public void enqueue(Object anObject) {
if (head == null) {
head = tail = new QNode(anObject, null);
} else {
tail.next = new QNode(anObject, null);
tail = tail.next;
}
}
public Object dequeue() {
if (head == null) {
throw new NoSuchElementException("No more elements");
}
Object retval = head.object;
QNode oldHead = head;
head = head.next;
if (head == null) {
tail = null;
} else {
oldHead.next = null;
}
return retval;
}
/**
* Tries to cas nh as new head; if successful, unlink old head's next node to avoid garbage
* retention.
*/
void advanceHead(QNode h, QNode nh) {
if (h == head && UNSAFE.compareAndSwapObject(this, headOffset, h, nh))
h.next = h; // forget old next
}
