通过日期计算周几

/**
     * 通过日期获取周几
     * @param pTime
     * @return String
     * @throws Throwable
     */
    public static String dayForWeek(String pTime) throws Exception{
        SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd",Locale.CHINA);
         
        Calendar cal =  Calendar.getInstance();
        cal.setTime(format.parse(pTime));
        int dayForWeek = 0;
        if (cal.get(Calendar.DAY_OF_WEEK) == 1) {
            dayForWeek = 7;
        } else {
            dayForWeek = cal.get(Calendar.DAY_OF_WEEK) - 1;
        }
         
        String week_value = "";
        switch (dayForWeek) {
            case 1:
                week_value = "周一";
                break;
            case 2:
                week_value = "周二";
                break;
            case 3:
                week_value = "周三";
                break;
            case 4:
                week_value = "周四";
                break;
            case 5:
                week_value = "周五";
                break;
            case 6:
                week_value = "周六";
                break;
                 
            case 7:
                week_value = "周日";
                break;
     
            default:
                break;
            }
         
        return week_value;
    }