根据身份证获取周岁

偶然看到根据身份证获取周岁的代码，没具体考察正确与否，不清楚是否判断身份证不同位数的问题，先保留一下。

/**
     * 根据身份证号获取年龄(周岁)
     * @param idCard 身份证
     * @return 年龄
     */
    public static int getFullAgeByIdCard(String idCard){
        Calendar cal1 = Calendar.getInstance();
        Calendar today = Calendar.getInstance();
        cal1.set(Integer.parseInt(idCard.substring(6,10)),
                Integer.parseInt(idCard.substring(10,12)),
                Integer.parseInt(idCard.substring(12,14)));
        int m = (today.get(today.MONTH))+1 - (cal1.get(cal1.MONTH));
        int y = (today.get(today.YEAR)) - (cal1.get(cal1.YEAR));
        int d = (today.get(today.DAY_OF_MONTH)) - (cal1.get(cal1.DAY_OF_MONTH));
        if (m <= 0){
            if (m == 0){
                if (d < 0) y--;
            }else {
                y--;
            }
        }
        return y;
    }