We had an opportunity to write unit test cases for some legacy code and it was tough job. Find it very difficult especially when so much singletons are used on code base.
We should really use it only when its required. The following article forces that.
Refer:
http://www.ibm.com/developerworks/webservices/library/co-single.html
Google has singleton detector for sometime now, that can be very useful if you need to analyze the code base without source code.
Refer:
http://code.google.com/p/google-singleton-detector/
Sunday, October 18, 2009
Law of Demeter and violations.
Law of Demeter - "Only talk to your immediate friends"
An object should avoid invoking methods of a member object returned by another method. In Java,the law can be stated simply as "use only one dot". That is, the code "a.b.Method()" breaks the law where "a.Method()" does not.
Violations:
With the SOA applications rising up these days, its very difficult to draw a line to what extend one can violate this law.
One way to create appropriate facades to wrap the internal extensions, however it just looks like for the sack of the (LoD) Law of Demeter and in fact slows one down on development.
Lot of third party libraries does not seem to care about the principle at all.Everyday we use these libraries,needless to say with lot of dots,and when we get "NullPointerException", the deguggin goes crazy.
We should realize the value of LoD, at least from unit testing perspective and its very hard to test the piece of the code that violates the LoD to larger extend.
Strongly feel, developers or API Architects should take LoD into account when they design plugin/libraries.
An object should avoid invoking methods of a member object returned by another method. In Java,the law can be stated simply as "use only one dot". That is, the code "a.b.Method()" breaks the law where "a.Method()" does not.
Violations:
With the SOA applications rising up these days, its very difficult to draw a line to what extend one can violate this law.
One way to create appropriate facades to wrap the internal extensions, however it just looks like for the sack of the (LoD) Law of Demeter and in fact slows one down on development.
Lot of third party libraries does not seem to care about the principle at all.Everyday we use these libraries,needless to say with lot of dots,and when we get "NullPointerException", the deguggin goes crazy.
We should realize the value of LoD, at least from unit testing perspective and its very hard to test the piece of the code that violates the LoD to larger extend.
Strongly feel, developers or API Architects should take LoD into account when they design plugin/libraries.
Saturday, October 3, 2009
Challenge your Math Skill
Visit http://mathschallenge.net/ and try to solve a problem or two.
Happy solving!
Happy solving!
Are you ready to prove your programming expertise?
Following are few of the sites which offer wide variety of challenges for programmers of most of the languages and reward them.
Code Golf
When: Ongoing, new challenges posted sporadically
Languages: Perl, PHP, Python, Ruby
How it works: Based on the original perl golf, Code Golf allows you to show off your code-fu by solving coding problems using the least number of keystrokes. The challenges cover a nice mix of topics; example challenges are 99 Bottles of Beer, Tower of Hanoi, The Game of Life, and converting Roman numerals to base 10 integers.
How to win: Submit your code, and if it passes the challenge test cases, your entry is scored according to the number of characters. Win bragging rights by appearing on the overall leader board or the leader board for each problem.
UVa
When: New contests every month
Languages: C, Java, C++, Pascal
How it works: Each contest consists of anywhere between 3 and 10 problems. The problem sets demand quick thinking and a good computer science background with solid knowledge of algorithms, data structures, and mathematics. Common themes are palindromes, primes, and graphs. Check out the extensive contest archives for practice.
How to win: Contests are timed and usually last several hours, so have some coffee and brain food nearby. Submit code for each problem to the automatic tester when it’s finished. Contestants are ranked by the number of correct solutions and ties broken by the time taken to complete the challenge.
Mindcipher
When: Ongoing
Languages: Logic
How it works: Mindcipher is a social repository of the world’s greatest brain teasers, logical puzzles and mental challenges. No programming required, just logic and common sense. Some of the problems are taken from Google and Microsoft interviews so brush up your interview skills while having some fun. Categories of brain teasers are mathematics, physics, at the campfire, logical, riddles, lateral thinking, optical illusions, and general. Each puzzle is ranked according to difficulty and members can vote up favorite puzzles.
How to win: Answers are provided for each brain teaser, so there isn’t really any winning involved.
Project Euler
When: Ongoing
Languages: All languages
How it works: Each problem is designed to be solved by some combination of mathematical insight and algorithm design. Problems build on one another, getting progressively harder, so its a great way to keep your math skills fresh. After solving a problem you are given access to the forum containing algorithm discussion and solutions in a wide variety of languages, so Project Euler is a nice way to learn a new language.
How to win: Submit correct answers to the most recent 25 problems to earn a spot on the venerable Eulerians list. Or solve more than 200 puzzles to reach level 5.
