runnable的线程抛出异常无法捕获

package com.itbuluoge.mythread;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

class MyThread implements Runnable
{
  public void run()
  {
    throw new RuntimeException();
  }
}
public class ExceptionThread{

  /**
   * @param args
   */
  public static void main(String[] args) {
    // TODO Auto-generated method stub
    try
    {
      ExecutorService exec=Executors.newCachedThreadPool();
      exec.execute(new MyThread());
    }
    catch(Exception e)
    {
      System.out.println("exception");
    }
    
  }

}