prestonbane/src/engine/util/BoxTracker.java

package engine.util;

import engine.objects.PlayerCharacter;

import java.util.ArrayList;
import java.util.HashMap;

public class BoxTracker {
    private static final HashMap<String, ArrayList<PlayerCharacter>> players_by_machine = new HashMap<>();

    public static void addPlayer(String machineId, PlayerCharacter player) {
        synchronized (players_by_machine) {
            ArrayList<PlayerCharacter> players = players_by_machine.get(machineId);
            if (players != null) {
                player.isBoxed = true;
                players.add(player);
            } else {
                players = new ArrayList<>();
                players.add(player);
                players_by_machine.put(machineId, players);
            }
        }
    }

    public static ArrayList<PlayerCharacter> getPlayers(String machineId) {
        synchronized (players_by_machine) {
            return new ArrayList<>(players_by_machine.getOrDefault(machineId, new ArrayList<>()));
        }
    }

    public static void removePlayer(String machineId, PlayerCharacter player) {
        synchronized (players_by_machine) {
            ArrayList<PlayerCharacter> players = players_by_machine.get(machineId);
            if (players != null) {
                players.remove(player);
                if (players.isEmpty()) {
                    players_by_machine.remove(machineId);
                }
            }
        }
    }

}