How to add arrays to ArrayList?

Question

I have an int[3][3] array and it contains only 0 or 1 values, if the value is 1 I want to add the coordinates of this value in the ArrayList as int[2] array, but I don\'t know w

Answer 1

If you are putting Points into an ArrayList, I suggest you create a Point object that takes coordinates. Please refer to the code below. Sorry for the lengthy reply.

import java.util.ArrayList;
import java.util.Arrays;

public class SomeClass {

    static class Point {

        int[] coordinates;

        public Point(int x, int y) {
            this.coordinates = new int[2];
            this.coordinates[0] = x;
            this.coordinates[1] = y;
        }

        public Point() {
            this(0,0);
        }

        public Point(int[] coordinates) {
            this.coordinates = coordinates;
        }
    }

    public static void main(String[] args) {
        SomeClass myClass = new SomeClass();
        Point a = new Point();
        Point b = new Point(5,5);
        Point c = new Point(new int[]{3,4});

        ArrayList arr = new ArrayList();

        // adding
        arr.add(a);
        arr.add(b);
        arr.add(c);

        // retrieve one object
        int index = 0;
        Point retrieved = arr.get(index);
        System.out.println("Retrieved coordinate: " + Arrays.toString(retrieved.coordinates));
        retrieved.coordinates[0] = 15;
        retrieved.coordinates[1] = 51;
        System.out.println("After change, retrieved coordinate: " + Arrays.toString(retrieved.coordinates));
        System.out.println("After change, accessing arraylist index: " + Arrays.toString(arr.get(index).coordinates));

        // we received a pointer to the array
        // changed values are automatically reflected in the ArrayList

    }
}

These are the values you will get...

Retrieved coordinate: [0, 0]
After change, retrieved coordinate: [15, 51]
After change, accessing arraylist index: [15, 51]