How to convert a byte array to a string, and string to a byte array with GWT?

Good question. I didn't realize it before.

as far as I know there is only 2 main method that convert byte array to String

1. You mentioned it
2. The fantastic way with java.io package that you can't use it on client-side

Here is mine implementation. I think it may be helpful to you

public static String convertByteArrayToString(byte[] byteArray) {
    String s = "";

    for (int i = 0; i < byteArray.length; i++) {
        s += (char) (byteArray[i]);
    }

    return s;
}

You can test it :

byte[] byteArray = new byte[] { 87, 79, 87, 46, 46, 46 };

System.out.println(convertByteArrayToString(byteArray));
System.out.println(new String(byteArray));

The following code should work, just specify the number of bytes per character.

public class GwtPlayground implements EntryPoint
{
    static final Logger logger = Logger.getLogger("");

    @Override
    public void onModuleLoad()
    {
        VerticalPanel loggerArea = new VerticalPanel();
        logger.addHandler(new HasWidgetsLogHandler(loggerArea));
        RootPanel.get().add(loggerArea);

        String original = new String("A" + "\uffea" + "\u00f1" + "\u00fc" + "C");

        logger.info("original = " + original);
        byte[] utfBytes = getBytes(original, 2);

        String roundTrip = getString(utfBytes, 2);
        logger.info("roundTrip = " + roundTrip);
    }

    public static byte[] getBytes(String string, int bytesPerChar)
    {
        char[] chars = string.toCharArray();
        byte[] toReturn = new byte[chars.length * bytesPerChar];
        for (int i = 0; i < chars.length; i++)
        {
            for (int j = 0; j < bytesPerChar; j++)
                toReturn[i * bytesPerChar + j] = (byte) (chars[i] >>> (8 * (bytesPerChar - 1 - j)));
        }
        return toReturn;
    }

    public static String getString(byte[] bytes, int bytesPerChar)
    {
        char[] chars = new char[bytes.length / bytesPerChar];
        for (int i = 0; i < chars.length; i++)
        {
            for (int j = 0; j < bytesPerChar; j++)
            {
                int shift = (bytesPerChar - 1 - j) * 8;
                chars[i] |= (0x000000FF << shift) & (((int) bytes[i * bytesPerChar + j]) << shift);
            }
        }
        return new String(chars);
    }
}