code: public void save(ProcessingEnvironment env) throws IOException
      {
          Filer filer = env.getFiler();
          //JavaFileObject sourceFile = filer.createClassFile(getQualifiedName(), superClass);
          FileObject sourceFile = filer.createResource(
                  StandardLocation.CLASS_OUTPUT, 
                  El.getPackageOf(this).getQualifiedName(), 
                  getSimpleName()+".class"
                  );
          BufferedOutputStream bos = new BufferedOutputStream(sourceFile.openOutputStream());
          DataOutputStream dos = new DataOutputStream(bos);
          write(dos);
          dos.close();
          System.err.println("wrote "+sourceFile.getName());
      }
docs: Saves subclass as class file
  @param env
  @throws IOException