chore: migrate from Java 9 to Java 11

- Update maven-compiler-plugin to 3.11.0 with <release>11</release>
- Add maven-surefire-plugin 3.2.5
- Add maven-enforcer-plugin 3.5.0 requiring JDK [11,)
- Add maven-javadoc-plugin 3.6.3 with -Xdoclint:none
- Upgrade JUnit from 4.11 to 4.13.2
- Upgrade JMH from 1.17.4 to 1.37
- Add GitHub Actions CI workflow for JDK 11
- Add MIGRATION_NOTES.md documenting all changes
- Update README.md to state JDK 11 requirement
- Update .gitignore to allow .github directory

Co-Authored-By: Lukas Burger <lukas.burger@cognition.ai>

Author: devin-ai-integration[bot]

.github/workflows/build.yml

@@ -0,0 +1,27 @@
+name: Java CI with Maven
+
+on:
+  push:
+    branches: [ master, 'devin/**' ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up JDK 11
+        uses: actions/setup-java@v4
+        with:
+          java-version: '11'
+          distribution: 'temurin'
+          cache: maven
+
+      - name: Build with Maven
+        run: mvn -B compile --file pom.xml
+
+      - name: Run tests
+        run: mvn -B test --file pom.xml

.gitignore

@@ -4,6 +4,7 @@
 # Eclipse, Netbeans and IntelliJ files
 /.*
 !.gitignore
+!.github
 /nbproject
 /*.ipr
 /*.iws

MIGRATION_NOTES.md

@@ -0,0 +1,52 @@
+# Migration Notes: Java 9 to Java 11
+
+## Overview
+
+This document describes the changes made to migrate the Java8InAction codebase from Java 9 (source/target 1.9) to Java 11.
+
+## Build Tool Changes (`pom.xml`)
+
+### Compiler Configuration
+- **Before**: `maven-compiler-plugin` 3.1 with `<source>1.9</source>` / `<target>1.9</target>`
+- **After**: `maven-compiler-plugin` 3.11.0 with `<release>11</release>`
+- Added `<maven.compiler.release>11</maven.compiler.release>` property for IDE tooling
+
+### Plugin Additions
+| Plugin | Version | Purpose |
+|--------|---------|---------|
+| `maven-compiler-plugin` | 3.11.0 | Upgraded from 3.1; uses `<release>` instead of source/target |
+| `maven-surefire-plugin` | 3.2.5 | Test runner compatible with Java 11+ |
+| `maven-enforcer-plugin` | 3.5.0 | Enforces minimum JDK 11 at build time |
+| `maven-javadoc-plugin` | 3.6.3 | Configured with `-Xdoclint:none` for lenient Javadoc |
+
+### Dependency Updates
+| Dependency | Old Version | New Version | Notes |
+|-----------|-------------|-------------|-------|
+| JUnit | 4.11 | 4.13.2 | Latest 4.x release; security and bug fixes |
+| JMH (jmh-core) | 1.17.4 | 1.37 | Latest release; full Java 11+ support |
+| JMH (jmh-generator-annprocess) | 1.17.4 | 1.37 | Kept in sync with jmh-core |
+
+### Encoding
+- `<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>` was already present (retained)
+
+## CI/CD
+- Added `.github/workflows/build.yml` — GitHub Actions workflow running `mvn compile` and `mvn test` on JDK 11 (Temurin) with Maven dependency caching
+
+## Source Code Changes
+- **None required.** The codebase compiled cleanly on Java 11 without any source modifications.
+- No JAXB, JavaFX, JAX-WS, CORBA, or Nashorn APIs are used, so no removals were necessary.
+- No module-info.java was added; the project continues to use the classpath (no JPMS).
+
+## Build Warnings (informational, not errors)
+- `maven-shade-plugin` missing explicit version (pre-existing, not introduced by this migration)
+- Deprecation warning in `lambdasinaction/chap11/Util.java` (pre-existing)
+- Unchecked operations warning in `lambdasinaction/appc/StreamForker.java` (pre-existing)
+
+## Testing
+- No test sources exist in the repository (`src/test/` directory absent)
+- `mvn test` succeeds with "No tests to run"
+
+## Compatibility
+- **Minimum JDK**: 11 (enforced by `maven-enforcer-plugin`)
+- **Build system**: Maven 3.6+
+- **No breaking changes** to the educational examples

README.md

@@ -29,17 +29,16 @@ The source code for all examples can be found in the directory [src/main/java/la
 * Appendix D: Lambdas and JVM bytecode
 We will update the repository as we update the book. Stay tuned!
 
-### Make sure to have JDK8 installed
-The latest binary can be found here: http://www.oracle.com/technetwork/java/javase/overview/java8-2100321.html
+### Requirements
 
-$ java -version
+**JDK 11** or later is required to build and run the examples.
 
-java version "1.8.0_05"
-Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
-Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)
+You can install it via [Adoptium (Eclipse Temurin)](https://adoptium.net/) or your system package manager.
 
+    $ java -version
+    openjdk version "11.0.x" ...
 
-You can download a preview version here: https://jdk8.java.net/
+See [MIGRATION_NOTES.md](MIGRATION_NOTES.md) for details on the Java 9 to 11 migration.
 
 ### Compile/Run the examples
 Using maven:

pom.xml

@@ -10,23 +10,24 @@
 
     <properties>
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+      <maven.compiler.release>11</maven.compiler.release>
     </properties>
 
   <dependencies>
     <dependency>
       <groupId>org.openjdk.jmh</groupId>
       <artifactId>jmh-core</artifactId>
-      <version>1.17.4</version>
+      <version>1.37</version>
     </dependency>
     <dependency>
       <groupId>org.openjdk.jmh</groupId>
       <artifactId>jmh-generator-annprocess</artifactId>
-      <version>1.17.4</version>
+      <version>1.37</version>
     </dependency>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
-      <version>4.11</version>
+      <version>4.13.2</version>
     </dependency>
   </dependencies>
 
@@ -35,10 +36,42 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>3.1</version>
+        <version>3.11.0</version>
         <configuration>
-          <source>1.9</source>
-          <target>1.9</target>
+          <release>11</release>
+        </configuration>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>3.2.5</version>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-enforcer-plugin</artifactId>
+        <version>3.5.0</version>
+        <executions>
+          <execution>
+            <id>enforce-java</id>
+            <goals>
+              <goal>enforce</goal>
+            </goals>
+            <configuration>
+              <rules>
+                <requireJavaVersion>
+                  <version>[11,)</version>
+                </requireJavaVersion>
+              </rules>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-javadoc-plugin</artifactId>
+        <version>3.6.3</version>
+        <configuration>
+          <additionalJOption>-Xdoclint:none</additionalJOption>
         </configuration>
       </plugin>
       <plugin>
@@ -63,4 +96,4 @@
       </plugin>
     </plugins>
   </build>
-</project>
+</project>