check spelling and update topic

event-aggregator/README.md

@@ -9,6 +9,10 @@ tags:
  - Reactive
 ---
 
+## Name
+
+Event Aggregator
+
 ## Intent
 A system with lots of objects can lead to complexities when a
 client wants to subscribe to events. The client has to find and register for
@@ -17,6 +21,136 @@ requires a separate subscription. An Event Aggregator acts as a single source
 of events for many objects. It registers for all the events of the many objects
 allowing clients to register with just the aggregator.
 
+## Explanation
+
+Real-world example
+
+> King Joffrey sits on the iron throne and rules the seven kingdoms of Westeros. He receives most
+> of his critical information from King's Hand, the second in command. King's hand has many
+> close advisors himself, feeding him with relevant information about events occurring in the
+> kingdom.
+
+In Plain Words
+
+> Event Aggregator is an event mediator that collects events from multiple sources and delivers
+> them to registered observers.
+
+**Programmatic Example**
+
+In our programmatic example, we demonstrate the implementation of an event aggregator pattern. Some of
+the objects are event listeners, some are event emitters, and the event aggregator does both.
+
+```java
+public interface EventObserver {
+  void onEvent(Event e);
+}
+
+public abstract class EventEmitter {
+
+  private final Map<Event, List<EventObserver>> observerLists;
+
+  public EventEmitter() {
+    observerLists = new HashMap<>();
+  }
+
+  public final void registerObserver(EventObserver obs, Event e) {
+    ...
+  }
+
+  protected void notifyObservers(Event e) {
+    ...
+  }
+}
+```
+
+`KingJoffrey` is listening to events from `KingsHand`.
+
+```java
+@Slf4j
+public class KingJoffrey implements EventObserver {
+  @Override
+  public void onEvent(Event e) {
+    LOGGER.info("Received event from the King's Hand: {}", e.toString());
+  }
+}
+```
+
+`KingsHand` is listening to events from his subordinates `LordBaelish`, `LordVarys`, and `Scout`.
+Whatever he hears from them, he delivers to `KingJoffrey`.
+
+```java
+public class KingsHand extends EventEmitter implements EventObserver {
+
+  public KingsHand() {
+  }
+
+  public KingsHand(EventObserver obs, Event e) {
+    super(obs, e);
+  }
+
+  @Override
+  public void onEvent(Event e) {
+    notifyObservers(e);
+  }
+}
+```
+
+For example, `LordVarys` finds a traitor every Sunday and notifies the `KingsHand`.
+
+```java
+@Slf4j
+public class LordVarys extends EventEmitter implements EventObserver {
+  @Override
+  public void timePasses(Weekday day) {
+    if (day == Weekday.SATURDAY) {
+      notifyObservers(Event.TRAITOR_DETECTED);
+    }
+  }
+}
+```
+
+The following snippet demonstrates how the objects are constructed and wired together.
+
+```java
+    var kingJoffrey = new KingJoffrey();
+
+    var kingsHand = new KingsHand();
+    kingsHand.registerObserver(kingJoffrey, Event.TRAITOR_DETECTED);
+    kingsHand.registerObserver(kingJoffrey, Event.STARK_SIGHTED);
+    kingsHand.registerObserver(kingJoffrey, Event.WARSHIPS_APPROACHING);
+    kingsHand.registerObserver(kingJoffrey, Event.WHITE_WALKERS_SIGHTED);
+
+    var varys = new LordVarys();
+    varys.registerObserver(kingsHand, Event.TRAITOR_DETECTED);
+    varys.registerObserver(kingsHand, Event.WHITE_WALKERS_SIGHTED);
+
+    var scout = new Scout();
+    scout.registerObserver(kingsHand, Event.WARSHIPS_APPROACHING);
+    scout.registerObserver(varys, Event.WHITE_WALKERS_SIGHTED);
+
+    var baelish = new LordBaelish(kingsHand, Event.STARK_SIGHTED);
+
+    var emitters = List.of(
+        kingsHand,
+        baelish,
+        varys,
+        scout
+    );
+
+    Arrays.stream(Weekday.values())
+        .<Consumer<? super EventEmitter>>map(day -> emitter -> emitter.timePasses(day))
+        .forEachOrdered(emitters::forEach);
+```
+
+The console output after running the example.
+
+```
+18:21:52.955 [main] INFO com.iluwatar.event.aggregator.KingJoffrey - Received event from the King's Hand: Warships approaching
+18:21:52.960 [main] INFO com.iluwatar.event.aggregator.KingJoffrey - Received event from the King's Hand: White walkers sighted
+18:21:52.960 [main] INFO com.iluwatar.event.aggregator.KingJoffrey - Received event from the King's Hand: Stark sighted
+18:21:52.960 [main] INFO com.iluwatar.event.aggregator.KingJoffrey - Received event from the King's Hand: Traitor detected
+```
+
 ## Class diagram
 ![alt text](./etc/classes.png "Event Aggregator")
 
@@ -26,9 +160,13 @@ Use the Event Aggregator pattern when
 * Event Aggregator is a good choice when you have lots of objects that are
   potential event sources. Rather than have the observer deal with registering
   with them all, you can centralize the registration logic to the Event
-  Aggregator. As well as simplifying registration, a Event Aggregator also
+  Aggregator. As well as simplifying registration, an Event Aggregator also
   simplifies the memory management issues in using observers.
 
