Client.java

public class Client {
    private Integer clientId;
    private String name;
    private String email;
    private String phoneNumber;
    private String country;

    public Client(Integer clientId, String name, String email, String phoneNumber, String country) {
        this.clientId = clientId;
        this.name = name;
        this.email = email;
        this.phoneNumber = phoneNumber;
        this.country = country;
    }

    // Getters and Setters
    public Integer getClientId() {
        return clientId;
    }

    public void setClientId(Integer clientId) {
        this.clientId = clientId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }

    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    // Override toString method for CSV format
    @Override
    public String toString() {
        return clientId + "," + name + "," + email + "," + phoneNumber + "," + country;
    }
}

Main.java**

 import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("input.txt"))) {
            FileUtility fileUtility = new FileUtility();
            Client[] clients = fileUtility.readFileData(br);
            Arrays.sort(clients, Comparator.comparing(Client::getClientId));
            fileUtility.writeDataToFile(clients);
            System.out.println("Output file generated successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
FileUtility.java**
  
  import java.io.*;
import java.util.*;

public class FileUtility {
    public Client[] readFileData(BufferedReader br) throws IOException {
        List<Client> clientList = new ArrayList<>();
        String line;
        while ((line = br.readLine()) != null) {
            String[] parts = line.split(",");
            Integer clientId = Integer.parseInt(parts[0].trim());
            String name = parts[1].trim();
            String email = parts[2].trim();
            String phoneNumber = parts[3].trim();
            String country = parts[4].trim();
            clientList.add(new Client(clientId, name, email, phoneNumber, country));
        }
        br.close();
        return clientList.toArray(new Client[0]);
    }

    public void writeDataToFile(Client[] clientArray) throws IOException {
        try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.csv"))) {
            for (Client client : clientArray) {
                writer.write(client.toString());
                writer.newLine();
            }
        }
    }
}