public void addListener(final ISPARQLUpdateListener l){
  if (isReadOnly())   throw new UnsupportedOperationException();
  if (l == null)   throw new IllegalArgumentException();
  listeners.add(l);
}

public void addListener ( final ISPARQLUpdateListener l ) { if ( isReadOnly ( ) ) throw new UnsupportedOperationException ( ) ; if ( l == null ) throw new IllegalArgumentException ( ) ; listeners . add ( l ) ; }
add a sparql udpate listener .
