从Google联系人迁移到People API。为Java构建它的小贴士？

<dependency>
  <groupId>com.google.api-client</groupId>
  <artifactId>google-api-client</artifactId>
  <version>1.31.0</version>
</dependency>
<dependency>
  <groupId>com.google.oauth-client</groupId>
  <artifactId>google-oauth-client-jetty</artifactId>
  <version>1.31.0</version>
</dependency>

import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.googleapis.auth.oauth2.GoogleTokenResponse;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.services.people.v1.PeopleService;
import com.google.api.services.people.v1.PeopleServiceScopes;
import com.google.api.services.people.v1.model.ListConnectionsResponse;
import com.google.api.services.people.v1.model.Person;

import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.List;

public class PeopleApiExample {
    private static final String APPLICATION_NAME = "Your Application Name";
    private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();
    private static final List<String> SCOPES = Arrays.asList(PeopleServiceScopes.CONTACTS_READONLY);

    public static void main(String[] args) throws Exception {
        HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
        Credential credential = authorize(httpTransport);
        PeopleService peopleService = new PeopleService.Builder(httpTransport, JSON_FACTORY, credential)
                .setApplicationName(APPLICATION_NAME)
                .build();
        ListConnectionsResponse connectionsResponse = peopleService.people().connections().list("people/me")
                .setPersonFields("names,emailAddresses")
                .execute();
        List<Person> connections = connectionsResponse.getConnections();
        for (Person person : connections) {
            List<Person.Name> names = person.getNames();
            List<Person.EmailAddress> emailAddresses = person.getEmailAddresses();
            if (names != null && emailAddresses != null) {
                for (Person.Name name : names) {
                    System.out.println("Name: " + name.getDisplayName());
                }
                for (Person.EmailAddress emailAddress : emailAddresses) {
                    System.out.println("Email: " + emailAddress.getValue());
                }
            }
        }
    }

    private static Credential authorize(HttpTransport httpTransport) throws Exception {
        GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY,
                new InputStreamReader(PeopleApiExample.class.getResourceAsStream("/client_secrets.json")));
        GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
                httpTransport, JSON_FACTORY, clientSecrets, SCOPES)
                .build();
        return new GoogleCredential.Builder()
                .setTransport(httpTransport)
                .setJsonFactory(JSON_FACTORY)
                .setClientSecrets(clientSecrets)
                .build()
                .setFromTokenResponse(flow.newTokenRequest("").setScopes(SCOPES).execute());
    }
}