code: public static BitStore asStore(BitSet bitSet, int size) {
  		if (bitSet == null) throw new IllegalArgumentException("null bitSet");
  		checkSize(size);
  		return new BitSetBitStore(bitSet, 0, size, true);
  	}
docs: Exposes a <code>BitSet</code> as a {@link BitStore}. The returned bit
  store is a live view over the bit set; changes made to the bit set are
  reflected in the bit store and vice versa. Unlike bit sets, bit stores
  have a fixed size which must be specified at construction time and which
  is not required to match the length of the bit set. In all cases, the
  bits of the bit set are drawn from the lowest-indexed bits.
  
  @param bitSet
  the bits of the {@link BitStore}
  @param size
  the size, in bits, of the {@link BitStore}
  @return a {@link BitStore} view over the bit set.