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Beginner's Guide to JDK

Issue 55

From Issue #55
November 1998

Nov 01, 1998  By Gordon Chamberlin
 in
This article covers the use of the Java Development Kit on a Linux platform. It includes a general introduction to Java, installing the JDK 1.1.6, compiling Java support into the Linux kernel, writing a simple Java program and studying an example.
Running the Demos

JDK includes many examples in addition to the applets and applications. Change the current path to /usr/local/jdk1.1.3/demo/ and you will see the numerous directories containing examples in this directory. Some of the examples include Tic-Tac-Toe, a graphics test and a molecule viewer.

To run Tic-Tac-Toe, use your web browser to open the file /usr/local/jdk1.1.6/demo/TicTacToe/example1.html.

The graphics test is located in jdk1.1.6/demo/GraphicsTest/. It is noteworthy for having been written to be executed as both an application and an applet.

The molecule viewer is an applet located in jdk1.1.6/demo/MoleculeViewer/. I mention it just because it is cool—it shows off the power of Java.

The Possibilities: Real Time Linux Statistics

The company I work for, Visualize, Inc. (http://www.visualizetech.com/), specializes in high-end data-graphing software also known as data visualization. Our products all derive from our core library called VantagePoint. VantagePoint is 100% Pure Java certified. Writing our products in Java allows us to develop the software once, then run it on any platform for which Java has been ported. In practice, our customers have encountered few problems with the products as a cross-platform software package. In fact, the earliest version of VantagePoint was developed completely on Linux. Linux still plays an important role in our company.

VantagePoint products, as a graphing solution, view the world as data sets. The possible operations on a data set are graphing, loading and analyzing. After an analysis has been performed on a data set, it is possible to do any of these operations again. A useful sequence of operations is opening and loading a data set, graphing the data to get a visual representation, analyzing the data and then graphing the result of the analysis.

One VantagePoint product, DP Server, is a manager for any data sets you may have. It also allows connections from applets running in a web browser on either an Intranet or the Internet.

Figure 1: Real-Time Linux CPU Usage Statistics

Now, go to the page at http://www.visualizetech.com/lj/. Follow the link to “Linux Statistics”. This page, which looks like Figure 1, starts a Java applet that connects to a DataPoint Server to show a two-dimensional line chart. It is updated regularly with each update showing the current CPU usage on the Linux web server. During this particular snapshot, the Linux box had just finished compiling the HelloLinux.java program.

Conclusion

Java is a boon to the software development industry. Java and Linux offer the best combination the computer industry has to offer: a free, dependable operating system and a platform-independent software language.

Acknowledgements

Gordon Chamberlin is a programmer and system administrator for Visualize, Inc., in Phoenix, AZ. He was introduced to Linux at 1.2.x and quickly bought a 486 to be able to use Linux at home. He enjoys playing computer games, especially Descent II and spending time with his wife, Barbara. Please send comments, questions or jokes to glac@visualizetech.com.

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