Created attachment 24244 [details] failing test for HSSFCell#getRichStringCellValue() The contract of HSSFCell#getRichStringCellValue() specifies that "For formulaCells that are not string Formulas, we return empty String". What actually happens is that for numeric formula an IllegalArgumentException is thrown. (See attached test).
Documentation fixed in r951466 - it now reflects the long-standing behaviour I've also added a test that ensures that both xssf and hssf do the same thing in these cases