KNY

package {
    class MySingleton {
        private static var m_instance:MySingleton;
        public function MySingleton(lock:Lock){
            // init code;
        }
        public static function instance()
        {
            if(m_instance == null){
                m_instance = new MySingleton(new Lock());
            }
            return m_instance;
        }
    }
}

class Lock{}