String str = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS"))

.format(new Date());

Calendar calendar = Calendar.getInstance(Locale.CHINA);

calendar.setTime(new Date());

int month = calendar.get(Calendar.MONTH) + 1;

int year = calendar.get(Calendar.YEAR);

int totalDay =

calendar.getActualMaximum(Calendar.DATE);

System.out.println(totalDay);

         getActualMaximum函数。主要是用于获取一个指定日期的当月总天数