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Applets<br />
--<br />
Mickey Segal<br />
Q: Why do I get message like “wrong magic number” when I am trying to run applet? What is a<br />
magic number?<br />
Answer: The first thing a JVM does when it loads a class is check that the first four bytes are (in hex)<br />
CA FE BA BE. This is the "magic number" and thats why you are getting that error, you are trying to<br />
load a file that isnt a class and so the class loader in the JVM is throwing out that exception.<br />
Make sure you transfer the class files to site in binary mode, rather than text or ASCII mode.<br />
An error from the browser saying "cannot start applet ... bad magic number" usually means that one of<br />
the class files on the server is corrupted. '<br />
Replace your class binary files on the web server; clean up the cache of your browser, and reload<br />
your applet.<br />
Q: I want to use more fonts in my applet... say for example Arial... which is not avilable in the<br />
present jdk package...<br />
How can i deal with it?<br />
Answer: import java.awt.Toolkit;<br />
....<br />
Toolkit tools : new Toolkit();<br />
String[] fontList = tools.getFontList();<br />
Q: How can I slow down my applet?<br />
I have a game applet that is running too fast on newer systems that have high-end video cards. Its<br />
easy enough to slow down the game by having it sleep between thread cycles, but I need to be able<br />
to<br />
determine how fast a users machine is before I determine how long to sleep for.<br />
I have been muddling through the documentation but cannot find any calls that will tell my applet what<br />
the users configuration is as regards to CPU speed and other components they may have on their<br />
system.<br />
Answer: Simple create a new Date (), then perform a standard lengthy operation on the order of<br />
something that takes about one second on your machine, like a long loop, then create another new<br />
Date() and compare it to the first. If it takes 1/2 of the time compared to your machine, then the CPU<br />
is probably about 2 times faster. if it takes 3 times the duration compared to your machine, the CPU is<br />
probably 1/3 as fast as yours.<br />
Do this dynamically, and it might help with speed changes when there's lots of action happening as<br />
well - unless this issue is already being dealt with using threads, that is.<br />
-by<br />
Max Polk<br />
Q: Why do I see applet in applet viewer and do not in a browser?<br />
When I try to view my applet on a web page i get the error<br />
java.lang.NoSuchMethodError: java/lang/Double: method<br />
parseDouble(Ljava/lang/String;)D not found<br />
Which is weird as it compiles fine on Borland and with the JDK using applet viewer<br />
file:///F|/350_t/350_tips/applets.htm (4 of 10) [2002-02-27 21:17:49]
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