags = request.getParameterValues("labels");
-        String[] fields = request.getParameterValues("fields");
-        String[] excludes = StringUtil.EMPTY_STRINGS;// TODO
+        final String seed = request.getParameter("seed");
+        final String[] tags = request.getParameterValues("labels");
+        final String[] fields = request.getParameterValues("fields");
+        final String[] excludes = StringUtil.EMPTY_STRINGS;// TODO
 
         final PopularWordHelper popularWordHelper = ComponentUtil.getPopularWordHelper();
 
@@ -675,13 +675,13 @@ public class JsonApiManager extends BaseApiManager {
 
         private final HttpServletRequest request;
 
-        private FessConfig fessConfig;
+        private final FessConfig fessConfig;
 
         private int startPosition = -1;
 
         private int pageSize = -1;
 
-        protected SearchApiRequestParams(final HttpServletRequest request, FessConfig fessConfig) {
+        protected SearchApiRequestParams(final HttpServletRequest request, final FessConfig fessConfig) {
             this.request = request;
             this.fessConfig = fessConfig;
         }
diff --git a/src/main/java/org/codelibs/fess/app/service/SearchService.java b/src/main/java/org/codelibs/fess/app/service/SearchService.java
index ee64825ab..1ceac0e27 100644
--- a/src/main/java/org/codelibs/fess/app/service/SearchService.java
+++ b/src/main/java/org/codelibs/fess/app/service/SearchService.java
@@ -112,8 +112,8 @@ public class SearchService {
                         fessConfig.getIndexDocumentType(),
                         searchRequestBuilder -> {
                             if (StringUtil.isNotBlank(sortField)) {
-                                String[] sort = sortField.split("\\.");
-                                SortBuilder sortBuilder = SortBuilders.fieldSort(sort[0]);
+                                final String[] sort = sortField.split("\\.");
+                                final SortBuilder sortBuilder = SortBuilders.fieldSort(sort[0]);
                                 if ("asc".equals(sort[1])) {
                                     sortBuilder.order(SortOrder.ASC);
                                 } else if ("desc".equals(sort[1])) {
diff --git a/src/main/java/org/codelibs/fess/app/web/admin/design/AdminDesignAction.java b/src/main/java/org/codelibs/fess/app/web/admin/design/AdminDesignAction.java
index eb7d553c8..9499132b6 100644
--- a/src/main/java/org/codelibs/fess/app/web/admin/design/AdminDesignAction.java
+++ b/src/main/java/org/codelibs/fess/app/web/admin/design/AdminDesignAction.java
@@ -306,7 +306,7 @@ public class AdminDesignAction extends FessAdminAction implements Serializable {
         return asHtml(path_AdminDesign_AdminDesignJsp).useForm(DesignForm.class);
     }
 
-    private HtmlResponse asListHtml(UploadForm uploadForm) {
+    private HtmlResponse asListHtml(final UploadForm uploadForm) {
         return asHtml(path_AdminDesign_AdminDesignJsp).useForm(DesignForm.class, setup -> {
             setup.setup(form -> {
                 copyBeanToBean(uploadForm, form, op -> op.include("designFile", "designFileName"));
diff --git a/src/main/java/org/codelibs/fess/app/web/admin/general/AdminGeneralAction.java b/src/main/java/org/codelibs/fess/app/web/admin/general/AdminGeneralAction.java
index c7bb4551f..f222db943 100644
--- a/src/main/java/org/codelibs/fess/app/web/admin/general/AdminGeneralAction.java
+++ b/src/main/java/org/codelibs/fess/app/web/admin/general/AdminGeneralAction.java
@@ -108,7 +108,7 @@ public class AdminGeneralAction extends FessAdminAction {
             saveInfo(messages -> messages.addSuccessSendTestmail(GLOBAL));
             updateProperty(Constants.NOTIFICATION_TO_PROPERTY, form.notificationTo);
             crawlerProperties.store();
-        } catch (Exception e) {
+        } catch (final Exception e) {
             logger.warn("Failed to send a test mail.", e);
             saveError(messages -> messages.addErrorsFailedToSendTestmail(GLOBAL));
         }
@@ -157,7 +157,7 @@ public class AdminGeneralAction extends FessAdminAction {
         return redirect(getClass());
     }
 
