Java User Group Münster » java

30.7.: Clojure Presentation with Alex Ott

Thomas — Thu, 22 Jul 2010 15:07:59 +0000

Clojure is a language running on the Java Virtual machine and gaining rapid popularity. Beeing a general-purpose language supporting interactive development that encourages a functional programming style, and simplifying multithreaded programming its usage is particularly promising in high concurrency/throughput environments.Alex Ott will present Clojure in a technical demonstration on Friday, July 30th in Muenster, covering these topics:

What is Clojure?
Why was the language was created
Language basics
Interoperability with Java
Concurrent programming – how Clojure simplify concurrent programming
Clojure in real life – tools, real projects, etc.
Sources of information
Examples & demonstrations

Alex Ott is currently working for McAfee Inc. and has profounded experience in development of content filtering and data leakage prevention solutions. He is leader of software development projects in the OpenSource and commercial space and is author of physics and computer science related articles and books.

The Clojure event will be performed at Leonardo Campus 18 (Google Maps Link), entry is at 6 PM, start is 6:30 PM. (18:00 Uhr)

Beverages and some snacks will be provided. Follow us on Twitter (JUG_MS) or join our Mailing List to keep up to date!

Java2D Conical Gradient Paint

Gerrit — Wed, 21 Jul 2010 13:28:10 +0000

Just a short blogpost about a little tool that i would like to share with you…
A few months ago i was creating a worldclock with a night and day display where i needed a conical gradient.
So what is a conical gradient ? Here we go…

You might think “ok, it looks nice but where is it useful ?”…well here are three little examples…

So if you would like to achieve these results without the conical gradient paint you have to rotate a line a change the color at every angle. This works out but if it comes to large angles you have to decrease the stepsize which leads to artifacts around the rotation center.

So the conical gradient paint is especialy useful when you work with rotationally symetrical stuff. With this kind of gradient you could get more realistic results of circular structures like the two buttons in the image above. On the left side i used a conical gradient and on the right side i used a linear gradient.

For most of the stuff the linear approach will work but the conical gradient gives you a more realistic shading. Things like the stainless steel button is hard to be generated without a gradient like this.

So let me show you some code to give you an idea of how to work with the ConicalGradientPaint:

The syntax is similar to the LinearGradientPaint and RadialGradientPaint where you define a float array that holds all the fractions of the gradient, a color array that holds all the colors for each fraction and a point that defines the rotation center of the gradient.

Additional to that standard parameters i added a indicator for the usage of degrees and a rotation offset.

Usage:

ConicalGradientPaint cgp = new ConicalGradientPaint(USE_DEGREES, CENTER, OFFSET, FRACTIONS, COLORS);

USE_DEGREES = true/false

CENTER = java.awt.geom.Point2D

OFFSET = float (either 0.0f – 1.0f or 0.0f – 360.0f)

FRACTIONS = float[] (either values from 0.0f..1.0f or from 0.0f..360.0f)

COLORS = java.awt.Color[]

// Code for a simple cone like from black over white to black
final Ellipse2D CONE = new Ellipse2D.Double(0, 0, 150, 150);

final Point2D CONE_CENTER = new Point2D.Double(CONE.getCenterX(), CONE.getCenterY());

final float[] CONE_FRACTIONS =
{
    0.0f,
    0.5f,
    1.0f
};

final java.awt.Color[] CONE_COLORS =
{
    java.awt.Color.BLACK,
    java.awt.Color.WHITE,
    java.awt.Color.BLACK
};

final ConicalGradientPaint CONE_GRADIENT = new ConicalGradientPaint(
	CONE_CENTER,
	CONE_FRACTIONS,
	CONE_COLORS);

G2.setPaint(CONE_GRADIENT);

G2.fill(CONE);

As you can see it’s not magic but simple stupid java code and with a little variation in colors and fractions you could achieve effects like the stainless steel button.

In my free time i’m working on a new component library (mostly gauges) where i also could use the conical gradient paint.

In the screenshot you could see that the gauge has a area from 10 to 60 where it has a gradient in the background. This gradient is also filled by the ConicalGradientPaint.

