Facebook Chat with Pidgin

In a previous post, I wrote about how you can use Pidgin to replace Office Communicator (OCS). Now, I will show you how you can use Pidgin for Facebook chat, thereby making Pidgin a truly universal chat client!

• Start the Pidgin client.
• Add a new Account with the following details:
• Protocol: XMPP
• Username: yourfacebookusername
• Domain: chat.facebook.com
• Password: facebookpassword
• On the Advanced tab, untick "Require SSL/TLS".

Leaving DB

Today is my last day at Deutsche Bank.

I've been at DB for six years. I started as a graduate and, over the years, have learnt so much, not just about technology, business and processes, but also about myself. I've had the opportunity to work with some of the best minds in the bank and have made some great friends. I would like to thank all my colleagues for their guidance and support and for making my time at DB so enjoyable. I will miss you all!

Leaving DB is by far the hardest decision I've ever had to make, but I feel that the time has come for me to move on to new challenges.

I'm certainly planning to keep blogging and tweeting, so stay tuned to find out what I am getting up to.

Journey onward!

Software Inventory of my Windows Machine

As I will be leaving my computer soon, I have decided to make a quick list of useful applications currently installed:

Category	Name	Description
Database	Aqua Data Studio	Database Query Tool
Database	JaySQL	JDBC Database Tool
Database	Toad	Oracle Database Tool
Dev	Ant	Build Tool
Dev	Axis 1.4	Web Services Engine
Dev	Axis 2	Web Services Engine
Dev	Chainsaw	Log Viewer
Dev	Cobertura	Code Coverage Tool
Dev	Eclipse	IDE
Dev	Groovy	Programming Language
Dev	GWT	Google Web Toolkit
Dev	HermesJMS	JMS Browser
Dev	HSQLDB	Java Database Engine
Dev	JAD	Java Decompiler
Dev	Java	Programming Language
Dev	Maven	Project Build Tool
Dev	Perl	Programming Language
Dev	PuTTy	SSH Client
Dev	Python 2.6	Programming Language
Dev	SciTE	Source Code Editor
Dev	soapUI	Web Service Caller
Dev	SQLite	SQL database engine
Dev	Tomcat	Servlet Engine
Dev	TortoiseCVS	CVS Client
Dev	WinMerge	Differencing and Merging Tool
Dev	xmlbeans-2.4.0	XML to Java type binding
Editor	Altova XML Spy	XML Editor
Editor	Emacs 22.3	Text Editor
Editor	TextPad 4	Text Editor
Performance	CachemanXP	Windows Tuneup Utility
Performance	CCleaner	PC Cleaner
Performance	Defraggler	Disk Defragmenter
Performance	HijackThis	System Scanner
Productivity	Alt-Tab Task Switcher	MS Powertoys
Productivity	Calculator Powertoy	MS Powertoys
Productivity	ClipX	Clipboard History Manager
Productivity	CmdHere Powertoy	MS Powertoys
Productivity	LClock	Clock
Productivity	Password Safe	Password Manager
Productivity	ProcessExplorer	Task Manager
Productivity	PsTools	Windows Tools
Productivity	SlickRun	Quick Application Launcher
Productivity	Taskix	Reorder taskbar items
Productivity	Tweak UI	MS Powertoys
Productivity	UnxUtils	GNU Utilities for Windows
Productivity	xplorer² lite	Windows File Manager
Utilities	Convert Image To PDF	PDF Converter
Utilities	doPDF 7	PDF Converter
Utilities	Foxit	PDF Reader
Utilities	WinRAR	Archive Manager
Utilities	xmltidy	TextPad addon
Web	Mozilla Firefox	Web Browser
Web	Pidgin	Instant Messenger

And, ofcourse, browsing wouldn't be the same without my Firefox addons:

Firefox Addons
Adblock Plus
All-in-One Sidebar
British English Dictionary
Cache Status
Colorful Tabs
Delicious Bookmarks
Download Statusbar
DownThemAll!
dragdropupload
FaviconizeTab
Firebug
Fission
Flashblock
Forecastfox
FoxClocks
Greasemonkey
Mouse Gestures Redox
Tab Mix Plus
Tab Preview
Ubiquity
URL Fixer

If you think you have better alternatives for any of the applications above, please write a comment!

Faster XPaths with VTD-XML

I've recently started using VTD-XML for applying XPaths on large XML documents. DOM is a memory hog and is too slow. However, VTD-XML allows you to run XPaths and provides random access to nodes, similar to DOM, but much more efficiently. You can't apply XPaths with a SAX parser nor can you access nodes randomly or traverse the document easily.

VTD-XML was 60 times faster compared to DOM when processing my XML document (20MB).

This post shows you how to use VTD-XML for fast XPath evaluation.

Sample XML:
I will use the following XML document in the examples below.

