Java 27 and 26: runnable demos and captured output for every JEP, plus version lanes

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3

lanes/upgrade/build.gradle.kts

@@ -0,0 +1,15 @@
+// Gradle (build.gradle.kts): ask for a Java 25 toolchain
+plugins {
+    java
+    application
+}
+
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(25))
+    }
+}
+
+application {
+    mainClass.set("demo.App")
+}

lanes/upgrade/pom.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.ankurm.demos</groupId>
+  <artifactId>upgrade-demo</artifactId>
+  <version>1.0</version>
+
+  <properties>
+    <!-- Maven (pom.xml): keep all three in step. source and target set the language level and the class-file version; release also limits the API you may call -->
+    <maven.compiler.source>25</maven.compiler.source>
+    <maven.compiler.target>25</maven.compiler.target>
+    <maven.compiler.release>25</maven.compiler.release>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
+</project>

lanes/upgrade/settings.gradle.kts

@@ -0,0 +1 @@
+rootProject.name = "upgrade-demo"

lanes/upgrade/src/main/java/demo/App.java

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+package demo;
+
+/**
+ * The smallest class that proves a build targets Java 25: it prints the Java version of the JVM it runs on.
+ * Explained in docs/15-build-files.md. The build files next to it (pom.xml, build.gradle.kts) are the ones
+ * quoted in the "Step 1" section of the upgrade guide.
+ */
+public class App {
+    public static void main(String[] args) {
+        System.out.println("running on Java " + Runtime.version().feature());
+    }
+}