Duplicate code smell

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Duplicated code is the smelliest of the code smells. The book ''Refactoring'' [[Martin Fowler 1999]] states that: "If you see the same code structure in more than one place, you can be sure that your program will be better if you find a way to unify them." [[Martin Fowler 1999]] states that the simplest duplicated code problem is when you have the same expression in two methods of the same class.
 
Duplicated code is the smelliest of the code smells. The book ''Refactoring'' [[Martin Fowler 1999]] states that: "If you see the same code structure in more than one place, you can be sure that your program will be better if you find a way to unify them." [[Martin Fowler 1999]] states that the simplest duplicated code problem is when you have the same expression in two methods of the same class.
  
== Refactoring ==
+
It is worth noting that occasionally what appears to be duplicated code is actually two different behaviours that will eventually evolve in different directions.
  
The best way to fix this bad code smell is to use [[Extract Method]] as shown below.
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'''Apply [[Extract Method]]'''
  
        printOwing() {
 
                printBanner();
 
       
 
                //print details
 
                System.out.println ("name: " + _name);
 
                System.out.println ("amount " + getOutstanding());
 
        }
 
 
becomes
 
 
        void printOwing() {
 
                printBanner();
 
                printDetails(getOutstanding());
 
        }
 
 
        void printDetails (double outstanding) {
 
                System.out.println ("name: " + _name);
 
                System.out.println ("amount " + outstanding);
 
        }
 
  
 
== See also ==
 
== See also ==
 +
* [[Extract Method]]
 
* [[Don't repeat yourself]]
 
* [[Don't repeat yourself]]
 
* [[Once and only once]]
 
* [[Once and only once]]
 
* [[Code smells]]
 
* [[Code smells]]
 
* [[Refactoring]]
 
* [[Refactoring]]
 +
 +
{{Template:CodeSmells}}
 +
 +
[[Category:Code smells]]

Latest revision as of 03:10, 25 November 2010

Duplicated code is the smelliest of the code smells. The book Refactoring Martin Fowler 1999 states that: "If you see the same code structure in more than one place, you can be sure that your program will be better if you find a way to unify them." Martin Fowler 1999 states that the simplest duplicated code problem is when you have the same expression in two methods of the same class.

It is worth noting that occasionally what appears to be duplicated code is actually two different behaviours that will eventually evolve in different directions.

Apply Extract Method


See also


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