This code converts an Excel spreadsheet to a comma delimited (.csv) file using Apache POI.
It works for Excel 97-2003 Workbook (.xls) and Excel Workbook (.xlsx). It does not work for the XML Spreadsheet 2003 (.xml) format produced by BIRT.
package mypackage;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;