Java比较2D数组与arrayList内部的2D数组

Question

I am having problems checking if the arrays inside one array are the same as my arrays in a list. This is the problem code, it does not seem to stop duplicates from being added. Arrays.equals() doesn't seem to work either:

if(!uniqueTiles.contains(playerPositions[i])) {
    uniqueTiles.add(playerPositions[i]);
}

Here is the entire method so far:

// gets the area in fishZone that the bot should walk to, based on the positions 
    // of clusters of players

    List<Player> players = getPlayers().getAll();



    int validPlayerCount = 0;

    // count valid players
    for (int i = 0; i < players.size(); i++) {
        if((players.get(i).getName() != myPlayer().getName()) && fishingZone.contains(players.get(i))) {
            validPlayerCount++;
        }
    }

    int[][] playerPositions = new int[validPlayerCount][2];
    List<int[]> uniqueTiles = new ArrayList<int[]>();

    // put the x and y coordinates of all nearby valid players into a 2d array
    for (int i = 0; i < validPlayerCount; i++) {
            playerPositions[i][0] = players.get(i).getX();
            playerPositions[i][1] = players.get(i).getY();



            if(!uniqueTiles.contains(playerPositions[i])) {
                uniqueTiles.add(playerPositions[i]);
            }
    }

As you can see uniqueTiles is an arrayList because it needs a flexible size, and playerPositions is a 2d array.

Answer 1

Do not use List s if you don't want duplicates:

Unlike sets, lists typically allow duplicate elements.

In Java, object comparison is made using the methods equals and hashCode . You can use third party libraries such as Apache Commons Lang's EqualsBuilder and HashCodeBuilder to help you implementing those.

Look at the source code of List.contains if you're curious.

Answer 2

Try this method :

TreeSet<Integer[]> set = new TreeSet<>((o1, o2) -> Arrays.deepEquals(o1, o2) ? 0 : 1);
    set.add(new Integer[]{1, 2, 4});
    set.add(new Integer[]{1, 2, 4});
    set.add(new Integer[]{1, 2, 4});
    System.out.println(set);