JEP 445: Flexible Main Methods and Anonymous Main Classes (Preview)(openjdk.org)

    interface Program {
        static void main(String...args);
    }

    interface Foo extends Comparable<This> {

        static This(A argA, B argB);

        static This difference(This v0, This v1);

        static int compare(This v0, This v1);

        default int compareTo(This other){
            return compare(v0, v1);
        }

    }

    /*
        I want to return an instance of my class' own type (defined in a subclass an so unknown),
        so I pass every implementation itself as its own generic parameter.
    */

    interface Why<W extends Why<W>> implements Comparable<W>{
        W someManipulation();  
    }

    class Foo implements Why<Foo> {
        @Override
        Foo someManipulation(){
            ....
        }
    }

    #!/usr/bin/env java

    #!/usr/bin/env java-12.0.*

  #include <stdio.h>
  int main() {
    printf("Hello world\n");
    return 0;
  }

    int x;

    public Foo(int x) {
        this.x = x;
    }
    
    void main() {
         System.out.println(x);
    }
}

  println("Hello");