java 處理超長的字串顯示為。。。的處理

public static string stringformat(string str,int n)
    {
    ///
    ///格式化字串
長度，超出部分顯示省略符號,區分漢字跟字母。漢字2個位元組，字母數字一個位元組
    ///
     string temp=string.Empty;
         if(System.Text.Encoding.Default.GetByteCount(str)<=n)//如果長度比需要的長度n小,返回原字串
        {
              return str;
         }
            else
               {
                  int t=0;
                  char[] q=str.ToCharArray();
                  for(int i=0;i<q.Length&&t<n;i++)
                     {
                      if((int)q[i]>=0x4E00 && (int)q[i]<=0x9FA5)//是否漢字
                           {
                                 temp+=q[i];
                                 t+=2;
                            }
                            else
                              {
                                temp+=q[i];
                                t++;
                               }
                            }
                        return (temp+"...");
                      }
                }