Java creates excel file but i am not able to open the file

Question

i have this java code which should create xls file but the file cannot be open. Excel says the format of the file is not valid. I added all librairie for generating xlsx file, am i missing something here. Any help please Thank you

Here is the code:

import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import com.google.common.collect.Table.Cell;
import jxl.Workbook;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.concurrent.TimeUnit;           

XSSFWorkbook workbook = new XSSFWorkbook();
XSSFSheet sheet = workbook.createSheet("Trade");
Map < String, Object[] > data = new TreeMap < String, Object[] > ();
data.put("1", new Object[] {
    "Code"
});

Set < String > keyset = data.keySet();
int rownum = 0;
for (String key: keyset) {
    Row row = sheet.createRow(rownum++);
    Object[] objArr = data.get(key);
    int cellnum = 0;
    for (Object obj: objArr) {
        org.apache.poi.ss.usermodel.Cell cell = row.createCell(cellnum++);
        if (obj instanceof String)
            cell.setCellValue((String) obj);
        else if (obj instanceof Integer)
            cell.setCellValue((Integer) obj);
    }
}
try {
    FileOutputStream out = new FileOutputStream(new 
File("C:\\temp\\demo.xlsx"));
    workbook.write(out);
    out.close();
    System.out.println("success");
} catch (Exception e) {
    e.printStackTrace();
}

Answer 1

Apache POI is notably disagreeable with newer excel filetypes. Changing your file extension to .xls should work