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工厂模式是Java中最常用的设计模式。工厂模式提供很好的创建对象的方式，属于创建型模式。
使用工厂模式创建对象是不向使用者暴露创建细节，并且可以通过统一的接口引用对象。
我们将创建Shape接口和实现Shape接口的具体类。下一步再声明工厂类ShapeFactory。
示例类FactoryPatternDemo使用ShapeFactory获取Shape对象。通过给ShapeFactory传递图形参数(CIRCLE / RECTANGLE / SQUARE)来获取需要的对象。
创建一个接口
Shape.java
public interface Shape { void draw(); }
创建实现Shape接口的具体类
Rectangle.java
public class Rectangle implements Shape { @Override public void draw() { System.out.println("Inside Rectangle::draw() method."); } }
Square.java
public class Square implements Shape { @Override public void draw() { System.out.println("Inside Square::draw() method."); } }
Circle.java
public class Circle implements Shape { @Override public void draw() { System.out.println("Inside Circle::draw() method."); } }
创建工厂类，工厂类可以根据传入参数创建具体类的实例。
ShapeFactory.java
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; } }
通过工厂类创建具体类的实例。
FactoryPatternDemo.java
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 circle shape3.draw(); } }
验证输出
Inside Circle::draw() method.
Inside Rectangle::draw() method.
Inside Square::draw() method.
本文翻译自 http://www.tutorialspoint.com/design_pattern/factory_pattern.htm
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原文地址：http://www.cnblogs.com/lin-xuan/p/5483417.html
