Java Program to read from Excel File


package com.howtodoinjava.demo.poi;

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.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

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())
{
//System.out.print(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();
}
}
}

Java Program to Write File in to Excel


package com.howtodoinjava.demo.poi;

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.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
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();
}
}
}