### Question:
NMEAFilters { public static final UnaryOperator<NMEASample> accumulatorMap() { return new AccumulatorMap(); }  static final Predicate<NMEASample> periodicFilter(long period, TimeUnit unit); static final Predicate<NMEASample> containsAllFilter(String... properties); static final UnaryOperator<NMEASample> accumulatorMap(); static final Stream<NMEASample> bearingToleranceFilter(Stream<NMEASample> stream, double bearingTolerance); static final Predicate<NMEASample> minDistanceFilter(double minDistance); static final Predicate<NMEASample> locationFilter(float maxAcceleration); static final Predicate<NMEASample> propertyAccelerationFilter(String property, float maxAcceleration); static final Predicate<NMEASample> rangeFilter(String property, float min, float max); static final Predicate<NMEASample> timeFilter();  }### Answer:
@Test public void testAccumulatorMap() { NMEAStream.Builder builder = new NMEAStream.Builder(); builder.addSample() .setProperty("a", 1); builder.addSample() .setProperty("b", 2); List<NMEASample> list = builder.build().map(NMEAFilters.accumulatorMap()).collect(Collectors.toList()); assertEquals(2, list.size()); assertTrue(list.get(0).hasProperty("a")); assertFalse(list.get(0).hasProperty("b")); assertTrue(list.get(1).hasProperty("a")); assertTrue(list.get(1).hasProperty("b")); }