Reading file from excel in java

In this section, we are going to learn how we can read data from an excel file.

In Java, reading excel file is not similar to read word file because of cells in excel file. JDK does not provide direct API to read or write Microsoft Excel or Word document. We have to rely on the third-party library that is Apache POI.

What is Apache POI?

Apache POI (Poor Obfuscation Implementation) is a Java API for reading and writing Microsoft Documents in both formats .xls and .xlsx. It contains classes and interfaces. The Apache POI library provides two implementations for reading excel files:

• HSSF (Horrible SpreadSheet Format) Implementation: It denotes an API that is working with Excel 2003 or earlier versions.
• XSSF (XML SpreadSheet Format) Implementation: It denotes an API that is working with Excel 2007 or later versions.

Interfaces and Classes in Apache POI

Interfaces

• Workbook: It represents an Excel Workbook. It is an interface implement by HSSFWorkbook and XSSFWorkbook.
• Sheet: It is an interface that represents an Excel worksheet. A sheet is a central structure of a workbook, which represents a grid of cells. The Sheet interface extends java.lang.Iterable.
• Row: It is also an interface that represents the row of the spreadsheet. The Row interface extends java.lang.Iterable. There are two concrete classes: HSSFRow and XSSFRow.
• Cell: It is an interface. It is a high-level representation of a cell in a row of the spreadsheet. HSSFCell and XSSFCell implement Cell interface.

Classes

XLS Classes

• HSSFWorkbook: It is a class representing the XLS file.
• HSSFSheet: It is a class representing the sheet in an XLS file.
• HSSFRow: It is a class representing a row in the sheet of XLS file.
• HSSFCell: It is a class representing a cell in a row of XLS file.

XLSX Classes

• XSSFWorkbook: It is a class representing the XLSX file.
• XSSFSheet: It is a class representing the sheet in an XLSX file.
• XSSFRow: It is a class representing a row in the sheet of XLSX file.
• XSSFCell: It is a class representing a cell in a row of XLSX file.

Steps to read data from XLS file

Step 1: Create a simple Java project in eclipse.

Step 2: Now, create a lib folder in the project.

Step 3: Download and add the following jar files in the lib folder:

• commons-collections4-4.1.jar Click Here
• poi-3.17.jar Click Here
• poi-ooxml-3.17.jar Click Here
• poi-ooxml-schemas-3.17.jar Click Here
• xmlbeans-2.6.0.jar Click Here

Step 4: Set the Class Path:

Right-click on the project ->Build Path ->Add External JARs -> select all the above jar files -> Apply and close.

Step 5: Now create a class file with the name ReadExcelFileDemo and write the following code in the file.

Step 6: Create an excel file with the name «student.xls» and write some data into it.

Step 7: Save and run the program.

Example of reading excel file (.xls) file

Output:

Name        Age        Height		
Swarit      23.0        5"
Puneet      25.0        6'1"
Swastik     22.0        5'5"
Tejas       12.0        4'9"

Reading XLSX File

All steps will remain same except file format.

Table: employee.xslx

Example of read excel file (.xlsx)

In this example we use XSSFWorkbook class.

Output:

Employee ID   Employee Name    Salary     Designation          Department	
1223.0         Harsh           20000.0    Marketing Manager    Marketing
3213.0         Vivek           15000.0    Financial Advisor    Finance	
6542.0         Krishna         21000.0    HR Manager           HR		
9213.0         Sarika          34000.0    Sales Manager       Sales 

Reading a particular cell value from a excel file (.xlsx)

Table: EmployeeData.xlsx

Example

In the following example, we read the value of the 2^nd row and the 2^nd column. The row and column counting start from 0. So the program returns «Software Engineer.»

Output:

Learn to read excel, write excel, evaluate formula cells and apply custom formatting to the generated excel files using Apache POI library with examples.

If we are building software for the HR or Finance domain, there is usually a requirement for generating excel reports across management levels. Apart from reports, we can also expect some input data for the applications coming in the form of excel sheets and the application is expected to support this requirement.

Apache POI is a well-trusted library among many other open-source libraries to handle such usecases involving excel files. Please note that, in addition, we can read and write MS Word and MS PowerPoint files also using the Apache POI library.

This Apache POI tutorial will discuss some everyday excel operations in real-life applications.

1. Maven Dependency

If we are working on a maven project, we can include the Apache POI dependencies in pom.xml file using this:

<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi</artifactId>
  <version>5.2.2</version>
</dependency>

<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi-ooxml</artifactId>
  <version>5.2.2</version>
</dependency>

2. Important Classes in POI Library

1. HSSF, XSSF and XSSF classes

   Apache POI main classes usually start with either HSSF, XSSF or SXSSF.

