Java Program to Extract Content from a Excel sheet - GeeksforGeeks

09 Nov, 2021
Spreadsheets are the easier way to represent table like data and can give a visual representation of data in tabular format. In this article, let us see how to extract the contents of the Excel sheet via java. Here there arise two cases where Maven is considered in the program or not. Discussing both of them as a prerequisite for a better understanding of the program.
Apache POI API basics are crucial before moving ahead, so the two main prefixes are required when working with Apache POI are as follows:
HSSF: denotes the API is for working with Excel 2003 and earlier.XSSF: denotes the API is for working with Excel 2007 and later.
HSSF: denotes the API is for working with Excel 2003 and earlier.
XSSF: denotes the API is for working with Excel 2007 and later.
Following 4 interfaces are important and essential to go through
Workbook: High-level representation of an Excel workbook. HSSFWorkbook and 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. HSSFRow and XSSFRow are two concrete classes.
Cell: High-level representation of a cell in a row. HSSFCell and XSSFCell are the typical implementing classes.
Case 1: Maven java project where dependencies are as follows
All Maven projects will have pom.xml as the main file.
There we need to add the dependencies.
pom.xml file contents Excel formats do differ a bit as shown below:
It is recommended to specify the latest version. (Maven project example used here is 3.11)
For Excel 2003 format
<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>
Case 2: Non-Maven Java project.
In order to meet the requirements there arises an urgent need to add the jar files in the build path in order to extract the contents. For this, download the latest release of the Apache POI library.
To extract the contents from
Excel 2003 format
poi-VERSION.jar is enough.
Excel 2007 format :
poi-ooxml-VERSION.jar
poi-ooxml-schemas-VERSION.jar
xmlbeans-VERSION.jar
Procedure: Reading from Excel file using Apache POI with examples. The goal is to read the contents from the given Excel file and display the contents of the Excel file in the “output” window.
Step 1: Here we are using the POJO class which has an equal number of fields as given in the attached Excel file. Excel file got 3 columns and hence 3 fields are there in the POJO class. Sample Excel file contents are as shown below. It is always nicer to have a POJO(Plain old java object) class for these kinds of operations. As there are 3 column values and the details are related to an employee, let us have an employee class.
Sample input image:
Empname, EmpDesignation, Salary are the columns
Example:
Java
// Java Program in which a Class is declared and// its methods are defined // Classclass Employee {     // Member variable of Employee Class    // Name, Designation and Salary    private String employeeName;    private String employeeDesignation;    private double salary;     // Constructor of Employee class    public Employee() {}     // Method 1    public String toString()    {        return String.format("%s - %s - %f", employeeName,                             employeeDesignation, salary);    }     // method 2    // To get name of an employee    public String getEmployeeName()    {         // Return the name of the employee        return employeeName;    }     // Method - 3    // To set employee name    public void setEmployeeName(String employeeName)    {         // This keyword refer to the current        // method or constructor itself        // Hence, same employee name can be set        // through this method        this.employeeName = employeeName;    }     // Method - 4    // To get already assigned designation of    // the employee over which method is invoked    public String getEmployeeDesignation()    {         // Return the designation of the employee        // over which the function is called        return employeeDesignation;    }     // Method - 5    // To assign a designation to an employee    public void    setEmployeeDesignation(String employeeDesignation)    {         // This keyword refer to the current        // method or constructor itself        this.employeeDesignation = employeeDesignation;    }     // Method - 6    // To get salary of an employee    public double getSalary()    {         // Return the salary of the employee for which        // the function is invoked        return salary;    }     // Method - 7    // To set salary of the existing employee with    // assigned name and designation    public void setSalary(double salary)    {        this.salary = salary;    }}
 Step 2: Depends on different data types like String, Number(it fits for integer, double, float, etc), Boolean, we need to have a method to get the cell values of Excel
Example:
Java
