Hello World revised, v2) public class HelloWorld Decoupled i public static void main(String[] args)t MessageRenderer mr new StandardoutMessageRenderer: MessageProvider mp new HelloWorldMessageProvidero mr. setMessageProvider(mp); mr render 还有一个小问题: 若想改变消息提供和显示 者还要改变代码HelloWorld (Revised, v2) public class HelloWorldDecoupled { public static void main(String[] args) { MessageRenderer mr = new StandardOutMessageRenderer; MessageProvider mp = new HelloWorldMessageProvider(); mr.setMessageProvider(mp); mr.render(); } } 还有一个小问题: 若想改变消息提供和显示 者还要改变代码