Java POI 写Excel文件

Pom：

        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>5.2.3</version>
        </dependency>

写Excel文件：

package com.zkfr.test.utils;

//生成Excel文件

import com.zkfr.test.bo.HourData;
import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.ss.usermodel.HorizontalAlignment;
import org.apache.poi.ss.usermodel.VerticalAlignment;
import org.apache.poi.ss.util.CellRangeAddress;
import org.joda.time.DateTime;

import java.io.FileOutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Map;
import java.util.TreeMap;

public class ExcelUtil
{
    public static void exportOneHourDataExcelFile(String dir, String fileName, DateTime dataDate, TreeMap<DateTime, HourData> hourDataMap )
    {
        try
        {
            //判断文件是否存在
            Files.deleteIfExists(Paths.get(dir + fileName) );

            //
            HSSFWorkbook workbook = new HSSFWorkbook();
            HSSFSheet hssfSheet = workbook.createSheet();
            hssfSheet.setDefaultRowHeight( (short) 320 );
            hssfSheet.setDefaultColumnWidth( (short) 16 );

            //表头
            HSSFCellStyle hssfCellStyle = workbook.createCellStyle();
            hssfCellStyle.setAlignment( HorizontalAlignment.CENTER );
            hssfCellStyle.setVerticalAlignment( VerticalAlignment.CENTER );
            hssfCellStyle.setWrapText( true );

            //创建第一行: 创建行的单元格，从0开始
            HSSFRow hssfRow = hssfSheet.createRow( 0 );

            HSSFCell hssfCell = hssfRow.createCell(0);
            hssfCell.setCellValue("短期预测（T+3至T+7）");
            CellRangeAddress region = new CellRangeAddress(0, 0, 0, 6);
            hssfSheet.addMergedRegion(region);
            hssfCell.setCellStyle( hssfCellStyle );

            //创建第2行
            HSSFRow hssfRow1 = hssfSheet.createRow(1);
            //第0列
            HSSFCell cell10 = hssfRow1.createCell(0);
            cell10.setCellValue("日期: " + dataDate.toString( "yyyy-MM-dd" ) );
            cell10.setCellStyle( hssfCellStyle );
            //第1列
            HSSFCell cell11 = hssfRow1.createCell(1);
            cell11.setCellValue( "预测" );
            CellRangeAddress region11 = new CellRangeAddress(1, 1, 1, 3);
            hssfSheet.addMergedRegion( region11 );
            cell11.setCellStyle( hssfCellStyle );
            //第2列
            HSSFCell cell12 = hssfRow1.createCell(4);
            cell12.setCellValue( "实际" );
            CellRangeAddress region12 = new CellRangeAddress(1, 1, 4, 6);
            hssfSheet.addMergedRegion( region12 );
            cell12.setCellStyle( hssfCellStyle );

            //创建第3行
            HSSFRow hssfRow2 = hssfSheet.createRow( 2 );
            //第0列：时间
            HSSFCell cell20 = hssfRow2.createCell(0);
            cell20.setCellValue( "时间" );
            cell20.setCellStyle( hssfCellStyle );
            //第1列：发电量(kWh)
            HSSFCell cell21 = hssfRow2.createCell(1);
            cell21.setCellValue( "发电量(kWh)" );
            cell21.setCellStyle( hssfCellStyle );
            //第2列：平均风速
            HSSFCell cell22 = hssfRow2.createCell(2);
            cell22.setCellValue( "平均风速" );
            cell22.setCellStyle( hssfCellStyle );
            //第3列：功率
            HSSFCell cell23 = hssfRow2.createCell(3);
            cell23.setCellValue( "功率" );
            cell23.setCellStyle( hssfCellStyle );
            //第4列：发电量(kWh)
            HSSFCell cell24 = hssfRow2.createCell(4);
            cell24.setCellValue( "发电量(kWh)" );
            cell24.setCellStyle( hssfCellStyle );
            //第5列：平均风速
            HSSFCell cell25 = hssfRow2.createCell(5);
            cell25.setCellValue( "平均风速" );
            cell25.setCellStyle( hssfCellStyle );
            //第6列：功率
            HSSFCell cell26 = hssfRow2.createCell(6);
            cell26.setCellValue( "功率" );
            cell26.setCellStyle( hssfCellStyle );

            //创建第4行~第26行
            int nRowIndex = 3;
            for(Map.Entry<DateTime, HourData> hourDataEntry : hourDataMap.entrySet())
            {
                HSSFRow hssfRow3 = hssfSheet.createRow( nRowIndex );

                //第0列：时间
                HSSFCell cell30 = hssfRow3.createCell(0);
                cell30.setCellValue( hourDataEntry.getKey().toString( "HH:mm" ) );
                cell30.setCellStyle( hssfCellStyle );

                //第1列：发电量(kWh)
                HSSFCell cell31 = hssfRow3.createCell(1);
                cell31.setCellValue( String.format("%.2f", hourDataEntry.getValue().getForecastElectricity()) );
                cell31.setCellStyle( hssfCellStyle );

                //第2列：平均风速
                HSSFCell cell32 = hssfRow3.createCell(2);
                cell32.setCellValue( String.format("%.2f", hourDataEntry.getValue().getForecastWindSpeed()) );
                cell32.setCellStyle( hssfCellStyle );

                //第3列：功率
                HSSFCell cell33 = hssfRow3.createCell(3);
                cell33.setCellValue(String.format("%.2f", hourDataEntry.getValue().getForecastPower()) );
                cell33.setCellStyle( hssfCellStyle );

                //第4列：发电量(kWh)
                HSSFCell cell34 = hssfRow3.createCell(4);
                cell34.setCellValue( String.format("%.2f", hourDataEntry.getValue().getRealElectricity()) );
                cell34.setCellStyle( hssfCellStyle );

                //第5列：平均风速
                HSSFCell cell35 = hssfRow3.createCell(5);
                cell35.setCellValue( String.format("%.2f", hourDataEntry.getValue().getRealWindSpeed()) );
                cell35.setCellStyle( hssfCellStyle );

                //第6列：功率
                HSSFCell cell36 = hssfRow3.createCell(6);
                cell36.setCellValue( String.format("%.2f", hourDataEntry.getValue().getRealPower()) );
                cell36.setCellStyle( hssfCellStyle );

                nRowIndex = nRowIndex+1;
            }

            //写入文件
            FileOutputStream fileOutputStream = new FileOutputStream( dir + fileName );
            workbook.write( fileOutputStream );
            workbook.close();
            fileOutputStream.close();
        }
        catch( Exception e )
        {
            e.printStackTrace();
        }
    }
}