Poi excel examples java

Apache POI – Read and Write Excel File in Java

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.

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

 org.apache.poi poi 5.2.2  org.apache.poi poi-ooxml 5.2.2 

2. Important Classes in POI Library

HSSF, XSSF and XSSF classes

• 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.

Row and Cell

Styling Related Classes

FormulaEvaluator

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[]) Mapdata = new TreeMap(); data.put("1", new Object[] ); data.put("2", new Object[] ); data.put("3", new Object[] ); data.put("4", new Object[] ); data.put("5", new Object[] ); //Iterate over data and write to sheet Set 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(); >> >

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 IteratorrowIterator = sheet.iterator(); while (rowIterator.hasNext()) < Row row = rowIterator.next(); //For each row, iterate through all the columns IteratorcellIterator = 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(); >> >

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

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 IteratorrowIterator = sheet.iterator(); while (rowIterator.hasNext()) < Row row = rowIterator.next(); //For each row, iterate through all the columns IteratorcellIterator = 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(); >>

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

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("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 =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.

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.

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HSSF and XSSF Examples

Apache POI comes with a number of examples that demonstrate how you can use the POI API to create documents from «real life». The examples below based on common XSSF-HSSF interfaces so that you can generate either *.xls or *.xlsx output just by setting a command-line argument:

All sample source is available in SVN

In addition, there are a handful of HSSF only and XSSF only examples as well.

Available Examples

The following examples are available:

• Common HSSF and XSSF
  • Business Plan
  • Calendar
  • Loan Calculator
  • Timesheet
  • Conditional Formats
  • Formula Examples
  • Add Dimensioned Image
  • Aligned Cells
  • Cell Style Details
  • Linked Dropdown Lists
  • Common SS Performance Test
  • To HTML
  • To CSV

  Business Plan

  The BusinessPlan application creates a sample business plan with three phases, weekly iterations and time highlighting. Demonstrates advanced cell formatting (number and date formats, alignments, fills, borders) and various settings for organizing data in a sheet (freezed panes, grouped rows).

  

  Calendar

  The Calendar demo creates a multi sheet calendar. Each month is on a separate sheet.

  

  Loan Calculator

  The LoanCalculator demo creates a simple loan calculator. Demonstrates advance usage of cell formulas and named ranges.

  

  Timesheet

  The Timesheet demo creates a weekly timesheet with automatic calculation of total hours. Demonstrates advance usage of cell formulas.

  

  Conditional Formats

  The ConditionalFormats demo is a collection of short examples showing what you can do with Excel conditional formatting in POI:

  • Highlight cells based on their values
  • Highlight a range of cells based on a formula
  • Hide errors
  • Hide the duplicate values
  • Highlight duplicate entries in a column
  • Highlight items that are in a list on the worksheet
  • Highlight payments that are due in the next thirty days
  • Shade alternating rows on the worksheet
  • Shade bands of rows on the worksheet

  Formula Examples

  The CalculateMortgage example demonstrates a simple user-defined function to calculate principal and interest.

  The CheckFunctionsSupported example shows how to test what functions and formulas aren’t supported from a given file.

  The SettingExternalFunction example demonstrates how to use externally provided (third-party) formula add-ins.

  The UserDefinedFunctionExample example demonstrates how to invoke a User Defined Function for a given Workbook instance using POI’s UDFFinder implementation.

  Add Dimensioned Image

  The AddDimensionedImage example demonstrates how to add an image to a worksheet and set that images size to a specific number of millimetres irrespective of the width of the columns or height of the rows.

  Aligned Cells

  The AligningCells example demonstrates how various alignment options work.

  Cell Style Details

  The CellStyleDetails example demonstrates how to read excel styles for cells.

  Linked Dropdown Lists

  The LinkedDropDownLists example demonstrates one technique that may be used to create linked or dependent drop down lists.

  Common SS Performance Test

  The SSPerformanceTest example provides a way to create simple example files of varying sizes, and to calculate how long they take. Useful for benchmarking your system, and to also test if slow performance is due to Apache POI itself or to your own code.

  ToHtml

  The ToHtml example shows how to display a spreadsheet in HTML using the classes for spreadsheet display.

  ToCSV

  The ToCSV example demonstrates one way to convert an Excel spreadsheet into a CSV file.

  HSSF-only Examples

  All the HSSF-only examples can be found in SVN

  • CellComments
  • HyperlinkFormula
  • EventExample
  • OfficeDrawingWithGraphics
  • CreateDateCells
  • NewWorkbook
  • EmeddedObjects
  • Hyperlinks
  • OfficeDrawing
  • HSSFReadWrite
  • NewSheet
  • SplitAndFreezePanes
  • InCellLists
  • RepeatingRowsAndColumns
  • MergedCells
  • CellTypes
  • ZoomSheet
  • ReadWriteWorkbook
  • CreateCells
  • Alignment
  • FrillsAndFills
  • AddDimensionedImage
  • Borders
  • NewLinesInCells
  • WorkingWithFonts
  • BigExample
  • Outlines
  • XLS2CSVmra

  XSSF-only Examples

  All the XSSF-only examples can be found in SVN

  • CellComments
  • HeadersAndFooters
  • CreateUserDefinedDataFormats
  • CreatePivotTable
  • CreatePivotTable2
  • FillsAndColors
  • WorkingWithBorders
  • BigGridDemo
  • CreateTable
  • CalendarDemo
  • AligningCells
  • SplitAndFreezePanes
  • WorkingWithPageSetup
  • WorkingWithPictures
  • MergingCells
  • CustomXMLMapping
  • SelectedSheet
  • EmbeddedObjects
  • WorkbookProperties
  • NewLinesInCells
  • Outlining
  • CreateCell
  • IterateCells
  • BarChart
  • BarAndLineChart
  • LineChart
  • ScatterChart
  • WorkingWithFonts
  • HyperlinkExample
  • ShiftRows
  • WorkingWithRichText
  • FitSheetToOnePage
  • HybridStreaming
  • Outlining (SXSSF output)
  • DeferredGeneration (SXSSF output)
  • SavePasswordProtectedXlsx (SXSSF output)
  • XLSX2CSV (streaming read)
  • FromHowTo (streaming read)

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