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今天学习了接口，策略模式（Strategy Pattern）

为了以后不加新算法时，不改SmartHomeQuotation类，SmartHomeQuotation类只负责“把总价交给策略对象计算”，至于怎么算是策略对象的事。PercentageDiscountStrategy类做的事和SmartHomeQuotation类里现有的方法一样。但接口的意义不在于做新的事，而在于把“怎么做”从“做什么”里解耦出来，让系统可以无限扩展新算法而不修改旧代码。这就是策略模式（Strategy Pattern）

main()，新增菜单 7 （通过接口来实现）

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package cn.com.d99714.smart.service;

import cn.com.d99714.smart.common.Config;
import cn.com.d99714.smart.entity.*;
import cn.com.d99714.smart.strategy.DiscountStrategy;
import cn.com.d99714.smart.strategy.PercentageDiscountStrategy;

import java.util.Scanner;

public class SmartHomeTest {
    // Test 类私有的交互常量
    private static final String MENU_TITLE = "===== 智能家居报价系统 V0.x =====";
    private static final String MENU_EXIT = "0. 退出";
    private static final String MSG_INVALID = "无效选项";
    private static final String MSG_SUCCESS = "创建成功";

    //  模拟数据存储
    private static SmartHomeQuotation[] quotations = new SmartHomeQuotation[10];
    private static int quotationCount = 0;

    private static Person[] people = new Person[10];
    private static int peopleCount = 0;

    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        //  预置测试数据
        initTestData(); //  初始化数据

        //  菜单循环
        while (true) {
            printMenu();    //  输出菜单

            String selected = scanner.nextLine().trim();
            switch (selected) {
                case "1" -> createCustomer();      // 创建客户
                case "2" -> createQuotation();     // 创建报价单
                case "3" -> showQuotationList();   // 查看报价单列表（摘要）
                case "4" -> showQuotationDetail(); // 查看报价单详情
                case "5" -> showRoleDemo();        // 多态角色展示
                case "6" -> discountDemo();        // 折扣计算演示
                case "7" -> showStategyDemo();  //  折扣方案演示
                case "0" -> {                      // 退出
                    System.out.println("Bye. See you next time.");
                    return;
                }
                default -> System.out.println("无效选项，请重新输入");
            }
            System.out.println();
        }
    }

    /**
     * 1. 打印菜单（方法提取）
     */
    private static void printMenu() {
        System.out.println("========== 智能家居报价系统 v0.1 ==========");
        System.out.println("1. 创建客户");
        System.out.println("2. 创建报价单");
        System.out.println("3. 查看报价单列表");
        System.out.println("4. 查看报价单详情");
        System.out.println("5. 多态角色展示");
        System.out.println("6. 折扣计算演示");
        System.out.println("7. 折扣方案演示");
        System.out.println("0. 退出");
        System.out.print("请选择（1-6）【0-退出】：");
    }

    /**
     * 2. 预置测试数据（方法提取）
     */
    private static void initTestData() {
        Company vendor = new Company("张经理", "13829871635", "视声智能",
                "广州市黄埔区", "KNX全屋智能/灯光/安防");
        Person client1 = new Customer("赵今麦", "15138473848", "上海市静安区", 533);
        Person client2 = new Company("李经理", "13150432864", "杜亚窗帘",
                "杭州市拱墅区", "智能窗帘/智能门锁");
        Person worker = new Worker("王师傅", "13022531893", "电工", 2, 4.2);

        people[peopleCount++] = vendor;
        people[peopleCount++] = client1;
        people[peopleCount++] = client2;
        people[peopleCount++] = worker;

        SmartHomeQuotation q1 = new SmartHomeQuotation(
                Config.QUOTATION_PREFIX + "20260001-000001",
                "2026-10-02 16:35:11", "赵女士静安府全屋智能",
                client1, vendor, 35800.0, 5800.0, 6500.0, 4200.0, 2000.0);
        q1.setTotalDiscount(0.85);

