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