### Question:
LightWeightLinkedSet extends LightWeightHashSet<T> { @Override public void clear() { super.clear(); this.head = null; this.tail = null; } LightWeightLinkedSet(int initCapacity, float maxLoadFactor,
      float minLoadFactor);  LightWeightLinkedSet(); T pollFirst(); @Override List<T> pollN(int n); @Override List<T> pollAll(); @Override @SuppressWarnings("unchecked") U[] toArray(U[] a); @Override Iterator<T> iterator(); @Override void clear();  }### Answer:
@Test public void testClear() { LOG.info("Test clear"); set.addAll(list); assertEquals(NUM, set.size()); assertFalse(set.isEmpty()); set.clear(); assertEquals(0, set.size()); assertTrue(set.isEmpty()); assertEquals(0, set.pollAll().size()); assertEquals(0, set.pollN(10).size()); assertNull(set.pollFirst()); Iterator<Integer> iter = set.iterator(); assertFalse(iter.hasNext()); LOG.info("Test clear - DONE"); }