code: protected void checkTarget(final File target) throws IOException {
          if (target == null) {
              throw new IOException("You must provide a target directory or file");
          }
          if (!target.exists()) {
              String extension = FilenameUtils.getExtension(target.getName());
              if (extension.length() == 0) {
                  throw new IOException("Target folder " + target + " not found");
              }
          }
      }
docs: make sure the target, folder or file, is valid. We consider that target
  files will have extensions. Its ok for a target file not to exist but
  target folders must exist.
  
  @param target the target folder or file
  @throws IOException if file cannot be located