格式化日期类SimpleDateFormat

/**
   * Title: 格式化日期类
   * Description:
   * Company:
   * Copyright
   * @author wei386
   * @version 1.0
   */
class SimpleDateFormat
{
   private var timetype :String;
   private var date:Date;
   private var year:String;
   private var month:String;
   private var day:String;
   
   function SimpleDateFormat(type:String)
   {
      this.timetype=type;
   }
   /**
    * 得到包含字符串firststring的开始位置
    * @param String firststring
    * @return Number
    */
   private function firstString(firststring:String):Number
   {
             var starts:Number = timetype.indexOf(firststring);
      return starts;
   }
   /**
    * 得到包含字符串firststring的结束位置
    * @param String firststring
    * @return Number
    */
   private function lastString(laststring:String):Number
   {
      var ends:Number = timetype.lastIndexOf(laststring);
      return ends;
   }
   /**
    * 查找是否年
    * @param
    * @return Boolean
    */
   private function findYear():Boolean
   {
      var starts = this.firstString("y");
      var ends = this.lastString("y");
      var yeartype = ends-starts;
      if(yeartype==3)
      {
         this.year=""+this.date.getFullYear();
         return true;
      }else if(yeartype==1)
      {
         var shortyear :String= ""+this.date.getFullYear();
         this.year = shortyear.substring(2,4);
         return true
      }else if(starts==-1||ends==-1)
      {
         return false;
      }
      else{
      trace("年份格式不正确");
      return false;
      }
   }
   /**
    * 查找是否月
    * @param
    * @return Boolean
    */
   private function findMonth():Boolean
   {
      var starts = this.firstString("M");
      var ends = this.lastString("M");
      var monthtype = ends-starts;
      if(starts==-1)
      {
         return false;
      }
      else if(monthtype==1)
      {
         var newmonth = this.date.getMonth()+1;
         if(newmonth<10)
         {
            this.month="0"+newmonth;
         }else{
         this.month=""+newmonth;
         }
         return true
      }
      else{
         trace("月份格式不正确");
         return false;
         }
   }
   /**
    * 查找是否日
    * @param
    * @return Boolean
    */   
   private function findDay():Boolean
   {
      var starts = this.firstString("d");
      var ends = this.lastString("d");
      var monthtype = ends-starts;
      if(starts==-1)
      {
         return false;
      }
      else if(monthtype==1)
      {
                var newday=this.date.getDate();
         if(newday<10)
         {
             this.day="0"+newday;
         }else
         {
            this.day=""+newday;
         }
         return true
      }
      else{
         trace("日子格式不正确");
         return false;
         }
   }
   /**
    * 按照构造函数时的格式，格式化传进来的date对象
    * @param Date pdate
    * @return String
    */
   public function format(pdate:Date):String
   {
      this.date=pdate;
      var stringlength = timetype.length;
      var ystarts = this.firstString("y");
      var yends = this.lastString("y");
      var mstarts = this.firstString("M");
      var mends = this.lastString("M");
      var dstarts = this.firstString("d");
      var dends = this.lastString("d");
      var isyear=this.findYear();
      var ismonth=this.findMonth();
      var isday=this.findDay();
      if(isyear)
      {
         this.showresult(ystarts,yends,this.year);
      }
      if(ismonth)
      {
         this.showresult(mstarts,mends,this.month);
      }
      if(isday)
      {
         this.showresult(dstarts,dends,this.day);
      }
      
      return timetype;
   }
   /**
    * 在相应的位置替换成日期结果
    * @param Number nstart,Number nend,String ndate
    * @return void
    */
   private function showresult(nstart:Number,nend:Number,ndate:String):Void
   {
      this.timetype = this.timetype.substring(0,nstart)+ndate+this.timetype.substring(nend+1,this.timetype.length);
   }
}