diff --git a/.github/workflows/deploy_snapshot.yml b/.github/workflows/deploy_snapshot.yml
index 17278ca..7f04315 100644
--- a/.github/workflows/deploy_snapshot.yml
+++ b/.github/workflows/deploy_snapshot.yml
@@ -15,7 +15,8 @@ on:
     types: [ trigger_after_upstream_deploy ]
 
 env:
-  GRADLE_VERSION: 7.6 # Gradle version used
+  GRADLE_VERSION: 8.5 # Gradle version used
+  JAVA_VERSION:   21  # Java version used
   GRADLE_CLI_OPTS: "-Pci --build-cache --refresh-dependencies" # CLI options passed to Gradle
   GRADLE_BUILD_ACTION_CACHE_KEY_JOB: "test-cache-${{ github.head_ref }}.${{ github.sha }}"
 
@@ -29,6 +30,11 @@ jobs:
     steps:
       - name: Checkout project sources
         uses: actions/checkout@v4
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: ${{ env.JAVA_VERSION }}
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4
         with:
@@ -45,6 +51,11 @@ jobs:
     steps:
       - name: Checkout project sources
         uses: actions/checkout@v4
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: ${{ env.JAVA_VERSION }}
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4
         with:
diff --git a/.github/workflows/test_branch.yml b/.github/workflows/test_branch.yml
index f401ba2..aeb5d8a 100644
--- a/.github/workflows/test_branch.yml
+++ b/.github/workflows/test_branch.yml
@@ -12,7 +12,8 @@ on:
     branches-ignore: [ "dev" ] # Do not run this on the default branch
 
 env:
-  GRADLE_VERSION: 7.6 # Gradle version used
+  GRADLE_VERSION: 8.5 # Gradle version used
+  JAVA_VERSION:   21  # Java version used
   GRADLE_CLI_OPTS: "-Pci --build-cache --refresh-dependencies" # CLI options passed to Gradle
   GRADLE_BUILD_ACTION_CACHE_KEY_JOB: "test-cache-${{ github.head_ref }}.${{ github.sha }}"
 
@@ -26,6 +27,11 @@ jobs:
     steps:
       - name: Checkout project sources
         uses: actions/checkout@v4
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: ${{ env.JAVA_VERSION }}
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4
         with:
diff --git a/README.md b/README.md
index 91de8ee..8ea2522 100644
--- a/README.md
+++ b/README.md
@@ -54,7 +54,7 @@ used when processing models. To this effect, it provides funcionality for
 * storing symbols in symbol files,
 * ,and loading symbols from symbol files.
 
-The requirements for building and using the OD tool are that Java 11, Git, and Gradle are
+The requirements for building and using the OD tool are that Java 21, Git, and Gradle 8.5 are
 installed and available for use in Bash.
 
 The following subsection describes how to download the tool. Then, this document describes how
@@ -76,7 +76,7 @@ Alternatively, the tools can be built from source code.
 
 ### Prerequisites
 
-To build the project, it is required to install a Java 11 JDK and git.
+To build the project, it is required to install a Java 21 JDK and git.
 
 #### Step 1: Clone Project with git
 
diff --git a/build.gradle b/build.gradle
index 3659feb..4cc9284 100644
--- a/build.gradle
+++ b/build.gradle
@@ -5,11 +5,15 @@ plugins {
   id 'java-library'
   id 'maven-publish'
   id "de.monticore.generator" version "$mc_version" // MontiCore Plugin
-  id "com.github.johnrengelman.shadow" version "$shadow_plugin_version"
+  id "com.gradleup.shadow" version "$shadow_plugin_version"
   id 'jacoco'
   id "io.github.themrmilchmann.ecj" version "0.2.0"
 }
 
+ecj {
+  compilerVersion = "3.43.0"
+}
+
 def grammarDir = "src/main/grammars"
 
 group = "de.monticore.lang"
@@ -31,7 +35,7 @@ sourceSets {
 
 java {
   toolchain {
-    languageVersion = JavaLanguageVersion.of(11)
+    languageVersion = JavaLanguageVersion.of(21)
   }
   // Deprecated feature, published for compatibility reasons
   registerFeature('grammars') {
diff --git a/gradle.properties b/gradle.properties
index c83f8ba..d44a4e2 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -5,7 +5,7 @@ mc_version=7.9.0-SNAPSHOT
 mlc_version=7.8.0-SNAPSHOT
 version=7.9.0-SNAPSHOT
 useLocalRepo=false
-shadow_plugin_version=7.1.2
+shadow_plugin_version=8.3.9
 guava_version=33.5.0-jre
 commons_lang3_version=3.20.0
 commons_cli_version=1.11.0
diff --git a/src/main/java/de/monticore/od2plantuml/REPORT.md b/src/main/java/de/monticore/od2plantuml/REPORT.md
index 07cd4b8..0004fca 100644
--- a/src/main/java/de/monticore/od2plantuml/REPORT.md
+++ b/src/main/java/de/monticore/od2plantuml/REPORT.md
@@ -82,8 +82,8 @@ foo--> "blub" bar
 ## Usage of ODPlantUMLTool
 
 ### Dependencies 
-* Java 11 (or higher)
-* Gradle 7.5 (or higher)
+* Java 21 (or higher)
+* Gradle 8.5 (or higher)
 
 ### Installation of the project
 * Clone the project from Gitlab