factory pattern

Author: urbytes21

content/posts/java-design-pattern.md

@@ -0,0 +1,122 @@
+---
+author: "Phong Nguyen"
+title: "Design Patterns"
+date: "2025-02-11"
+description: "Design Patterns."
+tags: ["java"]   #tags search
+FAcategories: ["syntax"]    #The category of the post, similar to tags but usually for broader classification.
+FAseries: ["Themes Guide"]    #indicates that this post is part of a series of related posts
+aliases: ["migrate-from-jekyl"]    #Alternative URLs or paths that can be used to access this post, useful for redirects from old posts or similar content.
+ShowToc: true    # Determines whether to display the Table of Contents (TOC) for the post.
+TocOpen: true    # Controls whether the TOC is expanded when the post is loaded. 
+weight: 11    # The order in which the post appears in a list of posts. Lower numbers make the post appear earlier.
+---
+Explain how to use the design patterns.
+[Refer1](https://github.com/kamranahmedse/design-patterns-for-humans?tab=readme-ov-file#-simple-factory)
+[Refer2](https://java-design-patterns.com/)
+[Refer3](https://www.tutorialspoint.com/design_pattern/factory_pattern.htm)<br>
+## 1. 🏠 Simple Factory
+- Factory is an object for creating other objects 
+- **Use cases:**
+  - when the class does not know beforehand the exact types and dependencies of the objects it needs to create.
+  - When a method returns one of several possible classes that share a common super class and wants to encapsulate the logic of which object to create.
+  - when designing frameworks or libraries to give the best flexibility and isolation from concrete class types
+
+- **Examples:** You want to manufacture the products. You must be able to create both A and B (C,D) products and switch between them without modify the existing source codes.
+  -  Design UML:
+![image](/images/factory_pattern.png)
+ 
+  - Implementation codes:
+
+```java
+package design.patterns.factory;
+
+public interface IProduct {
+	public void getType();
+}
+
+package design.patterns.factory;
+
+public class ProductA implements IProduct {
+	private static String TYPE_NAME = "ProductA";
+	@Override
+	public void getType() {
+		System.err.println(TYPE_NAME);
+	}
+
+}
+
+package design.patterns.factory;
+
+public class ProductB implements IProduct {
+	private static String TYPE_NAME = "ProductB";
+	@Override
+	public void getType() {
+		System.err.println(TYPE_NAME);
+	}
+}
+
+package design.patterns.factory;
+
+public class ProductC implements IProduct {
+	private static String TYPE_NAME = "ProductC";
+	@Override
+	public void getType() {
+		System.err.println(TYPE_NAME);
+	}
+
+}
+
+package design.patterns.factory;
+
+public enum ProductType {
+	TYPEA,
+	TYPEB,
+	TYPEC;
+}
+
+package design.patterns.factory;
+
+public class ProductFactory {
+	public static IProduct createProduct(ProductType type) {
+		if (type == null) {
+			return null;
+		}
+
+		switch (type) {
+		case TYPEA: {
+			return new ProductA();
+		}
+		case TYPEB: {
+			return new ProductB();
+		}
+		case TYPEC: {
+			return new ProductC();
+		}
+		}
+		return null;
+	}
+}
+
+package design.patterns.factory;
+
+public class MainTestFactory {
+
+	public static void main(String[] args) {
+		ProductFactory productFactory = new ProductFactory();
+		
+		IProduct product1 = productFactory.createProduct(ProductType.TYPEA);
+		product1.getType();
+		
+		IProduct product2 = productFactory.createProduct(ProductType.TYPEB);
+		product2.getType();
+		
+		IProduct product3 = productFactory.createProduct(ProductType.TYPEC);
+		product3.getType();
+				
+	}
+
+}
+
+
+```