Here is my code for detecting cycles in a linked list:

do
{
    hare = hare.next();
    if (hare == back) return;

    hare = hare.next();
    if (hare == back) return;

    tortoise = tortoise.next();
}
while (tortoise != hare);
throw new AssertionError("cyclic linkage");

1. Is there a way to get rid of the code duplication inside the loop?

2. Am I right in assuming that I don't need a check after making the tortoise take a step forward? As I see it, the tortoise can never reach the end of the list before the hare (contrary to the fable).

3. Any other ways to simplify/beautify this code?