throw new SmbUnsupportedOperationException("Refreshing credentials is not supported by this authenticator");
    }

    @Override
    public Kerb5Authenticator clone() {
        Kerb5Authenticator auth = new Kerb5Authenticator(getSubject());
        cloneInternal(auth, this);
        return auth;
    }

    /**
     * Clone the context
     *
     * @param to the target authenticator

        // Mixed null/non-null -> not equal
        Kerb5Authenticator c = new Kerb5Authenticator(new Subject());
        assertNotEquals(a, c);

        // Same subject instance -> equal
        Subject shared = new Subject();
        Kerb5Authenticator d1 = new Kerb5Authenticator(shared);
        Kerb5Authenticator d2 = new Kerb5Authenticator(shared);
        assertEquals(d1, d2);

        Kerb5Authenticator.cloneInternal(to, from);
        to.serviceName = from.serviceName;
        to.configuration = from.configuration;
        to.cachedSubject = from.cachedSubject;
    }

    /**
     * {@inheritDoc}
     *
     * @see jcifs.smb.Kerb5Authenticator#refresh()
     */
    @Override