I was curious as well, so I took it for a spin[0]. In short, no. A static initializer still needs to be wrapped in a class that contains a main method.

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

[0]: https://repl.it/GDZG/1

A bit of both. Code still belongs in a class, not pictured here. `static` blocks are executed when the class is loaded and are usually used to fill `static final` members. In a toy example like this it's shorter than writing the `main()` incantation.