Google Contacts API for Java Desktop Application

After hours of using google to find anything helpful I want to ask some experts...

I want to write a Java Desktop Application - nothing special, only simple Java SE without any servers, mobile apps... For this I want to access the contacts in my Google account: read all contacts and add some new ones.

I've read many of the doc pages and I got nothing working. I also have a problem with OAuth 2.0, although I only want to access my Data - so there is no problem to store my user credentials in my application.

So, can you tell me, which libraries I have to include, which method of which class I have to call? Or is there anywhere a small working example I could use?

Thank you