public Object dequeue() {
        if (used == 0) {
            return null;
        }
        Object obj = buf[readPos];
        buf[readPos++] = null; // enable GC of dequeued object
        if (readPos == buf.length) {
            readPos = 0;
        }
        used--;
        return obj;
    }
Dequeue the next object from this queue.

@return the next object from the queue or 'null' if the queue
is empty
jrt/src/com/yahoo/jrt/Queue.java