public static SimpleDateFormat getFormat(String format) {

        return new SimpleDateFormat(format);

    }

    /**

     * 获取上周周几的日期,默认一周从周一开始

     *

     * @param dayOfWeek

     * @param weekOffset

     * @return

     */

    public static Date getDayOfWeek(int dayOfWeek, int weekOffset) {

        return getDayOfWeek(Calendar.MONDAY, dayOfWeek, weekOffset);

    }

    /**

     * 获取上(下)周周几的日期

     *

     * @param firstDayOfWeek {@link Calendar} 值范围 <code>SUNDAY</code>,

     *                       <code>MONDAY</code>, <code>TUESDAY</code>,

     *                       <code>WEDNESDAY</code>, <code>THURSDAY</code>,

     *                       <code>FRIDAY</code>, and <code>SATURDAY</code>

     * @param dayOfWeek      {@link Calendar}

     * @param weekOffset     周偏移，上周为-1，本周为0，下周为1，以此类推

     * @return

     */

    public static Date getDayOfWeek(int firstDayOfWeek, int dayOfWeek, int weekOffset) {

        if (dayOfWeek > Calendar.SATURDAY || dayOfWeek < Calendar.SUNDAY) {

            return null;

        }

        if (firstDayOfWeek > Calendar.SATURDAY || firstDayOfWeek < Calendar.SUNDAY) {

            return null;

        }

        Calendar date = Calendar.getInstance(Locale.CHINA);

        date.setFirstDayOfWeek(firstDayOfWeek);

        // 周数减一，即上周

        date.add(Calendar.WEEK_OF_MONTH, weekOffset);

        // 日子设为周几

        date.set(Calendar.DAY_OF_WEEK, dayOfWeek);

        // 时分秒全部置0

        date.set(Calendar.HOUR_OF_DAY, 0);

        date.set(Calendar.MINUTE, 0);

        date.set(Calendar.SECOND, 0);

        date.set(Calendar.MILLISECOND, 0);

        return date.getTime();

    }

    public static void main(String[] args) {

        System.out.println(

                getFormat(DateTimeUtil.YEAR_MONTH_DATE_2).format(getDayOfWeek(Calendar.MONDAY, -1)));

        System.out.println(

                getFormat(DateTimeUtil.YEAR_MONTH_DATE_2).format(getDayOfWeek(Calendar.SUNDAY, -1)));

    }