build(maven): target Java 11 via release; upgrade plugins and deps

- maven-compiler-plugin 3.1 → 3.11.0 with <release>11</release>
- Add maven-surefire-plugin 3.2.5, maven-enforcer-plugin 3.5.0
- JMH 1.17.4 → 1.37, JUnit 4.11 → 4.13.2
- Fix deprecated new Double(String) → Double.parseDouble()
- Add GitHub Actions CI workflow for JDK 11
- Add MIGRATION_NOTES.md, update README.md for JDK 11
- Update .gitignore to allow .github directory

Co-Authored-By: derek.wu <derekwu35@gmail.com>

Author: devin-ai-integration[bot]

.github/workflows/java11-build.yml

@@ -0,0 +1,19 @@
+name: Java 11 Build
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup JDK 11
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '11'
+          cache: maven
+      - name: Compile
+        run: mvn -B -e clean compile
+      - name: Package (includes JMH shade)
+        run: mvn -B -e -DskipTests package

.gitignore

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

MIGRATION_NOTES.md

@@ -0,0 +1,56 @@
+# Java 9 → 11 Migration Notes
+
+## Summary
+
+This project has been migrated from Java 9 (`source`/`target` 1.9) to **Java 11 (LTS)** using the `release` compiler flag. The migration is minimal and behavior-safe, targeting build and dependency compatibility.
+
+## Build Changes
+
+### Maven Compiler Plugin
+- **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>`
+
+### New Plugins
+- `maven-surefire-plugin` 3.2.5 — modern test runner compatible with Java 11+
+- `maven-enforcer-plugin` 3.5.0 — enforces JDK 11 as the minimum build version
+
+### Dependency Upgrades
+| Dependency | Old Version | New Version | Reason |
+|---|---|---|---|
+| JMH (core + annprocess) | 1.17.4 | 1.37 | Java 11 compatibility |
+| JUnit | 4.11 | 4.13.2 | Security fixes, Java 11 support |
+
+## Code Changes
+
+- `Util.java`: Replaced `new Double(String)` (deprecated since Java 9, marked for removal) with `Double.parseDouble(String)`.
+
+## Removed JDK Modules
+
+No removed JDK modules (JAXB, JAX-WS, CORBA, JavaFX, Nashorn) were in use — no replacement dependencies needed.
+
+## Encapsulation / JPMS
+
+The project runs on the **classpath** (no `module-info.java`). No illegal reflective access warnings are present.
+
+## Known Warnings (Intentional)
+
+- `DateTimeExamples.java` uses the deprecated `Date(int, int, int)` constructor — this is intentional for the educational example contrasting old and new Date/Time APIs.
+- `StreamForker.java` uses unchecked/unsafe operations — inherent to the generics example.
+
+## CI
+
+A GitHub Actions workflow (`.github/workflows/java11-build.yml`) has been added to build and compile on JDK 11 (Temurin).
+
+## GC / Logging
+
+No JVM flags or GC options were configured in this project. The default G1 collector in Java 11 applies.
+
+## TLS / Security
+
+No TLS endpoints, keystores, or cipher configurations exist in this codebase.
+
+## Follow-ups
+
+- Consider adopting `var` (Java 10) for local type inference in examples.
+- Consider adding `java.net.http.HttpClient` (Java 11) usage examples.
+- Consider adding test classes under `src/test/java/`.

README.md

@@ -29,17 +29,13 @@ 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: JDK 11+
+Install [Eclipse Temurin 11](https://adoptium.net/temurin/releases/?version=11) (or any JDK 11+ distribution).
 
-$ java -version
+    $ java -version
+    openjdk version "11.0.x" ...
 
-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 download a preview version here: https://jdk8.java.net/
+See [MIGRATION_NOTES.md](MIGRATION_NOTES.md) for details on the Java 9 → 11 migration.
 
 ### Compile/Run the examples
 Using maven:

pom.xml

@@ -9,24 +9,25 @@
     <version>1.0</version>
 
     <properties>
+      <maven.compiler.release>11</maven.compiler.release>
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </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>
 
@@ -35,12 +36,33 @@
       <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>
+            <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-shade-plugin</artifactId>

src/main/java/lambdasinaction/chap11/Util.java

@@ -25,7 +25,7 @@ public static void delay() {
 
     public static double format(double number) {
         synchronized (formatter) {
-            return new Double(formatter.format(number));
+            return Double.parseDouble(formatter.format(number));
         }
     }