if (BRACKETS_REMOVER == null)
BRACKETS_REMOVER = new BracketsRemover();
if (SENTENCE_END_FILTER == null)
SENTENCE_END_FILTER = new SentenceEndFilter();
if (SENTENCE_START_FILTER == null)
SENTENCE_START_FILTER = new SentenceStartFilter();
extractor.addMapper(BRACKETS_REMOVER);
extractor.addMapper(SENTENCE_END_FILTER);
extractor.addMapper(SENTENCE_START_FILTER);
extractor.addMapper(SentenceLengthFilter.minFilter(4));
}