java中关于时间的计算

1.描述：在原有时间上增加一个时间差：

    代码示例：

      Date psd = sysDate();

      String workTimeP1 = mapP.get("WORK_TIME_") != null ? mapP.get("WORK_TIME_").toString() : "0"; 
      int news=Integer.parseInt(workTimeP1)*60;
      Date ped=DateUtils.addSeconds(psd,news);

2.时间差的计算代码：以毫秒为例

    public static int secondsBetween(Date smdate,Date bdate) throws Exception  {     
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");   //时间格式
        smdate=sdf.parse(sdf.format(smdate));    
        bdate=sdf.parse(sdf.format(bdate));   
        Calendar cal = Calendar.getInstance();     
        cal.setTime(smdate);     
        long time1 = cal.getTimeInMillis();                  
        cal.setTime(bdate);     
        long time2 = cal.getTimeInMillis();          
        long between_seconds=(time2-time1)/(1000);   
             
       return Integer.parseInt(String.valueOf(between_seconds));            
    }  

  Tbpbc35 c35=c35List.get(0);
   c35.setLotStartTime(c36MinDate);//lot开始时间为明细表的最早开始时间
   c35.setLotEndTime(c36MaxDate);//lot结束时间为明细表的最晚结束时间
   int seconds=this.secondsBetween(c35.getLotStartTime(),c35.getLotEndTime());
   int mintues=seconds/60;
   BigDecimal mb=new BigDecimal(mintues);
   c35.setWorkTotalTime(mb);

3.时间的加法：

    int ps = c36.getProdStartDate().getSeconds();//当前时间的华为秒
    int news = ps - betweenDate;//当前时间加
    Date s = c36.getProdStartDate();//当前时间
    s.setSeconds(news);
    c36.setProdStartDate(s);