SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");                      //获取前月的第一天          Calendar   cal_1=Calendar.getInstance();//获取当前日期           cal_1.add(Calendar.MONTH, -1);          cal_1.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天           firstDay = format.format(cal_1.getTime());          System.out.println("-----1------firstDay:"+firstDay);          //获取前月的最后一天          Calendar cale = Calendar.getInstance();             cale.set(Calendar.DAY_OF_MONTH,0);//设置为1号,当前日期既为本月第一天           lastDay = format.format(cale.getTime());          System.out.println("-----2------lastDay:"+lastDay);                                //获取当前月第一天：          Calendar c = Calendar.getInstance();              c.add(Calendar.MONTH, 0);          c.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天           String first = format.format(c.getTime());          System.out.println("===============first:"+first);                     //获取当前月最后一天          Calendar ca = Calendar.getInstance();              ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));            String last = format.format(ca.getTime());          System.out.println("===============last:"+last);                    /**     * 字符串的日期格式的计算     */    public static int daysBetween(String smdate,String bdate) throws ParseException{            SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");            Calendar cal = Calendar.getInstance();            cal.setTime(sdf.parse(smdate));            long time1 = cal.getTimeInMillis();            cal.setTime(sdf.parse(bdate));            long time2 = cal.getTimeInMillis();            long between_days=(time2-time1)/(1000*3600*24);            return Integer.parseInt(String.valueOf(between_days));    }