[Amazon] Find loop in a singly linkedlist

As the title says

http://stackoverflow.com/questions/2663115/how-to-detect-a-loop-in-a-linked-list
Floyd’s cycle-finding algorithm
Having a fast and slow pointer

boolean hasLoop(Node first) {

    if(first == null) // list does not exist..so no loop either.
        return false;

    Node slow, fast; // create two references.

    slow = fast = first; // make both refer to the start of the list.

    while(true) {

        slow = slow.next;          // 1 hop.

        if(fast.next != null)
            fast = fast.next.next; // 2 hops.
        else
            return false;          // next node null => no loop.

        if(slow == null || fast == null) // if either hits null..no loop.
            return false;

        if(slow == fast) // if the two ever meet...we must have a loop.
            return true;
    }
}