When trying to create a sheet with an invalid name (e.g. having a (') at the beginning or the end) with HSSF, then this creates an exception like "Invalid sheet name ''Invalid Sheet Name'. Sheet names must not begin or end with (').". I would consider this as expected and reasonable behaviour. With XSSF, however, no such exception is produced. But when trying to open the created Excel file, Excel shows a dialog box saying that non-readable content has been found and asks whether Excel should recover the content. I would except HSSF and XSSF to behave the same way and throw an exception when trying to create a sheet with an invalid name. The above behaviour can be reproduced by using the workbook.createSheet function. OS: Windows 7 64bit POI: 3.7-beta2 Java: 1.6.0_20 64bit
Fixed in r992629 Regards, Yegor