Key substitute for AS3

public class Key
    {
        import flash.display.Stage;
        import flash.events.Event;
        import flash.events.KeyboardEvent;

        private static var initialized:Boolean = false;
        private static var keysDown:Object = new Object();

        //player controlls
        public static const USE:uint = 88;
        public static const SHOOT:uint = 32;
        public static const SHOOT2:uint = 40;
        public static const ACCELERATE:uint = 38; //TODO: set all these with XML!
        public static const LEFT:uint = 37;
        public static const RIGHT:uint = 39;


        /**
         * Initializes the key class creating assigning event
         * handlers to capture necessary key events from the stage
         */
        public static function initialize(stage:Stage) {
            if (!initialized) {
                // assign listeners for key presses and deactivation of the player
                stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
                stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);
                stage.addEventListener(Event.DEACTIVATE, clearKeys);
                // mark initialization as true so redundant
                // calls do not reassign the event handlers
                initialized = true;
            }
        }

        /**
         * Returns true or false if the key represented by the
         * keyCode passed is being pressed
         */
        public static function isDown(keyCode:uint):Boolean {
            if (!initialized) {
                // throw an error if isDown is used
                // prior to Key class initialization
                throw new Error("Key class has not been initialized.");
            }
            return Boolean(keyCode in keysDown);
        }

        /**
         * Event handler for capturing keys being pressed
         */
        private static function keyPressed(event:KeyboardEvent):void {
            // create a property in keysDown with the name of the keyCode
            //trace(event.keyCode);
            keysDown[event.keyCode] = true;
        }

        /**
         * Event handler for capturing keys being released
         */
        private static function keyReleased(event:KeyboardEvent):void {
            if (event.keyCode in keysDown) {
                // delete the property in keysDown if it exists
                delete keysDown[event.keyCode];
            }
        }

        /**
         * Event handler for Flash Player deactivation
         */
        private static function clearKeys(event:Event):void {
            // clear all keys in keysDown since the player cannot
            // detect keys being pressed or released when not focused
            keysDown = new Object();
        }
    }