Sun Microsystem is releasing weekly early access snapshots of the complete source, binaries and documentation for JDK 7. These snapshot releases let you review and contribute to the Java SE platform as it is being developed.
You can read the API documentation @ http://download.java.net/jdk7/docs/api/
Three primary elements that offer new input/output (I/O) APIs for the Java platform are:
1. An extensive File I/O API system addresses feature requests that developers have sought since the inception of the JDK.
2. A socket channel API addresses multicasting, socket binding associated with channels, and related issues.
3. An asynchronous I/O API enables mapping to I/O facilities, completion ports, and various I/O event port mechanisms to enhance scalability.
You can download JDK 7 @ https://jdk7.dev.java.net/