public DimensionalNodeIterator(DimensionalNode node){
  if (node == null) {
    throw new NullPointerException("DimensionalNodeIterator received null starting point");
  }
  stack.add(new Moment(node,left));
  advance();
}

public DimensionalNodeIterator ( DimensionalNode node ) { if ( node == null ) { throw new NullPointerException ( "DimensionalNodeIterator received null starting point" ) ; } stack . add ( new Moment ( node , left ) ) ; advance ( ) ; }
start the traversal at the given node .
