Java documentation

Packages / Interfaces / Enumerations and Classes

http://www.j2ee.me/javase/6/docs/api/index-files/index-1.html

http://www.j2ee.me/javase/6/docs/api/java/util/package-summary.html

or

http://java.sun.com/javase/6/docs/api/index-files/index-1.html

Structure

http://java.sun.com/javase/6/docs/

APIs

http://java.sun.com/javase/6/docs/api/overview-summary.html