private void init(int minGram, int maxGram)
{
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.termAtt = AddAttribute<ITermAttribute>();
this.offsetAtt = AddAttribute<IOffsetAttribute>();
}