Update factory example

iluwatar · iluwatar · commit 588b106ada38 · 2021-06-13T10:50:29.000+03:00
diff --git a/factory/README.md b/factory/README.md
@@ -16,16 +16,17 @@ tags:
 
 ## Intent
 
-Providing a static method encapsulated in a class called factory, in order to hide the 
-implementation logic and makes client code focus on usage rather then initialization new objects.
+Providing a static method encapsulated in a class called the factory, to hide the implementation 
+logic and make client code focus on usage rather than initializing new objects.
 
 ## Explanation
 
-Real world example
+Real-world example
 
-> Lets say we have a web application connected to SQLServer, but now we want to switch to Oracle. To 
-> do so without modifying existing source code, we need to implements Simple Factory pattern, in 
-> which a static method can be invoked to create connection to a given database.
+> Imagine an alchemist who is about to manufacture coins. The alchemist must be able to create both 
+> gold and copper coins and switching between them must be possible without modifying the existing 
+> source code. The factory pattern makes it possible by providing a static construction method which 
+> can be called with relevant parameters.
 
 Wikipedia says
 
@@ -34,26 +35,26 @@ Wikipedia says
 
 **Programmatic Example**
 
-We have an interface `Car` and two implementations `Ford` and `Ferrari`.
+We have an interface `Coin` and two implementations `GoldCoin` and `CopperCoin`.
 
 ```java
-public interface Car {
+public interface Coin {
   String getDescription();
 }
 
-public class Ford implements Car {
+public class GoldCoin implements Coin {
 
-  static final String DESCRIPTION = "This is Ford.";
+  static final String DESCRIPTION = "This is a gold coin.";
 
   @Override
   public String getDescription() {
     return DESCRIPTION;
   }
 }
 
-public class Ferrari implements Car {
+public class CopperCoin implements Coin {
    
-  static final String DESCRIPTION = "This is Ferrari.";
+  static final String DESCRIPTION = "This is a copper coin.";
 
   @Override
   public String getDescription() {
@@ -62,51 +63,48 @@ public class Ferrari implements Car {
 }
 ```
 
-Enumeration above represents types of cars that we support (`Ford` and `Ferrari`).
+Enumeration above represents types of coins that we support (`GoldCoin` and `CopperCoin`).
 
 ```java
-public enum CarType {
-  
-  FORD(Ford::new), 
-  FERRARI(Ferrari::new);
-  
-  private final Supplier<Car> constructor; 
-  
-  CarType(Supplier<Car> constructor) {
-    this.constructor = constructor;
-  }
-  
-  public Supplier<Car> getConstructor() {
-    return this.constructor;
-  }
+@RequiredArgsConstructor
+@Getter
+public enum CoinType {
+
+  COPPER(CopperCoin::new),
+  GOLD(GoldCoin::new);
+
+  private final Supplier<Coin> constructor;
 }
 ```
-Then we have the static method `getCar` to create car objects encapsulated in the factory class 
-`CarsFactory`.
+
+Then we have the static method `getCoin` to create coin objects encapsulated in the factory class 
+`CoinFactory`.
 
 ```java
-public class CarsFactory {
-  
-  public static Car getCar(CarType type) {
+public class CoinFactory {
+
+  public static Coin getCoin(CoinType type) {
     return type.getConstructor().get();
   }
 }
 ```
 
-Now on the client code we can create different types of cars using the factory class.
+Now on the client code we can create different types of coins using the factory class.
 
 ```java
-var car1 = CarsFactory.getCar(CarType.FORD);
-var car2 = CarsFactory.getCar(CarType.FERRARI);
-LOGGER.info(car1.getDescription());
-LOGGER.info(car2.getDescription());
+LOGGER.info("The alchemist begins his work.");
+var coin1 = CoinFactory.getCoin(CoinType.COPPER);
+var coin2 = CoinFactory.getCoin(CoinType.GOLD);
+LOGGER.info(coin1.getDescription());
+LOGGER.info(coin2.getDescription());
 ```
 
 Program output:
 
 ```java
-This is Ford.
-This is Ferrari.
+The alchemist begins his work.
+This is a copper coin.
+This is a gold coin.
 ```
 
 ## Class Diagram
@@ -115,7 +113,7 @@ This is Ferrari.
 
 ## Applicability
 
-Use the Simple Factory pattern when you only care about the creation of a object, not how to create 
+Use the factory pattern when you only care about the creation of a object, not how to create 
 and manage it.
 
