Adding strings to an arraylist

Question

Say that I add 2 users apple and orange to an arraylist. Then I want to add newton to apple's list of friends. So apple should have 1 friend and orange still doesn't have any friends because I didn't add them yet.

My problem is that when I add newton to apple's friends, newton also shows up in orange's friends. I just need 1 friend to show up for apple and none for orange.

ArrayList<FacebookUser> users = new ArrayList<FacebookUser>();

ArrayList<FacebookUser> recommendedFriends = new ArrayList<FacebookUser>();

void friend(String newFriend)
    {
        boolean positiveChecker = false;

        for (int i = 0; i < recommendedFriends.size(); i++) 
        {

            if (recommendedFriends.get(i).toString().equalsIgnoreCase(newFriend)) 
            {
                System.out.println("Error: This friend already exists.");
                positiveChecker = true;
            }

        }
        if (positiveChecker == false) 
        {
            FacebookUser friend = new FacebookUser(newFriend, newFriend );
            recommendedFriends.add(friend);
            System.out.println(friend + " is now your friend.");
        }
        positiveChecker = false;
    }

void listFriends(String allFriends)
    {
         ArrayList<String> usersFriends = new ArrayList<String>();

            for (int i = 0; i < recommendedFriends.size(); i++) 
            {
                usersFriends.add(recommendedFriends.get(i).toString());
            }
            System.out.println(recommendedFriends);

    }

I think it's the way I set up the arraylist for the user's friends, but I'm not sure how to change it.

I don't know what you are trying to do, but recommendedFriends.get(i).toString() != formerFriend should be !recommendedFriends.get(i).toString().equals(formerFriend). — Paul Boddington
– Paul Boddington, Commented Apr 17, 2015 at 15:49
Can you organize your code so that we would understand something? Post only relevant code — Alexandru Severin
– Alexandru Severin, Commented Apr 17, 2015 at 15:49
Edited to make the code more clear. I can add any string as a user and any string I type as a friend. I make 2 users. Then I add a friend to 1 user. The problem I have is that friend shows up as friend for the 2 users, not the 1. — Ultimania
– Ultimania, Commented Apr 17, 2015 at 15:57
I don't know whether soul of newton will be happy or not once he will go through your post... — prashant thakre
– prashant thakre, Commented Apr 17, 2015 at 15:57

Andy T · Accepted Answer · 2015-04-17 15:59:23Z

3

The problem in your code is that all your friends share one pool of recommendedFriends. This means that all of apple's friends are also orange's friends as well.

ArrayList<FacebookUser> users = new ArrayList<FacebookUser>();

ArrayList<FacebookUser> recommendedFriends = new ArrayList<FacebookUser>();

As you can see above, your class contains all the FacebookUser as well as all the recommendedFriends. You will probably want to put the your list of recommendedFriends in your FacebookUser class so that each user has their own set of friends.

edited Apr 17, 2015 at 15:59

answered Apr 17, 2015 at 15:57

Andy T

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2 Comments

user180100 Over a year ago

or use a Map (or multimap).

Andy T Over a year ago

That's an option too :).

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