jokes

package test;

public class SO {

    public static void main(String[] args) {
        JokePrinter basic = new JokePrinter(new BasicJokeGenerator());
        basic.printJoke("testTopic");
        basic.printJoke("otherTopic");

        JokePrinter good = new JokePrinter(new GoodJokeGenerator());
        good.printJoke("testTopic");
        good.printJoke("otherTopic");
    }
}


class JokePrinter {
    private JokeGenerator jg;

    public JokePrinter(JokeGenerator jg) {
        this.jg = jg;
    }

    public void printJoke(String title) {
        System.out.println(jg.generateJoke(title));
    }
}

interface JokeGenerator {
    public String generateJoke(String topic);
}

class BasicJokeGenerator implements JokeGenerator {

    @Override
    public String generateJoke(String topic) {
        if(topic.equals("testTopic")) {
            //dont use == on strings!
            return "Some lame test joke";
        } else {
            return "Default lame joke";
        }
    }

}

class GoodJokeGenerator extends BasicJokeGenerator {

    @Override
    public String generateJoke(String title) {
        String joke = super.generateJoke(title);
        joke = joke.replace("lame", "good");
        return joke;
    }
}

/*
 * prints:
Some lame test joke
Default lame joke
Some good test joke
Default good joke
 */