Question

With the snippet below I am, attempting to process a spreadsheet, with the twist of needing to exclude ad hoc columns. I know the crude way I am doing it, put the exceptions in an ArrayList and process the list on each and ever increment over the current row columns is perverse, but you know just get it done.

However I am getting the titled error, which I believe should never happen. I am just looping through the ArrayList and comparing, not modifying anything. Where is the error? Is there a better way to handle the exceptions list?

ArrayList noProcess = new ArrayList();
Iterator itr00 = noProcess.iterator();
Iterator itr01 = noProcess.iterator();
noProcess.add(new Integer("5"));
noProcess.add(new Integer("18"));
....
 boolean include=true;
  for(int i=0;i<archive.length;i++){
    for (int j = 0; j < archive[i].length; j++) {
      while (itr00.hasNext()) {
        if (j == ( (Integer) itr00.next()).intValue())
          include = false;
      }
      if (include) {...

Answer 1

You can’t alter the contents of an Iterable once you create an iterator on it (other than via the iterator), otherwise you’ll get a ConcurrentModificationException as soon as you move the iterator – you create an iterator, then do noProcess.add(new Integer("5"));, then later advance the iterator.

Also, you create two iterators – you shouldn’t do that either – it’s crazy.