java获得指定时间几天前或几天后的日期

/**     * 得到几天前的时间     * @param d     * @param day     * @return     */    public static Date getDateBefore(Date d,int day){     Calendar now =Calendar.getInstance();     now.setTime(d);     now.set(Calendar.DATE,now.get(Calendar.DATE)-day);     return now.getTime();    }        /**     * 得到几天后的时间     * @param d     * @param day     * @return     */    public static Date getDateAfter(Date d,int day){     Calendar now =Calendar.getInstance();     now.setTime(d);     now.set(Calendar.DATE,now.get(Calendar.DATE)+day);     return now.getTime();    }