[DP] 전략 패턴

전략 패턴(strategy pattern)

 

객체의 행위를 바꾸고 싶은 경우 직접 수정하지 않고 전략이라고 부르는 캡슐화한 알고리즘을 컨텍스트 안에서 바꿔주면서 상호 교체가 가능하게 만드는 패턴

 

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;

interface PaymentStrategy { 
    public void pay(int amount);
} 

class CardStrategy implements PaymentStrategy {
    private String name;
    private String cardNumber;
    private String cvv;
    private String dateOfExpiry;
    
    public CardStrategy(String nm, String ccNum, String cvv, String expiryDate){
        this.name=nm;
        this.cardNumber=ccNum;
        this.cvv=cvv;
        this.dateOfExpiry=expiryDate;
    }

    @Override
    public void pay(int amount) {
        System.out.println(amount +" paid Card");
    }
} 

class CashStrategy implements PaymentStrategy {
    private String emailId;
    private String password;
    
    public CashStrategy(String email, String pwd){
        this.emailId=email;
        this.password=pwd;
    }
    
    @Override
    public void pay(int amount) {
        System.out.println(amount + " paid Cash.");
    }
} 

class Item { 
    private String name;
    private int price; 
    public Item(String name, int cost){
        this.name=name;
        this.price=cost;
    }

    public String getName() {
        return name;
    }

    public int getPrice() {
        return price;
    }
} 

class ShoppingCart { 
    List<Item> items;
    
    public ShoppingCart(){
        this.items=new ArrayList<Item>();
    }
    
    public void addItem(Item item){
        this.items.add(item);
    }
    
    public void removeItem(Item item){
        this.items.remove(item);
    }
    
    public int calculateTotal(){
        int sum = 0;
        for(Item item : items){
            sum += item.getPrice();
        }
        return sum;
    }
    
    public void pay(PaymentStrategy paymentMethod){
        int amount = calculateTotal();
        paymentMethod.pay(amount);
    }
}  

public class Main{
    public static void main(String []args){
        ShoppingCart cart = new ShoppingCart();
        
        Item A = new Item("apple",100);
        Item B = new Item("banana",200);
        
        cart.addItem(A);
        cart.addItem(B);
        
        // pay by Cash
        cart.pay(new CashStrategy("test@google.com", "1234"));
        // pay by Card
        cart.pay(new CardStrategy("yujin", "123456789", "123", "23/01"));
    }
}