java type parsing

[sammyinny01]

Hi,

I have a file database containing data values for several fields. The fields are specified in a separate meta data within the database in a format as:
fieldName, fieldType, fieldAggregationMethod
e.g., volume, long, sum
e.g., closePrice, float, last
e.g., numTrades, int, sum
The fieldType is always a basic type.

I need to read in these fields and allocate my arrays accordingly. Then I need to read the data values for each of these fields from a database, apply aggregation operation and return the values to the user.

I am thinking of setting up an aggregation method factory for the different aggregation operations.

But I am not sure how to handle field types. How do I allocate arrays based on the its specified type, return the right type from my functions, set type within the field, casting operation, etc. Is there a base class for the basic types in Java.
e.g, if I do something like:

if (type.equals("float"))
Object field1 = Float.valueOf(value);

Now how do I call my aggregation operation on field1?
something like

public Float sum(Float f1, Float f2) {
return f1 + f2;
}

I am thinking I need a wrapper around the existing java wrapper type classes and have those handle all these operations. Something like:

public interface Value {
public Object value();
public Object aggregate(Operation op);
}

public class DoubleValue implements Value {
Double d;
public Double(String s) {
// get d from s
}

public Object value() {
return d;
}

public Object aggregate(Operation op) {
return op.apply(d);
}
}

then have a factory construct the right type for me.

Is there an existing framework or example I could use for this? This looks like a common problem and I am sure there must be a good design pattern out there.

I want to avoid using reflection as much as possible as it is expensive, ugly, and error-prone.

Please share your experience and thoughts.

thanks,
Sam

 

[stefanwagner]

How many files do you have? How many types do they exist of?

Maybe you can create good fitting classes on the fly

class LFFI {
  long v1;
  float v2;
  float v3;
  int v4;
}

Sure your types are java-types (int, float, long)?

Another idea might be to use a sql-database, create insert statements, and do the aggregation by the database.

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[Diancecht]

Some ideas:

- You can consider using parseFloat instead of valueOf to get primitive types

- Are you actually using longs, ie, numbers bigger than 2,147,483,647.?


Cheers,
Dian