Resolves checkstyle errors for collection-pipeline, command, commander (#1061)

* Reduces checkstyle errors in collection-pipeline

* Reduces checkstyle errors in command

* Reduces checkstyle errors in commander

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/App.java

@@ -23,21 +23,18 @@
 
 package com.iluwatar.collectionpipeline;
 
+import java.util.List;
+import java.util.Map;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.List;
-import java.util.Map;
-
 /**
- * In imperative-style programming, it is common to use for and while loops for
+ * In imperative-style programming, it is common to use for and while loops for most kinds of data
- * most kinds of data processing. Function composition is a simple technique
+ * processing. Function composition is a simple technique that lets you sequence modular functions
- * that lets you sequence modular functions to create more complex operations.
+ * to create more complex operations. When you run data through the sequence, you have a collection
- * When you run data through the sequence, you have a collection pipeline.
+ * pipeline. Together, the Function Composition and Collection Pipeline patterns enable you to
- * Together, the Function Composition and Collection Pipeline patterns enable
+ * create sophisticated programs where data flow from upstream to downstream and is passed through a
- * you to create sophisticated programs where data flow from upstream to
+ * series of transformations.
- * downstream and is passed through a series of transformations.
- *
  */
 public class App {
 
@@ -45,32 +42,35 @@ public class App {
 
   /**
    * Program entry point.
-   * 
+   *
-   * @param args
+   * @param args command line args
-   *            command line args
    */
   public static void main(String[] args) {
 
     List<Car> cars = CarFactory.createCars();
-    
+
     List<String> modelsImperative = ImperativeProgramming.getModelsAfter2000(cars);
     LOGGER.info(modelsImperative.toString());
 
     List<String> modelsFunctional = FunctionalProgramming.getModelsAfter2000(cars);
     LOGGER.info(modelsFunctional.toString());
-    
+
-    Map<Category, List<Car>> groupingByCategoryImperative = ImperativeProgramming.getGroupingOfCarsByCategory(cars);
+    Map<Category, List<Car>> groupingByCategoryImperative =
+        ImperativeProgramming.getGroupingOfCarsByCategory(cars);
     LOGGER.info(groupingByCategoryImperative.toString());
 
-    Map<Category, List<Car>> groupingByCategoryFunctional = FunctionalProgramming.getGroupingOfCarsByCategory(cars);
+    Map<Category, List<Car>> groupingByCategoryFunctional =
+        FunctionalProgramming.getGroupingOfCarsByCategory(cars);
     LOGGER.info(groupingByCategoryFunctional.toString());
-    
+
     Person john = new Person(cars);
 
-    List<Car> sedansOwnedImperative = ImperativeProgramming.getSedanCarsOwnedSortedByDate(List.of(john));
+    List<Car> sedansOwnedImperative =
+        ImperativeProgramming.getSedanCarsOwnedSortedByDate(List.of(john));
     LOGGER.info(sedansOwnedImperative.toString());
 
-    List<Car> sedansOwnedFunctional = FunctionalProgramming.getSedanCarsOwnedSortedByDate(List.of(john));
+    List<Car> sedansOwnedFunctional =
+        FunctionalProgramming.getSedanCarsOwnedSortedByDate(List.of(john));
     LOGGER.info(sedansOwnedFunctional.toString());
   }
 }

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Car.java

@@ -34,10 +34,11 @@ public class Car {
 
   /**
    * Constructor to create an instance of car.
-   * @param make the make of the car
+   *
-   * @param model the model of the car
+   * @param make       the make of the car
+   * @param model      the model of the car
    * @param yearOfMake the year of built of the car
-   * @param category the {@link Category} of the car
+   * @param category   the {@link Category} of the car
    */
   public Car(String make, String model, int yearOfMake, Category category) {
     this.make = make;
@@ -103,7 +104,7 @@ public class Car {
   public int getYear() {
     return year;
   }
-  
+
   public Category getCategory() {
     return category;
   }

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/CarFactory.java

@@ -34,6 +34,7 @@ public class CarFactory {
 
   /**
    * Factory method to create a {@link List} of {@link Car} instances.
+   *
    * @return {@link List} of {@link Car}
    */
   public static List<Car> createCars() {

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Category.java

@@ -24,7 +24,7 @@
 package com.iluwatar.collectionpipeline;
 
 /**
- * Enum for the category of car 
+ * Enum for the category of car.
  */
 public enum Category {
   JEEP, SEDAN, CONVERTIBLE

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/FunctionalProgramming.java

@@ -30,20 +30,17 @@ import java.util.stream.Collectors;
 
 /**
  * Iterating and sorting with a collection pipeline
- * 
+ *
  * <p>In functional programming, it's common to sequence complex operations through
- * a series of smaller modular functions or operations. The series is called a
+ * a series of smaller modular functions or operations. The series is called a composition of
- * composition of functions, or a function composition. When a collection of
+ * functions, or a function composition. When a collection of data flows through a function
- * data flows through a function composition, it becomes a collection pipeline.
+ * composition, it becomes a collection pipeline. Function Composition and Collection Pipeline are
- * Function Composition and Collection Pipeline are two design patterns
+ * two design patterns frequently used in functional-style programming.
- * frequently used in functional-style programming.
+ *
- * 
  * <p>Instead of passing a lambda expression to the map method, we passed the
- * method reference Car::getModel. Likewise, instead of passing the lambda
+ * method reference Car::getModel. Likewise, instead of passing the lambda expression car ->
- * expression car -> car.getYear() to the comparing method, we passed the method
+ * car.getYear() to the comparing method, we passed the method reference Car::getYear. Method
- * reference Car::getYear. Method references are short, concise, and expressive.
+ * references are short, concise, and expressive. It is best to use them wherever possible.
- * It is best to use them wherever possible.
- * 
  */
 public class FunctionalProgramming {
   private FunctionalProgramming() {
@@ -51,35 +48,35 @@ public class FunctionalProgramming {
 
   /**
    * Method to get models using for collection pipeline.
-   * 
+   *
    * @param cars {@link List} of {@link Car} to be used for filtering
    * @return {@link List} of {@link String} representing models built after year 2000
    */
   public static List<String> getModelsAfter2000(List<Car> cars) {
     return cars.stream().filter(car -> car.getYear() > 2000)
-      .sorted(Comparator.comparing(Car::getYear))
+        .sorted(Comparator.comparing(Car::getYear))
-      .map(Car::getModel).collect(Collectors.toList());
+        .map(Car::getModel).collect(Collectors.toList());
   }
-  
+
   /**
-   * Method to group cars by category using groupingBy
+   * Method to group cars by category using groupingBy.
-   * 
+   *
    * @param cars {@link List} of {@link Car} to be used for grouping
    * @return {@link Map} with category as key and cars belonging to that category as value
    */
   public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
     return cars.stream().collect(Collectors.groupingBy(Car::getCategory));
   }
-  
+
   /**
-   * Method to get all Sedan cars belonging to a group of persons sorted by year of manufacture 
+   * Method to get all Sedan cars belonging to a group of persons sorted by year of manufacture.
-   * 
+   *
    * @param persons {@link List} of {@link Person} to be used
    * @return {@link List} of {@link Car} to belonging to the group
    */
   public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
     return persons.stream().map(Person::getCars).flatMap(List::stream)
-      .filter(car -> Category.SEDAN.equals(car.getCategory()))
+        .filter(car -> Category.SEDAN.equals(car.getCategory()))
-      .sorted(Comparator.comparing(Car::getYear)).collect(Collectors.toList());
+        .sorted(Comparator.comparing(Car::getYear)).collect(Collectors.toList());
   }
 }

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/ImperativeProgramming.java

@@ -31,23 +31,20 @@ import java.util.List;
 import java.util.Map;
 