+## Related patterns
+
+* [Observer](https://java-design-patterns.com/patterns/observer/)
+
 ## Credits
 
 * [Martin Fowler - Event Aggregator](http://martinfowler.com/eaaDev/EventAggregator.html)

factory-kit/README.md

@@ -10,115 +10,19 @@ tags:
 ---
 
 ## Intent
-
 Define a factory of immutable content with separated builder and factory interfaces.
 
-## Explanation
-
-Real-world example
-
-> Imagine a magical weapon factory that can create any type of weapon wished for. When the factory
-> is unboxed, the master recites the weapon types needed to prepare it. After that, any of those
-> weapon types can be summoned in an instant. 
-
-In plain words
-
-> Factory kit is a configurable object builder.
-
-**Programmatic Example**
-
-Let's first define the simple `Weapon` hierarchy.
-
-```java
-public interface Weapon {
-}
-
-public enum WeaponType {
-    SWORD,
-    AXE,
-    BOW,
-    SPEAR
-}
-
-public class Sword implements Weapon {
-    @Override
-    public String toString() {
-        return "Sword";
-    }
-}
-
-// Axe, Bow, and Spear are defined similarly
-```
-
-Next, we define a functional interface that allows adding a builder with a name to the factory.
-
-```java
-public interface Builder {
-  void add(WeaponType name, Supplier<Weapon> supplier);
-}
-```
-
-The meat of the example is the `WeaponFactory` interface that effectively implements the factory
-kit pattern. The method `#factory` is used to configure the factory with the classes it needs to
-be able to construct. The method `#create` is then used to create object instances.
-
-```java
-public interface WeaponFactory {
-
-  static WeaponFactory factory(Consumer<Builder> consumer) {
-      var map = new HashMap<WeaponType, Supplier<Weapon>>();
-      consumer.accept(map::put);
-      return name -> map.get(name).get();
-  }
-    
-  Weapon create(WeaponType name);
-}
-```
-
-Now, we can show how `WeaponFactory` can be used.
-
-```java
-var factory = WeaponFactory.factory(builder -> {
-  builder.add(WeaponType.SWORD, Sword::new);
-  builder.add(WeaponType.AXE, Axe::new);
-  builder.add(WeaponType.SPEAR, Spear::new);
-  builder.add(WeaponType.BOW, Bow::new);
-});
-var list = new ArrayList<Weapon>();
-list.add(factory.create(WeaponType.AXE));
-list.add(factory.create(WeaponType.SPEAR));
-list.add(factory.create(WeaponType.SWORD));
-list.add(factory.create(WeaponType.BOW));
-list.stream().forEach(weapon -> LOGGER.info("{}", weapon.toString()));
-```
-
-Here is the console output when the example is run.
-
-```
-21:15:49.709 [main] INFO com.iluwatar.factorykit.App - Axe
-21:15:49.713 [main] INFO com.iluwatar.factorykit.App - Spear
-21:15:49.713 [main] INFO com.iluwatar.factorykit.App - Sword
-21:15:49.713 [main] INFO com.iluwatar.factorykit.App - Bow
-```
-
 ## Class diagram
-
 ![alt text](./etc/factory-kit.png "Factory Kit")
 
 ## Applicability
-
 Use the Factory Kit pattern when
 
-* The factory class can't anticipate the types of objects it must create
-* A new instance of a custom builder is needed instead of a global one
-* The types of objects that the factory can build need to be defined outside the class
-* The builder and creator interfaces need to be separated
-
-## Related patterns
-
-* [Builder](https://java-design-patterns.com/patterns/builder/)
-* [Factory](https://java-design-patterns.com/patterns/factory/)
+* a class can't anticipate the class of objects it must create
+* you just want a new instance of a custom builder instead of the global one
+* you explicitly want to define types of objects, that factory can build
+* you want a separated builder and creator interface
 
 ## Credits
 
-* [Design Pattern Reloaded by Remi Forax](https://www.youtube.com/watch?v=-k2X7guaArU)
+* [Design Pattern Reloaded by Remi Forax: ](https://www.youtube.com/watch?v=-k2X7guaArU)

factory-kit/src/main/java/com/iluwatar/factorykit/App.java

@@ -23,16 +23,14 @@
 
 package com.iluwatar.factorykit;
 
