[nhn next] java 강의- week3

PL�� in�� Java�� Week03��

I n h e r i t a n c e

조영호�� snatcher@nhn.com��

상속

Conceptual Perspective��

Implementation Perspective��

객체지향�� Object-Orientation��

개념�� 관점��

구현�� 관점��

Type��

Class��

Generalization��

Inheritance��

To p i c s ��

Inheritance

Generalization

Composition

Method Overriding

super()

사람��

요츠바�� 5살��

class Person { String name; int age; Person() { this("사람", 1); } Person(String name, int age) { this.name = name; this.age= age; } String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; }}

Person��

Person yotsuba = new Person("요츠바", 5);System.out.println(yotsuba.introduce());

Person yotsuba = new Person("요츠바", 5);

name = 요츠바 age = 5��

Person

new Person()��

킬러��

class Killer { String name; int age; String warning; String weapon; Killer(String name, int age, String warning, String weapon) { this.name = name; this.age = age; this.warning = warning; this.weapon = weapon ; } String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; } String getWeapon() { return weapon; }}

Killer��

Killer killerYotsuba = new Killer("요츠바", 5, "You can tell me in hell.", "총");System.out.println(killerYotsuba.introduce());System.out.println(killerYotsuba.getWeapon());

Killer killerYotsuba = new Killer("요츠바", 5, "You can tell me in hell.", "총");

name = 요츠바 age = 5 warning = You.. weapon = 총 ��

Killer

new Killer()��

Person & Killer��

Person�� name age��

introduce()��

Killer�� name age warning weapon��

introduce() getWeapon()��

Code Duplication��

introduce()��

Killer�� name age warning weapon��

introduce() getWeapon()��

Inheritance��

introduce()��

Killer�� warning weapon��

getWeapon()��

class Killer extends Person { String warning; String weapon; Killer(String name, int age, String warning, String weapon) { this.name = name; this.age = age; this.warning = warning; this.weapon = weapon; } String getWeapon() { return weapon; } }

Killer extends Person��

Person

Killer

Member Variable Inheritance��

Person yotsuba = new Person("요츠바", 5);System.out.println(yotsuba.introduce());Killer killerYotsuba = new Killer("요츠바", 5, "You can tell me in hell.", "총");System.out.println(killerYotsuba.introduce());System.out.println(killerYotsuba.getWeapon());

Method Inheritacne��

음악가��

Person Code Reuse��

Inheritance��

introduce()��

Musican�� instrument

play()��

public class Musician extends Person { String instrument; Musician(String name, int age, String instrument) { this.name = name; this.age = age; this.instrument = instrument; } String play() { return instrument + " 연주"; }}

Musician extends Person��

Musician musicanYotsuba = new Musician("요츠바", 5, "피리");System.out.println(musicanYotsuba.introduce());System.out.println(musicanYotsuba.play());

Code Reuse��

Inheritance��

Remove Code Duplication��

Root Class��

Object��

class Person {}

Object��

class Person extends Object {}

To p i c s ��

Inheritance

Generalization

Composition

Method Overriding

super()

사람과�� 킬러��

사람과�� 킬러�� 더�� 일반적인�� 개념��

사람과�� 킬러�� 더�� 특수한�� 개념��

왜?��

왜?�� 의미적으로�� 킬러를�� 포괄하면서

더�� 적은�� 설명�� 필요��

사람의�� 개념을�� 포함하는 더�� 많은�� 설명�� 필요��

왜?��

이�� 세상에는�� 사람이�� 더�� 많을까요?�� 킬러가�� 더�� 많을까요?��

사람��

사람�� 킬러��

사람�� 킬러�� 더�� 일반적인�� 개념��

더�� 특수한�� 개념��

일반화와�� 특수화�� 일반화�� 특수화��

설명은�� 더�� 추상적이고 집합의�� 크기는�� 더�� 크고��

설명은�� 더�� 구체적이고 집합의�� 크기는�� 더�� 작고��

특수화�� 집합은�� 일반화�� 집합의�� 부분집합��

is-a Relationship��

Killer is-a Person��

in OO��

Concept == Type��

사람�� 킬러�� Type

in OO��

Type Class�� implementation

사람�� 킬러�� Class

class Person { String name; int age; String introduce() { } }

class Killer extends Person { String warning; String weapon; String getWeapon() { } }

더�� 추상적인�� 설명��

더�� 구체적인�� 설명��

Killer

Person

Killer

Person

Person yotsuba = new Killer("요츠바", 5, "You can tell me in hell.", "총");

Person�� Killer�� Class

new Killer()��

new Person()��

class Person { String name; int age; String introduce() { } }

class Killer extends Person { String warning; String weapon; String getWeapon() { } }

일반화��

특수화��

in OO��

Type Type��

Generalization Specialization

in OO��

Class Class�� Inheritance

in OO��

Generalization Inheritance��

implementation

To p i c s ��

Inheritance

Generalization

Composition

Method Overriding

super()

