[JAVA] 점프 투 자바 #19 다형성

[JAVA - 점프 투 자바 #19]

다형성

interface Predator {
    String getFood();

    default void printFood() {
        System.out.printf("my food is %s\n", getFood());
    }
}

class Animal {
    String name;

    void setName(String name) {
        this.name = name;
    }
}

class Tiger extends Animal implements Predator {
    public String getFood() {
        return "apple";
    }
}

class Lion extends Animal implements Predator {
    public String getFood() {
        return "banana";
    }
}

class ZooKeeper {
    void feed(Predator predator) {
        System.out.println("feed "+predator.getFood());
    }
}
class Bouncer {
    void barkAnimal(Animal animal) {
      if (animal instanceof Tiger) {
            System.out.println("어흥");
        } else if (animal instanceof Lion) {
            System.out.println("으르렁");
        } else if (animal instanceof Crocodile) {
          System.out.println("쩝쩝");
        } else if (animal instanceof Leopard) {
          System.out.println("캬옹");
        }
    }
}

public class Sample {
    public static void main(String[] args) {
        Tiger tiger = new Tiger();
        Lion lion = new Lion();

        Bouncer bouncer= new Bouncer();
        bouncer.barkAnimal(tiger);
        bouncer.barkAnimal(lion);
    }
}

instanceof는 어떤 객체가 특정 클래스의 객체인지를 조사할 때 사용되는 자바의 내장 명령어이다. 여기서 animal instanceof Tiger는 ‘animal 객체는 Tiger 클래스로 만들어진 객체인가?’를 묻는 조건문이고, 조건이 참이라면 ‘어흥’을 출력하게 되는 것이다.

인터페이스 사용

interface Predator {
    String getFood();

    default void printFood() {
        System.out.printf("my food is %s\n", getFood());
    }
}

interface Barkable {
    void bark();
}

interface BarkablePredator extends Predator, Barkable {
}

class Animal {
    String name;

    void setName(String name) {
        this.name = name;
    }
}

class Tiger extends Animal implements Predator, Barkable {
    public String getFood() {
        return "apple";
    }

    public void bark() {
        System.out.println("어흥");
    }
}

class Lion extends Animal implements BarkablePredator {
    public String getFood() {
        return "banana";
    }

    public void bark() {
        System.out.println("으르렁");
    }
}

class ZooKeeper {
    void feed(Predator predator) {
        System.out.println("feed " + predator.getFood());
    }
}

class Bouncer {
    void barkAnimal(Barkable animal) {
        animal.bark();
    }
}

public class Sample {
    public static void main(String[] args) {
        Tiger tiger = new Tiger();
        Lion lion = new Lion();

        Bouncer bouncer = new Bouncer();
        bouncer.barkAnimal(tiger);
        bouncer.barkAnimal(lion);
    }
}