Java设计模式——工厂模式

工厂模式是我们常用到的一种设计模式，它是一种创建模式。使用工厂模式的时候，我们不需要公开创建了对象的细节，只需要提供接口即可。

下面以一个例子说明。创建Shape接口以及它的实现类（Circle、Square、Rectangle），通过ShapeFactory类获取需要的实例。

1、创建接口Shape

public interface Shape {
   void draw();
}

2、创建实现类Circle、Square、Rectangle　

//  Rectangle
public class Rectangle implements Shape {

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

//  Square
public class Square implements Shape {

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

//  Circle
public class Circle implements Shape {

   @Override
   public void draw() {
      System.out.println("Inside Circle::draw() method.");
   }
}

3、创建ShapeFactory类（工厂类）

public class ShapeFactory {
	
   //use getShape method to get object of type shape 
   public Shape getShape(String shapeType){
      if(shapeType == null){
         return null;
      }		
      if(shapeType.equalsIgnoreCase("CIRCLE")){
         return new Circle();
         
      } else if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();
         
      } else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }
      
      return null;
   }
}

4、其他客户端FactoryPatternDemo，通过ShapeFactory，传递正确的参数，得到相应的实例

public class FactoryPatternDemo {

   public static void main(String[] args) {
      ShapeFactory shapeFactory = new ShapeFactory();

      //get an object of Circle and call its draw method.
      Shape shape1 = shapeFactory.getShape("CIRCLE");

      //call draw method of Circle
      shape1.draw();

      //get an object of Rectangle and call its draw method.
      Shape shape2 = shapeFactory.getShape("RECTANGLE");

      //call draw method of Rectangle
      shape2.draw();

      //get an object of Square and call its draw method.
      Shape shape3 = shapeFactory.getShape("SQUARE");

      //call draw method of square
      shape3.draw();
   }
}

5、测试结果

Inside Circle::draw() method.
Inside Rectangle::draw() method.
Inside Square::draw() method.