安卓转换时区2016-07-21T12:17:34.000Z转换成+8个小时

public static String formatDate(String date){
    if (date== null||date.equals("")) {
        throw new NullPointerException("date == null");
    }
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    //date = date.substring(0, date.indexOf("."));
            //截取19位
    date=date.length()>=19?date.substring(0,19):date.substring(0,date.length());
    date=date.replace("T"," ");
             //转换格林尼治时间
    sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
    Date d= null;
    try {
        d = sdf.parse(date);
    } catch (ParseException e) {
        e.printStackTrace();
    }
    SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            //转换成格林尼治+8时间
    sdf2.setTimeZone(TimeZone.getTimeZone("GMT+8:00"));
    return sdf2.format(d);
}

转换前的时间2016-07-21T12:17:34.000Z
转换后的时间2016-07-21 20:17:34