private void writeObject(java.io.ObjectOutputStream oos) throws java.io.IOException {
synchronized (principals) {
    oos.defaultWriteObject();
  }
}

private void writeObject ( java . io . ObjectOutputStream oos ) throws java . io . IOException { synchronized ( principals ) { oos . defaultWriteObject ( ) ; } }
writes this object out to a stream ( i . e . , serializes it ) .
