Create an Access token from the Service Account key

AccessToken.java

import com.google.api.services.forms.v1.FormsScopes;
import com.google.auth.oauth2.GoogleCredentials;

import java.io.IOException;
import java.util.Objects;

public static String getAccessToken() throws IOException {
      GoogleCredentials credential = GoogleCredentials.fromStream(Objects.requireNonNull(
              Main.class.getResourceAsStream("cred.json"))).createScoped(FormsScopes.all());
      return credential.getAccessToken() != null ?
              credential.getAccessToken().getTokenValue() :
              credential.refreshAccessToken().getTokenValue();
}