### Question:
HugeAtomicBitSet { public long cardinality() { long setBitCount = 0; for (long wordIndex = 0; wordIndex < bits.size() ; wordIndex++) { setBitCount += Long.bitCount(bits.get(wordIndex)); } return setBitCount; } private  HugeAtomicBitSet(HugeAtomicLongArray bits, long numBits); static HugeAtomicBitSet create(long size, AllocationTracker tracker); boolean get(long index); void set(long index); void set(long startIndex, long endIndex); boolean getAndSet(long index); void flip(long index); long cardinality(); boolean isEmpty(); long capacity(); long size(); void clear(); void clear(long index); BitSet toBitSet();  }### Answer:
@Test void testCardinality() { var bitSet = HugeAtomicBitSet.create(42, AllocationTracker.empty()); assertEquals(0L, bitSet.cardinality()); bitSet.set(41); assertEquals(1L, bitSet.cardinality()); for (long i = 0; i < bitSet.size(); i++) { bitSet.set(i); } assertEquals(42L, bitSet.cardinality()); }