Deleting from a ".txt" file

package javahelp;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

public class Javahelp {


    public static void main(String[] args) {

        Customer c1 = new Customer(0, "Smith", "smith@smith.com", "123456789", "details about smith");
        Customer c2 = new Customer(1, "Jons", "jones@jones.com", "234567891", "details about jones");
        Customer c3 = new Customer(2, "Williams", "williams@williams.com", "345678912", "details about williams");

        List<Customer> customerList = new ArrayList<>();
        customerList.add(c1);
        customerList.add(c2);
        customerList.add(c3);

        Customers customers = new Customers(customerList);

        System.out.println("Saving customers 0, 1 and 2 to file...");

        customers.saveCustomers();

        /* ----- */

        System.out.println("Reading customers 0, 1 and 2 from file...");

        customers.readCustomers();
        customers.printCustomers();

        Customer c4 = new Customer(3, "Taylor", "taylor@taylor.com", "456789123", "details about taylor");
        customers.addCustomer(c4);

        customers.saveCustomers();

        System.out.println("Saving customer 3 to file...");

        /* ----- */

        System.out.println("Reading customers 0, 1, 2 and 3 from file...");

        customers.readCustomers();
        customers.printCustomers();

        /* ----- */

        System.out.println("Removing customer with id = 1 from file...");

        customers.removeCustomerById(1);
        customers.saveCustomers();

        /* ----- */


        System.out.println("Reading customers 0, 2 and 3 from file...");

        customers.readCustomers();
        customers.printCustomers();


    }


}

class Customers {

    private final File file = new File("D:\\customers.txt");
    private List<Customer> customers;

    public Customers(List<Customer> customers) {

        this.customers = customers;

    }

    public void saveCustomers() {

        try {

            if (!file.exists()) {
                file.createNewFile();
            }

            FileOutputStream fos = new FileOutputStream(file);
            ObjectOutputStream oos = new ObjectOutputStream(fos);

            oos.writeObject(this.customers);
            oos.close();

        } catch (Exception e) {

            e.printStackTrace();
            System.out.println("Could not write object");

        }

    }

    public List<Customer> readCustomers() {

        try {

            FileInputStream fis = new FileInputStream(file);
            ObjectInputStream ois = new ObjectInputStream(fis);

            this.customers = (List<Customer>)ois.readObject();
            ois.close();

        } catch (Exception e) {

            e.printStackTrace();
            System.out.println("Could not read file");

        }

        return this.customers;

    }

    public void addCustomer(Customer customer) {

        this.customers = readCustomers();
        this.customers.add(customer);


    }


    public void removeCustomerById(int id) {

        this.customers = readCustomers();

        List<Customer> list = new ArrayList<>();
        for(Customer customer : this.customers) {

            if(customer.getId() != id) {

                list.add(customer);

            }

        }

        this.customers = list;

    }

    public void printCustomers() {

        for (Customer customer : this.customers) {

            customer.printCustomer();

        }

    }

}

class Customer implements Serializable {

    private static final long serialVersionUID = 7797875735963352544L;
    private int id;
    private String name;
    private String email;
    private String phone;
    private String details;

    public Customer(int id, String name, String email, String phone, String details) {
        super();
        this.id = id;
        this.name = name;
        this.email = email;
        this.phone = phone;
        this.details = details;
    }

    public int getId() {
        return this.id;
    }

    public void printCustomer() {

        System.out.println("");
        System.out.println("////////////////////");
        System.out.println("id: " + this.id);
        System.out.println("name: " + this.name);
        System.out.println("email: " + this.email);
        System.out.println("phone: " + this.phone);
        System.out.println("details: " + this.details);
        System.out.println("////////////////////");
        System.out.println("");

    }



}