Home | Contact Us | FAQ | Search & Site Map | Link to Us
Sign In | Join | Other 45 Sites in Network
HomeAnnouncementsWhite Papers
Discussion GroupsFirst AidDatabasesJavaBeansGUIJava 3DVirtual MachineCORBASecurityToolsGeneral
Java DirectoryOpen Source ProjectsSample Book ChaptersUser GroupsWeb Resources
Related Topics
Databases.NETMore Topics ...
Java Forum / General / January 2006

Tip: Looking for answers? Try searching our database.

Java 1.6 Heisenbug  involving startsWith

Thread view: 
Enable EMail AlertsStart New Thread
Roedy Green - 28 Jan 2006 00:05 GMT
I have an Applet that works fine in earlier JDKs but is failing in
1.6.

Code like this

public class StartsWithBug
  {
  /**
   * test startsWith optimisation bug
   *
   * @param args a string possibly starting with snippets/
   */
  public static void main ( String[] args )
     {
     //
     String urlString = args[0];
     System.out.println( urlString );

     if ( !urlString.startsWith( "snippets/" ) )
        {
        urlString = "snippets/" + urlString;
        }
     System.out.println( urlString );
     }
  }

is failling to prepend the "snippets/" string.

Of coruse it works fine in this isolated snippet. I gather the hotspot
optimiser screws it up in some contexts.
Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message
hiwa - 28 Jan 2006 00:57 GMT
> Of coruse it works fine in this isolated snippet.
Could you reproduce the failing condition?
Reply to this Message
Roedy Green - 28 Jan 2006 09:03 GMT
>> Of coruse it works fine in this isolated snippet.
>Could you reproduce the failing condition?
I can't get it to fail myself. I have prepared a new version to help
track the problem, but for some reason Mickey, who can get it to fail,
has been getting an old version.
Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message
Mickey Segal - 28 Jan 2006 20:08 GMT
> I can't get it to fail myself. I have prepared a new version to help
> track the problem, but for some reason Mickey, who can get it to fail,
> has been getting an old version.

On a "virgin" computer that had never loaded the applet I don't get the
Exceptions.  However, on the original computer, despite clearing the browser
caches in Internet Explorer and Firefox and setting IE to reload the new
version of a page each time I still get the error messages, presumably
meaning I'm getting the old version.

I don't think this is due to some different Java setting on the two
computers because I had removed Java and installed the new Java 1.6 weekly
build yesterday on each machine.

Is there some separate way of clearing a Java-specific cache?  I don't see
such a command in the Sun Java Console.
Reply to this Message
Roedy Green - 28 Jan 2006 23:09 GMT
On Sat, 28 Jan 2006 15:08:51 -0500, "Mickey Segal"
<not_monitored@example.com> wrote, quoted or indirectly quoted someone
who said :

>On a "virgin" computer that had never loaded the applet I don't get the
>Exceptions.  However, on the original computer, despite clearing the browser
[quoted text clipped - 8 lines]
>Is there some separate way of clearing a Java-specific cache?  I don't see
>such a command in the Sun Java Console.

Try going into to Java console in control panel | settings and poking
around.

the old version still should not be getting exceptions. It is just the
new version dumps more information and does more internal checks to
help me track down why they are happening.

You might want to use Wassup to verify you are indeed using 1.6 on
both.  See http://mindprod.com/jgloss/wassup.html
Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message
Mickey Segal - 29 Jan 2006 17:35 GMT
> Try going into to Java console in control panel | settings and poking
> around.

In the Java Control Panel under the General tab there is a Temporary
Internet Files section.  This caches applets in a way that survives
uninstalling Java and re-installing.

When I delete the material on the original computer the 4 applets still do
not work.

However, I get different set of error messages so it looks like we are
making some progress.  I still can't explain why it doesn't work on the
original machine but it does work on the virgin machine.  There seem to be
no different settings on the Java Control Panels of the original and virgin
computers.
Reply to this Message
Roedy Green - 30 Jan 2006 04:22 GMT
On Sun, 29 Jan 2006 12:35:13 -0500, "Mickey Segal"
<not_monitored@example.com> wrote, quoted or indirectly quoted someone
who said :

>However, I get different set of error messages so it looks like we are
>making some progress.  

You have been emailing me data too.  It looks like what was happening
in you were originally accessing an very old copy of JDisplay in
cache. Now you have nuked that and it can't seem to find the new one.

I can see it fine with JDK 1.5 from my website.

Is suspect the problem may be related to the use of

<applet archive="../applets/jdisplay.jar"

I suspect JDK 1.6 has lost the ability to support ../

I would think this was the browser's problem, converting hat to an
absolute URL.  At least the browser has to inform Java of the url of
the current page so it can concoct an absolute URL for the jar. The
server knows nothing about ../

Then again maybe the server does support ../  Perhaps it sometimes can
figure out from a referring page URL.

I have to figure out a way to get one of my browsers using Java 1.6 so
I can packet sniff to see what the heck is going on.

If this bug in released on the world, it could cause havoc.  I would
like it nailed prior to release.

Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message
Mickey Segal - 30 Jan 2006 16:35 GMT
> If this bug in released on the world, it could cause havoc.  I
> would like it nailed prior to release.

What makes this hard to figure out is that a virgin computer with JRE 1.6
works fine, but the other does not.  This sounds like either some cache we
have not nailed, affecting both browsers, or some setting we have not found
(but all the Java Control Panel settings are the same).

