How Java 21 Simplifies Hello World with Unnamed Classes and New Launch Protocol

Java 21 adds two language core features: unnamed classes and a new launch protocol (JEP 445) that let programs run with far less boilerplate.

Traditional Hello World in Java requires a public class, a static main method with a String[] argument, and explicit public modifiers:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

The article points out that these elements are unnecessary for a simple example and can confuse beginners.

Using JEP 445, the same program can be written as:

class HelloWorld {
    void main() {
        System.out.println("Hello, World!");
    }
}

Furthermore, Java 21 introduces unnamed classes, allowing the program to be reduced to a single method without a class declaration:

void main() {
    System.out.println("Hello, World!");
}

These changes make Java’s entry‑level code as concise as that of Python or Go, potentially lowering the learning curve for newcomers.