工厂设计模式

Posted 2020-10-19 大明湖畔的守望者

先通过例子理解一下

第1步：创建一个接口

Shape.java

1 public interface Shape {
2    void draw();
3 }

第2步：创建几个实现类

Rectangle.java

1 public class Rectangle implements Shape {
2 
3    @Override
4    public void draw() {
5       System.out.println("Inside Rectangle::draw() method.");
6    }
7 }

Square.java

1 public class Square implements Shape {
2 
3    @Override
4    public void draw() {
5       System.out.println("Inside Square::draw() method.");
6    }
7 }

Circle.java

1 public class Circle implements Shape {
2 
3    @Override
4    public void draw() {
5       System.out.println("Inside Circle::draw() method.");
6    }
7 }

第3步：创建工厂根据给定的信息生成具体类的对象

ShapeFactory.java

 1 public class ShapeFactory {
 2 
 3    //use getShape method to get object of type shape 
 4    public Shape getShape(String shapeType){
 5       if(shapeType == null){
 6          return null;
 7       }        
 8       if(shapeType.equalsIgnoreCase("CIRCLE")){
 9          return new Circle();
10 
11       } else if(shapeType.equalsIgnoreCase("RECTANGLE")){
12          return new Rectangle();
13 
14       } else if(shapeType.equalsIgnoreCase("SQUARE")){
15          return new Square();
16       }
17 
18       return null;
19    }
20 }

第4步：演示使用工厂通过传递类型等信息来获取具体类的对象

FactoryPatternDemo.java

 1 public class FactoryPatternDemo {
 2 
 3    public static void main(String[] args) {
 4       ShapeFactory shapeFactory = new ShapeFactory();
 5 
 6       //get an object of Circle and call its draw method.
 7       Shape shape1 = shapeFactory.getShape("CIRCLE");
 8 
 9       //call draw method of Circle
10       shape1.draw();
11 
12       //get an object of Rectangle and call its draw method.
13       Shape shape2 = shapeFactory.getShape("RECTANGLE");
14 
15       //call draw method of Rectangle
16       shape2.draw();
17 
18       //get an object of Square and call its draw method.
19       Shape shape3 = shapeFactory.getShape("SQUARE");
20 
21       //call draw method of circle
22       shape3.draw();
23    }
24 }

第5步：验证输出结果

验证输出结果如下：

1 Inside Circle::draw() method.
2 Inside Rectangle::draw() method.
3 Inside Square::draw() method.