java怎么把一个string个日期类型 如“Fri Feb 01 00:00:00 GMT+08:00 2013”转换成“yyyy-mm-dd”

String dateString = "Fri Feb 01 00:00:00 GMT+08:00 2013";
        SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy",Locale.US);
        TimeZone tz = TimeZone.getTimeZone("GMT+8");
        sdf.setTimeZone(tz);
        String str = sdf.format(Calendar.getInstance().getTime());
        System.out.println(str);
        Date s;
        try {
            s = sdf.parse(dateString);
            sdf = new SimpleDateFormat("yyyy-MM-dd");
            System.out.println(sdf.format(s));
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }