2019-06-20 日期类之Calender基本用法

// 获取某日期的日号
    public int getDate(Date d) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(d);
        int days = ca.get(Calendar.DATE);
        return days;
    }

// 给定日期的前/后n天
// n=-1表示前一天，n=1表示后一天
    public Date getDateForDayNum(Date date, int n) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(date);
        ca.add(Calendar.DAY_OF_MONTH, n);
        Date d = ca.getTime();
        return d;
    }


// 给定日期的前/后n月
// n=-1表示前一月，n=1表示后一月
    public Date getDateForMonthNum(Date date, int n) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(date);
        ca.add(Calendar.MONTH, n);
        Date d = ca.getTime();
        return d;
    }
//前/后某月、前/后某日的日期
    public Date getDateForMonthNum(Date date, int Month,int day) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(date);
        ca.add(Calendar.MONTH, Month);
        ca.add(Calendar.DAY_OF_MONTH, day);
        Date d = ca.getTime();
        return d;
    }

// 给定日期的前/后n年
// n=-1表示前一年，n=1表示后一年
    public Date getDateForYearNum(Date date, int n) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(date);
        ca.add(Calendar.YEAR, n);
        Date d = ca.getTime();
        return d;
    }


// 给定日期的前/后n小时
// n=-1表示前一小时，n=1表示后一小时
    public Date getDateForHourNum(Date date, int n) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(date);
        ca.add(Calendar.HOUR, n);
        Date d = ca.getTime();
        return d;
    }


// 某年某月的最后一天
    public Date getLastDay(Date date) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(date);
        ca.roll(Calendar.MONTH, 1);// 向后回滚一个月
        ca.set(Calendar.DATE, 0);
        Date time = ca.getTime();
        return time;
    }


// 某年某月的有多少天
    public int getDateNumForDate(Date date) {
        Calendar ca = Calendar.getInstance();
        ca.setTime(date);
        ca.roll(Calendar.MONTH, 1);
        ca.set(Calendar.DATE, 0);
        return ca.get(Calendar.DATE);
    }


// 某年某月是星期几（周日返回0，周一到周六就是1-6）
    public int getWeek(Date date) {
        Calendar ca = Calendar.getInstance();
        int week = ca.get(Calendar.DAY_OF_WEEK) - 1;// 设置
        return week;
    }