   • HSSF – is the POI Project’s pure Java implementation of the Excel 97(-2007) file format. e.g., HSSFWorkbook, HSSFSheet.
   • XSSF – is the POI Project’s pure Java implementation of the Excel 2007 OOXML (.xlsx) file format. e.g., XSSFWorkbook, XSSFSheet.
   • SXSSF (since 3.8-beta3) – is an API-compatible streaming extension of XSSF to be used when huge spreadsheets have to be produced and heap space is limited. e.g., SXSSFWorkbook, SXSSFSheet. SXSSF achieves its low memory footprint by limiting access to the rows within a sliding window, while XSSF gives access to all rows in the document.

2. Row and Cell

   Apart from the above classes, Row and Cell interact with a particular row and a particular cell in an excel sheet.

3. Styling Related Classes

   A wide range of classes like CellStyle, BuiltinFormats, ComparisonOperator, ConditionalFormattingRule, FontFormatting, IndexedColors, PatternFormatting, SheetConditionalFormatting etc. are used when you have to add formatting to a sheet, primarily based on some rules.

4. FormulaEvaluator

   Another helpful class FormulaEvaluator is used to evaluate the formula cells in an excel sheet.

3. Writing an Excel File

I am taking this example first so we can reuse the excel sheet created by this code in further examples.

Writing excel using POI is very simple and involves the following steps:

1. Create a workbook
2. Create a sheet in workbook
3. Create a row in sheet
4. Add cells to sheet
5. Repeat steps 3 and 4 to write more data

It seems very simple, right? Let’s have a look at the code doing these steps.

Java program to write an excel file using Apache POI library.

package com.howtodoinjava.demo.poi;
//import statements
public class WriteExcelDemo 
{
    public static void main(String[] args) 
    {
        //Blank workbook
        XSSFWorkbook workbook = new XSSFWorkbook(); 
         
        //Create a blank sheet
        XSSFSheet sheet = workbook.createSheet("Employee Data");
          
        //This data needs to be written (Object[])
        Map<String, Object[]> data = new TreeMap<String, Object[]>();
        data.put("1", new Object[] {"ID", "NAME", "LASTNAME"});
        data.put("2", new Object[] {1, "Amit", "Shukla"});
        data.put("3", new Object[] {2, "Lokesh", "Gupta"});
        data.put("4", new Object[] {3, "John", "Adwards"});
        data.put("5", new Object[] {4, "Brian", "Schultz"});
          
        //Iterate over data and write to sheet
        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)
            {
               Cell cell = row.createCell(cellnum++);
               if(obj instanceof String)
                    cell.setCellValue((String)obj);
                else if(obj instanceof Integer)
                    cell.setCellValue((Integer)obj);
            }
        }
        try
        {
            //Write the workbook in file system
            FileOutputStream out = new FileOutputStream(new File("howtodoinjava_demo.xlsx"));
            workbook.write(out);
            out.close();
            System.out.println("howtodoinjava_demo.xlsx written successfully on disk.");
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }
}

See Also: Appending Rows to Excel

4. Reading an Excel File

Reading an excel file using POI is also very simple if we divide this into steps.

1. Create workbook instance from an excel sheet
2. Get to the desired sheet
3. Increment row number
4. iterate over all cells in a row
5. repeat steps 3 and 4 until all data is read

Let’s see all the above steps in code. I am writing the code to read the excel file created in the above example. It will read all the column names and the values in it – cell by cell.

Java program to read an excel file using Apache POI library.

package com.howtodoinjava.demo.poi;
//import statements
public class ReadExcelDemo 
{
    public static void main(String[] args) 
    {
        try
        {
            FileInputStream file = new FileInputStream(new File("howtodoinjava_demo.xlsx"));
 
            //Create Workbook instance holding reference to .xlsx file
            XSSFWorkbook workbook = new XSSFWorkbook(file);
 
            //Get first/desired sheet from the workbook
            XSSFSheet sheet = workbook.getSheetAt(0);
 
            //Iterate through each rows one by one
            Iterator<Row> rowIterator = sheet.iterator();
            while (rowIterator.hasNext()) 
            {
                Row row = rowIterator.next();
                //For each row, iterate through all the columns
                Iterator<Cell> cellIterator = row.cellIterator();
                 
                while (cellIterator.hasNext()) 
                {
                    Cell cell = cellIterator.next();
                    //Check the cell type and format accordingly
                    switch (cell.getCellType()) 
                    {
                        case Cell.CELL_TYPE_NUMERIC:
                            System.out.print(cell.getNumericCellValue() + "t");
                            break;
                        case Cell.CELL_TYPE_STRING:
                            System.out.print(cell.getStringCellValue() + "t");
                            break;
                    }
                }
                System.out.println("");
            }
            file.close();
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }
}

Program Output:

ID      NAME        LASTNAME
1.0     Amit        Shukla  
2.0     Lokesh      Gupta   
3.0     John        Adwards 
4.0     Brian       Schultz 

See Also: Apache POI – Read an Excel File using SAX Parser

5. Add and Evaluate Formula Cells

When working on complex excel sheets, we encounter many cells with formulas to calculate their values. These are formula cells. Apache POI also has excellent support for adding formula cells and evaluating already present formula cells.

Let’s see one example of how to add formula cells in excel?

The sheet has four cells in a row and the fourth one in the multiplication of all the previous 3 rows. So the formula will be: A2*B2*C2 (in the second row)

Java program to add formula in an excel file using Apache POI library.

public static void main(String[] args) 
{
    XSSFWorkbook workbook = new XSSFWorkbook();
    XSSFSheet sheet = workbook.createSheet("Calculate Simple Interest");
  
    Row header = sheet.createRow(0);
    header.createCell(0).setCellValue("Pricipal");
    header.createCell(1).setCellValue("RoI");
    header.createCell(2).setCellValue("T");
    header.createCell(3).setCellValue("Interest (P r t)");
      
    Row dataRow = sheet.createRow(1);
    dataRow.createCell(0).setCellValue(14500d);
    dataRow.createCell(1).setCellValue(9.25);
    dataRow.createCell(2).setCellValue(3d);
    dataRow.createCell(3).setCellFormula("A2*B2*C2");
      
    try {
        FileOutputStream out =  new FileOutputStream(new File("formulaDemo.xlsx"));
        workbook.write(out);
        out.close();
        System.out.println("Excel with foumula cells written successfully");
          
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Similarly, we want to read a file with formula cells and use the following logic to evaluate formula cells.

Java program to evaluate formula in an excel file using Apache POI library.

public static void readSheetWithFormula()
{
    try
    {
        FileInputStream file = new FileInputStream(new File("formulaDemo.xlsx"));
 
        //Create Workbook instance holding reference to .xlsx file
        XSSFWorkbook workbook = new XSSFWorkbook(file);
 
        FormulaEvaluator evaluator = workbook.getCreationHelper().createFormulaEvaluator();
         
        //Get first/desired sheet from the workbook
        XSSFSheet sheet = workbook.getSheetAt(0);
 
        //Iterate through each rows one by one
        Iterator<Row> rowIterator = sheet.iterator();
        while (rowIterator.hasNext()) 
        {
            Row row = rowIterator.next();
            //For each row, iterate through all the columns
            Iterator<Cell> cellIterator = row.cellIterator();
             
            while (cellIterator.hasNext()) 
            {
                Cell cell = cellIterator.next();
                //Check the cell type after eveluating formulae
                //If it is formula cell, it will be evaluated otherwise no change will happen
                switch (evaluator.evaluateInCell(cell).getCellType()) 
                {
                    case Cell.CELL_TYPE_NUMERIC:
                        System.out.print(cell.getNumericCellValue() + "tt");
                        break;
                    case Cell.CELL_TYPE_STRING:
                        System.out.print(cell.getStringCellValue() + "tt");
                        break;
                    case Cell.CELL_TYPE_FORMULA:
                        //Not again
                        break;
                }
            }
            System.out.println("");
        }
        file.close();
    } 
    catch (Exception e) 
    {
        e.printStackTrace();
    }
}

Program Output:

Pricipal        RoI         T       Interest (P r t)        
14500.0         9.25        3.0     402375.0  

6. Formatting the Cells

So far we have seen examples of reading/writing and excel files using Apache POI. But, when creating a report in an excel file, it is essential to add formatting on cells that fit into any pre-determined criteria.

This formatting can be a different coloring based on a specific value range, expiry date limit etc.

In the below examples, we are taking a couple of such cell formatting examples for various purposes.

6.1. Cell value in a specific range

This code will color any cell in a range whose value is between a configured range. [e.g., between 50 and 70]

static void basedOnValue(Sheet sheet) 
{
    //Creating some random values
    sheet.createRow(0).createCell(0).setCellValue(84);
    sheet.createRow(1).createCell(0).setCellValue(74);
    sheet.createRow(2).createCell(0).setCellValue(50);
    sheet.createRow(3).createCell(0).setCellValue(51);
    sheet.createRow(4).createCell(0).setCellValue(49);
    sheet.createRow(5).createCell(0).setCellValue(41);
 
    SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
 
    //Condition 1: Cell Value Is   greater than  70   (Blue Fill)
    ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule(ComparisonOperator.GT, "70");
    PatternFormatting fill1 = rule1.createPatternFormatting();
    fill1.setFillBackgroundColor(IndexedColors.BLUE.index);
    fill1.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
 
    //Condition 2: Cell Value Is  less than      50   (Green Fill)
    ConditionalFormattingRule rule2 = sheetCF.createConditionalFormattingRule(ComparisonOperator.LT, "50");
    PatternFormatting fill2 = rule2.createPatternFormatting();
    fill2.setFillBackgroundColor(IndexedColors.GREEN.index);
    fill2.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
 
    CellRangeAddress[] regions = {
            CellRangeAddress.valueOf("A1:A6")
    };
 
    sheetCF.addConditionalFormatting(regions, rule1, rule2);
}

6.2. Highlight Duplicate Values

Highlight all cells which have duplicate values in observed cells.

