Question

Write a contacts database program that presents the user with a menu that allows the user to select between the following options: (In Java)

• Save a contact.
• Search for a contact.
• Print all contacts out to the screen.
• Quit

If the user selects the first option, the user is prompted to enter a person's name and phone number which will get saved at the end of a file named contacts.txt.
If the user selects the second option, the program prompts the user asking for the name of the contact. It then searches the contacts.txt for a matching name. If found, it displays the phone number on the screen. If not found, it will display an appropriate error message.
If the user selects the third option, the program displays all contacts stored in contacts.txt in a neat table.
The program is menu driven and will repeat presenting the menu and processing choices until the user selects the fourth option to quit.
If the user selects an invalid option, an appropriate error message should be displayed.
If the user selects to print all contacts to the screen with no stored contacts, an appropriate error message should be displayed.

You may use message dialogs or make it a purely console-based application

Hints:

• in.nextLine().charAt(0); will retrieve the first character of a string read from from the keyboard for Scanner object named in.
• f.exists() returns true if the file opened using File object f exists, false otherwise. Can be used to make sure you don't throw an exception related to the file not existing.
• attached, you can find a copy of the contacts.txt file that gets created by my solution.

Answer 1

Thanks for the question.

below is the code you will be needing  Let me know if you have any doubts or if you need anything to change.

Note: the fileName used in the program, please feel free to update the fileName when you run the program in your system. Dont change it is my recommendation.

Thank You !!

===========================================================================

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

public class PhoneBook {

    private String name;
    private String phoneNumber;

    public PhoneBook(String name, String phoneNumber) {
        this.name = name;
        this.phoneNumber = phoneNumber;
    }

    public String getName() {
        return name;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }

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

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

    @Override
    public String toString() {
        return "Name: " + name + ", Phone Number: " + phoneNumber;
    }

    public static void main(String[] args) {

        try {
            loadContacts();
            char choice = '\0';
            do {
                choice = printMenuGetChoice();
                if (choice == '1') {
                    saveAContact();
                } else if (choice == '2') {
                    searchContact();
                } else if (choice == '3') {
                    printAll();
                } else if (choice == '4') {
                    saveAllData();
                    System.out.println("Thanks. Bye!");
                } else {

                }
            } while (choice != '4');
        } catch (FileNotFoundException e) {
            System.out.println("Unable to read data from file: " + fileName);
        } catch (IOException e) {
            System.out.println("Unable to save records in file: " + fileName);
        }

    }

    private static void saveAllData() throws IOException {

        PrintWriter writer = new PrintWriter(new FileWriter(fileName));
        for (PhoneBook book : contacts) {
            writer.write(book.getName() + "," + book.getPhoneNumber() + "\r\n");
            writer.flush();
        }
        writer.close();
    }

    private static void searchContact() {

        System.out.print("Enter contact name: ");
        String name = in.nextLine();
        boolean flag = true;
        for (PhoneBook contact : contacts) {
            if (contact.getName().equalsIgnoreCase(name)) {
                System.out.println("Matching record found.");
                System.out.println("Contact Phone number: " + contact.getPhoneNumber());
                flag = false;
            }
        }
        if (flag) System.out.println("No records found.");

    }

    private static void saveAContact() {

        System.out.print("Enter contact name: ");
        String name = in.nextLine();
        System.out.print("Enter phone number: ");
        String phone = in.nextLine();
        PhoneBook contact = new PhoneBook(name, phone);
        contacts.add(contact);
        System.out.println("Contact saved successfully.");
    }

    private static void printAll() {
        System.out.println("Printing all contacts");
        System.out.println("=====================");
        for (PhoneBook contact : contacts)
            System.out.println(contact);
    }

    private static void loadContacts() throws FileNotFoundException {

        File file = new File(fileName);
        if (file.exists()) {

            Scanner fileScanner = new Scanner(file);
            while (fileScanner.hasNext()) {
                String tokens[] = fileScanner.nextLine().split(",");
                PhoneBook contact = new PhoneBook(tokens[0], tokens[1]);
                contacts.add(contact);
            }
            fileScanner.close();
        }

    }

    private static final Scanner in = new Scanner(System.in);
    private static ArrayList<PhoneBook> contacts = new ArrayList<PhoneBook>();
    private static final String fileName = "contacts.txt";

    private static char printMenuGetChoice() {

        System.out.println("Type [1] - Save a contact");
        System.out.println("Type [2] - Search for a contact");
        System.out.println("Type [3] - Print all contacts");
        System.out.println("Type [4] - Quit");
        System.out.print("Enter choice: ");
        return in.nextLine().charAt(0);
    }

}