Excel to HTML Table Converter in Java

import java.awt.*;
import java.io.*;
import java.util.Iterator;

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.*;
import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.ss.util.*;
import org.apache.poi.hssf.util.*;
import org.apache.poi.ss.usermodel.Row.MissingCellPolicy;

public class test12 {
    public static void main(String[] args) throws Exception {
        String excelFilePath = "input.xlsx";
        File inputFile = new File(excelFilePath);

        //Get the workbook instance for XLSX file
        Workbook workbook = null;
        if (excelFilePath.endsWith("xlsx")) {
            workbook = new XSSFWorkbook(new FileInputStream(inputFile));
        } else if (excelFilePath.endsWith("xls")) {
            workbook = new HSSFWorkbook(new FileInputStream(inputFile));
        }

        //Get the first sheet from the workbook
        Sheet sheet = workbook.getSheetAt(0);

        //Create a new HTML table
        StringBuffer htmlTable = new StringBuffer("<table style=\"border-collapse: collapse; width: 100%;\">");

        //Iterate through each rows from first sheet
        Iterator<Row> rowIterator = sheet.iterator();
        while (rowIterator.hasNext()) {
            Row row = rowIterator.next();

            //Create a new HTML table row
            htmlTable.append("<tr>");

            //Iterate through each columns from the row
            Iterator<Cell> cellIterator = row.cellIterator();
            while (cellIterator.hasNext()) {
                Cell cell = cellIterator.next();

                //Create a new HTML table cell
                htmlTable.append("<td style=\"border: 1px solid #ddd; padding: 8px;\">");

                //Get the cell value and append to HTML table cell
                switch (cell.getCellType()) {
                    case STRING:
                        htmlTable.append(cell.getStringCellValue());
                        break;
                    case NUMERIC:
                        if (DateUtil.isCellDateFormatted(cell)) {
                            htmlTable.append(cell.getDateCellValue().getTime());
                        } else {
                            htmlTable.append(cell.getNumericCellValue());
                        }
                        break;
                    case BOOLEAN:
                        htmlTable.append(cell.getBooleanCellValue());
                        break;
                    case FORMULA:
                        htmlTable.append(cell.getCellFormula());
                        break;
                    case BLANK:
                        htmlTable.append("");
                        break;
                    default:
                        htmlTable.append(cell);
                }

                //Close the HTML table cell
                htmlTable.append("</td>");
            }

            //Close the HTML table row
            htmlTable.append("</tr>");
        }

        //Close the HTML table
        htmlTable.append("</table>");

        //Close the workbook
        workbook.close();

        //Create a new HTML file and write the table content
        String htmlFilePath = "output.html";
        File htmlFile = new File(htmlFilePath);
        BufferedWriter writer = new BufferedWriter(new FileWriter(htmlFile));
        writer.write(htmlTable.toString());
        writer.close();

        //Open the HTML file in default browser
        Desktop.getDesktop().browse(htmlFile.toURI());
    }
}