Replace the chain of if/else with a switch expression.

pom.xml

@@ -17,8 +17,8 @@
   <properties>
     <java.version>25</java.version>
     <jacoco-maven-plugin.version>0.8.14</jacoco-maven-plugin.version>
-    <maven-checkstyle-plugin.version>3.5.0</maven-checkstyle-plugin.version>
-    <checkstyle.version>10.6.0</checkstyle.version>
+    <maven-checkstyle-plugin.version>3.6.0</maven-checkstyle-plugin.version>
+    <checkstyle.version>12.1.2</checkstyle.version>
     <lifecycle-mapping.version>1.0.0</lifecycle-mapping.version>
     <jjwt.version>0.12.6</jjwt.version>
     <okhttp.version>5.3.2</okhttp.version>
@@ -91,6 +91,13 @@
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-checkstyle-plugin</artifactId>
           <version>${maven-checkstyle-plugin.version}</version>
+          <dependencies>
+            <dependency>
+              <groupId>com.puppycrawl.tools</groupId>
+              <artifactId>checkstyle</artifactId>
+              <version>${checkstyle.version}</version>
+            </dependency>
+          </dependencies>
         </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
@@ -136,7 +143,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-gpg-plugin</artifactId>
-          <version>3.2.7</version>
+            <version>${maven-gpg-plugin.version}</version>
           <executions>
             <execution>
               <id>sign-artifacts</id>
@@ -188,7 +195,7 @@
         <plugin>
           <groupId>org.sonatype.central</groupId>
           <artifactId>central-publishing-maven-plugin</artifactId>
-          <version>0.9.0</version>
+            <version>${central-publishing-maven-plugin.version}</version>
           <extensions>true</extensions>
           <configuration>
             <publishingServerId>central</publishingServerId>

samples/delete-activity-profile/src/main/java/dev/learning/xapi/samples/deleteactivityprofile/DeleteActivityProfileApplication.java

@@ -23,6 +23,7 @@ public class DeleteActivityProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(DeleteActivityProfileApplication.class, args).close();
   }

samples/delete-agent-profile/src/main/java/dev/learning/xapi/samples/deleteagentprofile/DeleteAgentProfileApplication.java

@@ -23,6 +23,7 @@ public class DeleteAgentProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(DeleteAgentProfileApplication.class, args).close();
   }

samples/delete-state/src/main/java/dev/learning/xapi/samples/deletestate/DeleteStateApplication.java

@@ -23,6 +23,7 @@ public class DeleteStateApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(DeleteStateApplication.class, args).close();
   }

samples/delete-states/src/main/java/dev/learning/xapi/samples/deletestates/DeleteStatesApplication.java

@@ -23,6 +23,7 @@ public class DeleteStatesApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(DeleteStatesApplication.class, args).close();
   }

samples/get-about/src/main/java/dev/learning/xapi/samples/getabout/GetAboutApplication.java

@@ -23,6 +23,7 @@ public class GetAboutApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetAboutApplication.class, args).close();
   }

samples/get-activity-profile/src/main/java/dev/learning/xapi/samples/getactivityprofile/GetActivityProfileApplication.java

@@ -24,6 +24,7 @@ public class GetActivityProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetActivityProfileApplication.class, args).close();
   }

samples/get-activity-profiles/src/main/java/dev/learning/xapi/samples/getactivityprofiles/GetActivityProfilesApplication.java

@@ -25,6 +25,7 @@ public class GetActivityProfilesApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetActivityProfilesApplication.class, args).close();
   }

samples/get-activity/src/main/java/dev/learning/xapi/samples/getactivity/GetActivityApplication.java

@@ -27,6 +27,7 @@ public class GetActivityApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetActivityApplication.class, args).close();
   }

samples/get-agent-profile/src/main/java/dev/learning/xapi/samples/getagentprofile/GetAgentProfileApplication.java

@@ -24,6 +24,7 @@ public class GetAgentProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetAgentProfileApplication.class, args).close();
   }

samples/get-agent-profiles/src/main/java/dev/learning/xapi/samples/getagentprofiles/GetAgentProfilesApplication.java

@@ -23,6 +23,7 @@ public class GetAgentProfilesApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetAgentProfilesApplication.class, args).close();
   }

samples/get-agents/src/main/java/dev/learning/xapi/samples/getagents/GetAgentsApplication.java

