/**

     * A hashing method that changes a string (like a URL) into a hash suitable for using as a

     * disk filename.

     */

    public static String hashKeyForDisk(String key) {

        String cacheKey;

        try {

            final MessageDigest mDigest = MessageDigest.getInstance("MD5");

            mDigest.update(key.getBytes());

            cacheKey = bytesToHexString(mDigest.digest());

        } catch (NoSuchAlgorithmException e) {

            cacheKey = String.valueOf(key.hashCode());

        }

        return cacheKey;

    }

    private static String bytesToHexString(byte[] bytes) {

        // http://stackoverflow.com/questions/332079

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < bytes.length; i++) {

            String hex = Integer.toHexString(0xFF & bytes[i]);

            if (hex.length() == 1) {

                sb.append('0');

            }

            sb.append(hex);

        }

        return sb.toString();

    }