我对Java和RMI系统非常陌生。我正在关注一个教程，但不确定为什么会不断出现以下错误[1] [1]：https://i.stack.imgur.com/xeYTn.png 我已经附加了代码（直接从此处的教程https://docs.oracle.com/javase/1.5.0/docs/guide/rmi/hello/hello-world.html中获取）

我尝试过：

• 使用“ package”删除所有行
• 更改类路径变量
• 重新安装Java和Javac
• 在“ rmiregistry＆”命令中设置类路径

任何帮助将不胜感激

edit：糟糕，忘记附加代码。 Hello.java

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface Hello extends Remote {
    String sayHello() throws RemoteException;
}

Client.java

import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class Client {

    private Client() {
    }

    public static void main(String[] args) {

        String host = (args.length < 1) ? null : args[0];
        try {
            Registry registry = LocateRegistry.getRegistry(host);
            Hello stub = (Hello) registry.lookup("Hello");
            String response = stub.sayHello();
            System.out.println("response: " + response);
        } catch (Exception e) {
            System.err.println("Client exception: " + e.toString());
            e.printStackTrace();
        }
    }
}

Server.java

import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;

public class Server implements Hello {

    public Server() {
    }

    public String sayHello() {
        return "Hello,world!";
    }

    public static void main(String args[]) {

        try {
            Server obj = new Server();
            Hello stub = (Hello) UnicastRemoteObject.exportObject((Remote) obj,0);

            // Bind the remote object's stub in the registry
            Registry registry = LocateRegistry.getRegistry();
            registry.bind("Hello",stub);

            System.err.println("Server ready");
        } catch (Exception e) {
            System.err.println("Server exception: " + e.toString());
            e.printStackTrace();
        }
    }
}