Remove duplicate from custom ArrayList by parameter

Question

I'm facing a problem that I don't arrive to resolve:

I read an ArrayList from the phone:

ArrayList<Game> gameResult = writeRead.getArrayList(this);

I put the object gamer from each game in a new ArrayList:

ArrayList<Gamer> gamerList = new ArrayList<>();
for (int i = 0; i < gameResult.size(); i++) {
    gamerList.add(gameResult.get(i).getWinnerGamer());
}

now, what I would like is to:

add Gamer in an ArrayList if not already present
if present, add ++ to a parameter named LeaderPoints
sort by point

It's about a leaderboard activity with a custom ArrayList, but I don't arrive to do it.

All my code:

private void setGamerList() {

    ArrayList<Game> gameResult = writeRead.getArrayList(this);
    ArrayList<Gamer> gamerList = new ArrayList<>();
    ArrayList<Gamer> gamerNoDuplicate = new ArrayList<>();

    if (gameResult != null) {

        for (int i = 0; i < gameResult.size(); i++) {
            gamerList.add(gameResult.get(i).getWinnerGamer());
        }
    }

    Log.i(TAG, "--------------------------------");

    Collections.sort(mGamerList, (o1, o2) ->
        o2.getLeaderboardScore().compareTo(o1.getLeaderboardScore()));
}

can you show the Gamer class

Ryuzaki L
– Ryuzaki L

2019-02-26 12:59:48 +00:00
Commented Feb 26, 2019 at 12:59 — Ryuzaki L
– Ryuzaki L, Commented Feb 26, 2019 at 12:59

Akash Shah · Accepted Answer · 2019-02-26 13:14:47Z

1

Override equals and hashCode methods of your Gamer object class.

Then before adding object to ArrayList, check Arraylist.contains(), if yes then you can either call ArrayList.indexOf() method to get that object instance in ArrayList, increment the value of LeaderPoints and call ArrayList.set() to set back the instance at the same position.

edited Feb 26, 2019 at 13:14

Akash Shah

6165 silver badges17 bronze badges

answered Feb 26, 2019 at 13:09

Rajen Raiyarela

5,6344 gold badges23 silver badges41 bronze badges

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Comments

Vladyslav Diachenko · Accepted Answer · 2019-02-26 13:57:50Z

writeRead.getArrayList(this).stream()
            .map(Game::getWinnerGamer)
            .collect(Collectors.groupingBy(Gamer::getName, Collectors.summingInt(Gamer::getLeaderboardScore)))
            .entrySet()
            .stream()
            .sorted(Comparator.comparing(Map.Entry<String, Integer>::getValue).reversed())
            .map(entry -> new Gamer(entry.getKey(), entry.getValue()))
            .collect(Collectors.toList());

Steps:

extract winner
group winners by name and sum their scores. As result you will get Map
get entrySet of this Map
open stream on this entySet
sort by scores in DESC direction
map entry to Gamer (create new gamer instance for each entry)
collect to list

My answer based on assumption that you have such structure :

class Game {
    private Gamer winnerGamer;
    // getter & setter
}

class Gamer {
    private String name;
    private Integer leaderboardScore;
    // getters & setters && AllArgsContructor
}

BTW: if you override equals and hash code in class Gamer you can avoid Gamer recreation with this:

writeRead.getArrayList(this).stream()
            .map(Game::getWinnerGamer)
            .collect(Collectors.groupingBy(Function.identity(), Collectors.summingInt(Gamer::getLeaderboardScore)))
            .entrySet()
            .stream()
            .sorted(Comparator.comparing(Map.Entry<Gamer, Integer>::getValue).reversed())
            .map(Map.Entry::getKey)
            .collect(Collectors.toList());

you are welcome :) Streams help us not to write redundant code ;)

Rakesh · Accepted Answer · 2019-02-26 13:30:08Z

you can use Set Instead of ArrayList for unique value.

override HashCode and Equal Method.

Set<Gamer> gamerNoDuplicate=new HashSet();
if (gameResult != null) {
    for (int i = 0; i < gameResult.size(); i++) {
        if(gamerNoDuplicate.contains(gameResult.get(i).getWinnerGamer()){
            Gamer alreadyExist = gamerNoDuplicate.indexOf(gameResult.get(i).getWinnerGamer());
            alreadyExist.setLeaderPoints(alreadyExist.getLeaderPoints()+ gameResult.get(i).getWinnerGamer().getLeaderPoints());
        }else{
            gamerNoDuplicate.add(gameResult.get(i).getWinnerGamer());
        }
    }
}

Look good ! but i got a error on indexOf ... i don't know why ?

Joffrey B. · Accepted Answer · 2019-02-27 12:18:32Z

Finally i did it like this :

and it work perfectly Thanks !

if (gameResult != null) {


        for (int i = 0; i < gameResult.size(); i++) {
            gamerList.add(gameResult.get(i).getWinnerGamer());
        }

        /* --------- */


        for (int i = 0; i < gamerList.size(); i++) {
            Gamer gamer = gamerList.get(i);
            gamer.setLeaderboardScore(1);
            boolean isInArray = false;

            if (!gamerNoDuplicate.isEmpty()) {
                for (int j = 0; j < gamerNoDuplicate.size(); j++) {
                    if (gamer.getName().equals(gamerNoDuplicate.get(j).getName())) {
                        gamerNoDuplicate.get(j).addLeaderscorePoint();
                        isInArray = true;
                    }
                }

                if (!isInArray) {
                    gamerNoDuplicate.add(gamer);
                }

            } else gamerNoDuplicate.add(gamer);
        }
    }

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