code: public File getFile(String relativePath) throws IOException {
          if (!open.get()) {
              throw VFSMessages.MESSAGES.tempDirectoryClosed();
          }
          return new File(root, relativePath);
      }
docs: Get the {@code File} for a relative path.  The returned file is only valid as long as the tempdir exists.
  
  @param relativePath the relative path
  @return the corresponding file
  @throws IOException if the directory was closed at the time of this invocation