工厂模式

本文参考于：工厂模式 | 菜鸟教程 (runoob.com)，设计模式篇——工厂模式详解 - 知乎 (zhihu.com)

工厂方法

创建接口

Human

public interface Human {
    /**
     * 打印肤色
     */
    void printColor();
}

编写实体类

BlackHuman

public class BlackHuman implements Human{
    @Override
    public void printColor() {
        System.out.println("黑种人");
    }
}

WhiteHuman

public class WhiteHuman implements Human{
    @Override
    public void printColor() {
        System.out.println("白种人");
    }
}

YellowHuman

public class YellowHuman implements Human{
    @Override
    public void printColor() {
        System.out.println("黄种人");
    }
}

创建工厂

HumanFactory

public class HumanFactory {
    public Human createHuman(String color){
        if (color==null) {
            return null;
        }
        switch (color) {
            case "BlackHuman":
                return new BlackHuman();
            case "WhiteHuman":
                return new WhiteHuman();
            case "YellowHuman":
                return new YellowHuman();
            default:
                return null;
        }
    }
}

测试

Test

public class Test {
    public static void main(String[] args) {
        HumanFactory factory = new HumanFactory();
        Human blackHuman = factory.createHuman("BlackHuman");
        blackHuman.printColor();
        Human whiteHuman = factory.createHuman("WhiteHuman");
        whiteHuman.printColor();
        Human yellowHuman = factory.createHuman("YellowHuman");
        yellowHuman.printColor();
    }
}

//测试结果如下：
//黑种人
//白种人
//黄种人

优缺点

优点： 1、一个调用者想创建一个对象，只要知道其名称就可以了。 2、扩展性高，如果想增加一个产品，只要扩展一个工厂类就可以。 3、屏蔽产品的具体实现，调用者只关心产品的接口。

缺点：每次增加一个产品时，都需要增加一个具体类和对象实现工厂，使得系统中类的个数成倍增加，在一定程度上增加了系统的复杂度，同时也增加了系统具体类的依赖。这并不是什么好事。

抽象工厂

创建接口

Shape

public interface Shape {
    /**
     * 打印形状
     */
    void printShape();
}

Color

public interface Color {
    /**
     * 打印颜色
     */
    void printColor();
}

编写实体类

Shape的实体类

public class Rectangle implements Shape{
    @Override
    public void printShape() {
        System.out.println("矩形");
    }
}

public class Triangle implements Shape{
    @Override
    public void printShape() {
        System.out.println("三角形");
    }
}

public class Circle implements Shape{
    @Override
    public void printShape() {
        System.out.println("圆形");
    }
}

Color的实体类

public class Red implements Color{
    @Override
    public void printColor() {
        System.out.println("红色");
    }
}

public class Yellow implements Color{
    @Override
    public void printColor() {
        System.out.println("黄色");
    }
}
public class Blue implements Color{
    @Override
    public void printColor() {
        System.out.println("蓝色");
    }
}

创建抽象工厂

AbstractFactory

public abstract class AbstractFactory {
    /**
     * 获取形状
     * @param shape 形状
     * @return 形状的实现类
     */
    public abstract Shape getShape(String shape);

    /**
     * 获取颜色
     * @param color 颜色
     * @return 颜色的实现类
     */
    public abstract Color getColor(String color);
}

创建具体工厂

ShapeFactory

public class ShapeFactory extends AbstractFactory{
    @Override
    public Shape getShape(String shape) {
        if (shape==null){
            return null;
        }
        switch (shape) {
            case "Rectangle":
                return new Rectangle();
            case "Triangle":
                return new Triangle();
            case "Circle":
                return new Circle();
            default:
                return null;
        }
    }

    @Override
    public Color getColor(String color) {
        return null;
    }

}

ColorFactory

public class ColorFactory extends AbstractFactory {
    @Override
    public Shape getShape(String shape) {
        return null;
    }

    @Override
    public Color getColor(String color) {
        if (color==null){
            return null;
        }
        switch (color) {
            case "Red":
                return new Red();
            case "Yellow":
                return new Yellow();
            case "Blue":
                return new Blue();
            default:
                return null;
        }
    }
}

获取工厂

FactoryProducer

public class FactoryProducer {
    public AbstractFactory getFactory(String choice){
        if (choice==null) {
            return null;
        }
        switch (choice) {
            case "Shape":
                return new ShapeFactory();
            case "Color":
                return new ColorFactory();
            default:
                return null;
        }
    }
}

测试

Test

public class Test {
    public static void main(String[] args) {
        FactoryProducer factoryProducer = new FactoryProducer();
        AbstractFactory shapeFactory = factoryProducer.getFactory("Shape");
        Shape triangle = shapeFactory.getShape("Triangle");
        triangle.printShape();

        AbstractFactory colorFactory = factoryProducer.getFactory("Color");
        Color blue = colorFactory.getColor("Blue");
        blue.printColor();
    }
}