To help you navigate the new changes in JDK 9, the new functionalities can be organized into six categories. Those categories will help you understand which features are new, which require you to change your code or process, which come as default with JDK 9, which are improved APIs and which will be removed. The new features are available in JDK 9 early access. You can download and test today the features in JDK 9 early access
The categories are more clearly defined as:
The full list of features is available on the JDK 9 website. I am listing below some libraries that you, as a developer, might want to learn more about. See the graph at the bottom of the page.
Behind the scene