CombinedQueue get not threadsafe

public class CombinedQueue<T> implements Queue<T> // WIP
{
    final Collection<Queue<T>> memberQueues;
    final Lambda<T, Comparable> keyGetter;

    public T get(boolean remove)
    {
        // Work on a copy of memberQueues
        List<Queue<T>> memberQueuesCopy;

        synchronized(memberQueues)
        { memberQueuesCopy = new Arraylist<Queue<T>>(memberQueues); }

        // local variables
        Queue<T> nextQueue;
        T nextValue;
        Comparable nextValueComparable;

        // Run through all member queues, filling those variables with the variables
        // corresponding to the queue with the lowest next comparable derived via keyGetter.
        for(Queue<T> i : memberQueuesCopy)
        {
            if(i != null && !i.isEmpty())
            {
                T iValue = i.peek();

                if(iValue == null && nextValue == null)
                {
                    nextQueue = i;
                    nextValue = null;
                    nextValueComparable = null;
                }
                else if(iValue != null)
                {
                    Comparable iValueComparable = keyGetter.getMember(iValue);

                    if((iValueComparable == null && nextQueue == null) ||
                        (iValueComparable != null && iValueComparable.compareTo(nextValueComparable) < 0))
                    {
                        nextQueue = i;
                        nextValue = iValue;
                        nextValueComparable = iValueComparable;
                    }
                }
            }
        }

        if(Queue == null)
            throw new NoSuchElementException();

        if(remove)
            nextQueue.remove();

        return nextValue;
    }
}