CodeHelp - glossary J

CodeHelp contains the following Java related pages:

• Best Java sites on the web
• Java applet demonstration 1
• Java applet demonstration 2
• Non-Java applet code
• Java applet code
• The source code books available through CodeHelp contain essential information on programming in Java.

If you are considering learning Java, you should remember that it is an interpreted programming langauge - unlike HTML, CSS and Javascript, Java source code cannot simply be executed from the text file. A compiler program is required (java.exe) along with all associated class libraries. This can be a significant download and it may be easier to purchase a book on Java that includes the language files and the compiler with library files on a CD-ROM. Try Java Programming for Dummies which includes a CD-ROM of Java 2 (actually Java v1.2). Also, remember that Microsoft Visual J++ does not adhere strictly to the same rules as the original Java. This may be fixed with newer versions, but beware that Java code from Visual J++ could be tailored for the Windows environment. This could cause problems if you are creating non-applet code that could be downloaded onto other platforms like Unix or Mac.

Advantages of Java

• Platform independent applets
• Client-side operation means no burden on the server
• Your code is protected because only the compiled applet is downloaded, not the code

Disadvantages of Java

• Compared to Javascript, download and execution is slow
• Many of tasks that Java is best at have been superceded by animated GIF files and other technologies.
• Other technologies do not require a compiler and can be created without the author having to learn a new programming language, leading to faster development.

My previous site used a Java applet as the navigation bar with the advantage that the technology could not be installed on someone else's site - the Java applet was programmed to only accept links to my own webspace. If you want to protect your code and you are prepared to learn a new language, Java could be useful in creating utilities like calculators, spreadsheets, audio and text effects, games like asteroids and hangman, along with biorhythym charts, daily quotes etc.
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Javascript gives you the power to activate your web pages by embedding an object-based scripting language directly into the HTML. Create interactive web pages, activate graphics, verify form details, many sites can use Javascript to eliminate the need for Java applets altogether.

However, Javascript is not like Java, despite the misleading name. Javascript code is an integral part of the HTML document and as such is downloaded as plain text. Anyone with a web browser can download all your carefully written Javascript code and adapt it for their own site. This is how most web designers (including me) learnt Javascript in the first place. Find a page that already runs Javascript, view it, copy the file out of the browser cache, edit with a simple program like Notepad and experiment with the code until it's understandable. CodeHelp contains detailed help on using Javascript and which version to use when. CodeHelp reuses the same code, so it's stored in one external file linked to many HTML pages. To view the Javascript code used by CodeHelp in getting you this far, look for the .js files in your browser cache.

• Flavours and versions.
• Identifying a browser.
• Redirecting a browser.

To use a Javascript function from an HTML link use the syntax
<a href= "javascript:FUNCTION_NAME();"> LINK_TEXT</a>.
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Use JPEG files for high quality, high colour images like photographs. The JPEG format compresses the image by throwing out superfluous data, leaving an image that when viewed on a computer monitor is indistinguishable from the original file. This results in a file 10 to 20 times smaller than the original. JPEG images require more processing power to display and despite the compression, are used for larger files so have become associated with lengthy downloads compared to GIF's. See Web Design in a Nutshell by Niederst for more information of when to use which format.
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