使用java的Calendar对象获得当前日期

思路：

先获得当前季度的开始和结束日期，在当前日期的基础上往前推3个月即上个季度的开始和结束日期

  public static String getLastQuarterTime(boolean flag){
    SimpleDateFormat shortSdf = new SimpleDateFormat("yyyy-MM-dd");
    SimpleDateFormat longSdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
     
    String resultDate="";
    Date now = null;
    try {
      Calendar calendar = Calendar.getInstance();
      int currentMonth = calendar.get(Calendar.MONTH) + 1;
      //true：开始日期；false：结束日期
      if(flag){
 if (currentMonth >= 1 && currentMonth <= 3)
   calendar.set(Calendar.MONTH, 0);
 else if (currentMonth >= 4 && currentMonth <= 6)
   calendar.set(Calendar.MONTH, 3);
 else if (currentMonth >= 7 && currentMonth <= 9)
   calendar.set(Calendar.MONTH, 6);
 else if (currentMonth >= 10 && currentMonth <= 12)
   calendar.set(Calendar.MONTH, 9);
 calendar.set(Calendar.DATE, 1);
  
 now = longSdf.parse(shortSdf.format(calendar.getTime()) + " 00:00:00");
      }else{
 if (currentMonth >= 1 && currentMonth <= 3) {
   calendar.set(Calendar.MONTH, 2);
   calendar.set(Calendar.DATE, 31);
 } else if (currentMonth >= 4 && currentMonth <= 6) {
   calendar.set(Calendar.MONTH, 5);
   calendar.set(Calendar.DATE, 30);
 } else if (currentMonth >= 7 && currentMonth <= 9) {
   calendar.set(Calendar.MONTH, 8);
   calendar.set(Calendar.DATE, 30);
 } else if (currentMonth >= 10 && currentMonth <= 12) {
   calendar.set(Calendar.MONTH, 11);
   calendar.set(Calendar.DATE, 31);
 }
 now = longSdf.parse(shortSdf.format(calendar.getTime()) + " 23:59:59");
      }
      calendar.setTime(now);// 设置日期
      calendar.add(Calendar.MONTH, -3);
      resultDate = longSdf.format(calendar.getTime());

    } catch (Exception e) {
      ;
    }
    return resultDate;
  }