Design a good filtering mechanism

[N.K.]

Hello, I'm trying to find a way to flexibly filter a column in a row
of data read from a file. I will have data type of that column, the
operation to be performed on it (like >, <, <= etc.) and the value to
compare it to stored in a database. If I'm to write it in a
procedural language it would be a big case statement like this: case
int
case <=
return (value <= compare value)
Can you think of a better way of doing it?
I was thinking about writing a separate class for each datatype with
methods for each operation. But then again I have to use case to
figure out the datatype and the operation to use. I could put
operators in a hash table with the method name as the value which
leads me to a next question. Can I invoke a method where method name
is a variable? For example myClass.varMeth odName where varMethodName
would contain a string with a real method name? And can I instantiate
a class with a variable, like instanceof(varc lassname) where
varclassname will hold the name of the real class?
I'd appreciate if you could suggest a way to implement my filtering
mechanism.
Thanks for your help.
N.K.

[N.K.]

Thank you so much. At least I see how to implement one solution now.
Can you think of a totally differnt way to implement this filtering?
I'm not sure my solution (even if it works ) is a great one.
Thanks for your tips though, I do appreciate your help.
N.K.
"Eric Olander" <eo************ *@earthlink.net > wrote in message news:<rA******* **************@ newsread1.prod. itd.earthlink.n et>...

Hi,
Your proposed solution is possible using the Class class (defined in
java.lang) and classes from the Reflection API (java.lang.refl ect).
For example, your instanceof(varc lassname) would look something like this:

instanceof(Clas s.forName(varcl assname)) where varclassname is a String.

To call a method whose name is in a String var, you'd do something like
this:

note: myObj is an instance of myClass

Method myMethod = myClass.getDecl aredMethod(varM ethodName, argTypes[]);
myMethod.invoke (myObj, args[]);

I don't know if this is the best solution to your problem, but it can be
done this way. Good Luck!

-Eric

"N.K." <na****@parkerg lobal.com> wrote in message
news:2d******** *************** ***@posting.goo gle.com...

Hello, I'm trying to find a way to flexibly filter a column in a row
of data read from a file. I will have data type of that column, the
operation to be performed on it (like >, <, <= etc.) and the value to
compare it to stored in a database. If I'm to write it in a
procedural language it would be a big case statement like this: case
int
case <=
return (value <= compare value)
Can you think of a better way of doing it?
I was thinking about writing a separate class for each datatype with
methods for each operation. But then again I have to use case to
figure out the datatype and the operation to use. I could put
operators in a hash table with the method name as the value which
leads me to a next question. Can I invoke a method where method name
is a variable? For example myClass.varMeth odName where varMethodName
would contain a string with a real method name? And can I instantiate
a class with a variable, like instanceof(varc lassname) where
varclassname will hold the name of the real class?
I'd appreciate if you could suggest a way to implement my filtering
mechanism.
Thanks for your help.
N.K.