code: public void save(File file, String comment, boolean saveDefaults) throws IOException
      {
          save(file, comment, saveDefaults, null);
      }
docs: Save the current state of the properties within this instance to the
  given file.
  
  @param file
  the file to which the current properties and their values will
  be written
  @param comment
  an optional comment to put at the top of the file (
  <code>null</code> means no comment)
  @param saveDefaults
  if <code>true</code>, values that match the default will be
  written to the file; otherwise values matching the default
  will be skipped
  @throws IOException
  if there is an error writing the given file