<?xml version="1.0"?>
<catalog>
 <book id="bk101">
  <author>Gambardella, Matthew</author>
  <author>Doe, John</author>
  <title>XML Developer's Guide</title>
  <genre>Computer</genre>
  <price>44.95</price>
  <publish_date>2000-10-01</publish_date>
 </book>
 <book id="bk102">
  <author>Ralls, Kim</author>
  <title>Midnight Rain</title>
  <genre>Fantasy</genre>
  <price>5.95</price>
  <publish_date>2000-12-16</publish_date>
 </book>
 <book id="bk103">
  <author>Corets, Eva</author>
  <title>Maeve Ascendant</title>
  <genre>Fantasy</genre>
  <price>5.95</price>
  <publish_date>2000-11-17</publish_date>
 </book>
</catalog>

Loading the XML document:
The following code parses the XML file and creates the navigator and autopilot objects.

final VTDGen vg = new VTDGen();
vg.parseFile("books.xml", false);
final VTDNav vn = vg.getNav();
final AutoPilot ap = new AutoPilot(vn);

Selecting all titles:
Print out all the title nodes using an XPath expression of /catalog/book/title. First call selectXPath to compile the expression and then use evalXPath to move the cursor to the selected nodes in the result.

ap.selectXPath("/catalog/book/title");
while (ap.evalXPath() != -1) {
  int val = vn.getText();
  if (val != -1) {
    String title = vn.toNormalizedString(val);
    System.out.println(title);
  }
}

Selecting all book ids and authors:
This one is a bit more involved as a book can have many authors. In the code below, I first run an XPath to select the books and then iterate over the children, selecting the author nodes.

ap.selectXPath("/catalog/book");
while (ap.evalXPath() != -1) {
  int val = vn.getAttrVal("id");
  if(val != -1){
    String id = vn.toNormalizedString(val);
    System.out.println("Book id: " + id);
  }

  if(vn.toElement(VTDNav.FIRST_CHILD,"author")){
    do{
      val = vn.getText();
      if(val != -1){
        String author = vn.toNormalizedString(val);
        System.out.println("\tAuthor:" + author);
      }
    }while(vn.toElement(VTDNav.NEXT_SIBLING,"author"));
  }
  vn.toElement(VTDNav.PARENT);
}

The output is:

Book id: bk101
 Author:Gambardella, Matthew
 Author:Doe, John
Book id: bk102
 Author:Ralls, Kim
Book id: bk103
 Author:Corets, Eva

Related Posts:
Using XPath with DOM

Fixing a ConcurrentModificationException

Question:
The following code throws a ConcurrentModificationException. What additional code can you add between the <FIXME>...</FIXME> tags in order to prevent this exception from being thrown?

final List<String> list = new ArrayList<String>();
list.add("HELLO");
final Iterator<String> iter = list.iterator();
System.out.println(iter.next());
list.add("WORLD");
//<FIXME>

//</FIXME>
System.out.println(iter.next());

Solution:
In this example, a ConcurrentModificationException is thrown because the Iterator detects that the list over which it is iterating has been changed. If you look into the source code for these classes you will find that when an Iterator is created, it contains an int variable called expectedModCount which is initialised to the modCount of the backing list. Whenever the backing list is structurally modified (with an add or remove operation, for example) then the modCount is incremented. As a result, the iterator's expectedModCount no longer matches the list's modCount and the iterator throws a ConcurrentModificationException.

In order to prevent this exception from being thrown, we need to bring the expectedModCount of the iterator and the modCount of the list back in line with each other. Here are a couple of ways this can be done:

1. Reflection:
Reflection is the easiest way to change the internal counters of the iterator and list. In the fix below, I have set the expectedModCount of the iterator to the same value as the modCount of the list. The code no longer throws the ConcurrentModificationException.

final List<String> list = new ArrayList<String>();
list.add("HELLO");
final Iterator<String> iter = list.iterator();
System.out.println(iter.next());
list.add("WORLD");
//<FIXME>
/* Using Reflection */
try{
  //get the modCount of the List
  Class cls = Class.forName("java.util.AbstractList");
  Field f = cls.getDeclaredField("modCount");
  f.setAccessible(true);
  int modCount = f.getInt(list);

  //change the expectedModCount of the iterator
  //to match the modCount of the list
  cls = iter.getClass();
  f = cls.getDeclaredField("expectedModCount");
  f.setAccessible(true);
  f.setInt(iter, modCount);
}
catch(ClassNotFoundException e){
  e.printStackTrace();
}
catch(NoSuchFieldException e){
  e.printStackTrace();
}
catch(IllegalAccessException e){
  e.printStackTrace();
}
//</FIXME>
System.out.println(iter.next());

2. Integer Overflow:
Another approach is to keep modifying the list until the integer modCount overflows and reaches the same value as expectedModCount. At the moment, modCount=2 and expectedModCount=1. In the fix below, I repeatedly change the list (by calling trimToSize), forcing modCount to overflow and reach expectedModCount. This code took 38s to run on my machine.

final List<String> list = new ArrayList<String>();
list.add("HELLO");
final Iterator<String> iter = list.iterator();
System.out.println(iter.next());
list.add("WORLD");
//<FIXME>
for(int i = Integer.MIN_VALUE ; i < Integer.MAX_VALUE ; i++){
  ((ArrayList)list).trimToSize();
}
//</FIXME>
System.out.println(iter.next());