        SmartHomeQuotation q2 = new SmartHomeQuotation(
                Config.QUOTATION_PREFIX + "20260001-000002",
                "2026-10-02 16:37:20", "杜亚展厅智能改造",
                client2, vendor, 28000.0, 3500.0, 4000.0, 2500.0, 1500.0);
        q2.setTotalDiscount(0.80);

        quotations[quotationCount++] = q1;
        quotations[quotationCount++] = q2;
    }

    /**
     * 3. 创建客户（方法提取）
     */
    private static void createCustomer() {
        System.out.println("创建客户");
        System.out.print("类型（1-业主 2-公司 3-师傅）：");
        String type = scanner.nextLine().trim();

        System.out.print("姓名：");
        String name = scanner.nextLine().trim();

        System.out.print("电话：");
        String phone = scanner.nextLine().trim();

        switch (type) {
            case "1" -> {
                System.out.print("房屋地址：");
                String addr = scanner.nextLine().trim();
                System.out.print("房屋面积：");
                double area = Double.parseDouble(scanner.nextLine().trim());
                people[peopleCount++] = new Customer(name, phone, addr, area);
            }
            case "2" -> {
                System.out.print("公司名称：");
                String cName = scanner.nextLine().trim();
                System.out.print("公司地址：");
                String cAddr = scanner.nextLine().trim();
                people[peopleCount++] = new Company(name, phone, cName, cAddr, "");
            }
            case "3" -> {
                System.out.print("工种：");
                String job = scanner.nextLine().trim();
                System.out.print("工龄：");
                int year = Integer.parseInt(scanner.nextLine().trim());
                System.out.print("评分：");
                double score = Double.parseDouble(scanner.nextLine().trim());
                people[peopleCount++] = new Worker(name, phone, job, year, score);
            }
            default -> System.out.println("无效类型");
        }
        System.out.println("创建成功！");
    }

    /**
     * 4. 创建报价单（方法提取）
     */
    private static void createQuotation() {
        if (peopleCount < 2) {
            System.out.println("请先创建客户和厂家");
            return;
        }
        System.out.println("创建报价单");
        //  直接选预置数据，不交互选客户
        System.out.println("功能开发中，请使用预置数据（选项3/4查看）");
    }

    /**
     * 5. 查看报价单列表（方法提取）
     */
    private static void showQuotationList() {
        System.out.println("报价单列表");
        for (int i = 0; i < quotationCount; i++) {
            System.out.println((i + 1) + ". " + quotations[i].getSummaryLine());
        }
        if (quotationCount == 0) {
            System.out.println("暂无报价单");
        }
    }

    /**
     * 6. 查看报价单详情（方法提取）
     */
    private static void showQuotationDetail() {
        System.out.print("请输入报价单序号（1-" + quotationCount + "）：");
        int idx = Integer.parseInt(scanner.nextLine().trim()) - 1;
        if (idx < 0 || idx >= quotationCount) {
            System.out.println("序号无效");
            return;
        }
        System.out.println(quotations[idx]);
    }

    /**
     * 7. 多态角色展示（方法提取）
     */
    private static void showRoleDemo() {
        System.out.println("多态角色展示");
        for (int i = 0; i < peopleCount; i++) {
            Person p = people[i];
            System.out.println(p.showRole() + " " + p.getName());
            System.out.println("  " + p.introduce());
        }
    }

    /**
     * 8. 折扣计算演示（方法提取）
     */
    private static void discountDemo() {
        System.out.println("折扣计算演示");
        for (int i = 0; i < quotationCount; i++) {
            SmartHomeQuotation q = quotations[i];
            System.out.printf("%s 原价：%,.2f，%s后：%,.2f，优惠：%,.2f%n",
                    q.getQuotationNo(), q.calcOriginalTotalAmount(), q.getDiscountDesc(),
                    q.calcDiscountedTotalAmount(), q.calcOriginalTotalAmount() - q.calcDiscountedTotalAmount());
        }
    }

    /**
     * 9. 策略接口演示（方法提取）
     */
    private static void showStategyDemo(){
        System.out.println("策略接口演示");
        DiscountStrategy s1 = new PercentageDiscountStrategy(0.85);
        DiscountStrategy s2 = new PercentageDiscountStrategy(0.80);
        System.out.printf(" %s 接口策略【%s】：%,.2f 元 %n",
                quotations[0].getQuotationNo(),
                s1.getStrategyName(),
                quotations[0].getDiscountedTotal(s1));
        System.out.printf(" %s 接口策略【%s】：%,.2f 元 %n",
                quotations[1].getQuotationNo(),
                s2.getStrategyName(),
                quotations[1].getDiscountedTotal(s2));
    }
}

新增DiscountStrategy接口，两个方法，一个是获取整单折扣后的金额，一个是获取折扣的中文描述

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package cn.com.d99714.smart.strategy;

public interface DiscountStrategy {
    //  获取整单折扣后的金额，相当于SmartHomeQuotation类中的getDiscountedTotal()
    double applyDiscount(double amount);

    //  获取折扣的中文描述，相当于SmartHomeQuotation类中的getDiscountDesc()
    String getStrategyName();
}

新增PercentageDiscountStrategy类，实现DiscountStrategy接口的两个方法

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package cn.com.d99714.smart.strategy;

public class PercentageDiscountStrategy implements DiscountStrategy{
    private double rate;

    public PercentageDiscountStrategy(double rate){
        this.rate = rate;
    }

    @Override
    public double applyDiscount(double amount){
        return amount * rate;
    }

    @Override
    public String getStrategyName(){
        return (int)(rate * 100) + "%折扣";
    }
}

SmartHomeQuotation类，新增：通过接口实现类的方法来获取整单折扣后的金额

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package cn.com.d99714.smart.entity;

import cn.com.d99714.smart.common.Config;
import cn.com.d99714.smart.strategy.DiscountStrategy;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class SmartHomeQuotation {
    private String quotationNo = "";
    private String quotationDate = "";
    private String projectName = "";
    private Person client;
    private Company vendor;
    private double deviceCost = 0.0;
    private double materialCost = 0.0;
    private double installCost = 0.0;
    private double debugCost = 0.0;
    private double otherCost = 0.0;

    //  分类折扣
    private double deviceDiscount = 1.0;
    private double materialDiscount = 1.0;
    private double installDiscount = 1.0;
    private double debugDiscount = 1.0;
    private double otherDiscount = 1.0;
    //  整单折扣
    private double totalDiscount = 1.0;

    public SmartHomeQuotation() {
    }

    public SmartHomeQuotation(String quotationNo, String quotationDate, String projectName, Person client, Company vendor, double deviceCost, double materialCost, double installCost, double debugCost, double otherCost) {
        this.setQuotationNo(quotationNo);
        this.setQuotationDate(quotationDate);
        this.setProjectName(projectName);
        this.setClient(client);
        this.setVendor(vendor);
        this.setDeviceCost(deviceCost);
        this.setMaterialCost(materialCost);
        this.setInstallCost(installCost);
        this.setDebugCost(debugCost);
        this.setOtherCost(otherCost);
    }

    public void setQuotationNo(String quotationNo) {
        this.quotationNo = quotationNo;
    }

    public void setQuotationDate(String quotationDate) {
        this.quotationDate = quotationDate;
    }

    public void setProjectName(String projectName) {
        this.projectName = projectName;
    }

    public void setClient(Person client) {
        this.client = client;
    }

    public void setVendor(Company vendor) {
        this.vendor = vendor;
    }

    public void setDeviceCost(double deviceCost) {
        this.deviceCost = deviceCost;
    }

    public void setMaterialCost(double materialCost) {
        this.materialCost = materialCost;
    }

    public void setInstallCost(double installCost) {
        this.installCost = installCost;
    }

    public void setDebugCost(double debugCost) {
        this.debugCost = debugCost;
    }

