task: Explanations and grammar fixes for all the GoF patterns (#1791)

* Grammatical fixes to command pattern

* Update bridge pattern readme

* Fixes to builder pattern grammar

* Update chain of responsibility

* Improvements to the composite example

* Fixes to headings

* Minor updates to decorator pattern

* Update facade

* Update factory example

* Update factory method

* Update flyweight

* Interpreter explanation

* Update iterator readme

* Add explanation for mediator pattern

* Grammatical fixes to memento

* Grammar fixes for observer

* Update explanation for the prototype pattern

* Proxy pattern grammar fixes

* Update singleton

* Grammar fixes to state pattern

* Grammar fixes for strategy

* Grammar fixes, template method

* Grammar fixes for visitor

* Fix typo

factory/src/main/java/com/iluwatar/factory/App.java

@@ -30,8 +30,8 @@ import lombok.extern.slf4j.Slf4j;
  * 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());
   }
 }

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();
 

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();
   }
 }

factory/src/main/java/com/iluwatar/factory/CoinType.java

@@ -28,15 +28,14 @@ import lombok.Getter;
 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;
 }

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() {

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() {

factory/src/test/java/com/iluwatar/factory/CoinFactoryTest.java

@@ -27,12 +27,11 @@ import static org.junit.jupiter.api.Assertions.*;
 
 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);
   }
-
 }