-    private String getCheckboxValue(String value) {
+    private String getCheckboxValue(final String value) {
         return Constants.ON.equalsIgnoreCase(value) ? Constants.TRUE : Constants.FALSE;
     }
 
diff --git a/src/main/java/org/codelibs/fess/app/web/base/login/FessLoginAssist.java b/src/main/java/org/codelibs/fess/app/web/base/login/FessLoginAssist.java
index 09375eac8..94834e643 100644
--- a/src/main/java/org/codelibs/fess/app/web/base/login/FessLoginAssist.java
+++ b/src/main/java/org/codelibs/fess/app/web/base/login/FessLoginAssist.java
@@ -67,8 +67,8 @@ public class FessLoginAssist extends TypicalLoginAssist<String, FessUserBean, Fe
     }
 
     @Override
-    public OptionalEntity<FessUser> findLoginUser(String username, String password) {
-        OptionalEntity<FessUser> ldapUser = ComponentUtil.getLdapManager().login(username, password);
+    public OptionalEntity<FessUser> findLoginUser(final String username, final String password) {
+        final OptionalEntity<FessUser> ldapUser = ComponentUtil.getLdapManager().login(username, password);
         if (ldapUser.isPresent()) {
             return ldapUser;
         }
diff --git a/src/main/java/org/codelibs/fess/app/web/login/LoginAction.java b/src/main/java/org/codelibs/fess/app/web/login/LoginAction.java
index b5f429809..85f087d8f 100644
--- a/src/main/java/org/codelibs/fess/app/web/login/LoginAction.java
+++ b/src/main/java/org/codelibs/fess/app/web/login/LoginAction.java
@@ -68,7 +68,7 @@ public class LoginAction extends FessSearchAction {
         return getUserBean().map(user -> redirectByUser(user)).orElse(asHtml(path_Login_IndexJsp));
     }
 
-    private HtmlResponse redirectByUser(FessUserBean user) {
+    private HtmlResponse redirectByUser(final FessUserBean user) {
         if (!user.hasRoles(fessConfig.getAuthenticationAdminRolesAsArray())) {
             return redirectToRoot();
         }
diff --git a/src/main/java/org/codelibs/fess/app/web/search/SearchAction.java b/src/main/java/org/codelibs/fess/app/web/search/SearchAction.java
index 408013603..a5037373b 100644
--- a/src/main/java/org/codelibs/fess/app/web/search/SearchAction.java
+++ b/src/main/java/org/codelibs/fess/app/web/search/SearchAction.java
@@ -252,7 +252,7 @@ public class SearchAction extends FessSearchAction {
 
     protected static class WebRenderData extends SearchRenderData {
 
-        public void register(RenderData data) {
+        public void register(final RenderData data) {
             RenderDataUtil.register(data, "queryId", queryId);
             RenderDataUtil.register(data, "documentItems", documentItems);
             RenderDataUtil.register(data, "facetResponse", facetResponse);
diff --git a/src/main/java/org/codelibs/fess/es/client/FessEsClient.java b/src/main/java/org/codelibs/fess/es/client/FessEsClient.java
index 64db3b9e1..366ed76cd 100644
--- a/src/main/java/org/codelibs/fess/es/client/FessEsClient.java
+++ b/src/main/java/org/codelibs/fess/es/client/FessEsClient.java
@@ -224,7 +224,7 @@ public class FessEsClient implements Client {
 
     @PostConstruct
     public void open() {
-        FessConfig fessConfig = ComponentUtil.getFessConfig();
+        final FessConfig fessConfig = ComponentUtil.getFessConfig();
 
         final String transportAddressesValue = System.getProperty(Constants.FESS_ES_TRANSPORT_ADDRESSES);
         if (StringUtil.isNotBlank(transportAddressesValue)) {
diff --git a/src/main/java/org/codelibs/fess/es/user/exentity/User.java b/src/main/java/org/codelibs/fess/es/user/exentity/User.java
index 7075e52f4..f590e4ac4 100644
--- a/src/main/java/org/codelibs/fess/es/user/exentity/User.java
+++ b/src/main/java/org/codelibs/fess/es/user/exentity/User.java
@@ -45,11 +45,13 @@ public class User extends BsUser implements FessUser {
         asDocMeta().id(id);
     }
 
