How to get only a line containg two characters from text file

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.PrintWriter;

public class ll {

public static void main(String[] args) {
    FileReader fr = null;
    BufferedReader br =null;

    String [] stringArray;
    int counLine = 0;
    int arrayLength ;
    String s="";
    String stringLine="";
    try{
     //   fr = new FileReader("F:\\New folder (2)\\N.txt");
        String wrt="F:\\New folder (2)\\N.txt";
String line=null;
 fr=new FileReader(wrt);
FileWriter fw=new FileWriter(wrt);
BufferedWriter bw=new BufferedWriter(fw);
 
        br = new BufferedReader(fr);
        while((s = br.readLine()) != null){
            stringLine = stringLine + line;
            stringLine = stringLine + " ";
            counLine ++;  
        }System.out.println(stringLine);
 while((line=br.readLine())!=null)
       {
          System.out.print(line);
        }
        br.close();
        stringArray = stringLine.split(" ");
        arrayLength = stringArray.length;
     for (int i = 0; i < arrayLength; i++) {
            int c = 1 ;
            for (int j = i+1; j < arrayLength; j++) {
                if(stringArray[i].equalsIgnoreCase(stringArray[j])){
                   c++;
                   for (int j2 = j; j2 < arrayLength; j2++) {
                 }
     }
                int k;
              for(k=2;k==stringArray[i].length();i++)
           
             // if(stringArray[i].length()==1)
                {     bw.write(stringArray[i]);
              //    System.out.println(stringArray[i]);  
              }
            }}

//bw.newLine();
//bw.write("hello");
bw.close();
     fr.close();
        br.close();
    }catch (Exception e) {
        e.printStackTrace();
    }}}