Gmail Task API exist?

Inside Gmail, there is a small function called "Task". It can allow me to enter a to-do-list. I'm wondering if there is any official / unofficial Google API to access / update the list by Java language?

Does Google Tasks have an API?

The Google Tasks API lets you search, read, and update Google Tasks content and metadata. This document describes how to use a RESTful calling style and client libraries for various programming languages (currently Java, Python, and PHP) to access and edit Google Tasks data.

Is there a task manager for Gmail?

Gmail includes a powerful task manager you can use to keep up with your tasks and create simple lists. Along with adding tasks to a list, you can make tasks sub-tasks (or dependents) of other tasks and set up multiple task lists to organize your activities.

The official Google Task API has been released in May 2011 (Well, it's in Labs, but it is official)

https://developers.google.com/google-apps/tasks/

Here are the Java specific libraries:

https://developers.google.com/api-client-library/java/