/**
* Count words in sentences.
*
* @param sentences The sentences.
* @param stopWords Stop words.
* @return Map of words to WordCountAndSentence objects.
*/
public static <W extends Comparable> Map<String, WordCountAndSentences> countWordsInSentences(
List<List<W>> sentences, StopWords stopWords) {
// Holds map between each word
// and the word's count and appearance.
Map<String, WordCountAndSentences> wordCounts = new TreeMap<String, WordCountAndSentences>();
// Note if we are filtering using
// a stop word list.
boolean checkStopWords = (stopWords != null);
// Loop over sentences.
for (int i = 0; i < sentences.size(); i++) {
// Get next sentence.
List<W> sentence = sentences.get(i);
// Loop over words in sentence.
for (int j = 0; j < sentence.size(); j++) {
// Get next word.
W word = sentence.get(j);
// Get string version of word in
// lower case.
String lcWord = word.toString().toLowerCase();
// Ignore punctuation and symbols.
if (CharUtils.isPunctuationOrSymbol(lcWord)) {
}
// Ignore stop words.
else if (checkStopWords && stopWords.isStopWord(lcWord)) {
} else {
// Create/update count and appearance data
// for this word.
WordCountAndSentences wcs = wordCounts.get(lcWord);
if (wcs == null) {
wcs = new WordCountAndSentences(lcWord);
wordCounts.put(lcWord, wcs);
}
wcs.count++;
wcs.sentences.add(i);
}
}
}
return wordCounts;
}
/**
* Summarize text.
*
* @param sentences Tokenized sentences to summarize.
* @param summarySentences Maximum number of sentences to return in the summary.
* @return Summary of the input text.
*/
public <T extends Comparable> List<Integer> summarize(
List<List<T>> sentences, int summarySentences) {
// Get word counts ignoring stop words.
Map<String, WordCountAndSentences> wordCounts =
WordCountUtils.countWordsInSentences(sentences, new BuckleyAndSaltonStopWords());
// Sort the counts into descending
// order by count.
List<WordCountAndSentences> wcsData = new SortedArrayList<WordCountAndSentences>();
Iterator<String> iterator = wordCounts.keySet().iterator();
while (iterator.hasNext()) {
wcsData.add(wordCounts.get(iterator.next()));
}
// Holds summary sentence indices.
Set<Integer> summarySentencesSet = new TreeSet<Integer>();
// Use up to 100 most commonly used words.
int maxWords = Math.min(100, wcsData.size());
// For each commonly word word,
// find the first sentence in which
// that word appears, and add it to the
// summary sentences collection.
for (int i = 0; (i < wcsData.size()) && (summarySentencesSet.size() < summarySentences); i++) {
WordCountAndSentences wcs = wcsData.get(i);
if (CharUtils.isNumber(wcs.word.toString())) continue;
if (CharUtils.hasDigit(wcs.word.toString())) continue;
Integer[] sentenceNumbers =
(Integer[]) wcs.sentences.toArray(new Integer[wcs.sentences.size()]);
summarySentencesSet.add(sentenceNumbers[0]);
}
// Return indices of selected
// summary sentences.
return new ArrayList<Integer>(summarySentencesSet);
}