Question

JAVA FILE PROGRAM

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

• 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

Answer 1

Contact.java

public class Contact {
private String name, number;
  
public Contact()
{
this.name = "";
this.number = "";
}

public Contact(String name, String number) {
this.name = name;
this.number = number;
}

public String getName() {
return name;
}

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

public String getNumber() {
return number;
}

public void setNumber(String number) {
this.number = number;
}
  
public String toString(){ return ("Name: " + this.name + ", Number: " + this.number); }
}

ContactDB.java

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Scanner;

public class ContactDB {
  
private ArrayList<Contact> contacts;
  
public ContactDB()
{
this.contacts = new ArrayList<>();
}
  
public void readContactFile(String fileName)
{
Scanner fileReader;
int count = 0;
try
{
fileReader = new Scanner(new File(fileName));
while(fileReader.hasNextLine())
{
String line = fileReader.nextLine().trim();
String[] data = line.split(",");
this.contacts.add(new Contact(data[0], data[1]));
count++;
}
fileReader.close();
}catch(FileNotFoundException fnfe){
System.out.println("Could not locate file: " + fileName);
System.exit(0);
}
System.out.println("Finished reading " + count + " contacts.\n");
}
  
public void saveContact(String fileName)
{
Scanner sc = new Scanner(System.in);
System.out.print("\nEnter the contact name: ");
String name = sc.nextLine().trim();
while(name.length() < 0)
{
System.out.print("\nPlease enter a valid contact name: ");
name = sc.nextLine().trim();
}
System.out.print("Enter the contact number: ");
String number = sc.nextLine().trim();
while(number.length() < 0)
{
System.out.print("\nPlease enter a valid contact number: ");
number = sc.nextLine().trim();
}
  
this.contacts.add(new Contact(name, number));
writeContacts(fileName);
System.out.println(name + " has successfully been saved to contacts!\n");
}
  
private void writeContacts(String fileName)
{
FileWriter fw;
PrintWriter pw;
try
{
fw = new FileWriter(new File(fileName));
pw = new PrintWriter(fw);
  
for(Contact con : contacts)
{
pw.write(con.getName() + "," + con.getNumber() + System.lineSeparator());
}
  
pw.flush();
fw.close();
pw.close();
}catch(IOException ioe){
System.out.println("Error in writing to file: " + fileName);
System.exit(0);
}
}
  
public void searchContact()
{
Scanner sc = new Scanner(System.in);
System.out.print("\nEnter a contact name to search: ");
String name = sc.nextLine().trim();
  
boolean found = false;
int index = -1;
for(int i = 0; i < contacts.size(); i++)
{
if(contacts.get(i).getName().equalsIgnoreCase(name))
{
found = true;
index = i;
break;
}
}
if(!found)
System.out.println("\nNo matches found for contact name: " + name + ".\n");
else
System.out.println("\nMatch found:\n" + contacts.get(index).toString());
}
  
public void displayAllContacts()
{
System.out.println("ALL CONTACTS\n------------");
System.out.printf("%10s %10s %15s\n", "SL. No.", "Contact Name", "Contact Number");
int i = 0;
for(Contact con : contacts)
{
i++;
System.out.printf("%10d %10s %15s\n", i, con.getName(), con.getNumber());
}
System.out.println();
}
}

ContactDBTest.java (Driver class)

import java.util.Scanner;

public class ContactDBTest {
  
private static final String FILENAME = "contacts.txt";
  
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
ContactDB db = new ContactDB();
  
// read contacts from the file and populate the list
db.readContactFile(FILENAME);
  
// user menu
int choice;
do
{
printMenu();
choice = Integer.parseInt(sc.nextLine().trim());
switch(choice)
{
case 1:
{
db.saveContact(FILENAME);
break;
}
  
case 2:
{
db.searchContact();
break;
}
  
case 3:
{
db.displayAllContacts();
break;
}
  
case 4:
{
System.out.println("\nThank you!\nGood Bye!\n");
System.exit(0);
}
  
default:
System.out.println("\nInvalid choice!\n");
}
}while(choice != 4);
}
  
private static void printMenu()
{
System.out.print("1. Save a contact\n"
+ "2. Search for a contact\n"
+ "3. Display all contacts\n"
+ "4. Quit\n"
+ "Enter your choice: ");
}
}

******************************************************************** SCREENSHOT *******************************************************

FILE (contacts.txt - This file needs to be created before running the code, data in the file may vary)

CONSOLE OUTPUT: