안녕하세요.

현재 자바 1-17 객체지향 퀴즈 강의를 듣고 있습니다.

코드를 작성하고 Main.java를 실행하는데 사진과 같은 에러가 발생하여 문의드립니다!

감사합니다.

전체 화면 캡처 및 에러 메세지

작성한 코드

(1) Main.java

public class Main {
    public static void main(String[] args) {
        Human child = new Child("나", 20);
        Human parent = new Parent("엄마", 50);
        Human grandParent = new GrandParent("할아버지", 70);

        Human[] humans = {grandParent, parent, child};// 배열에 담기
        for (Human human : humans) {//for-each문 적용
            System.out.println(human.name + ", 나이 : "+ child.age + ", 속도 : "+ child.speed + ", 현재 위치 : "+ human.getLocation());
        }
        System.out.println("<활동 시작>");
        for (Human human : humans) {//for-each문 적용
            if (human instanceof Walkable) {// human이 걸을 수 있는 친구의 인스턴스이면, 걸어갈거야
                ((Walkable) human).walk(1,1);//캐스팅, Walkable의 인스턴스 타입으로 인식됨
                System.out.println("- - - - - - - -");
            }
            if (human instanceof Runnable) {
                ((Runnable) human).run(2,2);
                System.out.println("- - - - - - - -");
            }
            if (human instanceof Swimmable) {
                ((Swimmable) human).swim(3, -1);
                System.out.println("- - - - - - - - ");
            }
        }
    }
}

(2) Human.java

public class Human {
    String name;
    int age;
    int speed;
    int x,y;

    public Human(String name, int age, int speed, int x, int y) {// 초기화할 수 있는 constructor 생성 alt+insert
        this.name = name;
        this.age = age;
        this.speed = speed;
        this.x = x;
        this.y = y;
    }

    public Human(String name, int age, int speed) {// 위치 기본값 0
        this(name, age, speed, 0,0);
    }

    public String getLocation() {// 위치 정보
        return "( " + x + ", " + y + ")";
    }

    protected void printWhoAmI() {
        System.out.println("My name is "+name+ "." + age + "aged.");
    }
}

(3) Walkable.java

public interface Walkable {
    void walk(int x, int y);
}

(4) Runnable.java

public interface Runnable {
    void run(int x, int y);
}

(5) Swimmable.java

public interface Swimmable {
    void swim(int x, int y);
}

(6) GrandParent.java

public class GrandParent extends Human implements Walkable{
    public GrandParent(String name, int age) {//조부모의 기본 속도 : 1 -> parameter로 받을 필요가 없다.
        super(name, age, 1);
    }

    @Override
    public void walk(int x, int y) {
        printWhoAmI();
        System.out.println("walk speed : " + speed);
        this.x = x;
        this.y = y;
        System.out.println("Walked to " + getLocation());
    }
}

(7) Parent.java

public class Parent extends Human implements Walkable, Runnable{
    public Parent(String name, int age) {//기본 속도 : 3 지정되어 있으므로
        super(name, age, 3);
    }

    @Override
    public void walk(int x, int y) {
        printWhoAmI();
        System.out.println("walk speed : " + speed);
        this.x = x;
        this.y = y;
        System.out.println("Walked to " + getLocation());
    }

    @Override
    public void run(int x, int y) {
        printWhoAmI();
        System.out.println("run speed : " + (speed+2));
        this.x = x;
        this.y = y;
        System.out.println("Ran to " + getLocation());
    }
}

(8) Child.java

public class Child extends Human implements Walkable, Runnable, Swimmable{
    public Child(String name, int age) {// 기본 속도 : 5
        super(name, age, 5);
    }

    @Override
    public void walk(int x, int y) {
        printWhoAmI();
        System.out.println("walk speed : " + speed);
        this.x = x;
        this.y = y;
        System.out.println("Walked to " + getLocation());
    }

    @Override
    public void run(int x, int y) {
        printWhoAmI();
        System.out.println("run speed : " + (speed+2));
        this.x = x;
        this.y = y;
        System.out.println("Ran to " + getLocation());
    }

    @Override
    public void swim(int x, int y) {
        printWhoAmI();
        System.out.println("swim speed : " + (speed+1));
        this.x = x;
        this.y = y;
        System.out.println("swum to " + getLocation());
    }

}