getting an error while acessing google calendar API. Null pointer exception - nullpointerexception

Question

I get a error message below .. when I run the code for hitting google Calendar API.There is a client_secrets.json file that has the credentials (client ID and redirectID) . I unzipped and ran the package google gave, it successfully runs and I could see that by a "Success,Add code here"message. after which it throws me a nullpointer exception for which I'm not sure what has gone wrong.please help. Downloaded the sample project from here https://developers.google.com/api-client-library/java/apis/calendar/v3
May 01, 2014 12:59:42 PM com.google.api.client.util.store.FileDataStoreFactory setPermissionsToOwnerOnly
WARNING: unable to change permissions for everybody: C:\Users\Aishwarya Anand\.store\calendar_sample
May 01, 2014 12:59:42 PM com.google.api.client.util.store.FileDataStoreFactory setPermissionsToOwnerOnly
WARNING: unable to change permissions for owner: C:\Users\Aishwarya Anand\.store\calendar_sample
Success! Now add code here.
inserting event ...
Aish Event from the new Google API
2014-05-01T16:59:42.545Z
2014-05-01T17:59:42.545Z
java.lang.NullPointerException
at com.google.api.client.repackaged.com.google.common.base.Preconditions.checkNotNull(Preconditions.java:191)
at com.google.api.client.util.Preconditions.checkNotNull(Preconditions.java:127)
at com.google.api.client.json.jackson2.JacksonFactory.createJsonParser(JacksonFactory.java:96)
at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:85)
at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:81)
at com.google.api.client.auth.oauth2.TokenResponseException.from(TokenResponseException.java:88)
at com.google.api.client.auth.oauth2.TokenRequest.executeUnparsed(TokenRequest.java:287)
at com.google.api.client.auth.oauth2.TokenRequest.execute(TokenRequest.java:307)
at com.google.api.client.auth.oauth2.Credential.executeRefreshToken(Credential.java:570)
at com.google.api.client.auth.oauth2.Credential.refreshToken(Credential.java:489)
at com.google.api.client.auth.oauth2.Credential.intercept(Credential.java:217)
at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:859)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:410)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:343)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:460)
at com.google.api.services.samples.calendar.cmdline.CalendarSample.insertEventTest(CalendarSample.java:170)
at com.google.api.services.samples.calendar.cmdline.CalendarSample.main(CalendarSample.java:116)
Class here,
package com.google.api.services.samples.calendar.cmdline;
import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.extensions.java6.auth.oauth2.AuthorizationCodeInstalledApp;
import com.google.api.client.extensions.jetty.auth.oauth2.LocalServerReceiver;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets;
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.client.util.DateTime;
import com.google.api.client.util.store.DataStoreFactory;
import com.google.api.client.util.store.FileDataStoreFactory;
import com.google.api.services.calendar.Calendar;
import com.google.api.services.calendar.CalendarScopes;
import com.google.api.services.calendar.model.*;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.Date;
import java.util.TimeZone;
public class CalendarSample {
/**
* Be sure to specify the name of your application. If the application name is {#code null} or
* blank, the application will log a warning. Suggested format is "MyCompany-ProductName/1.0".
*/
private static final String APPLICATION_NAME = "Caritas-CalendarAPI/1.0";
/** Directory to store user credentials. */
private static final java.io.File DATA_STORE_DIR =
new java.io.File(System.getProperty("user.home"), ".store/calendar_sample");
/**
* Global instance of the {#link DataStoreFactory}. The best practice is to make it a single
* globally shared instance across your application.
*/
private static FileDataStoreFactory dataStoreFactory;
/** Global instance of the JSON factory. */
private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();
/** Global instance of the HTTP transport. */
private static HttpTransport httpTransport;
#SuppressWarnings("unused")
private static Calendar client;
/** Authorizes the installed application to access user's protected data. */
private static Credential authorize() throws Exception {
// load client secrets
GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY,
new InputStreamReader(CalendarSample.class.getResourceAsStream("/client_secrets.json")));
// Set up authorization code flow.
// Ask for only the permissions you need. Asking for more permissions will
// reduce the number of users who finish the process for giving you access
// to their accounts. It will also increase the amount of effort you will
// have to spend explaining to users what you are doing with their data.
// Here we are listing all of the available scopes. You should remove scopes
// that you are not actually using.
Set<String> scopes = new HashSet<String>();
scopes.add(CalendarScopes.CALENDAR);
scopes.add(CalendarScopes.CALENDAR_READONLY);
GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(
httpTransport, JSON_FACTORY, clientSecrets, scopes)
.setDataStoreFactory(dataStoreFactory)
.build();
// authorize
return new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver()).authorize("user");
}
public static void main(String[] args) {
try {
// initialize the transport
httpTransport = GoogleNetHttpTransport.newTrustedTransport();
// initialize the data store factory
dataStoreFactory = new FileDataStoreFactory(DATA_STORE_DIR);
// authorization
Credential credential = authorize();
// set up global Calendar instance
client = new Calendar.Builder(httpTransport, JSON_FACTORY, credential).setApplicationName(APPLICATION_NAME).build();
System.out.println("Success! Now add code here.");
insertEventTest();
//getEventList();
//getEventTest();
//sertEventTest();
} catch (IOException e) {
System.err.println(e.getMessage());
} catch (Throwable t) {
t.printStackTrace();
}
System.exit(1);
}
private static void getEventList() throws IOException {
String pageToken = null;
do {
Events events = client.events().list("primary").setPageToken(pageToken).execute();
List<Event> items = events.getItems();
for (Event event : items) {
System.out.println(" id: " + event.getId() + "; summary: " + event.getSummary());
}
pageToken = events.getNextPageToken();
} while (pageToken != null);
}
private static void getEventTest() throws IOException {
String eventId = "idkoi3c55lvegs2ev333u28grk5c";
Event event = client.events().get("primary", eventId).execute();
System.out.println(event.getSummary());
}
private static void insertEventTest() throws IOException {
System.out.println("inserting event ...");
Event event = new Event();
event.setSummary("Aish Event from the new Google API");
event.setLocation("Somewhere");
System.out.println(event.getSummary());
Date startDate = new Date();
Date endDate = new Date(startDate.getTime() + 3600000);
DateTime start = new DateTime(startDate, TimeZone.getTimeZone("UTC"));
event.setStart(new EventDateTime().setDateTime(start));
System.out.println(start.toStringRfc3339());
DateTime end = new DateTime(endDate, TimeZone.getTimeZone("UTC"));
event.setEnd(new EventDateTime().setDateTime(end));
System.out.println(end.toStringRfc3339());
Event createdEvent = client.events().insert("primary", event).execute();
System.out.println("event id" + createdEvent.getId());
}
}