Please read the following before sending me e-mail. The following questions come up frequently. I cannot guarantee that your email will get an answer... sorry... I'm a busy guy.
1. Are these applets free?
The compiled applets listed on the download page are free for use on personal or commercial webpages. You may use the '.class' files to implement the applets on your own pages (and customize them according to the parameters). Note that while the applets are free for personal or commercial use, if you or your company feel inclined to do so, you are welcome to reimburse me for prominent use of my applets. Contact me about this and we can discuss appropriate fees. Also note that in some of the demonstrations of my applets I use images which have copyrights held by separate entities. If you use the applets for yourself (especially for commercial purposes, you should replace such images with restriction free material.
2. How do I embed an applet into a webpage?
In the actual HTML of the webpage you must include a set of <applet></applet> tag. You can look at the source of the description page to see a basic example. The applet tag MUST include attributes for code= (which points to the main applet class file -- ending in ____ech.class), width=, height=. Other attributes are optional, including:
- align=
- alt=
- codebase= Use this tag ONLY if you want to put the '.class' files in a directory other than that which houses the webpage. This value should indicate the directory path to whatever folder you want to hold the '.class' files.
- archive= You may, if you want, archive all the '.class' files into a single '.zip' or .'jar' file in an attempt to speed up the applet's download for users. This is NOT NECESSARY, though, and if you do not want to fool with it, LEAVE THIS ATTRIBUTE OUT of the HTML code. More information about the '.jar' format may be found at Sun Microsystem's Java pages.
Between the basic applet tags, you will want to include various
tags so that the applet can be customized for your pages with your own images or sound files or whatever.
Many of the parameter tags let you refernce image files or sound files that are also on your web server. If you don't want to include a particular image or sound in your implementation of an applet, OMIT the parameter completely. Any directory paths specified in image/sound parameters are assumed to either be complete URL addresses or directory paths relative to the directory holding the webpage (not necessarily the same directory holding the '.class' files).
3. Do you write/code JavaScript?
No. For those who do not realize it: Java and JavaScript are two very different things (despite their horribly similar names). I do not do any professional work in JavaScript, only Java. Furthermore, if you use applets on your webpages, you should tell visitors that they need a Java enabled browser (not a JavaScript enabled browser).
4. Hey!... I just downloaded one of your applets and it's not working correctly. Can you take a look at my page, and the HTML code and see what I'm doing wrong?
Sorry... I don't really have time to look at HTML source of pages into which you are trying to add an applet. I have tested the applets on the latest versions of both Netscape and Internet Explorer, and they all function properly unless otherwise noted. Here are some things you can quickly doublecheck:
- Check your double-quotes (") around parameter vales containing whitespace.
- Be sure you have all the necessary '.class' files as listed on the description page for the individual applet.
- Also, watch for 'Case Sensitivity'; meaning that if any of the '.class' files have Capital letters in them, then so should yours that you download (and lowercase letters should match also).
- Finally, if you are transferring the '.class' files around using an FTP program, be sure it is BINARY and not ASCII mode during the transfers
5. I'm trying to use one of your applets, but I keep getting 'this or that' error message... what's wrong? Besides the problems listed above, there are so many things that could possibly be wrong, I won't try to write a complete list, but here are a few common Error/Exception messages people keep asking about, none of which has anything to do with a problem in the applet itself:
- ClassFormatError/NoClassDefFoundError: This often means that the applet is not being found/loaded by the browser. If you do not use the codebase= attribute in your <APPLET> tag, then the .class files MUST reside in the same working directory as your HTML page. The codebase= attribute may be used to specify a different directory. Also, if your HTML page has a <BASE> tag in it... this may confuse the applet as to where the .class files are. Also, if you copy the example code directly from my webpages, you will have to either modify or delete the existing 'codebase' and 'archive' tags.
- Be sure that you have downloaded all classes necessary for the particular applet, and that they all reside in the correct directory. Some applets require more than one .class file (if multiple are needed, they will be listed on the applet description page).
-
NullPointerException: A 'null pointer' means that the applet is trying to manipulate something that should (but does not) exist... it is 'null'. This often occurs if Parameters in the HTML document are directing the applet to a sound or image file which does not exist, or exists in a directory different than that specified. DOUBLE/TRIPLE CHECK your image and sound file paths! And if are not wanting to use a sound/image in an applet, don't reference it with a param-tag.
-
java.lang.IllegalArgumentException: An error of this type probably means that the applet was expecting a numerical value of some sort and found something else (this could include accidently putting a '+' in from of a positive number, or using a decimel point in an expected integer value).
Web browsers generally have a 'Java Console' window which spits out messages of greater length than the one-line status bar at the bottom of the browser. This console may give you a little more insight as to what type of error is going on.
6. Hey!...I'm just learning Java. Can you give me help?
See above. I'm happy that so many people are interested in Java and that they want to ask me general programming questions, but again, I have enough trouble keeping up with my own projects. If you are interested in learning more about Java programming, I suggest you take a look at the homepage for Javasoft at Sun Microsystems.
7. Is the source code available for the applets?
No, not currently.
8. What type of sound file formats can I use for the applets?
Java v1.0.2 only supports the 'voice format' of the .au sound files. This is also know as 'µ-law, 8-bit, mono, 8000hz sample rate' aka... the lowest possible quality of sound. Multimedia flexibility is being worked on for the next Java release by Javasoft.
9. What type of image file formats can I use for the applets?
You may use GIF or JPG images with applets. I would be wary of using Animated GIFs or interlaced/progressive GIFs/JPGs.
10. Can I use transparent GIFs in an applet?
Yes, but it will not allow you to see the background of your webpage housing the applet. Web browsers allocate an area of the web page for the applet... and this area is forced to be light gray in color (usually). So, if you use a transparent GIF in your applet, you will simply see back to the gray background. Most of the applets at The Applet Depot; have some sort of parameter to allow you to pick a background color for the applet (parameter BGCOLOR, usually). Some even let you load in a background image (which can be matched, somewhat, to the web page's background).
11. What about the sound/picture files that you use in your examples... can I use them also?
You should be able to access any sound files and images files with your web browser (if you point the browser directly at those files). You are welcome to use and of the sounds or images (note that many of the images in the examples I provide are not mine, so I hold no claim to their respective copyrights; I am only using them for demonstration purposes).
12. What type of fonts can I use for the applets?
Java v1.0.2 is limited in its font choices. To be safe with cross-platform names stick with one of the following (exactly as named): TimesRoman, Courier, Dialog, DialogInput, Helvetica. Font size can be just about any positive integer, but certain browsers don't support values greater than 36. The font style may be either: 'plain', 'bold', 'italic', or 'bolditalic'.
13. May I make suggestions about future revisions to an applet?
Go for it. I am always willing to hear new ideas. I cannot guarantee the suggestion will be implemented, but I will consider it.
14. What is the schedule for applet updates?
Schedule?.. what?... hehehe... yeah... right.
15. What development tools do you use to write/program Java?
I use the standard compiler that comes with Sun Microsystems' Java Development Kit (JDK), and whatever simple text editor is available on the OS platform (usually 'Notepad' on Windows or 'vi' on Unix).
If your questions are still not answered, feel free to email me. |
