code: public void set(String name, Object obj)
      throws CertificateException, IOException {
          if (!(obj instanceof Date)) {
              throw new CertificateException("Attribute must be of type Date.");
          }
          if (name.equalsIgnoreCase(NOT_BEFORE)) {
              notBefore = (Date)obj;
          } else if (name.equalsIgnoreCase(NOT_AFTER)) {
              notAfter = (Date)obj;
          } else {
            throw new CertificateException("Attribute name not recognized by"
                             + " CertAttrSet:PrivateKeyUsage.");
          }
          encodeThis();
      }
docs: Set the attribute value.
  @exception CertificateException on attribute handling errors.