 /**
- * Imperative-style programming to iterate over the list and get the names of
+ * Imperative-style programming to iterate over the list and get the names of cars made later than
- * cars made later than the year 2000. We then sort the models in ascending
+ * the year 2000. We then sort the models in ascending order by year.
- * order by year.
+ *
- * 
  * <p>As you can see, there's a lot of looping in this code. First, the
- * getModelsAfter2000UsingFor method takes a list of cars as its parameter. It
+ * getModelsAfter2000UsingFor method takes a list of cars as its parameter. It extracts or filters
- * extracts or filters out cars made after the year 2000, putting them into a
+ * out cars made after the year 2000, putting them into a new list named carsSortedByYear. Next, it
- * new list named carsSortedByYear. Next, it sorts that list in ascending order
+ * sorts that list in ascending order by year-of-make. Finally, it loops through the list
- * by year-of-make. Finally, it loops through the list carsSortedByYear to get
+ * carsSortedByYear to get the model names and returns them in a list.
- * the model names and returns them in a list.
+ *
- * 
  * <p>This short example demonstrates what I call the effect of statements. While
- * functions and methods in general can be used as expressions, the {@link Collections}
+ * functions and methods in general can be used as expressions, the {@link Collections} sort method
- * sort method doesn't return a result. Because it is used as a statement, it
+ * doesn't return a result. Because it is used as a statement, it mutates the list given as
- * mutates the list given as argument. Both of the for loops also mutate lists
+ * argument. Both of the for loops also mutate lists as they iterate. Being statements, that's just
- * as they iterate. Being statements, that's just how these elements work. As a
+ * how these elements work. As a result, the code contains unnecessary garbage variables
- * result, the code contains unnecessary garbage variables
  */
 public class ImperativeProgramming {
   private ImperativeProgramming() {
@@ -55,6 +52,7 @@ public class ImperativeProgramming {
 
   /**
    * Method to return the car models built after year 2000 using for loops.
+   *
    * @param cars {@link List} of {@link Car} to iterate over
    * @return {@link List} of {@link String} of car models built after year 2000
    */
@@ -80,16 +78,16 @@ public class ImperativeProgramming {
 
     return models;
   }
-  
+
   /**
-   * Method to group cars by category using for loops
+   * Method to group cars by category using for loops.
-   * 
+   *
    * @param cars {@link List} of {@link Car} to be used for grouping
    * @return {@link Map} with category as key and cars belonging to that category as value
    */
   public static Map<Category, List<Car>> getGroupingOfCarsByCategory(List<Car> cars) {
     Map<Category, List<Car>> groupingByCategory = new HashMap<>();
-    for (Car car: cars) {
+    for (Car car : cars) {
       if (groupingByCategory.containsKey(car.getCategory())) {
         groupingByCategory.get(car.getCategory()).add(car);
       } else {
@@ -100,33 +98,34 @@ public class ImperativeProgramming {
     }
     return groupingByCategory;
   }
-  
+
   /**
-   * Method to get all Sedan cars belonging to a group of persons sorted by year of manufacture using for loops 
+   * Method to get all Sedan cars belonging to a group of persons sorted by year of manufacture
-   * 
+   * using for loops.
+   *
    * @param persons {@link List} of {@link Person} to be used
    * @return {@link List} of {@link Car} to belonging to the group
    */
   public static List<Car> getSedanCarsOwnedSortedByDate(List<Person> persons) {
     List<Car> cars = new ArrayList<>();
-    for (Person person: persons) {
+    for (Person person : persons) {
       cars.addAll(person.getCars());
     }
-  
+
     List<Car> sedanCars = new ArrayList<>();
-    for (Car car: cars) {
+    for (Car car : cars) {
       if (Category.SEDAN.equals(car.getCategory())) {
         sedanCars.add(car);
       }
     }
-  
+
     sedanCars.sort(new Comparator<Car>() {
       @Override
       public int compare(Car o1, Car o2) {
         return o1.getYear() - o2.getYear();
       }
     });
-  
+
     return sedanCars;
   }
 }

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/Person.java

@@ -33,6 +33,7 @@ public class Person {
 
   /**
    * Constructor to create an instance of person.
+   *
    * @param cars the list of cars owned
    */
   public Person(List<Car> cars) {

collection-pipeline/src/test/java/com/iluwatar/collectionpipeline/AppTest.java

@@ -23,14 +23,13 @@
 
 package com.iluwatar.collectionpipeline;
 
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import java.util.List;
 import java.util.Map;
-
+import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Tests that Collection Pipeline methods work as expected.
@@ -39,35 +38,35 @@ public class AppTest {
   private static final Logger LOGGER = LoggerFactory.getLogger(AppTest.class);
 
   private List<Car> cars = CarFactory.createCars();
-  
+
   @Test
   public void testGetModelsAfter2000UsingFor() {
     var models = ImperativeProgramming.getModelsAfter2000(cars);
     assertEquals(List.of("Avenger", "Wrangler", "Focus", "Cascada"), models);
   }
-  
+
   @Test
   public void testGetModelsAfter2000UsingPipeline() {
     var models = FunctionalProgramming.getModelsAfter2000(cars);
     assertEquals(List.of("Avenger", "Wrangler", "Focus", "Cascada"), models);
   }
-  
+
   @Test
   public void testGetGroupingOfCarsByCategory() {
     var modelsExpected = Map.of(
-            Category.CONVERTIBLE, List.of(new Car("Buick", "Cascada", 2016, Category.CONVERTIBLE),
+        Category.CONVERTIBLE, List.of(new Car("Buick", "Cascada", 2016, Category.CONVERTIBLE),
-                    new Car("Chevrolet", "Geo Metro", 1992, Category.CONVERTIBLE)),
+            new Car("Chevrolet", "Geo Metro", 1992, Category.CONVERTIBLE)),
-            Category.SEDAN, List.of(new Car("Dodge", "Avenger", 2010, Category.SEDAN),
+        Category.SEDAN, List.of(new Car("Dodge", "Avenger", 2010, Category.SEDAN),
-                    new Car("Ford", "Focus", 2012, Category.SEDAN)),
+            new Car("Ford", "Focus", 2012, Category.SEDAN)),
-            Category.JEEP, List.of(new Car("Jeep", "Wrangler", 2011, Category.JEEP),
+        Category.JEEP, List.of(new Car("Jeep", "Wrangler", 2011, Category.JEEP),
-                    new Car("Jeep", "Comanche", 1990, Category.JEEP)));
+            new Car("Jeep", "Comanche", 1990, Category.JEEP)));
     var modelsFunctional = FunctionalProgramming.getGroupingOfCarsByCategory(cars);
     var modelsImperative = ImperativeProgramming.getGroupingOfCarsByCategory(cars);
     LOGGER.info("Category " + modelsFunctional);
     assertEquals(modelsExpected, modelsFunctional);
     assertEquals(modelsExpected, modelsImperative);
   }
-  
+
   @Test
   public void testGetSedanCarsOwnedSortedByDate() {
     var john = new Person(cars);

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

@@ -24,31 +24,28 @@
 package com.iluwatar.command;
 
