diff --git a/bundles/org.openhab.core.addon.marketplace.karaf/src/main/java/org/openhab/core/addon/marketplace/karaf/internal/community/CommunityKarafAddonHandler.java b/bundles/org.openhab.core.addon.marketplace.karaf/src/main/java/org/openhab/core/addon/marketplace/karaf/internal/community/CommunityKarafAddonHandler.java
index 037e402179..d7c24404f5 100644
--- a/bundles/org.openhab.core.addon.marketplace.karaf/src/main/java/org/openhab/core/addon/marketplace/karaf/internal/community/CommunityKarafAddonHandler.java
+++ b/bundles/org.openhab.core.addon.marketplace.karaf/src/main/java/org/openhab/core/addon/marketplace/karaf/internal/community/CommunityKarafAddonHandler.java
@@ -165,7 +165,7 @@ public class CommunityKarafAddonHandler implements MarketplaceAddonHandler {
                             "The local cache folder doesn't contain a single file: " + addonPath, null);
                 }
                 try {
-                    karService.install(karFiles.get(0).toUri(), false);
+                    karService.install(karFiles.getFirst().toUri(), false);
                 } catch (Exception e) {
                     throw new MarketplaceHandlerException(
                             "Cannot install KAR from marketplace cache: " + e.getMessage(), e);
diff --git a/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/AbstractJacksonYAMLParser.java b/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/AbstractJacksonYAMLParser.java
index 47c0c1a266..c564104d35 100644
--- a/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/AbstractJacksonYAMLParser.java
+++ b/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/AbstractJacksonYAMLParser.java
@@ -32,17 +32,17 @@ import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
 public abstract class AbstractJacksonYAMLParser<T> implements Parser<T> {
 
     /** The YAML object mapper instance */
-    protected static final ObjectMapper yamlMapper;
+    protected static final ObjectMapper YAML_MAPPER;
 
     static {
-        yamlMapper = new ObjectMapper(new YAMLFactory());
-        yamlMapper.findAndRegisterModules();
+        YAML_MAPPER = new ObjectMapper(new YAMLFactory());
+        YAML_MAPPER.findAndRegisterModules();
     }
 
     @Override
     public void serialize(Set<T> dataObjects, OutputStreamWriter writer) throws Exception {
         for (T dataObject : dataObjects) {
-            yamlMapper.writeValue(writer, dataObject);
+            YAML_MAPPER.writeValue(writer, dataObject);
         }
     }
 }
diff --git a/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/TemplateYAMLParser.java b/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/TemplateYAMLParser.java
index cc8359f387..8a6cdd115a 100644
--- a/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/TemplateYAMLParser.java
+++ b/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/internal/parser/jackson/TemplateYAMLParser.java
@@ -43,16 +43,16 @@ public class TemplateYAMLParser extends AbstractJacksonYAMLParser<Template> {
     public Set<Template> parse(InputStreamReader reader) throws ParsingException {
         try {
             Set<Template> templates = new HashSet<>();
-            JsonNode rootNode = yamlMapper.readTree(reader);
+            JsonNode rootNode = YAML_MAPPER.readTree(reader);
             if (rootNode.isArray()) {
-                List<RuleTemplateDTO> templateDtos = yamlMapper.convertValue(rootNode,
+                List<RuleTemplateDTO> templateDtos = YAML_MAPPER.convertValue(rootNode,
                         new TypeReference<List<RuleTemplateDTO>>() {
                         });
                 for (RuleTemplateDTO templateDTO : templateDtos) {
                     templates.add(RuleTemplateDTOMapper.map(templateDTO));
                 }
             } else {
-                RuleTemplateDTO templateDto = yamlMapper.convertValue(rootNode, new TypeReference<RuleTemplateDTO>() {
+                RuleTemplateDTO templateDto = YAML_MAPPER.convertValue(rootNode, new TypeReference<RuleTemplateDTO>() {
                 });
                 templates.add(RuleTemplateDTOMapper.map(templateDto));
             }
diff --git a/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/parser/ValidationException.java b/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/parser/ValidationException.java
index bc600b74a4..4ca261a4c8 100644
--- a/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/parser/ValidationException.java
+++ b/bundles/org.openhab.core.automation/src/main/java/org/openhab/core/automation/parser/ValidationException.java
@@ -12,6 +12,8 @@
  */
 package org.openhab.core.automation.parser;
 
+import java.io.Serial;
+
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.eclipse.jdt.annotation.Nullable;
 
