data和nowTime格式為：2018-8-24  可以通過SimpleDateFormat.format 得到

public static String getAge(String date, String nowTime)
{
    if (TextUtils.isEmpty(date)||TextUtils.isEmpty(nowTime)){
        return "";
    }
    String[] data = date.split("-");
    String[] nowData = nowTime.split("-");
    if (data.length < 3 || nowData.length < 3)
        return "";
    
    Calendar birthday = new GregorianCalendar(Integer.valueOf(data[0]),
            Integer.valueOf(data[1]), Integer.valueOf(data[2]));
    
    Calendar now = new GregorianCalendar(Integer.valueOf(nowData[0]),
            Integer.valueOf(nowData[1]), Integer.valueOf(nowData[2]));
    int day = now.get(Calendar.DAY_OF_MONTH)
            - birthday.get(Calendar.DAY_OF_MONTH);
    int month = now.get(Calendar.MONTH) - birthday.get(Calendar.MONTH);
    int year = now.get(Calendar.YEAR) - birthday.get(Calendar.YEAR);
    // 按照減法原理，先day相減，不夠向month借；然後month相減，不夠向year借；最後year相減。
    if (day < 0)
    {
        month -= 1;
        now.add(Calendar.MONTH, -1);// 得到上一個月，用來得到上個月的天數。
        day = day + now.getActualMaximum(Calendar.DAY_OF_MONTH);
    }
    if (month < 0)
    {
        month = (month + 12) % 12;
        year--;
    }
    System.out.println("年齡：" + year + "歲" + month + "月" + day + "天");
    StringBuffer tag = new StringBuffer();
    if (year > 0)
    {
        tag.append(year + "歲");
    }
    if (month > 0)
    {
        tag.append(month + "個月");
    }
    if (day > 0)
    {
        tag.append(day + "天");
    }
    if (year == 0 && month == 0 && day == 0)
    {
        tag.append("今日出生");
    }
    return String.valueOf(tag);
}