 /**
- * 
  * The Command pattern is a behavioral design pattern in which an object is used to encapsulate all
  * information needed to perform an action or trigger an event at a later time. This information
  * includes the method name, the object that owns the method and values for the method parameters.
- * <p>
+ *
- * Four terms always associated with the command pattern are command, receiver, invoker and client.
+ * <p>Four terms always associated with the command pattern are command, receiver, invoker and
- * A command object (spell) knows about the receiver (target) and invokes a method of the receiver.
+ * client. A command object (spell) knows about the receiver (target) and invokes a method of the
- * Values for parameters of the receiver method are stored in the command. The receiver then does
+ * receiver. Values for parameters of the receiver method are stored in the command. The receiver
- * the work. An invoker object (wizard) knows how to execute a command, and optionally does
+ * then does the work. An invoker object (wizard) knows how to execute a command, and optionally
- * bookkeeping about the command execution. The invoker does not know anything about a concrete
+ * does bookkeeping about the command execution. The invoker does not know anything about a concrete
  * command, it knows only about command interface. Both an invoker object and several command
  * objects are held by a client object (app). The client decides which commands to execute at which
  * points. To execute a command, it passes the command object to the invoker object.
- * <p>
+ *
- * In other words, in this example the wizard casts spells on the goblin. The wizard keeps track of
+ * <p>In other words, in this example the wizard casts spells on the goblin. The wizard keeps track
- * the previous spells cast, so it is easy to undo them. In addition, the wizard keeps track of the
+ * of the previous spells cast, so it is easy to undo them. In addition, the wizard keeps track of
- * spells undone, so they can be redone.
+ * the spells undone, so they can be redone.
- * 
- * 
  */
 public class App {
 
   /**
-   * Program entry point
+   * Program entry point.
-   * 
+   *
    * @param args command line args
    */
   public static void main(String[] args) {

command/src/main/java/com/iluwatar/command/Command.java

@@ -24,9 +24,7 @@
 package com.iluwatar.command;
 
 /**
- * 
  * Interface for Commands.
- * 
  */
 public abstract class Command {
 

command/src/main/java/com/iluwatar/command/Goblin.java

@@ -24,9 +24,7 @@
 package com.iluwatar.command;
 
 /**
- * 
+ * Goblin is the target of the spells.
- * Goblin is the target of the spells
- *
  */
 public class Goblin extends Target {
 

command/src/main/java/com/iluwatar/command/InvisibilitySpell.java

@@ -24,9 +24,7 @@
 package com.iluwatar.command;
 
 /**
- * 
+ * InvisibilitySpell is a concrete command.
- * InvisibilitySpell is a concrete command
- *
  */
 public class InvisibilitySpell extends Command {
 

command/src/main/java/com/iluwatar/command/ShrinkSpell.java

@@ -24,9 +24,7 @@
 package com.iluwatar.command;
 
 /**
- * 
+ * ShrinkSpell is a concrete command.
- * ShrinkSpell is a concrete command
- *
  */
 public class ShrinkSpell extends Command {
 

command/src/main/java/com/iluwatar/command/Size.java

@@ -24,9 +24,7 @@
 package com.iluwatar.command;
 
 /**
- *
  * Enumeration for target size.
- *
  */
 public enum Size {
 

command/src/main/java/com/iluwatar/command/Target.java

@@ -27,9 +27,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * 
  * Base class for spell targets.
- *
  */
 public abstract class Target {
 
@@ -59,7 +57,7 @@ public abstract class Target {
   public abstract String toString();
 
   /**
-   * Print status
+   * Print status.
    */
   public void printStatus() {
     LOGGER.info("{}, [size={}] [visibility={}]", this, getSize(), getVisibility());

command/src/main/java/com/iluwatar/command/Visibility.java

@@ -24,9 +24,7 @@
 package com.iluwatar.command;
 
 /**
- * 
  * Enumeration for target visibility.
- *
  */
 public enum Visibility {
 

command/src/main/java/com/iluwatar/command/Wizard.java

@@ -23,16 +23,13 @@
 
 package com.iluwatar.command;
 
+import java.util.Deque;
+import java.util.LinkedList;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.Deque;
-import java.util.LinkedList;
-
 /**
- * 
+ * Wizard is the invoker of the commands.
- * Wizard is the invoker of the commands
- *
  */
 public class Wizard {
 
@@ -46,7 +43,7 @@ public class Wizard {
   }
 
   /**
-   * Cast spell
+   * Cast spell.
    */
   public void castSpell(Command command, Target target) {
     LOGGER.info("{} casts {} at {}", this, command, target);
@@ -55,7 +52,7 @@ public class Wizard {
   }
 
   /**
-   * Undo last spell
+   * Undo last spell.
    */
   public void undoLastSpell() {
     if (!undoStack.isEmpty()) {
@@ -67,7 +64,7 @@ public class Wizard {
   }
 
   /**
-   * Redo last spell
+   * Redo last spell.
    */
   public void redoLastSpell() {
     if (!redoStack.isEmpty()) {

commander/src/main/java/com/iluwatar/commander/AppEmployeeDbFailCases.java

@@ -31,16 +31,15 @@ import com.iluwatar.commander.messagingservice.MessagingDatabase;
 import com.iluwatar.commander.messagingservice.MessagingService;
 import com.iluwatar.commander.paymentservice.PaymentDatabase;
 import com.iluwatar.commander.paymentservice.PaymentService;
+import com.iluwatar.commander.queue.QueueDatabase;
 import com.iluwatar.commander.shippingservice.ShippingDatabase;
 import com.iluwatar.commander.shippingservice.ShippingService;
-import com.iluwatar.commander.queue.QueueDatabase;
 
 /**
- * AppEmployeeDbFailCases class looks at possible cases when Employee handle service is 
+ * AppEmployeeDbFailCases class looks at possible cases when Employee handle service is
  * available/unavailable.
  */
-
+public class AppEmployeeDbFailCases {
-public class AppEmployeeDbFailCases { 
   final int numOfRetries = 3;
   final long retryDuration = 30000;
   final long queueTime = 240000; //4 mins
@@ -50,33 +49,40 @@ public class AppEmployeeDbFailCases {
   final long employeeTime = 240000; //4 mins
 
   void employeeDatabaseUnavailableCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());  
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
     MessagingService ms = new MessagingService(new MessagingDatabase());
-    EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase(), new DatabaseUnavailableException(), 
+    EmployeeHandle eh =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new EmployeeHandle(new EmployeeDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-    QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(), 
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
-        new DatabaseUnavailableException());
+    QueueDatabase qdb =
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+        new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException());
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
   }
 
   void employeeDbSuccessCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase());  
+    PaymentService ps = new PaymentService(new PaymentDatabase());
-    ShippingService ss = new ShippingService(new ShippingDatabase(), new ItemUnavailableException());
+    ShippingService ss =
+        new ShippingService(new ShippingDatabase(), new ItemUnavailableException());
     MessagingService ms = new MessagingService(new MessagingDatabase());
-    EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase(), new DatabaseUnavailableException(), 
+    EmployeeHandle eh =
-        new DatabaseUnavailableException());
+        new EmployeeHandle(new EmployeeDatabase(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -87,7 +93,7 @@ public class AppEmployeeDbFailCases {
    *
    * @param args command line args
    */
-  
+
   public static void main(String[] args) throws Exception {
     AppEmployeeDbFailCases aefc = new AppEmployeeDbFailCases();
     //aefc.employeeDatabaseUnavailableCase();

commander/src/main/java/com/iluwatar/commander/AppMessagingFailCases.java

@@ -30,12 +30,12 @@ import com.iluwatar.commander.messagingservice.MessagingDatabase;
 import com.iluwatar.commander.messagingservice.MessagingService;
 import com.iluwatar.commander.paymentservice.PaymentDatabase;
 import com.iluwatar.commander.paymentservice.PaymentService;
+import com.iluwatar.commander.queue.QueueDatabase;
 import com.iluwatar.commander.shippingservice.ShippingDatabase;
 import com.iluwatar.commander.shippingservice.ShippingService;
-import com.iluwatar.commander.queue.QueueDatabase;
 
 /**
- * AppMessagingFailCases class looks at possible cases when Messaging service is 
+ * AppMessagingFailCases class looks at possible cases when Messaging service is
  * available/unavailable.
  */
 
@@ -50,15 +50,17 @@ public class AppMessagingFailCases {
 
   void messagingDatabaseUnavailableCasePaymentSuccess() throws Exception {
     //rest is successful
-    PaymentService ps = new PaymentService(new PaymentDatabase());  
+    PaymentService ps = new PaymentService(new PaymentDatabase());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+    MessagingService ms =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -66,40 +68,52 @@ public class AppMessagingFailCases {
 
   void messagingDatabaseUnavailableCasePaymentError() throws Exception {
     //rest is successful
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());  
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+    MessagingService ms =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
   }
 
-  void messagingDatabaseUnavailableCasePaymentFailure() throws Exception { 
+  void messagingDatabaseUnavailableCasePaymentFailure() throws Exception {
     //rest is successful
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());  
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+    MessagingService ms =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
-    QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+    QueueDatabase qdb =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,queueTime,queueTaskTime,
+            new DatabaseUnavailableException(), new DatabaseUnavailableException());
-        paymentTime,messageTime,employeeTime);
+    Commander c =
+        new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration, queueTime, queueTaskTime,
+            paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -107,16 +121,19 @@ public class AppMessagingFailCases {
 
   void messagingSuccessCase() throws Exception {
     //done here
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());  
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+    MessagingService ms =
-        new DatabaseUnavailableException());
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -127,7 +144,7 @@ public class AppMessagingFailCases {
    *
    * @param args command line args
    */
-  
+
   public static void main(String[] args) throws Exception {
     AppMessagingFailCases amfc = new AppMessagingFailCases();
     //amfc.messagingDatabaseUnavailableCasePaymentSuccess();

commander/src/main/java/com/iluwatar/commander/AppPaymentFailCases.java

@@ -31,13 +31,12 @@ import com.iluwatar.commander.messagingservice.MessagingDatabase;
 import com.iluwatar.commander.messagingservice.MessagingService;
 import com.iluwatar.commander.paymentservice.PaymentDatabase;
 import com.iluwatar.commander.paymentservice.PaymentService;
+import com.iluwatar.commander.queue.QueueDatabase;
 import com.iluwatar.commander.shippingservice.ShippingDatabase;
 import com.iluwatar.commander.shippingservice.ShippingService;
-import com.iluwatar.commander.queue.QueueDatabase;
 
 /**
- * AppPaymentFailCases class looks at possible cases when Payment service is 
+ * AppPaymentFailCases class looks at possible cases when Payment service is available/unavailable.
- * available/unavailable.
  */
 
 public class AppPaymentFailCases {
@@ -50,14 +49,16 @@ public class AppPaymentFailCases {
   final long employeeTime = 240000; //4 mins
 
   void paymentNotPossibleCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new PaymentDetailsErrorException());  
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+            new PaymentDetailsErrorException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
+    MessagingService ms =
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException());
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -65,15 +66,17 @@ public class AppPaymentFailCases {
 
   void paymentDatabaseUnavailableCase() throws Exception {
     //rest is successful
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());  
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
     MessagingService ms = new MessagingService(new MessagingDatabase());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -81,14 +84,16 @@ public class AppPaymentFailCases {
 
   void paymentSuccessCase() throws Exception {
     //goes to message after 2 retries maybe - rest is successful for now
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException());  
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
+    MessagingService ms =
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException());
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -99,7 +104,7 @@ public class AppPaymentFailCases {
    *
    * @param args command line args
    */
-  
+
   public static void main(String[] args) throws Exception {
     AppPaymentFailCases apfc = new AppPaymentFailCases();
     //apfc.paymentNotPossibleCase();

commander/src/main/java/com/iluwatar/commander/AppQueueFailCases.java

@@ -31,13 +31,12 @@ import com.iluwatar.commander.messagingservice.MessagingDatabase;
 import com.iluwatar.commander.messagingservice.MessagingService;
 import com.iluwatar.commander.paymentservice.PaymentDatabase;
 import com.iluwatar.commander.paymentservice.PaymentService;
+import com.iluwatar.commander.queue.QueueDatabase;
 import com.iluwatar.commander.shippingservice.ShippingDatabase;
 import com.iluwatar.commander.shippingservice.ShippingService;
-import com.iluwatar.commander.queue.QueueDatabase;
 
 /**
- * AppQueueFailCases class looks at possible cases when Queue Database is 
+ * AppQueueFailCases class looks at possible cases when Queue Database is available/unavailable.
- * available/unavailable.
  */
 
 public class AppQueueFailCases {
@@ -50,71 +49,87 @@ public class AppQueueFailCases {
   final long employeeTime = 240000; //4 mins
 
   void queuePaymentTaskDatabaseUnavailableCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());  
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
     MessagingService ms = new MessagingService(new MessagingDatabase());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
-    QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+    QueueDatabase qdb =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+            new DatabaseUnavailableException(), new DatabaseUnavailableException());
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
   }
 
   void queueMessageTaskDatabaseUnavailableCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase());  
+    PaymentService ps = new PaymentService(new PaymentDatabase());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+    MessagingService ms =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
-    QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+    QueueDatabase qdb =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+            new DatabaseUnavailableException(), new DatabaseUnavailableException());
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
   }
 
   void queueEmployeeDbTaskDatabaseUnavailableCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase());  
+    PaymentService ps = new PaymentService(new PaymentDatabase());
-    ShippingService ss = new ShippingService(new ShippingDatabase(), new ItemUnavailableException());
+    ShippingService ss =
+        new ShippingService(new ShippingDatabase(), new ItemUnavailableException());
     MessagingService ms = new MessagingService(new MessagingDatabase());
-    EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase(), new DatabaseUnavailableException(),
+    EmployeeHandle eh =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new EmployeeHandle(new EmployeeDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-    QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(), 
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(), 
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(), 
+            new DatabaseUnavailableException());
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(), 
+    QueueDatabase qdb =
-        new DatabaseUnavailableException());
+        new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException());
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
   }
 
   void queueSuccessCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
+    PaymentService ps =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());  
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     ShippingService ss = new ShippingService(new ShippingDatabase());
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+    MessagingService ms =
-        new DatabaseUnavailableException());
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
-    QueueDatabase qdb = new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException());
+    QueueDatabase qdb =
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+        new QueueDatabase(new DatabaseUnavailableException(), new DatabaseUnavailableException());
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);

commander/src/main/java/com/iluwatar/commander/AppShippingFailCases.java

@@ -32,12 +32,12 @@ import com.iluwatar.commander.messagingservice.MessagingDatabase;
 import com.iluwatar.commander.messagingservice.MessagingService;
 import com.iluwatar.commander.paymentservice.PaymentDatabase;
 import com.iluwatar.commander.paymentservice.PaymentService;
+import com.iluwatar.commander.queue.QueueDatabase;
 import com.iluwatar.commander.shippingservice.ShippingDatabase;
 import com.iluwatar.commander.shippingservice.ShippingService;
-import com.iluwatar.commander.queue.QueueDatabase;
 
 /**
- * AppShippingFailCases class looks at possible cases when Shipping service is 
+ * AppShippingFailCases class looks at possible cases when Shipping service is
  * available/unavailable.
  */
 
@@ -51,26 +51,28 @@ public class AppShippingFailCases {
   final long employeeTime = 240000; //4 mins
 
   void itemUnavailableCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase());  
+    PaymentService ps = new PaymentService(new PaymentDatabase());
-    ShippingService ss = new ShippingService(new ShippingDatabase(), new ItemUnavailableException());
+    ShippingService ss =
+        new ShippingService(new ShippingDatabase(), new ItemUnavailableException());
     MessagingService ms = new MessagingService(new MessagingDatabase());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
   }
 
   void shippingNotPossibleCase() throws Exception {
-    PaymentService ps = new PaymentService(new PaymentDatabase());  
+    PaymentService ps = new PaymentService(new PaymentDatabase());
-    ShippingService ss = new ShippingService(new ShippingDatabase(), new ShippingNotPossibleException());
+    ShippingService ss =
+        new ShippingService(new ShippingDatabase(), new ShippingNotPossibleException());
     MessagingService ms = new MessagingService(new MessagingDatabase());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -78,15 +80,17 @@ public class AppShippingFailCases {
 
   void shippingDatabaseUnavailableCase() throws Exception {
     //rest is successful
-    PaymentService ps = new PaymentService(new PaymentDatabase());  
+    PaymentService ps = new PaymentService(new PaymentDatabase());
-    ShippingService ss = new ShippingService(new ShippingDatabase(), new DatabaseUnavailableException(),
+    ShippingService ss =
-        new DatabaseUnavailableException(), new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+        new ShippingService(new ShippingDatabase(), new DatabaseUnavailableException(),
-        new DatabaseUnavailableException(), new DatabaseUnavailableException());
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
     MessagingService ms = new MessagingService(new MessagingDatabase());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
@@ -94,25 +98,28 @@ public class AppShippingFailCases {
 
   void shippingSuccessCase() throws Exception {
     //goes to payment after 2 retries maybe - rest is successful for now
-    PaymentService ps = new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException());  
+    PaymentService ps =
-    ShippingService ss = new ShippingService(new ShippingDatabase(), new DatabaseUnavailableException(),
+        new PaymentService(new PaymentDatabase(), new DatabaseUnavailableException());
-        new DatabaseUnavailableException());
+    ShippingService ss =
-    MessagingService ms = new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
+        new ShippingService(new ShippingDatabase(), new DatabaseUnavailableException(),
+            new DatabaseUnavailableException());
+    MessagingService ms =
+        new MessagingService(new MessagingDatabase(), new DatabaseUnavailableException());
     EmployeeHandle eh = new EmployeeHandle(new EmployeeDatabase());
     QueueDatabase qdb = new QueueDatabase();
-    Commander c = new Commander(eh,ps,ss,ms,qdb,numOfRetries,retryDuration,
+    Commander c = new Commander(eh, ps, ss, ms, qdb, numOfRetries, retryDuration,
-        queueTime,queueTaskTime,paymentTime,messageTime,employeeTime);
+        queueTime, queueTaskTime, paymentTime, messageTime, employeeTime);
     User user = new User("Jim", "ABCD");
     Order order = new Order(user, "book", 10f);
     c.placeOrder(order);
   }
- 
+
   /**
    * Program entry point.
    *
    * @param args command line args
    */
-  
+
   public static void main(String[] args) throws Exception {
     AppShippingFailCases asfc = new AppShippingFailCases();
     //asfc.itemUnavailableCase();

commander/src/main/java/com/iluwatar/commander/Commander.java

@@ -23,53 +23,51 @@
 
 package com.iluwatar.commander;
 
-import java.util.ArrayList;
+import com.iluwatar.commander.Order.MessageSent;
+import com.iluwatar.commander.Order.PaymentStatus;
 import com.iluwatar.commander.employeehandle.EmployeeHandle;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 import com.iluwatar.commander.exceptions.ItemUnavailableException;
 import com.iluwatar.commander.exceptions.PaymentDetailsErrorException;
 import com.iluwatar.commander.exceptions.ShippingNotPossibleException;
 import com.iluwatar.commander.messagingservice.MessagingService;
-import com.iluwatar.commander.Order.MessageSent;
-import com.iluwatar.commander.Order.PaymentStatus;
 import com.iluwatar.commander.paymentservice.PaymentService;
 import com.iluwatar.commander.queue.QueueDatabase;
 import com.iluwatar.commander.queue.QueueTask;
 import com.iluwatar.commander.queue.QueueTask.TaskType;
 import com.iluwatar.commander.shippingservice.ShippingService;
+import java.util.ArrayList;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- *<p>Commander pattern is used to handle all issues that can come up while making a
+ * <p>Commander pattern is used to handle all issues that can come up while making a
- * distributed transaction. The idea is to have a commander, which coordinates the
+ * distributed transaction. The idea is to have a commander, which coordinates the execution of all
- * execution of all instructions and ensures proper completion using retries and
+ * instructions and ensures proper completion using retries and taking care of idempotence. By
- * taking care of idempotence. By queueing instructions while they haven't been done,
+ * queueing instructions while they haven't been done, we can ensure a state of 'eventual
- * we can ensure a state of 'eventual consistency'.</p>
+ * consistency'.</p>
  * <p>In our example, we have an e-commerce application. When the user places an order,
- * the shipping service is intimated first. If the service does not respond for some
+ * the shipping service is intimated first. If the service does not respond for some reason, the
- * reason, the order is not placed. If response is received, the commander then calls
+ * order is not placed. If response is received, the commander then calls for the payment service to
- * for the payment service to be intimated. If this fails, the shipping still takes
+ * be intimated. If this fails, the shipping still takes place (order converted to COD) and the item
- * place (order converted to COD) and the item is queued. If the queue is also found
+ * is queued. If the queue is also found to be unavailable, the payment is noted to be not done and
- * to be unavailable, the payment is noted to be not done and this is added to an
+ * this is added to an employee database. Three types of messages are sent to the user - one, if
- * employee database. Three types of messages are sent to the user - one, if payment
+ * payment succeeds; two, if payment fails definitively; and three, if payment fails in the first
- * succeeds; two, if payment fails definitively; and three, if payment fails in the
+ * attempt. If the message is not sent, this is also queued and is added to employee db. We also
- * first attempt. If the message is not sent, this is also queued and is added to employee
+ * have a time limit for each instruction to be completed, after which, the instruction is not
- * db. We also have a time limit for each instruction to be completed, after which, the
+ * executed, thereby ensuring that resources are not held for too long. In the rare occasion in
- * instruction is not executed, thereby ensuring that resources are not held for too long.
+ * which everything fails, an individual would have to step in to figure out how to solve the
- * In the rare occasion in which everything fails, an individual would have to step in to
+ * issue.</p>
- * figure out how to solve the issue.</p>
  * <p>We have abstract classes {@link Database} and {@link Service} which are extended
- * by all the databases and services. Each service has a database to be updated, and 
+ * by all the databases and services. Each service has a database to be updated, and receives
- * receives request from an outside user (the {@link Commander} class here). There are
+ * request from an outside user (the {@link Commander} class here). There are 5 microservices -
- * 5 microservices - {@link ShippingService}, {@link PaymentService}, {@link MessagingService},
+ * {@link ShippingService}, {@link PaymentService}, {@link MessagingService}, {@link EmployeeHandle}
- * {@link EmployeeHandle} and a {@link QueueDatabase}. We use retries to execute any
+ * and a {@link QueueDatabase}. We use retries to execute any instruction using {@link Retry} class,
- * instruction using {@link Retry} class, and idempotence is ensured by going through some
+ * and idempotence is ensured by going through some checks before making requests to services and
- * checks before making requests to services and making change in {@link Order} class fields
+ * making change in {@link Order} class fields if request succeeds or definitively fails. There are
- * if request succeeds or definitively fails. There are 5 classes - 
+ * 5 classes - {@link AppShippingFailCases}, {@link AppPaymentFailCases}, {@link
- * {@link AppShippingFailCases}, {@link AppPaymentFailCases}, {@link AppMessagingFailCases}, 
+ * AppMessagingFailCases}, {@link AppQueueFailCases} and {@link AppEmployeeDbFailCases}, which look
- * {@link AppQueueFailCases} and {@link AppEmployeeDbFailCases}, which look at the different
+ * at the different scenarios that may be encountered during the placing of an order.</p>
- * scenarios that may be encountered during the placing of an order.</p>
  */
 
