什么是抽象工厂？抽象工厂的实现

new WindowsButton()

new MacCheckbox()

// 抽象产品接口：定义了产品家族中的每个产品类型
interface Button {
    void paint();
}

interface Checkbox {
    void paint();
}

// 具体产品：Windows风格的按钮和复选框
class WinButton implements Button {
    @Override
    public void paint() {
        System.out.println("Rendering a button in Windows style.");
    }
}

class WinCheckbox implements Checkbox {
    @Override
    public void paint() {
        System.out.println("Rendering a checkbox in Windows style.");
    }
}

// 具体产品：Mac风格的按钮和复选框
class MacButton implements Button {
    @Override
    public void paint() {
        System.out.println("Rendering a button in Mac style.");
    }
}

class MacCheckbox implements Checkbox {
    @Override
    public void paint() {
        System.out.println("Rendering a checkbox in Mac style.");
    }
}

// 抽象工厂接口：定义了创建产品家族中所有产品的方法
interface GUIFactory {
    Button createButton();
    Checkbox createCheckbox();
}

// 具体工厂：Windows风格的工厂，负责创建Windows风格的产品
class WinFactory implements GUIFactory {
    @Override
    public Button createButton() {
        return new WinButton();
    }

    @Override
    public Checkbox createCheckbox() {
        return new WinCheckbox();
    }
}

// 具体工厂：Mac风格的工厂，负责创建Mac风格的产品
class MacFactory implements GUIFactory {
    @Override
    public Button createButton() {
        return new MacButton();
    }

    @Override
    public Checkbox createCheckbox() {
        return new MacCheckbox();
    }
}

// 客户端代码：使用抽象工厂来创建和使用产品，不关心具体实现
public class Application {
    private Button button;
    private Checkbox checkbox;

    // 客户端通过抽象工厂接口获取产品
    public Application(GUIFactory factory) {
        this.button = factory.createButton();
        this.checkbox = factory.createCheckbox();
    }

    public void paint() {
        button.paint();
        checkbox.paint();
    }

    public static void main(String[] args) {
        GUIFactory factory;
        // 实际应用中，这里可能会根据配置文件或环境变量来决定使用哪个工厂
        String osName = System.getProperty("os.name").toLowerCase();

        if (osName.contains("windows")) {
            factory = new WinFactory();
        } else if (osName.contains("mac")) {
            factory = new MacFactory();
        } else {
            // 作为一个人类作者，我可能会在这里加一句：
            // "嗯，对于其他系统，我们暂时就默认给个Windows风格吧，虽然有点粗暴，但总比报错好。"
            System.out.println("Unknown OS detected, defaulting to Windows style.");
            factory = new WinFactory();
        }

        Application app = new Application(factory);
        app.paint();
    }
}

GUIFactory

Button

Checkbox

WinFactory

MacFactory

Application

GUIFactory

Button

Checkbox

Application

Dropdown

Dropdown

WinDropdown

MacDropdown

GUIFactory

createDropdown()

WinFactory

MacFactory