### Question:
LongSet implements Serializable, Cloneable, Iterable<Long> { public boolean contains(long key) { return key != NULL && key != REMOVED && keys[find(key)] != NULL; } LongSet();  LongSet(int initialCapacity); int size(); boolean isEmpty(); boolean contains(long key); boolean add(long key); @Override LongPrimitiveIterator iterator(); long[] toArray(); boolean remove(long key); boolean addAll(long[] keys); boolean addAll(LongSet keys); void clear(); void rehash(); int intersectionSize(LongSet other); @Override LongSet clone(); @Override int hashCode(); @Override boolean equals(Object other); @Override String toString();  }### Answer:
@Test public void testContains() { LongSet set = buildTestFastSet(); assertTrue(set.contains(1)); assertTrue(set.contains(2)); assertTrue(set.contains(3)); assertFalse(set.contains(4)); }