How to check if an object exists in a LinkedList in java?

Question

A LinkedList contains a set of Integer[]. Each Integer[] in the list has 2 numbers. Ex of the linked list:

Integer[]{1,2}, Integer[]{2,3}.....

Before adding another Integer[] to this LinkedList, I wanto check if another Integer[] with the same data already exists.

Ex: Object to add = Integer[] {2,3}. But this already exists in the LinkedList.

So I want to avoid adding this.

How to verify that object already exists? Is there an inbuild function that can be used? contains() didnt do the trick.

Answer 1

I think you better use a specific class if you are treating coordinates, as an Integer[] is useless for only two numbers, and will cause some problems with contains() and other List methods like .sort() as well.

You better create a Coordinate class, which will hold the two values:

public class Coordinate{
    private int x;
    private int y;

    //getters and setters, constructor
    @Override
    public boolean equals(Object o) {
        if (o == this) return true;
        if (!(o instanceof Coord)) {
            return false;
        }
        Coordinate coord = (Coordinate) o;
        return coord.x == x &&
                coord.y == y;
    }

    @Override
    public int hashCode() {
        int result = 17;
        result = 31 * result + x;
        result = 31 * result + y;
        return result;
    }
}

Then you can use:

LinkedList<Coordinate>

Note:

Note that using a Set implementation will be better here, it will prevent having duplicates in the set of coordinates, so we don't need to check for it manually.