Java设计模式-通俗举例
设计模式就像做菜的食谱，告诉我们遇到常见问题时该用什么"烹饪方法"。今天我就用最生活化的例子，带大家轻松掌握23种设计模式的精髓。
一、创建型模式（5种）：怎么"造东西"
1. 单例模式：公司的CEO
问题：一个公司只需要一个CEO
解决：
public class CEO {private static CEO instance;private CEO() {} // 防止外部newpublic static CEO getInstance() {if (instance == null) {instance = new CEO();}return instance;}
}生活类比：不管问多少个人"谁是CEO"，得到的都是同一个人
2. 工厂方法：奶茶店点单
问题：顾客不需要知道奶茶怎么做
解决：
interface MilkTea {void make();
}class BubbleTea implements MilkTea {public void make() { System.out.println("加珍珠"); }
}class MilkTeaShop {public MilkTea orderTea(String type) {if ("bubble".equals(type)) {return new BubbleTea();}// 其他口味...}
}生活类比：告诉店员要珍珠奶茶，店员帮你做好，你不用管制作过程
3. 抽象工厂：家具套装
问题：要买整套风格匹配的家具
解决：
interface FurnitureFactory {Chair createChair();Table createTable();
}class ModernFactory implements FurnitureFactory {public Chair createChair() { return new ModernChair(); }public Table createTable() { return new ModernTable(); }
}生活类比：买"北欧风"套装，确保沙发、茶几风格统一
4. 建造者模式：组装电脑
问题：配电脑有很多可选配件，组合复杂
解决：
class Computer {private String CPU;private String GPU;// 其他配件...// 建造者内部类public static class Builder {private String CPU;private String GPU;public Builder setCPU(String cpu) {this.CPU = cpu;return this; // 返回Builder自己，实现链式调用}public Builder setGPU(String gpu) {this.GPU = gpu;return this;}public Computer build() {Computer computer = new Computer();computer.CPU = this.CPU;computer.GPU = this.GPU;return computer;}}
}// 使用
Computer myPC = new Computer.Builder().setCPU("i7").setGPU("RTX 3080").build();生活类比：去电脑城配机，告诉老板："我要i7CPU，3080显卡，16G内存..."，老板帮你组装好整机
5. 原型模式：复印简历
问题：创建重复对象成本高
解决：
class Resume implements Cloneable {private String name;private String experience;// 实现克隆方法public Resume clone() {try {return (Resume)super.clone();} catch (CloneNotSupportedException e) {return null;}}
}// 使用
Resume original = new Resume();
Resume copy = original.clone();生活类比：复印简历原件，不用每次都手写一份新的
二、结构型模式（7种）：怎么"组装东西"
1. 适配器：电源转换插头
问题：中国插头没法用美国插座
解决：
class ChinesePlug {void charge() { System.out.println("中国插头充电"); }
}interface AmericanSocket {void power();
}class Adapter implements AmericanSocket {private ChinesePlug plug;public Adapter(ChinesePlug plug) {this.plug = plug;}public void power() {plug.charge();}
}生活类比：转换插头让不同标准的电器能工作
2. 装饰器：给奶茶加料
问题：想灵活添加珍珠、椰果等配料
解决：
abstract class MilkTea {abstract String getDescription();abstract double cost();
}class BubbleDecorator extends MilkTea {private MilkTea milkTea;public BubbleDecorator(MilkTea milkTea) {this.milkTea = milkTea;}public String getDescription() {return milkTea.getDescription() + "+珍珠";}public double cost() {return milkTea.cost() + 2.0;}
}生活类比：先要杯原味奶茶，再说"加珍珠"，"再加布丁"
3. 桥接模式：遥控器与电器
问题：遥控器要控制多种电器
解决：
// 实现部分
interface Device {void turnOn();void turnOff();
}class TV implements Device {public void turnOn() { System.out.println("电视开机"); }public void turnOff() { System.out.println("电视关机"); }
}// 抽象部分
abstract class RemoteControl {protected Device device;public RemoteControl(Device device) {this.device = device;}abstract void power();
}class BasicRemote extends RemoteControl {public BasicRemote(Device device) {super(device);}public void power() {device.turnOn();}
}生活类比：同一个遥控器可以控制电视、空调等不同电器
4. 组合模式：公司组织架构
问题：统一处理单个对象和对象集合
解决：
interface Employee {void showDetails();
}class Developer implements Employee {private String name;public void showDetails() {System.out.println("开发员：" + name);}
}class Department implements Employee {private List<Employee> employees = new ArrayList<>();public void addEmployee(Employee e) {employees.add(e);}public void showDetails() {for (Employee e : employees) {e.showDetails();}}
}生活类比：查看部门信息会自动展示所有成员信息
5. 享元模式：共享单车
问题：大量相似对象消耗内存
解决：
class Bike {private String color; // 内部状态（可共享）private String rider; // 外部状态（不可共享）public Bike(String color) {this.color = color;}public void ride(String rider) {this.rider = rider;System.out.println(rider + "骑走" + color + "单车");}
}class BikeFactory {private static Map<String, Bike> pool = new HashMap<>();public static Bike getBike(String color) {if (!pool.containsKey(color)) {pool.put(color, new Bike(color));}return pool.get(color);}
}生活类比：共享单车公司不会为每个用户造新车，而是大家共用
6. 代理模式：房产中介
问题：不想/不能直接访问对象
解决：
interface House {void sell();
}class Owner implements House {public void sell() {System.out.println("房主卖房");}
}class Agent implements House {private House house;public Agent(House house) {this.house = house;}public void sell() {System.out.println("中介带看房");house.sell();System.out.println("中介收佣金");}
