avoiding if else

[sumit919]

My project generates DDL Script for an ER Model for multiple database vendors. I will be needing create and alter statements for various database objects. I want to avoid using if else and use some good OO Practices to design this. Can anyone help. I hope i am clear with my question.

[Norm]

I want to avoid using if else

Can you explain why? The if statement is one of the standard ways of testing conditions and controlling execution flow.
There are not many programs that do not use if statements.

[Tolls]

You'll need one somewhere to differentiate the target database, but after that just create a database specific concrete version of some database interface.
A factory method would be a reasonable approach:

public DatabaseBuilder getDatabaseBuilder(String dbname) { // or enum or whatever, this is not cut 'n' paste code here
    if (dbname.equals("MYSQL")) return new MySQLDatabaseBuilder();
    if (dbname.equals("Oracle")) return new OracleDatabaseBuilder();
// and so on
}

then use that returned DatabaseBuilder reference.
In fact, a singleton set up would make some sense if, on a single execution, this was run against only a single database.

[sumit919]

Currently we use if else only. But when new databases are added I have to test code for the previously supported databases also. And the use of if else makes that code highly error prone and absolutely unreadable. Its partially also because of some poor programming practices being adopted by our team. When i started reading about actually using interfaces and inheritance I thought this can be an area in our code where we can use inheritance or interfaces. Or any good design pattern.

[sumit919]

Yes I was also thinking on the same lines. If I am not wrong this is something similar to the Strategy design pattern (The first DP mentioned in Head First Design Patterns). But I was not able to understand the singleton thing u mentioned. Thanks for the help. :)

[Tolls]

Depends on how your system works, but if it's run against a single database at any one time then you only need one of those DatabaseBuilders. That implies a singleton.
Except (thinking about it) it could be a bit awkward passing in the parameter for which database to use...