### Question:
GridTraversal implements Spliterator<double[]> { static double[] toVector(double[] start, double[] end) { double[] vec = new double[start.length]; for (int i = 0; i < vec.length; i++) { vec[i] = end[i] - start[i]; } return vec; } private  GridTraversal(PointList trajectory); private  GridTraversal(final PointList trajectory, final int startPoint, final int endPoint); @Override boolean tryAdvance(Consumer<? super double[]> action); @Override Spliterator<double[]> trySplit(); @Override long estimateSize(); @Override int characteristics(); static Stream<double[]> stream(final double[] trajectory, final int dimension, final boolean includeStart, final boolean parallel);  }### Answer:
@Test public void testVectorCreation() { final Random rand = new Random(); final long seed = rand.nextLong(); rand.setSeed(seed); for (int i = 0 ; i < 51 ; i++) { final int dimension = rand.nextInt(40)+2; try { double[] start = rand.doubles(dimension, -20000, 20000).toArray(); double[] end = rand.doubles(dimension, -20000, 20000).toArray(); double[] generatedVector = toVector(start, end); double[] expectedVector = IntStream.range(0, start.length) .mapToDouble(x -> end[x] - start[x]) .toArray(); Assert.assertArrayEquals("Vector generated", expectedVector, generatedVector, EPSILON); } catch (AssertionError|RuntimeException e) { String msg = String.format( "Test failed for seed %d, iteration %d, %d dimensions", seed, i, dimension ); throw new AssertionError(msg, e); } } }