So you see it could be useful to have this kind of gradient available and for that reason i would like to share it with you…

Here is the source as zipped Netbeans project. It contains the ConicalGradient class and a little demo that will give you an idea of how to use the paint.

In this project you’ll also find a compiled jar that you could start and it will show you this

So enjoy Swing and follow me on twitter if you like…

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Java Stammtisch: 23.6. ab 18:30 Uhr

Thomas — Mon, 21 Jun 2010 08:09:27 +0000

Wir möchten zum nächsten Java Stammtisch in Münster einladen! Herzlich willkommen sind alle an Java und Softwareentwicklung interessierten Personen. (Damit sind auch PHP, Ruby on Rails, .NET und Scala Entwickler gemeint ) In entspannter Atmosphäre gibt es Gelegenheit zum gegenseitigen Austausch, Kennenlernen oder auch Diskussionen beizuwohnen.

Hinweis: Wir haben eine neue Mailingliste, wer per E-Mail auf dem Laufenden gehalten werden möchte, kann sich mit einer E-Mail an jug-join@list.jug-muenster.de eintragen.

Der Java Stammtisch findet Mittwoch ab ca. 18:30 Uhr im Cuba Nova statt. Das Cuba Nova befindets ich in der Achtermannstrasse in der Nähe vom Hauptbahnhof. (3 Minuten zu Fuß, wenn man langsam geht.).

Für Teilnehmer am Java Stammtisch gibt es einen Sonderpreis für Weizen, zudem gibt es auch Aktionsangbote bei Speisen.
Parkmöglichkeiten und Anfahrt zum Java Usergroup Münster Treff: Parkhaus Engelenschanze ist am nächsten gelegen. Ansonsten empfehlen wir die Anreise mit dem Rad oder öffentlichen Verkehrsmitteln – insbesondere für Weizen-Fans. (Google Maps Link)

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Stammtisch: Java Runde am 9.6.

Thomas — Mon, 07 Jun 2010 11:45:22 +0000

Die Java Usergroup Münster lädt am kommenden Mittwoch zum nächsten Java Stammtisch in Münster ein: Für alle an Java, Softwareentwicklung und aktuellen Trends interessierten Personen – auch PHP, Ruby on Rails Entwickler sind natürlich willkommen!

Der Java Treff findet Mittwoch ab ca. 18:30 Uhr im Cuba Nova statt. Das Cuba Nova befindets ich in der Achtermannstrasse in der Nähe vom Hauptbahnhof. (3 Minuten zu Fuß, wenn man langsam geht.).

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Using Smack xmpp lib on Android with Netbeans

Gerrit — Tue, 11 May 2010 04:58:47 +0000

Last week i got my Android phone and finally started coding for a mobile phone (which really is a great experience and lot’s of fun).

During my daylight work i’m using xmpp in different projects and tools and so i would really like to use it on the Android phone also. In the java world there is a really neat library called smack from ignite realtime which makes using xmpp a piece of cake and so i asked myself if it would also run on android?

Yes it does…BUT…you need a patched version that i found on the net…
In Eclipse it seems to be easy to link a external library to a android project but in Netbeans i was not so intuitively as i thought…
You need three little steps to include a external library like smack and here they are:

#1 STEP:

Create a local folder named “lib” in your Android project folder like this:

Now copy the patched smack.jar file into this folder.

#2 STEP:

Add the jar file to your libraries in netbeans like this:

#3 STEP:

At last you have to edit the build.xml file of your android project and add the link to the /lib folder where you copied the library file.

Add the following to the end of your build.xml file:

name=“-pre-jar”>

name=“external.libs.dir” value=”/PATH_TO_YOUR_PROJECT/lib“ />

todir=“${build.classes.dir}”>

dir=“/PATH_TO_YOUR_PROJECT/lib” />

That’s it…

Now you should be able to use the external library in the same way as you know it from your normal desktop machine.
Be aware that the patched smack.jar does not contain the complete functionality of the desktop version…
You might also take a look at a project called asmack which you could find here…

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Java Stammtisch Münster: 12.5.

