How to hash a string in Android?

That function above from (http://www.androidsnippets.org/snippets/52/index.html) is flawed. If one of the digits in the messageDigest is not a two character hex value (i.e. 0x09), it doesn't work properly because it doesn't pad with a 0. If you search around you'll find that function and complaints about it not working. Here a better one found in the comment section of this page, which I slightly modified:

public static String md5(String s) 
{
    MessageDigest digest;
    try
    {
        digest = MessageDigest.getInstance("MD5");
        digest.update(s.getBytes(Charset.forName("US-ASCII")),0,s.length());
        byte[] magnitude = digest.digest();
        BigInteger bi = new BigInteger(1, magnitude);
        String hash = String.format("%0" + (magnitude.length << 1) + "x", bi);
        return hash;
    }
    catch (NoSuchAlgorithmException e)
    {
        e.printStackTrace();
    }
    return "";
}

not working method:

public static String md5(String s) {
    try {
        // Create MD5 Hash
        MessageDigest digest = java.security.MessageDigest
                .getInstance("MD5");
        digest.update(s.getBytes());
        byte messageDigest[] = digest.digest();

        // Create Hex String
        StringBuffer hexString = new StringBuffer();
        for (int i = 0; i < messageDigest.length; i++)
            hexString.append(Integer.toHexString(0xFF & messageDigest[i]));
        return hexString.toString();

    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return "";
}

result: 1865e62e7129927f6e4cd9bff104f0 (length 30)

working method:

public static final String md5(final String toEncrypt) {
    try {
        final MessageDigest digest = MessageDigest.getInstance("md5");
        digest.update(toEncrypt.getBytes());
        final byte[] bytes = digest.digest();
        final StringBuilder sb = new StringBuilder();
        for (int i = 0; i < bytes.length; i++) {
            sb.append(String.format("%02X", bytes[i]));
        }
        return sb.toString().toLowerCase();
    } catch (Exception exc) {
        return ""; // Impossibru!
    }
}

result: 1865e62e7129927f6e4c0d9bff1004f0 (length 32)

This snippet calculate md5 for any given string

public String md5(String s) {
    try {
        // Create MD5 Hash
        MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
        digest.update(s.getBytes());
        byte messageDigest[] = digest.digest();

        // Create Hex String
        StringBuffer hexString = new StringBuffer();
        for (int i=0; i<messageDigest.length; i++)
            hexString.append(Integer.toHexString(0xFF & messageDigest[i]));
        return hexString.toString();

    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return "";
}

Source: http://www.androidsnippets.com/snippets/52/index.html

Hope this is useful for you