Update Progress:

public void updateProgress(MapleMap next, MapleMap from) {
        if (MapleRace.getMinutesUntilBegin() < 0) { // if they try to start early, wat
            if (next.getId() != map.getLeft()) //at this point, this is basically saying if it isnt the first map of the race
                racer.getCharacter().changeMap(from);
            return;
        }
        //a check if they reach the end of a list
        synchronized(this) { //order is crucial here, multi-threaded "photo finish" moment.
            if (next.getId() == racing_track.get((stage - 1)).get(racing_track.get((stage - 1)).size()).getLeft()) {
                if (MapleRace.STAGES_USE > stage) { //if they have more to go
                    ++stage;
                    MapleRace.announce("Racer #" + racer.getRacingId() + " has moved on to stage " + stage + " of the Great Maple Race!");
                    racer.getCharacter().changeMap(ChannelServer.getInstance(1).getMapFactory().getMap(racing_track.get((stage - 1)).get(0).getLeft()));
                } else {
                    MapleRace.announce("Racer #" + racer.getRacingId() + " has won the Great Maple Race!!! Please give him/her a huge congratulations!");
                    racer.award();
                    MapleRace.end();
                }
            }
        }

        Pair<Integer, Integer> update = new Pair<>(next.getId(), (point + 1));
        if (racing_track.get((stage - 1)).contains(update)) { //checks for valid global coordinate
            ++point;
            this.map = update;
            MapleRace.announce("Racer #" + racer.getRacingId() + " has progressed to " + next.getMapName() + " (point " + point + ")");

        } else {
            client.MapleCharacter c = racer.getCharacter();

            c.dropMessage(6, "You're going the wrong way!!! Follow the map! Head east!");
            int sendBack = racing_track.get((stage - 1)).contains(new Pair<>(from.getId(), point)) ? map.getLeft() : racing_track.get(0).get(0).getLeft();

            this.map = new Pair<>(sendBack, 1);
            c.changeMap(ChannelServer.getInstance(1).getMapFactory().getMap(sendBack)); // previous map or beginning
        }
    }

________________


Change map:

private void changeMapInternal(final MapleMap to, final Point pos, byte[] warpPacket, final MaplePortal pto) {
        if (to == null || MapleRace.getMinutesUntilBegin() < 0 && MapleRace.getMinutesUntilBegin() > -2 && getRacerIdentity() != null) {
            return;
        }
        final int nowmapid = map.getId();
        if (eventInstance != null) {
            eventInstance.changedMap(this, to.getId());
        }
        final boolean pyramid = pyramidSubway != null;
        if (map.getId() == nowmapid) {
            client.getSession().write(warpPacket);
            final boolean shouldChange = !isClone() && client.getChannelServer().getPlayerStorage().getCharacterById(getId()) != null;
            final boolean shouldState = map.getId() == to.getId();
            if (shouldChange && shouldState) {
                to.setCheckStates(false);
            }
            map.removePlayer(this);
            if (shouldChange) {
                map = to;
                setPosition(pos);
                to.addPlayer(this);
                stats.relocHeal(this);
                if (shouldState) {
                    to.setCheckStates(true);
                }
            }
        }
        if (this.getRacingId() > -1 && this.getRacerIdentity() != null) {
            getRacerIdentity().getProgress().updateProgress(to, map);
        }
        if (pyramid && pyramidSubway != null) { //checks if they had pyramid before AND after changing
            pyramidSubway.onChangeMap(this, to.getId());
        }
    }