public Expression nextValid(final Iterator<Expression> it){
  while (it.hasNext()) {
    final Expression expr=it.next();
    if (!isIgnorable(expr)) {
      return expr;
    }
  }
  return null;
}

public Expression nextValid ( final Iterator < Expression > it ) { while ( it . hasNext ( ) ) { final Expression expr = it . next ( ) ; if ( ! isIgnorable ( expr ) ) { return expr ; } } return null ; }
advance the iterator and return the next non - ignorable expression .
