GOF 디자인 패턴 (생성 패턴)

1.    Singleton 패턴

 

목적

n        어떤 객체가 단 하나만 생성되어 사용되어야 할 때 적용

 

 

public class A {        private static A instance;               private A() {}      // 생성자 제한        public static synchronized A getInstance() {              if(instance == null) {                     instance = new A();                     return instance;              }else                     return instance;                        }               public static void main(String [] args) {              A a1 = A.getInstance();              A a2 = A.getInstance();                           if(a1 == a2) {                     System.out.println("두 객체는 동일합니다.");              }        } }

 

 

2.    Factory Method 패턴

 

목적

n         객체를 생성하기 위한 인터페이스를 정의

n         서브클래스가 어느 클래스를 인스턴스화 할지를 결정

 

 

public abstract class Connection {        protected String url;               public Connection(String url) {              this.url = url;        }        abstract public void connect(); }   class TCPConnection extends Connection {        public TCPConnection(String url) {              super(url);        }        public void connect() {              System.out.println(url + " 로 TCP 연결을 시도합니다.");        } }   class UDPConnection extends Connection {        public UDPConnection(String url) {              super(url);        }               public void connect() {              System.out.println(url + " UDP 연결을 시도합니다.");        } }   class HTTPConnection extends Connection {        public HTTPConnection(String url) {              super(url);        }               public void connect() {              System.out.println(url + " HTTP 연결을 시도합니다.");        } }

 

abstract class ConnectionFactory {        abstract public Connection getConnection(String str); }   class TCPConnectionFactory extends ConnectionFactory {        public Connection getConnection(String url) {              return new TCPConnection(url);        } }   class UDPConnectionFactory extends ConnectionFactory {        public Connection getConnection(String url) {              return new UDPConnection(url);        } }   class HTTPConnectionFactory extends ConnectionFactory {        public Connection getConnection(String url) {              return new HTTPConnection(url);        } }

 

public class Client {        public static void main(String[] args) {              ConnectionFactory factory = new TCPConnectionFactory();              Connection socket = factory.getConnection("SOCKET://70.12.113.168:5555");              socket.connect();                           ConnectionFactory factory1 = new UDPConnectionFactory();              Connection datagram = factory1.getConnection("DATAGRAM://70.12.113.168:5555");              datagram.connect();                           ConnectionFactory factory2 = new HTTPConnectionFactory();              Connection http = factory1.getConnection("HTTP://70.12.113.168:5555");              http.connect();        } }

 

3.    Abstract Factory 패턴

 

목적

n         구체 클래스를 명시하지 않고 관련된 혹은 의존적인 객체의 집합을 생성하기 위한 인터페이스를 제공

n         단순하게 객체 하나를 생성하는 경우보다는 여러 개의 객체를 생성해야 하는 경우에 유용

 

 

abstract class Head {        abstract public void display(); }   class CircleHead extends Head {        public void display() {              System.out.println("둥근 타입의 머리를 가졌습니다.");        } }   abstract class Leg {        abstract public void display(); }   class WheelLeg extends Leg {        public void display() {              System.out.println("바퀴 타입의 다리를 가졌습니다.");        } }   abstract class Body {        abstract public void display(); }   class LCDBody extends Body {        public void display() {              System.out.println("몸통에는 LCD 화면을 가지고 있습니다.");        } }   abstract class Arm {        abstract public void display(); }   class FingerArm extends Arm {        public void display() {              System.out.println("손가락 팔을 가지고 있습니다.");        } }

 

class Robot {        private Head head;        private Body body;        private Leg leg;        private Arm arm;               public void addHead(Head head) {              this.head = head;        }        public void addBody(Body body) {              this.body = body;        }        public void addLeg(Leg leg) {              this.leg = leg;        }        public void addArm(Arm arm) {              this.arm = arm;        }        public void displayRobot() {              System.out.println("완성된 로봇은 다음과 같은 기능을 가지고 있습니다.");              head.display();              body.display();              leg.display();              arm.display();        } }

 

abstract class RobotFactory {        abstract public Head createHead();        abstract public Body createBody();        abstract public Leg createLeg();        abstract public Arm createArm(); }   class HomeRobotFactory extends RobotFactory {        public Head createHead() {              return new CircleHead();        }        public Body createBody() {              return new LCDBody();        }        public Leg createLeg() {              return new WheelLeg();        }        public Arm createArm() {              return new FingerArm();        } }

