父子进程 父子线程 守护线程

public class Son extends Thread {
    private Thread parent;

    public Son(Thread parent) {
        this.parent = parent;
    }

    @Override
    public void run() {
        while (true) {
            System.out.println("thread say");

            try {
                Thread.sleep(1000);
                System.out.println(parent.isAlive());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Son son = new Son(Thread.currentThread());
        son.start();
        System.out.println("main thread ending");
    }
}