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工厂模式是Java中最常用的设计模式之一。这种类型的设计模式属于创建模式,因为此模式提供了创建对象的最佳方法之一。
在Factory模式中,我们创建对象而不将创建逻辑暴露给客户端,并使用公共接口引用新创建的对象。
履行
我们将创建一个Shape接口和实现Shape接口的具体类。工厂类ShapeFactory被定义为下一步。
FactoryPatternDemo,我们的演示类将使用ShapeFactory来获取Shape对象。它会将信息(CIRCLE / RECTANGLE / SQUARE)传递给ShapeFactory以获取所需的对象类型。
![工厂模式UML图](https://www.tutorialspoint.com/design_pattern/images/factory_pattern_uml_diagram.jpg)
步骤1
创建一个界面。
Shape.java
public interface Shape { void draw(); }
第2步
创建实现相同接口的具体类。
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."); } }
第3步
创建工厂以根据给定信息生成具体类的对象。
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; } }
步骤4
使用Factory通过传递类型等信息来获取具体类的对象。
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 square shape3.draw(); } }
第5步
验证输出。
Inside Circle::draw() method. Inside Rectangle::draw() method. Inside Square::draw() method.