#590 fix checkstyle error

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

.all-contributorsrc

@@ -1422,6 +1422,24 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "noamgrinch",
+      "name": "Noam Greenshtain",
+      "avatar_url": "https://avatars.githubusercontent.com/u/31648669?v=4",
+      "profile": "https://github.com/noamgrinch",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "qfxl",
+      "name": "yonghong Xu",
+      "avatar_url": "https://avatars.githubusercontent.com/u/14086462?v=4",
+      "profile": "https://xuyonghong.cn/",
+      "contributions": [
+        "doc"
+      ]
     }
   ],
   "contributorsPerLine": 4,

.github/workflows/maven-pr-builder.yml

@@ -29,7 +29,7 @@ name: Java PR Builder
 on:
   pull_request:
     branches: [ master ]
-    types: [ opened, reopened, synchronize ]
+    types: [ opened, reopened, synchronize, labeled, unlabeled ]
 
 jobs:
   build:

README.md

@@ -10,7 +10,7 @@
 [![Coverage](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=coverage)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
 [![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-156-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-158-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 <br/>
@@ -309,6 +309,10 @@ This project is licensed under the terms of the MIT license.
     <td align="center"><a href="https://github.com/richardmr36"><img src="https://avatars.githubusercontent.com/u/19147333?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Martel Richard</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=richardmr36" title="Code">💻</a></td>
     <td align="center"><a href="https://github.com/va1m"><img src="https://avatars.githubusercontent.com/u/17025445?v=4?s=100" width="100px;" alt=""/><br /><sub><b>va1m</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=va1m" title="Code">💻</a></td>
   </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/noamgrinch"><img src="https://avatars.githubusercontent.com/u/31648669?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Noam Greenshtain</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=noamgrinch" title="Code">💻</a></td>
+    <td align="center"><a href="https://xuyonghong.cn/"><img src="https://avatars.githubusercontent.com/u/14086462?v=4?s=100" width="100px;" alt=""/><br /><sub><b>yonghong Xu</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qfxl" title="Documentation">📖</a></td>
+  </tr>
 </table>
 
 <!-- markdownlint-restore -->

active-object/README.md

@@ -79,12 +79,12 @@ public abstract class ActiveCreature{
     return this.name;
   }
 }
-
 ```
 
 We can see that any class that will extend the ActiveCreature class will have its own thread of control to execute and invocate methods.
 
 For example, the Orc class:
+
 ```java
 public class Orc extends ActiveCreature {
 
@@ -96,6 +96,7 @@ public class Orc extends ActiveCreature {
 ```
 
 Now, we can create multiple creatures such as Orcs, tell them to eat and roam and they will execute it on their own thread of control:
+
 ```java
   public static void main(String[] args) {  
     var app = new App();
@@ -121,4 +122,4 @@ Now, we can create multiple creatures such as Orcs, tell them to eat and roam an
 
 ## Class diagram
 
-![alt text](./etc/active-object.urm.png "Active Object class diagram")
+![alt text](./etc/active-object.urm.PNG "Active Object class diagram")

active-object/src/main/java/com/iluwatar/activeobject/ActiveCreature.java

@@ -1,3 +1,26 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
 package com.iluwatar.activeobject;
 
 import java.util.concurrent.BlockingQueue;

active-object/src/main/java/com/iluwatar/activeobject/Orc.java

@@ -1,3 +1,26 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
 package com.iluwatar.activeobject;
 
 /**

active-object/src/test/java/com/iluwatar/activeobject/ActiveCreatureTest.java

@@ -1,3 +1,26 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
 package com.iluwatar.activeobject;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;

active-object/src/test/java/com/iluwatar/activeobject/AppTest.java

@@ -1,3 +1,26 @@
+/*
+ * The MIT License
+ * Copyright © 2014-2021 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
 package com.iluwatar.activeobject;
 
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;

async-method-invocation/README.md

@@ -9,21 +9,160 @@ tags:
 ---
 
 ## Intent
-Asynchronous method invocation is pattern where the calling thread
+
+Asynchronous method invocation is a pattern where the calling thread
 is not blocked while waiting results of tasks. The pattern provides parallel
 processing of multiple independent tasks and retrieving the results via
 callbacks or waiting until everything is done. 
 
