ImageLoader.java

private static String getCacheKey(String url, int maxWidth, int maxHeight) {
        return md5(new StringBuilder(url.length() + 12).append("#W").append(maxWidth)
                .append("#H").append(maxHeight).append(url).toString());
    }

    private static final String md5(final 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++) {
                String h = Integer.toHexString(0xFF & messageDigest[i]);
                while (h.length() < 2)
                    h = "0" + h;
                hexString.append(h);
            }
            return hexString.toString();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("Missing MD5?",e);
        }
    }