ExecutorService会阻止它所处的方法吗？(Will ExecutorService block the method it lies in?)

 我是Java的新手，我知道我的问题可能很愚蠢...我发现如果我不调用ExecutorService.shutdown（），我的主方法将被ExecutorService阻止返回： 
 
class Test{
    public static void main(String[] args){
        ExecutorService exec = new Executors.newCachedThreadPool();
        exec.execute(new Runnable(){
            public void run(){
                System.out.println("I am running!");
            }
        });
    }
}
 
 上面的代码不会在主线程中返回。 我想知道为什么ExecutorService会阻止main方法，它的目的是强制程序员调用shutdown（）吗？ 

I am a newbie in Java and I know my question may be silly... I found that my main method is prevented from returning by the ExecutorService if I do not invoke ExecutorService.shutdown():
 
class Test{
    public static void main(String[] args){
        ExecutorService exec = new Executors.newCachedThreadPool();
        exec.execute(new Runnable(){
            public void run(){
                System.out.println("I am running!");
            }
        });
    }
}
 
The code above will not return in the main thread. I wonder why the ExecutorService keeps blocking the main method, does it aim at forcing the programmer to invoke shutdown()?

原文：https://stackoverflow.com/questions/45418969