How to read and write excel file

Question

I want to read and write an Excel file from Java with 3 columns and N rows, printing one string in each cell. Can anyone give me simple code snippet for this? Do I need to

Answer 1

A simple CSV file should suffice

Answer 2

You can not read & write same file in parallel(Read-write lock). But, we can do parallel operations on temporary data(i.e. Input/output stream). Write the data to file only after closing the input stream. Below steps should be followed.

• Open the file to Input stream
• Open the same file to an Output Stream
• Read and do the processing
• Write contents to output stream.
• Close the read/input stream, close file
• Close output stream, close file.

Apache POI - read/write same excel example

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;


public class XLSXReaderWriter {

    public static void main(String[] args) {

        try {
            File excel = new File("D://raju.xlsx");
            FileInputStream fis = new FileInputStream(excel);
            XSSFWorkbook book = new XSSFWorkbook(fis);
            XSSFSheet sheet = book.getSheetAt(0);

            Iterator<Row> itr = sheet.iterator();

            // Iterating over Excel file in Java
            while (itr.hasNext()) {
                Row row = itr.next();

                // Iterating over each column of Excel file
                Iterator<Cell> cellIterator = row.cellIterator();
                while (cellIterator.hasNext()) {

                    Cell cell = cellIterator.next();

                    switch (cell.getCellType()) {
                    case Cell.CELL_TYPE_STRING:
                        System.out.print(cell.getStringCellValue() + "\t");
                        break;
                    case Cell.CELL_TYPE_NUMERIC:
                        System.out.print(cell.getNumericCellValue() + "\t");
                        break;
                    case Cell.CELL_TYPE_BOOLEAN:
                        System.out.print(cell.getBooleanCellValue() + "\t");
                        break;
                    default:

                    }
                }
                System.out.println("");
            }

            // writing data into XLSX file
            Map<String, Object[]> newData = new HashMap<String, Object[]>();
            newData.put("1", new Object[] { 1d, "Raju", "75K", "dev",
                    "SGD" });
            newData.put("2", new Object[] { 2d, "Ramesh", "58K", "test",
                    "USD" });
            newData.put("3", new Object[] { 3d, "Ravi", "90K", "PMO",
                    "INR" });

            Set<String> newRows = newData.keySet();
            int rownum = sheet.getLastRowNum();

            for (String key : newRows) {
                Row row = sheet.createRow(rownum++);
                Object[] objArr = newData.get(key);
                int cellnum = 0;
                for (Object obj : objArr) {
                    Cell cell = row.createCell(cellnum++);
                    if (obj instanceof String) {
                        cell.setCellValue((String) obj);
                    } else if (obj instanceof Boolean) {
                        cell.setCellValue((Boolean) obj);
                    } else if (obj instanceof Date) {
                        cell.setCellValue((Date) obj);
                    } else if (obj instanceof Double) {
                        cell.setCellValue((Double) obj);
                    }
                }
            }

            // open an OutputStream to save written data into Excel file
            FileOutputStream os = new FileOutputStream(excel);
            book.write(os);
            System.out.println("Writing on Excel file Finished ...");

            // Close workbook, OutputStream and Excel file to prevent leak
            os.close();
            book.close();
            fis.close();

        } catch (FileNotFoundException fe) {
            fe.printStackTrace();
        } catch (IOException ie) {
            ie.printStackTrace();
        }
    }
}

Answer 3

I edited the most voted one a little cuz it didn't count blanks columns or rows well not totally, so here is my code i tested it and now can get any cell in any part of an excel file. also now u can have blanks columns between filled column and it will read them

  try {
POIFSFileSystem fs = new POIFSFileSystem(new FileInputStream(Dir));
HSSFWorkbook wb = new HSSFWorkbook(fs);
HSSFSheet sheet = wb.getSheetAt(0);
HSSFRow row;
HSSFCell cell;

int rows; // No of rows
rows = sheet.getPhysicalNumberOfRows();

int cols = 0; // No of columns
int tmp = 0;
int cblacks=0;