Method Overloading?��

Method Overloading�� public class Elevator { Elevator() { ... } Elevator(int floor) { ... } void moveUp() { ... } void moveUp(int floor) { ... } void moveDown() { ... } void moveDown(int floor) { ... }}

Method Overriding?��

class Person { String name; int age; ... String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; }}

this class Person String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; }

class Object

superclass

String toString() { ... }

Method Lookup

this에서�� 시작��

class Person { String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; }}

class Object

superclass

yotsuba.introduce()

class Person { String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; } }

class Object

superclass

yotsuba.toString()

class Killer extends Person { }

Person yotsuba = new Killer("요츠바", 5, "You can tell me in hell.", "총");

name = 요츠바 age = 5 warning = You.. weapon = 총

��

class Person String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; }

class Object

superclass

class Killer

superclass

��

class Object

superclass

class Killer

superclass

yotsuba.introduce()

class Killer extends Person { }

class Person { String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; } }

��

class Object

superclass

class Killer

superclass

yotsuba.introduce()

String introduce() { return ＂무기 : " + weapon + "," + "이름 : " + name + ", 나이 " + age + "세"; }

class Killer extends Person { String introduce() { return ＂무기 : " + weapon + "," + "이름 : " + name + ", 나이 " + age + "세"; } }

class Object

Killer의�� introduce()가��

Person의�� introduce()를��

감춤��

Method Overriding?��

To p i c s ��

Inheritance

Generalization

Composition

Method Overriding

super()

Method Lookup

this에서�� 시작��

메시지를�� 수신한�� 현재�� 객체��

현재�� 클래스��

public class Person { String message() { return "Message : [" + introduce() + "]"; }

String introduce() { return "이름: " + name + ", 나이: " + age + "세"; }}

public class Killer extends Person { String introduce() { return ＂무기 : " + weapon + "," + "이름 : " + name + ", 나이 " + age + "세"; }}

Person killerYotsuba = new Killer("요츠바", 5, "You can tell me in hell.", "총");killerYotsuba.message();

��

class Person String message() { return "Message : [" + introduce() + "]"; }

String introduce() { return "이름 : " + name + ", 나이 " + age + "세"; }

class Object

superclass

class Killer

superclass

Person killerYotsuba = new Killer("요츠바", 5, "You can tell me in hell.", "총");

killerYotsuba.message(); class Object

this부터�� Look�� Up��

��

class Object

superclass

class Killer

superclass

class Object

introduce()

��

class Object

superclass

class Killer

superclass

class Object

introduce()

��

class Object

superclass

class Killer

superclass

class Object

introduce()

this Dynamic��

Method Lookup

부모�� 클래스에서�� 시작��

public class Person { String introduce() { return "이름: " + name + ", 나이: " + age + "세"; } }

public class Killer extends Person { String introduce() { return ＂무기 : " + weapon + "," + "이름 : " + name + ", 나이 " + age + "세"; }}

Code Duplication

public class Killer extends Person { String introduce() { return ＂무기 : " + weapon + "," + introduce(); }} Recursive Call

Code Reuse

public class Killer extends Person { String introduce() { return ＂무기 : " + weapon + "," + super.introduce(); }}

super가�� 있는�� 클래스의�� 부모�� 클래스��

현재�� 객체��

super Static��

To p i c s ��

Inheritance

Generalization

Composition

Method Overriding

super()

this()

this()�� class Person { Person() { this("사람", 1); } Person(String name, int age) { this.name = name; this.age= age; }}

class Killer extends Person { Killer(String name, int age, String warning, String weapon) { this.name = name; this.age = age; this.warning = warning; this.weapon = weapon; }}

class Person { Person() { this("사람", 1); } Person(String name, int age) { this.name = name; this.age= age; }}

Code Duplication

super()

class Killer extends Person { Killer(String name, int age, String warning, String weapon) { super(name, age); this.warning = warning; this.weapon = weapon; }}

class Person { Person() { this("사람", 1); } Person(String name, int age) { this.name = name; this.age= age; }}

Code Duplication

To p i c s ��

Inheritance

Generalization

Composition

Method Overriding

super()

아이언맨��

class IronMan extends Person { }

?��

사람�� 킬러��

아이언맨��

?��

IronMan�� Person��

Composition��

Not Generalization��

class IronMan { Person person; IronMan(Person person) { this.person = person; } }

합성Composition��

IronMan ironMan = new IronMan(new Person("토니 스타크", 40)); IronMan ironYotsuba = new IronMan(new Killer("요츠바", 5, "You can tell me in hell.", "총"));

사람�� 킬러�� 아이언맨��

포함��

아이언맨이�� 말을�� 하는�� 것이�� 아니라��

안에�� 들어�� 있는�� 사람이�� 말을�� 하는�� 것이죠��

public class IronMan { Person person; IronMan(Person person) { this.person = person; } String introduce() { return person.introduce(); } }

위임Delegation��

has-a Relationship��

IronMan has-a Person��

Code Reuse��

Inheritance��

Composition��

White-Box Reuse��

Black-Box Reuse��

Favor composition over inheritance

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