[jdom-interest] Bug in Element.getChildren().listIterator(pos)

[Bradley S. Huffman]

I think this is the same bug found by Vadim Strizhevsky at the end of July.
There is a patch at

http://lists.denveronline.net/lists/jdom-interest/2003-July/013289.html

but it hasn't been fully tested either.

Looking at your patch, I'm not sure it is correct. If start = 0 and the 
backing list contains only a single Text node then initializeCursor
would return 0 cause a call to hasNext to be true, but index 0 in the backing
list is a Text node not a Element.

Brad

Paul Cantrell writes:

> Working on Macker (at http://innig.net/macker if you're curious), I 
> found a bug in the listIterator(int) method of the list returned by 
> Element.getChildren().
> 
> The following code demonstrates the bug -- it incorrectly generates a 
> ClassCastException if element contains text content after its last 
> child element:
> 
>          List children = element.getChildren();
>          for(ListIterator childIter = 
> children.listIterator(children.size()); childIter.hasPrevious(); )
>              {
>              Element subElem = (Element) childIter.previous();
> 	.......
>              }
> 
> The exception occurs because the call to childIter.previous() 
> erroneously returns a Text object the first time it is called.
> 
> The problem appears to be in the last line 
> ContentList.java.initializeCursor(int start), which is 
> ContentList.java:1277 in the nightly I just picked up.  The final 
> return incorrectly presumes that the last element in the list matches 
> the filter.  The method *should* go something like this:
> 
>          private int initializeCursor(int start) {
>              if (start < 0) {
>                  throw new IndexOutOfBoundsException("Index: " + start);
>              }
> 
>              int count = 0;
>              int lastMatchPos = -1;  // <---------
>              for (int i = 0; i < ContentList.this.size(); i++) {
>                  Object obj = ContentList.this.get(i);
>                  if (filter.matches(obj)) {
>                      lastMatchPos = i;  // <----------
>                      if (start == count) {
>                          return i;
>                      }
>                      count++;
>                  }
>              }
> 
>              if (start > count) {
>                  throw new IndexOutOfBoundsException("Index: " + start +
>                                                      " Size: " + count);
>              }
> 
>              return lastMatchPos + 1; // <---------
>          }
> 
> WARNING: I haven't tested this patch -- I just typed it straight into 
> the email.  (Sorry!)  I hope it's not too far off the mark.
> 
> Cheers,
> 
> Paul
> 
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