public void generateConversationLengthVsFreq() throws IOException{

        conversationLengthVsFreqFileWriter = new BufferedWriter(new FileWriter(convLengthVsFreqFile));

        TreeMap<Integer, Integer> conversationLengthVsFrequency = new TreeMap<Integer, Integer>();

        for( Long rootId : roots ) {

            //int conversationLength = adjacencyList.get(rootId).size();
            int conversationLength = bfs(rootId);

            if( !conversationLengthVsFrequency.containsKey(conversationLength) )
                conversationLengthVsFrequency.put(conversationLength, 0);

            int freq = conversationLengthVsFrequency.get(conversationLength);
            conversationLengthVsFrequency.put(conversationLength, freq+1);
        }

        for( Integer conversationLength: conversationLengthVsFrequency.keySet() ) {

            conversationLengthVsFreqFileWriter.write(conversationLength + "-" + conversationLengthVsFrequency.get(conversationLength) + '\n');
        }

        conversationLengthVsFreqFileWriter.close();

    }