src/org/nutz/lang/Times.java
public static Date nextWeek(Date date, int week) {
        Calendar cal = Calendar.getInstance();
        if (date != null) {
            cal.setTime(date);
        }
        cal.add(Calendar.WEEK_OF_MONTH, week);
        return cal.getTime();
    }
public static Date nextWeek(Date date, int week) {
        Calendar cal = Calendar.getInstance();
        if (date != null) {
            cal.setTime(date);
        }
        cal.add(Calendar.WEEK_OF_MONTH, week);
        return cal.getTime();
    }
取得指定日期过 day 周后的日期 (当 day 为负数表示指定月之前)

@param date
日期 为null时表示当天