//获取年月，最大日期

//获取年月，最大日期
        SimpleDateFormat format = new  SimpleDateFormat("yyyy-MM-dd");
        Calendar cal = Calendar.getInstance();
        Date date = format.parse(a);
        cal.setTime(date);
        int year = cal.get(Calendar.YEAR);
        int month = cal.get(Calendar.MONTH);
        //设置年份  
        cal.set(Calendar.YEAR,year);  
        //设置月份  
        cal.set(Calendar.MONTH, month);  
        //获取某月最大天数  
        int lastDay = cal.getActualMaximum(Calendar.DAY_OF_MONTH);  
        cal.set(Calendar.DAY_OF_MONTH, lastDay);
        System.out.println(format.format(cal.getTime()));