@Override
	public void step() {
		if (allDone()) {
			StringBuilder sb = new StringBuilder();
			sb.append("No more task. Elevators' status: (");
			for (Integer elvId : elevators.keySet()) {
				IElevator elv = elevators.get(elvId);
				sb.append("Elevator-" + elv.getElevatorId() + "=>"
						+ elv.getCurrentFloor() + ", ");
			}
			sb.append(")");

			System.out.println(sb.toString());
		} else {
			for (Integer elvId : elevators.keySet()) {
				IElevator elv = elevators.get(elvId);
				elv.update();
			}
		}
	}