PhoneBook.java

import java.io.*;
import java.util.ArrayList;
import java.util.Comparator;

class MalformedContactStringException extends Exception {
    public MalformedContactStringException(String str) {
        super(str);
    }
}

class Contact {
    public String firstName;
    public String lastName;
    public String phoneNumber;

    public Contact(String f, String l, String n) {
        firstName = f;
        lastName = l;
        phoneNumber = n;
    }

    public static Comparator<Contact> firstNameComparator = new Comparator<Contact>() {
        @Override
        public int compare(Contact contact, Contact contact2) {
            return contact.firstName.compareTo(contact2.firstName);
        }
    };
    public static Comparator<Contact> lastNameComparator = new Comparator<Contact>() {
        @Override
        public int compare(Contact contact, Contact contact2) {
            return contact.lastName.compareTo(contact2.lastName);
        }
    };
    public static Comparator<Contact> phoneNumberComparator = new Comparator<Contact>() {
        @Override
        public int compare(Contact contact, Contact contact2) {
            return contact.phoneNumber.compareTo(contact2.phoneNumber);
        }
    };
}

class PhoneBook {
    public ArrayList<Contact> contacts;

    public PhoneBook() {
        contacts = new ArrayList<>();
    }

    public PhoneBook(ArrayList<Contact> l) {
        contacts = l;
    }

    static PhoneBook loadFile(String path) {
        ArrayList<Contact> contactsList = new ArrayList<>();

        try(BufferedReader br = new BufferedReader(new FileReader(path))) {
            String f, l, n;

            while((f = br.readLine()) != null &&
                  (l = br.readLine()) != null &&
                  (n = br.readLine()) != null) {
                  contactsList.add(new Contact(f, l, n));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return new PhoneBook(contactsList);
    }

    void writeToFile(String path) {
        try(BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(
                new FileOutputStream(path), "utf-8"))) {
            for(Contact c : contacts) {
                writer.write(c.firstName);
                writer.write(c.lastName);
                writer.write(c.phoneNumber);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

PhoneBookForm.java

import javax.swing.*;
import javax.swing.table.AbstractTableModel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class PhoneBookForm {
    private JPanel panel1;
    private JTable table1;
    private JButton buttonAdd;
    private JButton buttonDelete;

    public PhoneBookForm() {
        buttonAdd.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent actionEvent) {
                PhoneBookTableModel tm = ((PhoneBookTableModel) table1.getModel());
                tm.phoneBook.contacts.add(new Contact("", "", ""));
                tm.fireTableDataChanged();
            }
        });
        buttonDelete.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent actionEvent) {
                PhoneBookTableModel tm = ((PhoneBookTableModel) table1.getModel());
                tm.phoneBook.contacts.remove(table1.getSelectedRow());
                tm.fireTableDataChanged();
            }
        });
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("PhoneBookForm");
        frame.setContentPane(new PhoneBookForm().panel1);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }

    private void createUIComponents() {
        table1 = new JTable(new PhoneBookTableModel());
    }
}

class PhoneBookTableModel extends AbstractTableModel {
    static private String[] headers = {"First", "Last", "Phone"};

    public PhoneBook phoneBook;

    public PhoneBookTableModel() {
        phoneBook = new PhoneBook();
    }

    public Class getColumnClass(int column) {
        return String.class;
    }

    public void setValueAt(Object value, int row, int column) {
        Contact contact = phoneBook.contacts.get(row);
        String s = (String) value;
        switch(column) {
            case 0: contact.firstName = s; break;
            case 1: contact.lastName = s; break;
            case 2: contact.phoneNumber = s; break;
        }
    }

    public String getValueAt(int row, int column) {
        Contact contact = phoneBook.contacts.get(row);
        switch(column) {
            case 0: return contact.firstName;
            case 1: return contact.lastName;
            case 2: return contact.phoneNumber;
            default: return "Empty";
        }
    }

    public int getRowCount() {
        return phoneBook.contacts.size();
    }

    public int getColumnCount() {return 3;}

    public String getColumnName(int column) {
        return headers[column];
    }

    public boolean isCellEditable(int i, int j) {return true;}
}