code: public Date get(String name) throws CertificateException {
        if (name.equalsIgnoreCase(NOT_BEFORE)) {
            return (new Date(notBefore.getTime()));
        } else if (name.equalsIgnoreCase(NOT_AFTER)) {
            return (new Date(notAfter.getTime()));
        } else {
            throw new CertificateException("Attribute name not recognized by"
                             + " CertAttrSet:PrivateKeyUsage.");
        }
    }
docs: Get the attribute value.
  @exception CertificateException on attribute handling errors.