diff --git a/src/main/java/org/codelibs/fess/api/BaseApiManager.java b/src/main/java/org/codelibs/fess/api/BaseApiManager.java
index 4ac4e26b6f30ee7dd7372b113cdae062066d6456..54bf9ee9ec08f346747d9e76f8a251cb88fb1e3a 100644
--- a/src/main/java/org/codelibs/fess/api/BaseApiManager.java
+++ b/src/main/java/org/codelibs/fess/api/BaseApiManager.java
@@ -68,29 +68,35 @@ public abstract class BaseApiManager implements WebApiManager {
         }
         if (value == null) {
             return FormatType.SEARCH;
-        } else {
-            final String type = value.toUpperCase(Locale.ROOT);
-            if (FormatType.SEARCH.name().equals(type)) {
-                return FormatType.SEARCH;
-            } else if (FormatType.LABEL.name().equals(type)) {
-                return FormatType.LABEL;
-            } else if (FormatType.POPULARWORD.name().equals(type)) {
-                return FormatType.POPULARWORD;
-            } else if (FormatType.FAVORITE.name().equals(type)) {
-                return FormatType.FAVORITE;
-            } else if (FormatType.FAVORITES.name().equals(type)) {
-                return FormatType.FAVORITES;
-            } else if (FormatType.PING.name().equals(type)) {
-                return FormatType.PING;
-            } else if (FormatType.SCROLL.name().equals(type)) {
-                return FormatType.SCROLL;
-            } else if (FormatType.SUGGEST.name().equals(type)) {
-                return FormatType.SUGGEST;
-            } else {
-                // default
-                return FormatType.OTHER;
-            }
         }
+        final String type = value.toUpperCase(Locale.ROOT);
+        if (FormatType.SEARCH.name().equals(type)) {
+            return FormatType.SEARCH;
+        }
+        if (FormatType.LABEL.name().equals(type)) {
+            return FormatType.LABEL;
+        }
+        if (FormatType.POPULARWORD.name().equals(type)) {
+            return FormatType.POPULARWORD;
+        }
+        if (FormatType.FAVORITE.name().equals(type)) {
+            return FormatType.FAVORITE;
+        }
+        if (FormatType.FAVORITES.name().equals(type)) {
+            return FormatType.FAVORITES;
+        }
+        if (FormatType.PING.name().equals(type)) {
+            return FormatType.PING;
+        }
+        if (FormatType.SCROLL.name().equals(type)) {
+            return FormatType.SCROLL;
+        }
+        if (FormatType.SUGGEST.name().equals(type)) {
+            return FormatType.SUGGEST;
+        }
+
+        // default
+        return FormatType.OTHER;
     }
 
     protected void write(final String text, final String contentType, final String encoding) {
diff --git a/src/main/java/org/codelibs/fess/api/json/SearchApiManager.java b/src/main/java/org/codelibs/fess/api/json/SearchApiManager.java
index c556d9c942fd3f42707d6d235f192984f5360e72..34183dbcbedc0bda47b255f1e3e10e2f30e2840b 100644
--- a/src/main/java/org/codelibs/fess/api/json/SearchApiManager.java
+++ b/src/main/java/org/codelibs/fess/api/json/SearchApiManager.java
@@ -127,22 +127,27 @@ public class SearchApiManager extends BaseApiManager {
             }
             // return FormatType.SCROLL;
             return FormatType.SEARCH;
-        } else if ("labels".equals(type)) {
+        }
+        if ("labels".equals(type)) {
             return FormatType.LABEL;
-        } else if ("popular-words".equals(type)) {
+        }
+        if ("popular-words".equals(type)) {
             return FormatType.POPULARWORD;
-        } else if ("favorites".equals(type)) {
+        }
+        if ("favorites".equals(type)) {
             return FormatType.FAVORITES;
-        } else if ("health".equals(type)) {
+        }
+        if ("health".equals(type)) {
             return FormatType.PING;
-        } else if ("suggest-words".equals(type)) {
+        }
+        if ("suggest-words".equals(type)) {
             return FormatType.SUGGEST;
-        } else if ("scroll".equals(type)) {
+        }
+        if ("scroll".equals(type)) {
             return FormatType.SCROLL;
-        } else {
-            // default
-            return FormatType.OTHER;
         }
+        // default
+        return FormatType.OTHER;
     }
 
     @Override
@@ -192,7 +197,7 @@ public class SearchApiManager extends BaseApiManager {
 
     protected boolean acceptHttpMethod(final HttpServletRequest request, final String... methods) {
         final String method = request.getMethod();
-        for (String m : methods) {
+        for (final String m : methods) {
             if (m.equals(method)) {
                 return true;
             }
diff --git a/src/main/java/org/codelibs/fess/es/client/SearchEngineClient.java b/src/main/java/org/codelibs/fess/es/client/SearchEngineClient.java
index d49b1ad3f7bf03ff7ef1c0f30259ceb344f2f147..9279480dac0428153bcacb1dbaa0d2a65e237f59 100644
--- a/src/main/java/org/codelibs/fess/es/client/SearchEngineClient.java
+++ b/src/main/java/org/codelibs/fess/es/client/SearchEngineClient.java
@@ -1211,7 +1211,7 @@ public class SearchEngineClient implements Client {
             throw new SearchEngineClientException(response.buildFailureMessage());
         }
 
