设计模式- Java

工厂模式

通过将对象的创建过程封装到一个工厂类中，使得客户端不需要直接使用 new 去创建对象，而是通过调用工厂方法来获取所需的对象。这样可以降低代码耦合度，并方便后续的扩展和维护。

示例代码

简单工厂模式（不配合策略模式）：

// 手机顶层接口
public interface Phone {
   
    void makeCall(String number);
}

// 华为手机实现
public class HuaweiPhone implements Phone {
   
    @Override
    public void makeCall(String number) {
   
        System.out.println("Using HuaweiPhone to call: " + number);
    }
}

// 苹果手机实现
public class ApplePhone implements Phone {
   
    @Override
    public void makeCall(String number) {
   
        System.out.println("Using ApplePhone to call: " + number);
    }
}

// 工厂类
public class PhoneFactory {
   
    public static Phone createPhone(String type) {
   
        switch (type) {
   
            case "Huawei":
                return new HuaweiPhone();
            case "Apple":
                return new ApplePhone();
            default:
                throw new IllegalArgumentException("Unknown phone type: " + type);
        }
    }
}

// 测试类
public class Main {
   
    public static void main(String[] args) {
   
        Phone huawei = PhoneFactory.createPhone("Huawei");
        huawei.makeCall("123456789");

        Phone apple = PhoneFactory.createPhone("Apple");
        apple.makeCall("987654321");
    }
}

---

工厂模式 + 策略模式

目的：当需要扩展更多设备（如平板）时，可以抽象顶层接口，将工厂类的职责划分得更清晰。

// 顶层接口：设备
public interface Device {
   
    void start();
}

// 手机实现
public class PhoneDevice implements Device {
   
    @Override
    public void start() {
   
        System.out.println("Starting Phone...");
    }
}

// 平板实现
public class TabletDevice implements Device {
   
    @Override
    public void start() {
   
        System.out.println("Starting Tablet...");
    }
}

// 策略模式：设备工厂接口
public interface DeviceFactory {
   
    Device createDevice();
}

// 手机工厂实现
public class PhoneFactory implements DeviceFactory {
   
    @Override
    public Device createDevice() {
   
        return new PhoneDevice();
    }
}

// 平板工厂实现
public class TabletFactory implements DeviceFactory {
   
    @Override
    public Device createDevice() {
   
        return new TabletDevice();
    }
}

// 客户端
public class Main {
   
    public static void main(String[] args) {
   
        DeviceFactory phoneFactory = new PhoneFactory();
        Device phone = phoneFactory.createDevice();
        phone.start();

        DeviceFactory tabletFactory = new TabletFactory();
        Device tablet = tabletFactory.createDevice();
        tablet.start();
    }
}

---

配合 Map 的映射关系

当设备种类较多时，可以用 Map 管理工厂类，动态获取：

import java.util.HashMap;
import java.util.Map;

public class DeviceFactoryRegistry {
   
    private static final Map<String, DeviceFactory> factoryMap = new HashMap<>();

    static {
   
        factoryMap.put("Phone", new PhoneFactory());
        factoryMap.put("Tablet", new TabletFactory());
    }

    public static Device getDevice(String type) {
   
        DeviceFactory factory = factoryMap.get(type);
        if (factory == null) {
   
            throw new IllegalArgumentException("Unknown device type: " + type);
        }
        return factory.createDevice();