API v. Java

The Java API is a collection of standard classes that implement many of the useful objects you will encounter during Java programming. Many of the Java API classes implement native methods. Native methods are methods that are implemented in a language native to the machine. For example, most of the classes that allow you to construct GUIs are implemented natively.

It's important to recognize that much of what can be done in Java is independent of the API. That is, a great many things can be accomplished without it, and for that matter, one could completely reimplement only the parts of the API you need if the existing API doesn't suit your needs.

The complete API reference is available at http://java.sun.com/JDK-1.0/api/packages.html