static void formatDuplicates(Sheet sheet) {
    sheet.createRow(0).createCell(0).setCellValue("Code");
    sheet.createRow(1).createCell(0).setCellValue(4);
    sheet.createRow(2).createCell(0).setCellValue(3);
    sheet.createRow(3).createCell(0).setCellValue(6);
    sheet.createRow(4).createCell(0).setCellValue(3);
    sheet.createRow(5).createCell(0).setCellValue(5);
    sheet.createRow(6).createCell(0).setCellValue(8);
    sheet.createRow(7).createCell(0).setCellValue(0);
    sheet.createRow(8).createCell(0).setCellValue(2);
    sheet.createRow(9).createCell(0).setCellValue(8);
    sheet.createRow(10).createCell(0).setCellValue(6);
 
    SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
 
    // Condition 1: Formula Is   =A2=A1   (White Font)
    ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule("COUNTIF($A$2:$A$11,A2)>1");
    FontFormatting font = rule1.createFontFormatting();
    font.setFontStyle(false, true);
    font.setFontColorIndex(IndexedColors.BLUE.index);
 
    CellRangeAddress[] regions = {
            CellRangeAddress.valueOf("A2:A11")
    };
 
    sheetCF.addConditionalFormatting(regions, rule1);
 
    sheet.getRow(2).createCell(1).setCellValue("<== Duplicates numbers in the column are highlighted.  " +
            "Condition: Formula Is =COUNTIF($A$2:$A$11,A2)>1   (Blue Font)");
}

6.3. Alternate Color Rows in Different Colors

A simple code to color each alternate row in a different color.

static void shadeAlt(Sheet sheet) {
    SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
 
    // Condition 1: Formula Is   =A2=A1   (White Font)
    ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule("MOD(ROW(),2)");
    PatternFormatting fill1 = rule1.createPatternFormatting();
    fill1.setFillBackgroundColor(IndexedColors.LIGHT_GREEN.index);
    fill1.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
 
    CellRangeAddress[] regions = {
            CellRangeAddress.valueOf("A1:Z100")
    };
 
    sheetCF.addConditionalFormatting(regions, rule1);
 
    sheet.createRow(0).createCell(1).setCellValue("Shade Alternating Rows");
    sheet.createRow(1).createCell(1).setCellValue("Condition: Formula Is  =MOD(ROW(),2)   (Light Green Fill)");
}

6.4. Color amounts that are going to expire in the next 30 days

A handy code for financial projects which keeps track of deadlines.

static void expiryInNext30Days(Sheet sheet) 
{
    CellStyle style = sheet.getWorkbook().createCellStyle();
    style.setDataFormat((short)BuiltinFormats.getBuiltinFormat("d-mmm"));
 
    sheet.createRow(0).createCell(0).setCellValue("Date");
    sheet.createRow(1).createCell(0).setCellFormula("TODAY()+29");
    sheet.createRow(2).createCell(0).setCellFormula("A2+1");
    sheet.createRow(3).createCell(0).setCellFormula("A3+1");
 
    for(int rownum = 1; rownum <= 3; rownum++) sheet.getRow(rownum).getCell(0).setCellStyle(style);
 
    SheetConditionalFormatting sheetCF = sheet.getSheetConditionalFormatting();
 
    // Condition 1: Formula Is   =A2=A1   (White Font)
    ConditionalFormattingRule rule1 = sheetCF.createConditionalFormattingRule("AND(A2-TODAY()>=0,A2-TODAY()<=30)");
    FontFormatting font = rule1.createFontFormatting();
    font.setFontStyle(false, true);
    font.setFontColorIndex(IndexedColors.BLUE.index);
 
    CellRangeAddress[] regions = {
            CellRangeAddress.valueOf("A2:A4")
    };
 
    sheetCF.addConditionalFormatting(regions, rule1);
 
    sheet.getRow(0).createCell(1).setCellValue("Dates within the next 30 days are highlighted");
}

I am ending this apache poi tutorial here to keep the post within a limit.

7. Conclusion

In this tutorial, we learned to read excel, write excel, set and evaluate formula cells, and format the cells with color codings using the Apache POI library.

Happy Learning !!

Source Code on Github

In this tutorial, I will share with you how to read Excel files programmatically using Java.

You know, Excel is the very popular file format created by Microsoft. Although it is not an opened file format, Java applications can still read and write Excel files using the Apache POI — the Java API for Microsoft Documents, because the development team uses reverse-engineering to understand the Excel file format. Hence the name POI stands for Poor Obfuscation Implementation.

This tutorial shows you how simple and easy it is to read Excel files using Apache POI’s API.

