Which design should I use?

[jacob deiter]

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]

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]

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]

You could use Factory and Command patterns.
Use Factory to create a command object and call command.execute().

[kitarp Prabhu]

implementing Factory (Abstract Factory - if needed depending on the complexity) with Command pattern is good solution.

[Laurent Leonard]

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]

Chain of Responsibility will be good for this scenario.