A DESCRIPTION OF THE PROBLEM :
In current implementation lookup of MD5 MessageDigest happens for each call to UUID#nameUUIDFromBytes(byte[]):
    MessageDigest md;
    try {
        md = MessageDigest.getInstance("MD5");
    } catch (NoSuchAlgorithmException nsae) {
        throw new InternalError("MD5 not supported", nsae);
    }
this may be enhanced by adding an internal holder-class (as done for SecureRandom via Holder inner class) to store MessageDigest which the former method would reference