Note: Because the preceding applet uses the Java 2 SDK 1.2 API, it requires Java Plug-in 1.2. It won't work with Java Plug-in 1.1.1, or Java Plug-in 1.1.2, or uncustomized 1.1 browsers.And here are the sources: TreeApplet.java.
8. November 1999 Josef Willenborg