Java: Unable to Concatenate to file using BufferedWriter and FileWriter

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;

public class TestConcatenateFiles {
    
    public static void main(String[] args) {
        
        String relativeSourceFileName = "Test1.txt";
        String sourceDirPath = "C:\\Source";
        String destDirPath = "C:\\Destination";
        
        processResultInSourceDirIfExistsInDestDir(relativeSourceFileName, sourceDirPath, destDirPath);
                                                                                                                  
    }
    
    
    
    // See if file 'relativeSourceFileName' exists with earlier file date in 'destDirPath' location
    // if it does, than read the file from 'destDirPath' and concatenate to this file the same filename 
    // in 'sourceDirPath'
    private static void processResultInSourceDirIfExistsInDestDir(String relativeSourceFileName, String sourceDirPath, String destDirPath){
        
        // See if file exists in the destination folder:
        File fileOnServer = new File(destDirPath + "\\" + relativeSourceFileName);
        String line = "";
        ArrayList<String> linesListResultFile = new  ArrayList<String>();
        
            if(fileOnServer.exists() && !fileOnServer.isDirectory()) {   // If file exists and it is not directory, 
                // then concatenate current test results to the file on server and save it at local
                // folder to be backed up later on server.
                
                try {
                            // FileReader reads text files in the default encoding:
                            FileReader fileReader = new FileReader(sourceDirPath + "\\" + relativeSourceFileName);
                            // wrap FileReader in BufferedReader:
                            BufferedReader bufferedReader = new BufferedReader(fileReader);

                            while((line = bufferedReader.readLine()) != null) {
                                linesListResultFile.add(line);
                            }    
                            // Close file
                            bufferedReader.close();            
                        }
                        catch(FileNotFoundException ex) {
                            System.out.println(
                                "File not found, unable to open file '" + 
                                sourceDirPath + "\\" + relativeSourceFileName + "'");                
                        }
                        catch(IOException ex) {
                            System.out.println(
                                "Error reading file '" 
                                + sourceDirPath + "\\" + relativeSourceFileName + "'");                   
                        }
                    }
    
        System.out.println();
        // Append to end of file on server, in a try-catch:
        
        try{
                // Open file on server, and with append = true setting concatenate to file:
                FileWriter fileWriter = new FileWriter(fileOnServer.getName(),true);
                            BufferedWriter bufferWriter = new BufferedWriter(fileWriter);
            
                            Iterator it = linesListResultFile.iterator();
                            
                                while(it.hasNext()){
                                    bufferWriter.write((String) it.next());
                            } 
                            
                            bufferWriter.flush();
                            bufferWriter.close();
                            System.out.println("Done writing file");
             
                    }catch(IOException e){
                    System.out.println("Error writing file on server");    
                          //  e.printStackTrace();
                    }
    }  // End of processResultInSourceDirIfExistsInDestDir() method
            
}

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