Review

Should catch NoSuchElementException around SortedMap.firstKey()

• missing/exception handling

org/apache/lucene/index/ParallelReader.java

ParallelTermEnum()

class ParallelReader.ParallelTermEnum {
    public ParallelTermEnum() throws IOException {
      field = (String)fieldToReader.firstKey();
      if (field != null)
        termEnum = ((IndexReader)fieldToReader.get(field)).terms();
    }

}

class ParallelReader.ParallelTermEnum {
    public ParallelTermEnum(Term term) throws IOException {
      field = term.field();
      IndexReader reader = ((IndexReader)fieldToReader.get(field));
      if (reader!=null)
        termEnum = reader.terms(term);
    }

}

class HandleNoFirstKey {
  void pattern(SortedMap fieldToReader) {
    String field;
    try {
      field = (String) fieldToReader.firstKey();
    } catch(NoSuchElementException e) {
      return;
    }
    if (field != null) {
      // do something with field...
    }
  }
}