Java Apache POI simple read / write example

XLSXUpdaterExample.java

import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class XLSXUpdaterExample {

    private static final String DIRNAME =  "/tmp/";


    private XSSFWorkbook workbook;
    public XLSXUpdaterExample(String filename) throws IOException, InvalidFormatException {
        this.workbook = new XSSFWorkbook(new File(DIRNAME + filename));;
    }

    private void read() {
        XSSFCell cell = this.getMyCell();
        double nb = cell.getNumericCellValue();
        System.out.printf("February : %2f%n", nb);
    }
    private void update() throws IOException {
        double newValue = 5;
        this.getMyCell().setCellValue(newValue);

        FileOutputStream fos = new FileOutputStream(new  File(DIRNAME + "copy.xlsx"));
        workbook.write(fos);
        fos.close();
        System.out.printf("(after update): %2f%n", newValue);
    }

    private XSSFCell getMyCell() {
        return workbook.getSheetAt(0)
                .getRow(2)
                .getCell(1);
    }

    private void close() throws IOException {
        workbook.close();
    }


    public static void main(String[] args) throws IOException, InvalidFormatException {
        XLSXUpdaterExample xlsxParser = new XLSXUpdaterExample("simple.xlsx");
        xlsxParser.read();
        xlsxParser.update();
        xlsxParser.close();
        xlsxParser = new XLSXUpdaterExample("copy.xlsx");
        xlsxParser.read();
        xlsxParser.close();

    }
}