-import java.util.ArrayList;
-
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * Factory kit is a creational pattern that defines a factory of immutable content with separated
+ * Factory-kit is a creational pattern which defines a factory of immutable content with separated
  * builder and factory interfaces to deal with the problem of creating one of the objects specified
- * directly in the factory kit instance.
+ * directly in the factory-kit instance.
  *
- * <p>In the given example {@link WeaponFactory} represents the factory kit, that contains four
+ * <p>In the given example {@link WeaponFactory} represents the factory-kit, that contains four
  * {@link Builder}s for creating new objects of the classes implementing {@link Weapon} interface.
  *
  * <p>Each of them can be called with {@link WeaponFactory#create(WeaponType)} method, with
@@ -54,11 +52,7 @@ public class App {
       builder.add(WeaponType.SPEAR, Spear::new);
       builder.add(WeaponType.BOW, Bow::new);
     });
-    var list = new ArrayList<Weapon>();
-    list.add(factory.create(WeaponType.AXE));
-    list.add(factory.create(WeaponType.SPEAR));
-    list.add(factory.create(WeaponType.SWORD));
-    list.add(factory.create(WeaponType.BOW));
-    list.stream().forEach(weapon -> LOGGER.info("{}", weapon.toString()));
+    var axe = factory.create(WeaponType.AXE);
+    LOGGER.info(axe.toString());
   }
 }

trampoline/README.md

@@ -17,19 +17,19 @@ and to interleave the execution of functions without hard coding them together.
 ## Explanation
 
 Recursion is a frequently adopted technique for solving algorithmic problems in a divide and conquer
-style. For example calculating fibonacci accumulating sum and factorials. In these kinds of problems 
-recursion is more straightforward than their loop counterpart. Furthermore recursion may need less 
-code and looks more concise. There is a saying that every recursion problem can be solved using 
-a loop with the cost of writing code that is more difficult to understand.
+style. For example, calculating Fibonacci accumulating sum and factorials. In these kinds of 
+problems, recursion is more straightforward than its loop counterpart. Furthermore, recursion may 
+need less code and looks more concise. There is a saying that every recursion problem can be solved 
+using a loop with the cost of writing code that is more difficult to understand.
 
-However recursion type solutions have one big caveat. For each recursive call it typically needs 
+However, recursion-type solutions have one big caveat. For each recursive call, it typically needs 
 an intermediate value stored and there is a limited amount of stack memory available. Running out of 
 stack memory creates a stack overflow error and halts the program execution.
 
-Trampoline pattern is a trick that allows us define recursive algorithms in Java without blowing the 
+Trampoline pattern is a trick that allows defining recursive algorithms in Java without blowing the 
 stack. 
 
-Real world example
+Real-world example
 
 > A recursive Fibonacci calculation without the stack overflow problem using the Trampoline pattern.       
 
@@ -105,24 +105,26 @@ public interface Trampoline<T> {
 Using the `Trampoline` to get Fibonacci values.
 
 ```java
-  public static Trampoline<Integer> loop(int times, int prod) {
+public static void main(String[] args) {
+    LOGGER.info("Start calculating war casualties");
+    var result = loop(10, 1).result();
+    LOGGER.info("The number of orcs perished in the war: {}", result);
+}
+
+public static Trampoline<Integer> loop(int times, int prod) {
     if (times == 0) {
-      return Trampoline.done(prod);
+        return Trampoline.done(prod);
     } else {
-      return Trampoline.more(() -> loop(times - 1, prod * times));
+        return Trampoline.more(() -> loop(times - 1, prod * times));
     }
-  }
-  
-  log.info("start pattern");
-  var result = loop(10, 1).result();
-  log.info("result {}", result);
+}
 ```
 
 Program output:
 
 ```
-start pattern
-result 3628800
+19:22:24.462 [main] INFO com.iluwatar.trampoline.TrampolineApp - Start calculating war casualties
+19:22:24.472 [main] INFO com.iluwatar.trampoline.TrampolineApp - The number of orcs perished in the war: 3628800
 ```
 
 ## Class diagram
@@ -133,8 +135,8 @@ result 3628800
 
 Use the Trampoline pattern when
 
-* For implementing tail recursive function. This pattern allows to switch on a stackless operation.
-* For interleaving the execution of two or more functions on the same thread.
+* For implementing tail-recursive functions. This pattern allows to switch on a stackless operation.
+* For interleaving execution of two or more functions on the same thread.
 
 ## Known uses
 

trampoline/src/main/java/com/iluwatar/trampoline/Trampoline.java

@@ -107,6 +107,4 @@ public interface Trampoline<T> {
       }
     };
   }
-
-
 }

trampoline/src/main/java/com/iluwatar/trampoline/TrampolineApp.java

@@ -39,9 +39,9 @@ public class TrampolineApp {
    * Main program for showing pattern. It does loop with factorial function.
    */
   public static void main(String[] args) {
-    LOGGER.info("start pattern");
+    LOGGER.info("Start calculating war casualties");
     var result = loop(10, 1).result();
-    LOGGER.info("result {}", result);
+    LOGGER.info("The number of orcs perished in the war: {}", result);
 
   }
 
@@ -55,5 +55,4 @@ public class TrampolineApp {
       return Trampoline.more(() -> loop(times - 1, prod * times));
     }
   }
-
 }