java代码如何用设计模式优化架构 java代码设计模式的应用教程​

// 策略接口
interface DiscountStrategy {
    double applyDiscount(double price);
}

// 具体策略：打折
class PercentageDiscount implements DiscountStrategy {
    private double discountPercentage;

    public PercentageDiscount(double discountPercentage) {
        this.discountPercentage = discountPercentage;
    }

    @Override
    public double applyDiscount(double price) {
        return price * (1 - discountPercentage);
    }
}

// 具体策略：满减
class FixedAmountDiscount implements DiscountStrategy {
    private double discountAmount;

    public FixedAmountDiscount(double discountAmount) {
        this.discountAmount = discountAmount;
    }

    @Override
    public double applyDiscount(double price) {
        return Math.max(0, price - discountAmount);
    }
}

// 上下文
class ShoppingCart {
    private DiscountStrategy discountStrategy;

    public void setDiscountStrategy(DiscountStrategy discountStrategy) {
        this.discountStrategy = discountStrategy;
    }

    public double calculatePrice(double price) {
        if (discountStrategy != null) {
            return discountStrategy.applyDiscount(price);
        }
        return price;
    }
}

// 使用示例
public class Main {
    public static void main(String[] args) {
        ShoppingCart cart = new ShoppingCart();
        cart.setDiscountStrategy(new PercentageDiscount(0.1)); // 打9折
        double discountedPrice = cart.calculatePrice(100);
        System.out.println("Discounted price: " + discountedPrice);

        cart.setDiscountStrategy(new FixedAmountDiscount(20)); // 满减20
        discountedPrice = cart.calculatePrice(100);
        System.out.println("Discounted price: " + discountedPrice);
    }
}