[Zero-base] 11-9. 스트러티지(Strategy)

행동 패턴 - Strategy

 

해결하려는 문제

• 클라이언트에 독립적으로 문제 해결 전략을 바꾸고 싶을 때
• 다양한 문제해결 방법을 제공해야 할 때

 

 

public class Main {

    private static CouponService couponService = new CouponService();

    public static void main(String[] args) {
        /*
        Coupon discountCoupon = new DiscountCoupon(2000);
        System.out.println(discountCoupon.calc(3000));
        
        Coupon percentageCoupon = new PercentageCoupon(10);
        System.out.println(percentageCoupon.calc(3000));
        */
        
//      int productPrice = 1000;
        
        Product ipadPro = new Product("아이패드 프로", 1500000);
        
        Coupon percentageCoupon = couponService.getCoupon(10L);
        
        int discountAmount = ipadPro.discount(percentageCoupon);
        System.out.println("최종가격 : " + discountAmount);
        
//      Coupon discountCoupon = couponService.getCoupon(500L);
//      System.out.println(discountCoupon.calc(productPrice));
        
    }
}

public interface Coupon {
    int calc(int productAmount);
}

public class DiscountCoupon implements Coupon {
    private int discount;
    
    public DiscountCoupon(int discount) {
        this.discount = discount;
    }
    
    @Override
    public int calc(int productAmount) {
        return Math.max(productAmount - discount, 0);
    }
}

public class PercentageCoupon implements Coupon {
    private int ratio;
    
    public PercentageCoupon(int ratio) {
        this.ratio = ratio;
    }
    
    @Override
    public int calc(int productAmount) {
        int discountAmount = (int)(productAmount * (double)ratio / 100);
        return Math.max(productAmount - discountAmount, 0);
    }
}

public class CouponService {

    private CouponRepository couponRepository = new MockCouponRepository();

    public Coupon getCoupon(long couponId) {
        return couponRepository.findById(couponId)
                .orElseThrow(RuntimeException::new);
    }
}

import java.util.Optional;

public interface CouponRepository {
    Optional<Coupon> findById(Long id);
}

import java.util.Optional;

public class MockCouponRepository implements CouponRepository {
    @Override
    public Optional<Coupon> findById(Long id) {
    
        if (id <= 0)
            return Optional.empty();
        
        if (id < 100)
            return Optional.of(new PercentageCoupon(10));
            
        return Optional.of(new DiscountCoupon(2000));
    }
}

public class Product {
    private String name;
    private int price;
    public Product(String name, int price) {
        this.name = name;
        this.price = price;
    }
    
    public int discount(Coupon percentageCoupon) {
        return percentageCoupon.calc(price);
    }
}

 

 

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