    public void setOtherCost(double otherCost) {
        this.otherCost = otherCost;
    }

    public void setDeviceDiscount(double deviceDiscount) {
        if (deviceDiscount < Config.MIN_DISCOUNT_RATE || deviceDiscount > Config.MAX_DISCOUNT_RATE) {
            System.out.println(Config.MSG_WARN_PREFIX + Config.MSG_DISCOUNT_RATE_INVALID);
            return;
        }
        this.deviceDiscount = deviceDiscount;
    }

    public void setMaterialDiscount(double materialDiscount) {
        if (materialDiscount < Config.MIN_DISCOUNT_RATE || materialDiscount > Config.MAX_DISCOUNT_RATE) {
            System.out.println(Config.MSG_WARN_PREFIX + Config.MSG_DISCOUNT_RATE_INVALID);
            return;
        }
        this.materialDiscount = materialDiscount;
    }

    public void setInstallDiscount(double installDiscount) {
        if (installDiscount < Config.MIN_DISCOUNT_RATE || installDiscount > Config.MAX_DISCOUNT_RATE) {
            System.out.println(Config.MSG_WARN_PREFIX + Config.MSG_DISCOUNT_RATE_INVALID);
            return;
        }
        this.installDiscount = installDiscount;
    }

    public void setDebugDiscount(double debugDiscount) {
        if (debugDiscount < Config.MIN_DISCOUNT_RATE || debugDiscount > Config.MAX_DISCOUNT_RATE) {
            System.out.println(Config.MSG_WARN_PREFIX + Config.MSG_DISCOUNT_RATE_INVALID);
            return;
        }
        this.debugDiscount = debugDiscount;
    }

    public void setOtherDiscount(double otherDiscount) {
        if (otherDiscount < Config.MIN_DISCOUNT_RATE || otherDiscount > Config.MAX_DISCOUNT_RATE) {
            System.out.println(Config.MSG_WARN_PREFIX + Config.MSG_DISCOUNT_RATE_INVALID);
            return;
        }
        this.otherDiscount = otherDiscount;
    }

    public void setTotalDiscount(double totalDiscount) {
        if (totalDiscount < Config.MIN_DISCOUNT_RATE || totalDiscount > Config.MAX_DISCOUNT_RATE) {
            System.out.println(Config.MSG_WARN_PREFIX + Config.MSG_DISCOUNT_RATE_INVALID);
            return;
        }
        this.totalDiscount = totalDiscount;
    }

    public String getQuotationNo() {

        return this.quotationNo;
    }

    public String getQuotationDate() {
        LocalDateTime dateTime = LocalDateTime.parse(this.quotationDate, Config.DATE_TIME_INPUT_FORMATTER);
        return dateTime.format(Config.DATE_TIME_DISPLAY_FORMATTER);
    }

    public String getProjectName() {
        return this.projectName;
    }

    public Person getClient() {
        return this.client;
    }

    public Company getVendor() {
        return this.vendor;
    }

    public double getDeviceCost() {
        return this.deviceCost;
    }

    public double getMaterialCost() {
        return this.materialCost;
    }

    public double getInstallCost() {
        return this.installCost;
    }

    public double getDebugCost() {
        return this.debugCost;
    }

    public double getOtherCost() {
        return this.otherCost;
    }

    public double getDeviceDiscount() {
        return this.deviceDiscount;
    }

    public double getMaterialDiscount() {
        return this.materialDiscount;
    }

    public double getInstallDiscount() {
        return this.installDiscount;
    }

    public double getDebugDiscount() {
        return this.debugDiscount;
    }

    public double getOtherDiscount() {
        return this.otherDiscount;
    }

    public double getTotalDiscount() {
        return this.totalDiscount;
    }

    /**
     * 计算原价的总金额
     * @return 原价的总金额
     */
    public double calcOriginalTotalAmount() {
        return (deviceCost + materialCost + installCost + debugCost + otherCost);
    }

    /**
     * 计算优惠后的总金额 （总金额 = 设备费用 * 折扣 + 材料费用 * 折扣 + 安装费用 * 折扣 + 调试费用 * 折扣 + 其他费用 * 折扣） * 折扣      *
     * @return 折扣后的总金额
     */
    public double calcDiscountedTotalAmount() {
        double dc = deviceCost * deviceDiscount;
        double mc = materialCost * materialDiscount;
        double ic = installCost * installDiscount;
        double bc = debugCost * debugDiscount;
        double oc = otherCost * otherDiscount;

        return (dc + mc + ic + bc + oc) * totalDiscount;
    }

    /**
     * 计算优惠的金额（优惠的金额 = 原始的总金额 - 优惠后的总金额）     *
     * @return 优惠的金额
     */
    public double caclDiscountAmount() {
        return calcOriginalTotalAmount() - calcDiscountedTotalAmount();
    }

    //  TODO：测试，要删除
    /**
     * 试算：不修改字段，只返回给定折扣率的计算结果
     * @param discountRate 试算折扣率
     * @return 试算金额
     */
    public double getDiscountedTotal(double discountRate) {
        if (discountRate < 0.0 || discountRate > 1.0) {
            System.out.println(Config.MSG_WARN_PREFIX + Config.MSG_DISCOUNT_RATE_INVALID);
            return calcOriginalTotalAmount();
        }
        return calcOriginalTotalAmount() * discountRate;
    }

    /**
     * 获取客户信息，通过 instanceof来判断客户是 Customer还是 Company
     * @return  客户类型：Customer或 Company（Config类有配置）
     */
    public String getClientDisplay() {
        if (client instanceof Customer) {
            Customer cu = (Customer) client;
            return cu.getName() + Config.TAG_CUSTOMER;
        } else if (client instanceof Company) {
            Company co = (Company) client;
            return co.getCompanyName() + Config.TAG_COMPANY;
        }
        return "";
    }

    /**
     * 获取客户的完整信息，通过 instanceof来判断客户是 Customer还是 Company
     * @return  客户信息
     */
    public String getClientFullInfo() {
        if (client instanceof Customer) {
            Customer cu = (Customer) client;
            return Config.TAG_CUSTOMER + "电话：" + cu.getPhone() + "，地址：" + cu.getHouseAddress() + "，房屋面积：" + cu.getHouseArea() + "m²";
        } else if (client instanceof Company) {
            Company co = (Company) client;
            return Config.TAG_COMPANY + "联系人：" + co.getName() + "，电话：" + co.getPhone() + "，地址：" + co.getAddress();
        }
        return "";
    }

    /**
     * 折扣率转中文描述
     * 1.0 → 原价, 0.85 → 85折, 0.8 → 8折, 0.0 → 免费
     * @return  中文描述
     */
    public String getDiscountDesc() {
        if (totalDiscount == Config.MAX_DISCOUNT_RATE) return "原价";
        if (totalDiscount == Config.MIN_DISCOUNT_RATE) return "免费";

        long percent = Math.round(totalDiscount * 100);  // 0.85→85, 0.8→80
        if (percent % 10 == 0) {
            return (percent / 10) + "折";   // 80→8折, 50→5折
        } else {
            return percent + "折";           // 85→85折, 88→88折
        }
    }

    /**
     * 报价单摘要展示
     * @return  报价单的摘要
     */
    public String getSummaryLine() {
        return String.format("%s | %s | %s | 原始金额：%s 元 | 折扣：%.0f%% | 折后金额：%s 元",
                quotationNo,
                projectName,
                getClientDisplay(),
                String.format(Config.AMOUNT_FORMAT, calcOriginalTotalAmount()),
                totalDiscount * 100,
                String.format(Config.AMOUNT_FORMAT, calcDiscountedTotalAmount())
        );
    }

    /**
     * 重写 toString()
     * @return
     */
    @Override
    public String toString() {
        double totalAmount = calcDiscountedTotalAmount(); //  调用calcTotalAmount()，计算报价单总金额
        StringBuilder sb = new StringBuilder();

