POI XSSF (Example)

1. PersonDO

import java.util.ArrayList;
/**
 *
 */
/**
 * @author abhinav
 */
public class PersonDO
{
    private String name;
    private String city;
    private String phone;
    public static ArrayList<PersonDO> getPersons( Number n )
    {
        ArrayList<PersonDO> list = new ArrayList<PersonDO>();
        for ( int i = 0; i <= n.intValue(); i++ )
        {
            PersonDO p = new PersonDO();
            p.setName( "abhinav " + i );
            p.setCity( "pune " + i );
            p.setPhone( "phone " + i );
            list.add( p );
        }
        return list;
    }
    /**
     * @return the name
     */
    public String getName()
    {
        return name;
    }
    /**
     * @param name the name to set
     */
    public void setName( String name )
    {
        this.name = name;
    }
    /**
     * @return the city
     */
    public String getCity()
    {
        return city;
    }
    /**
     * @param city the city to set
     */
    public void setCity( String city )
    {
        this.city = city;
    }
    /**
     * @return the phone
     */
    public String getPhone()
    {
        return phone;
    }
    /**
     * @param phone the phone to set
     */
    public void setPhone( String phone )
    {
        this.phone = phone;
    }
}

==============================================

2.  Write to Excel

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.ArrayList;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
//import statements
public class ReadExcelDemo
{
    public static void main( String[] args )
    {
        System.out.println( java.lang.Runtime.getRuntime().maxMemory() );
        try
        {
            FileInputStream file = new FileInputStream( new File( "path2template.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 );
            ArrayList<PersonDO> persons = PersonDO.getPersons( 1000000 );
            int startIndex = 1;
            System.out.println( "Populating data..." );
            for ( PersonDO p : persons )
            {
                // Row row = sheet.getRow( startIndex );
                Row row = sheet.createRow( startIndex ); // getRow( startIndex );
                row.createCell( 0 ).setCellValue( p.getName() );
                row.createCell( 1 ).setCellValue( p.getPhone() );
                row.createCell( 2 ).setCellValue( p.getCity() );
                if ( startIndex % 500 == 0 )
                {
                    System.out.println( "At " + startIndex );
                    System.out.println( java.lang.Runtime.getRuntime().freeMemory() );
                }
                startIndex++;
            }
            System.out.println( "Writing to excel..." );
            FileOutputStream fileOut = new FileOutputStream( "output_file.xlsx" );
            workbook.write( fileOut );
            System.out.println( "Completed..." );
            fileOut.close();
            file.close();
        }
        catch ( Exception e )
        {
            e.printStackTrace();
        }
    }
}

Used JARS

G:\WORKSPACE\ALLPROJECTS\EXCELPOI\LIBS

1.     dom4j-1.6.1.jar
2.     poi-3.10-FINAL-20140208.jar
3.     poi-examples-3.10-FINAL-20140208.jar
4.     poi-ooxml-3.10-FINAL-20140208.jar
5.     poi-ooxml-schemas-3.10-FINAL-20140208.jar
6.     xmlbeans-2.3.0.jar

ExcelTemplate
https://drive.google.com/file/d/0B3prgPRdV5ZbOEhVSEpqZEV6SjQ/edit?usp=sharing