yilai/FixedAmountDiscountStrategy.java

/**
 * 固定金额折扣策略，提供固定金额的折扣
 */
package com.orderprocessing;

public class FixedAmountDiscountStrategy implements DiscountStrategy {
    private double discountAmount;
    private double minimumOrderAmount;
    
    /**
     * 构造方法
     * @param discountAmount 固定折扣金额
     * @param minimumOrderAmount 应用折扣的最小订单金额
     */
    public FixedAmountDiscountStrategy(double discountAmount, double minimumOrderAmount) {
        if (discountAmount < 0) {
            throw new IllegalArgumentException("折扣金额不能为负数");
        }
        if (minimumOrderAmount < 0) {
            throw new IllegalArgumentException("最小订单金额不能为负数");
        }
        this.discountAmount = discountAmount;
        this.minimumOrderAmount = minimumOrderAmount;
    }
    
    @Override
    public double calculateDiscount(Order order) {
        if (order == null || order.getTotalAmount() < minimumOrderAmount) {
            return 0;
        }
        // 确保折扣金额不超过订单总金额
        return Math.min(discountAmount, order.getTotalAmount());
    }
    
    public double getDiscountAmount() {
        return discountAmount;
    }
    
    public void setDiscountAmount(double discountAmount) {
        if (discountAmount < 0) {
            throw new IllegalArgumentException("折扣金额不能为负数");
        }
        this.discountAmount = discountAmount;
    }
    
    public double getMinimumOrderAmount() {
        return minimumOrderAmount;
    }
    
    public void setMinimumOrderAmount(double minimumOrderAmount) {
        if (minimumOrderAmount < 0) {
            throw new IllegalArgumentException("最小订单金额不能为负数");
        }
        this.minimumOrderAmount = minimumOrderAmount;
    }
}