Thomas — Mon, 10 May 2010 07:36:36 +0000

Kommenden Mittwoch ist es wieder soweit: Der nächste Java Stammtisch findet am Mittwoch den 12.05. im Cuba Nova statt.
Für alle an Java, Softwareentwicklung und aktuellen Trends interessierten Personen – auch PHP, Ruby on Rails Entwickler sind natürlich willkommen!

Der Java Treff für Münster, Osnabrück und Umgebung findet am Mittwoch ab ca. 18:30 Uhr im Cuba Nova statt. Das Cuba Nova befindets ich in der Achtermannstrasse in der Nähe vom Hauptbahnhof. (3 Minuten zu Fuß, wenn man langsam geht.).

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Java Stammtisch

Thomas — Sun, 11 Apr 2010 17:37:40 +0000

Am 14.04. findet wieder ein Java Stammtisch in Münster statt!

Für alle an Java, Softwareentwicklung und aktuellen Trends interessierten Personen – auch PHP, Ruby on Rails Entwickler sind natürlich willkommen!

Für Teilnehmer am Java Stammtisch gibt es einen Sonderpreis fuer Weizen, zudem gibt es auch Aktionsangbote bei Speisen.
Parkmöglichkeiten und Anfahrt zum Java Usergroup Münster Treff: Parkhaus Engelenschanze ist am nächsten gelegen. Ansonsten empfehlen wir die Anreise mit dem Rad oder öffentlichen Verkehrsmitteln – insbesondere für Weizen-Fans. (Google Maps Link)

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Swing event departure board

Gerrit — Wed, 24 Mar 2010 07:18:48 +0000

Sitting at Gard du Nord train station in Paris in January this year i saw this huge departure board:

It was fascinating to see and hear all these flipping characters everytime a departure time changed. I guess most of you know already how these boards work but for all others i will explain it shortly.

The arriving trains are in chronological order from top to bottom of the board which means the trains that arrives as next stays on top of the board.
The flipping characters are made of little metal plates that are printed on the front and backside with characters that are split into half. The Top part of the character is printed on the frontside of the upper plate and the bottom part of the character is printed on the backside of the lower plate (i tried to visualize it with a little image).

So if the current character the element shows is a “B” and it should show up the character “C” it only flips once and the next character will be the “C” BUT if it should shup up the character “A” it has to flip through the whole stack of characters until it reaches the “A” because there is only one direction it could flip.

I was asking myself if it might be possible to do that in swing and on my way back to germany i started creating a flipping character component in Adobe Fireworks and Netbeans.
So the design of the component and the logic behind it was one thing but the flipping of the plates was a totaly different problem.
For a realistic view i would need something like a perspective transform which is not available in Swing. First i skimmed through Google search results to find something and found solutions to this problem but for just a little component the solutions have been to heavy.
Next thought was JavaFX because there you have a perspective transform and so i thought about using JavaFX to do the transformation and use the transformed images in swing…but i was not able to do so.

In the end it was a really easy solution even if it’s not as close to the reality as i whish it would but when i thought about the speed the characters are flipping with i found out that you won’t really notice each plate flipping. So the solution is using “fake images” for each flipping state which has the big advantage that i could use the same images over and over again. Here is what they look like:

So it just lacks the characters on the plate during the flip but on the other hand it’s faster because i do not have to transform the images on each flip but only playback a sequence of images.

The resulting swing component looks like this:

Now it was easy to create a panel that holds some of these flipping characters and put some logic in that the panel represents a word.

Satisfied with this solution i left the component like it was and moved to other things but when i was at JFokus conference in february in sweden i got the problem that i did not have the exact schedule of all the talks which leads me to the following idea…

Every appointment in my calendar (meetings etc.), talks on our JUG events and all other time based events could be handled by a departure board like the one i saw at Paris. So i started creating a talk departure board that we could use for our JUG events.

Now i was facing another problem that did not occur before, if i use a lot of these flipping characters i need a lot of animation at the same time which means a lot of redraws etc. which could make things slow down.
For that reason i implemented a global timer that triggers the flipping of every character so that they are flipping at the same time. The next problem was the space the component would need…it’s huge (around 1600 px wide). I created the departure board for big screens with resolutions around 1920 px because it was not made for personal use on your notebook but for big screens at JUG events (you might tweak the component if you need a smaller one).

