Reading and Writing Excel file in Java Using Apache POI

By | April 9, 2018

Reading and Writing Excel file in Java Using Apache POI – In this java tutorial and example, i will show to you how to import and export data in excel in java code and also discuss about how to read and write an excel file using Apache POI

Reading and Writing Excel file in Java Using Apache POI

If you want to build feature like export and import excel in java, at least you must learn 2 excel library like Apache POI or JExcel API. In this java tutorial i will teach you to write and read data in excel using Apache POI in java code. But if you want to learn how to use JExcel API too, please read my last article Reading and Writing Excel file in Java Using JExcel API.

1. Definitions for Apache POI library

This section briefly describe about basic classes used during Excel Read and Write.

  1. HSSF is prefixed before the class name to indicate operations related to a Microsoft Excel 2003 file.
  2. XSSF is prefixed before the class name to indicate operations related to a Microsoft Excel 2007 file or later.
  3. XSSFWorkbook and HSSFWorkbook are classes which act as an Excel Workbook
  4. HSSFSheet and XSSFSheet are classes which act as an Excel Worksheet
  5. Row defines an Excel row
  6. Cell defines an Excel cell addressed in reference to a row.

2. Import Apache POI library using Maven Depedency

Apache POI library is easily available using Maven Dependencies or Gradle.

add this depedency to your pom.xml file.
  <dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>3.15</version>
  </dependency>

3. Apache POI library – Writing a Simple Excel

The below code shows how to write a simple Excel file using Apache POI libraries. The code uses a 2 dimensional data array to hold the data. The data is written to a XSSFWorkbook object. XSSFSheet is the work sheet being worked on. The code is as shown below:

ApachePOIExcelWrite.java
package com.cimblo;

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;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class ApachePOIExcelWrite {

    private static final String FILE_NAME = "/tmp/ReadWriteExcelInJava.xlsx";
    public static void main(String[] args) {

        XSSFWorkbook workbook = new XSSFWorkbook();
        XSSFSheet sheet = workbook.createSheet("Datatypes in Java");
        Object[][] datatypes = {
                {"Datatype", "Type", "Size(in bytes)"},
                {"int", "Primitive", 2},
                {"float", "Primitive", 4},
                {"double", "Primitive", 8},
                {"char", "Primitive", 1},
                {"String", "Non-Primitive", "No fixed size"}
        };

        int rowNum = 0;
        System.out.println("Creating excel");

        for (Object[] datatype : datatypes) {
            Row row = sheet.createRow(rowNum++);
            int colNum = 0;
            for (Object field : datatype) {
                Cell cell = row.createCell(colNum++);
                if (field instanceof String) {
                    cell.setCellValue((String) field);
                } else if (field instanceof Integer) {
                    cell.setCellValue((Integer) field);
                }
            }
        }

        try {
            FileOutputStream outputStream = new FileOutputStream(FILE_NAME);
            workbook.write(outputStream);
            workbook.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("Done");
    }
}

 

4. Apache POI library – Reading an Excel file

The below code explains how to read an Excel file using Apache POI libraries. The function getCellTypeEnum is deprecated in version 3.15 and will be renamed to getCellType from version 4.0 onwards.

ApachePOIExcelRead.java
package com.cimblo;

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Iterator;

public class ApachePOIExcelRead {

    private static final String FILE_NAME = "/tmp/ReadWriteExcelInJava.xlsx";

    public static void main(String[] args) {

        try {

            FileInputStream excelFile = new FileInputStream(new File(FILE_NAME));
            Workbook workbook = new XSSFWorkbook(excelFile);
            Sheet datatypeSheet = workbook.getSheetAt(0);
            Iterator<Row> iterator = datatypeSheet.iterator();

            while (iterator.hasNext()) {

                Row currentRow = iterator.next();
                Iterator<Cell> cellIterator = currentRow.iterator();

                while (cellIterator.hasNext()) {

                    Cell currentCell = cellIterator.next();
                    //getCellTypeEnum shown as deprecated for version 3.15
                    //getCellTypeEnum ill be renamed to getCellType starting from version 4.0
                    if (currentCell.getCellTypeEnum() == CellType.STRING) {
                        System.out.print(currentCell.getStringCellValue() + "--");
                    } else if (currentCell.getCellTypeEnum() == CellType.NUMERIC) {
                        System.out.print(currentCell.getNumericCellValue() + "--");
                    }

                }
                System.out.println();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

On executing the above code, you get the below output.

Datatype--Type--Size(in bytes)--
int--Primitive--2.0--
float--Primitive--4.0--
double--Primitive--8.0--
char--Primitive--1.0--
String--Non-Primitive--No fixed size--
That is some trick to you about Reading and Writing Excel file in Java Using Apache POI. And also do not forget to check and upgrade Apache POI library version if there found a new version to get new feature on this library.

References

  1. Apache POI reference regarding Deprecation
  2. Apache POI Maven Repo
  3. Apache POI API docs

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