Java. Почему не правильный индекс Листа?

int countOfShips = scanner.nextInt();
        List<MyOwnThread> list = new ArrayList<>();

        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                int randomIndex = (int) (Math.random() * ((countOfShips-1) - 0)) + 0;
                while (randomIndex == list.indexOf(Thread.currentThread())){
                    randomIndex = (int) (Math.random() * ((countOfShips-1) - 0)) + 0;
                }
                System.out.println(Thread.currentThread().getName());
                System.out.println(list.indexOf(Thread.currentThread()));
            }
        };

        for (int i = 0; i < countOfShips; i++) {
            list.add(i, new MyOwnThread());
            list.get(i).setHp(random.nextInt(51) + 50);
            list.get(i).setDamage(random.nextInt(11) + 20);
            list.get(i).setCoolDown(0.2f + random.nextDouble() * 1.5f);
            Thread thread = new Thread(runnable);
            list.get(i).setThread(thread);
            list.get(i).getThread().start();
            list.get(i).getThread().join();
        }