The Java Developer's Kit
Although the details of programming and developing Java applications and applets are beyond the scope of this article, we will briefly cover how to go about compiling and running Java applications and applets. Java source code is saved in files with the .java extension. Once compiled, a class file (with a .class extension) will be created. Assuming the java/bin directory is in your path as outlined above, a Java source file can be compiled with:
Class files for applications can be executed using:
Applets are a little more complicated. Applets are run as embedded pieces of web pages and are included in web pages with a special <APPLET> tag. You can test an embedded applet with appletviewer or Netscape Navigator 2.0 or 3.0. With Navigator, simply choose Open from the File menu and then open the HTML file with the embedded applet.
With appletviewer, simply type:
Running applets as well as some Java applications requires that you are working in an X-Windows environment. If you don't have X-Windows installed on your system you won't be able to test applets or any applications which make use of Java's GUI development capabilities.
On most Linux systems the steps outlined above should be all that is required to get the JDK up and running. However, on some systems you may experience some difficulty; some of the common errors and their solutions are outlined below:
You get an error message referring to /dev/zero. The device /dev/zero needs to have world read and write permissions. Set these permissions using:
chmod 666 /dev/zero
You get “dirname: too many arguments” or “cannot find class” errors. The component you are trying to run cannot find the native Java class files. The JDK uses the environment variable CLASSPATH to find these files. This variable is set in java/bin/.java_wrapper and java/bin/appletviewer. However, with your shell, these scripts are having trouble determining the correct directory. You can edit these files so that the CLASSPATH gets set correctly.
In .java_wrapper, change the line which reads:
(or wherever you installed the JDK) A similar change needs to be made in appletviewer.
Once you have installed the Java Developer's Kit, you will probably want more information about developing Java applications and applets. Aside from Sun's official Java home page at http://www.javasoft.com/, the Gamelan directory (http://www.gamelan.com/) provides an extensive collection of applets and applications—many with source code—as well as pointers to other reference material. The comp.lang.java newsgroup is a high-volume newsgroup which is actively used by many Java experts and novice programmers.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide