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

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());
    }
}