POI生成excel表格，如何合并单元格

Java代码
import java.io.FileOutputStream;   
import java.io.IOException;   
  
import org.apache.poi.hssf.usermodel.HSSFCell;   
import org.apache.poi.hssf.usermodel.HSSFCellStyle;   
import org.apache.poi.hssf.usermodel.HSSFRow;   
import org.apache.poi.hssf.usermodel.HSSFSheet;   
import org.apache.poi.hssf.usermodel.HSSFWorkbook;   
import org.apache.poi.hssf.util.Region;   
  
public class ExcelTest {   
  
    /**  
     * @param args  
     */  
    public static void main(String[] args) throws IOException {   
  
        try {   
            HSSFWorkbook wb = new HSSFWorkbook();   
            HSSFSheet sheet = wb.createSheet("new   sheet");   
            HSSFCellStyle style = wb.createCellStyle(); // 样式对象   
  
            style.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);// 垂直   
            style.setAlignment(HSSFCellStyle.ALIGN_CENTER);// 水平   
            HSSFRow row = sheet.createRow((short) 0);   
            HSSFRow row2 = sheet.createRow((short) 1);   
  
            sheet.addMergedRegion(new Region(0, (short) 0, 1, (short) 0));   
            HSSFCell ce = row.createCell((short) 0);   
            ce.setEncoding(HSSFCell.ENCODING_UTF_16);// 中文处理   
            ce.setCellValue("项目\\日期"); // 表格的第一行第一列显示的数据   
            ce.setCellStyle(style); // 样式，居中   
            int num = 0;   
            for (int i = 0; i < 9; i++) { // 循环9次，每一次都要跨单元格显示   
                // 计算从那个单元格跨到那一格   
                int celln = 0;   
                int celle = 0;   
                if (i == 0) {   
                    celln = 0;   
                    celle = 1;   
                } else {   
                    celln = (i * 2);   
                    celle = (i * 2 + 1);   
                }   
                // 单元格合并   
                // 四个参数分别是：起始行，起始列，结束行，结束列   
                sheet.addMergedRegion(new Region(0, (short) (celln + 1), 0,   
                        (short) (celle + 1)));   
                HSSFCell cell = row.createCell((short) (celln + 1));   
                cell.setCellValue("merging" + i); // 跨单元格显示的数据   
                cell.setCellStyle(style); // 样式   
                // 不跨单元格显示的数据，如：分两行，上一行分别两格为一格，下一行就为两格，“数量”，“金额”   
                HSSFCell cell1 = row2.createCell((short) celle);   
                HSSFCell cell2 = row2.createCell((short) (celle + 1));   
                cell1.setEncoding(HSSFCell.ENCODING_UTF_16);   
                cell1.setCellValue("数量");   
                cell1.setCellStyle(style);   
                cell2.setEncoding(HSSFCell.ENCODING_UTF_16);   
                cell2.setCellValue("金额");   
                cell2.setCellStyle(style);   
                num++;   
            }   
  
            // 在后面加上合计百分比   
  
            // 合计 在最后加上，还要跨一个单元格   
            sheet.addMergedRegion(new Region(0, (short) (2 * num + 1), 0,   
                    (short) (2 * num + 2)));   
            HSSFCell cell = row.createCell((short) (2 * num + 1));   
            cell.setEncoding(HSSFCell.ENCODING_UTF_16);   
            cell.setCellValue("合计");   
            cell.setCellStyle(style);   
            HSSFCell cell1 = row2.createCell((short) (2 * num + 1));   
            HSSFCell cell2 = row2.createCell((short) (2 * num + 2));   
            cell1.setEncoding(HSSFCell.ENCODING_UTF_16);   
            cell1.setCellValue("数量");   
            cell1.setCellStyle(style);   
            cell2.setEncoding(HSSFCell.ENCODING_UTF_16);   
            cell2.setCellValue("金额");   
            cell2.setCellStyle(style);   
  
            // 百分比 同上   
            sheet.addMergedRegion(new Region(0, (short) (2 * num + 3), 0,   
                    (short) (2 * num + 4)));   
            HSSFCell cellb = row.createCell((short) (2 * num + 3));   
            cellb.setEncoding(HSSFCell.ENCODING_UTF_16);   
            cellb.setCellValue("百分比");   
            cellb.setCellStyle(style);   
            HSSFCell cellb1 = row2.createCell((short) (2 * num + 3));   
            HSSFCell cellb2 = row2.createCell((short) (2 * num + 4));   
            cellb1.setEncoding(HSSFCell.ENCODING_UTF_16);   
            cellb1.setCellValue("数量");   
            cellb1.setCellStyle(style);   
            cellb2.setEncoding(HSSFCell.ENCODING_UTF_16);   
            cellb2.setCellValue("金额");   
            cellb2.setCellStyle(style);   
  
            FileOutputStream fileOut = new FileOutputStream("workbook.xls");   
            wb.write(fileOut);   
            fileOut.close();   
            System.out.print("OK");   
        } catch (Exception ex) {   
            ex.printStackTrace();   
        }   
  
    }   
  
}