sheet.addMergedRegion(new Region(0,(short)0,0,(short)1)); 

sheet.addMergedRegion(new Region(0,(short)0,1,(short)0)); 

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);  
  
   /***这里是问题的关键，将这个工作簿写入到一个流中就可以输出相应的名字，这里需要写路径就ok了。 
   FileOutputStream fileOut = new FileOutputStream("workbook.xls");  
   wb.write(fileOut);  
   fileOut.close(); 
    **/ 
    
    
   /**第二种是输出到也面中的excel名称 
    * pName="栏目统计表"; 
 response.reset(); 
 response.setContentType("application/x-msdownload"); 
 response.setHeader("Content-Disposition","attachment; filename="+new String(pName.getBytes("gb2312"),"ISO-8859-1")+".xls"); 
 ServletOutputStream outStream=null; 
 
 try{ 
  outStream = response.getOutputStream(); 
  wb.write(outStream); 
 }catch(Exception e) 
 { 
  e.printStackTrace(); 
 }finally{ 
  outStream.close(); 
 } 
    * */ 
   System.out.print("OK");  
  } catch (Exception ex) {  
   ex.printStackTrace();  
  }  
  
 }  
  
}