code: public DirectoryEntry requireSymbolicLink(Path pathForException)
        throws NoSuchFileException, NotLinkException {
      requireExists(pathForException);
      if (!file().isSymbolicLink()) {
        throw new NotLinkException(pathForException.toString());
      }
      return this;
    }
docs: Checks that this entry exists and links to a symbolic link, throwing an exception if not.
  
  @return this
  @throws NoSuchFileException if this entry does not exist
  @throws NotLinkException if this entry does not link to a symbolic link