This book was my personal choice, kindly agreed to by the other members of the group. Everyone seems to enjoy the book thus far, even when I presented chapters four and five this week!

If you’re in the Phoenix area, come join us! Drop by Gangplank at 8:00pm on any Wednesday.

Integer.toString(Math.abs(random.nextInt()))

Findbugs indicated there was a possibility that I might end up with a negative value even though I “cleverly” used Math.abs().

RV: Bad attempt to compute absolute value of signed random integer (RV_ABSOLUTE_VALUE_OF_RANDOM_INT)

If the number returned by the random number generator is Integer.MIN_VALUE, then the result will be negative as well

Even though I didn’t need this random id to be perfect — the unintended side-effect wasn’t a technical problem since I used it as a String — I still wanted to fix it. Stackoverflow to the rescue.

A question-and-answer from Stackoverflow pointed the way to the solution: java.util.UUID. Somehow, I missed that Sun had added Java’s own universally unique identifier (UUID) generator in Java 1.5.

In the end, I happily replaced my homemade id generator with Java’s.

UUID.randomUUID().toString()

The output of which is something like 1c312843-8903-411f-88b2-ff1b92ca80ba.

Cross-posted at http://java.dzone.com/articles/global-unique-identifiers-java.

Several months ago I became frustrated with repeated navigation from one to the other, so I began using a symbolic link. In ~ I created a link to %USERPROFILE% with ln -s "$USERPROFILE" home. Thus, any time I wanted to change to my Windows home directory I would simply cd ~/home.

It worked, but that dichotomy remained… Then, it occurred to me: why couldn’t ~ and %USERPROFILE% be the same?

Luckily, they can!  In fact, the Cygwin documentation on alternate home roots shows exactly how. Using mkpasswd, one or all home directories may be set to any arbitrary path; to change all home directories to the Windows home directory:

mkpasswd -l -p "$(cygpath -H)" > /etc/passwd

Pretty neat. See the Cygwin documentation on alternate home roots for more information.

By default, Eclipse does a pretty good job of syntax highlighting Java files without going overboard. But, if you want a fresh look — maybe you want to try a dark background — the Eclipse Color Theme plugin lets you change whole editor themes with the click of your mouse.

The Eclipse Color Theme plugin is free and so are the themes. So far I’m liking the dark Oblivion theme, shown below.

To complicate matters, I had recently removed OS X 10.4 and installed Ubuntu 10.10 on the PowerBook in an ill-fated attempt to give it new life. The PowerBook was a great computer in its time but, these days, PowerPC is a dying, if not already dead, architecture. Flash 10? Not on PowerPC. Google Chrome? Nope.

On the Mini, which ran Windows 7 Starter, I used WUHU for data acquisition and upload. That program worked well, but obviously an x86 PC app just would not do the trick on Linux or a PowerPC. Some searching led me to wview which worked on Linux and was capable of running on something like a NSLU2 or plug computer. It would either be perfect or a perfect mirage.

And then there was the issue of my USB-to-Serial adapter, for connecting the computer to the weather station console. Who knew if that would work?

So, there I was with a dead architecture, the wrong OS, a questionable USB adapter and… well, let’s just say I wasn’t very hopeful.

But… it worked! Much to my surprise, I was able to get data from my weather station, using wview, through the USB adapter, into the PowerBook, and out to the world. Here’s how I did it:

1. Installed Ubuntu 10.10 for PowerPC.
2. Tested the IOgear GUC232A USB-to-Serial Adapter and it worked right out of the box.

   USB Serial support registered for pl2303
   usb 3-1: pl2303 converter now attached to ttyUSB0
   usbcore: registered new interface driver pl2303
   pl2303: Prolific PL2303 USB to serial adaptor driver
   

3. Followed wview Debian Quick Start Guide. Downloaded and executed wview-install-debian, encountered first problem:

   In file included from ../htmlgenerator/htmlStates.c:36:
   ./glchart.h:28: fatal error: gd.h: No such file or directory

4. Installed libgd2.

   apt-get install libgd2-noxpm-dev

5. Executed wview-install-debian again, encountered second problem:

   http.h: error: curl/curl.h: No such file or directory
   

6. Installed libcurl4.

   apt-get install libcurl4-openssl-dev

7. Executed wview-install-debian again; encountered problem; re-ran as

   wview-install-debian -f

8. From here out, I followed the wview user manual for configuration.

Check it out, it's a live, daily temperature graph. For reals.

Anyway, here’s my weather page:

http://christiansons.net/mike/weather/

It’s nice to have brought life back to disused computer; it’s nice to have my Mini back!

P.S. Not having tried wview on OS X, I can’t compare the experience or difficulty.

socat TCP-L:4096,fork -

Socat is quite powerful, be sure to read more about what it can do.

2011-July-08: My coworker has a great post showing how socat can pipe data from a serial port to a socket!

Please leave a comment if you have corrections or additional tips! (And, preemptively, yes, some day I’ll give Joda Time a try.)

• Dates do not have timezones; they reflect UTC.
• Date.toString() returns a String representation based on the local machine’s default timezone. This makes people think that Dates have timezones.
• You cannot convert a Date from one timezone to another.

Calendar c = Calendar.getInstance();
c.setTime(new Date());
c.setTimeZone(TimeZone.getTimeZone("UTC"));
Date utc = c.getTime();
c.setTimeZone(TimeZone.getTimeZone("America/Phoenix"));
Date mst = c.getTime();
assert !utc.equals(mst);  //throws AssertionError

• However, you can use DateFormat to affect the String representation of a Date, including the timezone.

Date date = new Date();
SimpleDateFormat utcFormat = new SimpleDateFormat("ddHHmm");
SimpleDateFormat mstFormat = new SimpleDateFormat("ddHHmm");
utcFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
mstFormat.setTimeZone(TimeZone.getTimeZone("America/Phoenix"));
String utc = utcFormat.format(date);
String mst = mstFormat.format(date);
assert !utc.equals(mst);  //should not throw AssertionError