A Java Clock and Some Lossages

This page is part of a critique of EJBs, demonstrating that Java can be a bit of a moving target. Originally produced as a revision exercise in coding Java, the clock Applet demonstrates some lossages in older Java Virtual Machines (JVMs).

[If Java was running in your browser an analogue clock would appear here]

A Java Clock

We have all, one is sure, waded through books styled Power Java for the Very Stupid Made Easy with a CD or thereabouts. Satisfied that enough Java had been digested to get by, there was then a hiatus where no Java was written. Since some time has now elapsed, and we are all into Enterprise Java Beans (EJB) now this clock written as revision exercise. Initial attempts at compilation were marked by the Java Compiler whinging about "Deprecated features". So the Classes and methods were rewritten to use pure Java 1.1. The interesting thing about the clock is that it has shown up some lossages that can reasonably be expected from arbitrarily trying to run more modern Java programs on Browsers which might not be all that up to date. It should be noted that the latest Java is now 1.2 (also known as Java 2).

The clock might not be telling the time very accurately, the guts of the program is the Calendar class, which is relatively new in Java. Sadly therefore the following lossages have been observed:

Clock displays a random time:

The Browser's Java implementation is ancient and can't get the time from the operating system correctly.

Clock displays a random time (and doesn't update):

The Browser's Java implementation is ancient and has a broken Calendar class.

Clock displays the time, but is an hour out:

The Browser's Java implementation is relatively modern, but is running on UNIX (or similar) and the Calendar class doesn't understand the concept of daylight savings time in the Time Zone Environment variable (in-spite of what the documentation says).

Your Browser spits out something incomprehensible about an exception:

The Browser's Java implementation doesn't understand a class invocation (probably the Point class). It is truly too ancient for the clock, you'll have to get your time some place else.

Your Browser dies trying to display this page:

Your Browser's Java implementation is so broken that it fails on startup and brings the Browser down with it. Let me guess: Netscape distributed with Red Hat Linux 6.0. You may have already figured that and switched Java off to view this page.

In these instances ancient is defined as that which is earlier than Java 1.1.4 or thereabouts. Mail Mr. OLTP if the clock did something different to the above in your Browser. We will add it to the above list (with an attribution if you wish).

A number of you out there (well, one at least) have asked to see the Source Code for the Clock Applet. We're happy to publish it in the hope it may encourage more Feedback.

Updates

Feedback has suggested that the following needed to be changed after this had been published:

A Mobile Java Clock

As you can probably tell, this was written prior to the turn of the century, "Java 1.1", antediluvian or what? Much has happened since then, and many of the criticisms have been 'fixed' by later Java releases. Java remains a core and important programming language, however, and it has been extended to the mobile arena. Point and laugh at our sad efforts in this area too.

~Z~

Navigation

This is some navigation, it should appear at the side if the page is wide, and at the bottom if it is not.

Search

Seek enlightenment and wisdom: 

Example: "tuxedo".

Highlights

This site is mainly about On-Line Transaction Processing (OLTP). We've some other papers on this:

• Something for non-cognoscente.
• The executive summary.
• OLTP and big computers.
• OLTP and reliability.
• What Transactions are about.
• The need for scaling.
• Tuxedo.
• CICS.

Also of Interest

Juicy morsels from the rest of the site:

• Some site news; it's a sort of infrequently updated journal for the author too.
• Rather specific Technical Notes, the author can still bore people in the Historic Third-person.
• Of the little hacks that have been done recently, the Unofficial Jobcentre Plus Mirror seems to have gained the most traction.
• Other ephemeral, eclectic stuff. Mostly photographs.
• A series of Gormless Anecdotes, basically recycled e-mails.

About the Author

His name is Martin Sullivan. He's a fifty-something some-time computer programmer living in the quaintly named town of Cockermouth in north-west England.

The Company

ZOIS Limited is basically a vehicle for Martin and his OLTP work, he owns it. You can find out more about it elsewhere on the main site.

Pro-Bono Plug

Martin is currently on a health sabbatical, but is interested in the odd bit of pro-bono work by the way of therapeutic recovery. So, if you've anything that he can tackle on a non-commercial basis from his base in Cockermouth please let him know. Unsurprisingly, he's particularly interest in biology, again, and the application of computing to it.