TopCoder
When: Weekly rated competitions, and practice rooms that are always open
Languages: Java, C++, C#, Visual Basic
How it works: In TopCoder’s algorithm competitions, you have a set amount of time to complete the problem set (usually an hour). Code is normally developed inside TopCoder; there are multiple plugins that provide an IDE within your browser.
TC also holds “competitions” in bug fixing and component design, development, and assembly. These competitions are actually work developed on a speculative basis for companies who have outsourced development to TC, with “prizes” given to work with the best ratings.
How to win: For the algorithm competitions, develop, test, and submit solutions to the 3 problems in the set during the submission widow. After a 5 minute intermission you can view competitors’ code and challenge it by giving a test case that you believe will break the submission. Scoring is based on problem difficulty, time to complete the problem, results of the challenge round, and results of automated testing.
The International Obfuscated C Code Contest
When: Yearly (but currently on hiatus after 19 competitions)
Languages: C
How it works: Submit your most obfuscated ANSI C code. Each contest has a list of rules concerning code size, the build process, compile dependencies, etc. However, legal abuse of the rules is somewhat encouraged. Winners from previous years have all used nefariously tricky obfuscation.
How to win: Submissions are judged by a panel of judges based on how obfuscated the code is. Originality is important in both the type of obfuscation used and the purpose of the code.
Enjoy Programming!!!
Code Golf
When: Ongoing, new challenges posted sporadically
Languages: Perl, PHP, Python, Ruby
How it works: Based on the original perl golf, Code Golf allows you to show off your code-fu by solving coding problems using the least number of keystrokes. The challenges cover a nice mix of topics; example challenges are 99 Bottles of Beer, Tower of Hanoi, The Game of Life, and converting Roman numerals to base 10 integers.
How to win: Submit your code, and if it passes the challenge test cases, your entry is scored according to the number of characters. Win bragging rights by appearing on the overall leader board or the leader board for each problem.
UVa
When: New contests every month
Languages: C, Java, C++, Pascal
How it works: Each contest consists of anywhere between 3 and 10 problems. The problem sets demand quick thinking and a good computer science background with solid knowledge of algorithms, data structures, and mathematics. Common themes are palindromes, primes, and graphs. Check out the extensive contest archives for practice.
How to win: Contests are timed and usually last several hours, so have some coffee and brain food nearby. Submit code for each problem to the automatic tester when it’s finished. Contestants are ranked by the number of correct solutions and ties broken by the time taken to complete the challenge.
Mindcipher
When: Ongoing
Languages: Logic
How it works: Mindcipher is a social repository of the world’s greatest brain teasers, logical puzzles and mental challenges. No programming required, just logic and common sense. Some of the problems are taken from Google and Microsoft interviews so brush up your interview skills while having some fun. Categories of brain teasers are mathematics, physics, at the campfire, logical, riddles, lateral thinking, optical illusions, and general. Each puzzle is ranked according to difficulty and members can vote up favorite puzzles.
How to win: Answers are provided for each brain teaser, so there isn’t really any winning involved.
Project Euler
When: Ongoing
Languages: All languages
How it works: Each problem is designed to be solved by some combination of mathematical insight and algorithm design. Problems build on one another, getting progressively harder, so its a great way to keep your math skills fresh. After solving a problem you are given access to the forum containing algorithm discussion and solutions in a wide variety of languages, so Project Euler is a nice way to learn a new language.
How to win: Submit correct answers to the most recent 25 problems to earn a spot on the venerable Eulerians list. Or solve more than 200 puzzles to reach level 5.
TopCoder
When: Weekly rated competitions, and practice rooms that are always open
Languages: Java, C++, C#, Visual Basic
How it works: In TopCoder’s algorithm competitions, you have a set amount of time to complete the problem set (usually an hour). Code is normally developed inside TopCoder; there are multiple plugins that provide an IDE within your browser.
TC also holds “competitions” in bug fixing and component design, development, and assembly. These competitions are actually work developed on a speculative basis for companies who have outsourced development to TC, with “prizes” given to work with the best ratings.
How to win: For the algorithm competitions, develop, test, and submit solutions to the 3 problems in the set during the submission widow. After a 5 minute intermission you can view competitors’ code and challenge it by giving a test case that you believe will break the submission. Scoring is based on problem difficulty, time to complete the problem, results of the challenge round, and results of automated testing.
The International Obfuscated C Code Contest
When: Yearly (but currently on hiatus after 19 competitions)
Languages: C
How it works: Submit your most obfuscated ANSI C code. Each contest has a list of rules concerning code size, the build process, compile dependencies, etc. However, legal abuse of the rules is somewhat encouraged. Winners from previous years have all used nefariously tricky obfuscation.
How to win: Submissions are judged by a panel of judges based on how obfuscated the code is. Originality is important in both the type of obfuscation used and the purpose of the code.
Enjoy Programming!!!
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