Design Pattern and Anti Pattern

1. What is the Design Pattern ?

Those put typical problems occurred in designing a program in order , and collect to reuse.
( From e-Words (In Japanese))

1. Because we remember the name of the Design Patterns, it becomes easy to communicate with other people.
     In short, when you design the program and explain the idea of the design to other person , you don't need explain all.
     "There are names of the Pattern" is very important ¹.
2. We can understand the libraries further. (For example, Java libraries , boost(C++) , Qt(C++) and so on.)
     There are cases that libraries use the Design Patterns.
     For example , the InputStream class , the OutputStream class and these subclasses in java.io package. These classes use the Decorator Pattern.
   
3. You can use the Patterns , when you design a program.

1. When you apply the Design Patterns , you should confirm not only the merits but also demerits.
     For example , if the Design Patterns is applied in object-oriented , there is a case that the number of the class is increase.
     If in aspect-oriented, the increasing is less than in object-oriented.
2. You should confirm whether other person know the Design Patterns.
     I think that a few person understand perfectly. For example , many person only know the name or only know the 2 or 3 pattern. (but , I am too ...)

2. What is the Anti Pattern ?

  In software engineering, an anti-pattern (or antipattern) is a pattern that may be commonly used but is ineffective and/or counterproductive in practice.
( From Anti-pattern - Wikipedia, the free encyclopedia)

1. Lava Flow
     This pattern could occur when the updating speed of the research and development and technology. Programming source code is makeshift , document does not exist and there are unnecessary sources in many place.
     Those source codes , which are incomprehensible , could not modify. Because we can not modify for source codes that the specification are incomprehensible...
     But when you leave just as it is , those incomprehensible source codes increase.
   
2. Golden Hammer
     Trying to apply the accustomed technology , idea and so on to anything and everything.
     There are often this cases.
   
3. Cut and Paste Programming
     Because the specification is like , don't you copy and paste the source codes ?
     When you modify copied all source codes , aren't there cases that there are modification leak ?
   #Attention: In object-oriented , for example logging and access control and so on, there are cases that this pattern ocurr.
   
4. Functional Decomposition
     This pattern ocurr , when a person who don't understand object-oriented design a program.
     Don't he (she) think class is the collection of the function ?
     There are often this cases too.
   
5. Crush
     2 or more person are going to update the same datas.
     For example:
     PersonA show a data.
     PersonB show the same data. (Attention: PersonA don't know that PersonB show the data.)
     PersonA update and the data.
     PersonB update and the data too. ...? Where is the data updated by PersonA ? Go out ? And PersonA and PersonB don't notice that.
   
   

1. Because the names exist , the communication become easy.
   ( We don't need to explain all. )
2. We can decrease the mistakes when we design a program.
3. We can use for education. (Because there are the patterns that the beginner may often make a mistake. )
4. We can use for laughing materials of the communication to except software engineer. ( ... ? )

3. Reference

No.	Author	Book Name	ISBN
1	Craig Larman	Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and Iterative Development (3rd Edition)	978-0131489066
2	Bill Dudney , Stephen Asbury , Joseph K. Krozak , Kevin Wittkopf	J2EE AntiPatterns	978-0471146155