Java 设计模式——工场模式（Factory method）

工场模式：通过一个公共接口来将 对象的创建逻辑与用户分离。

例子：

创建一个ShapeFactory获得不同的Shape对象（Circle，Rectangle，Square）

第一步：创建接口Shape.java

public interface Shape {void draw();}

第二步：创建具体的类来实现接口

Rectangle.java

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

Rectangle.java

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

Circle.java

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

第三步：创建工场类ShapeFactory.java，根据用户传入的信息获得对应的类的实例

public class ShapeFactory {public Shape getShape(String shapeType){if(shapeType == null){return null;}if(shapeType.equalsIgnoreCase("CIRCLE")){return new Circle();}if(shapeType.equalsIgnoreCase("RECTANGLE")){return new Rectangle();}if(shapeType.equalsIgnoreCase("SQUARE")){return new Square();}return null;}}

第四步：使用工场类测试 FactoryPatternDemo.java

public class FactoryPatternDemo {public static void main(String[] args) {ShapeFactory shapeFactory = new ShapeFactory();Shape shape1 = shapeFactory.getShape("CIRCLE");shape1.draw();Shape shape2 = shapeFactory.getShape("RECTANGLE");shape2.draw();Shape shape3 = shapeFactory.getShape("SQUARE");shape3.draw();}}

输出结果：

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