/**
* 计算时间差
* @param begin
* @param end
* @return 返回格式,"hh:mm:ss"
*/
public String getTimeDifference(Date begin,Date end) {
  long between=(end.getTime()-begin.getTime())/1000;
  //除以1000是为了转换成秒
  long hour=between%(24*3600)/3600;
  long minute=between%3600/60;
  long second=between%60;
  StringBuffer time=new StringBuffer();
  if(hour!=0){
   time.append(hour+":");
  }
  if(time.length()!=0){
   time.append(String.format("d:", minute));
  }else if(minute!=0){
   time.append(String.format("%d:", minute));
  }
  if(time.length()!=0){
   time.append(String.format("d", second));
  }else{
   time.append(second);
  }
  return time.toString();
}