Question

Create a java program that reads an input file named Friends.txt containing a list 4 names (create this file using Notepad) and builds an ArrayList with them. Use sout<tab> to display a menu asking the user what they want to do:  

1. Add a new name  

2. Change a name

3. Delete a name

4. Print the list  

or 5. Quit   

When the user selects Quit your app creates a new friends.txt output file.

Use methods: main( ) shouldn’t do all the work!

  

Answer 1

import java.io.*;
import java.util.*;


class Driver {

    static void addName(List<String> names) {
        Scanner obj = new Scanner(System.in);
        System.out.println("enter new name to add");
        String name = obj.nextLine();
        names.add(name);
    }

    static void changeName(List<String> names) {
        Scanner obj = new Scanner(System.in);
        System.out.println("Enter name to change");
        String source = obj.nextLine();
        System.out.println("Enter name to replace");
        String target = obj.nextLine();
        int ind = names.indexOf(source);
        names.remove(source);
        names.add(ind, target);
    }

    static void deleteName(List<String> names){
        Scanner obj = new Scanner(System.in);
        System.out.println("Enter the name to delete");
        String del = obj.nextLine();
        names.remove(del);
    }

    public static void main(String[] args) throws FileNotFoundException {
        Scanner obj = new Scanner(System.in);
        Scanner f = new Scanner(new File("Friends.txt"));
        ArrayList<String> names = new ArrayList<String>();
        while (f.hasNextLine()) {
            names.add(f.nextLine());
        }
        System.out.println("1.Add a new name\n2.Change a name\n3.Delete a name\n4.Print the list\n5.Quit");
        int ch = Integer.parseInt(obj.nextLine());
        while (ch != 5) {

            if (ch == 1) {
                addName(names);
            } else if (ch == 2) {
                changeName(names);
            } else if (ch == 3) {
                deleteName(names);
            } else if (ch == 4) {
                System.out.println("List is " + names);
            }
            System.out.println("1.Add a new name\n2.Change a name\n3.Delete a name\n4.Print the list\n5.Quit");
            ch = Integer.parseInt(obj.nextLine());
        }

    }
}

OUTPUT :

1.Add a new name
2.Change a name
3.Delete a name
4.Print the list
5.Quit
1
enter new name to add
adam
1.Add a new name
2.Change a name
3.Delete a name
4.Print the list
5.Quit
4
List is [john, joseph, jose, sam, adam]
1.Add a new name
2.Change a name
3.Delete a name
4.Print the list
5.Quit
2
Enter name to change
sam
Enter name to replace
joseph
1.Add a new name
2.Change a name
3.Delete a name
4.Print the list
5.Quit
4
List is [john, joseph, jose, joseph, adam]
1.Add a new name
2.Change a name
3.Delete a name
4.Print the list
5.Quit
3
Enter the name to delete
joseph
1.Add a new name
2.Change a name
3.Delete a name
4.Print the list
5.Quit
5

Process finished with exit code 0