A series of articles published in ;login:. To quote Rik Farrow from the first article:

"This . . . is not a beginning tutorial. It assumes that you know something about Java, while still covering some of the basics for getting started. I suggest Exploring Java (Niemeyer and Peck, O'Reilly and Associates), some of the other books mentioned in ;login: reviews, or the online documentation available from JavaSoft for getting started with Java. "

Using Java 1 by Rik Farrow. including the clock.java applet.

Using Java 2 by Rik Farrow. Networking and DateServer.

Using Java 3 by Rik Farrow. Threads

Using Java 4 by Rik Farrow. Java Beans and Events

Using Java 5 by Rik Farrow. WebWalker

Using Java 6 by Rik Farrow. Layout Managers

Using Java 7 by Terry Slattery. Test TCP

Using Java 8 by Philippe Kaplan. Debugging in Java

Using Java 9 by Rik Farrow. Java Beans

Using Java 10 by Mark Sienkiewicz. Portability

Using Java 11 by Prithvi Rao. Using Beans within ActiveX

Using Java 12 by Prithvi Rao. Is Java Secure?

Using Java 13 by Prithvi Rao. Java RMI, CORBA or COM?

Using Java 14 by Prithvi Rao. Security Outside the JVM

Using Java 15 by Prithvi Rao. The Java Native Interface

Using Java 16 by Prithvi Rao. Applets and Animation

Using Java 17 by Prithvi Rao. Remote Method Invocation

Using Java 18 by Prithvi Rao. Input and Output Streams

Using Java 19 by Prithvi Rao. Using Threads Within Applets

Using Java 20 by Prithvi Rao. Threads Groups

Using Java 21 by Prithvi Rao. Java Collections

Using Java 22 by Prithvi Rao. Active Content in Java

Using Java 23 by Prithvi Rao. Life After Containers and Layout Managers: Part I

Using Java 24 by Prithvi Rao. Life After Containers and Layout Managers: Part II

Using Java 25 by Prithvi Rao. Enterprise Java Beans: An Overview

Using CORBA with Java by Prithvi Rao. A Mini Napster, Part 1