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  Writing unit tests for legacy code – an open letter to developers I work with

This is an email I sent today to developers who work with me, it is exactly as I wrote it except for project and developer names which I’ve redacted. Dear Developers, S asked me a difficult question today, and I think the answer (which took me a few minutes to arrive at) is worth sharing with all developers, mainly because many of you will surely face the exact same problem especially in [maintenance and enhancement] projects. By now I think it is crystal clear that one of our non-ne...

   Unit testing,Open letter     2012-02-09 05:39:56

  Select top 3 values from each group in a table with SQL

Yesterday, my friend Liu Bing asked me a question about how to select top 3 values for each person in a database table using SQL. I think this question is interesting and it deserves some thoughts. Here I record down how to solve this issue. Assume we have a table which has two columns, one column contains the names of some people and the other column contains some values related to each person. One person can have more than one value. Each value has a numeric type. The question is we want to se...

   SQL,Correlated query,top 3     2013-05-23 03:21:25

  How To Write A Good Programming Test

I’ve taken and marked a lot of programming tests in the past. I love doing them as it’s always good to see what challenges different programmers have come up with when designing them. Unfortunately, however, most of them aren’t very good. Below is a list of general ideas to help increase the quality of programmer tests. 1. Keep it relevant Too many of the tests have questions on content that simply isn’t relevant to the job. The whole idea behind a programming test i...

   Programming test,Interview,Questions,Pro     2011-08-26 02:46:44

  Implementation of +,-,*,/ with bitwise operator

There is a question asked on Stackoverflow : Divide a number by 3 without using *,/,+,-,% operators. This question is an Oracle interview question. Some people give excellent answers. You can go there and take a look. Usually we need to use bitwise operators to do this kind of implementations. Here I want to show you ways to implement +,-,*,/ with bitwise operators. A bitwise operation operates on one or more bit patterns or binary numerals at the level of their individual bits. It is a fast, pr...

   Bitwise operator,Shift,Add,Subtract,Multiplication,Division     2012-08-05 01:52:47

  A boolean value interview question

Someone asked a question on StackOverflow, he was asked an interview question. The question is : Given 3 boolean variables a, b, c, return true if at least 2 out of the 3 are true. He gave the solution as follows :boolean atLeastTwo(boolean a, boolean b, boolean c) {    if ((a && b) || (b && c) || (a && c)) {        return true;    } else {        ret...

   bool,return,expression,conditional     2012-04-30 08:49:32

  Magic CSS shape

There is a question on StackOverflow which states that someone finds a CSS sample on http://css-tricks.com/examples/ShapesOfCSS/  , the sample shows a triangle created with pure CSS. The source code is :#triangle-up {width: 0;height: 0;border-left: 50px solid transparent;border-right: 50px solid transparent;border-bottom: 100px solid red;}The question is how these few lines can create a triangle? Next we give the answer and the detail illustration to this question We need to consider the B...

   CSS,Triangle,Box model,Border     2012-04-20 12:56:22

  Convert JKS to BKS using keytool

There are lots of questions(question 1, question 2) on Stackoverflow about how to convert JKS keystore to BKS keystore(a keystore format provided by BouncyCastle) using Java keytool.  The reason why this conversion gets lots of questions is that BKS is not a keystore format supported by Java SE, it's a third party keystore format. To convert JSK to BKS, the BKS provider has to be downloaded first. And a few more options needs to be added when running the keytool command. The typical co...

   JKS,BKS,KEYTOOL,JAVA,SECURITY     2016-07-14 03:49:52

  Origin of Windows blue screen

Many of you from old ages might see the classical blue Windows blue screen before.Do you still remember the most famous Windows blue screen incident during a presentation of a Windows 98 beta by Bill Gates at COMDEX on April 20 1998. But do you know the history of blue screen? John Vert, an ex-Windoes NT kernel guy, shared the story on Quora.  Back in 1991 John Vert wrote the original code for Windows NT 3.1 that put the video screen back into text mode and the routines to put text on it (a...

   Windows blue screen,History     2013-07-24 09:25:16

  The new TV rating standard: Nielsen + Twitter

Recently, the market research company Nielsen and Twitter made an agreement to propose an new TV rating standard based on Twitter chats in the U.S television market in the fall of 2013, The new standard is called "Nielsen Twitter TV Rating", it will be the complement of Nielsen's traditional rating standard.Steve Hasker, president of Nielsen Global media advertising says "'Nielsen Twitter TV Rating" is a milestone in the entire television industry, Now not only television producers but also adve...

   Nelson, Twitter, TV rating     2012-12-18 12:56:18

  Guest Post from a CodeBoy: The Five Stages of Debugging

Being confronted with a serious and difficult-to-diagnose bug can be one of the most traumatic and stressful experiences of a professional programmer's career. Those who have been through such an ordeal rate the stress as on a par with that accompanying serious injury, divorce, or the death of a family member. Researchers who have studied the psychology of computer programming have lately constructed a framework to understand the stages through which the programmer's mind progresses as she...

   Debug,Steps,Stages     2012-05-01 06:39:38

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