code: int createUserIndexForChains() {
  		if (m_chainIndices == null) {
  			m_chainIndices = new ArrayList<AttributeStreamOfInt32>(3);
  		}
  
  		AttributeStreamOfInt32 new_stream = new AttributeStreamOfInt32(
  				m_chainData.capacity(), -1);
  		for (int i = 0, n = m_chainIndices.size(); i < n; i++) {
  			if (m_chainIndices.get(i) == null) {
  				m_chainIndices.set(i, new_stream);
  				return i;
  			}
  		}
  		m_chainIndices.add(new_stream);
  		return m_chainIndices.size() - 1;
  	}
docs: Creates a new user index for the chains. The index values are set to -1.