🧑‍💻 Singleton Design Pattern

The Singleton Pattern is a creational design pattern that ensures:

A class has only one instance.
That instance is globally accessible.

Escape Room Example Scenario

In your game, some objects should only exist once:

GameManager → controls the game flow, keeps score, manages time.
Settings → stores configuration (sound, difficulty, etc.).
Logger → records player actions.

Singleton Class (GameManager)

public class GameManager {
    // Step 1: private static instance
    private static GameManager instance;

    // Step 2: private constructor (prevents outside instantiation)
    private GameManager() {
        System.out.println("GameManager initialized.");
    }

    // Step 3: public method to get the instance
    public static GameManager getInstance() {
        if (instance == null) {
            instance = new GameManager();
        }
        return instance;
    }

    // Example functionality
    private int score = 0;

    public void addScore(int points) {
        score += points;
        System.out.println("Score updated: " + score);
    }

    public int getScore() {
        return score;
    }
}

Using the Singleton in the Game

public class EscapeRoomGame {
    public static void main(String[] args) {
        // Get the one and only instance
        GameManager gm1 = GameManager.getInstance();
        gm1.addScore(10);

        GameManager gm2 = GameManager.getInstance();
        gm2.addScore(20);

        // Both gm1 and gm2 are the SAME instance
        System.out.println("Final Score: " + gm1.getScore());
    }
}

Sample Output

GameManager initialized.
Score updated: 10
Score updated: 30
Final Score: 30

Notice:

The GameManager was initialized only once.
Both references (gm1, gm2) pointed to the same instance.

Thread-Safe Singleton (Optional Upgrade)

In a multi-threaded game, we need to ensure only one instance is created even if multiple threads request it simultaneously.

public class GameManager {
    private static volatile GameManager instance;

    private GameManager() {}

    public static GameManager getInstance() {
        if (instance == null) {
            synchronized (GameManager.class) {
                if (instance == null) {
                    instance = new GameManager();
                }
            }
        }
        return instance;
    }
}

This is the double-checked locking approach.

Why is Singleton Useful in a Game?

Global access point (all parts of the game can reference one manager).
Consistency (one score, one timer, one config).
Memory efficiency (avoids creating unnecessary duplicate objects).

Next Step Ideas 💡

Use Singleton for TimerManager (only one countdown timer per game).
Use Singleton for SoundManager (global control of sound effects).
Combine with Observer Pattern → GameManager notifies observers (UI, players) about game events.

✅ Key Takeaway:
The Singleton Pattern ensures there’s exactly one instance of a class, making it perfect for global managers like GameManager, Logger, or Settings in your escape room.