Thank you for considering Aspose APIs.
Please try setting the license in your application as follow and see if you get the “Evaluation” worksheet in the resultant file.
com.aspose.cells.License license = new com.aspose.cells.License();
com.aspose.cells.Workbook workbook = new com.aspose.cells.Workbook();
Moreover, the latest version of Aspose.Cells for Java is 8.3.0. In case you get the Evaluation worksheet in the resultant spreadsheet with your current version of the API, we would request you to try the case by upgrading the API to latest version 8.3.0. You can download the latest version from the below link.