I need a scenario to generate ConcurrentModificationException using multi-thread. Please have a look at the below code, here I am getting IllegalThreadStateException.
Not sure why this is happening and also what could be the correct example for my scenario.

public class MultiThreadFailMain {
    public static void main(String[] args) {
        List<Integer> l  = new CopyOnWriteArrayList<>(Arrays.asList(1,2,3,4));
        Thread t1 = new Thread(() -> {
            l.add(1);
        });
        Thread t2 = new Thread(() -> {
            l.add(1);
        });
        l.forEach(v -> {
            t1.start();
            t2.start();
        });
        System.out.println("n---------------");
        l.forEach(System.out::print);
    }
}