java获取系统指定时间年月日

java获取系统指定时间年月日

     private String setDateTime(String falg) {
         Calendar c = Calendar.getInstance();
         c.setTimeInMillis(new Date().getTime());
         SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
         SimpleDateFormat dateMouthFormat = new SimpleDateFormat("yyyy-MM");
         SimpleDateFormat dateYearFormat = new SimpleDateFormat("yyyy");
         if (falg.equals("daystartTime")) {
             c.add(Calendar.DATE, -45);
             return dateFormat.format(c.getTime());
         } else if (falg.equals("dayendTime")) {
             return dateFormat.format(c.getTime());
         } else if (falg.equals("MouthstartTime")) {
             c.add(Calendar.YEAR, -1);
             return dateMouthFormat.format(c.getTime());
         } else if (falg.equals("MouthendTime")) {
             return dateMouthFormat.format(c.getTime());
         } else if (falg.equals("YearstartTime")) {
             c.add(Calendar.YEAR, -3);
             return dateYearFormat.format(c.getTime());
         } else if (falg.equals("YearendTime")) {
             return dateYearFormat.format(c.getTime());
         } else {
             return null;
         }
     }