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-method/README.md

@@ -7,7 +7,7 @@ categories: Creational
 language: en
 tags:
  - Extensibility
- - Gang Of Four
+ - Gang of Four
 ---
 
 ## Also known as
@@ -21,7 +21,7 @@ Factory Method lets a class defer instantiation to subclasses.
 
 ## Explanation
 
-Real world example
+Real-world example
 
 > Blacksmith manufactures weapons. Elves require Elvish weapons and orcs require Orcish weapons. 
 > Depending on the customer at hand the right type of blacksmith is summoned.
@@ -40,7 +40,7 @@ Wikipedia says
 
  **Programmatic Example**
 
-Taking our blacksmith example above. First of all we have a `Blacksmith` interface and some 
+Taking our blacksmith example above. First of all, we have a `Blacksmith` interface and some 
 implementations for it:
 
 ```java
@@ -65,15 +65,25 @@ When the customers come, the correct type of blacksmith is summoned and requeste
 manufactured:
 
 ```java
-var blacksmith = new ElfBlacksmith();
-blacksmith.manufactureWeapon(WeaponType.SPEAR);
-blacksmith.manufactureWeapon(WeaponType.AXE);
+Blacksmith blacksmith = new OrcBlacksmith();
+Weapon weapon = blacksmith.manufactureWeapon(WeaponType.SPEAR);
+LOGGER.info("{} manufactured {}", blacksmith, weapon);
+weapon = blacksmith.manufactureWeapon(WeaponType.AXE);
+LOGGER.info("{} manufactured {}", blacksmith, weapon);
+
+blacksmith = new ElfBlacksmith();
+weapon = blacksmith.manufactureWeapon(WeaponType.SPEAR);
+LOGGER.info("{} manufactured {}", blacksmith, weapon);
+weapon = blacksmith.manufactureWeapon(WeaponType.AXE);
+LOGGER.info("{} manufactured {}", blacksmith, weapon);
 ```
 
 Program output:
-```java
-// Elven spear
-// Elven axe
+```
+The orc blacksmith manufactured an orcish spear
+The orc blacksmith manufactured an orcish axe
+The elf blacksmith manufactured an elven spear
+The elf blacksmith manufactured an elven axe
 ```
 
 ## Class diagram
@@ -89,7 +99,7 @@ Use the Factory Method pattern when:
 * Classes delegate responsibility to one of several helper subclasses, and you want to localize the 
 knowledge of which helper subclass is the delegate.
 
-## Real world examples
+## Known uses
 
 * [java.util.Calendar](http://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html#getInstance--)
 * [java.util.ResourceBundle](http://docs.oracle.com/javase/8/docs/api/java/util/ResourceBundle.html#getBundle-java.lang.String-)

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

@@ -26,7 +26,7 @@ package com.iluwatar.factory.method;
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * The Factory Method is a creational design pattern which uses factory methods to deal with the
+ * The Factory Method is a creational design pattern that uses factory methods to deal with the
  * problem of creating objects without specifying the exact class of object that will be created.
  * This is done by creating objects via calling a factory method either specified in an interface
  * and implemented by child classes, or implemented in a base class and optionally overridden by
@@ -41,39 +41,22 @@ import lombok.extern.slf4j.Slf4j;
 @Slf4j
 public class App {
 
-  private final Blacksmith blacksmith;
-
-  /**
-   * Creates an instance of <code>App</code> which will use <code>blacksmith</code> to manufacture 
-   * the weapons for war.
-   * <code>App</code> is unaware which concrete implementation of {@link Blacksmith} it is using.
-   * The decision of which blacksmith implementation to use may depend on configuration, or
-   * the type of rival in war.
-   * @param blacksmith a non-null implementation of blacksmith
-   */
-  public App(Blacksmith blacksmith) {
-    this.blacksmith = blacksmith;
-  }
-
   /**
    * Program entry point.
-   *
    * @param args command line args
    */
   public static void main(String[] args) {
-    // Lets go to war with Orc weapons
-    var app = new App(new OrcBlacksmith());
-    app.manufactureWeapons();
 
-    // Lets go to war with Elf weapons
-    app = new App(new ElfBlacksmith());
-    app.manufactureWeapons();
-  }
-
-  private void manufactureWeapons() {
-    var weapon = blacksmith.manufactureWeapon(WeaponType.SPEAR);
-    LOGGER.info(weapon.toString());
+    Blacksmith blacksmith = new OrcBlacksmith();
+    Weapon weapon = blacksmith.manufactureWeapon(WeaponType.SPEAR);
+    LOGGER.info("{} manufactured {}", blacksmith, weapon);
     weapon = blacksmith.manufactureWeapon(WeaponType.AXE);
-    LOGGER.info(weapon.toString());
+    LOGGER.info("{} manufactured {}", blacksmith, weapon);
+
+    blacksmith = new ElfBlacksmith();
+    weapon = blacksmith.manufactureWeapon(WeaponType.SPEAR);
+    LOGGER.info("{} manufactured {}", blacksmith, weapon);
+    weapon = blacksmith.manufactureWeapon(WeaponType.AXE);
+    LOGGER.info("{} manufactured {}", blacksmith, weapon);
   }
 }

factory-method/src/main/java/com/iluwatar/factory/method/ElfBlacksmith.java

@@ -44,4 +44,8 @@ public class ElfBlacksmith implements Blacksmith {
     return ELFARSENAL.get(weaponType);
   }
 
+  @Override
+  public String toString() {
+    return "The elf blacksmith";
+  }
 }

factory-method/src/main/java/com/iluwatar/factory/method/ElfWeapon.java

@@ -37,6 +37,6 @@ public class ElfWeapon implements Weapon {
 
   @Override
   public String toString() {
-    return "Elven " + weaponType;
+    return "an elven " + weaponType;
   }
 }

factory-method/src/main/java/com/iluwatar/factory/method/OrcBlacksmith.java

@@ -43,4 +43,9 @@ public class OrcBlacksmith implements Blacksmith {
   public Weapon manufactureWeapon(WeaponType weaponType) {
     return ORCARSENAL.get(weaponType);
   }
+
+  @Override
+  public String toString() {
+    return "The orc blacksmith";
+  }
 }

factory-method/src/main/java/com/iluwatar/factory/method/OrcWeapon.java

@@ -37,6 +37,6 @@ public class OrcWeapon implements Weapon {
 
   @Override
   public String toString() {
-    return "Orcish " + weaponType;
+    return "an orcish " + weaponType;
   }
 }