Question

For a Java application that drags data together from some sources and does some calculation itself, we want to offer users the possibility to use their own format strings, and would prefer the format string syntax they know from Excel (e. g. "$ "#,###.,0) which happens to be the same used in .net and Analysis Services.

The closest thing to use that I found in Java is DecimalFormat which lacks some of the features (e. g. thousands and millions formatting by putting the thousands separator at the end, the floating point numbers NaN and infinity are displayed differently, etc., and probably depending on locale, there will be some additional small differences.

For now, just the numeric formatting would suffice. Maybe date and string formatting will become a requirement in future.

Is there a library, or would we have to develop that ourselves?

I cannot imagine we are the only ones who have this issue.

POI as suggested by Noel M does not seem to offer a solution. Any other ideas?

Answer 1

Is there a library, or would we have to develop that ourselves?

Check ExtenXLS, the Java Spreadsheet SDK, or its open source version OpenXLS (under GPLv.3). About OpenXLS:

OpenXLS is the open-source version of
ExtenXLS — the leading Java
Spreadsheet SDK.

OpenXLS is the no-risk way to embed
advanced Java spreadsheet
functionality in your applications.

With the same industrial-strength code
as ExtenXLS3, OpenXLS is a rock-solid
performer which gives your Java
applications the spreadsheet
functionality your users demand — and
then some!

Give your users business intelligence
applications and reports in the format
they know and love, complete with
Charts, images, VB code, and all of
the features of Excel intact.

I had a quick look at the API and found this FormatHandle#convertFormatString(String) that converts an Excel-style format string to a Java Format string.

I don’t know if it will match your constraints but it’s definitely a serious product.