[スニペット] Java8 ApchePOIでExcel1行目にフィルタを設定

import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.apache.poi.ss.util.CellRangeAddress;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class ExcelFilterSetter {

    public static void addFilterToFirstRow(String inputPath, String outputPath) throws IOException {
        try (FileInputStream fis = new FileInputStream(inputPath);
             Workbook workbook = new XSSFWorkbook(fis)) {

            Sheet sheet = workbook.getSheetAt(0); // 1枚目のシートを取得

            // 1行目のセル数（列数）を取得
            int lastColumn = sheet.getRow(0).getLastCellNum() - 1;

            if (lastColumn >= 0) {
                // フィルタの範囲を1行目に設定（例: A1〜C1）
                sheet.setAutoFilter(new CellRangeAddress(0, 0, 0, lastColumn));
            }

            // 保存
            try (FileOutputStream fos = new FileOutputStream(outputPath)) {
                workbook.write(fos);
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        try {
            ExcelFilterSetter.addFilterToFirstRow("input.xlsx", "output.xlsx");
            System.out.println("フィルタを追加しました！");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}