Encoding and Decoding messages in Radix transactions

MessageEncoder.java

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;

import java.nio.charset.StandardCharsets;

public class MessageEncoder {

    public static String decode(String message) throws DecoderException {
        if (message.startsWith("0000")) { // sent through new API
            byte[] bytes = Hex.decodeHex(message.substring(4).toCharArray());
            return new String(bytes, StandardCharsets.UTF_8);
        } else if (message.startsWith("30303030"))  { // sent through old API,
            // you can skip this section if you are going to process only transactions sent after March 1
            byte[] bytes = Hex.decodeHex(message.toCharArray());
            return decode(new String(bytes, StandardCharsets.UTF_8));
        } else {
            throw new DecoderException("Can't parse message: " + message);
        }
    }

    public static String encode(String message) {
        return "0000" + Hex.encodeHexString(message.getBytes(StandardCharsets.UTF_8));
    }
}