Access K8S API from a pod

I have a main pod that accesses and makes Kubernetes API calls to deploy other pods (the code similar below). It works fine. Now, I don't want to use the config file. I know it's possible with a service account. https://kubernetes.io/docs/tasks/access-application-cluster/access-cluster/. How do I configure a service account (e.g default service account) that allows my pod to access the APIs?

public class KubeConfigFileClientExample {
  public static void main(String[] args) throws IOException, ApiException {

    // file path to your KubeConfig
    String kubeConfigPath = "~/.kube/config";

    // loading the out-of-cluster config, a kubeconfig from file-system
    ApiClient client =
        ClientBuilder.kubeconfig(KubeConfig.loadKubeConfig(new FileReader(kubeConfigPath))).build();

    // set the global default api-client to the in-cluster one from above
    Configuration.setDefaultApiClient(client);

    // the CoreV1Api loads default api-client from global configuration.
    CoreV1Api api = new CoreV1Api();

    // invokes the CoreV1Api client
    V1PodList list = api.listPodForAllNamespaces(null, null, null, null, null, null, null, null, null);
    System.out.println("Listing all pods: ");
    for (V1Pod item : list.getItems()) {
      System.out.println(item.getMetadata().getName());
    }
  }
}

The official Java client has example for in-cluster client example.

It is quite similar to your code, you need to use a different ClientBuilder:

ApiClient client = ClientBuilder.cluster().build();

and use it like this:

    // loading the in-cluster config, including:
    //   1. service-account CA
    //   2. service-account bearer-token
    //   3. service-account namespace
    //   4. master endpoints(ip, port) from pre-set environment variables
    ApiClient client = ClientBuilder.cluster().build();

    // set the global default api-client to the in-cluster one from above
    Configuration.setDefaultApiClient(client);

    // the CoreV1Api loads default api-client from global configuration.
    CoreV1Api api = new CoreV1Api();