It would be interesting to know whether other computers with JRE 1.6 have
problems, but clearly some work fine.

Regardless of the cause it would be good to know what is going on so these
problems don't occur for our users.
Reply to this Message
Roedy Green - 30 Jan 2006 22:10 GMT
On Mon, 30 Jan 2006 11:35:22 -0500, "Mickey Segal"
<not_monitored@example.com> wrote, quoted or indirectly quoted someone
who said :

>It would be interesting to know whether other computers with JRE 1.6 have
>problems, but clearly some work fine.

you might compare the policy files on both.  See
http://mindprod.com/jgloss/policy.html
Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message
Mickey Segal - 31 Jan 2006 02:56 GMT
> you might compare the policy files on both.  See
> http://mindprod.com/jgloss/policy.html

I looked at http://mindprod.com/jgloss/policyfile.html and found that the
policy files on both files were the same, the default versions created when
I installed the new Java 1.6 build on 27 January.  While looking around I
noticed that on the computer that was virgin to
http://mindprod.com/jgloss/properties.html there was a folder for JRE 1.5
even though it was uninstalled.  It had only one file, QTJava.zip, buried
deep in a nest of folders.  This got me wondering whether the supposedly
virgin computer was showing signs of experience with JRE 1.5.

I then uninstalled JRE 1.6 and JDK 1.6 from both computers, deleted the JRE
1.5 folder from the supposedly virgin computer, reinstalled JDK and JRE 1.6
from http://download.java.net/jdk6/binaries/, and now I get the 4 applets
failing on both machines.  It is not clear how the JRE 1.5 folder caused a
difference, but it seems that was the case.

The good part of this experiment is that we now have what seems to be a
reproducible way of eliciting the problem.  Following the procedure above
should demonstrate the problem.

The bad part of this experiment is that it shows how hard it is to know the
state of Java on a user's computer.
Reply to this Message
Roedy Green - 31 Jan 2006 04:42 GMT
On Mon, 30 Jan 2006 21:56:58 -0500, "Mickey Segal"
<not_monitored@example.com> wrote, quoted or indirectly quoted someone
who said :

>The bad part of this experiment is that it shows how hard it is to know the
>state of Java on a user's computer.

Ok what about OTHER applets? Is it just JDisplay that fails?

What about say
http://mindprod.com/applets/converter.html
http://mindprod.com/jgloss/mime.html
http://mindprod.com/applets/wassup.html
one of the Sun test applet you can get to via
http://mindprod.com/jgloss/swing.html
Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message
Mickey Segal - 31 Jan 2006 13:22 GMT
> Ok what about OTHER applets? Is it just JDisplay that fails?

I haven't looked at the pages in detail to see which parts use applets, but
here is what fails on each page:

On http://mindprod.com/jgloss/properties.html the 4 applets with the
following text before them fail and all other content works:
1.  For Applets, there is a similar PARAM mechanism that generates a
properties table.
2.  Look at any *.properties files file to see an example. It will look
something like this example
3.  You could access a property in a sample.properties file like this:
4.  Beware, unused properties will return null, not the default.

> What about say
> http://mindprod.com/applets/converter.html
The top left applet fails.

> http://mindprod.com/jgloss/mime.html
The top applet fails.

> http://mindprod.com/applets/wassup.html
The applet fails.

> one of the Sun test applet you can get to via
> http://mindprod.com/jgloss/swing.html
This page works fine.
Reply to this Message
Roedy Green - 31 Jan 2006 14:10 GMT
On Tue, 31 Jan 2006 08:22:46 -0500, "Mickey Segal"
<not_monitored@example.com> wrote, quoted or indirectly quoted someone
who said :

>> one of the Sun test applet you can get to via
>> http://mindprod.com/jgloss/swing.html
>This page works fine.

no I meant something like

Test your JRE browser's ability to run Applets in general by
running Sun's

http://java.sun.com/applets/archive/beta/LED/index.html

LED Sign demo.
 
Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message
Mickey Segal - 31 Jan 2006 14:30 GMT
> no I meant something like
>
[quoted text clipped - 4 lines]
>
> LED Sign demo.

This works fine, as do many other applets I seen.  The only failures I've
seen are the ones I indicated on the mindprod.com site.
Reply to this Message
Roedy Green - 31 Jan 2006 14:13 GMT
On Tue, 31 Jan 2006 08:22:46 -0500, "Mickey Segal"
<not_monitored@example.com> wrote, quoted or indirectly quoted someone
who said :

>> http://mindprod.com/applets/converter.html
>The top left applet fails.

So NO Applet at all works on my site. What is the console saying, same
thing about not being able to find the class?

I wonder if Sun has changed its  dot class convention.  On their site
they used .class in all the <applet tags, so so did I.

I will take the .class off one and see if that lets it work.

see if http://mindprod.com/jgloss/mime.html works.
Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message


Free Magazines

Get these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...

Oracle MagazineNetwork ComputingComputer WorldBio-IT WorldeWeekInformation WeekInfosecurity
 
Sign In
Join
My Latest Posts
My Monitored Threads
My Blog
My Photo Gallery
My Profile
My Homepage
Start New Thread
Enable EMail Alerts
Rate this Thread



©2008 Advenet LLC   Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.