 public class Commander {
@@ -86,17 +84,18 @@ public class Commander {
   private final long queueTaskTime;
   private final long paymentTime;
   private final long messageTime;
-  private final long employeeTime; 
+  private final long employeeTime;
   private boolean finalSiteMsgShown;
   static final Logger LOG = LoggerFactory.getLogger(Commander.class);
   //we could also have another db where it stores all orders
-  
+
-  Commander(EmployeeHandle empDb, PaymentService pService, ShippingService sService,
+  Commander(EmployeeHandle empDb, PaymentService paymentService, ShippingService shippingService,
-      MessagingService mService, QueueDatabase qdb, int numOfRetries, long retryDuration,
+            MessagingService messagingService, QueueDatabase qdb, int numOfRetries,
-      long queueTime, long queueTaskTime, long paymentTime, long messageTime, long employeeTime) {
+            long retryDuration, long queueTime, long queueTaskTime, long paymentTime,
-    this.paymentService = pService;
+            long messageTime, long employeeTime) {
-    this.shippingService = sService;
+    this.paymentService = paymentService;
-    this.messagingService = mService;
+    this.shippingService = shippingService;
+    this.messagingService = messagingService;
     this.employeeDb = empDb;
     this.queue = qdb;
     this.numOfRetries = numOfRetries;
@@ -106,7 +105,7 @@ public class Commander {
     this.paymentTime = paymentTime;
     this.messageTime = messageTime;
     this.employeeTime = employeeTime;
-    this.finalSiteMsgShown = false;   
+    this.finalSiteMsgShown = false;
   }
 
   void placeOrder(Order order) throws Exception {
@@ -118,40 +117,43 @@ public class Commander {
     Retry.Operation op = (l) -> {
       if (!l.isEmpty()) {
         if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-          LOG.debug("Order " + order.id + ": Error in connecting to shipping service, trying again..");
+          LOG.debug("Order " + order.id + ": Error in connecting to shipping service, "
+              + "trying again..");
         } else {
           LOG.debug("Order " + order.id + ": Error in creating shipping request..");
         }
         throw l.remove(0);
-      } 
+      }
-      String transactionId = shippingService.receiveRequest(order.item, order.user.address); 
+      String transactionId = shippingService.receiveRequest(order.item, order.user.address);
       //could save this transaction id in a db too
-      LOG.info("Order " + order.id + ": Shipping placed successfully, transaction id: " + transactionId);
+      LOG.info("Order " + order.id + ": Shipping placed successfully, transaction id: "
+          + transactionId);
       LOG.info("Order has been placed and will be shipped to you. Please wait while we make your"
-          + " payment... "); 
+          + " payment... ");
-      sendPaymentRequest(order);       
+      sendPaymentRequest(order);
-      return; 
+      return;
     };
-    Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
+    Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
       if (ShippingNotPossibleException.class.isAssignableFrom(err.getClass())) {
-        LOG.info("Shipping is currently not possible to your address. We are working on the problem "
+        LOG.info("Shipping is currently not possible to your address. We are working on the problem"
-            + "and will get back to you asap.");
+            + " and will get back to you asap.");
         finalSiteMsgShown = true;
-        LOG.info("Order " + order.id + ": Shipping not possible to address, trying to add problem to employee db..");
+        LOG.info("Order " + order.id + ": Shipping not possible to address, trying to add problem "
+            + "to employee db..");
         employeeHandleIssue(o);
       } else if (ItemUnavailableException.class.isAssignableFrom(err.getClass())) {
-        LOG.info("This item is currently unavailable. We will inform you as soon as the item becomes "
+        LOG.info("This item is currently unavailable. We will inform you as soon as the item "
-            + "available again.");
+            + "becomes available again.");
         finalSiteMsgShown = true;
-        LOG.info("Order " + order.id + ": Item " + order.item + " unavailable, trying to add problem to employee "
+        LOG.info("Order " + order.id + ": Item " + order.item + " unavailable, trying to add "
-            + "handle..");
+            + "problem to employee handle..");
         employeeHandleIssue(o);
       } else {
         LOG.info("Sorry, there was a problem in creating your order. Please try later.");
         LOG.error("Order " + order.id + ": Shipping service unavailable, order not placed..");
         finalSiteMsgShown = true;
       }
-      return; 
+      return;
     };
     Retry<Order> r = new Retry<Order>(op, handleError, numOfRetries, retryDuration,
         e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -174,28 +176,31 @@ public class Commander {
         Retry.Operation op = (l) -> {
           if (!l.isEmpty()) {
             if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-              LOG.debug("Order " + order.id + ": Error in connecting to payment service, trying again..");
+              LOG.debug("Order " + order.id + ": Error in connecting to payment service,"
+                  + " trying again..");
             } else {
               LOG.debug("Order " + order.id + ": Error in creating payment request..");
             }
-            throw l.remove(0); 
+            throw l.remove(0);
-          } 
+          }
           if (order.paid.equals(PaymentStatus.Trying)) {
             String transactionId = paymentService.receiveRequest(order.price);
-            order.paid = PaymentStatus.Done; 
+            order.paid = PaymentStatus.Done;
-            LOG.info("Order " + order.id + ": Payment successful, transaction Id: " + transactionId);
+            LOG.info("Order " + order.id + ": Payment successful, transaction Id: "
-            if (!finalSiteMsgShown) { 
+                + transactionId);
-              LOG.info("Payment made successfully, thank you for shopping with us!!"); 
+            if (!finalSiteMsgShown) {
-              finalSiteMsgShown = true; 
+              LOG.info("Payment made successfully, thank you for shopping with us!!");
-            } 
+              finalSiteMsgShown = true;
-            sendSuccessMessage(order); 
+            }
-            return; 
+            sendSuccessMessage(order);
-          } 
+            return;
+          }
         };
-        Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
+        Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
           if (PaymentDetailsErrorException.class.isAssignableFrom(err.getClass())) {
             if (!finalSiteMsgShown) {
-              LOG.info("There was an error in payment. Your account/card details may have been incorrect. "
+              LOG.info("There was an error in payment. Your account/card details "
+                  + "may have been incorrect. "
                   + "Meanwhile, your order has been converted to COD and will be shipped.");
               finalSiteMsgShown = true;
             }
@@ -213,15 +218,16 @@ public class Commander {
                 LOG.warn("Order " + order.id + ": Payment error, going to queue..");
                 sendPaymentPossibleErrorMsg(o);
               }
-              if (o.paid.equals(PaymentStatus.Trying) && System.currentTimeMillis() - o.createdTime < paymentTime) {
+              if (o.paid.equals(PaymentStatus.Trying) && System
-                QueueTask qt = new QueueTask(o, TaskType.Payment,-1);
+                  .currentTimeMillis() - o.createdTime < paymentTime) {
+                QueueTask qt = new QueueTask(o, TaskType.Payment, -1);
                 updateQueue(qt);
-              } 
+              }
             } catch (InterruptedException e1) {
               e1.printStackTrace();
-            } 
+            }
-          } 
+          }
-          return; 
+          return;
         };
         Retry<Order> r = new Retry<Order>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -229,7 +235,7 @@ public class Commander {
           r.perform(list, order);
         } catch (Exception e1) {
           e1.printStackTrace();
-        } 
+        }
       }
     });
     t.start();
@@ -237,17 +243,18 @@ public class Commander {
 