+## Explanation
+
+Real world example
+
+> Launching space rockets is an exciting business. The mission command gives an order to launch and 
+> after some undetermined time, the rocket either launches successfully or fails miserably.
+
+In plain words
+
+> Asynchronous method invocation starts task processing and returns immediately before the task is 
+> ready. The results of the task processing are returned to the caller later.
+
+Wikipedia says
+
+> In multithreaded computer programming, asynchronous method invocation (AMI), also known as 
+> asynchronous method calls or the asynchronous pattern is a design pattern in which the call site 
+> is not blocked while waiting for the called code to finish. Instead, the calling thread is 
+> notified when the reply arrives. Polling for a reply is an undesired option.
+
+**Programmatic Example**
+
+In this example, we are launching space rockets and deploying lunar rovers.
+
+The application demonstrates the async method invocation pattern. The key parts of the pattern are 
+`AsyncResult` which is an intermediate container for an asynchronously evaluated value, 
+`AsyncCallback` which can be provided to be executed on task completion and `AsyncExecutor` that 
+manages the execution of the async tasks.
+
+```java
+public interface AsyncResult<T> {
+  boolean isCompleted();
+  T getValue() throws ExecutionException;
+  void await() throws InterruptedException;
+}
+```
+
+```java
+public interface AsyncCallback<T> {
+  void onComplete(T value, Optional<Exception> ex);
+}
+```
+
+```java
+public interface AsyncExecutor {
+  <T> AsyncResult<T> startProcess(Callable<T> task);
+  <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback);
+  <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException;
+}
+```
+
+`ThreadAsyncExecutor` is an implementation of `AsyncExecutor`. Some of its key parts are highlighted 
+next.
+
+```java
+public class ThreadAsyncExecutor implements AsyncExecutor {
+
+  @Override
+  public <T> AsyncResult<T> startProcess(Callable<T> task) {
+    return startProcess(task, null);
+  }
+
+  @Override
+  public <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback) {
+    var result = new CompletableResult<>(callback);
+    new Thread(
+            () -> {
+              try {
+                result.setValue(task.call());
+              } catch (Exception ex) {
+                result.setException(ex);
+              }
+            },
+            "executor-" + idx.incrementAndGet())
+        .start();
+    return result;
+  }
+
+  @Override
+  public <T> T endProcess(AsyncResult<T> asyncResult)
+      throws ExecutionException, InterruptedException {
+    if (!asyncResult.isCompleted()) {
+      asyncResult.await();
+    }
+    return asyncResult.getValue();
+  }
+}
+```
+
+Then we are ready to launch some rockets to see how everything works together.
+
+```java
+public static void main(String[] args) throws Exception {
+  // construct a new executor that will run async tasks
+  var executor = new ThreadAsyncExecutor();
+
+  // start few async tasks with varying processing times, two last with callback handlers
+  final var asyncResult1 = executor.startProcess(lazyval(10, 500));
+  final var asyncResult2 = executor.startProcess(lazyval("test", 300));
+  final var asyncResult3 = executor.startProcess(lazyval(50L, 700));
+  final var asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Deploying lunar rover"));
+  final var asyncResult5 =
+      executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
+
+  // emulate processing in the current thread while async tasks are running in their own threads
+  Thread.sleep(350); // Oh boy, we are working hard here
+  log("Mission command is sipping coffee");
+
+  // wait for completion of the tasks
+  final var result1 = executor.endProcess(asyncResult1);
+  final var result2 = executor.endProcess(asyncResult2);
+  final var result3 = executor.endProcess(asyncResult3);
+  asyncResult4.await();
+  asyncResult5.await();
+
+  // log the results of the tasks, callbacks log immediately when complete
+  log("Space rocket <" + result1 + "> launch complete");
+  log("Space rocket <" + result2 + "> launch complete");
+  log("Space rocket <" + result3 + "> launch complete");
+}
+```
+
+Here's the program console output.
+
+```java
+21:47:08.227 [executor-2] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launched successfully
+21:47:08.269 [main] INFO com.iluwatar.async.method.invocation.App - Mission command is sipping coffee
+21:47:08.318 [executor-4] INFO com.iluwatar.async.method.invocation.App - Space rocket <20> launched successfully
+21:47:08.335 [executor-4] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <20>
+21:47:08.414 [executor-1] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launched successfully
+21:47:08.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Space rocket <callback> launched successfully
+21:47:08.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <callback>
+21:47:08.616 [executor-3] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launched successfully
+21:47:08.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launch complete
+21:47:08.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launch complete
+21:47:08.618 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launch complete
+```
+
 # Class diagram
+
 ![alt text](./etc/async-method-invocation.png "Async Method Invocation")
 
