java获取当前月的开始时间和结束时间

maxDate获取的是当前月的天数

startTime拼接的本月的第一天

endTime拼接的是本月的最后一天

        Calendar a = Calendar.getInstance();
        a.set(Calendar.DATE, 1);//把日期设置为当月第一天
        a.roll(Calendar.DATE, -1);//日期回滚一天，也就是最后一天
        //当月有多少天
        int maxDate = a.get(Calendar.DATE);

        SimpleDateFormat sdfTwo = new SimpleDateFormat("yyyy-MM-");
        String startTime = sdfTwo.format(new Date()) + "01 00:00:00";
        String endTime = sdfTwo.format(new Date()) + maxDate + " 23:59:59";

增减日期时间实现方法：

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date currnetDate = new Date();
        Calendar calendar = Calendar.getInstance();

        Date dateResult = dayAddAndSub(Calendar.DATE, -1); //一个月中的某天
        //Date dateResult = test.dayAddAndSub(Calendar.HOUR , -4); //小时
        //Date dateResult = test.dayAddAndSub(Calendar.MINUTE , -60); //分钟
        //Date dateResult = test.dayAddAndSub(Calendar.MonTH , -1); //月
        System.out.println(sdf.format(dateResult) + " 00:00:00");
        System.out.println(sdf.format(currnetDate) + " 23:59:59");

    
    public Date dayAddAndSub(int currentDay,int day) {
        Calendar calendar = Calendar.getInstance();
        calendar.add(currentDay, day);
        Date startDate = calendar.getTime();
        return startDate;
    }