+    @Override
     public String[] getRoleNames() {
         return StreamUtil.of(getRoles()).map(role -> new String(Base64.getDecoder().decode(role), Constants.CHARSET_UTF_8))
                 .toArray(n -> new String[n]);
     }
 
+    @Override
     public String[] getGroupNames() {
         return StreamUtil.of(getGroups()).map(group -> new String(Base64.getDecoder().decode(group), Constants.CHARSET_UTF_8))
                 .toArray(n -> new String[n]);
diff --git a/src/main/java/org/codelibs/fess/helper/PopularWordHelper.java b/src/main/java/org/codelibs/fess/helper/PopularWordHelper.java
index 085a6f25c..f6a626bb9 100644
--- a/src/main/java/org/codelibs/fess/helper/PopularWordHelper.java
+++ b/src/main/java/org/codelibs/fess/helper/PopularWordHelper.java
@@ -18,7 +18,6 @@ package org.codelibs.fess.helper;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 
@@ -51,44 +50,46 @@ public class PopularWordHelper {
                         .expireAfterWrite(fessConfig.getSuggestPopularWordCacheExpireAsInteger().longValue(), TimeUnit.MINUTES).build();
     }
 
-    public List<String> getWordList(String seed, String[] tags, String[] fields, String[] excludes) {
-        RoleQueryHelper roleQueryHelper = ComponentUtil.getRoleQueryHelper();
-        String[] roles = roleQueryHelper.build().stream().toArray(n -> new String[n]);
+    public List<String> getWordList(final String seed, final String[] tags, final String[] fields, final String[] excludes) {
+        final RoleQueryHelper roleQueryHelper = ComponentUtil.getRoleQueryHelper();
+        final String[] roles = roleQueryHelper.build().stream().toArray(n -> new String[n]);
         return getWordList(seed, tags, roles, fields, excludes);
     }
 
-    public List<String> getWordList(String seed, String[] tags, String[] roles, String[] fields, String[] excludes) {
+    public List<String> getWordList(final String seed, final String[] tags, final String[] roles, final String[] fields,
+            final String[] excludes) {
         try {
-            return cache.get(getCacheKey(seed, tags, roles, fields, excludes), new Callable<List<String>>() {
-                @Override
-                public List<String> call() throws Exception {
-                    final List<String> wordList = new ArrayList<String>();
-                    SuggestHelper suggestHelper = ComponentUtil.getSuggestHelper();
-                    final PopularWordsRequestBuilder popularWordsRequestBuilder =
-                            suggestHelper.suggester().popularWords().setSize(fessConfig.getSuggestPopularWordSizeAsInteger().intValue())
-                                    .setWindowSize(fessConfig.getSuggestPopularWordWindowSizeAsInteger().intValue());
-                    if (seed != null) {
-                        popularWordsRequestBuilder.setSeed(seed);
-                    }
-                    StreamUtil.of(tags).forEach(tag -> popularWordsRequestBuilder.addTag(tag));
-                    StreamUtil.of(roles).forEach(role -> popularWordsRequestBuilder.addRole(role));
-                    StreamUtil.of(fields).forEach(field -> popularWordsRequestBuilder.addField(field));
-                    StreamUtil.of(excludes).forEach(exclude -> popularWordsRequestBuilder.addExcludeWord(exclude));
-                    popularWordsRequestBuilder.execute().then(r -> {
-                        r.getItems().stream().forEach(item -> wordList.add(item.getText()));
-                    }).error(t -> logger.warn("Failed to generate popular words.", t));
+            return cache.get(
+                    getCacheKey(seed, tags, roles, fields, excludes),
+                    () -> {
+                        final List<String> wordList = new ArrayList<String>();
+                        final SuggestHelper suggestHelper = ComponentUtil.getSuggestHelper();
+                        final PopularWordsRequestBuilder popularWordsRequestBuilder =
+                                suggestHelper.suggester().popularWords()
+                                        .setSize(fessConfig.getSuggestPopularWordSizeAsInteger().intValue())
+                                        .setWindowSize(fessConfig.getSuggestPopularWordWindowSizeAsInteger().intValue());
+                        if (seed != null) {
+                            popularWordsRequestBuilder.setSeed(seed);
+                        }
+                        StreamUtil.of(tags).forEach(tag -> popularWordsRequestBuilder.addTag(tag));
+                        StreamUtil.of(roles).forEach(role -> popularWordsRequestBuilder.addRole(role));
+                        StreamUtil.of(fields).forEach(field -> popularWordsRequestBuilder.addField(field));
+                        StreamUtil.of(excludes).forEach(exclude -> popularWordsRequestBuilder.addExcludeWord(exclude));
+                        popularWordsRequestBuilder.execute().then(r -> {
+                            r.getItems().stream().forEach(item -> wordList.add(item.getText()));
+                        }).error(t -> logger.warn("Failed to generate popular words.", t));
 
