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Hello all,

I believe to have found a bug in the implementation for the iterator of
sim.util.Bag (current version in the CVS)

The problem is located in the method remove() lines 454-461

> public void remove()
> {
>     if (!canRemove) throw new IllegalStateException("remove() before next(), or remove() called twice");
>     // more consistent with the following line than 'obj > bag.numObjs' would be...
>     if (obj - 1 >=  bag.numObjs) throw new NoSuchElementException("No More Elements");
>     bag.removeNondestructively(obj-1);
>     canRemove = false;
> }

The remove() method in an iterator is defined as such that it will
remove the element that was returned by the last next()-operation.

As you can see in the code the field obj (an integer) points to the next
element that can be accessed through the iterator. So to remove the
element the removeNondestructively method is called correctly with
'obj - 1' as argument.

However, obj itself should also decremented with one.  If not, you will
skip an element for each remove operation.

For example, the following code will not function correctly:

Bag bag = new Bag();
bag.add(obj1);
bag.add(obj2)

Iterator it = bag.iterator();
while (it.hasNext()) {
	Object o = bag.next();
	it.remove();
}

You will notice that the bag is not empty at after executing this while,
although it should be.

Fixing the problem can be done by decrementing the obj-field with one in
the remove() method.


Kind Regards,
Bruno

-- 
Bruno Van Den Bossche
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http://www.ibcn.intec.UGent.be