import java.io.*;
import jxl.*;
import java.util.*;

class  ConvertExcelToCSV
{
  public static void main(String[] args) 
  {
    try
    {
      String filename = "C:/data.xls";
      WorkbookSettings ws = new WorkbookSettings();
      ws.setLocale(new Locale("en", "EN"));
      Workbook w = Workbook.getWorkbook(new File(filename),ws);

      File f = new File("c:/new.csv");
      OutputStream os = (OutputStream)new FileOutputStream(f);
      String encoding = "UTF8";
      OutputStreamWriter osw = new OutputStreamWriter(os, encoding);
      BufferedWriter bw = new BufferedWriter(osw);


      for (int sheet = 0; sheet < w.getNumberOfSheets(); sheet++)
      {
        Sheet s = w.getSheet(sheet);

        bw.write(s.getName());
        bw.newLine();

        Cell[] row = null;

        for (int i = 0 ; i < s.getRows() ; i++)
        {
          row = s.getRow(i);

          if (row.length > 0)
          {
            bw.write(row[0].getContents());
            for (int j = 1; j < row.length; j++)
            {
              bw.write(',');
              bw.write(row[j].getContents());
            }
          }
          bw.newLine();
        }
      }
      bw.flush();
      bw.close();
    }
    catch (Exception e)
    {
      System.err.println(e);
    }

  }
}

For the above code, you need JExcel Api,

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