1. Getting Apache POI library

Apache POI is the pure Java API for reading and writing Excel files in both formats XLS (Excel 2003 and earlier) and XLSX (Excel 2007 and later). To use Apache POI in your Java project:

• For non-Maven projects:
  • Download the latest release of the library here: Apache POI — Download Release ArtifactsExtract the zip file and add the appropriate JAR files to your project’s classpath:- If you are reading and writing only Excel 2003 format, only the file poi-VERSION.jar is enough.- If you are reading and writing Excel 2007 format, you have to include the following files:
    • poi-ooxml-VERSION.jar
    • poi-ooxml-schemas-VERSION.jar
    • xmlbeans-VERSION.jar 
• For Maven projects: Add the following dependency to your project’s pom.xml file:
  • For Excel 2003 format only:

    <dependency>
    	<groupId>org.apache.poi</groupId>
    	<artifactId>poi</artifactId>
    	<version>VERSION</version>
    </dependency>

  • For Excel 2007 format:

    <dependency>
    	<groupId>org.apache.poi</groupId>
    	<artifactId>poi-ooxml</artifactId>
    	<version>VERSION</version>
    </dependency>

     The latest stable version of Apache POI is 3.11 (at the time of writing this tutorial).

2. The Apache POI API Basics

There are two main prefixes which you will encounter when working with Apache POI:

• HSSF: denotes the API is for working with Excel 2003 and earlier.
• XSSF: denotes the API is for working with Excel 2007 and later.

And to get started the Apache POI API, you just need to understand and use the following 4 interfaces:

• Workbook: high level representation of an Excel workbook. Concrete implementations are: HSSFWorkbookand XSSFWorkbook.
• Sheet: high level representation of an Excel worksheet. Typical implementing classes are HSSFSheetand XSSFSheet.
• Row: high level representation of a row in a spreadsheet. HSSFRowand XSSFRoware two concrete classes.
• Cell: high level representation of a cell in a row. HSSFCelland XSSFCellare the typical implementing classes.

Now, let’s walk through some real-life examples.

3. Reading from Excel File Examples

Suppose you want to read an Excel file whose content looks like the following screenshot:

This spreadsheet contains information about books (title, author and price).

A Simple Example to Read Excel File in Java

Here’s a dirty example that reads every cell in the first sheet of the workbook and prints out values in every cell, row by row:

package net.codejava.excel;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Iterator;

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

/**
 * A dirty simple program that reads an Excel file.
 * @author www.codejava.net
 *
 */
public class SimpleExcelReaderExample {
	
	public static void main(String[] args) throws IOException {
		String excelFilePath = "Books.xlsx";
		FileInputStream inputStream = new FileInputStream(new File(excelFilePath));
		
		Workbook workbook = new XSSFWorkbook(inputStream);
		Sheet firstSheet = workbook.getSheetAt(0);
		Iterator<Row> iterator = firstSheet.iterator();
		
		while (iterator.hasNext()) {
			Row nextRow = iterator.next();
			Iterator<Cell> cellIterator = nextRow.cellIterator();
			
			while (cellIterator.hasNext()) {
				Cell cell = cellIterator.next();
				
				switch (cell.getCellType()) {
					case Cell.CELL_TYPE_STRING:
						System.out.print(cell.getStringCellValue());
						break;
					case Cell.CELL_TYPE_BOOLEAN:
						System.out.print(cell.getBooleanCellValue());
						break;
					case Cell.CELL_TYPE_NUMERIC:
						System.out.print(cell.getNumericCellValue());
						break;
				}
				System.out.print(" - ");
			}
			System.out.println();
		}
		
		workbook.close();
		inputStream.close();
	}

}

Output:

Head First Java - Kathy Serria - 79.0 -
Effective Java - Joshua Bloch - 36.0 -
Clean Code - Robert Martin - 42.0 -
Thinking in Java - Bruce Eckel - 35.0 -

A More Object-Oriented Example to read Excel File

For nicer and more object-oriented program, let’s create a model class (Book.java) with the following code:

package net.codejava.excel;

public class Book {
	private String title;
	private String author;
	private float price;

	public Book() {
	}

	public String toString() {
		return String.format("%s - %s - %f", title, author, price);
	}

	// getters and setters
}

Write a method that reads value of a cell as following:

private Object getCellValue(Cell cell) {
	switch (cell.getCellType()) {
	case Cell.CELL_TYPE_STRING:
		return cell.getStringCellValue();

	case Cell.CELL_TYPE_BOOLEAN:
		return cell.getBooleanCellValue();

	case Cell.CELL_TYPE_NUMERIC:
		return cell.getNumericCellValue();
	}

	return null;
}

Next, implement a method that reads an Excel file and returns a list of books:

public List<Book> readBooksFromExcelFile(String excelFilePath) throws IOException {
	List<Book> listBooks = new ArrayList<>();
	FileInputStream inputStream = new FileInputStream(new File(excelFilePath));

	Workbook workbook = new XSSFWorkbook(inputStream);
	Sheet firstSheet = workbook.getSheetAt(0);
	Iterator<Row> iterator = firstSheet.iterator();

	while (iterator.hasNext()) {
		Row nextRow = iterator.next();
		Iterator<Cell> cellIterator = nextRow.cellIterator();
		Book aBook = new Book();

		while (cellIterator.hasNext()) {
			Cell nextCell = cellIterator.next();
			int columnIndex = nextCell.getColumnIndex();

			switch (columnIndex) {
			case 1:
				aBook.setTitle((String) getCellValue(nextCell));
				break;
			case 2:
				aBook.setAuthor((String) getCellValue(nextCell));
				break;
			case 3:
				aBook.setPrice((double) getCellValue(nextCell));
				break;
			}


