Review

class TermsHash {
  synchronized void flush(Map threadsAndFields, final SegmentWriteState state) throws IOException {
    Map childThreadsAndFields = new HashMap();
    Map nextThreadsAndFields;

    if (nextTermsHash != null)
      nextThreadsAndFields = new HashMap();
    else
      nextThreadsAndFields = null;

    Iterator it = threadsAndFields.entrySet().iterator();
    while(it.hasNext()) {

      Map.Entry entry = (Map.Entry) it.next();

      TermsHashPerThread perThread = (TermsHashPerThread) entry.getKey();

      Collection fields = (Collection) entry.getValue();

      Iterator fieldsIt = fields.iterator();
      Collection childFields = new HashSet();
      Collection nextChildFields;

      if (nextTermsHash != null)
        nextChildFields = new HashSet();
      else
        nextChildFields = null;

      while(fieldsIt.hasNext()) {
        TermsHashPerField perField = (TermsHashPerField) fieldsIt.next();
        childFields.add(perField.consumer);
        if (nextTermsHash != null)
          nextChildFields.add(perField.nextPerField);
      }

      childThreadsAndFields.put(perThread.consumer, childFields);
      if (nextTermsHash != null)
        nextThreadsAndFields.put(perThread.nextPerThread, nextChildFields);
    }
    
    consumer.flush(childThreadsAndFields, state);

    shrinkFreePostings(threadsAndFields, state);
    
    if (nextTermsHash != null)
      nextTermsHash.flush(nextThreadsAndFields, state);
  }

}