在工廠模式中，我們在創(chuàng)建對象時不會對客戶端暴露創(chuàng)建邏輯，并且是通過使用一個共同的接口來指向新創(chuàng)建的對象。定義一個用于創(chuàng)建對象的接口，讓子類決定實例化哪個類，解決不同條件下創(chuàng)建不同的類。簡單實現(xiàn)如下：
1.創(chuàng)建接口

public interface Shape {
    void draw();
}

2.創(chuàng)建各種實體類

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

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

3.創(chuàng)建工廠類

public class ShapeFactory {
    public Shape getShape(String type){
        if(type == null)
            return null;
        switch (type){
            case "triangle":
                return new Triangle();
            case "circle":
                return new Circle();
             default:
                 return null;
        }
    }
}

4.測試類

public class FactoryDemo {
    public static void main(String[] args) {
        ShapeFactory factory = new ShapeFactory();
        Shape shape = factory.getShape("circle");
        shape.draw();
    }
}