 

public class Client {        public static void main(String[] args) {              Robot homeRobot = new Robot();              RobotFactory homeFactory = new HomeRobotFactory();              homeRobot.addHead(homeFactory.createHead());              homeRobot.addBody(homeFactory.createBody());              homeRobot.addLeg(homeFactory.createLeg());              homeRobot.addArm(homeFactory.createArm());                           homeRobot.displayRobot();        } }

 

 

4.    Builder 패턴

 

목적

n         Product에 대한 다양한 추가 작업으로 인한 결과값의 변형에 유용

n         하나의 Product를 완성하기 위해서 복잡한 작업을 거쳐야 할 경우에도 유용

 

 

 

import java.io.*;   abstract class Builder {        StringBuffer result = new StringBuffer();               public boolean makeFile(String filename) {              try {                     FileOutputStream fout = new FileOutputStream(filename);                     DataOutputStream dout = new DataOutputStream(fout);                                         dout.writeUTF(result.toString());                     return true;              }              catch (Exception e) {                     return false;              }        }        public abstract String getResult();        public abstract void makeTitle(String title);        public abstract void makeAuthor(String author);        public abstract void makeDate(String date);        public abstract void makeSubTitle(String subTitle);        public abstract void makeContext(String context[]); }

 

class HTMLBuilder extends Builder {        public String getResult() {              result.append("</body></html>");              return result.toString();        }        public void makeTitle(String title) {              result.append("<html><<head>");              result.append("<title>" + title + "</title>");              result.append("</head>");              result.append("<body>");              result.append("TITLE : " + title + "<br>");        }        public void makeAuthor(String author) {              result.append("AUTHOR : " + author + "<br>");        }        public void makeDate(String date) {              result.append("DATE : " + date + "<br><hr>");        }        public void makeSubTitle(String subTitle) {              result.append(subTitle + "<br>");        }        public void makeContext(String context[]) {              result.append("<ul>");              for(int i=0; i<context.length; i++) {                     result.append("<li>" + context[i] + "</li>");              }              result.append("</ul>");        } }

 

class Director {        private Builder builder;        private String filename;               public Director(Builder builder, String filename) {              this.builder = builder;              this.filename = filename;        }        public String construct() {              builder.makeTitle("Member List");              builder.makeAuthor("kkang");              builder.makeDate("2005.12.25");              builder.makeSubTitle("A++");              builder.makeContext(new String[]{"홍길동", "김길동", "강길동"});              builder.makeSubTitle("B++");              builder.makeContext(new String[]{"박길동", "원길동", "정길동"});              return builder.getResult();        }               public boolean makeFile() {              return builder.makeFile(filename);        } }

 

public class Client {        public static void main(String[] args) {              Director director = new Director(new HTMLBuilder(), "member.html");                           System.out.println(director.construct());              director.makeFile();        } }

 

5.    Prototype 패턴

 

목적

n         새로운 객체를 생성할 때 new 연산자를 사용하지 않고 기존의 객체를 복사하여 이용하는 패턴

 

 

class Product implements Cloneable {        private String name;        private int price;               public Product(String name, int price) {              this.name = name;              this.price = price;        }        public Product cloneMe() throws CloneNotSupportedException {              return (Product) clone();        }               public String getName() {              return name;        }        public void setName(String name) {              this.name = name;        }        public int getPrice() {              return price;        }        public void setPrice(int price) {              this.price = price;        } }

 

class Manager {        private Product product = null;               public Product getProduct() {              if(product == null) {                     product = new Product("design pattern", 10000);                     return product;              }              else {                     try {                            product = product.cloneMe();                            return product;                     } catch (Exception e) {                            return null;                     }              }        } }

 

public class Client {        public static void main(String[] args) {              Manager manager = new Manager();                           Product product = manager.getProduct();              System.out.println("name:" + product.getName());              System.out.println("price:" + product.getPrice());              System.out.println();                           Product product1 = manager.getProduct();              System.out.println("name:" + product1.getName());              System.out.println("price:" + product1.getPrice());              System.out.println();                           product1.setName("java programming");              product1.setPrice(5000);                           Product product2 = manager.getProduct();              System.out.println("name:" + product2.getName());              System.out.println("price:" + product2.getPrice());              System.out.println();        } }

 

참고

1.      삼성 SDS 멀티캠퍼스 교육 과정 – “자바 개발자를 위한 디자인 패턴” (수강 추천)

      2.   StarUML 패턴 관련 도움말.