Comparison of implicit and explicit type conversions of String

/**
 * Copyright Fumio ( http://wonderfl.net/user/Fumio )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/9LQ4
 */

package {
	import flash.display.Sprite;
	import flash.utils.getTimer;
	import flash.text.TextField;
	import flash.text.TextFieldAutoSize;
	import flash.text.TextFormat;
	import flashx.textLayout.formats.TextAlign;
	[SWF(width = "240",height = "180")]
	public class Implicit_vs_ExplicitTypeConversion2 extends Sprite {
		private const AMOUNT:uint = 100000000;
		private var started:uint;
		private var my_txt:TextField = new TextField();
		private var label_txt:TextField = new TextField();
		private var my_fmt:TextFormat = new TextFormat();
		private var test_array:Array = [];
		private var testVector:Vector.<uint >  = new Vector.<uint > (AMOUNT);
		public function Implicit_vs_ExplicitTypeConversion2() {
			// Creating a TextField for display
			createTextField();
			// Starting test
			set_literal();
			use_plus();
			use_coversion_w_plus();
			use_String();
			// use_toString();
		}
		private function set_literal():void {
			started = getTimer();
			for (var i:int = 0; i < AMOUNT; i++) {
				var _str:String = "10";
			}
			xTrace(getTimer() - started);
		}
		private function use_plus():void {
			started = getTimer();
			for (var i:int = 0; i < AMOUNT; i++) {
				var _str:String = "1" + "0";
			}
			xTrace(getTimer() - started);
		}
		private function use_coversion_w_plus():void {
			started = getTimer();
			for (var i:int = 0; i < AMOUNT; i++) {
				var _str:String = "" + 10;
			}
			xTrace(getTimer() - started);
		}
		private function use_String():void {
			started = getTimer();
			for (var i:int = 0; i < AMOUNT; i++) {
				var _str:String = String(10);
			}
			xTrace(getTimer() - started);
		}
		private function use_toString():void {
			started = getTimer();
			for (var i:int = 0; i < AMOUNT; i++) {
				var _str:String = (10).toString();
			}
			xTrace(getTimer() - started);
		}
		private function createTextField():void {
			addChild(my_txt);
			addChild(label_txt);
			my_txt.x +=  70;
			my_txt.autoSize = TextFieldAutoSize.RIGHT;
			my_fmt.align = TextAlign.RIGHT;
			my_txt.defaultTextFormat = my_fmt;
			label_txt.autoSize = TextFieldAutoSize.LEFT;
			label_txt.text = "String literal:\npulus + operator:\nimplicit conversion with +:\nString() function:"  // \ntoString() metohd:";
		}
		private function xTrace(n:int):void {
			my_txt.appendText(String(n) + "\n");
		}
	}
}