 ## Applicability
-Use async method invocation pattern when
+
+Use the async method invocation pattern when
 
 * You have multiple independent tasks that can run in parallel
 * You need to improve the performance of a group of sequential tasks
-* You have limited amount of processing capacity or long running tasks and the
+* You have a limited amount of processing capacity or long-running tasks and the caller should not wait for the tasks to be ready
-  caller should not wait the tasks to be ready
 
 ## Real world examples
 

async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java

@@ -27,10 +27,12 @@ import java.util.concurrent.Callable;
 import lombok.extern.slf4j.Slf4j;
 
 /**
- * This application demonstrates the async method invocation pattern. Key parts of the pattern are
+ * In this example, we are launching space rockets and deploying lunar rovers.
- * <code>AsyncResult</code> which is an intermediate container for an asynchronously evaluated
+ *
- * value, <code>AsyncCallback</code> which can be provided to be executed on task completion and
+ * <p>The application demonstrates the async method invocation pattern. The key parts of the
- * <code>AsyncExecutor</code> that manages the execution of the async tasks.
+ * pattern are <code>AsyncResult</code> which is an intermediate container for an asynchronously
+ * evaluated value, <code>AsyncCallback</code> which can be provided to be executed on task
+ * completion and <code>AsyncExecutor</code> that manages the execution of the async tasks.
  *
  * <p>The main method shows example flow of async invocations. The main thread starts multiple
  * tasks with variable durations and then continues its own work. When the main thread has done it's
@@ -68,13 +70,14 @@ public class App {
     final var asyncResult1 = executor.startProcess(lazyval(10, 500));
     final var asyncResult2 = executor.startProcess(lazyval("test", 300));
     final var asyncResult3 = executor.startProcess(lazyval(50L, 700));
-    final var asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Callback result 4"));
+    final var asyncResult4 = executor.startProcess(lazyval(20, 400),
+        callback("Deploying lunar rover"));
     final var asyncResult5 =
-        executor.startProcess(lazyval("callback", 600), callback("Callback result 5"));
+        executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
 
     // emulate processing in the current thread while async tasks are running in their own threads
-    Thread.sleep(350); // Oh boy I'm working hard here
+    Thread.sleep(350); // Oh boy, we are working hard here
-    log("Some hard work done");
+    log("Mission command is sipping coffee");
 
     // wait for completion of the tasks
     final var result1 = executor.endProcess(asyncResult1);
@@ -84,9 +87,9 @@ public class App {
     asyncResult5.await();
 
     // log the results of the tasks, callbacks log immediately when complete
-    log("Result 1: " + result1);
+    log("Space rocket <" + result1 + "> launch complete");
-    log("Result 2: " + result2);
+    log("Space rocket <" + result2 + "> launch complete");
-    log("Result 3: " + result3);
+    log("Space rocket <" + result3 + "> launch complete");
   }
 
