“Thread.setDefaultUncaughtExceptionHandler”的构造函数和静态代码有什么区别？功能

Question

构造函数和静态代码有什么区别？

为什么Thread.setDefaultUncaughtExceptionHandler不能在构造函数中工作？

源代码 1：

class MyUncaughtExceptionHandler implements
        Thread.UncaughtExceptionHandler {
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        System.out.println("caught " + e.getMessage());
    }
}
public class CaughtExceptionThread extends Thread{

    static {
        Thread.setDefaultUncaughtExceptionHandler(new MyUncaughtExceptionHandler());
    }
}

源代码 2：

class MyUncaughtExceptionHandler implements
        Thread.UncaughtExceptionHandler {
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        System.out.println("caught " + e.getMessage());
    }
}
public class CaughtExceptionThread extends Thread{

    public CaughtExceptionThread() {
        Thread.setDefaultUncaughtExceptionHandler(new MyUncaughtExceptionHandler());
    }
}

测试代码：

public class DefaultExceptionHandler extends CaughtExceptionThread{

    public static void main(String[] args) {
        ExecutorService es =
                Executors.newCachedThreadPool();
        es.execute(new ExceptionThread());
        es.shutdown();
    }
}

为什么源代码 1 可以工作，而源代码 2 却不能？