The first two lessons in this trail discussed all of the applet-specific API. However, most applets rely on a lot of API that isn't specific to applets. This lesson gives you hints about using the Java API, covering the areas that are affected by applets' close relationships with browsers.
Security Restrictions lists the security restrictions that untrusted applets face. It also describes some ways to get around the restrictions.
Creating a User Interface discusses the elements of an applet's UI. It then goes on to give hints for creating a GUI and creating debugging output using the standard output and standard error streams.
Getting System Properties discusses the system properties that an applet can get to find out about its environment. It includes an example applet that displays the ten properties applets can get. It also lists some properties that applets typically can't get.
Threads in Applets delves deeply into the issues of using threads in applets. A thread -- sometimes called an execution context or a lightweight process -- is a single sequential flow of control within a process. Even the simplest applets run in multiple threads, although it's not always apparent. Many applets create and use their own threads so that they perform well without affecting the performance of the browser they run in or the performance of other applets.
Working with a Server-Side Application shows how even untrusted applets can use networking code to communicate with programs running on the host from which they came.