}生活类比：通过中介买房，不用直接联系房东
三、行为型模式（11种）：怎么做事情
1. 观察者：微信群通知
问题：消息要实时通知所有群成员
解决：
class WeChatGroup {private List<Member> members = new ArrayList<>();public void addMember(Member m) {members.add(m);}public void notifyMembers(String msg) {for (Member m : members) {m.receive(msg);}}
}class Member {void receive(String msg) {System.out.println("收到消息：" + msg);}
}生活类比：群里发消息，所有成员手机都会响
2. 策略：出行导航
问题：根据情况选择不同路线
解决：
interface RouteStrategy {void buildRoute();
}class DrivingStrategy implements RouteStrategy {public void buildRoute() { System.out.println("开车路线"); }
}class WalkingStrategy implements RouteStrategy {public void buildRoute() { System.out.println("步行路线"); }
}class Navigator {private RouteStrategy strategy;public void setStrategy(RouteStrategy s) {this.strategy = s;}public void execute() {strategy.buildRoute();}
}生活类比：高德地图可以切换"驾车"、"步行"等不同导航模式
3. 责任链模式：审批流程
问题：请求需要多级处理
解决：
abstract class Approver {protected Approver next;public void setNext(Approver next) {this.next = next;}abstract void processRequest(int amount);
}class Manager extends Approver {public void processRequest(int amount) {if (amount <= 1000) {System.out.println("经理批准");} else if (next != null) {next.processRequest(amount);}}
}class CEO extends Approver {public void processRequest(int amount) {System.out.println("CEO批准");}
}// 使用
Approver chain = new Manager();
chain.setNext(new CEO());
chain.processRequest(5000); // CEO批准生活类比：报销流程，金额小的组长批，大的要经理批
4. 命令模式：餐厅点餐
问题：将请求封装为对象
解决：
interface Command {void execute();
}class OrderCommand implements Command {private Chef chef;private String dish;public OrderCommand(Chef chef, String dish) {this.chef = chef;this.dish = dish;}public void execute() {chef.cook(dish);}
}class Waiter {private List<Command> orders = new ArrayList<>();public void takeOrder(Command cmd) {orders.add(cmd);}public void placeOrders() {for (Command cmd : orders) {cmd.execute();}}
}生活类比：服务员记下订单（命令对象），后厨按订单做菜
5. 迭代器模式：电视频道切换
问题：统一遍历不同集合
解决：
interface ChannelIterator {boolean hasNext();String next();
}class TVChannelList {private String[] channels = {"CCTV1", "CCTV5", "HunanTV"};public ChannelIterator iterator() {return new ConcreteIterator();}private class ConcreteIterator implements ChannelIterator {private int position;public boolean hasNext() {return position < channels.length;}public String next() {return channels[position++];}}
}生活类比：用遥控器上下键切换频道，不用知道频道如何存储
6. 中介者模式：机场塔台
问题：对象间直接交互复杂
解决：
class Airplane {private ControlTower tower;public void requestLanding() {tower.requestLanding(this);}
}class ControlTower {public void requestLanding(Airplane plane) {System.out.println("允许降落");}
}生活类比：飞机不直接沟通，都通过塔台协调
7. 备忘录模式：游戏存档
问题：需要保存和恢复对象状态
解决：
class Game {private int level;public GameMemento save() {return new GameMemento(level);}public void load(GameMemento memento) {this.level = memento.getLevel();}
}class GameMemento {private final int level;public GameMemento(int level) {this.level = level;}public int getLevel() {return level;}
}生活类比：游戏存档读档功能
8. 状态模式：红绿灯切换
问题：对象行为随状态改变
解决：
interface TrafficLightState {void handle();
}class RedLight implements TrafficLightState {public void handle() {System.out.println("红灯停");}
}class TrafficLight {private TrafficLightState state;public void setState(TrafficLightState state) {this.state = state;}public void change() {state.handle();}
}生活类比：交通灯自动按红→绿→黄变化
9. 模板方法模式：冲泡饮料
问题：固定流程中的步骤变化
解决：
abstract class Beverage {// 模板方法（固定流程）final void prepare() {boilWater();brew();pourInCup();addCondiments();}abstract void brew();abstract void addCondiments();void boilWater() {System.out.println("烧水");}void pourInCup() {System.out.println("倒入杯子");}
}class Coffee extends Beverage {void brew() { System.out.println("冲泡咖啡"); }void addCondiments() { System.out.println("加糖和牛奶"); }
}生活类比：泡茶和泡咖啡步骤类似，但具体操作不同
10. 访问者模式：医生问诊
问题：对一组对象执行多种操作
解决：
interface Patient {void accept(Doctor visitor);
}class ChildPatient implements Patient {public void accept(Doctor visitor) {visitor.visit(this);}
}interface Doctor {void visit(ChildPatient patient);void visit(AdultPatient patient);
}class Pediatrician implements Doctor {public void visit(ChildPatient patient) {System.out.println("检查儿童生长发育");}public void visit(AdultPatient patient) {System.out.println("成人不看儿科");}
}生活类比：不同专科医生对病人做不同检查