在Actionscript 3中实现单例模式类的最佳方法是什么？

public class Singleton {
    private static var _instance:Singleton;

    public static function getInstance():Singleton {
        if (_instance == null) {
            _instance = new Singleton();
        }
        return _instance;
    }

    public function Singleton() {
        if (_instance != null) {
            throw new Error("Singleton instance already created.");
        }
    }

    public function doSomething():void {
        // 在这里实现你的业务逻辑
    }
}

var singleton:Singleton = Singleton.getInstance();
singleton.doSomething();