线程的实现方式一般是继承thread类或者实现runnable接口,最近在看Android watchdog的时候发现它是一个线程,但是并没有extends Thread,编译是能过的,并且这是Android framework的源码,肯定是没有问题的,但是不理解,想请教下各位专家为什么可以这样写,我参照的是Android S的源码,代码位置frameworks\base\services\core\java\com\android\server\Watchdog.java
```java
public class Watchdog {
static final String TAG = "Watchdog";
......
private static Watchdog sWatchdog;
private final Thread mThread;
......
private Watchdog() {
mThread = new Thread(this::run, "watchdog");
}
public void start() {
mThread.start();
}
}
```