下面是学习如何捕获多线程异常的一个范例：
import java.util.concurrent.*;
class ExceptionThread2 implements Runnable {
public void run() {
Thread t = Thread.currentThread();
System.out.println("run() by " + t);
System.out.println(
"eh = " + t.getUncaughtExceptionHandler());
throw new RuntimeException();
}
}
class MyUncaughtExceptionHandler implements
Thread.UncaughtExceptionHandler {
public void uncaughtException(Thread t, Throwable e) {
System.out.println("caught " + e);
}
}
class HandlerThreadFactory implements ThreadFactory {
public Thread newThread(Runnable r) {
System.out.println(this + " creating new Thread");
Thread t = new Thread(r);
System.out.println("created " + t);
t.setUncaughtExceptionHandler(
new MyUncaughtExceptionHandler());
System.out.println(
"eh = " + t.getUncaughtExceptionHandler());
return t;
}
}
public class CaptureUncaughtException {
public static void main(String[] args) {
ExecutorService exec = Executors.newCachedThreadPool(
new HandlerThreadFactory());
exec.execute(new ExceptionThread2());
}
}

但奇怪的是，这个demo创建了两个线程，明明只有一个exec.execute(new ExceptionThread2());啊
谁知道是为什么？

而且运行之后这个程序并没有结束，再输出：caught java.lang.RuntimeException之后也没有退出。为什么？

我日，16年的帖子，还没人回复，你知道啥原因了吗？