ConcurrentModificationException while iterating through ArrayList

Question

synchronized(queueClientList){
    Iterator<Client> iterator = queueClientList.iterator();
    while (iterator.hasNext()){
        Client client = new Client();
        client = iterator.next();
        try {
            Thread.sleep(client.serviceTime);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
        System.out.println(client.ID+ " it`s out");
        queueClientList.remove(client);
    }
}

This code should iterate through queueClientList and sleep the Thread for client.serviceTime milliseconds. After waking up, it should delete the current client from the queueClientList.

It gives me the ConcurrentModificationException at client = iterator.next() line

The declaration of queueClientList is:

public List<Client> queueClientList = Collections.synchronizedList(new ArrayList<Client>());

Why does it throw that error if this whole method is synchronized?

As an aside, this has nothing to do with threading/thread safety, as the concurrent modification all happens within the same thread. — rmlan, Apr 01 '17 at 13:37

score 0 · Accepted Answer · answered Apr 01 '17 at 13:43

0

Problem solved. The problem was, that I was trying to remove from my list , while iterating thorugh it, which is impossible.

answered Apr 01 '17 at 13:43

biafas

127
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ConcurrentModificationException while iterating through ArrayList

1 Answers1