Java Utililty Methods Matrix to Vector

double[] v = new double[m.length];
for (int i = 0; i < v.length; i++) {
    v[i] = m[i][0];
return v;

if (matrix == null || matrix.length <= 0 || matrix[0].length <= 0) {
    return null;
int[] vector = new int[matrix.length * matrix[0].length];
int index = 0;
for (int i = 0; i < matrix.length; i++) {
    for (int j = 0; j < matrix[0].length; j++, index++) {
        vector[index] = matrix[i][j];
...

if (b.length == 0 || a.length == 0 || a[0].length == 0 || b.length != (M * N) || a.length != M
        || a[0].length != N) {
    throw new IllegalArgumentException(
            "The number of data points in both arrays must be equal and different from zero.");
for (int i = 0; i < M; i++) {
    System.arraycopy(a[i], 0, b, N * i, N);

checkDimension(a);
if (a.length != M || a[0].length != N || b.length == 0 || b.length != (M * N)) {
    throw new IllegalArgumentException(
            "The number of data points in both arrays must be equal and different from zero.");
for (int i = 0; i < M; i++) {
    System.arraycopy(a[i], 0, b, N * i, N);

int w1 = w.length;
int w2 = w[0].length;
int v1 = v.length;
if (w2 != v1) {
    System.out.println("Matrix dimensions do not agree...");
    System.exit(-1);
double[] result = new double[w1];
...

assert hasShape(V, l1, l2);
assert d != null;
assert w != null;
assert a != null;
assert d.length >= l2;
assert w.length >= l2;
assert a.length >= l1;
for (int i = 0; i < l1; i++) {
...