GUI Development with Java
But isn't Java proprietary? Well, although Sun invented Java and many of the pieces of technology that accompany it, it can be called an “open” technology. Old-timers will remember how Sun dominated the UNIX distributed file system by making its NFS a public specification, even giving away the source for the RPC and XDR layers that underlie NFS. From the beginning, the specification of the Java language and the specification and format of the compiled class files have been publicly available and the source code of the public API has been included with the freely-downloadable JDK. The source for everything—compiler, runtime interpreter and the internal parts of the API—has been available for free under a non-disclosure agreement that permits free redistribution of binaries. Without this, there would most likely not be a Java for Linux, SunOS4.1 or *BSD. In fact, there are several: JDK ports, Kaffe ports and others. Further, the licensing is designed to encourage the “open API” concept. Read this extract from Clause 2 of the JDK license, which every Java developer who uses Sun's JDK or any derivative must agree to:
In the event that Licensee creates any Java-related API and distributes such API to others for applet or application development, Licensee must promptly publish an accurate specification for such API for free use by all developers of Java-based software.
Because of this, members of the free software community have responded as enthusiastically to Java as they did to Linux. Several free compilers, at least one free interpreter and many free libraries are available. Even commercial companies are making some libraries free. A good place to explore Java freeware (and payware) is Gamelan (pronounced Gamma-LOHN), at http://www.developer.com/. My own contributions include Jabadex, a Rolodex-like application, a set of X Color names (Java's AWT has only 13 named colors) and others (see http://www.darwinsys.com/freeware/).
Most recently, Sun announced easier licensing—the Sun Community Source License—presumably patterned after the Mozilla license. It's not the BSD Copyright or the GPL, but it's a step closer. See http:java.sun.com/ and look for licensing.
Java's developers wanted everything about Java to be portable, including how to deal with the X Window System, MS Windows, Macintosh and other window systems. The Abstract Window Toolkit is the solution they provide. Instead of starting by writing components that work everywhere, they wrote a library of GUI components that is a least common denominator to what the big three systems offer. It used the underlying native components on each platform, so that it would “look and feel” like a native application. This is an important aspect of user acceptance—if users have to learn a whole new GUI just to use your software, they probably won't bother. This approach limited what you could do with the early versions of Java's AWT, but with more recent versions, this is no longer true. The JFC components bring Java to the forefront of fully functional GUI development environments.
Java has been increasing in popularity since its first public release in 1995. Version 1.0 incorporated the Applet API, a basic window toolkit (AWT) and numerous other APIs. Version 1.1, released in the fall of 1996, added a tremendous amount of new functionality including internationalization, better coupling between GUI controls and their action-handling code, text formatting and hundreds of new classes. JDK1.2 has just been released at the time of this writing (January 1999). Version 1.2 of the JDK, which is also being called “Java 2”, includes the Java Foundation Classes (JFC). JFC includes the Swing GUI classes which are the focus of this article, some accessibility features to make computing usage easier for persons with various disadvantages, the 2-D graphics package and the original AWT.
The 2-D graphics can be thought of as PostScript for Java. If you've done any PostScript, you'll know it is really two things: a scripting language and a marking engine. Since Java already provides a powerful programming language, the 2-D developers needed to provide only the “marking engine” (putting marks on paper), transforms, composites and other fancy graphics and a much-expanded set of fonts. However, it is implemented in a backward-compatible way: a Graphics2D object is subclassed from a Graphics object. This provides Java developers and users with all the fancy graphics capabilities invented over a decade of desktop publishing, all in a platform-independent way.
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