java获取时间，mysql获取时间

java

获取和今日偏移指定日期的字符串

public static String getTodayDifString(int dif) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        calendar.add(Calendar.DATE, dif);
        Date date = calendar.getTime();
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(date);
    }

获取指定日期所在周的周一日期

public static String getFirstDayOfWeek(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        if (calendar.get(Calendar.DAY_OF_WEEK) == 1) {
            calendar.add(Calendar.DATE, -6);
        } else {
            calendar.add(Calendar.DATE, 2 - calendar.get(Calendar.DAY_OF_WEEK));
        }
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime());
    }

获取指定日期所在周的周日日期

public static String getLastDayOfWeek(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        if (calendar.get(Calendar.DAY_OF_WEEK) != 1) {
            calendar.add(Calendar.DATE, 8 - calendar.get(Calendar.DAY_OF_WEEK));
        }
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime());
    }

获取指定日期所在月的第一天

 public static String getFirstDayOfMonth(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.DATE, -calendar.get(Calendar.DAY_OF_MONTH) + 1);
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime());
    }

获取指定日期所在月的最后一天

public static String getLastDayOfMonth(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.set(Calendar.DAY_OF_MONTH,calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime());
    }

mysql

获取指定日期所在周的周一日期

select date_sub(now(),INTERVAL weekday(now())+0 day);

获取指定日期所在周的周日日期

select date_sub(now(),INTERVAL weekday(now())-6 day);

 获取指定日期所在月的第一天

select date_add(curdate(),interval -day(curdate())+1 day) ;

 获取指定日期所在月的最后一天

select last_day(now());