code: public BearerTokenResponse refreshToken(String refreshToken) throws OAuthException {
          
          logger.debug("Enter OAuth2PlatformClient::refreshToken");
          try {
              HttpRequestClient client = new HttpRequestClient(oauth2Config.getProxyConfig());
              Request request = new Request.RequestBuilder(MethodType.POST, oauth2Config.getIntuitBearerTokenEndpoint())
                                          .requiresAuthentication(true)
                                          .authString(getAuthHeader())
                                          .postParams(getUrlParameters("refresh", refreshToken, null))
                                          .build();
              Response response = client.makeRequest(request);
  
              logger.debug("Response Code : "+ response.getStatusCode());
              if (response.getStatusCode() != 200) {
                  logger.debug("failed getting access token");
                  throw new OAuthException("failed getting access token", response.getStatusCode() + "");
              }
   
              ObjectReader reader = mapper.readerFor(BearerTokenResponse.class);
              BearerTokenResponse bearerTokenResponse = reader.readValue(response.getContent());
              return bearerTokenResponse;
          }
          catch (Exception ex) {
              logger.error("Exception while calling refreshToken ", ex);
              throw new OAuthException(ex.getMessage(), ex);
          } 
      }
docs: Method to renew OAuth2 tokens by passing the refreshToken
  
  @param refreshToken
  @return
  @throws OAuthException