   private void updateQueue(QueueTask qt) throws InterruptedException {
     if (System.currentTimeMillis() - qt.order.createdTime >= this.queueTime) {
-      //since payment time is lesser than queuetime it would have already failed..additional check not needed
+      // since payment time is lesser than queuetime it would have already failed..
+      // additional check not needed
       LOG.trace("Order " + qt.order.id + ": Queue time for order over, failed..");
       return;
     } else if (qt.taskType.equals(TaskType.Payment) && !qt.order.paid.equals(PaymentStatus.Trying)
         || qt.taskType.equals(TaskType.Messaging) && (qt.messageType == 1
         && !qt.order.messageSent.equals(MessageSent.NoneSent)
-        || qt.order.messageSent.equals(MessageSent.PaymentFail) 
+        || qt.order.messageSent.equals(MessageSent.PaymentFail)
         || qt.order.messageSent.equals(MessageSent.PaymentSuccessful))
         || qt.taskType.equals(TaskType.EmployeeDb) && qt.order.addedToEmployeeHandle) {
       LOG.trace("Order " + qt.order.id + ": Not queueing task since task already done..");
-      return; 
+      return;
     }
     ArrayList<Exception> list = queue.exceptionsList;
     Thread t = new Thread(new Runnable() {
@@ -256,24 +263,25 @@ public class Commander {
         Retry.Operation op = (list) -> {
           if (!list.isEmpty()) {
             LOG.warn("Order " + qt.order.id + ": Error in connecting to queue db, trying again..");
-            throw list.remove(0); 
+            throw list.remove(0);
-          } 
+          }
-          queue.add(qt); 
+          queue.add(qt);
-          queueItems++; 
+          queueItems++;
           LOG.info("Order " + qt.order.id + ": " + qt.getType() + " task enqueued..");
           tryDoingTasksInQueue();
-          return;  
+          return;
         };
-        Retry.HandleErrorIssue<QueueTask> handleError = (qt,err) -> {
+        Retry.HandleErrorIssue<QueueTask> handleError = (qt, err) -> {
           if (qt.taskType.equals(TaskType.Payment)) {
-            qt.order.paid = PaymentStatus.NotDone; 
+            qt.order.paid = PaymentStatus.NotDone;
-            sendPaymentFailureMessage(qt.order); 
+            sendPaymentFailureMessage(qt.order);
-            LOG.error("Order " + qt.order.id + ": Unable to enqueue payment task, payment failed..");
+            LOG.error("Order " + qt.order.id + ": Unable to enqueue payment task,"
+                + " payment failed..");
           }
-          LOG.error("Order " + qt.order.id + ": Unable to enqueue task of type " + qt.getType() 
+          LOG.error("Order " + qt.order.id + ": Unable to enqueue task of type " + qt.getType()
               + ", trying to add to employee handle..");
           employeeHandleIssue(qt.order);
-          return; 
+          return;
         };
         Retry<QueueTask> r = new Retry<QueueTask>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -281,8 +289,8 @@ public class Commander {
           r.perform(list, qt);
         } catch (Exception e1) {
           e1.printStackTrace();
-        } 
+        }
-      } 
+      }
     });
     t.start();
   }
@@ -295,13 +303,13 @@ public class Commander {
         Retry.Operation op = (list) -> {
           if (!list.isEmpty()) {
             LOG.warn("Error in accessing queue db to do tasks, trying again..");
-            throw list.remove(0); 
+            throw list.remove(0);
           }
           doTasksInQueue();
-          return; 
+          return;
         };
-        Retry.HandleErrorIssue<QueueTask> handleError = (o,err) -> {
+        Retry.HandleErrorIssue<QueueTask> handleError = (o, err) -> {
-          return; 
+          return;
         };
         Retry<QueueTask> r = new Retry<QueueTask>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -309,8 +317,8 @@ public class Commander {
           r.perform(list, null);
         } catch (Exception e1) {
           e1.printStackTrace();
-        } 
+        }
-      } 
+      }
     });
     t2.start();
   }
@@ -323,14 +331,14 @@ public class Commander {
         Retry.Operation op = (list) -> {
           if (!list.isEmpty()) {
             LOG.warn("Error in accessing queue db to dequeue task, trying again..");
-            throw list.remove(0); 
+            throw list.remove(0);
-          } 
+          }
-          queue.dequeue(); 
+          queue.dequeue();
-          queueItems--; 
+          queueItems--;
           return;
         };
-        Retry.HandleErrorIssue<QueueTask> handleError = (o,err) -> {
+        Retry.HandleErrorIssue<QueueTask> handleError = (o, err) -> {
-          return; 
+          return;
         };
         Retry<QueueTask> r = new Retry<QueueTask>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -338,12 +346,12 @@ public class Commander {
           r.perform(list, null);
         } catch (Exception e1) {
           e1.printStackTrace();
-        } 
+        }
       }
     });
     t3.start();
   }
-  
+
   private void sendSuccessMessage(Order order) {
     if (System.currentTimeMillis() - order.createdTime >= this.messageTime) {
       LOG.trace("Order " + order.id + ": Message time for order over, returning..");
@@ -359,32 +367,35 @@ public class Commander {
               LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
                   + "(Payment Success msg), trying again..");
             } else {
-              LOG.debug("Order " + order.id + ": Error in creating Payment Success messaging request..");
+              LOG.debug("Order " + order.id + ": Error in creating Payment Success"
+                  + " messaging request..");
             }
-            throw l.remove(0); 
+            throw l.remove(0);
-          } 
+          }
-          if (!order.messageSent.equals(MessageSent.PaymentFail) 
+          if (!order.messageSent.equals(MessageSent.PaymentFail)
               && !order.messageSent.equals(MessageSent.PaymentSuccessful)) {
-            String requestId = messagingService.receiveRequest(2); 
+            String requestId = messagingService.receiveRequest(2);
             order.messageSent = MessageSent.PaymentSuccessful;
-            LOG.info("Order " + order.id + ": Payment Success message sent, request Id: " + requestId);
+            LOG.info("Order " + order.id + ": Payment Success message sent,"
-          } 
+                + " request Id: " + requestId);
-          return; 
+          }
+          return;
         };
-        Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
+        Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
           try {
-            if ((o.messageSent.equals(MessageSent.NoneSent) || o.messageSent.equals(MessageSent.PaymentTrying)) 
+            if ((o.messageSent.equals(MessageSent.NoneSent) || o.messageSent
+                .equals(MessageSent.PaymentTrying))
                 && System.currentTimeMillis() - o.createdTime < messageTime) {
-              QueueTask qt = new QueueTask(order, TaskType.Messaging,2);
+              QueueTask qt = new QueueTask(order, TaskType.Messaging, 2);
               updateQueue(qt);
-              LOG.info("Order " + order.id + ": Error in sending Payment Success message, trying to "
+              LOG.info("Order " + order.id + ": Error in sending Payment Success message, trying to"
-                  + "queue task and add to employee handle..");
+                  + " queue task and add to employee handle..");
               employeeHandleIssue(order);
             }
           } catch (InterruptedException e1) {
             e1.printStackTrace();
-          } 
+          }
-          return; 
+          return;
         };
         Retry<Order> r = new Retry<Order>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -392,8 +403,8 @@ public class Commander {
           r.perform(list, order);
         } catch (Exception e1) {
           e1.printStackTrace();
-        } 
+        }
-      } 
+      }
     });
     t.start();
   }
@@ -413,32 +424,35 @@ public class Commander {
               LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
                   + "(Payment Failure msg), trying again..");
             } else {
-              LOG.debug("Order " + order.id + ": Error in creating Payment Failure message request..");
+              LOG.debug("Order " + order.id + ": Error in creating Payment Failure"
+                  + " message request..");
             }
-            throw l.remove(0); 
+            throw l.remove(0);
-          } 
+          }
-          if (!order.messageSent.equals(MessageSent.PaymentFail) 
+          if (!order.messageSent.equals(MessageSent.PaymentFail)
-              && !order.messageSent.equals(MessageSent.PaymentSuccessful)) { 
