Apache POI - Spreadsheets

This chapter explains how to create a spreadsheet and manipulate it using Java. Spreadsheet is a page in an Excel file; it contains rows and columns with specific names.
After completing this chapter, you will be able to create a spreadsheet and perform read operations on it.
First of all, let us create a spreadsheet using the referenced classes discussed in the earlier chapters. By following the previous chapter, create a workbook first and then we can go on and create a sheet.
The following code snippet is used to create a spreadsheet.
//Create Blank workbook
XSSFWorkbook workbook = new XSSFWorkbook();

//Create a blank spreadsheet
XSSFSheet spreadsheet = workbook.createSheet("Sheet Name");
Spreadsheets have a grid layout. The rows and columns are identified with specific names. The columns are identified with alphabets and rows with numbers.
The following code snippet is used to create a row.
XSSFRow row = spreadsheet.createRow((short)1);

Let us consider an example of employee data. Here the employee data is given in a tabular form.
The following code is used to write the above data into a spreadsheet.
import java.io.File;
import java.io.FileOutputStream;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class Writesheet {
   public static void main(String[] args) throws Exception {
      //Create blank workbook
      XSSFWorkbook workbook = new XSSFWorkbook(); 

      //Create a blank sheet
      XSSFSheet spreadsheet = workbook.createSheet(" Employee Info ");

      //Create row object
      XSSFRow row;

      //This data needs to be written (Object[])
      Map < String, Object[] > empinfo = new TreeMap < String, Object[] >();
      empinfo.put( "1", new Object[] { "EMP ID", "EMP NAME", "DESIGNATION" });
      empinfo.put( "2", new Object[] { "tp01", "Gopal", "Technical Manager" });
      empinfo.put( "3", new Object[] { "tp02", "Manisha", "Proof Reader" });
      empinfo.put( "4", new Object[] { "tp03", "Masthan", "Technical Writer" });
      empinfo.put( "5", new Object[] { "tp04", "Satish", "Technical Writer" });
      empinfo.put( "6", new Object[] { "tp05", "Krishna", "Technical Writer" });
      
      //Iterate over data and write to sheet
      Set < String > keyid = empinfo.keySet();
      int rowid = 0;

      for (String key : keyid) {
         row = spreadsheet.createRow(rowid++);
         Object [] objectArr = empinfo.get(key);
         int cellid = 0;

         for (Object obj : objectArr) {
            Cell cell = row.createCell(cellid++);
            cell.setCellValue((String)obj);
         }
      }
      //Write the workbook in file system
      FileOutputStream out = new FileOutputStream(new File("Writesheet.xlsx"));
      workbook.write(out);
      out.close();
      System.out.println("Writesheet.xlsx written successfully");
   }
}
Save the above Java code as Writesheet.java, and then compile and run it from the command prompt as follows −
$javac Writesheet.java
$java Writesheet

It will compile and execute to generate an Excel file named Writesheet.xlsx in your current directory and you will get the following output in the command prompt.
Writesheet.xlsx written successfully

The Writesheet.xlsx file looks as follows −
Let us consider the above excel file named Writesheet.xslx as input. Observe the following code; it is used for reading the data from a spreadsheet.
import java.io.File;
import java.io.FileInputStream;
import java.util.Iterator;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class Readsheet {
   static XSSFRow row;
   public static void main(String[] args) throws Exception {
      FileInputStream fis = new FileInputStream(new File("WriteSheet.xlsx"));
      XSSFWorkbook workbook = new XSSFWorkbook(fis);
      XSSFSheet spreadsheet = workbook.getSheetAt(0);
      Iterator < Row >  rowIterator = spreadsheet.iterator();
      
      while (rowIterator.hasNext()) {
         row = (XSSFRow) rowIterator.next();
         Iterator < Cell >  cellIterator = row.cellIterator();
         
         while ( cellIterator.hasNext()) {
            Cell cell = cellIterator.next();
            
            switch (cell.getCellType()) {
               case NUMERIC:
                  System.out.print(cell.getNumericCellValue() + " \t\t ");
                  break;
               
               case STRING:
                  System.out.print(
                  cell.getStringCellValue() + " \t\t ");
                  break;
            }
         }
         System.out.println();
      }
      fis.close();
   }
}
Let us keep the above code in Readsheet.java file, and then compile and run it from the command prompt as follows −
$javac Readsheet.java
$java Readsheet

If your system environment is configured with the POI library, it will compile and execute to generate the following output in the command prompt.
EMP ID   EMP NAME       DESIGNATION 
 tp01     Gopal       Technical Manager 
 tp02     Manisha     Proof Reader 
 tp03     Masthan     Technical Writer 
 tp04     Satish      Technical Writer 
 tp05     Krishna     Technical Writer


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