@@ -23,6 +25,7 @@ import org.eclipse.jdt.annotation.Nullable;
 @NonNullByDefault
 public class ValidationException extends Exception {
 
+    @Serial
     private static final long serialVersionUID = 1L;
 
     /**
diff --git a/bundles/org.openhab.core.ephemeris/src/main/java/org/openhab/core/ephemeris/internal/EphemerisManagerImpl.java b/bundles/org.openhab.core.ephemeris/src/main/java/org/openhab/core/ephemeris/internal/EphemerisManagerImpl.java
index 394932c709..aaf3e43952 100644
--- a/bundles/org.openhab.core.ephemeris/src/main/java/org/openhab/core/ephemeris/internal/EphemerisManagerImpl.java
+++ b/bundles/org.openhab.core.ephemeris/src/main/java/org/openhab/core/ephemeris/internal/EphemerisManagerImpl.java
@@ -20,7 +20,7 @@ import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.nio.file.Files;
-import java.nio.file.Paths;
+import java.nio.file.Path;
 import java.time.DayOfWeek;
 import java.time.LocalDate;
 import java.time.ZonedDateTime;
@@ -223,7 +223,7 @@ public class EphemerisManagerImpl implements EphemerisManager, ConfigOptionProvi
     }
 
     private URL getUrl(String filename) throws FileNotFoundException {
-        if (Files.exists(Paths.get(filename))) {
+        if (Files.exists(Path.of(filename))) {
             try {
                 return (new URI("file:" + filename)).toURL();
             } catch (IllegalArgumentException | MalformedURLException | URISyntaxException e) {
diff --git a/bundles/org.openhab.core.io.websocket/src/main/java/org/openhab/core/io/websocket/log/LogWebSocket.java b/bundles/org.openhab.core.io.websocket/src/main/java/org/openhab/core/io/websocket/log/LogWebSocket.java
index 79c95f271c..a080040392 100644
--- a/bundles/org.openhab.core.io.websocket/src/main/java/org/openhab/core/io/websocket/log/LogWebSocket.java
+++ b/bundles/org.openhab.core.io.websocket/src/main/java/org/openhab/core/io/websocket/log/LogWebSocket.java
@@ -198,7 +198,7 @@ public class LogWebSocket implements LogListener {
         lastSentTime = System.currentTimeMillis();
 
         // Remove any duplicates from the live log buffer
-        long newestSequence = logs.get(0).getSequence();
+        long newestSequence = logs.getFirst().getSequence();
         synchronized (deferredLogs) {
             Iterator<LogDTO> iterator = deferredLogs.iterator();
             while (iterator.hasNext()) {
diff --git a/bundles/org.openhab.core.model.core/src/main/java/org/openhab/core/model/core/internal/ModelRepositoryImpl.java b/bundles/org.openhab.core.model.core/src/main/java/org/openhab/core/model/core/internal/ModelRepositoryImpl.java
index 08de70a83f..fce56c34ae 100644
--- a/bundles/org.openhab.core.model.core/src/main/java/org/openhab/core/model/core/internal/ModelRepositoryImpl.java
+++ b/bundles/org.openhab.core.model.core/src/main/java/org/openhab/core/model/core/internal/ModelRepositoryImpl.java
@@ -234,7 +234,6 @@ public class ModelRepositoryImpl implements ModelRepository {
 
