Singleton.java

public class Jackpot {
    private static Jackpot jackpot;
    private ArrayList<Bet> betHistory;

    private Jackpot() {
        this.betHistory = new ArrayList<Bet>();
    }

    public boolean addBet(Bet bet) {
        this.betHistory.add(bet);
        return true;
    }

    public ArrayList<Bet> getBetHistory() {
        return this.betHistory;
    }

    public static Jackpot getJackpot() {
        if (jackpot == null) {
            jackpot = new Jackpot();
        }
        return jackpot;
    }

}