// This trick ensures that we get the data properly even if it doesn't start from first few rows
for(int i = 0; i <= 10 || i <= rows; i++) {
    row = sheet.getRow(i);
    if(row != null) {
        tmp = sheet.getRow(i).getPhysicalNumberOfCells();
        if(tmp >= cols) cols = tmp;else{rows++;cblacks++;}
    }

    cols++;
}
cols=cols+cblacks;
for(int r = 0; r < rows; r++) {
    row = sheet.getRow(r);
    if(row != null) {
        for(int c = 0; c < cols; c++) {
            cell = row.getCell(c);
            if(cell != null) {
                System.out.print(cell+"\n");//Your Code here
            }
        }
    }
}} catch(Exception ioe) {
ioe.printStackTrace();}

Answer 4

When using the apache poi 4.1.2. The celltype changes a bit. Below is an example

    try {
        File excel = new File("/home/name/Downloads/bb.xlsx");
        FileInputStream fis = new FileInputStream(excel);
        XSSFWorkbook book = new XSSFWorkbook(fis);
        XSSFSheet sheet = book.getSheetAt(0);

        Iterator<Row> itr = sheet.iterator();

        // Iterating over Excel file in Java
        while (itr.hasNext()) {
            Row row = itr.next();

            Iterator<Cell> cellIterator = row.cellIterator();
            while (cellIterator.hasNext()) {



                Cell cell = cellIterator.next();



                switch (cell.getCellType()) {
                case STRING:
                    System.out.print(cell.getStringCellValue() + "\t");
                    break;
                case NUMERIC:
                    System.out.print(cell.getNumericCellValue() + "\t");
                    break;
                case BOOLEAN:
                    System.out.print(cell.getBooleanCellValue() + "\t");
                    break;
                default:


                }
            }
            System.out.println("");}
        }catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }

Answer 5

Another way to read/write Excel files is to use Windmill. It provides a fluent API to process Excel and CSV files.

Import data

try (Stream<Row> rowStream = Windmill.parse(FileSource.of(new FileInputStream("myFile.xlsx")))) {
  rowStream
    // skip the header row that contains the column names
    .skip(1)
    .forEach(row -> {
      System.out.println(
        "row n°" + row.rowIndex()
        + " column 'User login' value : " + row.cell("User login").asString()
        + " column n°3 number value : " + row.cell(2).asDouble().value() // index is zero-based
      );
    });
}

Export data

Windmill
  .export(Arrays.asList(bean1, bean2, bean3))
  .withHeaderMapping(
    new ExportHeaderMapping<Bean>()
      .add("Name", Bean::getName)
      .add("User login", bean -> bean.getUser().getLogin())
  )
  .asExcel()
  .writeTo(new FileOutputStream("Export.xlsx"));

Answer 6

If column number are varing you can use this

package com.org.tests;
import org.apache.poi.xssf.usermodel.*;
import java.io.FileInputStream;
import java.io.IOException;

public class ExcelSimpleTest 
{   
    String path;
    public FileInputStream fis = null;
    private XSSFWorkbook workbook = null;
    private XSSFSheet sheet = null;
    private XSSFRow row   =null;
    private XSSFCell cell = null;

    public ExcelSimpleTest() throws IOException
    {
        path = System.getProperty("user.dir")+"\\resources\\Book1.xlsx";
        fis = new FileInputStream(path); 
        workbook = new XSSFWorkbook(fis);
        sheet = workbook.getSheetAt(0);
    }
    public void ExelWorks()
    {
        int index = workbook.getSheetIndex("Sheet1");
        sheet = workbook.getSheetAt(index);
        int rownumber=sheet.getLastRowNum()+1;  

        for (int i=1; i<rownumber; i++ )
        {
            row = sheet.getRow(i);
            int colnumber = row.getLastCellNum();
            for (int j=0; j<colnumber; j++ )
            {
                cell = row.getCell(j);
                System.out.println(cell.getStringCellValue());
            }
        }
    }   
    public static void main(String[] args) throws IOException 
    {
        ExcelSimpleTest excelwork = new ExcelSimpleTest();
        excelwork.ExelWorks();
    }
}

The corresponding mavendependency can be found here