ThreadLocal

Look at the code below:

public class Main {
    private static final ThreadLocal<Integer> threadLocalCounter = new ThreadLocal<>();

    public static void main(String[] args) throws InterruptedException {
        class MyRunnable implements Runnable {

            @Override
            public void run() {
                if (threadLocalCounter.get() != null) {
                    threadLocalCounter.set(threadLocalCounter.get() + 1);
                } else {
                    threadLocalCounter.set(0);
                }
            }
        };

        Thread thread1 = new Thread(new MyRunnable(), "first_thread");
        Thread thread2 = new Thread(new MyRunnable(), "second_thread");
        Thread thread3 = new Thread(new MyRunnable(), "third_thread");

        // first
        thread1.start();
        thread1.join();
        // second
        thread2.start();
        thread2.join();
        // third
        thread3.start();
        thread3.join();
    }
}

What value of threadLocalCounter will each thread have?

Example of answer:

3 4 5