Welcome to the Java 101 study guide. This guide complements "Trash Talk, Part 2." It provides a glossary of terms specific to that article, new homework, solutions to last month's homework, and Jeff Friesen's answers to questions from your fellow students. The Java 101 study guides are evolving documents -- they change periodically. For example, if you submit a question long after Jeff posts the relevant study guide, your question and his answer will eventually make its way onto that guide. Furthermore, from time to time, he will post additional examples and other material that clarifies an article's topic, so be sure to revisit the study guides periodically.
This month, Jeff Friesen explores the Reference Objects API, an API that allows your programs to interact with the garbage collector in limited ways. He shows you how to use that API to manage image caches, obtain notification when significant objects are no longer strongly reachable, and perform post-finalization cleanup. For answers to last month's homework, for this month's homework, and for additional material related to this article, visit the associated study guide. (3,700 words; January 4, 2002)
5. Pick up performance with generational garbage collection
With generational garbage collection (introduced in Sun Microsystems's Java HotSpot VM for Solaris), command line parameters control how the JVM uses heap space to perform garbage collection. The default parameters are effective for most small applications that require faster startup and a smaller footprint. By selecting parameters that activate the Java HotSpot Server VM, you can improve the throughput of large, server-side applications by 20 percent or more. This article explains how the HotSpot JVM uses system resources to provide significant throughput improvement with no code modifications. (4,200 words; January 11, 2002)
6. Interact with garbage collector to avoid memory leaks
In model-view-controller (MVC) applications, models often accumulate references to unused view objects. These references prevent the view objects from being garbage-collected, even after the user disposes of views that can no longer be used. This tip shows you how to implement your own models to remove unneeded listeners automatically, thus preventing memory leaks. A simple application is included to demonstrate the problem and solution. (1,800 words)