@@ -26,6 +26,7 @@ public class GetAgentsApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetAgentsApplication.class, args).close();
   }

samples/get-more-statements/src/main/java/dev/learning/xapi/samples/getmorestatements/GetMoreStatementsApplication.java

@@ -24,6 +24,7 @@ public class GetMoreStatementsApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetMoreStatementsApplication.class, args).close();
   }

samples/get-state/src/main/java/dev/learning/xapi/samples/getstate/GetStateApplication.java

@@ -24,6 +24,7 @@ public class GetStateApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetStateApplication.class, args).close();
   }

samples/get-statement-iterator/src/main/java/dev/learning/xapi/samples/getstatements/GetStatementIteratorApplication.java

@@ -23,6 +23,7 @@ public class GetStatementIteratorApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetStatementIteratorApplication.class, args).close();
   }

samples/get-statement-with-attachment/src/main/java/dev/learning/xapi/samples/poststatement/GetStatementWithAttachmentApplication.java

@@ -32,6 +32,7 @@ public class GetStatementWithAttachmentApplication implements CommandLineRunner
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetStatementWithAttachmentApplication.class, args).close();
   }

samples/get-statement/src/main/java/dev/learning/xapi/samples/getstatement/GetStatementApplication.java

@@ -26,6 +26,7 @@ public class GetStatementApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetStatementApplication.class, args).close();
   }

samples/get-statements/src/main/java/dev/learning/xapi/samples/getstatements/GetStatementsApplication.java

@@ -24,6 +24,7 @@ public class GetStatementsApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetStatementsApplication.class, args).close();
   }

samples/get-states/src/main/java/dev/learning/xapi/samples/getstates/GetStatesApplication.java

@@ -25,6 +25,7 @@ public class GetStatesApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetStatesApplication.class, args).close();
   }

samples/get-voided-statement/src/main/java/dev/learning/xapi/samples/getvoidedstatement/GetVoidedStatementApplication.java

@@ -26,6 +26,7 @@ public class GetVoidedStatementApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(GetVoidedStatementApplication.class, args).close();
   }

samples/post-activity-profile/src/main/java/dev/learning/xapi/samples/postactivityprofile/PostActivityProfileApplication.java

@@ -23,6 +23,7 @@ public class PostActivityProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PostActivityProfileApplication.class, args).close();
   }

samples/post-agent-profile/src/main/java/dev/learning/xapi/samples/postagentprofile/PostAgentProfileApplication.java

@@ -23,6 +23,7 @@ public class PostAgentProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PostAgentProfileApplication.class, args).close();
   }

samples/post-signed-statement/src/main/java/dev/learning/xapi/samples/poststatement/PostSignedStatementApplication.java

@@ -29,6 +29,7 @@ public class PostSignedStatementApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PostSignedStatementApplication.class, args).close();
   }

samples/post-state/src/main/java/dev/learning/xapi/samples/poststate/PostStateApplication.java

@@ -23,6 +23,7 @@ public class PostStateApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PostStateApplication.class, args).close();
   }

samples/post-statement-with-attachment/src/main/java/dev/learning/xapi/samples/poststatement/PostStatementWithAttachmentApplication.java

@@ -29,6 +29,7 @@ public class PostStatementWithAttachmentApplication implements CommandLineRunner
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PostStatementWithAttachmentApplication.class, args).close();
   }

samples/post-statement/src/main/java/dev/learning/xapi/samples/poststatement/PostStatementApplication.java

@@ -25,6 +25,7 @@ public class PostStatementApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PostStatementApplication.class, args).close();
   }

samples/post-statements/src/main/java/dev/learning/xapi/samples/poststatements/PostStatementsApplication.java

@@ -24,6 +24,7 @@ public class PostStatementsApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PostStatementsApplication.class, args).close();
   }

samples/put-activity-profile/src/main/java/dev/learning/xapi/samples/putactivityprofile/PutActivityProfileApplication.java

@@ -23,6 +23,7 @@ public class PutActivityProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PutActivityProfileApplication.class, args).close();
   }

samples/put-agent-profile/src/main/java/dev/learning/xapi/samples/putagentprofile/PutAgentProfileApplication.java

