code: public final void expurgeQueuedReferences() {
  		Reference<? extends E> obj;
  		while ((obj = this.queue.poll()) != null) {
  			obj.clear();
  			if (this.referenceType.isInstance(obj)) {
  				this.theSet.remove(this.referenceType.cast(obj));
  			}
  		}
  	}
docs: Clean the references that was marked as released inside
  the queue.