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

flyweight/README.md

@@ -6,7 +6,7 @@ permalink: /patterns/flyweight/
 categories: Structural
 language: en
 tags:
- - Gang Of Four
+ - Gang of Four
  - Performance
 ---
 
@@ -16,11 +16,11 @@ Use sharing to support large numbers of fine-grained objects efficiently.
 
 ## Explanation
 
-Real world example
+Real-world example
 
 > Alchemist's shop has shelves full of magic potions. Many of the potions are the same so there is 
-> no need to create new object for each of them. Instead one object instance can represent multiple 
-> shelf items so memory footprint remains small.
+> no need to create a new object for each of them. Instead, one object instance can represent 
+> multiple shelf items so the memory footprint remains small.
 
 In plain words
 
@@ -36,7 +36,7 @@ Wikipedia says
 
 **Programmatic example**
 
-Translating our alchemist shop example from above. First of all we have different potion types:
+Translating our alchemist shop example from above. First of all, we have different potion types:
 
 ```java
 public interface Potion {
@@ -104,27 +104,81 @@ public class PotionFactory {
 }
 ```
 
-And it can be used as below:
+`AlchemistShop` contains two shelves of magic potions. The potions are created using the
+aforementioned `PotionFactory`.
 
 ```java
-var factory = new PotionFactory();
-factory.createPotion(PotionType.INVISIBILITY).drink(); // You become invisible. (Potion=6566818)
-factory.createPotion(PotionType.HEALING).drink(); // You feel healed. (Potion=648129364)
-factory.createPotion(PotionType.INVISIBILITY).drink(); // You become invisible. (Potion=6566818)
-factory.createPotion(PotionType.HOLY_WATER).drink(); // You feel blessed. (Potion=1104106489)
-factory.createPotion(PotionType.HOLY_WATER).drink(); // You feel blessed. (Potion=1104106489)
-factory.createPotion(PotionType.HEALING).drink(); // You feel healed. (Potion=648129364)
+@Slf4j
+public class AlchemistShop {
+
+  private final List<Potion> topShelf;
+  private final List<Potion> bottomShelf;
+
+  public AlchemistShop() {
+    var factory = new PotionFactory();
+    topShelf = List.of(
+        factory.createPotion(PotionType.INVISIBILITY),
+        factory.createPotion(PotionType.INVISIBILITY),
+        factory.createPotion(PotionType.STRENGTH),
+        factory.createPotion(PotionType.HEALING),
+        factory.createPotion(PotionType.INVISIBILITY),
+        factory.createPotion(PotionType.STRENGTH),
+        factory.createPotion(PotionType.HEALING),
+        factory.createPotion(PotionType.HEALING)
+    );
+    bottomShelf = List.of(
+        factory.createPotion(PotionType.POISON),
+        factory.createPotion(PotionType.POISON),
+        factory.createPotion(PotionType.POISON),
+        factory.createPotion(PotionType.HOLY_WATER),
+        factory.createPotion(PotionType.HOLY_WATER)
+    );
+  }
+
+  public final List<Potion> getTopShelf() {
+    return List.copyOf(this.topShelf);
+  }
+
+  public final List<Potion> getBottomShelf() {
+    return List.copyOf(this.bottomShelf);
+  }
+
+  public void drinkPotions() {
+    LOGGER.info("Drinking top shelf potions\n");
+    topShelf.forEach(Potion::drink);
+    LOGGER.info("Drinking bottom shelf potions\n");
+    bottomShelf.forEach(Potion::drink);
+  }
+}
+```
+
+In our scenario, a brave visitor enters the alchemist shop and drinks all the potions.
+
+```java
+// create the alchemist shop with the potions
+var alchemistShop = new AlchemistShop();
+// a brave visitor enters the alchemist shop and drinks all the potions
+alchemistShop.drinkPotions();
 ```
 
 Program output:
 
 ```java
-You become invisible. (Potion=6566818)
-You feel healed. (Potion=648129364)
-You become invisible. (Potion=6566818)
-You feel blessed. (Potion=1104106489)
-You feel blessed. (Potion=1104106489)
-You feel healed. (Potion=648129364)
+Drinking top shelf potions 
+You become invisible. (Potion=1509514333)
+You become invisible. (Potion=1509514333)
+You feel strong. (Potion=739498517)
+You feel healed. (Potion=125130493)
+You become invisible. (Potion=1509514333)
+You feel strong. (Potion=739498517)
+You feel healed. (Potion=125130493)
+You feel healed. (Potion=125130493)
+Drinking bottom shelf potions
+Urgh! This is poisonous. (Potion=166239592)
+Urgh! This is poisonous. (Potion=166239592)
+Urgh! This is poisonous. (Potion=166239592)
+You feel blessed. (Potion=991505714)
+You feel blessed. (Potion=991505714)
 ```
 
 ## Class diagram
@@ -138,13 +192,13 @@ Flyweight pattern when all of the following are true:
 
 * An application uses a large number of objects.
 * Storage costs are high because of the sheer quantity of objects.
-* Most object state can be made extrinsic.
-* Many groups of objects may be replaced by relatively few shared objects once extrinsic state is 
-removed.
+* Most of the object state can be made extrinsic.
+* Many groups of objects may be replaced by relatively few shared objects once the extrinsic state 
+  is removed.
 * The application doesn't depend on object identity. Since flyweight objects may be shared, identity 
 tests will return true for conceptually distinct objects.
 
-## Real world examples
+## Known uses
 
 * [java.lang.Integer#valueOf(int)](http://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#valueOf%28int%29) and similarly for Byte, Character and other wrapped types.
 

flyweight/src/main/java/com/iluwatar/flyweight/AlchemistShop.java

@@ -78,12 +78,12 @@ public class AlchemistShop {
   }
 
   /**
-   * Enumerate potions.
+   * Drink all the potions.
    */
-  public void enumerate() {
-    LOGGER.info("Enumerating top shelf potions\n");
+  public void drinkPotions() {
+    LOGGER.info("Drinking top shelf potions");
     topShelf.forEach(Potion::drink);
-    LOGGER.info("Enumerating bottom shelf potions\n");
+    LOGGER.info("Drinking bottom shelf potions");
     bottomShelf.forEach(Potion::drink);
   }
 }

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

@@ -43,7 +43,9 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
+    // create the alchemist shop with the potions
     var alchemistShop = new AlchemistShop();
-    alchemistShop.enumerate();
+    // a brave visitor enters the alchemist shop and drinks all the potions
+    alchemistShop.drinkPotions();
   }
 }