I haven't looked at Anki's implementation but have you seen this one? quiz-me an SRS in Java.
Basically it goes like this
public static void calcuateInterval(Card card) {
if (card.getEFactor() < 3) {
card.setCount(1);
}
int count = card.getCount();
int interval = 1;
if (count == 2) {
interval = 6;
} else if (count > 2) {
interval = Math.round(card.getInterval() * card.getEFactor());
}
card.setInterval(interval);
}
If you really want Anki's algorithm, look through the source of Anki in Android available in Github. It is GPL though so you might need to buy a license.