GoogleID Token with Google api client library

GoogleIDTokenAPI.java

package com.test;

import java.util.Arrays;
import java.io.FileInputStream;
import java.io.File;

import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.jackson2.JacksonFactory;

import com.google.api.services.iamcredentials.v1.IAMCredentials;
import com.google.api.services.iamcredentials.v1.IAMCredentialsScopes;

import com.google.api.services.iamcredentials.v1.model.GenerateIdTokenRequest;
import com.google.api.services.iamcredentials.v1.model.GenerateIdTokenResponse;

/*
<dependency>
 <groupId>com.google.apis</groupId>
 <artifactId>google-api-services-iamcredentials</artifactId>
 <version>v1-rev46-1.25.0</version>
</dependency>
*/

public class TestApp {
    public static void main(String[] args) {
        TestApp tc = new TestApp();
    }
        
    public TestApp() {
        try
        {

            HttpTransport httpTransport = new NetHttpTransport();             
            JacksonFactory jsonFactory = new JacksonFactory();

            // export GOOGLE_APPLICATION_CREDENTIALS=/path/to/svc.json      
            //GoogleCredential credential = GoogleCredential.getApplicationDefault(httpTransport,jsonFactory);
            String SERVICE_ACCOUNT_JSON_FILE = "/path/to/svc.json";
            FileInputStream inputStream = new FileInputStream(new File(SERVICE_ACCOUNT_JSON_FILE));
            GoogleCredential credential = GoogleCredential.fromStream(inputStream, httpTransport, jsonFactory);

            if (credential.createScopedRequired())
                credential = credential.createScoped(Arrays.asList(IAMCredentialsScopes.CLOUD_PLATFORM));
                        
            IAMCredentials service = new IAMCredentials.Builder(httpTransport, jsonFactory, credential)
                        .setApplicationName("oauth client")   
                        .build();                           

            String name = "projects/-/serviceAccounts/impersonated-account@fabled-ray-104117.iam.gserviceaccount.com";

            GenerateIdTokenRequest idreq = new GenerateIdTokenRequest();
            idreq.setAudience("https://foo");
            GenerateIdTokenResponse idresp = service.projects().serviceAccounts().generateIdToken(name, idreq).execute();
            System.out.println(idresp.toPrettyString());
            
        } 
        catch (Exception ex) {
            System.out.println("Error:  " + ex);
        }
    }
        
}