in formGrams, if text.length() is less than ng, you will get a NegativeArraySizeException. this can happen if you try to do a spell check on a zero length string. this happens because getMax(int) will return 2 if the word length is zero, so in formGrams, 0 - 2 + 1 = -1 and you get the NegativeArraySizeException. i got this exception running 2.1.0, but i also took a look at the code in 2.1.3, and it looks like it will still happen, though i have not verified this.