code: public void set(String name, Object obj) throws IOException {
          if (name.equalsIgnoreCase(NUMBER)) {
              if (!(obj instanceof BigInteger)) {
                  throw new IOException("Attribute must be of type BigInteger.");
              }
              crlNumber = (BigInteger)obj;
          } else {
            throw new IOException("Attribute name not recognized by"
                                  + " CertAttrSet:" + extensionName + ".");
          }
          encodeThis();
      }
docs: Set the attribute value.