Java設計模式——抽象工廠模式

抽象工廠模式也是創建模式，可以把它理解成創建工廠的工廠，這種模式也是我們經常使用的。
在抽象工廠中的接口是用來創建工廠的，每個生成的工廠又都可以按照工廠模式創建其他對象。

舉例說明：

1. 創建Shape接口及其實現類Circle、Square、RoundedRectangle、RoundedSquare
2. 創建抽象工廠類AbstractFactory
3. 創建工廠類ShapeFactory，它繼承AbstractFactory抽象類
4. 創建工廠生成類FactoryProducer
5. 創建AbstractFactoryPatternDemo類，用來測試抽象工廠模式

1、創建接口Shape

public interface Shape {
   void draw();
}

2、創建接口Shape實現類

public class Rectangle implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside Rectangle::draw() method.");
   }
}

public class Square implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside Square::draw() method.");
   }
}

public class RoundedRectangle implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside RoundedRectangle::draw() method.");
   }
}

public class RoundedSquare implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside RoundedSquare::draw() method.");
   }
}

3、創建抽象類AbstractFactory

public abstract class AbstractFactory {
   abstract Shape getShape(String shapeType) ;
}

4、創建抽象類AbstractFactory的實現類

public class ShapeFactory extends AbstractFactory {
   @Override
   public Shape getShape(String shapeType){    
      if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();         
      }else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }  
      return null;
   }
}

public class RoundedShapeFactory extends AbstractFactory {
   @Override
   public Shape getShape(String shapeType){    
      if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new RoundedRectangle();         
      }else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new RoundedSquare();
      }  
      return null;
   }
}

5、創建工廠生成類FactoryProducer

public class FactoryProducer {
   public static AbstractFactory getFactory(boolean rounded){   
      if(rounded){
         return new RoundedShapeFactory();         
      }else{
         return new ShapeFactory();
      }
   }
}　　

6、測試

public class AbstractFactoryPatternDemo {
   public static void main(String[] args) {
      //get shape factory
      AbstractFactory shapeFactory = FactoryProducer.getFactory(false);
      //get an object of Shape Rectangle
      Shape shape1 = shapeFactory.getShape("RECTANGLE");
      //call draw method of Shape Rectangle
      shape1.draw();
      //get an object of Shape Square 
      Shape shape2 = shapeFactory.getShape("SQUARE");
      //call draw method of Shape Square
      shape2.draw();
      //get shape factory
      AbstractFactory shapeFactory1 = FactoryProducer.getFactory(true);
      //get an object of Shape Rectangle
      Shape shape3 = shapeFactory1.getShape("RECTANGLE");
      //call draw method of Shape Rectangle
      shape3.draw();
      //get an object of Shape Square 
      Shape shape4 = shapeFactory1.getShape("SQUARE");
      //call draw method of Shape Square
      shape4.draw();
      
   }
}

7、結果

Inside Rectangle::draw() method.
Inside Square::draw() method.
Inside RoundedRectangle::draw() method.
Inside RoundedSquare::draw() method.