-                    return wordList;
-                }
-            });
-        } catch (ExecutionException e) {
+                        return wordList;
+                    });
+        } catch (final ExecutionException e) {
             logger.warn("Failed to load popular words.", e);
         }
         return Collections.emptyList();
     }
 
-    protected String getCacheKey(String seed, String[] tags, String[] roles, String[] fields, String[] excludes) {
-        StringBuilder buf = new StringBuilder(100);
+    protected String getCacheKey(final String seed, final String[] tags, final String[] roles, final String[] fields,
+            final String[] excludes) {
+        final StringBuilder buf = new StringBuilder(100);
         buf.append(seed).append(CACHE_KEY_SPLITTER);
         StreamUtil.of(tags).sorted().reduce((l, r) -> l + r).ifPresent(v -> buf.append(v));
         buf.append(CACHE_KEY_SPLITTER);
diff --git a/src/main/java/org/codelibs/fess/helper/SambaHelper.java b/src/main/java/org/codelibs/fess/helper/SambaHelper.java
index bc673506b..687576e01 100644
--- a/src/main/java/org/codelibs/fess/helper/SambaHelper.java
+++ b/src/main/java/org/codelibs/fess/helper/SambaHelper.java
@@ -41,15 +41,15 @@ public class SambaHelper {
         return convert(sid.getType(), sid.getAccountName());
     }
 
-    public String getRoleByUser(String name) {
+    public String getRoleByUser(final String name) {
         return convert(SID_TYPE_USER, name);
     }
 
-    public String getRoleByGroup(String name) {
+    public String getRoleByGroup(final String name) {
         return convert(SID_TYPE_DOM_GRP, name);
     }
 
-    protected String convert(int type, String name) {
+    protected String convert(final int type, final String name) {
         return type + name;
     }
 }
diff --git a/src/main/java/org/codelibs/fess/helper/SuggestHelper.java b/src/main/java/org/codelibs/fess/helper/SuggestHelper.java
index 8de2a9cad..bbace4743 100644
--- a/src/main/java/org/codelibs/fess/helper/SuggestHelper.java
+++ b/src/main/java/org/codelibs/fess/helper/SuggestHelper.java
@@ -81,7 +81,7 @@ public class SuggestHelper {
 
     private List<String> contentFieldList;
 
-    private List<Pattern> roleFilterList = new ArrayList<>();
+    private final List<Pattern> roleFilterList = new ArrayList<>();
 
     @PostConstruct
     public void init() {
@@ -274,7 +274,7 @@ public class SuggestHelper {
         suggester.indexer().deleteBadWord(badWord);
     }
 
-    private Stream<String> stream(String value) {
+    private Stream<String> stream(final String value) {
         return StreamUtil.of(value.split(",")).filter(v -> StringUtil.isNotBlank(v));
     }
 
diff --git a/src/main/java/org/codelibs/fess/helper/ViewHelper.java b/src/main/java/org/codelibs/fess/helper/ViewHelper.java
index 022312bc1..229e1c7ae 100644
--- a/src/main/java/org/codelibs/fess/helper/ViewHelper.java
+++ b/src/main/java/org/codelibs/fess/helper/ViewHelper.java
@@ -418,7 +418,7 @@ public class ViewHelper implements Serializable {
 
