private int findLastAssignedIndex(final Object[] items) {
            for (int i = items.length - 1; i >= 0; i--) {
                if (items[i] != null) {
                    return i;
                }
            }
            return -1;
        }
Returns an iterator over the elements of this, starting at the last
element and working backwards. This iterator does not support remove.
vespajlib/src/main/java/com/yahoo/concurrent/ThreadRobustList.java