Applet Lifecycle

An applet begins its life when the web browser loads its classes and calls its init() method. Thus, in the init() method you should provide initialization code such as the initialization of variables. Once the initialization is complete, the web browser will call the start() method in the applet. At this point the user can begin interacting with the applet.
But what would happen if the user moved to another web page while the applet was executing? Well, if this happens, the web browser will call the applets stop() method so that the applet can take a breather while the user goes off and explores the web some more.
If the user returns to the applet, the web browser will simply call the applet's start() method again and the user will be back into the program.
Finally, if the user decides to quit the web browser, the web browser will free up system resources by killing the applet before it closes. To do so, it will call the applets destroy() method.
You are welcome to override any of the methods in order to provide your own logic. For example, you may want to provide logic in the stop() method which performs some cleanup or save operation.
Finally, you can override destroy() to perform one-time tasks upon program completion. One example is cleaning up threads which were started in the init() method.

Writing Applets
Table of Contents
Java Applet by Example