java常用時間處理方法收藏

    /**
     * 得到幾天前的時間
     *
     * @param d
     * @param day
     * @return
     */
    public static String getDateBefore(Date d, int day) {
        SimpleDateFormat dft = new SimpleDateFormat("yyyy-MM-dd");
        Calendar now = Calendar.getInstance();
        now.setTime(d);
        now.set(Calendar.DATE, now.get(Calendar.DATE) - day);
        return dft.format(now.getTime());
    }

    /**
     * 描述:獲取上個月的最後一天.
     *
     * @return
     */
    public static String getLastMaxMonthDate() {
        SimpleDateFormat dft = new SimpleDateFormat("yyyy-MM-dd");
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        calendar.add(Calendar.MONTH, -1);
        calendar.set(Calendar.DAY_OF_MONTH,                     
        calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
        return dft.format(calendar.getTime());
    }

    /**
     * 獲取上幾個月
     *
     * @return
     */
    public static String getLastMonth(Integer n) {
        Calendar cal = Calendar.getInstance();
        cal.add(cal.MONTH, -n);
        SimpleDateFormat dft = new SimpleDateFormat("yyyy-MM");
        String lastMonth = dft.format(cal.getTime());
        return lastMonth;
    }

    /**
     * 獲取上一個月月數
     *
     * @return
     */
    public static Integer lastMonth() {
        Calendar cal = Calendar.getInstance();
        cal.add(cal.MONTH, -1);
        SimpleDateFormat dft = new SimpleDateFormat("M");
        Integer lastMonth = Integer.parseInt(dft.format(cal.getTime()));
        return lastMonth;
    }

    //獲取前幾月的天數
    public static Integer getDaysOfMonth(Integer n) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        calendar.add(Calendar.MONTH, -n);
        return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
    }

    /**
     * 通過時間秒毫秒數判斷兩個時間的間隔
     * @param time1
     * @param time2
     * @return
     */
    public static int differentDaysByMillisecond(String time1,String time2)
    {
        if(time1.trim().indexOf(" ") >0 || time1.indexOf(":")>0){
            time1 = time1.substring(0,time1.indexOf(" "));
        }
        if(time2.trim().indexOf(" ") >0 || time2.indexOf(":")>0){
            time2 = time2.substring(0,time2.indexOf(" "));
        }
        SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
        try{
            Date date1 = sf.parse(time1+" 00:00:00");
            Date date2 = sf.parse(time2+" 00:00:00");
            int days = Math.abs((int) (( date1.getTime()-date2.getTime()) /     
  (1000*3600*24)));
            return days;
        }catch (Exception e){
            System.out.println(e.getMessage());
            return 0;
        }
    }