java - Unable to update the required cell values in the excel using apache poi? -

below program trying update birds column value(ex:duck) not updated after "parrot" value.i want output below.can 1 me resolve this. program: package config;

import java.io.fileinputstream; import java.io.fileoutputstream; import org.apache.poi.xssf.usermodel.xssfcell; import org.apache.poi.xssf.usermodel.xssfrow; import org.apache.poi.xssf.usermodel.xssfsheet; import org.apache.poi.xssf.usermodel.xssfworkbook; import org.testng.annotations.test;  public class writing  { @test     public void test() throws exception     { fileinputstream f1=new fileinputstream("d://xl4.xlsx"); xssfworkbook w1=new xssfworkbook(f1); xssfsheet s1=w1.getsheetat(0); xssfcell c = null; xssfrow r = null; int rows=s1.getphysicalnumberofrows(); for(int i=0;i<=rows;i++) {     r = s1.getrow(i);      if(r == null)     {         s1.createrow((short) (i)).createcell(1).setcellvalue("duck");     } } fileoutputstream f2=new fileoutputstream("d://xl4.xlsx"); w1.write(f2); f2.close();         } }   **actual result:** animals     birds elephant    parrot lion     tiger    deer     cow              duck  **expected result:** animals     birds elephant    parrot lion        duck tiger    deer     cow   [output][1]     [1]: http://i.stack.imgur.com/xzttz.png 

if(r == null)  

is culprit here. when in 3rd row r = s1.getrow(i) not null. so, call not come inside condition block.

change condition row not null , second cell null - create new cell , assign value "duck" here.