public ApnsServiceBuilder asQueued(ThreadFactory threadFactory) {
        this.isQueued = true;
        this.queueThreadFactory = threadFactory;
        return this;
    }
Constructs a new thread with a processing queue to process
notification requests.

@param threadFactory
           thread factory to use for queue processing
@return  this
src/main/java/com/notnoop/apns/ApnsServiceBuilder.java