日常总结-Java的日期操作

1、获取当天的0点和23:59:59 999，以此类推，可以获取任何时刻。

 public static Calendar beginOfDay(Calendar calendar) {
        calendar.set(11, 0);
        calendar.set(12, 0);
        calendar.set(13, 0);
        calendar.set(14, 0);
        return calendar;
    }

    public static Calendar endOfDay(Calendar calendar) {
        calendar.set(11, 23);
        calendar.set(12, 59);
        calendar.set(13, 59);
        calendar.set(14, 999);
        return calendar;
    }

2、判断当前时刻是否在时间范围内

/**
     * 检测当前时间是否在11:30--13:00之间
     *
     * @return
     */
    public static boolean checkRange() {
        Date nowDate = new Date();
        Calendar cal11 = Calendar.getInstance();
        cal11.setTime(nowDate);
        cal11.set(Calendar.HOUR_OF_DAY, 11);
        cal11.set(Calendar.MINUTE, 30);
        cal11.set(Calendar.SECOND, 0);
        cal11.set(Calendar.MILLISECOND, 0);

        Calendar cal13 = Calendar.getInstance();
        cal13.setTime(nowDate);
        cal13.set(Calendar.HOUR_OF_DAY, 13);
        cal13.set(Calendar.MINUTE, 0);
        cal13.set(Calendar.SECOND, 0);
        cal13.set(Calendar.MILLISECOND, 0);

        long now = nowDate.getTime();

        return cal11.getTime().getTime() <= now && now <= cal13.getTime().getTime();
    }

3、获取本周一

    public static Date getThisWeekMonday(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        // 获得当前日期是一个星期的第几天
        int dayWeek = cal.get(Calendar.DAY_OF_WEEK);
        if (1 == dayWeek) {
            cal.add(Calendar.DAY_OF_MONTH, -1);
        }
        // 设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
        cal.setFirstDayOfWeek(Calendar.MONDAY);
        // 获得当前日期是一个星期的第几天
        int day = cal.get(Calendar.DAY_OF_WEEK);
        // 根据日历的规则，给当前日期减去星期几与一个星期第一天的差值
        cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day);
        return cal.getTime();
    }

 4、给定日期加减天数

 private static Date offset(Date date, int calendar, int offset) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        cal.add(6, offset);
        return cal.getTime();
    }