		}
		listBooks.add(aBook);
	}

	workbook.close();
	inputStream.close();

	return listBooks;
}

And here is the testing code:

public static void main(String[] args) throws IOException {
	String excelFilePath = "Books.xlsx";
	ExcelReaderExample2 reader = new ExcelReaderExample2();
	List<Book> listBooks = reader.readBooksFromExcelFile(excelFilePath);
	System.out.println(listBooks);
}

Output:

[Head First Java - Kathy Serria - 79.000000, Effective Java - Joshua Bloch - 36.000000,
	Clean Code - Robert Martin - 42.000000, Thinking in Java - Bruce Eckel - 35.000000]

How to Read both Excel 2003 and 2007 format in Java

For better supporting both users using Excel 2003 and 2007, it’s recommended to write a separate factory method that returns an XSSFWorkbookor HSSFWorkbookdepending on the file extension of the file (.xls or .xlsx):

private Workbook getWorkbook(FileInputStream inputStream, String excelFilePath)
		throws IOException {
	Workbook workbook = null;

	if (excelFilePath.endsWith("xlsx")) {
		workbook = new XSSFWorkbook(inputStream);
	} else if (excelFilePath.endsWith("xls")) {
		workbook = new HSSFWorkbook(inputStream);
	} else {
		throw new IllegalArgumentException("The specified file is not Excel file");
	}

	return workbook;
}

And here’s a usage example of this factory method:

String excelFilePath = "Books.xlsx"; // can be .xls or .xlsx

FileInputStream inputStream = new FileInputStream(new File(excelFilePath));

Workbook workbook = getWorkbook(inputStream, excelFilePath);

Reading Other Information

• Get a specific sheet:

  Sheet thirdSheet = workbook.getSheetAt(2);

• Get sheet name:

  String sheetName = sheet.getSheetName();

• Get total number of sheets in the workbook:

  int numberOfSheets = workbook.getNumberOfSheets();

• Get all sheet names in the workbook:

  int numberOfSheets = workbook.getNumberOfSheets();
  
  for (int i = 0; i < numberOfSheets; i++) {
  	Sheet aSheet = workbook.getSheetAt(i);
  	System.out.println(aSheet.getSheetName());
  }

• Get comment of a specific cell:

  Comment cellComment = sheet.getCellComment(2, 2);
  System.out.println("comment: " + cellComment.getString());

  For reading other information, see the getXXX() methods of the Workbook, Sheet, Row and Cell interfaces.

That’s how to read Excel files in Java programmatically. I recommend you to take this Java course to fully learn Java programming.

Related Java Excel Tutorials:

• How to Write Excel Files in Java using Apache POI
• Java Example to Read Password-protected Excel Files Using Apache POI
• Java Example to Update Existing Excel Files Using Apache POI
• Working with Formula Cells in Excel using Apache POI

References:

• Apache POI — the Java API for Microsoft Documents
• POI API Documentation (Javadocs)
• Apache POI Quick Guide
• Apache POI HOWTO

Рассказывает автор блога javarevisited.blogspot.ru

Из этой статьи вы сможете узнать о записи и чтении данных из Excel файлов в Java (будет рассмотрен как XLS, так и XLSX формат). Мы будем использовать библиотеку Apache POI и сосредоточимся на работе с типами String и Date, работа с последним происходит достаточно хитро. Напомню, что работу с числами мы уже рассмотрели в другой статье.

Библиотеку poi-XX.jar вы можете использовать для всех старых (xls, doc, ppt) файлов Microsoft Office, для новых (xlsx, docx, pptx) вам понадобится poi-ooxml-XX.jar. Очень важно понимать, что к чему относится, т.к. используемые классы тоже разные — для старых расширений это HSSFWorkbook, а для новых — XSSFWorkbook.

Подготовка: загрузка библиотек и зависимостей

Конечно, существует достаточно много открытых библиотек, которые позволяют работать с Excel файлами в Java, например, JXL, но мы будем использовать имеющую самый обширный API и самую популярную — Apache POI. Чтобы её использовать, вам нужно скачать jar файлы и добавить их через Eclipse вручную, или вы можете предоставить это Maven.

Во втором случае вам нужно просто добавить следующие две зависимости:

<dependencies>
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>3.12</version>
    </dependency>
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>3.12</version>
    </dependency>
  </dependencies>

Самое удобное в Maven — что он загрузит не только указанные poi.jar и poi-ooxml.jar, но и все jar файлы, которые используются внутри, то есть xmlbeans-2.6.0.jar, stax-api-1.0.1.jar, poi-ooxml-schemas-3.12.jar и commons-codec-1.9.jar.

