A MessageQueue is one of the core components in forming an Akka Mailbox.
The MessageQueue is where the normal messages that are sent to Actors will be enqueued (and subsequently dequeued)
It needs to at least support N producers and 1 consumer thread-safely.
Called when the mailbox this queue belongs to is disposed of. Normally it
is expected to transfer all remaining messages into the dead letter queue
which is passed in. The owner of this MessageQueue is passed in if
available (e.g. for creating DeadLetters()), “/deadletters” otherwise.
Try to enqueue the message to this queue, or throw an exception.
receiver - (undocumented)
handle - (undocumented)
Indicates whether this queue is non-empty.
Should return the current number of messages held in this queue; may
always return 0 if no other value is available efficiently. Do not use
this for testing for presence of messages, use hasMessages instead.