To get a better look i needed a analog clock to show the current time and some led to visualize the next upcoming event. And here they are:

With all these components available i started creating the departure board and the final result looks like this (only parts because it’s too big):

To fill the component with data i created a small xml file that contains the events (this could be improved) wich contains data like event title, event date and time, title, speaker and room of each talk. You could also add your own logo image (png format) to the upper right corner of the departure board by defining it in the xml file.
The component will read in the xml file at startup if it is in the same folder and will display the events.
If there will be a event within the next 5 minutes the green led at the beginning and end of the event will start to blink and they will stop blinking if the current event is running for more than 5 minutes. In this case the top event will be deleted from the board and all other events will move one row up in the list.

Well i finished this component in february but did not find the time to make further improvements to it so i decided to release it as it is to give you something to play with.

It might be usefull for some of you (e.g. you could use it in your company to visualize appointments with visitors at the lobby).

After start up it will take some seconds to flip every component through the whole stack (which might be slow) but after this the flipping of the rows should be faster (but could still be improved).

Finally here is a link to a little video where you could see the component in action.

Swing talk departure board

And as always the source as Netbeans project (EventTalkBoard.zip).

Follow me on twitter if you like…

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Swing Weather Worldclock

Gerrit — Tue, 23 Mar 2010 06:44:58 +0000

Remember the worldclock blogpost? Well it was ok but i thought there was one thing missing…

Weather information

For that reason i added this missing feature to the known worldclock component so that you now might choose out of four clocks:

Pure clock and icon indicator for time of day
Pure clock, icon indicator for time of day and weather information
Clock with inbuild time of day display
Clock with inbuild time of day display and weather information

This image shows all available clocks:

To get the weather information for all the cities in the enum i provide, i needed to add the country for each city and by adding all these countries i translated the cities to their (hopefully) right english names (in the original worldclock post i used german city names).

I use weather underground to retrieve the weather information because they provide an easy to access service for free. You will find a package called “net” in the project in which i put the classes responsible for fetching the weather condition. There is timer which checks every 30 seconds for the availability of the connection.
The clockpanels will every 10 minutes add a so called ConditionFetcher thread to the queue of the WeatherService which will be handled by a ExecutorService. The WeatherService will tries to use the system proxy server if there is one so it hopefuly works out for you.

The most of the work was done by creating all the different weather condition images which you will see in the next image:

And of course we will have different images for the night (but only different if the moon is visible), here they are:

Additional to the current weather condition you will find the min and max temperature below the condition image and you could choose between degrees celsius or fahrenheit as temperature unit.

In the project you will find a package called “app” and in this package you will find four classes called “Main1″, “Main2″, “Main3″, “Main4″. Each of these classes will start a different version of the worldclock with the four cities (Hong Kong, Berlin, New York, San Francisco) so if you are fine with the cities just select the right class as start class in the netbeans project properties and compile it. Otherwise change/add/remove the cities as you like.

Here are the four predefined worldclocks:

Main1.class

Main2.class

Main3.class

Main4.class

So that’s the weather worldtime clock and as always you will find the source as zipped netbeans project here.

By the way i’m still not satisfied with this version. I’m currently working on a different approach where i try to visualize the time of the day and combine it with weather and a clock but that project will take some more time to finish. Here is a little preview:

But that’s a different story…

Enjoy Java and follow me on twitter if you like…

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24.03. – Java Stammtisch Münster

Gerrit — Mon, 22 Mar 2010 16:27:22 +0000

Am 24.03. gibt es wieder den Stammtisch der Java User Group Münster! Ein Angebot für alle an Java, Softwareentwicklung und aktuellen Trends interessierte Personen – auch PHP, Ruby on Rails Entwickler sind natürlich willkommen!

Der Java Treff für Münster, Osnabrück und Umgebung findet am Mittwoch dem 24.03. ab ca. 18:30 Uhr im Cuba Nova statt. Das Cuba Nova befindets ich in der Achtermannstrasse in der Nähe vom Hauptbahnhof. (3 Minuten zu Fuß, wenn man langsam geht.).

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