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Today, I would like to share with you how to use Java code to achieve factory method pattern related knowledge, detailed content, clear logic, I believe that most people still know too much about this knowledge, so share this article for your reference, I hope you have something to gain after reading this article, let's take a look at it.

1. Introduction of factory method model

Definition: the factory method pattern is a further abstraction of the simple factory pattern. The advantage is that it enables the system to introduce new products without modifying the original code, that is, to meet the opening and closing principle. Define an object interface to create and let the subclass decide which class to instantiate, delaying the instantiation of a class to the subclass.

two。 Factory method pattern class diagram UML

3. Factory method pattern role description

Abstract factory (AbstractFactory): provides an interface to create a product through which the caller accesses the factory method of the concrete factory to create the product

Concrete factory (ConcreteFactory): implements the method of abstract factory definition and completes the creation of concrete products.

Abstract product (Product): defines the specification of the product and describes the main features and performance of the product

ConcreteProduct: a method that implements the definition of an abstract product. There are specific factories to create products, and specific factories correspond to specific products one by one.

4. Code implementation

Factory method pattern implementation:

/ * Abstract factory: provide common methods for specific factories * / public interface Product {public void show ();} public class ConcreteProduct1 implements Product {@ Override public void show () {System.out.println ("concrete product 1 presentation...");}} public class ConcreateProduct2 implements Product {@ Override public void show () {System.out.println ("concrete product 2 presentation...") }} / * Abstract factory * / public interface AbstractFactory {public Product createProduct ();} / * concrete factory 1 produces concrete products 1 * / public class ConcreteFactory1 implements AbstractFactory {@ Override public Product createProduct () {ConcreteProduct1 concreteProduct1 = new ConcreteProduct1 (); System.out.println ("concrete factory 1 creates concrete products 1."); return concreteProduct1 } public class ConcreteFactory2 implements AbstractFactory {@ Override public Product createProduct () {System.out.println ("specific factory 2 produces specific products 2..."); return new ConcreateProduct2 ();}}

Call method:

/ / get specific product 1 Product product = new ConcreteFactory1 () .createProduct (); product.show (); Product product1 = new ConcreteFactory2 () .createProduct (); product1.show ()

Steps to use:

Create abstract product classes and define public methods for products

Create a concrete product class (implement an abstract product interface) and define the generated concrete product

Create an abstract factory class that defines the public interface of a concrete factory

Create a specific factory class and define the method for creating a specific product instance

The caller calls the method of a specific factory class to create instances of different specific products.

5. Re-exploration of Factory Model

Solve the problem: solve the simple factory class new products need to modify the factory class method logic problem, that is, do not open and close the principle.

Exit the creation of specific products to the subclass of the factory class (specific factory). At this time, the factory class is no longer responsible for the creation of all products, but gives the interfaces that the specific factory must implement, so that when adding new products, the factory method does not need to modify the logic of the factory class, but adds a new factory subclass, which conforms to the opening and closing principle.

6. Advantages and disadvantages

Advantages:

Strong flexibility, for the creation of new products, only need to write one more corresponding factory class

Users only need to guide the name of the factory to get the desired product, and there is no need to guide the specific product creation process.

Disadvantages:

It is easy to have too many classes, which increases the complexity.

Each factory can only produce one product, and the secondary malpractice can be solved by using abstract factory pattern.

7. Application scenario

Customers only focus on the name of the factory that created the product, and do not need to know the specific product name.

These are all the contents of the article "how to implement the factory method pattern in Java code". Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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