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Which design should I use?

jacob deiter
Ranch Hand

Joined: Apr 02, 2008
Posts: 580
In my class I have a condition statement which is very large

If (condtion1 ,condition 2,condtion4)
Set of statement

Else condtion 13
Set of statement

Condtion 5,condition 6,
Set of statement

Condtion 7 condtion 8 condtion 9

Set of statement

else condition 10 ,condition 11,condition 12

Set of statement


Since I every thing hard coded in If loop, I do not want to use it,

How I can replace the If loop with more generic stuff, which allow me to add more conditions and remove more conditions?
Gerardo Tasistro
Ranch Hand

Joined: Feb 08, 2005
Posts: 362
A switch statement would be helpful first approach if your conditions are numeric.

Are your conditions something like variableX=1 (a number)?

Will you be operating on the same data on your statements? That is, you could put that in a method who's parameters would be the same even if what each method does is different?
David Newton

Joined: Sep 29, 2008
Posts: 12617

As Gerardo said, the best answer for this may depend on the nature of the decisions you have to make.

Sometimes things like this can be encapsulated in a simple jump table (which in Java looks like a map of conditions => interface implementatons).
Hong Anderson
Ranch Hand

Joined: Jul 05, 2005
Posts: 1936
You could use Factory and Command patterns.
Use Factory to create a command object and call command.execute().

SCJA 1.0, SCJP 1.4, SCWCD 1.4, SCBCD 1.3, SCJP 5.0, SCEA 5, SCBCD 5; OCUP - Fundamental, Intermediate and Advanced; IBM Certified Solution Designer - OOAD, vUML 2; SpringSource Certified Spring Professional
kitarp Prabhu

Joined: Nov 12, 2008
Posts: 1
implementing Factory (Abstract Factory - if needed depending on the complexity) with Command pattern is good solution.
Laurent Leonard
Ranch Hand

Joined: May 15, 2001
Posts: 35
You could use the chain of responsability pattern (gof).
For each block in your if statement, you have a class that check if some conditions are validated, and if it's the case you can execute a statement.
Main -> Handler1 -> Handler2 -> Handler3 -> ... -> HandlerN

The advantages are
- different handlers could be triggered.
- Adding a new Handler is obvious.
- The condition are easier to read because no complex if statement.
- could be implemented in a way that if a statement is executed, the iteration on the chain is stopped

The disadvantage are
- be carefull of overlapping conditions (more than one statement is executed)
- testing could be difficult

Anand Kumar Singh

Joined: Oct 18, 2007
Posts: 22
Chain of Responsibility will be good for this scenario.

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