   /**
@@ -99,7 +102,7 @@ public class App {
   private static <T> Callable<T> lazyval(T value, long delayMillis) {
     return () -> {
       Thread.sleep(delayMillis);
-      log("Task completed with: " + value);
+      log("Space rocket <" + value + "> launched successfully");
       return value;
     };
   }
@@ -115,7 +118,7 @@ public class App {
       if (ex.isPresent()) {
         log(name + " failed: " + ex.map(Exception::getMessage).orElse(""));
       } else {
-        log(name + ": " + value);
+        log(name + " <" + value + ">");
       }
     };
   }

balking/README.md

@@ -9,19 +9,131 @@ tags:
 ---
 
 ## Intent
-Balking Pattern is used to prevent an object from executing certain code if it is an
+
-incomplete or inappropriate state
+Balking Pattern is used to prevent an object from executing a certain code if it is in an incomplete 
+or inappropriate state.
+
+## Explanation
+
+Real world example
+
+> There's a start-button in a washing machine to initiate the laundry washing. When the washing 
+> machine is inactive the button works as expected, but if it's already washing the button does
+> nothing.
+
+In plain words
+
+> Using the balking pattern, a certain code executes only if the object is in particular state.
+
+Wikipedia says
+
+> The balking pattern is a software design pattern that only executes an action on an object when 
+> the object is in a particular state. For example, if an object reads ZIP files and a calling 
+> method invokes a get method on the object when the ZIP file is not open, the object would "balk" 
+> at the request.
+
+**Programmatic Example**
+
+In this example implementation, `WashingMachine` is an object that has two states in which it can 
+be: ENABLED and WASHING. If the machine is ENABLED, the state changes to WASHING using a thread-safe
+method. On the other hand, if it already has been washing and any other thread executes `wash()` 
+it won't do that and returns without doing anything.
+
+Here are the relevant parts of the `WashingMachine` class.
+
+```java
+@Slf4j
+public class WashingMachine {
+
+  private final DelayProvider delayProvider;
+  private WashingMachineState washingMachineState;
+
+  public WashingMachine(DelayProvider delayProvider) {
+    this.delayProvider = delayProvider;
+    this.washingMachineState = WashingMachineState.ENABLED;
+  }
+
+  public WashingMachineState getWashingMachineState() {
+    return washingMachineState;
+  }
+
+  public void wash() {
+    synchronized (this) {
+      var machineState = getWashingMachineState();
+      LOGGER.info("{}: Actual machine state: {}", Thread.currentThread().getName(), machineState);
+      if (this.washingMachineState == WashingMachineState.WASHING) {
+        LOGGER.error("Cannot wash if the machine has been already washing!");
+        return;
+      }
+      this.washingMachineState = WashingMachineState.WASHING;
+    }
+    LOGGER.info("{}: Doing the washing", Thread.currentThread().getName());
+    this.delayProvider.executeAfterDelay(50, TimeUnit.MILLISECONDS, this::endOfWashing);
+  }
+
+  public synchronized void endOfWashing() {
+    washingMachineState = WashingMachineState.ENABLED;
+    LOGGER.info("{}: Washing completed.", Thread.currentThread().getId());
+  }
+}
+```
+
+Here's the simple `DelayProvider` interface used by the `WashingMachine`.
+
+```java
+public interface DelayProvider {
+  void executeAfterDelay(long interval, TimeUnit timeUnit, Runnable task);
+}
+```
+
+Now we introduce the application using the `WashingMachine`.
+
+```java
+  public static void main(String... args) {
+    final var washingMachine = new WashingMachine();
+    var executorService = Executors.newFixedThreadPool(3);
+    for (int i = 0; i < 3; i++) {
+      executorService.execute(washingMachine::wash);
+    }
+    executorService.shutdown();
+    try {
+      executorService.awaitTermination(10, TimeUnit.SECONDS);
+    } catch (InterruptedException ie) {
+      LOGGER.error("ERROR: Waiting on executor service shutdown!");
+      Thread.currentThread().interrupt();
+    }
+  }
+```
+
+Here is the console output of the program.
+
+```
+14:02:52.268 [pool-1-thread-2] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-2: Actual machine state: ENABLED
+14:02:52.272 [pool-1-thread-2] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-2: Doing the washing
+14:02:52.272 [pool-1-thread-3] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-3: Actual machine state: WASHING
+14:02:52.273 [pool-1-thread-3] ERROR com.iluwatar.balking.WashingMachine - Cannot wash if the machine has been already washing!
+14:02:52.273 [pool-1-thread-1] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-1: Actual machine state: WASHING
+14:02:52.273 [pool-1-thread-1] ERROR com.iluwatar.balking.WashingMachine - Cannot wash if the machine has been already washing!
+14:02:52.324 [pool-1-thread-2] INFO com.iluwatar.balking.WashingMachine - 14: Washing completed.
+```
 
