code: public Runnable asRunnable() {
          return new Runnable() {
              @Override
              public void run() {
                  try {
                      callable.call();
                  } catch (Exception e) {
                      throw new RuntimeException(e);
                  }
              }
          };
      }
docs: Wraps the enhanced callable as a runnable.
  @return the wrapped runnable.