Why these java lines goes to an infinite loop

Question

I heed to do some arraylist manipulations and I've run into a problem, creating an infinite loop. Can someone explain it why, please?

p.s. don't worry about trace command, I'm creating custom java extension to smartfoxserver 2x instance.

String deckOf4Array[] = new String[] {"AD","KD","QD","JD","10D","9D","8D","7D","6D","AH","KH","QH","JH","10H","9H","8H","7H","6H","AC","AS","KS"};
List<String> deckOf4List = new ArrayList<String>(Arrays.asList(deckOf4Array));

for(int n=0; n<4; n++)
{
    int cardindex = new Random().nextInt(deckOf4List.size()-1);
    trace("cardindex: " + cardindex);
    for (ListIterator<String> iter = deckOf4List.listIterator(); iter.hasNext(); )
    {
        // Here goes infinite loop
        trace("cardindex: " + cardindex);

        if(cardindex == iter.nextIndex())
        {
            // Here goes manipulations
        }
        iter.remove();
    }
}

Answer 1

You have to edit your for loop...

for (ListIterator<String> iter = deckOf4List.listIterator(); iter.hasNext(); iter.next())

The nextIndex() method returns the upcoming index, however, it does not move the cursor in your iteration. So if you put iter.next() in your for-loop, it will actually move the cursor. In your case, you are not moving the cursor, so you keep iterating over index 0.

As for the official documentation...

next() - Returns the next element in the list and advances the cursor position.

int nextIndex() - Returns the index of the element that would be returned by a subsequent call to next().