 ## Class diagram
+
 ![alt text](./etc/balking.png "Balking")
 
 ## Applicability
+
 Use the Balking pattern when
 
-* you want to invoke an action on an object only when it is in a particular state
+* You want to invoke an action on an object only when it is in a particular state
-* objects are generally only in a state that is prone to balking temporarily
+* Objects are generally only in a state that is prone to balking temporarily but for an unknown 
-but for an unknown amount of time
+  amount of time
 
 ## Related patterns
-* Guarded Suspension Pattern
+
-* Double Checked Locking Pattern
+* [Guarded Suspension Pattern](https://java-design-patterns.com/patterns/guarded-suspension/)
+* [Double Checked Locking Pattern](https://java-design-patterns.com/patterns/double-checked-locking/)
+
+## Credits
+
+* [Patterns in Java: A Catalog of Reusable Design Patterns Illustrated with UML, 2nd Edition, Volume 1](https://www.amazon.com/gp/product/0471227293/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=0471227293&linkId=0e39a59ffaab93fb476036fecb637b99)

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

@@ -32,11 +32,11 @@ import lombok.extern.slf4j.Slf4j;
  * then the method will return without doing anything. Objects that use this pattern are generally
  * only in a state that is prone to balking temporarily but for an unknown amount of time
  *
- * <p>In this example implementation WashingMachine is an object that has two states in which it
+ * <p>In this example implementation, {@link WashingMachine} is an object that has two states in
- * can be: ENABLED and WASHING. If the machine is ENABLED the state is changed into WASHING that any
+ * which it can be: ENABLED and WASHING. If the machine is ENABLED, the state changes to WASHING
- * other thread can't invoke this action on this and then do the job. On the other hand if it have
+ * using a thread-safe method. On the other hand, if it already has been washing and any other
- * been already washing and any other thread execute wash() it can't do that once again and returns
+ * thread executes {@link WashingMachine#wash()} it won't do that and returns without doing
- * doing nothing.
+ * anything.
  */
 @Slf4j
 public class App {
@@ -54,11 +54,12 @@ public class App {
     }
     executorService.shutdown();
     try {
-      executorService.awaitTermination(10, TimeUnit.SECONDS);
+      if (!executorService.awaitTermination(10, TimeUnit.SECONDS)) {
+        executorService.shutdownNow();
+      }
     } catch (InterruptedException ie) {
       LOGGER.error("ERROR: Waiting on executor service shutdown!");
       Thread.currentThread().interrupt();
     }
   }
-
 }

factory/README.md

@@ -105,7 +105,7 @@ Program output:
 
 ```java
 This is Ford.
-This Ferrari.
+This is Ferrari.
 ```
 
 ## Class Diagram