         String cache = DocumentUtil.getValue(doc, fessConfig.getIndexFieldCache(), String.class);
         if (cache != null) {
-            String mimetype = DocumentUtil.getValue(doc, fessConfig.getIndexFieldMimetype(), String.class);
+            final String mimetype = DocumentUtil.getValue(doc, fessConfig.getIndexFieldMimetype(), String.class);
             if (!ComponentUtil.getFessConfig().isHtmlMimetypeForCache(mimetype)) {
                 cache = StringEscapeUtils.escapeHtml4(cache);
             }
diff --git a/src/main/java/org/codelibs/fess/ldap/LdapManager.java b/src/main/java/org/codelibs/fess/ldap/LdapManager.java
index 918dadcba..82519871c 100644
--- a/src/main/java/org/codelibs/fess/ldap/LdapManager.java
+++ b/src/main/java/org/codelibs/fess/ldap/LdapManager.java
@@ -42,9 +42,9 @@ import org.slf4j.LoggerFactory;
 public class LdapManager {
     private static final Logger logger = LoggerFactory.getLogger(AdLoginInfoFilter.class);
 
-    public OptionalEntity<FessUser> login(String username, String password) {
-        FessConfig fessConfig = ComponentUtil.getFessConfig();
-        String providerUrl = fessConfig.getLdapProviderUrl();
+    public OptionalEntity<FessUser> login(final String username, final String password) {
+        final FessConfig fessConfig = ComponentUtil.getFessConfig();
+        final String providerUrl = fessConfig.getLdapProviderUrl();
 
         if (StringUtil.isBlank(providerUrl)) {
             return OptionalEntity.empty();
@@ -52,7 +52,7 @@ public class LdapManager {
 
         DirContext ctx = null;
         try {
-            Hashtable<String, String> env = new Hashtable<>();
+            final Hashtable<String, String> env = new Hashtable<>();
             env.put(Context.INITIAL_CONTEXT_FACTORY, fessConfig.getLdapInitialContextFactory());
             env.put(Context.SECURITY_AUTHENTICATION, fessConfig.getLdapSecurityAuthentication());
             env.put(Context.PROVIDER_URL, providerUrl);
@@ -63,13 +63,13 @@ public class LdapManager {
                 logger.debug("Logged in.", ctx);
             }
             return OptionalEntity.of(createLdapUser(username, env));
-        } catch (NamingException e) {
+        } catch (final NamingException e) {
             logger.debug("Login failed.", e);
         } finally {
             if (ctx != null) {
                 try {
                     ctx.close();
-                } catch (NamingException e) {
+                } catch (final NamingException e) {
                     // ignore
                 }
             }
@@ -77,13 +77,13 @@ public class LdapManager {
         return OptionalEntity.empty();
     }
 
-    protected LdapUser createLdapUser(String username, Hashtable<String, String> env) {
+    protected LdapUser createLdapUser(final String username, final Hashtable<String, String> env) {
         return new LdapUser(env, username);
     }
 
-    public String[] getRoles(final LdapUser ldapUser, String bindDn, String accountFilter) {
-        SambaHelper sambaHelper = ComponentUtil.getSambaHelper();
-        FessConfig fessConfig = ComponentUtil.getFessConfig();
+    public String[] getRoles(final LdapUser ldapUser, final String bindDn, final String accountFilter) {
+        final SambaHelper sambaHelper = ComponentUtil.getSambaHelper();
+        final FessConfig fessConfig = ComponentUtil.getFessConfig();
         final List<String> roleList = new ArrayList<String>();
 
         if (fessConfig.isSmbRoleAsUser()) {
@@ -113,7 +113,7 @@ public class LdapManager {
                 }
 
                 for (int i = 0; i < attr.size(); i++) {
-                    Object attrValue = attr.get(i);
+                    final Object attrValue = attr.get(i);
                     if (attrValue != null) {
                         // TODO replace with regexp
                         String strTmp = attrValue.toString();
diff --git a/src/main/java/org/codelibs/fess/ldap/LdapUser.java b/src/main/java/org/codelibs/fess/ldap/LdapUser.java
index c143c0e14..642373aff 100644
--- a/src/main/java/org/codelibs/fess/ldap/LdapUser.java
+++ b/src/main/java/org/codelibs/fess/ldap/LdapUser.java
@@ -31,7 +31,7 @@ public class LdapUser implements FessUser {
 
     protected String[] roles = null;
 
