In r1721930 the return value of org.apache.poi.ss.usermodel.Workbook.getNumCellStyles() (and related classes) was changed from short to int. This breaks binary compatibility of the interface with previous releases of POI. Code calling this method now throws an exception: java.lang.NoSuchMethodError: org/apache/poi/ss/usermodel/Workbook.getNumCellStyles()S
This change was intentional to unify XSSF and HSSF while avoiding overflow bugs due to lack of unsigned datatypes. As this is a better nd not a setter, there was no way for us to make this change gradually without breaking binary compatibility. This doesn't break source compatibility since shorts can be implicitly cast to ints. You unfortunately may need to recompile your project.