 Pros
@@ -127,13 +125,13 @@ Cons
 
 * The code becomes more complicated than it should be. 
 
-## Real world examples
+## Known uses
 
 * [java.util.Calendar#getInstance()](https://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html#getInstance--)
 * [java.util.ResourceBundle#getBundle()](https://docs.oracle.com/javase/8/docs/api/java/util/ResourceBundle.html#getBundle-java.lang.String-)
 * [java.text.NumberFormat#getInstance()](https://docs.oracle.com/javase/8/docs/api/java/text/NumberFormat.html#getInstance--)
 * [java.nio.charset.Charset#forName()](https://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html#forName-java.lang.String-)
-* [java.net.URLStreamHandlerFactory#createURLStreamHandler(String)](https://docs.oracle.com/javase/8/docs/api/java/net/URLStreamHandlerFactory.html) (Returns different singleton objects, depending on a protocol)
+* [java.net.URLStreamHandlerFactory#createURLStreamHandler(String)](https://docs.oracle.com/javase/8/docs/api/java/net/URLStreamHandlerFactory.html) (returns different singleton objects, depending on a protocol)
 * [java.util.EnumSet#of()](https://docs.oracle.com/javase/8/docs/api/java/util/EnumSet.html#of(E))
 * [javax.xml.bind.JAXBContext#createMarshaller()](https://docs.oracle.com/javase/8/docs/api/javax/xml/bind/JAXBContext.html#createMarshaller--) and other similar methods.
 
diff --git a/factory/etc/factory.urm.png b/factory/etc/factory.urm.png
diff --git a/factory/etc/factory.urm.puml b/factory/etc/factory.urm.puml
@@ -5,31 +5,32 @@ package com.iluwatar.factory {
     + App()
     + main(args : String[]) {static}
   }
-  interface Car {
+  interface Coin {
     + getDescription() : String {abstract}
   }
-  class CarsFactory {
-    + CarsFactory()
-    + getCar(type : CarType) : Car {static}
+  class CoinFactory {
+    + CoinFactory()
+    + getCoin(type : CoinType) : Coin {static}
   }
-  ~enum CarType {
-    + FERRARI {static}
-    + FORD {static}
-    + valueOf(name : String) : CarType {static}
-    + values() : CarType[] {static}
+  enum CoinType {
+    + COPPER {static}
+    + GOLD {static}
+    - constructor : Supplier<Coin>
+    + getConstructor() : Supplier<Coin>
+    + valueOf(name : String) : CoinType {static}
+    + values() : CoinType[] {static}
   }
-  class Ferrari {
+  class CopperCoin {
     ~ DESCRIPTION : String {static}
-    + Ferrari()
+    + CopperCoin()
     + getDescription() : String
   }
-  class Ford {
+  class GoldCoin {
     ~ DESCRIPTION : String {static}
-    + Ford()
+    + GoldCoin()
     + getDescription() : String
   }
 }
-CarType ..+ CarsFactory
-Ferrari ..|> Car 
-Ford ..|> Car 
+CopperCoin ..|> Coin 
+GoldCoin ..|> Coin 
 @enduml
diff --git a/factory/src/main/java/com/iluwatar/factory/App.java b/factory/src/main/java/com/iluwatar/factory/App.java
@@ -30,8 +30,8 @@
  * create and return objects of varying classes, in order to hide the implementation logic 
  * and makes client code focus on usage rather then objects initialization and management.
  *
- * <p>In this example the CarFactory is the factory class and it provides a static method to 
- * create different cars.
+ * <p>In this example an alchemist manufactures coins. CoinFactory is the factory class and it
+ * provides a static method to create different types of coins.
  */
 
 @Slf4j
@@ -41,9 +41,10 @@ public class App {
    * Program main entry point.
    */
   public static void main(String[] args) {
-    var car1 = CarsFactory.getCar(CarType.FORD);
-    var car2 = CarsFactory.getCar(CarType.FERRARI);
-    LOGGER.info(car1.getDescription());
-    LOGGER.info(car2.getDescription());
+    LOGGER.info("The alchemist begins his work.");
+    var coin1 = CoinFactory.getCoin(CoinType.COPPER);
+    var coin2 = CoinFactory.getCoin(CoinType.GOLD);
+    LOGGER.info(coin1.getDescription());
+    LOGGER.info(coin2.getDescription());
   }
 }
diff --git a/factory/src/main/java/com/iluwatar/factory/Coin.java b/factory/src/main/java/com/iluwatar/factory/Coin.java
@@ -24,9 +24,9 @@
 package com.iluwatar.factory;
 
 /**
- * Car interface.
+ * Coin interface.
  */
-public interface Car {
+public interface Coin {
 
   String getDescription();
 
diff --git a/factory/src/main/java/com/iluwatar/factory/CoinFactory.java b/factory/src/main/java/com/iluwatar/factory/CoinFactory.java
@@ -24,14 +24,14 @@
 package com.iluwatar.factory;
 
 /**
- * Factory of cars.
+ * Factory of coins.
  */
-public class CarsFactory {
+public class CoinFactory {
 
   /**
-   * Factory method takes as parameter a car type and initiate the appropriate class.
+   * Factory method takes as a parameter the coin type and calls the appropriate class.
    */
-  public static Car getCar(CarType type) {
+  public static Coin getCoin(CoinType type) {
     return type.getConstructor().get();
   }
 }
diff --git a/factory/src/main/java/com/iluwatar/factory/CoinType.java b/factory/src/main/java/com/iluwatar/factory/CoinType.java
@@ -28,15 +28,14 @@
 import lombok.RequiredArgsConstructor;
 
 /**
- * Enumeration for different types of cars.
+ * Enumeration for different types of coins.
  */
 @RequiredArgsConstructor
 @Getter
-public enum CarType {
+public enum CoinType {
 
-  FORD(Ford::new),
-  FERRARI(Ferrari::new);
-
-  private final Supplier<Car> constructor;
+  COPPER(CopperCoin::new),
+  GOLD(GoldCoin::new);
 
+  private final Supplier<Coin> constructor;
 }
diff --git a/factory/src/main/java/com/iluwatar/factory/CopperCoin.java b/factory/src/main/java/com/iluwatar/factory/CopperCoin.java
@@ -24,11 +24,11 @@
 package com.iluwatar.factory;
 
 /**
- * Ferrari implementation.
+ * CopperCoin implementation.
  */
-public class Ferrari implements Car {
+public class CopperCoin implements Coin {
 
-  static final String DESCRIPTION = "This is Ferrari.";
+  static final String DESCRIPTION = "This is a copper coin.";
 
   @Override
   public String getDescription() {
diff --git a/factory/src/main/java/com/iluwatar/factory/GoldCoin.java b/factory/src/main/java/com/iluwatar/factory/GoldCoin.java
@@ -24,11 +24,11 @@
 package com.iluwatar.factory;
 
 /**
- * Ford implementation.
+ * GoldCoin implementation.
  */
-public class Ford implements Car {
+public class GoldCoin implements Coin {
 
-  static final String DESCRIPTION = "This is Ford.";
+  static final String DESCRIPTION = "This is a gold coin.";
 
   @Override
   public String getDescription() {
diff --git a/factory/src/test/java/com/iluwatar/factory/CoinFactoryTest.java b/factory/src/test/java/com/iluwatar/factory/CoinFactoryTest.java
@@ -27,12 +27,11 @@
 
 import org.junit.jupiter.api.Test;
 
-class CarsFactoryTest {
+class CoinFactoryTest {
 
   @Test
-  void shouldReturnFerrariInstance() {
-    final var ferrari = CarsFactory.getCar(CarType.FERRARI);
-    assertTrue(ferrari instanceof Ferrari);
+  void shouldReturnGoldCoinInstance() {
+    final var goldCoin = CoinFactory.getCoin(CoinType.GOLD);
+    assertTrue(goldCoin instanceof GoldCoin);
   }
-
 }

Original file line number	Diff line number	Diff line change
`@@ -27,12 +27,11 @@`
`27`	`27`
`28`	`28`	`import org.junit.jupiter.api.Test;`
`29`	`29`
`30`		`-class CarsFactoryTest {`
	`30`	`+class CoinFactoryTest {`
`31`	`31`
`32`	`32`	`@Test`
`33`		`- void shouldReturnFerrariInstance() {`
`34`		`- final var ferrari = CarsFactory.getCar(CarType.FERRARI);`
`35`		`- assertTrue(ferrari instanceof Ferrari);`
	`33`	`+ void shouldReturnGoldCoinInstance() {`
	`34`	`+ final var goldCoin = CoinFactory.getCoin(CoinType.GOLD);`
	`35`	`+ assertTrue(goldCoin instanceof GoldCoin);`
`36`	`36`	`}`
`37`		`-`
`38`	`37`	`}`