Доступ к элементу объекта класса

import java.util.Arrays;
 
public class Matrix {
 
    private final int height;
    private final int width;
    private final double[][] data;
 
    public Matrix(int height, int width) {
        this.height = height;
        this.width = width;
        this.data = new double[height][width];
    }
 
    public Matrix(double[][] matrix) {
        this.data = new double[matrix.length][];
        this.height = matrix.length;
        this.width = matrix[0].length;
        for (int i = 0; i < matrix.length; ++i) {
            data[i] = Arrays.copyOf(matrix[i], matrix[i].length);
        }
    }
 
    private Matrix(double[][] matrix, int unused) {
        this.data = matrix;
        this.height = matrix.length;
        this.width = matrix[0].length;
    }
 
    public void set(int i, int j, double value) {
        data[i][j] = value;
    }
 
    public double get(int i, int j) {
        return data[i][j];
    }
 
    public int getHeight() {
        return height;
    }
 
    public int getWidth() {
        return width;
    }
 
    public Matrix add(Matrix other) {
        if (getHeight() != other.getHeight() || getWidth() != other.getWidth()) {
            throw new IllegalArgumentException("matrices must have same sizes");
        }
        double[][] result = new double[getHeight()][getWidth()];
        for (int i = 0; i < getHeight(); ++i) {
            for (int j = 0; j < getWidth(); ++j) {
                result[i][j] = get(i, j) + other.get(i, j);
            }
        }
        return new Matrix(result, 0);
    }
 
    @Override
    public String toString() {
        return "Matrix{" +
                "height=" + height +
                ", width=" + width +
                ", data=" + Arrays.deepToString(data) +
                '}';
    }
}

public class Testy {
    public static void main(String[] args) {
        Matrix a = new Matrix(new double[][]{{0, 1, 2}, {3, 4, 5}, {6, 7, 8}});
        Matrix b = new Matrix(new double[][]{{8, 7, 6}, {5, 4, 3}, {2, 1, 0}});
        Matrix c = a.add(b);
 
        System.out.println("a[1][1] = " + a.get(1, 1));
        System.out.println("a[0][2] = " + a.get(0, 2));
 
        System.out.println("a = " + a);
        System.out.println("b = " + b);
        System.out.println("a + b = " + c);
    }
}