The library is very easy to use, first make sure you have all the required jars in the classpath then have a look at the sample source bellow.
public void printContacts() {
// Setup session and contact manager
String username = "<gmail username or email address>";
String password = "<gmail password>";
GMSession session = new GMSession(username, password);
GMContactManager manager = new GMContactManager(session);
// Retrieve all contacts and do some processing on each contact
GMContact[] contacts = manager.getAllGMContacts();
for (int i = 0; i < contacts.length; i++) {
// Do some fancy stuff here
}
// Add a new contact
GMContact contact = new GMContact(
"TEST TESTINGSSON",
"test.testingsson@testnet.com",
"Test comment");
contact = manager.addGMContact(contact);
// Update contact
contact.setNote("A new note.");
manager.updateGMContact(contact);
// Remove contact.
manager.removeGMContact(contact);
// End session.
manager = null;
session.logout();
session = null;
}