工厂模式

Github：FactoryPattern.java

创建接口，定义公共方法

/**
 * 公共接口
 */
public interface Shape{
    void draw();
}

创建接口实现类

矩形实现类

/**
 * 矩形
 */
public class Rectangle implements Shape{
    @Override
    public void draw() {
        System.out.println("this is Rectangle::draw method!");
    }
}

圆形实现类

/**
 * 圆形
 */
public class Circle implements Shape{
    @Override
    public void draw() {
        System.out.println("this is Circle::draw method!");
    }
}

正方形实现类

/**
 * 正方形
 */
public class Square implements Shape{
    @Override
    public void draw() {
        System.out.println("this is Square::draw method!");
    }
}

定义形状枚举类

/**
 * 定义可使用的类型，所有新的在此增加即可
 */
public enum ShapeEnums{
    RECTANGLE, CIRCLE, SQUARE
    ;
}

创建工厂类

/**
 * 定义 shape工厂
 */
public class ShapeFactory{
    private Shape shape;
    public ShapeFactory(ShapeEnums shape){
        switch (shape){
            case RECTANGLE: this.shape = new Rectangle(); break;
            case CIRCLE: this.shape = new Circle(); break;
            case SQUARE: this.shape = new Square(); break;
            default: throw new IllegalArgumentException("not found match construct method with : "+shape);
        }
    }
    public Shape getShape() {
        return shape;
    }
}

测试，打印矩形

public static void main(String[] args) {
    FactoryPattern factoryPattern = new FactoryPattern();
    factoryPattern.factory();
}
public void factory(){
    ShapeFactory factory = new ShapeFactory(ShapeEnums.CIRCLE);
    factory.getShape().draw();
}

输出结果：

this is Rectangle::draw method!

打印其他类型：
只需要创建工厂实例即可。

public void factory(){
    // 矩形
    ShapeFactory factory = new ShapeFactory(ShapeEnums.RECTANGLE);
    factory.getShape().draw();
    // 圆形
    factory = new ShapeFactory(ShapeEnums.CIRCLE);
    factory.getShape().draw();
    // 正方形
    factory = new ShapeFactory(ShapeEnums.SQUARE);
    factory.getShape().draw();
}

输出结果：

this is Rectangle::draw method!
this is Circle::draw method!
this is Square::draw method!

如何新增其他类型

1. 在枚举类新增指定类型

比如新增菱形

/**
 * 定义可使用的类型，所有新的在此增加即可
 */
public enum ShapeEnums{
    RECTANGLE, CIRCLE, SQUARE, RHOMBUS
    ;
}

2. 新增菱形实现类

/**
 * 菱形
 */
public class Rhombus implements Shape{
    @Override
    public void draw() {
        System.out.println("this is Rhombus::draw method!");
    }
}

3. 修改工厂类，新增菱形实例化

/**
 * 定义 shape工厂
 */
public class ShapeFactory{
    private Shape shape;
    public ShapeFactory(ShapeEnums shape){
        switch (shape){
            case RECTANGLE: this.shape = new Rectangle(); break;
            case CIRCLE: this.shape = new Circle(); break;
            case SQUARE: this.shape = new Square(); break;
            case RHOMBUS: this.shape = new Rhombus(); break;
            default: throw new IllegalArgumentException("not found match construct method with : "+shape);
        }
    }
    public Shape getShape() {
        return shape;
    }
}

4. 测试

public void factory(){
    // 矩形
    ShapeFactory factory = new ShapeFactory(ShapeEnums.RECTANGLE);
    factory.getShape().draw();
    // 圆形
    factory = new ShapeFactory(ShapeEnums.CIRCLE);
    factory.getShape().draw();
    // 正方形
    factory = new ShapeFactory(ShapeEnums.SQUARE);
    factory.getShape().draw();
    // 菱形
    factory = new ShapeFactory(ShapeEnums.RHOMBUS);
    factory.getShape().draw();
}

输出结果：此时会发现多了打印菱形结果

this is Rectangle::draw method!
this is Circle::draw method!
this is Square::draw method!
this is Rhombus::draw method!

参考

菜鸟教程 - 工厂模式