下面代码使用了哪种设计模式（）
ChatRoom.java
import java.util.Date;
public class ChatRoom {
public static void showMessage(User user, String message){
System.out.println(new Date().toString()
+ " [" + user.getName() +"] : " + message);
}
}
User.java
public class User {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public User(String name){
this.name = name;
}
public void sendMessage(String message){
ChatRoom.showMessage(this,message);
}
}
Demo.java
public class Demo {
public static void main(String[] args) {
User robert = new User("Robert");
User john = new User("John");
robert.sendMessage("Hi! John!");
john.sendMessage("Hello! Robert!");
}
}