-    public LdapUser(Hashtable<String, String> env, String name) {
+    public LdapUser(final Hashtable<String, String> env, final String name) {
         this.env = env;
         this.name = name;
     }
diff --git a/src/main/java/org/codelibs/fess/mylasta/direction/FessProp.java b/src/main/java/org/codelibs/fess/mylasta/direction/FessProp.java
index 27d098d58..536790da7 100644
--- a/src/main/java/org/codelibs/fess/mylasta/direction/FessProp.java
+++ b/src/main/java/org/codelibs/fess/mylasta/direction/FessProp.java
@@ -21,15 +21,15 @@ import org.codelibs.fess.util.ComponentUtil;
 import org.codelibs.fess.util.StreamUtil;
 
 public interface FessProp {
-    public default String getProperty(String key) {
+    public default String getProperty(final String key) {
         return ComponentUtil.getCrawlerProperties().getProperty(key);
     }
 
-    public default String getProperty(String key, String defaultValue) {
+    public default String getProperty(final String key, final String defaultValue) {
         return ComponentUtil.getCrawlerProperties().getProperty(key, defaultValue);
     }
 
-    public default void setLoginRequired(boolean value) {
+    public default void setLoginRequired(final boolean value) {
         ComponentUtil.getCrawlerProperties().setProperty(Constants.LOGIN_REQUIRED_PROPERTY, value ? Constants.TRUE : Constants.FALSE);
     }
 
@@ -50,7 +50,7 @@ public interface FessProp {
         return getProperty(Constants.LDAP_PROVIDER_URL);
     }
 
-    public default String getLdapSecurityPrincipal(String username) {
+    public default String getLdapSecurityPrincipal(final String username) {
         return String.format(getProperty(Constants.LDAP_SECURITY_PRINCIPAL, StringUtil.EMPTY), username);
     }
 
@@ -88,8 +88,8 @@ public interface FessProp {
 
     String getCrawlerDocumentCacheHtmlMimetypes();
 
-    public default boolean isHtmlMimetypeForCache(String mimetype) {
-        String[] mimetypes = getCrawlerDocumentCacheHtmlMimetypes().split(",");
+    public default boolean isHtmlMimetypeForCache(final String mimetype) {
+        final String[] mimetypes = getCrawlerDocumentCacheHtmlMimetypes().split(",");
         if (mimetypes.length == 1 && StringUtil.isBlank(mimetypes[0])) {
             return true;
         }
@@ -98,8 +98,8 @@ public interface FessProp {
 
     String getCrawlerDocumentCacheSupportedMimetypes();
 
-    public default boolean isSupportedDocumentCacheMimetypes(String mimetype) {
-        String[] mimetypes = getCrawlerDocumentCacheSupportedMimetypes().split(",");
+    public default boolean isSupportedDocumentCacheMimetypes(final String mimetype) {
+        final String[] mimetypes = getCrawlerDocumentCacheSupportedMimetypes().split(",");
         if (mimetypes.length == 1 && StringUtil.isBlank(mimetypes[0])) {
             return true;
         }
diff --git a/src/main/java/org/codelibs/fess/util/QueryStringBuilder.java b/src/main/java/org/codelibs/fess/util/QueryStringBuilder.java
index ebb5ce55d..20b05f30d 100644
--- a/src/main/java/org/codelibs/fess/util/QueryStringBuilder.java
+++ b/src/main/java/org/codelibs/fess/util/QueryStringBuilder.java
@@ -60,18 +60,18 @@ public class QueryStringBuilder {
         return queryBuf.toString();
     }
 
-    public static QueryStringBuilder query(String query) {
-        QueryStringBuilder builder = new QueryStringBuilder();
+    public static QueryStringBuilder query(final String query) {
+        final QueryStringBuilder builder = new QueryStringBuilder();
         builder.query = query;
         return builder;
     }
 
