### Question:
HashSet extends Set<E> { @Override public boolean contains(E object) { return backingMap.containsKey(object); } HashSet();  HashSet(int capacity);  HashSet(int capacity, float loadFactor);  HashSet(Collection<E> collection);  HashSet(E... args);   HashSet(HashMap<E, HashSet<E>> backingMap); @Override boolean add(E object); @Override void clear(); @Override boolean contains(E object); @Override boolean isEmpty(); @Override Iterator<E> iterator(); @Override boolean remove(E object); @Override int size();  }### Answer:
@Test public void testContainsNull() { assertTrue("Returned false for valid object", hs.contains(objArray[90])); assertTrue("Returned true for invalid Object", !hs.contains(new Object())); }