@Override
		public int compare(CentralTask o1, CentralTask o2) {
			if (o1 instanceof DownloadJobEntryTask && o2 instanceof DownloadJobEntryTask)
				return Long.compare(o1.createTime, o2.createTime);
			else if (o1 instanceof DownloadJobEntryTask || o2 instanceof DownloadJobEntryTask) {
				return o1 instanceof DownloadJobEntryTask ? -1 : 1;
			}

			if (o1 instanceof DownloadCameraIntervalTask && o2 instanceof DownloadCameraIntervalTask) {
				DownloadCameraIntervalTask d1 = (DownloadCameraIntervalTask)o1;
				DownloadCameraIntervalTask d2 = (DownloadCameraIntervalTask)o2;
				if (d1.getPriority() == d2.getPriority())
					return Long.compare(d1.createTime, d2.createTime);
				else
					return d1.getPriority() < d2.getPriority() ? 1 : -1;
			} else if (o1 instanceof DownloadCameraIntervalTask || o2 instanceof DownloadCameraIntervalTask)
				return o1 instanceof DownloadCameraIntervalTask ? -1 : 1;

			return Long.compare(o1.createTime, o2.createTime);
		}
	};