web开发中，一个系统的普通需求也包括导出excel，一般采用POI做统计报表导出excel。

导出excel工具类：

    import java.io.FileOutputStream;        import java.io.IOException;        import java.io.OutputStream;        import java.util.List;        import java.util.Map;                import org.apache.poi.hssf.usermodel.HSSFCell;        import org.apache.poi.hssf.usermodel.HSSFRichTextString;        import org.apache.poi.hssf.usermodel.HSSFRow;        import org.apache.poi.hssf.usermodel.HSSFSheet;        import org.apache.poi.hssf.usermodel.HSSFWorkbook;                public class ExportExcel {                    private ExportExcel() {                super();            }                    public static void exportExcel(List<Object> list, Map<Integer, Long> map,                    String[] titles) throws IOException {                // 创建Excel文档                HSSFWorkbook hwb = new HSSFWorkbook();                // sheet 对应一个工作页                HSSFSheet sheet = hwb.createSheet("exportReport");                int colNum = titles.length;                // 创建第一行                HSSFRow firstrow = sheet.createRow(0);                HSSFCell[] firstcell = new HSSFCell[colNum];                for (int col = 0; col < colNum; col++) {                    firstcell[col] = firstrow.createCell(col);                    firstcell[col].setCellValue(new HSSFRichTextString(titles[col]));                }                        // 插入记录                int rowNum = map.size();                for (int i = 0; i < rowNum; i++) {                    // 从第二行开始                    HSSFRow row = sheet.createRow(i + 1);                    // 插入list中的字段                    for (int col = 0; col < colNum - 2; col++) {                        HSSFCell cell = row.createCell(col);                        cell.setCellValue(list.get(col).toString());                    }                    // 插入月份或日期                    row.createCell(colNum - 2).setCellValue(i + 1);                    // 插入总量                    row.createCell(colNum - 1).setCellValue(map.get(i + 1));                }                String fileName = titles[1].substring(0, 2);                if (colNum == 4) {                    fileName += list.get(0) + "_" + list.get(1) + "年_年度报表";                } else if (colNum == 5) {                    fileName += list.get(0) + "_" + list.get(1) + "年" + list.get(2)                            + "月_月度报表";                }                // 创建文件输出流，准备输出电子表格                OutputStream out = new FileOutputStream("../webapps/UsedMallMinaServer/files/"                        + fileName + ".xls");                hwb.write(out);                out.close();            }        }