### Question:
Line extends AUnboundedLine implements ILine { @Override public Optional<Double> getYIntercept() { return LineMath.getYIntercept(this); } private  Line(final IVector2 supportVector, final IVector2 directionVector); static ILine fromPoints(final IVector2 supportPointA, final IVector2 supportPointB); static ILine fromDirection(final IVector2 supportVector, final IVector2 directionVector); @Override ILine copy(); @Override final boolean equals(final Object other); @Override final int hashCode(); @Override Optional<Double> getYIntercept(); @Override Optional<Double> getXValue(final double y); @Override Optional<Double> getYValue(final double x); @Override ILine getOrthogonalLine(); @Override IVector2 closestPointOnLine(final IVector2 point); @Override ILine toLine(); @Override Optional<IVector2> intersectLine(final ILine other); @Override Optional<IVector2> intersectHalfLine(final IHalfLine halfLine); @Override Optional<IVector2> intersectSegment(final ILineSegment segment); @Override String toString();  }### Answer:
@Test public void testGetYIntercept() { for (int degAngle = -90; degAngle <= 90; degAngle += 10) { double angle = Math.toRadians(degAngle); IVector2 sV = Vector2.fromXY(1, 0); IVector2 dV = Vector2.fromAngle(angle); ILine line = Line.fromDirection(sV, dV); if (Math.abs(degAngle) == 90) { assertThat(line.getYIntercept(), isNotPresent()); } else { double expected = SumatraMath.tan(-angle); assertThat(line.getYIntercept(), isPresentAnd(closeTo(expected, ACCURACY))); } } }