생성자, Getter, Setter, 추상클래스, 인터페이스

생성자 & Getter Setter

자바(Java) 기초 강의 #10 생성자 & Getter Setter - 쉽게 자바 코딩하는 방법 (현직 개발자 설명) , Java / android / Java tutorial
출처:youtube hongdroid홍드로이드

생성자

Alt + insert Constructor

public class Main {
//    public Main () {}
// default 생성자
    public static void main(String[] args) {
    }
}

인스턴스 적용

public class User {
    public static void main(String[] args) {
        Main main = new Main("홍승엽", 27,"프로그래밍");
    }
}

Getter Setter

Alt + insert Getter and Setter

public String getName() {
        return name;
    }
    // Getter
    public void setName(String name) {
        this.name = name;
    }
    // Setter 

public class Main {
    String name;    // 이름
    public Main() {} // default 생성자
}
public static void main(String[] args) {
        Main main = new Main(); // default 생성자 필요
        main.setName("홍승엽");
        System.out.println(main.getName());
        System.out.println(main.name());
}

접근제어자가 private인 경우 Getter와 Setter를 활용하여 접근

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&, |: 비트연산자의 경우 뒤쪽까지 모두 실행

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추상클래스

abstract class Bird { // 추상클래스
    private int x, y, z;
    void fly(int x, int y, int z) {
        printlocation();
        System.out.println("이동합니다.");
        this.x = x;
        this.y = y;
        if(flyable(z)) {
            this.z = z;
        } else {
            System.out.println("그 높이로는 날 수 없습니다.");
        }
        printlocation();
    }
    abstract boolean flyable(int z);
    public void printlocation() {
        System.out.println("현재위치 (" + x + ", " + y + ", " + z + ")");
    }
}
class Pigeon extends Bird { // 각 클래스에서 flyable z 포함
    @Override
    boolean flyable(int z) {
        return z < 10000;
    }
}
class Peacock extends Bird {
    @Override
    boolean flyable(int z) {
        return false;
    }
}
public class Main {
    public static void main(String[] args) {
        Bird pigeon = new Pigeon();
        Bird Peacock = new Peacock();
        System.out.println("---비둘기---");
        pigeon.fly(1,2,3);
        System.out.println("---공작새---");
        Peacock.fly(1,2,3);
        System.out.println("---비둘기---");
        pigeon.fly(2,2,10002);
    }
}

인터페이스
접근제어자, 리턴타입, 메소드 이름만을 정의
함수의 내용은 없음
인터페이스를 구성하는 class는 함수의 내용({} 중괄호 안의 내용)을 반드시 구현해야한다.

 interface Flyable {
    void fly(int x, int y, int z);
 }
 class Pigeon implements Flyable { // 내용 구현
    private int x, y, z;
    @Override
    public void fly(int x, int y, int z) {
        printLocation();
        System.out.println("날아갑니다.");
        this.x = x;
        this.y = y;
        this.z = z;
        printLocation();
    }
    public void printLocation() {
        System.out.println("현재 위치 (" + x + ", " + ", " + z + ")");
    }
 }
 public class Main {
     public static void main(String[] args) {
         Flyable pigeon = new Pigeon();
         pigeon.fly(1,2,3,);
     }
 }

• 인터페이스

1. 구현하려는 객체의 동작의 명세
2. 다중 상속 가능
3. implements를 이용하여 구현
4. 메소드 시그니처(이름, 파라미터, 리턴 타입)에 대한 선언만 가능

• 추상클래스

1. 클래스를 상속받아 이용 및 확장을 위함
2. 다중 상속 불가능 , 단일 상속
3. extends를 이용하여 구현
4. 추상메소드에 대한 구현 가능

class Family {
String name;
int age;
int speed;
int x;
int y;
String way;

1-17 객체지향 퀴즈(내가 한 답)

public Family(String name, int age) {
        this.name = name;
        this.age = age;
        this.x = x;
        this.y = y;
        if(name=="Grand") {
            this.speed=1;
        }
        else if(name=="Parents") {
            this.speed=3;
        }
        else {
            this.speed=5;
        }
        System.out.println("Name: " + name + ", Age: " + age + ", Speed: " + speed + ", Initial Location: " + x + ", " + y);
        if(name=="Grand") {
            this.x = 1;
            this.y = 1;
            way = "walking";
        }
        else if(name=="Parents") {
            this.x = 2;
            this.y = 2;
            this.speed+=2;
            way = "running";
        }
        else {
            this.x = 3;
            this.y = -1;
            this.speed+=1;
            way = "swimming";
        }
    }
    public void printLocation() {
        System.out.println("Speed: " + speed + ", Location: " + x + ", " + y + ", by " + way);
    }
}
public class Main {
    public static void main(String[] args) {
        Family grand = new Family("Grand",70);
        grand.printLocation();
        Family parents = new Family("Parents",35);
        parents.printLocation();
        Family child = new Family("Childre",10);
        child.printLocation();
    }
}

interface (답)

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) {
        this.name = name;
        this.age = age;
        this.speed = speed;
        this.x = x;
        this.y = y;
    }
    public Human(String name, int age, int speed) {
        this(name, age, speed, 0,0);
    }
    public String getLocation() {
        return "(" + x + ", " + y + ")";
    }
    protected void printWhoAmI() {
        System.out.println("My name is " + name + ". " + age + " aged.");
    }
}

Walkable.java

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

Runnable.java

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

Swimmable.java

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

GrandParent.java

public class GrandParent extends Human implements Walkable {
    public GrandParent(String name, int age) {
        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());
    }
}

Parent.java

public class Parent extends Human implements Walkable, Runnable{
    public Parent(String name, int age) {
        super(name, age, 3);
    }
    @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 walk(int x, int y) {
        printWhoAmI();
        System.out.println("walk speed: " + speed);
        this.x = x;
        this.y = y;
        System.out.println("Walked to " + getLocation());
    }
}

Child.java

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

Main.java

public class Main {
    public static void main(String[] args) {
        Human grandParent = new GrandParent("할아버지",70);
        Human parent = new Parent("어머니",45);
        Human child = new Child("아들", 15);
        Human[] humans = {grandParent, parent, child};
        for(Human human : humans) {
            System.out.println(human.name + ", 나이: " + human.age + ", 속도: " + human.speed + "현재위치" + human.getLocation());
        }
        System.out.println("<활동시작>");
        for(Human human : humans) {
            if(human instanceof Walkable) {
                ((Walkable) human).walk(1,1);
                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("- - - - - -");
            }
        }
    }
}

어렵다....