static {
        PREFERRED_MECHS.add(new ASN1ObjectIdentifier("1.2.840.113554.1.2.2"));
        PREFERRED_MECHS.add(new ASN1ObjectIdentifier("1.2.840.48018.1.2.2"));
    }


    /**
     * Construct a <code>Kerb5Authenticator</code> object with <code>Subject</code>
     * which hold TGT retrieved from KDC. If multiple TGT are contained, the
     * first one will be used to retrieve user principal.
     *