ReactiveX

// says hello
public class Main {
    public static void main(String[] args) {
        System.out.println("hello, world");
    }
}

def print_hi(name)
  puts "Hi, #{name}"
end
print_hi('Tom')
#=> prints 'Hi, Tom' to STDOUT.

object HelloWorld {
  def main(args: Array[String]) {
    println("hello, world")
  }
}

// hello, world
int main(void)
{
    printf("hello, world\n");
    return 0;
}