code: boolean scanIsEmpty() {
  		// This 'slow' implementation is still faster than any external one
  		// could be
  		// (e.g.: (bitSet.length() == 0 || bitSet.nextSetBit(0) == -1))
  		// especially for small BitSets
  		// Depends on the ghost bits being clear!
  		final int count = numWords;
  
  		for (int i = 0; i < count; i++) {
  			if (bits[i] != 0)
  				return false;
  		}
  
  		return true;
  	}
docs: Scans the backing store to check if all bits are clear. The method is
  deliberately not called "isEmpty" to emphasize it is not low cost (as
  isEmpty usually is).
  
  @return true if all bits are clear.