Почему без join не видит метод printResult()?

public static volatile BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

    public static void main(String[] args) throws InterruptedException {
        Read3Strings t1 = new Read3Strings();
        Read3Strings t2 = new Read3Strings();
        t1.start();
        t1.join();
        t2.start();
        t2.join();
        //add your code here - добавьте код тут
        t1.printResult();
        t2.printResult();
    }

    public static class Read3Strings extends Thread {
        ArrayList<String> finals = new ArrayList<String>();

        @Override
        public void run() {
            try {
                for (int i = 0; i < 3; i++) {
                    finals.add(reader.readLine());
                }
            } catch (IOException e) {
            }
        }

        public void printResult() {
            for (String lol : finals
            ) {
                System.out.print(lol + " ");
            }
            System.out.println();
        }

    }
    //add your code here - добавьте код тут
}