Frequently Asked Questions

Note: The FAQ will be updated with your questions.
So ask questions rvdb@nedernet.nl

Questions

1:When I try to start an applet on my local system I get a
com.ms.applet.AppletSecurityExeption: Couldn't connect with the origin from the file
ANSWER

2:The applet works fine when I start it localy.
But it doesn't work or when I start it from the net.
I get something like :
load: class xxxx.xxx not found.
ANSWER

3:The mouse isn't a pointing hand but a cross or an up arrow.
ANSWER

4:The applet doesn't display my images the right way.
It dithers the pictures
I'm using an Netscape browser.
ANSWER

5:The applet doesn't display transparent images the right way.
ANSWER

6:After I uploaded the applet to my server I get an
java.lang.ClassFormatError
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Answers

Answer 1:
When you try to start an applet on the local system with
the Ms Explorer 3.01, 3.02 or 4.0 you can get an AppletSecurity exception.
Java runs within a virtual machine within the browser.
Microsoft made a very rigid security ristriction on applets.
There where many complains abouth this restriction.
There is a fix for this on the Microsoft site.
http://www.microsoft.com/java/dl_vmsp2.htm
Note: that this download only works if you haven't start an applet. So close the Ms Explorer and restart it at this url. This download is a new Virtual Machine that is build in top of the old one. BACK














































Answer 2:
This is mostly caused by a wrong filename 
or lettercassing.
Java is case sensitive.
Each file in Windows95 has two names.
A short Windows 3.1x filename and a 
long Windows95 filename.
A Windows 3.1x or Dos FTP(=File Transfere Protocol) program
uses the short filename.
When uploading the files to the providers computer these 
programs use the short filenames.
Solution download a Windows95 FTP program.
This can be found at HTTP://www.windows95.com
I myself use the WS FTP.
Also some Windows NT FTP programs change the lettercassing
to small cassing.

It is also possible you tried to change the place of the 
class file with the CODE attribute.
Te code attribute of the applet tag only tells the 
browser the filename.
If you want to change the place use the CODEBASE attribute.
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Answer 3:
There is a BUG in Java on the Windows95 system.
Java can't acces the pointing hand on a Windows95 system.
I can change the applet so there will be an pointing hand on 
non Windows95 systems.
If you want such an change email me.
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Answer 4:
Netscapes Java virtual machine dithers gif files to 
a 125 color pallete.

Solution 1:
Convert your gif file to jpg.
Netscape doesn't dither jpg files.
Explorer does display jpg and gif files without dithering.

Solution 2:
Convert the pictures to the 125color pallete.
Netscape RGB color pallete is a combination of the following 
color values : 0,64,128,192,255.
This is not very usefull for photo like images.

This is not simple thing to do !
I can send you an applet that converts a picture to the 
125 color pallete.
(This applet will not work on a Macintosh)
But you will have to take a screenshot to get the picture
back to the gif format.
Also you can use a program like Coral Photo paint for it
but many things you still have to do manualy.

Solution 3:
You also can change Netscape preferences:
Look at : general preferences, Images.
 
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Answer 5:
There are some problems with transparent Images on the Netscape browser
and the Explorer.

Note:
The background color of the applet is usualy gray.
It doesn't has to be the same as the html page.

Cause of the problem offscreen images.
Offscreen images are used to reduce drawing time and flickering.

Solution: 
Use non transparent gif files and convert the transparancy color
to the background color you want.

Netscape:
Doesn't support transparency on offscreen images.
The offscreenImages are displayed but whithout transparency.

Explorer:
Does support transparency on offscreen images.
But explorer handles offscreen images different than normal images.
With offscreen images explorer doesn't draw the transparent pixels.
With normal transparent images explorer displays the 
background color of the applet.

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Answer 6:
You probably uploaded the *.class file as an ASCII (=text) file.
If you upload *.class files as ASCII they will get corrupted.
Class files are binary files.

Solution:
Set your FTP (=File Transvere Program) to binary mode.
Then try it again.

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