-    public QueryStringBuilder extraQueries(String[] extraQueries) {
+    public QueryStringBuilder extraQueries(final String[] extraQueries) {
         this.extraQueries = extraQueries;
         return this;
     }
 
-    public QueryStringBuilder fields(Map<String, String[]> fieldMap) {
+    public QueryStringBuilder fields(final Map<String, String[]> fieldMap) {
         this.fieldMap = fieldMap;
         return this;
     }
diff --git a/src/main/java/org/codelibs/fess/util/RenderDataUtil.java b/src/main/java/org/codelibs/fess/util/RenderDataUtil.java
index 6fb549fc7..b35711219 100644
--- a/src/main/java/org/codelibs/fess/util/RenderDataUtil.java
+++ b/src/main/java/org/codelibs/fess/util/RenderDataUtil.java
@@ -25,7 +25,7 @@ import org.lastaflute.web.response.render.RenderData;
 
 public class RenderDataUtil {
 
-    public static void register(RenderData data, String key, Object value) {
+    public static void register(final RenderData data, final String key, final Object value) {
         if (value instanceof Entity) {
             data.register(key, BeanUtil.copyBeanToNewMap(value));
         } else if (value instanceof Collection<?>) {
diff --git a/src/main/java/org/codelibs/fess/util/ResourceUtil.java b/src/main/java/org/codelibs/fess/util/ResourceUtil.java
index 7b2b7bef8..96b12ebad 100644
--- a/src/main/java/org/codelibs/fess/util/ResourceUtil.java
+++ b/src/main/java/org/codelibs/fess/util/ResourceUtil.java
@@ -41,7 +41,7 @@ public class ResourceUtil {
         if (url != null) {
             return url;
         }
-        FessConfig fessConfig = ComponentUtil.getFessConfig();
+        final FessConfig fessConfig = ComponentUtil.getFessConfig();
         return fessConfig.getElasticsearchHttpUrl();
     }
 
diff --git a/src/main/java/org/codelibs/fess/validation/CronExpressionValidator.java b/src/main/java/org/codelibs/fess/validation/CronExpressionValidator.java
index 6f430530b..5b5f9fb83 100644
--- a/src/main/java/org/codelibs/fess/validation/CronExpressionValidator.java
+++ b/src/main/java/org/codelibs/fess/validation/CronExpressionValidator.java
@@ -23,15 +23,15 @@ import org.codelibs.core.lang.StringUtil;
 public class CronExpressionValidator implements ConstraintValidator<CronExpression, String> {
 
     @Override
-    public void initialize(CronExpression constraintAnnotation) {
+    public void initialize(final CronExpression constraintAnnotation) {
     }
 
     @Override
-    public boolean isValid(String value, ConstraintValidatorContext context) {
+    public boolean isValid(final String value, final ConstraintValidatorContext context) {
         return determineValid(value);
     }
 
-    protected boolean determineValid(String value) {
+    protected boolean determineValid(final String value) {
         if (StringUtil.isNotBlank(value) && !org.quartz.CronExpression.isValidExpression(value)) {
             return false;
         }
diff --git a/src/main/java/org/codelibs/fess/validation/UriTypeValidator.java b/src/main/java/org/codelibs/fess/validation/UriTypeValidator.java
index 6d7396183..47f309562 100644
--- a/src/main/java/org/codelibs/fess/validation/UriTypeValidator.java
+++ b/src/main/java/org/codelibs/fess/validation/UriTypeValidator.java
@@ -25,7 +25,7 @@ public class UriTypeValidator implements ConstraintValidator<UriType, String> {
     private String[] protocols;
 
     @Override
-    public void initialize(UriType uriType) {
+    public void initialize(final UriType uriType) {
         protocols = uriType.protocols();
         if (protocols == null || protocols.length == 0) {
             throw new ConstraintDefinitionException("protocols is emtpy.");
@@ -33,7 +33,7 @@ public class UriTypeValidator implements ConstraintValidator<UriType, String> {
     }
 
     @Override
-    public boolean isValid(String value, ConstraintValidatorContext context) {
+    public boolean isValid(final String value, final ConstraintValidatorContext context) {
         if (StringUtil.isNotBlank(value)) {
             return check(protocols, value);
         }