AddressBook

import java.util.Arrays;
import java.util.Scanner;

public class AddressBook {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter number of contacts you want to input: ");
        int numberOfContacts = Integer.parseInt(scanner.nextLine());
        while (numberOfContacts <= 0) {
            System.out.println("Invalid number. Must be positive and greater than 0.");
            System.out.print("Enter number of contacts you want to input: ");
            numberOfContacts = Integer.parseInt(scanner.nextLine());

        }
        Contact[] contacts = new Contact[numberOfContacts];

        for (int i = 0; i < contacts.length; i++) {
            System.out.print("What is your last name? ");
            String last = scanner.nextLine();
            System.out.print("What is your first name? ");
            String first = scanner.nextLine();
            System.out.print("What is your email? ");
            String email = scanner.nextLine();

            contacts[i] = new Contact(last, first, email);
        }

		Arrays.sort(contacts); // this sorts the array of Contact objects according to last name.

        for (Contact c : contacts) {
            System.out.printf("First name: %s\nLast Name: %s\nEmail: %s\n\n",c.getFirstName(),
                    c.getLastName(), c.getEmail());
        }

    }

}