what make rmi server keep running?

I have the following RMI server code:

public class ServerProgram {
    public ServerProgram() {
        try {
            LocateRegistry.createRegistry(1097);
            Calculator c = new CalculatorImpl();
            String name = "rmi://host:port/name";
            Naming.rebind(name, c);
            System.out.println("Service is bound......");
        开发者_如何学JAVA} catch (Exception e) {
        }
    }
    public static void main(String[] args) {
        new ServerProgram();
    }
}

When the above program running, it keeps running to wait for client requests. But what I do not understand is what make that program keeps running while it is not in something like while(true){}; and how to stop it from listening, except stopping the whole program?

What makes it keep running is a non-daemon listening thread started by RMI. To make it exit, unbind the name and unexport both the Registry and the remote object, with UnicastRemoteObject.unexportObject().

To stop it, you should call

LocateRegistry.getRegistry().unbind("rmi://host:port/name");

But what I do not understand is what make that program keeps running while it is not in something like while(true){}; and how to stop it from listening, except stopping the whole program?

This is done by a edit non-editdaemon thread. See: What is Daemon thread in Java? You can test the behavior with this little example:

public class DaemonThread extends Thread
{
  public void run(){
    System.out.println("Entering run method");
    try
    {
      System.out.println(Thread.currentThread());
      while (true)
      {
        try {Thread.sleep(500);}
        catch (InterruptedException x) {}
        System.out.println("Woke up");
      }
    }
    finally { System.out.println("run finished");}
  }

  public static void main(String[] args) throws InterruptedException{
    System.out.println("Main");
    DaemonThread t = new DaemonThread();
    t.setDaemon(false);  // Set to true for testing
    t.start();
    Thread.sleep(2000);
    System.out.println("Finished");
  }
}

The setting prevents the JVM to shut down. after System.out.println("Finished"); you still see the thread running with it's "Woke up" log outputs.