Question

您能帮我解决一下这段代码吗？

interface Speaker {

    void speak();

}
public class Politician implements Speaker {

    public void speak() {
        System.out.println("Politician speaking");
    }
}
public class Lecturer implements Speaker {

    public void speak() {
        System.out.println("Lecturer spaeking");
    }

}

public class SpeakerTest {

    public static void main(String[] args) {

         //??????????????? how to execute?


    }
}

Answer 1

public static void main(String[] args) {

Speaker s1,s2;
s1 = new Lecturer();
s2 = new Politician();

s1.speak(); // it print  'Lecturer spaeking'
s2.speak(); // it print  'Politician speaking'

}

Answer 2

Speaker s = new AnInstanceOfAClassThatImplementsSpeaker();//instead of //??????????????? how to execute?
s.speak(); // will call appropriate speak() method`

Answer 3

接口基本上是一个合约，其他类可以看到这些方法。与抽象类相反，内部没有任何功能（静态方法除外）。

接口方法的具体实现是在实现接口的类中完成的。所以类必须保持接口的方法契约。

因此，您在main方法中声明类型为Speaker的变量，并在此示例中指定类的实例（Politician或Lecturer）。

public class SpeakerTest {

    public static void main(String[] args) {
         // Speaker is the Interface. We know it has a speak() method and do not care about the implementation (i.e. if its a politicial or a lecturer speaking)
         Speaker firstSpeaker = new Politician();
         firstSpeaker.speak();
         Speaker secondSpeaker = new Lecturer();
         secondSpeaker.speak();

    }
}

简单的Java接口实现

3 个答案: