Tutoriel pour extraire des données depuis une feuille Excel, les transformer et les sauvegarder : utilisation d'Apache POI

public class TestOutil  
{
    public static void main(String[] args) 
    {
        Tableau tab = new Tableau("paye.xls", "sheet1");
        Object corps[][] = tab.getBody();
        System.out.println(corps[10][2]);
        corps[10][2] = 5000;
        Object corps2[][] = tab.getBody();
        System.out.println(corps2[10][2]);
        tab.save();
    }
}

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.ss.usermodel.Cell;
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 Tableau 
{
    private String header[];
    private Object body[][];
    private String lastFileName = null;
    private String lastSheetName = null;
    
    public Tableau(String fileName, String sheetName)
    {
        try
        {
            this.setLastFileName(fileName);
            this.setLastSheetName(sheetName);
            FileInputStream file = new FileInputStream(fileName);
            Workbook workbook = WorkbookFactory.create(file);
            final Sheet sheet = workbook.getSheet(sheetName);
            int top = sheet.getFirstRowNum();
            int bottom = sheet.getLastRowNum();
            Row line = sheet.getRow(top);
            int start = line.getFirstCellNum();
            int end = line.getLastCellNum();    
            int length = end - start;
            while(length == 0)
            {
                top++;
                line = sheet.getRow(top);
                start = line.getFirstCellNum();
                end = line.getLastCellNum();    
                length = end - start;
            }
            int hight = bottom - top;
            this.header =  new String[length];
            this.body = new Object[hight][length];
            for (int i = 0; i < length; i++)
            {
                header[i] = line.getCell(start + i).getStringCellValue();    
            }
            
            for (int index = 0; index < hight; index++) 
            {
                line = sheet.getRow(index + top + 1);
                for (int i = 0; i < length; i++)
                {
                    Cell cellule = line.getCell(start + i);
                    switch (cellule.getCellType())
                    {
                        case Cell.CELL_TYPE_STRING : 
                            this.body[index][i] = cellule.getStringCellValue();
                            break;
                        case Cell.CELL_TYPE_BOOLEAN : 
                            this.body[index][i] = cellule.getBooleanCellValue();
                            break;
                        default :
                            this.body[index][i] = cellule.getNumericCellValue();
                    }
                }
            }
            workbook.close();
            file.close();
        }
         catch (InvalidFormatException | IOException e) 
        {
             e.printStackTrace();
        }
    }
    
    public void saveAs(String fileName, String sheetName)
    {
        try 
        {
            if (this.getLastFileName().compareTo(fileName) != 0)
                this.setLastFileName(fileName);
            if (this.getLastSheetName() != sheetName)
                this.setLastSheetName(sheetName);
            Workbook workbook = new HSSFWorkbook();
            Sheet sheet = workbook.createSheet(sheetName);
            Row row = sheet.createRow(0);
            for(int i = 0; i < this.getHeader().length; i++)
            {
                row.createCell(i).setCellValue(this.getHeader()[i]);
            }
            
            for (int index = 0; index < this.getBody().length; index++)
            {
                row = sheet.createRow(index + 1);
                for (int i = 0; i < this.getBody()[index].length; i++)
                {
                    String valeur = String.valueOf(this.getBody()[index][i]);
                    row.createCell(i).setCellValue(valeur);
                }
            }
            FileOutputStream fileOut = new FileOutputStream(fileName);
            workbook.write(fileOut);
            workbook.close();
            fileOut.close();
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
    }
    
    public void save()
    {
        this.saveAs(this.getLastFileName(), this.getLastSheetName());
    }
    
    public String[] getHeader() 
    {
        return this.header;
    }
    
    public Object[][] getBody() 
    {
        return this.body;
    }

    public String getLastFileName() {
        return this.lastFileName;
    }

    private void setLastFileName(String lastFileName) {
        this.lastFileName = lastFileName;
    }

    public String getLastSheetName() {
        return this.lastSheetName;
    }

    private void setLastSheetName(String lastSheetName) {
        this.lastSheetName = lastSheetName;
    }
}