public static String getEncoding(String str){

        String encoding = "UTF-8";

        try {

            if (str.equals(new String(str.getBytes(),encoding))) {

                return encoding;

            }

        } catch (UnsupportedEncodingException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        encoding = "GBK";

        try {

            if (str.equals(new String(str.getBytes(),encoding))) {

                return encoding;

            }

        } catch (UnsupportedEncodingException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        encoding = "ISO-8859-1";

        try {

            if (str.equals(new String(str.getBytes(),encoding))) {

                return encoding;

            }

        } catch (UnsupportedEncodingException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        encoding = "GB2312";

        try {

            if (str.equals(new String(str.getBytes(),encoding))) {

                return encoding;

            }

        } catch (UnsupportedEncodingException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        return null;

    }