7.5 Java线程：重写的示例代码

class A implements Runnable {
    public void run() {
        System.out.println(Thread.currentThread().getName());
    }
}
 
class B implements Runnable {
 
    public void run() {
        new A().run();
        new Thread(new A(), "name_thread2").run();
        new Thread(new A(), "name_thread3").start();
    }
}
 
public class Main {
 
    public static void main(String[] args) {
        new Thread(new B(), "name_thread1").start();
    }
}

输出是什么？

============================
name_thread1
name_thread1
name_thread3
============================ 

new Thread(new A(), "name_thread2").run()和 new Thread(new A(), "name_thread3").start()不同的是 new Thread(new A(), "name_thread2").run()只是会在本线程内部执行，而 new Thread(new A(), "name_thread3").start()将会新建一个线程，然后在新建的线程中执行run，所以有以上结果。