Matrice.java

        List<Vector> local = A.toRowMatrix().rows().toJavaRDD().collect();

        int M = (int) A.numRows();
        int N = (int) A.numCols();

        // List<Double> -> double[]
        double[] arr = new double[M * N];
        for (int i = 0; i < M; i++) {
            for (int j = 0; j < N; j++) {
                arr[i * N + j] = local.get(i).apply(j);
            }
        }

        DenseMatrix localMatrix = new DenseMatrix(M, N, arr);