Matrice.java

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

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

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);