Hi,All!
When i develop a RMI server,i use
import java.rmi.server.UnicastRemoteServer;
import java.rmi.server.StubSecurityManager;

import chat.server.*;


but when i compile the java file,it occur an error,it said
Class java.rmi.server.UnicastRemoteServer not found in import.
import java.rmi.server.UnicastRemoteServer
and also error with StubSecurityManager
also it said

pls help me work out this problem
thanks a lot