@@ -23,6 +23,7 @@ public class PutAgentProfileApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PutAgentProfileApplication.class, args).close();
   }

samples/put-state/src/main/java/dev/learning/xapi/samples/putstate/PutStateApplication.java

@@ -23,6 +23,7 @@ public class PutStateApplication implements CommandLineRunner {
   /** Default xAPI client. Properties are picked automatically from application.properties. */
   @Autowired private XapiClient client;
 
+  /** Main method to start the application. */
   public static void main(String[] args) {
     SpringApplication.run(PutStateApplication.class, args).close();
   }

xapi-client/src/main/java/dev/learning/xapi/client/StatementHttpMessageWriter.java

@@ -164,14 +164,16 @@ private List<Object> getParts(Object object) {
 
     final var list = new ArrayList<>();
 
-    Stream<Attachment> attachments;
-    if (object instanceof final Statement statement) {
-      attachments = getRealAttachments(statement);
-    } else if (object instanceof final List<?> statements
-        && !statements.isEmpty()
-        && statements.get(0) instanceof Statement) {
-      attachments = ((List<Statement>) statements).stream().flatMap(this::getRealAttachments);
-    } else {
+    final Stream<Attachment> attachments =
+        switch (object) {
+          case Statement statement -> getRealAttachments(statement);
+          case List<?> statements
+              when !statements.isEmpty() && statements.get(0) instanceof Statement ->
+              ((List<Statement>) statements).stream().flatMap(this::getRealAttachments);
+          default -> null;
+        };
+
+    if (attachments == null) {
       // The object is not a statement or list of statements
       return list;
     }

xapi-client/src/test/java/dev/learning/xapi/client/configuration/XapiClientAutoConfigurationAuthorizationTest.java

@@ -49,7 +49,7 @@ public void accept(Builder builder) {
       mockWebServer = new MockWebServer();
       try {
         mockWebServer.start();
-      } catch (final IOException e) {
+      } catch (final IOException e) { // Named parameter required by Google Java Style
         // Ignore - test will fail if server doesn't start
       }
       builder.baseUrl(mockWebServer.url("").toString());

xapi-client/src/test/java/dev/learning/xapi/client/configuration/XapiClientAutoConfigurationUsernamePasswordTest.java

@@ -49,7 +49,7 @@ public void accept(Builder builder) {
       mockWebServer = new MockWebServer();
       try {
         mockWebServer.start();
-      } catch (final IOException e) {
+      } catch (final IOException e) { // Named parameter required by Google Java Style
         // Ignore - test will fail if server doesn't start
       }
       builder.baseUrl(mockWebServer.url("").toString());

xapi-model/src/main/java/dev/learning/xapi/jackson/LocaleSerializer.java

@@ -21,6 +21,7 @@ public class LocaleSerializer extends StdSerializer<Locale> {
 
   private static final long serialVersionUID = 7182941951585541965L;
 
+  /** Default constructor. */
   public LocaleSerializer() {
     super(Locale.class);
   }
@@ -40,6 +41,7 @@ public static class LocaleKeySerializer extends StdSerializer<Locale> {
 
     private static final long serialVersionUID = 7182941951585541965L;
 
+    /** Default constructor. */
     public LocaleKeySerializer() {
       super(Locale.class);
     }

xapi-model/src/main/java/dev/learning/xapi/jackson/StrictLocaleDeserializer.java

@@ -53,7 +53,7 @@ static Locale validateLocale(String localeString, DeserializationContext deseria
       // test validity of language and country codes (throws exception)
       locale.getISO3Language();
       locale.getISO3Country();
-    } catch (final MissingResourceException e) {
+    } catch (final MissingResourceException e) { // Named parameter required by Google Java Style
       locale = null;
     }
     // test the validity of the whole key

xapi-model/src/main/java/dev/learning/xapi/model/validation/disableable/ValidatorDisabler.java

@@ -15,5 +15,11 @@ public interface ValidatorDisabler {
   public static final ValidatorDisabler DEFAULT_DISABLER = v -> true;
   public static final ValidatorDisabler DEFAULT_ENABLER = v -> false;
 
+  /**
+   * Checks whether the given validator is disabled.
+   *
+   * @param validator the validator to check
+   * @return true if the validator is disabled, false otherwise
+   */
   public boolean isDisabled(DisableableValidator<?, ?> validator);
 }