public void makeImmutable(){
  if (!mutable) {
    return;
  }
  mutable=false;
  if ((content != null) && (!content.isEmpty())) {
    content=Collections.unmodifiableList(content);
  }
}

public void makeImmutable ( ) { if ( ! mutable ) { return ; } mutable = false ; if ( ( content != null ) && ( ! content . isEmpty ( ) ) ) { content = Collections . unmodifiableList ( content ) ; } }
makes the object immutable
