From: Charles Mills <cmills@...>
Date: 2004-10-29T01:52:09+09:00
Subject: Re: Rounding error, (100.0 * 9.95).to_i == 994

On Oct 28, 2004, at 9:12 AM, trans. (T. Onoma) wrote:
>
> How 'bout a good Money class ?
>

IMHO a good Money class would be priceless :)
There was an interesting article in Dr. Dobbs about a java money class  
a while back.  Below is the extract (registration required for full  
article).
Anyway if you do a lot of monetary calculations using floating point  
you can get some pretty hefty round off error... as you guys have been  
discussing.

-Charlie

www.ddj.com/documents/ddj0405i/
------------------------------------------------------------------------ 
---------
Java & Monetary Data

Dr. Dobb's Journal May 2004

A standalone class to tackle the problem

By John N. Armstrong
John is a senior partner and owner of Objective Logic L.L.P. in  
McKinney, Texas, a software consulting firm specializing in  
Java-centric architectures and solutions. He can be reached at  
john@objectivelogic.com.
Decimal Data

Java and J2EE have become ubiquitous as a platform of choice for  
creating robust enterprise e-commerce applications. Although these  
kinds of applications typically involve operations on monetary data  
(computing unit and extended prices, tax amounts, shipping costs, and  
so on), Java does not provide suitable mechanisms for dealing with this  
type of data.

Consequently, programmers are often faced with the problem of how to  
reliably represent, store, and manipulate monetary data. Obviously,  
when dealing with money, the importance of "getting it right" cannot be  
overstated. For these and similar reasons, an e-commerce application  
architecture should include a consistent mechanism for dealing with  
monetary data.

In this article, I'll examine some of the more common techniques for  
dealing with monetary data, and show why these techniques are less than  
optimal. I also present Money, a standalone Java class that addresses  
the problem of dealing with monetary data.
------------------------------------------------------------------------ 
-------------