double product(TokenizedCharSequence thatDoc) {
double sum = 0.0;
for (String token : mTokenCounter.keySet()) {
int count = thatDoc.mTokenCounter.getCount(token);
if (count == 0) continue;
// tf = sqrt(count); sum += tf1 * tf2
sum += Math.sqrt(count * mTokenCounter.getCount(token));
}
return sum;
}
