private void init(Version version, int minGram, int maxGram, bool edgesOnly) { if (!version.onOrAfter(Version.LUCENE_44)) { throw new System.ArgumentException("This class only works with Lucene 4.4+. To emulate the old (broken) behavior of NGramTokenizer, use Lucene43NGramTokenizer/Lucene43EdgeNGramTokenizer"); } charUtils = version.onOrAfter(Version.LUCENE_44) ? CharacterUtils.getInstance(version) : CharacterUtils.Java4Instance; if (minGram < 1) { throw new System.ArgumentException("minGram must be greater than zero"); } if (minGram > maxGram) { throw new System.ArgumentException("minGram must not be greater than maxGram"); } this.minGram = minGram; this.maxGram = maxGram; this.edgesOnly = edgesOnly; charBuffer = CharacterUtils.newCharacterBuffer(2 * maxGram + 1024); // 2 * maxGram in case all code points require 2 chars and + 1024 for buffering to not keep polling the Reader buffer = new int[charBuffer.Buffer.Length]; // Make the term att large enough termAtt.resizeBuffer(2 * maxGram); }