飛び飛びに値を入れた配列の長さは？

/**
 * Copyright esukei ( http://wonderfl.net/user/esukei )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/q3qF
 */

/**
 * 先輩の質問への回答用
 * 飛び飛びに宣言したときは、それまでの配列も確保されます。
 * のでarray.lengthは5になりません。
 */
package {
    import flash.display.Sprite;
    import flash.text.TextField;
    import flash.events.MouseEvent;
    import flash.events.Event;
    import flash.geom.Point;
    [SWF(frameRate = "8")]
    public class FlashTest extends Sprite {
        
        private var textField:TextField;      
        
        public function FlashTest() {
            // write as3 code here..
            textField = new TextField();
            textField.width = stage.stageWidth;
            textField.height = stage.stageHeight;
            textField.multiline = true;
            textField.wordWrap = true;
            textField.text = 'LOGGING HERE.';
            addChild(textField);
            
            var array:Array = new Array();
            
            array[1] = 1;
            array[10] = 10;
            array[100] = 100;
            array[1000] = 1000;
            array[10000] = 10000;
            
            clearLog();
            
            addLog('配列の長さ：' + array.length.toString());
            addLog('配列の中身：');
            addLog(array.toString());
            
        }
        
        private function addLog(log:String):void
        {
            textField.appendText(log + '\n');
        }
        
        private function clearLog():void
        {
            textField.text = '';
        }
        
    }
}