code: public Observable<ServiceResponse<P2SVpnServerConfigurationInner>> createOrUpdateWithServiceResponseAsync(String resourceGroupName, String virtualWanName, String p2SVpnServerConfigurationName, P2SVpnServerConfigurationInner p2SVpnServerConfigurationParameters) {
          if (this.client.subscriptionId() == null) {
              throw new IllegalArgumentException("Parameter this.client.subscriptionId() is required and cannot be null.");
          }
          if (resourceGroupName == null) {
              throw new IllegalArgumentException("Parameter resourceGroupName is required and cannot be null.");
          }
          if (virtualWanName == null) {
              throw new IllegalArgumentException("Parameter virtualWanName is required and cannot be null.");
          }
          if (p2SVpnServerConfigurationName == null) {
              throw new IllegalArgumentException("Parameter p2SVpnServerConfigurationName is required and cannot be null.");
          }
          if (p2SVpnServerConfigurationParameters == null) {
              throw new IllegalArgumentException("Parameter p2SVpnServerConfigurationParameters is required and cannot be null.");
          }
          Validator.validate(p2SVpnServerConfigurationParameters);
          final String apiVersion = "2018-08-01";
          Observable<Response<ResponseBody>> observable = service.createOrUpdate(this.client.subscriptionId(), resourceGroupName, virtualWanName, p2SVpnServerConfigurationName, apiVersion, p2SVpnServerConfigurationParameters, this.client.acceptLanguage(), this.client.userAgent());
          return client.getAzureClient().getPutOrPatchResultAsync(observable, new TypeToken<P2SVpnServerConfigurationInner>() { }.getType());
      }
docs: Creates a P2SVpnServerConfiguration to associate with a VirtualWan if it doesn't exist else updates the existing P2SVpnServerConfiguration.
  
  @param resourceGroupName The resource group name of the VirtualWan.
  @param virtualWanName The name of the VirtualWan.
  @param p2SVpnServerConfigurationName The name of the P2SVpnServerConfiguration.
  @param p2SVpnServerConfigurationParameters Parameters supplied to create or Update a P2SVpnServerConfiguration.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request