// Java Program to get the cell value// of the corresponding cells // Method// To get the cell valueprivate Object getCellValue(Cell cell){     // Now either do-while or switch can be used    // to display menu/user's choice     // Switch case is used here for illustration    // Switch case to get the users choice    switch (cell.getCellType()) {         // Case 1        // If cell contents are string    case Cell.CELL_TYPE_STRING:        return cell.getStringCellValue();         // Case 2        // If cell contents are Boolean    case Cell.CELL_TYPE_BOOLEAN:        return cell.getBooleanCellValue();         // Case 3        // If cell contents are Numeric which includes        // int, float , double etc    case Cell.CELL_TYPE_NUMERIC:        return cell.getNumericCellValue();    }     // Case 4    // Default case    // If cell contents are neither    // string nor Boolean nor Numeric,    // simply nothing is returned    return null;}
Step 3:Method to extract Excel file contents. We need to specify the location of the file correctly. otherwise, it will end up with IOException
Example:
Java
// Java Program to get the Excel file name// as an argument public List<Employee>readDataFromExcelFile(String excelFilePath)    throws IOException{    // Creating an List object of Employee type    // Note: User defined type    List<Employee> listEmployees        = new ArrayList<Employee>();     FileInputStream inputStream        = new FileInputStream(new File(excelFilePath));     // As used 'xlsx' file is used so XSSFWorkbook will be    // used    Workbook workbook = new XSSFWorkbook(inputStream);     // Read the first sheet and if the contents are in    // different sheets specifying the correct index    Sheet firstSheet = workbook.getSheetAt(0);     // Iterators to traverse over    Iterator<Row> iterator = firstSheet.iterator();     // Condition check using hasNext() method which holds    // true till there is single element remaining in List     while (iterator.hasNext()) {        // Get a row in sheet        Row nextRow = iterator.next();        // This is for a Row's cells        Iterator<Cell> cellIterator            = nextRow.cellIterator();        // We are taking Employee as reference.        Employee emp = new Employee();        // Iterate over the cells        while (cellIterator.hasNext()) {            Cell nextCell = cellIterator.next();             // Switch case variable to            // get the columnIndex            int columnIndex = nextCell.getColumnIndex();             // Depends upon the cell contents we need to            // typecast             // Switch-case            switch (columnIndex) {                 // Case 1            case 0:                // First column is alpha and hence                // it is typecasted to String                emp.setEmployeeName(                    (String)getCellValue(nextCell));                // Break keyword to directly terminate                // if this case is hit                break;                 // Case 2            case 1:                // Second  column is alpha and hence                // it is typecasted to String                emp.setEmployeeDesignation(                    (String)getCellValue(nextCell));                // Break keyword to directly terminate                // if this case is hit                break;                 // Case 3            case 2:                // Third  column is double value and                // hence it is typecasted to Double                emp.setSalary(                    (Double)getCellValue(nextCell));                break;                 // Note: If additional cells are present                // then                // they should be specified further down,                // and POJO class should accommodate those                // cell values            }        }        // Adding up to the list        listEmployees.add(emp);    }     // Closing the workbook and inputstream    // as it free up the space in memory    workbook.close();    inputStream.close();     // Return all the employees present in List    // object of Employee type    return listEmployees;}
Step 4: Integrating the concepts from Step 1 to Step 3 in the Main program
Java
// Main driver methodpublic static void main(String[] args){    // Detecting the file type    GetContentFromExcelSheets getContentFromExcelSheets        = new GetContentFromExcelSheets();    // Creating an List object of Employee type    // in main() method    List<Employee> extractedEmployeeData        = new ArrayList<Employee>();     // Try block to check if any exception/s occurs    try {        // excelFileContents.xlsx location need to be        // specified correctly or else IOException will be        // thrown. If file is available in that location, it        // gets the data and stored in a list variable        extractedEmployeeData            = getContentFromExcelSheets                  .readDataFromExcelFile(                      "excelFileContents.xlsx");    }     // Catch block to handle the exceptions if occurred    catch (IOException e) {         // Print the line number and exception        // in the program        e.printStackTrace();    }     // As there are possibility of data in multiple cells,    // it is always a good approach to follow a POJO pattern    // and get a row value in specified POJO As all data is    // collected in a list, we can iterate and display as    // below    for (int i = 0; i < extractedEmployeeData.size(); i++) {         // Print and display the employees data to the        //  console using toString() method to the user        System.out.println(            extractedEmployeeData.get(i).toString());    }}
