diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
index 7b319b78..bcea8e79 100644
--- a/.devcontainer/Dockerfile
+++ b/.devcontainer/Dockerfile
@@ -1,8 +1,8 @@
 # See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.238.0/containers/java/.devcontainer/base.Dockerfile
 
 # [Choice] Java version (use -bullseye variants on local arm64/Apple Silicon): 11, 17, 11-bullseye, 17-bullseye, 11-buster, 17-buster
-ARG VARIANT="17-bullseye"
-FROM mcr.microsoft.com/vscode/devcontainers/java:0-${VARIANT}
+ARG VARIANT="21-bullseye"
+FROM mcr.microsoft.com/vscode/devcontainers/java:1.1.0-${VARIANT}
 
 # [Option] Install Maven
 ARG INSTALL_MAVEN="false"
diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index 3994bec7..fdc7cdbd 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -8,7 +8,7 @@
 			// Update the VARIANT arg to pick a Java version: 11, 17
 			// Append -bullseye or -buster to pin to an OS version.
 			// Use the -bullseye variants on local arm64/Apple Silicon.
-			"VARIANT": "17-bullseye",
+			"VARIANT": "21-bullseye",
 			// Options
 			"INSTALL_MAVEN": "true",
 			"INSTALL_GRADLE": "true",
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index faf5dd6a..14a4ce5f 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -6,10 +6,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Set up JDK 17
+      - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'adopt'
       - name: Build with Maven
         run: mvn --batch-mode --update-snapshots verify
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index f447eb95..ff76b1af 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -26,10 +26,10 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Set up JDK 17
+      - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'adopt'
 
       - name: Initialize CodeQL
diff --git a/.gitpod.dockerfile b/.gitpod.dockerfile
index 1f0020db..0bba1827 100644
--- a/.gitpod.dockerfile
+++ b/.gitpod.dockerfile
@@ -1,4 +1,4 @@
-FROM gitpod/workspace-java-17:2024-05-13-09-12-40
+FROM gitpod/workspace-java-21:2024-05-15-13-36-34
 
 ENV LLVM_SCRIPT="tmp_llvm.sh"
 
diff --git a/pom.xml b/pom.xml
index 1ba57f57..2c2f640d 100644
--- a/pom.xml
+++ b/pom.xml
@@ -10,8 +10,8 @@
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
         <assertj.version>3.25.3</assertj.version>
     </properties>
 
@@ -73,8 +73,8 @@
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.13.0</version>
                 <configuration>
-                    <source>17</source>
-                    <target>17</target>
+                    <source>21</source>
+                    <target>21</target>
                     <compilerArgs>
                         <arg>-Xlint:all</arg>
                         <arg>-Xlint:-auxiliaryclass</arg>
@@ -82,6 +82,8 @@
                         <arg>-Xlint:-serial</arg>
                         <arg>-Xlint:-try</arg>
                         <arg>-Xlint:-unchecked</arg>
+                        <arg>-Xlint:-lossy-conversions</arg>
+                        <arg>-Xlint:-this-escape</arg>
                         <arg>-Werror</arg>
                     </compilerArgs>
                 </configuration>