Do I need a Singleton pattern for this case

Question

Hello,
I'm writing a game in Java and I have a very simple score manager class which just tracks the points the player so far has. I need to access this class in different pars of my app (gui, game core ...) so I created a singleton class which looks like this
public class ScoreManager {
        private static ScoreManager instance = new ScoreManager();
        private int score = 0;
     private int highScore = 0;
     public static ScoreManager getInstance() {
          return instance;
     public int getScore() {
          return score;
     public int getHighScore() {
          return highScore;
     public void addScore(int scoreToAdd){
          score += scoreToAdd;
          if(score > highScore) {
               highScore = score;
}so far so good ..
I would like to read the "highScore" from a file when the game starts and write it back when the game ends. I added those two methods:
     public void init(File highScoreFile) {
          highScore = readFromFile(highScoreFile);
                score = 0;               
     public void dispose(File highScoreFile) {
               writeToFile(highScoreFile);
     }So basically I call the init() method when the game stars and the dispose() when the game ends.
It works but what I don't like is that the init() and dispose() methods are exposed and someone could call them in a wrong place.
What would be a better way to do this ?
Thanks for your help,
Jesse

Answer 1

safarmer wrote:
You could keep track of the state (initialised, destroyed etc) in the manager and only perform the action if it is an expected state.
private enum State { NOT_INITIALISED, INITIALISED, DESTROYED};
private State currentState = State.NOT_INITIALISED;
// i will leave the rest up to your imagination :) this looks good, thanks
anotherAikman wrote:
>
It works but what I don't like is that the init() and dispose() methods are exposed and someone could call them in a wrong place. And who would that be? You´re the only one using the code, aren´t you?
If not, you could still include in the documentation where to call those methods.
no I'm not the only one working on this. Documentation can be useful but does not prevent calling wrong methods.
YoungWinston wrote:
I don't see any constructor. Usually, a singleton class should have a private one, even if it has no parameters. If you don't have any, Java will create a public no-parameter one as default.ok I forgot the private constructor.
It works but what I don't like is that the init() and dispose() methods are exposed and someone could call them in a wrong place. Then my advice would be not to make them public. After all, your code is the only one calling these methods - yes?yes only the code of the app calls it.
If you are convinced that your game requires one and only one score manager, then a singleton is probably the best way to go.
I'm a little worried about the init() and dispose() methods though, because these suggest state changes, which is unusual for the singleton pattern. You may want to think about synchronizing them.
An alternative might be to use properties to get and store your scores.ok for the synchronization. What would using the properties ? It would be just another type of storage backend and I'd still need to read/write it.
Thanks for your help,
J