Recursion vs iteration

Situations not to use recursion:
- recomputation of values (fibonacci, factorial, GCD)
- exhaust memory very quickly

Advisable to use iteration or memoization, instead, if you are so keen and persistent to implement recursion.

How to record the behavior of Internet users

I would like to discuss about this interesting topic which is sometimes wrongly perceived by many people as a menacing way practiced by some, if not many, Internet companies to invade one's privacy. I supposed there is a huge gap or the level of understanding that separates the consumers and the business people.

The technological perspective that I am illustrating in this article is about implementing "click-tracking". For software engineers that really know and understand whatever they are implementing, the server has no control over the dynamic HTML pages once the bits and bytes are presented to the end-users. For now, do we agree unanimously at this stage?

Great, thank you for agreeing to my thoughts! If so, I shall elaborate further about how "click-tracking" is implemented, especially at the anchor element <a> in the HTML document. There are at least three significant ways to track the links the users are clicking. I am taking an online video company as an example.

[1] Redirecting users to different servlets
This is the most common way to track user clicks. Imagine you are a registered user and while your session is still active:
1. You do a keyword search
2. You get a compiled list of result items in the result page
(eg: http://www.example.com/search/?q=keyword_string&pg=1)
3. You click at the link you think is most relevant to you
(eg: http://www.example.com/view/?videoID=12345678)
4. You enjoy watching the selected video
5. You demand for more videos and you reiterate step 1 again.
But WAIT ... what laymen do not know is that while they are busy with their viewing activities, the servers are busy harvesting the clicks of the links. Technically speaking, the servlet that is related to the URL request will update the user database with the unique video IDs, which I think is the most important element. Many interesting things can take place from here and one of them is to count the number of viewed videos.

[2] AJAX
Some of you might have this question popping in your mind "But what if the page is loaded dynamically using AJAX?". The implementation is actually quite similar to the one mentioned previously but with a slightly different flavor. By using AJAX, you can implement an asynchronous method to pass the video ID as an argument to the servlet using GET or POST method. The servlet will then take care of the rest without the user knowing whatever happens behind the scene (or their clicks are monitored).

[3] Javascript / AJAX
The other method to perform "click-track" is by using Javascript. This is used in the scenario where the search result page contains links that redirect users to the original sources and not within their domain. In other words, a totally different URL altogether. A GET or POST method is used to send the data back to the server.

While the 3 suggested implementations seem similar, they are actually not the same. I hope you find this article a good read and insightful about performing "click-track".

Binary Tree != B-tree

NOTE TO SELF: Binary tree is not B-tree
B-tree is commonly used in databases and filesystems.
Binary tree is used for binary search.

My pet project web-based music jukebox (part 2)

I have added a major feature in my web application to internationalize the page content. Hope you enjoy watching this video :)

Sorting a vector of objects using Comparator

Here is something really cool about sorting a Vector of objects. At least it is appealing to me. Let say we have a vector of "Students" objects and we are interested to sort the objects using one of its private fields, say, "StudentID" which is of data type Integer.

The code is as follow:

public static void anyMethod(){
  try {
    Collections.sort(yourVectorThatContainsObjects, ComparatorName);
  } catch (Exception ex) {}
}

public static Comparator<Object> ComparatorName = new Comparator<Object>() {
  public int compare(Object resultItem1, Object resultItem2) {
    Integer id1 = ((Students)resultItem1).StudentID;
    Integer id2 = ((Students)resultItem2).StudentID;
    return id2.compareTo(id1);
  }
};

The result of this sort is in descending order, eg largest to smallest. However there is a simple trick to sort it in an ascending order. Simply use "return id1.compareTo(id2);" It works for me. I hope it works for you too. Otherwise, please feel free to leave a comment so that I can investigate my code :)

My pet project

This is a brief introduction of my pet project. I hope you find this interesting. I am utilizing Java, jQuery and YouTube API to develop the entire web application. Here is the video.

An insightful presentation about Social Media