i need to create a ArrayList for my class project

Question

I have written what I can and have come to a point where I cant figure out why it is not saving the data. Below is the File Test, then the File, and the Array file I have made. please some help...

$

import java.util.Scanner;

public class FriendsListTest

{

public static void main( String[] args)
{
    FriendsList friendsList = new FriendsList();

    char selection;
    Scanner input = new Scanner( System.in );
    do
        {
            //display menu
            System.out.println("\n--------------");
            System.out.println("Main Menu\n");
            System.out.println("1. Add a friend ");
            System.out.println("2. Delete a friend ");
            System.out.println("3. Show List ");
            System.out.println("4. Exit");

            //selection results
            selection = input.next().charAt(0);

            switch(selection){
            case '1':
                FriendsList.AddFriends();
                break;
            case '2':
                FriendsList.RemoveFriend();
                break;
            case '3':
                FriendsList.DisplayArray();     
                break;
            case '4':
                break;
            default:
                System.out.println("Invalid Selection");
        }//end Switch   

}while( selection != 4);//end do

}//end main

}//end FriendsListTest

$ $

import java.util.Scanner;
import java.util.ArrayList;

public class FriendsList
{

public static void AddFriends()
{
    Scanner input = new Scanner( System.in );
    ArrayList<Friends> friend = new ArrayList<Friends>(20);

    System.out.println("\n--------------");
    System.out.println("Please enter Name");
    String name = input.nextLine(); //reads name
    System.out.println("Please enter Age");
    int Age = input.nextInt();
    friend.add(new Friends( Age, name));

}//end AddFriends
public static void RemoveFriend()
{
    ArrayList<Friends> friend = new ArrayList<Friends>(20);
    Scanner input = new Scanner( System.in );

    System.out.println("\n--------------");
    System.out.println("Please enter Name of person you wish you remove");
    String name = input.nextLine();
    friend.remove(name);

}//End RemoveFriend
public static void DisplayArray()
{
    ArrayList<Friends> friend = new ArrayList<Friends>(20);
    System.out.print(friend);

}//end DisplayArray

 }//end class FriendsList

$ $

 class Friends
 {
    private String nName;
    private int nAge;
    public Friends(int Age, String name)
{
    nName = name;
    nAge = Age;
}
public String getName()
{
    return nName;
}
public int getAge()
{
    return nAge;
}
}//end class person

Ok after your suggestions I was able to get it to store data but now I have the problem of removing data. It doesn't throw any errors when removing data but the data remains. If I would repost the program if you with the edits that I have done.

Answer 1

You're creating a new ArrayList whenever you want to add or remove a Friend rather than acting on an ArrayList of the class. Do the latter please not the former. In other words give your class an ArrayList<Friend> variable and do your friend additions and removals on that array list.

Answer 2

you need to understand what's the life scope of a local variable, apparently you need a member variable here. FYI: What is the difference between a member variable and a local variable?

Answer 3

You're creating a new ArrayList<Friend> every time Add, Remove, or Display is called. You need to save your list as a class-level field.

It would also be best if you took away all of the static methods and made them all instance level. Then your FriendList instance would be associated with a particular list of friends.

For example:

public class FriendsList
{

private List<Friend> friends = new ArrayList<Friend>();

public void addFriends()
{
    Scanner input = new Scanner( System.in );

    System.out.println("\n--------------");
    System.out.println("Please enter Name");
    String name = input.nextLine(); //reads name
    System.out.println("Please enter Age");
    int Age = input.nextInt();
    friends.add(new Friends( Age, name));

}//end AddFriends
public void removeFriend()
{
    Scanner input = new Scanner( System.in );

    System.out.println("\n--------------");
    System.out.println("Please enter Name of person you wish you remove");
    String name = input.nextLine();
    friends.remove(name);

}//End RemoveFriend
public void displayArray()
{
    System.out.print(friends);
}

That would mean that you need to actually use your friendList instance variable in your main method rather than calling those methods in a static manner (ie use friendsList.addFriends() instead of FriendList.addFriends() )

Also, notice that I made the first letter of my methods lowercase. That's pretty much a standard in Java.

EDIT

Your current code is trying to remove a String from your List<Friends> . It's not removing anything because there are no String elements in the List . You're going to have to iterate through the list and find the Friend whose name is name

So your remove method should look something like this:

public void removeFriend()
{
  Scanner input = new Scanner( System.in );

  System.out.println("\n--------------");
  System.out.println("Please enter Name of person you wish you remove");
  String name = input.nextLine(); 

  Friends friendToRemove = null;
  for (Friends friend : friends) {
    if (name.equals(friend.getName()) {
      friendToRemove = friend;
    }
  } 

  if (friendToRemove != null) {
    friends.remove(friendToRemove)
  }

}//End RemoveFriend