获取当前日期的前四个季度，其后在获取这四个季度的开始时间和结束时间

import java.text.SimpleDateFormat;import java.util.Calendar;public class T2 {    public static void main(String[] args) {        Calendar c = Calendar.getInstance();                int m = c.get(Calendar.MONTH) + 1;            //月份        int s = (int)Math.ceil( (m - 1)  / 3) + 1;     //季度        System.out.println(s);        int em = (s - 1) * 3;                        //上一个季度最后一个月                Calendar sc = Calendar.getInstance();        sc.setTimeInMillis(c.getTimeInMillis());        sc.set(Calendar.MONTH, em);        sc.set(Calendar.DAY_OF_MONTH, 1);        sc.set(Calendar.HOUR_OF_DAY, 0);        sc.set(Calendar.MINUTE, 0);        sc.set(Calendar.SECOND, 0);        sc.set(Calendar.MILLISECOND, 0);        sc.add(Calendar.MILLISECOND, -1);        out(sc);//结束时间                Calendar ec = Calendar.getInstance();        ec.setTimeInMillis(c.getTimeInMillis());        ec.set(Calendar.MONTH, em - 1);    //month 基于0,一月的值是0        ec.set(Calendar.DAY_OF_MONTH, 1);        ec.set(Calendar.HOUR_OF_DAY, 0);        ec.set(Calendar.MINUTE, 0);        ec.set(Calendar.SECOND, 0);        ec.set(Calendar.MILLISECOND, 0);        ec.add(Calendar.MONTH, -11);     //向前12个月，但是-11        out(ec);//开始时间            }        protected static void out(Calendar c){        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");        String str = sdf.format(c.getTime());        System.out.println(str);    }    }