public void preSaveInit(){
  persistentData.clear();
  for (int i=0; i < getNumPoints(); i++) {
    persistentData.add(getPoint(i));
  }
}

public void preSaveInit ( ) { persistentData . clear ( ) ; for ( int i = 0 ; i < getNumPoints ( ) ; i ++ ) { persistentData . add ( getPoint ( i ) ) ; } }
initializes persistent data . initializes dataset from persistent data .