 Output: For our example, we have 3 rows of data only
Implementation:
Example:
Java
// Java Program to Extract Content from a Excel sheet // As we are reading the excel file, java.io package is// compulsorily requiredimport java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.util.ArrayList;import java.util.Iterator;import java.util.List; // Below imports are required to access Apache POI// The usermodel package maps HSSF low level structures to// familiar workbook/sheet model// org.apache.poi.hssf.usermodel// But we are using higher excel formats hence,// org.apache.poi.ss.usermodel is used To determine the type// of cell contentimport org.apache.poi.ss.usermodel.Cell; // each and every row of excel is taken and stored in this// row formatimport org.apache.poi.ss.usermodel.Row; // excel sheet is read in this sheet formatimport org.apache.poi.ss.usermodel.Sheet; // excel Workbook is read in this Workbook formatimport org.apache.poi.ss.usermodel.Workbook; // XSSFWorkbook denotes the API is for working with Excel// 2007 and later.import org.apache.poi.xssf.usermodel.XSSFWorkbook; // POJO class having 3 fields matching with the given excel// fileclass Employee {    private String employeeName;    private String employeeDesignation;    private double salary;    // All 3 fields getter, setter methods should be there    public Employee() {}     public String toString()    {        return String.format("%s - %s - %f", employeeName,                             employeeDesignation, salary);    }     public String getEmployeeName() { return employeeName; }     public void setEmployeeName(String employeeName)    {        this.employeeName = employeeName;    }     public String getEmployeeDesignation()    {        return employeeDesignation;    }     public void    setEmployeeDesignation(String employeeDesignation)    {        this.employeeDesignation = employeeDesignation;    }     public double getSalary() { return salary; }     public void setSalary(double d) { this.salary = d; }}// class to assign the cell value once it is getting done to// read from excel sheet It can be String/Boolean/Numericpublic class GetContentFromExcelSheets {    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;    }    // Read the excel sheet contents and get the contents in    // a list    public List<Employee>    readBooksFromExcelFile(String excelFilePath)        throws IOException    {        List<Employee> listEmployees            = new ArrayList<Employee>();        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();            Employee emp = new Employee();             while (cellIterator.hasNext()) {                Cell nextCell = cellIterator.next();                int columnIndex = nextCell.getColumnIndex();                 switch (columnIndex) {                case 1:                    emp.setEmployeeName(                        (String)getCellValue(nextCell));                    break;                case 2:                    emp.setEmployeeDesignation(                        (String)getCellValue(nextCell));                    break;                case 3:                    emp.setSalary(Double.valueOf(                        (String)getCellValue(nextCell)));                    break;                }            }            listEmployees.add(emp);        }         ((FileInputStream)workbook).close();        inputStream.close();         return listEmployees;    }     // Main program    public static void main(String[] args)    {        // detecting the file type        GetContentFromExcelSheets getContentFromExcelSheets            = new GetContentFromExcelSheets();        List<Employee> extractedEmployeeData            = new ArrayList<Employee>();        try {            extractedEmployeeData                = getContentFromExcelSheets                      .readBooksFromExcelFile(                          "excelFileContents.xlsx");        }        catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        System.out.println(extractedEmployeeData);    }}
Conclusion : Apache POI provides a nicer implementation to extract Excel file contents. In coding, according to the availability of data in the number of cells, we need to have POJO class attributes and also we need to specify coll data in the “readDataFromExcelFile” method. We can format Double data as per our requirement also.
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