Computers & Technology►Software Engineering

用设计模式写 Hello World

看了许多遍设计模式，还是不能完全理解，不知道什么时候才能写出下面这种 Hello World，或者是看懂就行。

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public interface MessageStrategy {
    public void sendMessage();
}

public abstract class AbstractStrategyFactory {
    public abstract MessageStrategy createStrategy(MessageBody mb);
}

public class MessageBody {
    Object payload;
    public Object getPayload() {
        return payload;
    }
    public void configure(Object obj) {
        payload = obj;
    }
    public void send(MessageStrategy ms) {
        ms.sendMessage();
    }
}

public class DefaultFactory extends AbstractStrategyFactory {
    private DefaultFactory() {;}
    static DefaultFactory instance;
    public static AbstractStrategyFactory getInstance() {
        if (instance==null) instance = new DefaultFactory();
        return instance;
    }

    public MessageStrategy createStrategy(final MessageBody mb) {
        return new MessageStrategy() {
            MessageBody body = mb;
            public void sendMessage() {
                Object obj = body.getPayload();
                System.out.println((String)obj);
            }
        };
    }
}

public class HelloWorld {
    public static void main(String[] args) {
        MessageBody mb = new MessageBody();
        mb.configure("Hello World!");
        AbstractStrategyFactory asf = DefaultFactory.getInstance();
        MessageStrategy strategy = asf.createStrategy(mb);
        mb.send(strategy);
    }
}

参见 Jason Tiscione Re:Design Patterns

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