Need help understanding why one code works and the other doesn't !

Hello, I couldn't manage to find the solution, so I snooped a bit in the help section. I stumbled upon this working code :

public static int calculateHorsesFinished(List<Horse> horses) throws InterruptedException {
        int finishedCount = 0;

        for (int i = 0;i< horses.size();i++){
            if (horses.get(i).isFinished()){
                finishedCount++;
            }
            else {
                System.out.println("Waiting for " + horses.get(i).getName());
                horses.get(i).join();
            }
        }

        return finishedCount;
    }

I thought my code was functionally identical, yet it doesn't work. Here it is :

public static int calculateHorsesFinished(List<Horse> horses) throws InterruptedException {
        int finishedCount = 0;

        for (int i = 0; i < horses.size(); i++) {
            Horse horse = horses.get(i);
            if(horse.isFinished){
                finishedCount++;
            } else{
                System.out.println(String.format("Wait for %s", horse.getName()));
                horse.join();
            }
        }

        return finishedCount;
}

Can anyone explain the difference to me please ?