Если вы будете добавлять библиотеки вручную — не забудьте о вышеназванных файлах. Скачать всё можно отсюда. Помните — если вы загрузите только poi-XX.jar, то ваш код скомпилируется без ошибок, но потом упадёт с java.lang.NoClassDefFoundError: org/apache/xmlbeans/XmlObject, так как внутри будет вызываться xmlbeans.jar.

Запись

В этом примере мы запишем в xls файл следующие данные: в первую ячейку — строку с именем, а во вторую — дату рождения. Вот пошаговая инструкция:

• Создаём объект HSSFWorkBook;
• Создаём лист, используя на объекте, созданном в предыдущем шаге, createSheet();
• Создаём на листе строку, используя createRow();
• Создаём в строке ячейку — createCell();
• Задаём значение ячейки через setCellValue();
• Записываем workbook в File через FileOutputStream;
• Закрываем workbook, вызывая close().

Для записи строк или чисел этого вполне достаточно, но чтобы записать дату, нам понадобится сделать ещё кое-что:

• Создать DateFormat;
• Создать CellStyle;
• Записать DateFormat в CellStyle;
• Записать CellStyle в ячейку;
• Теперь в эту ячейку можно записать объект Date через всё тот же setCellValue;
• Чтобы дата поместилась в ячейку, нам нужно добавить столбцу свойство автоматически менять размер: sheet.autoSizeColumn(1).

Всё вместе это будет выглядеть так:

@SuppressWarnings("deprecation")
    public static void writeIntoExcel(String file) throws FileNotFoundException, IOException{
        Workbook book = new HSSFWorkbook();
        Sheet sheet = book.createSheet("Birthdays");

        // Нумерация начинается с нуля
        Row row = sheet.createRow(0); 
        
        // Мы запишем имя и дату в два столбца
        // имя будет String, а дата рождения --- Date,
        // формата dd.mm.yyyy
        Cell name = row.createCell(0);
        name.setCellValue("John");
        
        Cell birthdate = row.createCell(1);
        
        DataFormat format = book.createDataFormat();
        CellStyle dateStyle = book.createCellStyle();
        dateStyle.setDataFormat(format.getFormat("dd.mm.yyyy"));
        birthdate.setCellStyle(dateStyle);
        
 
        // Нумерация лет начинается с 1900-го
        birthdate.setCellValue(new Date(110, 10, 10));
        
        // Меняем размер столбца
        sheet.autoSizeColumn(1);
        
        // Записываем всё в файл
        book.write(new FileOutputStream(file));
        book.close();
    }

Чтение

Теперь мы считаем из только что созданного файла то, что мы туда записали.

• Для начала создадим HSSFWorkBook, передав в конструктор FileInputStream;
• Получаем лист, передавая в getSheet() его номер или название;
• Получаем строку, используя getRow();
• Получаем ячейку, используя getCell();
• Узнаём тип ячейки, используя на ней getCellType();
• В зависимости от типа ячейки, читаем её значения, используя getStringCellValue(), getNumericCellValue() или getDateCellValue();
• Закрываем workbook используя close().

Напомню, что дату Excel хранит как числа, т.е. тип ячейки всё равно будет CELL_TYPE_NUMERIC.

В виде кода это будет выглядеть следующим образом:

public static void readFromExcel(String file) throws IOException{
        HSSFWorkbook myExcelBook = new HSSFWorkbook(new FileInputStream(file));
        HSSFSheet myExcelSheet = myExcelBook.getSheet("Birthdays");
        HSSFRow row = myExcelSheet.getRow(0);
        
        if(row.getCell(0).getCellType() == HSSFCell.CELL_TYPE_STRING){
            String name = row.getCell(0).getStringCellValue();
            System.out.println("name : " + name);
        }
        
        if(row.getCell(1).getCellType() == HSSFCell.CELL_TYPE_NUMERIC){
            Date birthdate = row.getCell(1).getDateCellValue();
            System.out.println("birthdate :" + birthdate);
        }
        
        myExcelBook.close();
        
    }

В заключение

Как уже упомналось выше, чтение из xlsx файлов ничем принципиально не отличается — нужно только вместо HSSFWorkBook, HSSFSheet, HSSFRow (и прочих) из poi-XX.jar использовать XSSFWorkBook, XSSFSheet, XSSFRow из poi-ooxml-XX.jar. Это всё, что вам нужно знать для чтения и записи в файлы Excel. Разумеется, с помощью библиотеки Apache POI вы можете сделать гораздо больше, но эта статья должна помочь вам быстрее в ней освоиться.

_{Перевод статьи «How to Read Write Excel file in Java — POI Example»}

If you hate to maintain JARs by yourself, use Maven. In Eclipse IDE, you can download M2Eclipse plug-in to setup Maven project. Once you done that, add the following dependencies in your pom.xml (project object model) file.

    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>3.11-beta2</version>
    </dependency>

<dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>3.11-beta2</version>
</dependency>

The next line gives us a worksheet from the book, and from there we are just going through each row and then each column. Cell represents a block in Excel, also known as cell. This is where we read or write data. 

