java basic threads

class HelloThread extends Thread {

    @Override
    public void run() {
        System.out.println("Hello from a thread1!");

        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        System.out.println("Hello from a thread2!");
    }

}

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");
        var helloThread = new HelloThread();
        helloThread.start();

    }
}