设计模式之桥接、组合、装饰模式

一、桥接模式

1.所有电器的通用插座:

// bridge/device/Device.java
public interface Device {
// 所有电器必须实现的功能
    boolean isOn();
    void powerOn();
    void powerOff();
    void setVolume(int volume);
    int getVolume();
}

2.具体设备实现

设备1：电视实现

public class TV implements Device {
    private boolean isOn = false;
    private int volume = 50;

    @Override
    public boolean isOn() { return isOn; }

    @Override
    public void powerOn() {
        isOn = true;
        System.out.println("电视机已启动，欢迎使用");
    }

    @Override
    public void powerOff() {
        isOn = false;
        System.out.println("电视机已关闭");
    }

    @Override
    public void setVolume(int volume) {
        this.volume = Math.min(100, Math.max(0, volume));
        System.out.println("电视机音量设置：" + this.volume);
    }

    @Override
    public int getVolume() { return volume; }
}

设备2：空调实现

public class Radio implements Device {
    private boolean isOn = false;
    private int volume = 30;

    @Override
    public boolean isOn() { return isOn; }

    @Override
    public void powerOn() {
        isOn = true;
        System.out.println("收音机启动，开始播放广播");
    }

    @Override
    public void powerOff() {
        isOn = false;
        System.out.println("收音机已关闭");
    }

    @Override
    public void setVolume(int volume) {
        this.volume = Math.min(50, Math.max(0, volume)); // 收音机音量上限较低
        System.out.println("收音机音量设置：" + this.volume);
    }

    @Override
    public int getVolume() { return volume; }
}

3.遥控器抽象层

父类（模板）:

public abstract class RemoteControl {
    protected Device device; // 关键：持有一个设备

    public RemoteControl(Device device) {
        this.device = device;
    }

    public abstract void power();
    public abstract void volumeUp();
    public abstract void volumeDown();
}

子类

public class BasicRemote extends RemoteControl {
    public BasicRemote(Device device) {
        super(device);
    }

    @Override
    public void power() {
        if (device.isOn()) {
            device.powerOff();
        } else {
            device.powerOn();
        }
    }

    @Override
    public void volumeUp() {
        device.setVolume(device.getVolume() + 5);
    }

    @Override
    public void volumeDown() {
        device.setVolume(device.getVolume() - 5);
    }
}

4.测试类

public class Main {
    public static void main(String[] args) {
        // 测试电视机
        Device tv = new TV();
        RemoteControl tvRemote = new BasicRemote(tv);
        tvRemote.power();      // 开机
        tvRemote.volumeUp();   // 55
        
        // 测试收音机
        Device radio = new Radio();
        RemoteControl radioRemote = new BasicRemote(radio);
        radioRemote.power();    // 开机
        radioRemote.volumeUp();  // 35
    }
}

二、组件模式

1.所有物品的必需功能

public interface CatalogComponent {
    void display(int indent); // 缩进展示
    double calculatePrice(); // 计算总价
}

2.商品类

public class Product implements CatalogComponent {
    private String name;
    private double price;

    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }

    @Override
    public void display(int indent) {
        String space = "  ".repeat(indent);
        System.out.println(space + "📦 " + name + " ￥" + price);
    }

    @Override
    public double calculatePrice() {
        return price;
    }
}

3.商品分类

public class ProductCategory implements CatalogComponent {
    private String categoryName;
    private List<CatalogComponent> items = new ArrayList<>();

    public ProductCategory(String name) {
        this.categoryName = name;
    }

    public void addItem(CatalogComponent item) {
        items.add(item);
    }

    @Override
    public void display(int indent) {
        String space = "  ".repeat(indent);
        System.out.println(space + "📁 " + categoryName);
        for (CatalogComponent item : items) {
            item.display(indent + 1); // 递归调用
        }
    }

    @Override
    public double calculatePrice() {
        return items.stream()
                   .mapToDouble(CatalogComponent::calculatePrice)
                   .sum();
    }
}

4.测试类

public class Main {
    public static void main(String[] args) {
        CatalogComponent electronics = new ProductCategory("电子产品");
        electronics.addItem(new Product("iPhone", 5999));
        electronics.addItem(new Product("耳机", 399));

        electronics.display(0);
        System.out.println("总价值: ￥" + electronics.calculatePrice());
    }
}

三、装饰模式

1.武器接口

public interface Weapon {
    String getDescription();
    int getAttackPower();
}

2.基础武器实现

public class Sword implements Weapon {
    @Override
    public String getDescription() {
        return "🗡️ 铁剑";
    }

    @Override
    public int getAttackPower() {
        return 10;
    }
}

3.装饰器基类

public abstract class WeaponDecorator implements Weapon {
    protected Weapon decoratedWeapon;

    public WeaponDecorator(Weapon weapon) {
        this.decoratedWeapon = weapon;
    }

    @Override
    public String getDescription() {
        return decoratedWeapon.getDescription();
    }

    @Override
    public int getAttackPower() {
        return decoratedWeapon.getAttackPower();
    }
}

4.具体装饰器

装饰器1:

public class FireEnchant extends WeaponDecorator {
    public FireEnchant(Weapon weapon) {
        super(weapon);
    }

    @Override
    public String getDescription() {
        return super.getDescription() + " 🔥火焰附魔";
    }

    @Override
    public int getAttackPower() {
        return super.getAttackPower() + 5;
    }
}

装饰器2:

public class AttackBoost extends WeaponDecorator {
    public AttackBoost(Weapon weapon) {
        super(weapon);
    }

    @Override
    public String getDescription() {
        return super.getDescription() + " ⚡攻击强化";
    }

    @Override
    public int getAttackPower() {
        return super.getAttackPower() + 8;
    }
}

5.测试类

public class Main {
    public static void main(String[] args) {
        Weapon weapon = new Sword();
        weapon = new FireEnchant(weapon);
        weapon = new AttackBoost(weapon);

        System.out.println(weapon.getDescription()); 
        // 输出：🗡️ 铁剑 🔥火焰附魔 ⚡攻击强化
        System.out.println("攻击力: " + weapon.getAttackPower()); // 23
    }
}

关键点总结

模式	核心思想	类比场景	代码特征
桥接模式	抽象与实现解耦	遥控器 vs 不同电器	抽象类持有实现接口
组合模式	统一处理树状结构	商品分类嵌套	递归调用 + 组件集合
装饰模式	动态添加功能，无需修改原有代码	游戏装备强化	装饰器持有被装饰对象，链式调用