A cell can be any type e.g. String, numeric or boolean. Before reading the value you must ascertain the correct type of cell. After that just call corresponding value method e.g. getStringValue() or getNumericValue() to read data from cell. 

 File myFile = new File("C://temp/Employee.xlsx");
            FileInputStream fis = new FileInputStream(myFile);

            // Finds the workbook instance for XLSX file
            XSSFWorkbook myWorkBook = new XSSFWorkbook (fis);
           
            // Return first sheet from the XLSX workbook
            XSSFSheet mySheet = myWorkBook.getSheetAt(0);
           
            // Get iterator to all the rows in current sheet
            Iterator<Row> rowIterator = mySheet.iterator();
           
            // Traversing over each row of XLSX file
            while (rowIterator.hasNext()) {
                Row row = rowIterator.next();

                // For each row, iterate through each columns
                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("");
            }

This will save all updates you made in an existing file or in a new file which is created by Java’s File class. 

Here is a step by step code of updating an existing Excel file in Java. In first couple of lines we are creating rows in form of object array and storing them as values in HashMap with key as row number. 

After that, we loop through HashMap and insert each row at the end of the last row, in other words we are appending rows in our Excel file. Just like before reading we need to determine type of cell, we also need to do the same thing before writing data into cell. 

            Map<String, Object[]> data = new HashMap<String, Object[]>();
            data.put("7", new Object[] {7d, "Sonya", "75K", "SALES", "Rupert"});
            data.put("8", new Object[] {8d, "Kris", "85K", "SALES", "Rupert"});
            data.put("9", new Object[] {9d, "Dave", "90K", "SALES", "Rupert"});
         
            // Set to Iterate and add rows into XLS file
            Set<String> newRows = data.keySet();
         
            // get the last row number to append new data          
            int rownum = mySheet.getLastRowNum();         
         
            for (String key : newRows) {
             
                // Creating a new Row in existing XLSX sheet
                Row row = mySheet.createRow(rownum++);
                Object [] objArr = data.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 XLSX file
            FileOutputStream os = new FileOutputStream(myFile);
            myWorkBook.write(os);
            System.out.println("Writing on XLSX file Finished ...");


Output
Writing on XLSX file Finished ...

Exception in thread "main" org.apache.poi.poifs.
 filesystem.OfficeXmlFileException: 
 The supplied data appears to be in the Office 2007+ XML. 
 You are calling the part of POI that deals with OLE2 Office Documents. 
 You need to call a different part of POI to process this data 
 (eg XSSF instead of HSSF)
 at org.apache.poi.poifs.storage.HeaderBlock.<init>(HeaderBlock.java:131)
 at org.apache.poi.poifs.storage.HeaderBlock.<init>(HeaderBlock.java:104)
 at org.apache.poi.poifs.filesystem.POIFSFileSystem.<init>(POIFSFileSystem.java:128)
 at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:361)
 at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:342)
 at App.main(App.java:25)

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;

/**
 * Sample Java program to read and write Excel file in Java using Apache POI
 *
 */
public class XLSXReaderWriter {

    public static void main(String[] args) {

        try {
            File excel = new File("C://temp/Employee.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("7", new Object[] { 7d, "Sonya", "75K", "SALES",
                    "Rupert" });
            newData.put("8", new Object[] { 8d, "Kris", "85K", "SALES",
                    "Rupert" });
            newData.put("9", new Object[] { 9d, "Dave", "90K", "SALES",
                    "Rupert" });

            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();
        }
    }
}
Output
ID NAME SALARY DEPARTMENT MANGER 
1.0 John 70K IT Steve 
2.0 Graham 80K DATA Carl 
3.0 Sodhi 60K IT Ram 
4.0 Ram 100K IT Alex 
5.0 Carl 150K DATA Alex 
7.0 Sonya 75K SALES Rupert 
9.0 Dave 90K SALES Rupert 
8.0 Kris 85K SALES Rupert 
Writing on Excel file Finished ...

import java.io.FileOutputStream;

import java.io.IOException;

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 GFG {

    public static void main(String[] args)

    {

        XSSFWorkbook workbook = new XSSFWorkbook();

        XSSFSheet sheet

            = workbook.createSheet("student Details");

        Map<String, Object[]> data

            = new TreeMap<String, Object[]>();

        data.put("1",

                 new Object[] { "ID", "NAME", "LASTNAME" });

        data.put("2",

                 new Object[] { 1, "Pankaj", "Kumar" });

        data.put("3",

                 new Object[] { 2, "Prakashni", "Yadav" });

        data.put("4", new Object[] { 3, "Ayan", "Mondal" });

        data.put("5", new Object[] { 4, "Virat", "kohli" });

        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) {

                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("gfgcontribute.xlsx"));

            workbook.write(out);

            out.close();

            System.out.println(

                "gfgcontribute.xlsx written successfully on disk.");

        }

        catch (Exception e) {

            e.printStackTrace();

        }

    }

}