Teach Yourself SunSoft Java WorkShop in 21 Days

Questions and Answers

Download and Installation Problems

• Question: I installed Java workshop on my computer succesfully, but when I open it, it says, "This program has made an illegal operation." I checked details, and it said "Invalid Pagefault in Kernal32.dll". I did have a previous version of JDK on my computer, but I deleted it and changed back my Autoexec.bat file. What should I do? -- J.

  Answer: This is not a problem that I have encountered, and a look through Sun's Java site doesn't offer anything specific either.

  It probably is happening because a previous version of the Java Developer's Kit or Java WorkShop was not fully deinstalled from your system. Make sure to deinstall all other Java development software, removing references to them in your AUTOEXEC.BAT and CONFIG.SYS files. When that's done, reinstall Java WorkShop.

  A patch has been made available fixing some of the bugs in the 1.0 release of Java WorkShop. You might also download and install that patch to see if it fixes your installation problem.

Programming Problems

• Question: The ColorTest applet written on Day 13 seems to bring up a problem when run under Netscape Navigator 3.0 as follows: "Applet can't start: class ColorTest got a security violation: method verification error".

  The applet works correctly in Java Workshop v 1.0 patch release A.

  The error in Internet explorer is: "error: java.lang.NoClassDefFoundError : ColorControls" This also happens after copying the class from the CD. What would fix this? -- D.D.
  

  Answer: I think this is occurring because the ColorControls.class file has not been put in the same directory as the HTML page containing the file.

  The ColorTest applet includes two class files: ColorTest.class and ColorControls.class. Make sure both are where they should be and that ought to fix the problem.

   

• Question: I am thoroughly enjoying your Java WorkShop book; however I have a question. On Day 13 when I build the Guesser program using the Visual interface, everything works just fine in the Workshop tester mode. But when I try to run it in Netscape or in Explorer I get a security violation. (And this is right on my own desktop!) Any ideas? -- J.M.
  

  Answer: The Visual Java feature of Java WorkShop uses classes that are not part of the standard Java language. To offer an applet that uses Visual Java, you have to put extra class files in the same directory as the applet's class file (or files).

  Find the jws/visual/rt directory and copy all of its classes and subdirectories into the directory where your applet files are located. This will enable your applet to find the Visual Java classes that are needed, and Sun permits this use of WorkShop.