public void add(HistoryReference href){
synchronized (hrefList) {
    hrefList.add(href);
    fireTableRowsInserted(hrefList.size() - 1,hrefList.size() - 1);
  }
}

public void add ( HistoryReference href ) { synchronized ( hrefList ) { hrefList . add ( href ) ; fireTableRowsInserted ( hrefList . size ( ) - 1 , hrefList . size ( ) - 1 ) ; } }
adds a href . method is synchronized internally .
