Java 25 Lets Developers Launch Micronaut Apps Without Boilerplate Class Declarations

Java 25 finalizes a feature called compact source files via JEP 512, allowing developers to write launchable programs without explicitly declaring a class or a public static void main method. This reduces boilerplate code significantly when bootstrapping frameworks like Micronaut, where the traditional startup class requires a full package declaration, class definition, and main method signature. With a compact source file, the entire Micronaut application entry point shrinks to just an import and a void main method calling Micronaut.run(). Because no package is declared, the Gradle build configuration also simplifies, requiring only the filename as the mainClass value. Developers must ensure the compact source file is placed directly under src/main/java rather than inside a package subdirectory, as the implicit class name is derived from the filename.