Posts in the “java” category

This code shows how to create a Java FlowLayout that flows left and has horizontal spacing of ten pixels and vertical spacing of five pixels:

FlowLayout flowLayout = new FlowLayout(FlowLayout.LEFT, 10, 5);
jPanel.setLayout(flowLayout);

Here’s what the FlowLayout constructor arguments look like:

FlowLayout(int align, int horizontalSpacing, int verticalSpacing);

FlowLayout 'align' property definitions

The align property can be any of these:

Java Jar file FAQ: Is there an easy way to delete a file from a Jar file?

Yes. Because a Jar file is just a Zip file, you can use the zip command to remove a file from a Jar file, like this:

zip -d MyApp.jar fileToDelete.foo

Of course the file to delete can be any sort of file. I just went through this process where I had to delete a configuration file, and my command looked like this:

As a quick note, if you ever need to use a Java TimerTask, you can define one like this:

class BrightnessTimerTask extends TimerTask {
    @Override
    public void run() {
        // your custom code here ...
    }        
}

and you can then instantiate it, create a Timer, and schedule the task like this:

Java/JVM FAQ: How can I see which garbage collector is running when I run a java command?

Use the -XX:+PrintCommandLineFlags command line argument, as shown here:

This JConsole page has some nice Java/JVM garbage collector terminology, including the following definitions:

Last week I ran into a situation where I was bundling a Java/Scala application on a Mac OS X system, which (as usual) requires you to bundle your code in a Jar file. I was working with the jnativehook library, where I saw some code like this:

As I get back into working with a MySQL database in a Java (Scala, actually) development project and also in adding functionality to Cato, I found these MySQL to Java data type mappings, via this link:

If you want to add menu items to your Dock menu in Mac OS X Java applications, I can confirm that this approach works:

As a quick note, I saw the PrintFlagsFinal Java/JVM option today, and thought it was interesting. I saw this command:

java -XX:+PrintFlagsFinal -Xmx64m -Xms32m -version 2>&1 | grep -i -E 'heapsize|permsize|version'

which yielded this output:

Mac Java FAQ: How do I report Mac Java bugs?

I just saw this information on the Mac Java mailing list, how to report Mac Java bugs:

I've been working with Scala quite a bit lately, and in an effort to get it all to stick in my brain, I've created a Scala cheat sheet in PDF format, which you can download below.

This PDF is very different from my earlier Scala cheat sheet in HTML format, as I tried to create something that works much better in a print format. (I first tried to get it all in one page, but short of using a one-point font, that wasn't going to happen.)

I was just reading the book, Hadoop in Action, and came across a nice, simple way to use the Java StringTokenizer class to break a sentence (String) into words, taking into account many standard punctuation marks. Before looking at their solution, first take a look at the code they used to break a String into words using whitespace (a blank):

I just ran across a nice example of a Java static initializer block example in an Android book, and thought it might be helpful to share that example here.

First, here's the static initialization code:

Sigh, so many broken links, so little time ... when I switched this website to Drupal, I didn't (couldn't) take the time to move all of my static content in the Drupal CMS, so a lot of great content is just sitting out there in static files. To help fix that problem a little bit, here's a link to a collection of Java test project (example projects) that demonstrate all sorts of cool and fun things with Java, including:

Java image FAQ: How do I crop an image in Java?

To crop an image in Java, just use the Java BufferedImage class, specifically the getSubimage method of the BufferedImage class.

As I go through some old applications I wrote for various purposes, but never released, I thought I'd share the source code for a Java program that you can use to get the x/y coordinates or the mouse cursor (pointer) and RGB value of the pixel at that location. I've used this application for various reasons, including determining the location of something on screen, determining the width or height between two points, or getting the RGB value of a pixel on screen.

Java image FAQ: Can you show me how to create a screen capture in Java?

I don't have any Java screen capture code to share at the moment, but if you don't mind a JRuby screen capture example (which you can easily convert to Java), this JRuby screenshot (screen capture) source code example should help point you in the right direction:

Just a quick note that over the last few days I finished a major re-work of my old Java and Object Oriented Programming (OOP) training material. I used variations of this Java/OOP training material with several classes I taught from 1998 through about 2005.

I still need to make a few more changes to improve the material, but this big change involved reformatting the training material (courseware) into much longer pages that are easier to read, and improving the appearance of the pages.

I'm not sure how much call there is for a simplified Nagios web interface (user interface), but I wrote one last year, and I'll be releasing it here soon, after many comments on my Nagios MySQL database design article, along with many, many personal emails.

Summary: I'm sharing my Java True License client and server source code. This code is taken from a Java/Swing software application which I successfully licensed and sold using the True License software library.