code: public T mkfile() throws MkfileException {
          try {
              if (exists()) {
                  throw new MkfileException(this);
              }
              return writeBytes();
          } catch (IOException e) {
              throw new MkfileException(this, e);
          }
      }
docs: Fails if the file already exists. Features define whether this operation is atomic.
  This default implementation is not atomic.
  @return this