        //  静态拼接报价单的头
        sb.append(Config.LINE_CHAR.repeat(Config.LINE_TITLE_REPEAT_COUNT)).append(Config.QUOTATION_TITLE).append(Config.LINE_CHAR.repeat(Config.LINE_TITLE_REPEAT_COUNT)).append("\n");
        sb.append(String.format(Config.LABEL_QUOTATION_NO + "%s%n", getQuotationNo()));
        sb.append(String.format(Config.LABEL_QUOTATION_DATE + "%s%n", getQuotationDate()));
        sb.append(String.format(Config.LABEL_VENDOR + "%s%n", vendor.getCompanyName()));
        sb.append(String.format(Config.LABEL_PROJECT_NAME + "%s%n", getProjectName()));
        sb.append(String.format(Config.LABEL_CLIENT_INFO + "%s%n", getClientDisplay()));

        sb.append(Config.LINE_CHAR.repeat(Config.LINE_REPEAT_COUNT * 2)).append("\n");

        //  动态拼接报价单金额（按照总金额格式化后的长度右对齐）
        String totalStr = String.format(Config.AMOUNT_FORMAT, totalAmount);
        int width = totalStr.length();
        //  折后金额
        sb.append(String.format(Config.LABEL_DISCOUNTED_AMOUNT + "%," + width + ".2f" + " 元%n", calcDiscountedTotalAmount()));
        //  优惠金额
        sb.append(String.format(Config.LABEL_DISCOUNT_AMOUNT + "%," + width + ".2f" + " 元%n", caclDiscountAmount()));
        //  原始金额
        sb.append(String.format(Config.LABEL_TOTAL_AMOUNT + "%," + width + ".2f" + " 元（" + Config.LABEL_DISCOUNT_RATE + "%.0f %% ）%n", calcOriginalTotalAmount() , totalDiscount * 100));

        sb.append(Config.LINE_CHAR.repeat(Config.LINE_REPEAT_COUNT * 2)).append("\n");

        sb.append(Config.LABEL_DETAIL_PREFIX + "\n");
        sb.append(String.format(Config.LABEL_DEVICE_COST + "%," + width + ".2f" + " 元（" + Config.LABEL_DISCOUNT_RATE + "%.0f %% ）%n", deviceCost * deviceDiscount, deviceDiscount * 100));
        sb.append(String.format(Config.LABEL_MATERIAL_COST + "%," + width + ".2f" + " 元（" + Config.LABEL_DISCOUNT_RATE + "%.0f %%） %n", materialCost * materialDiscount, materialDiscount * 100));
        sb.append(String.format(Config.LABEL_INSTALL_COST + "%," + width + ".2f" + " 元（" + Config.LABEL_DISCOUNT_RATE + "%.0f %% ）%n", installCost * installDiscount, installDiscount * 100));
        sb.append(String.format(Config.LABEL_DEBUG_COST + "%," + width + ".2f" + " 元（" + Config.LABEL_DISCOUNT_RATE + "%.0f %% ）%n", debugCost * debugDiscount, debugDiscount * 100));
        sb.append(String.format(Config.LABEL_OTHER_COST + "%," + width + ".2f" + " 元（" + Config.LABEL_DISCOUNT_RATE + "%.0f %% ）%n", otherCost * otherDiscount, otherDiscount * 100));
        sb.append(Config.LINE_CHAR.repeat(Config.LINE_REPEAT_COUNT * 2)).append("\n");

        return sb.toString();
    }

    /**
     * 获取整单折扣的总金额（调用接口实现类 discountStrategy中的 applyDiscount()方法）
     * @param discountStrategy  折扣策略（也就是折扣）
     * @return  整单折扣的总金额（原始金额打折后的金额）
     */
    public double getDiscountedTotal(DiscountStrategy discountStrategy){
        return discountStrategy.applyDiscount(calcOriginalTotalAmount());
    }
}
Java
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鱼友0258
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