-        return Arrays.stream(response.getItems()).map(res -> res.getId()).toArray(n -> new String[n]);
+        return Arrays.stream(response.getItems()).map(BulkItemResponse::getId).toArray(n -> new String[n]);
     }
 
     public static class SearchConditionBuilder {
diff --git a/src/main/java/org/codelibs/fess/helper/ActivityHelper.java b/src/main/java/org/codelibs/fess/helper/ActivityHelper.java
index d42506ca69ae62e47606d792f420df3e59dda0e8..741714e9a837704b77be2d2e690b915fbeff693a 100644
--- a/src/main/java/org/codelibs/fess/helper/ActivityHelper.java
+++ b/src/main/java/org/codelibs/fess/helper/ActivityHelper.java
@@ -82,7 +82,7 @@ public class ActivityHelper {
         valueMap.put("action", Action.LOGIN_FAILURE.name());
         credential.ifPresent(c -> {
             valueMap.put("class", c.getClass().getSimpleName());
-            if (c instanceof FessCredential fessCredential) {
+            if (c instanceof final FessCredential fessCredential) {
                 valueMap.put("user", fessCredential.getUserId());
             }
         });
@@ -177,15 +177,15 @@ public class ActivityHelper {
         this.permissionSeparator = permissionSeparator;
     }
 
-    public void setEcsVersion(String ecsVersion) {
+    public void setEcsVersion(final String ecsVersion) {
         this.ecsVersion = ecsVersion;
     }
 
-    public void setEcsServiceName(String ecsServiceName) {
+    public void setEcsServiceName(final String ecsServiceName) {
         this.ecsServiceName = ecsServiceName;
     }
 
-    public void setEcsEventDataset(String ecsEventDataset) {
+    public void setEcsEventDataset(final String ecsEventDataset) {
         this.ecsEventDataset = ecsEventDataset;
     }
 }
diff --git a/src/main/java/org/codelibs/fess/helper/SuggestHelper.java b/src/main/java/org/codelibs/fess/helper/SuggestHelper.java
index 520a7306419328e4f40f70add6a845040c5c7366..171d8113fc1adc9e488a980ff2636442922c485a 100644
--- a/src/main/java/org/codelibs/fess/helper/SuggestHelper.java
+++ b/src/main/java/org/codelibs/fess/helper/SuggestHelper.java
@@ -398,7 +398,7 @@ public class SuggestHelper {
         }
     }
 
-    public void setSearchStoreInterval(long searchStoreInterval) {
+    public void setSearchStoreInterval(final long searchStoreInterval) {
         this.searchStoreInterval = searchStoreInterval;
     }
 }
diff --git a/src/main/java/org/codelibs/fess/thumbnail/ThumbnailManager.java b/src/main/java/org/codelibs/fess/thumbnail/ThumbnailManager.java
index 9bedad9262342325477eed5927ff076b2e4d9c59..3634374b85a7b5e053ef27e1d0129b168bfbf9d5 100644
--- a/src/main/java/org/codelibs/fess/thumbnail/ThumbnailManager.java
+++ b/src/main/java/org/codelibs/fess/thumbnail/ThumbnailManager.java
@@ -543,7 +543,7 @@ public class ThumbnailManager {
         this.noImageExpired = noImageExpired;
     }
 
-    public void setSplitHashSize(int splitHashSize) {
+    public void setSplitHashSize(final int splitHashSize) {
         this.splitHashSize = splitHashSize;
     }
 
diff --git a/src/main/java/org/codelibs/fess/thumbnail/impl/BaseThumbnailGenerator.java b/src/main/java/org/codelibs/fess/thumbnail/impl/BaseThumbnailGenerator.java
index 96ee146665953552d1ceacf670d5c403dcad237e..dbbadfe3042169ab58318510e52b3420c29eb742 100644
--- a/src/main/java/org/codelibs/fess/thumbnail/impl/BaseThumbnailGenerator.java
+++ b/src/main/java/org/codelibs/fess/thumbnail/impl/BaseThumbnailGenerator.java
@@ -84,7 +84,7 @@ public abstract class BaseThumbnailGenerator implements ThumbnailGenerator {
             return false;
         }
         for (final Map.Entry<String, String> entry : conditionMap.entrySet()) {
-            if (docMap.get(entry.getKey()) instanceof String value && value.matches(entry.getValue())) {
+            if (docMap.get(entry.getKey()) instanceof final String value && value.matches(entry.getValue())) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("[{}] match {}:{}", entry.getKey(), name, value);
                 }
diff --git a/src/main/java/org/codelibs/fess/util/SearchEngineUtil.java b/src/main/java/org/codelibs/fess/util/SearchEngineUtil.java
index 023af4fade526712764ca5b45a766377cfb9126e..bc40b795df4ee6cdf3135d986c5c2b04c78b92c7 100644
--- a/src/main/java/org/codelibs/fess/util/SearchEngineUtil.java
+++ b/src/main/java/org/codelibs/fess/util/SearchEngineUtil.java
@@ -63,7 +63,7 @@ public final class SearchEngineUtil {
     public static String getXContentString(final ToXContent xContent, final XContentType xContentType) {
         try {
             return XContentHelper.toXContent(xContent, xContentType, ToXContent.EMPTY_PARAMS, false).utf8ToString();
-        } catch (IOException e) {
+        } catch (final IOException e) {
             throw new IORuntimeException(e);
         }
     }