Java Excel 数据填充：使用 Apache POI 计算平均值并写入 Excel 文件

package org.example;

import java.io.FileInputStream; import java.io.FileOutputStream; import java.text.DecimalFormat; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date;

import org.apache.poi.ss.usermodel.Cell; import org.apache.poi.ss.usermodel.CellType; import org.apache.poi.ss.usermodel.Row; import org.apache.poi.ss.usermodel.Sheet; import org.apache.poi.ss.usermodel.Workbook; import org.apache.poi.ss.usermodel.WorkbookFactory;

public class test09 {

public static void main(String[] args) {
    String inputFile = 'input.xlsx';
    String outputFile = 'output.xlsx';
    try (Workbook workbook = WorkbookFactory.create(new FileInputStream(inputFile));
         FileOutputStream outputStream = new FileOutputStream(outputFile)) {
        Sheet sheet = workbook.getSheetAt(0);
        for (int i = 1; i <= sheet.getLastRowNum(); i++) {
            Row row = sheet.getRow(i);
            if (row != null) {
                Cell cell = row.getCell(1);
                if (cell != null && cell.getCellType() != CellType.BLANK) {
                    // do nothing
                } else {
                    double avg = calculateAverage(sheet, i, 1);
                    if (avg > 0) {
                        DecimalFormat df = new DecimalFormat('#.##');
                        if(cell == null){
                            cell = row.createCell(1);
                        }
                        cell.setCellValue(Double.parseDouble(df.format(avg)));
                    }
                }
            }
        }
        workbook.write(outputStream);
        System.out.println('Data filling completed.');
    } catch (Exception e) {
        e.printStackTrace();
    }
}

private static double calculateAverage(Sheet sheet, int rowIndex, int columnIndex) {
    double sum = 0;
    int count = 0;
    for (int i = rowIndex - 1; i >= 0; i--) {
        Row row = sheet.getRow(i);
        if (row != null) {
            Cell cell = row.getCell(columnIndex);
            if (cell != null && cell.getCellType() != CellType.BLANK) {
                sum += cell.getNumericCellValue();
                count++;
                break;
            }
        }
    }
    for (int i = rowIndex + 1; i <= sheet.getLastRowNum(); i++) {
        Row row = sheet.getRow(i);
        if (row != null) {
            Cell cell = row.getCell(columnIndex);
            if (cell != null && cell.getCellType() != CellType.BLANK) {
                sum += cell.getNumericCellValue();
                count++;
                break;
            }
        }
    }
    if (count > 0) {
        return sum / count;
    } else {
        return 0;
    }
}

private static Date parseDate(String dateString) {
    SimpleDateFormat dateFormat = new SimpleDateFormat('yyyy/MM/dd HH:mm');
    try {
        return dateFormat.parse(dateString);
    } catch (ParseException e) {
        e.printStackTrace();
        return null;
    }
}

}