     @Override
     public void generateSyntaxFromModel(OutputStream out, String modelType, EObject modelContent) {
-        String result = "";
         synchronized (resourceSet) {
             String name = "tmp_generated_syntax_%d.%s".formatted(++counter, modelType);
             Resource resource = resourceSet.createResource(URI.createURI(name));
diff --git a/bundles/org.openhab.core.model.yaml/src/main/java/org/openhab/core/model/yaml/internal/YamlModelRepositoryImpl.java b/bundles/org.openhab.core.model.yaml/src/main/java/org/openhab/core/model/yaml/internal/YamlModelRepositoryImpl.java
index 77d6cd2d0e..80f2c085c2 100644
--- a/bundles/org.openhab.core.model.yaml/src/main/java/org/openhab/core/model/yaml/internal/YamlModelRepositoryImpl.java
+++ b/bundles/org.openhab.core.model.yaml/src/main/java/org/openhab/core/model/yaml/internal/YamlModelRepositoryImpl.java
@@ -722,7 +722,6 @@ public class YamlModelRepositoryImpl implements WatchService.WatchEventListener,
                             errors.add("could not create new instance of %s".formatted(elementClass.getSimpleName()));
                         }
                     }
-
                 } else {
                     try {
                         elt = objectMapper.treeToValue(node, elementClass);
diff --git a/bundles/org.openhab.core.persistence/src/main/java/org/openhab/core/persistence/QueryablePersistenceService.java b/bundles/org.openhab.core.persistence/src/main/java/org/openhab/core/persistence/QueryablePersistenceService.java
index 6227192c5e..e3e67bd648 100644
--- a/bundles/org.openhab.core.persistence/src/main/java/org/openhab/core/persistence/QueryablePersistenceService.java
+++ b/bundles/org.openhab.core.persistence/src/main/java/org/openhab/core/persistence/QueryablePersistenceService.java
@@ -108,7 +108,6 @@ public interface QueryablePersistenceService extends PersistenceService {
      *
      * @param itemName name of item
      * @param alias alias of item
-     *
      * @return a {@link PersistedItem} or null if the item has not been persisted
      */
     default @Nullable PersistedItem persistedItem(String itemName, @Nullable String alias) {
diff --git a/bundles/org.openhab.core.semantics/src/main/java/org/openhab/core/semantics/internal/SemanticsServiceImpl.java b/bundles/org.openhab.core.semantics/src/main/java/org/openhab/core/semantics/internal/SemanticsServiceImpl.java
index d45a98f4d0..0d840cd6df 100644
--- a/bundles/org.openhab.core.semantics/src/main/java/org/openhab/core/semantics/internal/SemanticsServiceImpl.java
+++ b/bundles/org.openhab.core.semantics/src/main/java/org/openhab/core/semantics/internal/SemanticsServiceImpl.java
@@ -313,7 +313,7 @@ public class SemanticsServiceImpl implements SemanticsService, RegistryChangeLis
                 }
             }
         } else if (Equipment.class.isAssignableFrom(semanticTag)) {
-            if (parentLocations.size() > 0 && parentEquipments.size() > 0) {
+            if (!parentLocations.isEmpty() && !parentEquipments.isEmpty()) {
                 warnings.add(String.format(
                         "It belongs to location(s) %s and equipment(s) %s. An Equipment can only belong to one Location or another Equipment, but not both.",
                         parentLocations.toString(), parentEquipments.toString()));
@@ -333,7 +333,7 @@ public class SemanticsServiceImpl implements SemanticsService, RegistryChangeLis
                 warnings.add(String.format("It is a %s item, not a group. A location should be a Group Item.",
                         item.getType()));
             }
-            if (parentEquipments.size() > 0) {
+            if (!parentEquipments.isEmpty()) {
                 warnings.add(String.format(
                         "It belongs to equipment(s) %s. A Location can only belong to another Location, not Equipment.",
                         parentEquipments.toString()));
diff --git a/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/library/unit/CurrencyConverter.java b/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/library/unit/CurrencyConverter.java
index 21b8e77751..009ae0c953 100644
--- a/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/library/unit/CurrencyConverter.java
+++ b/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/library/unit/CurrencyConverter.java
@@ -12,6 +12,7 @@
  */
 package org.openhab.core.internal.library.unit;
 
+import java.io.Serial;
 import java.lang.reflect.Field;
 import java.math.BigDecimal;
 import java.math.MathContext;
@@ -34,6 +35,7 @@ import tech.units.indriya.function.Calculus;
  */
 @NonNullByDefault
 public class CurrencyConverter extends AbstractConverter {
+    @Serial
     private static final long serialVersionUID = 1L;
 
     private final BigDecimal factor;
diff --git a/bundles/org.openhab.core/src/main/java/org/openhab/core/items/GenericItem.java b/bundles/org.openhab.core/src/main/java/org/openhab/core/items/GenericItem.java
index 96b2de0a92..2d33c6d072 100644
--- a/bundles/org.openhab.core/src/main/java/org/openhab/core/items/GenericItem.java
+++ b/bundles/org.openhab.core/src/main/java/org/openhab/core/items/GenericItem.java
@@ -242,7 +242,6 @@ public abstract class GenericItem implements ActiveItem {
     public void setState(State state, @Nullable State lastState, @Nullable ZonedDateTime lastStateUpdate,
             @Nullable ZonedDateTime lastStateChange) {
         State oldState = this.state;
-        ZonedDateTime oldStateUpdate = this.lastStateUpdate;
         this.state = state;
         this.lastState = lastState != null ? lastState : this.lastState;
         this.lastStateUpdate = lastStateUpdate != null ? lastStateUpdate : this.lastStateUpdate;