code: public void serialize(final ByteBuffer buf) {
  
  		checkInvariants();
  
  		if (!sizeIsSticky)
  			trimToSize();
  
  		buf.putInt(wordsInUse);
  		for (int i = 0; i < wordsInUse; i++) {
  			buf.putLong(words[i]);
  		}
  	}
docs: Save the state of the <tt>BitSet</tt> instance to a ByteBuffer (i.e.,
  serialize it).