Newbie question on using an Interface

Question

I am something of an advanced beginner, one of those guys who can write simple stuff and maintain code but always have a bunch of questions.
I am able to use an interface in a simple example shown below:
import java.util.*;
import java.text.*;
public class ClassTest
public static void main(String args[])
new ClassTest();
ClassTest()
IfcPrintClass dao=null;
try{ dao = (IfcPrintClass)Class.forName("ThatPrintClass").newInstance();
}catch (Exception e) {};
System.out.println(dao.PrintTheClass());
try{ dao = (IfcPrintClass)Class.forName("ThisPrintClass").newInstance();
}catch (Exception e) {};
System.out.println(dao.PrintTheClass());
} //end ClassTest
What I am wondering is how do I instantiate (hope that's the right terminology) a class via an interface when the class has parameters? The API and other examples, at least ones I've seen, don't spell this out.
I have to maintain a piece of code (ie, I didn't write it) with a class defined below. We need to create an interface for this class to implement so we can re-use this and similarly named classes for other projects. For example, the below listed class is to handle our SQL I/O, but naturally the db handling will varying from project to project. I want to be able to dynamically load a class within my code and pass the class name and directory into the package via ARGS (again, hope I'm using terminology correctly). I am trying to figure out how to adapt my above example to the below class instantiation, but cannot figure out how to pass the parameter along with it. I do know how to create an interface. In the below example "errorModule" is another class that handles our error and information logging, but is abstract enough that it will not change project to project. The "insertLoader" method is a sample method that the DAOLoader class will do, as is "isConnected".
dao = new DAOLoader(errorModule);
if(dao == null || !dao.isConnected()) //connection failed
// handle this error
else
dbAlreadyFailed = false;
if(firstDatabaseConnection)
dao.insertLoader();
thanks in advance, and hope you can help.

Answer 1

As requested, here is the code I posted using code tags,and I'll do this in the future:
ClassTest.java:
import java.util.*;
import java.text.*;
public class ClassTest
public static void main(String args[])
new ClassTest();
ClassTest()
IfcPrintClass dao=null;
try{ dao = (IfcPrintClass)Class.forName("ThatPrintClass").newInstance();
}catch (Exception e) {};
System.out.println(dao.PrintTheClass());
try{ dao = (IfcPrintClass)Class.forName("ThisPrintClass").newInstance();
}catch (Exception e) {};
System.out.println(dao.PrintTheClass());
} //end ClassTestMy actual code:
dao = new DAOLoader(errorModule);
if(dao == null || !dao.isConnected()) //connection failed
// handle this error
else
dbAlreadyFailed = false;
if(firstDatabaseConnection)
dao.insertLoader();
}IfcPrintClass.java:
public interface IfcPrintClass
String PrintTheClass();
}ThatPrintClass.java:
public class ThatPrintClass implements IfcPrintClass
public String PrintTheClass()
return "That";
}Then I have a class ThisPrintClass:
public class ThisPrintClass implements IfcPrintClass
public String PrintTheClass()
return "This";
}