diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
new file mode 100644
index 0000000..27072fd
--- /dev/null
+++ b/.devcontainer/devcontainer.json
@@ -0,0 +1,40 @@
+{
+  "name": "DocRaptor Java",
+  "image": "mcr.microsoft.com/devcontainers/java:21",
+  "features": {
+    "ghcr.io/devcontainers/features/java:1": {
+      "version": "21",
+      "jdkDistro": "tem",
+      "installGradle": "true",
+      "installMaven": "true",
+      "additionalVersions": "8"
+    },
+    "ghcr.io/devcontainers/features/git-lfs:1": {}
+  },
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "vscjava.vscode-java-pack",
+        "vscjava.vscode-gradle",
+        "redhat.java"
+      ],
+      "settings": {
+        "java.configuration.updateBuildConfiguration": "automatic",
+        "java.compile.nullAnalysis.mode": "automatic",
+        "java.configuration.runtimes": [
+          {
+            "name": "JavaSE-21",
+            "path": "/usr/lib/jvm/msopenjdk-21",
+            "default": true
+          },
+          {
+            "name": "JavaSE-1.8",
+            "path": "/usr/lib/jvm/msopenjdk-8"
+          }
+        ]
+      }
+    }
+  },
+  "postCreateCommand": "echo 'Java 21:' && /usr/lib/jvm/msopenjdk-21/bin/java -version && echo 'Java 8:' && /usr/lib/jvm/msopenjdk-8/bin/java -version",
+  "remoteUser": "vscode"
+}
diff --git a/pom.xml b/pom.xml
index 1c943bf..36d045a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -36,10 +36,8 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.1</version>
+                <version>3.14.1</version>
                 <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
                     <fork>true</fork>
                     <meminitial>128m</meminitial>
                     <maxmem>512m</maxmem>
@@ -47,6 +45,7 @@
                         <arg>-Xlint:all</arg>
                         <arg>-J-Xss4m</arg><!-- Compiling the generated JSON.java file may require larger stack size. -->
                     </compilerArgs>
+                    <release>21</release>
                 </configuration>
             </plugin>
 
@@ -223,6 +222,11 @@
             <artifactId>swagger-annotations</artifactId>
             <version>${swagger-annotations-version}</version>
         </dependency>
+        <dependency>
+            <groupId>jakarta.annotation</groupId>
+            <artifactId>jakarta.annotation-api</artifactId>
+            <version>1.3.5</version>
+        </dependency>
 
         <!-- @Nullable annotation -->
         <dependency>
diff --git a/src/main/java/com/docraptor/ApiClient.java b/src/main/java/com/docraptor/ApiClient.java
index 4f099fe..41b8de3 100644
--- a/src/main/java/com/docraptor/ApiClient.java
+++ b/src/main/java/com/docraptor/ApiClient.java
@@ -238,8 +238,8 @@ public Authentication getAuthentication(String authName) {
    */
   public void setUsername(String username) {
     for (Authentication auth : authentications.values()) {
-      if (auth instanceof HttpBasicAuth) {
-        ((HttpBasicAuth) auth).setUsername(username);
+      if (auth instanceof HttpBasicAuth basicAuth) {
+        basicAuth.setUsername(username);
         return;
       }
     }
@@ -252,8 +252,8 @@ public void setUsername(String username) {
    */
   public void setPassword(String password) {
     for (Authentication auth : authentications.values()) {
-      if (auth instanceof HttpBasicAuth) {
-        ((HttpBasicAuth) auth).setPassword(password);
+      if (auth instanceof HttpBasicAuth basicAuth) {
+        basicAuth.setPassword(password);
         return;
       }
     }
@@ -391,11 +391,11 @@ public String formatDate(Date date) {
   public String parameterToString(Object param) {
     if (param == null) {
       return "";
-    } else if (param instanceof Date) {
-      return formatDate((Date) param);
-    } else if (param instanceof Collection) {
+    } else if (param instanceof Date date) {
+      return formatDate(date);
+    } else if (param instanceof Collection<?> collection) {
       StringBuilder b = new StringBuilder();
-      for(Object o : (Collection<?>)param) {
+      for(Object o : collection) {
         if(b.length() > 0) {
           b.append(',');
         }
@@ -560,7 +560,7 @@ public Object serialize(Object obj, String contentType, Map<String, Object> form
       FormDataMultiPart mp = new FormDataMultiPart();
       for (Entry<String, Object> param: formParams.entrySet()) {
         if( param.getValue() instanceof List && !( ( List ) param.getValue() ).isEmpty()
-                  && ( ( List ) param.getValue() ).get( 0 ) instanceof File ) {
+                  && ( ( List ) param.getValue() ).getFirst() instanceof File ) {
             @SuppressWarnings( "unchecked" )
             List<File> files = ( List<File> ) param.getValue();
             for( File file : files ) {
@@ -594,8 +594,7 @@ private String buildUrl(String path, List<Pair> queryParams, List<Pair> collecti
     String baseURL;
     if (serverIndex != null) {
       if (serverIndex < 0 || serverIndex >= servers.size()) {
-        throw new ArrayIndexOutOfBoundsException(String.format(
-          "Invalid index %d when selecting the host settings. Must be less than %d", serverIndex, servers.size()
+        throw new ArrayIndexOutOfBoundsException("Invalid index %d when selecting the host settings. Must be less than %d".formatted(serverIndex, servers.size()
         ));
       }
       baseURL = servers.get(serverIndex).URL(serverVariables);
diff --git a/src/main/java/com/docraptor/RFC3339DateFormat.java b/src/main/java/com/docraptor/RFC3339DateFormat.java
index 10aeb8f..9a28dfb 100644
--- a/src/main/java/com/docraptor/RFC3339DateFormat.java
+++ b/src/main/java/com/docraptor/RFC3339DateFormat.java
@@ -14,6 +14,7 @@
 
 import com.fasterxml.jackson.databind.util.StdDateFormat;
 
+import java.io.Serial;
 import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
@@ -23,6 +24,7 @@
 import java.util.TimeZone;
 
 public class RFC3339DateFormat extends DateFormat {
+  @Serial
   private static final long serialVersionUID = 1L;
   private static final TimeZone TIMEZONE_Z = TimeZone.getTimeZone("UTC");