code: public Observable<ServiceResponse<ResourceListKeysInner>> regenerateKeysWithServiceResponseAsync(String resourceGroupName, String namespaceName, String authorizationRuleName, String policyKey) {
          if (resourceGroupName == null) {
              throw new IllegalArgumentException("Parameter resourceGroupName is required and cannot be null.");
          }
          if (namespaceName == null) {
              throw new IllegalArgumentException("Parameter namespaceName is required and cannot be null.");
          }
          if (authorizationRuleName == null) {
              throw new IllegalArgumentException("Parameter authorizationRuleName is required and cannot be null.");
          }
          if (this.client.subscriptionId() == null) {
              throw new IllegalArgumentException("Parameter this.client.subscriptionId() is required and cannot be null.");
          }
          if (this.client.apiVersion() == null) {
              throw new IllegalArgumentException("Parameter this.client.apiVersion() is required and cannot be null.");
          }
          PolicykeyResource parameters = new PolicykeyResource();
          parameters.withPolicyKey(policyKey);
          return service.regenerateKeys(resourceGroupName, namespaceName, authorizationRuleName, this.client.subscriptionId(), this.client.apiVersion(), this.client.acceptLanguage(), parameters, this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<ResourceListKeysInner>>>() {
                  @Override
                  public Observable<ServiceResponse<ResourceListKeysInner>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<ResourceListKeysInner> clientResponse = regenerateKeysDelegate(response);
                          return Observable.just(clientResponse);
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Regenerates the Primary/Secondary Keys to the Namespace Authorization Rule.
  
  @param resourceGroupName The name of the resource group.
  @param namespaceName The namespace name.
  @param authorizationRuleName The connection string of the namespace for the specified authorizationRule.
  @param policyKey Name of the key that has to be regenerated for the Namespace/Notification Hub Authorization Rule. The value can be Primary Key/Secondary Key.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ResourceListKeysInner object