import org.apache.lucene.analysis.position.PositionFilter; //导入依赖的package包/类
@Override
public PositionFilter create(TokenStream input) {
  return new PositionFilter(input, positionIncrement);
}
 

import org.apache.lucene.analysis.position.PositionFilter; //导入依赖的package包/类
public static List<String> getNgrams(String text, int N) throws IOException {
	
	List<String> tokens = new ArrayList<String>();
	
	
	Reader reader = new StringReader(text);
	// Tokenizer
	//StandardTokenizer tokenizer = new StandardTokenizer(Version.LUCENE_46, reader);
	
	LowerCaseTokenizer tokenizer = new LowerCaseTokenizer(Version.LUCENE_46, reader);
	
	// Filters
	LowerCaseFilter lowerCaseFilter = new LowerCaseFilter(Version.LUCENE_46, tokenizer); 
	KStemFilter kStemFilter = new KStemFilter(lowerCaseFilter);
	
	CharArraySet stopwords = StopAnalyzer.ENGLISH_STOP_WORDS_SET;
	StopFilter stopFilter = new StopFilter(Version.LUCENE_46, kStemFilter, stopwords);

	TokenStream ts;
	if(N > 1) {

		PositionFilter positionFilter = new PositionFilter(stopFilter);
		
		//@SuppressWarnings("resource")
		//ShingleFilter shingleFilter = new ShingleFilter(positionFilter, N, N);
		//shingleFilter.setOutputUnigrams(false);
		
		@SuppressWarnings("resource")
		ShingleFilter shingleFilter = new ShingleFilter(positionFilter, 2, N);
		shingleFilter.setOutputUnigrams(true);
		
		ts = shingleFilter;
	}
	else {
		ts = stopFilter;
	}
	
	CharTermAttribute charTermAtt = ts.addAttribute(CharTermAttribute.class);
	
	ts.reset();
	while (ts.incrementToken()) {
		String token = charTermAtt.toString();
		if(token.length()>1)
			tokens.add(token);
      }
      ts.end();  
      ts.close();
      
	return tokens;
}