+              && !order.messageSent.equals(MessageSent.PaymentSuccessful)) {
-            String requestId = messagingService.receiveRequest(0); 
+            String requestId = messagingService.receiveRequest(0);
             order.messageSent = MessageSent.PaymentFail;
-            LOG.info("Order " + order.id + ": Payment Failure message sent successfully, request Id: " + requestId);
+            LOG.info("Order " + order.id + ": Payment Failure message sent successfully,"
-          } 
+                + " request Id: " + requestId);
-          return; 
+          }
+          return;
         };
-        Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
+        Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
-          if ((o.messageSent.equals(MessageSent.NoneSent) || o.messageSent.equals(MessageSent.PaymentTrying))
+          if ((o.messageSent.equals(MessageSent.NoneSent) || o.messageSent
+              .equals(MessageSent.PaymentTrying))
               && System.currentTimeMillis() - o.createdTime < messageTime) {
             try {
-              QueueTask qt = new QueueTask(order, TaskType.Messaging,0);
+              QueueTask qt = new QueueTask(order, TaskType.Messaging, 0);
               updateQueue(qt);
               LOG.warn("Order " + order.id + ": Error in sending Payment Failure message, "
                   + "trying to queue task and add to employee handle..");
               employeeHandleIssue(o);
             } catch (InterruptedException e1) {
               e1.printStackTrace();
-            } 
+            }
-            return; 
+            return;
-          } 
+          }
         };
         Retry<Order> r = new Retry<Order>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -446,8 +460,8 @@ public class Commander {
           r.perform(list, order);
         } catch (Exception e1) {
           e1.printStackTrace();
-        } 
+        }
-      } 
+      }
     });
     t.start();
   }
@@ -467,31 +481,35 @@ public class Commander {
               LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
                   + "(Payment Error msg), trying again..");
             } else {
-              LOG.debug("Order " + order.id + ": Error in creating Payment Error messaging request..");
+              LOG.debug("Order " + order.id + ": Error in creating Payment Error"
+                  + " messaging request..");
             }
-            throw l.remove(0); 
+            throw l.remove(0);
           }
-          if (order.paid.equals(PaymentStatus.Trying) && order.messageSent.equals(MessageSent.NoneSent)) {
+          if (order.paid.equals(PaymentStatus.Trying) && order.messageSent
-            String requestId = messagingService.receiveRequest(1); 
+              .equals(MessageSent.NoneSent)) {
-            order.messageSent = MessageSent.PaymentTrying; 
+            String requestId = messagingService.receiveRequest(1);
-            LOG.info("Order " + order.id + ": Payment Error message sent successfully, request Id: " + requestId);
+            order.messageSent = MessageSent.PaymentTrying;
-          } 
+            LOG.info("Order " + order.id + ": Payment Error message sent successfully,"
-          return; 
+                + " request Id: " + requestId);
+          }
+          return;
         };
-        Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
+        Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
           try {
-            if (o.messageSent.equals(MessageSent.NoneSent) && order.paid.equals(PaymentStatus.Trying)
+            if (o.messageSent.equals(MessageSent.NoneSent) && order.paid
+                .equals(PaymentStatus.Trying)
                 && System.currentTimeMillis() - o.createdTime < messageTime) {
-              QueueTask qt = new QueueTask(order,TaskType.Messaging,1);
+              QueueTask qt = new QueueTask(order, TaskType.Messaging, 1);
               updateQueue(qt);
               LOG.warn("Order " + order.id + ": Error in sending Payment Error message, "
                   + "trying to queue task and add to employee handle..");
               employeeHandleIssue(o);
-            } 
+            }
           } catch (InterruptedException e1) {
             e1.printStackTrace();
-          } 
+          }
-          return; 
+          return;
         };
         Retry<Order> r = new Retry<Order>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -516,28 +534,31 @@ public class Commander {
       public void run() {
         Retry.Operation op = (l) -> {
           if (!l.isEmpty()) {
-            LOG.warn("Order " + order.id + ": Error in connecting to employee handle, trying again..");
+            LOG.warn("Order " + order.id + ": Error in connecting to employee handle,"
-            throw l.remove(0); 
+                + " trying again..");
-          } 
+            throw l.remove(0);
+          }
           if (!order.addedToEmployeeHandle) {
-            employeeDb.receiveRequest(order); 
+            employeeDb.receiveRequest(order);
             order.addedToEmployeeHandle = true;
             LOG.info("Order " + order.id + ": Added order to employee database");
           }
-          return; 
+          return;
         };
-        Retry.HandleErrorIssue<Order> handleError = (o,err) -> {
+        Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
           try {
-            if (!o.addedToEmployeeHandle && System.currentTimeMillis() - order.createdTime < employeeTime) {
+            if (!o.addedToEmployeeHandle && System
-              QueueTask qt = new QueueTask(order, TaskType.EmployeeDb,-1);
+                .currentTimeMillis() - order.createdTime < employeeTime) {
+              QueueTask qt = new QueueTask(order, TaskType.EmployeeDb, -1);
               updateQueue(qt);
-              LOG.warn("Order " + order.id + ": Error in adding to employee db, trying to queue task..");
+              LOG.warn("Order " + order.id + ": Error in adding to employee db,"
+                  + " trying to queue task..");
               return;
-            } 
+            }
           } catch (InterruptedException e1) {
             e1.printStackTrace();
           }
-          return; 
+          return;
         };
         Retry<Order> r = new Retry<Order>(op, handleError, numOfRetries, retryDuration,
             e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -558,7 +579,7 @@ public class Commander {
       LOG.trace("Order " + qt.order.id + ": Started doing task of type " + qt.getType());
       if (qt.firstAttemptTime == -1) {
         qt.firstAttemptTime = System.currentTimeMillis();
-      } 
+      }
       if (System.currentTimeMillis() - qt.firstAttemptTime >= queueTaskTime) {
         tryDequeue();
         LOG.trace("Order " + qt.order.id + ": This queue task of type " + qt.getType()
@@ -573,14 +594,15 @@ public class Commander {
             LOG.debug("Order " + qt.order.id + ": Trying to connect to payment service..");
           }
         } else if (qt.taskType.equals(TaskType.Messaging)) {
-          if (qt.order.messageSent.equals(MessageSent.PaymentFail) 
+          if (qt.order.messageSent.equals(MessageSent.PaymentFail)
               || qt.order.messageSent.equals(MessageSent.PaymentSuccessful)) {
             tryDequeue();
             LOG.trace("Order " + qt.order.id + ": This messaging task already done, dequeue..");
           } else if (qt.messageType == 1 && (!qt.order.messageSent.equals(MessageSent.NoneSent)
               || !qt.order.paid.equals(PaymentStatus.Trying))) {
             tryDequeue();
-            LOG.trace("Order " + qt.order.id + ": This messaging task does not need to be done, dequeue..");
+            LOG.trace("Order " + qt.order.id + ": This messaging task does not need to be done,"
+                + " dequeue..");
           } else if (qt.messageType == 0) {
             sendPaymentFailureMessage(qt.order);
             LOG.debug("Order " + qt.order.id + ": Trying to connect to messaging service..");
@@ -594,7 +616,8 @@ public class Commander {
         } else if (qt.taskType.equals(TaskType.EmployeeDb)) {
           if (qt.order.addedToEmployeeHandle) {
             tryDequeue();
-            LOG.trace("Order " + qt.order.id + ": This employee handle task already done, dequeue..");
+            LOG.trace("Order " + qt.order.id + ": This employee handle task already done,"
+                + " dequeue..");
           } else {
             employeeHandleIssue(qt.order);
             LOG.debug("Order " + qt.order.id + ": Trying to connect to employee handle..");

commander/src/main/java/com/iluwatar/commander/Database.java

@@ -26,12 +26,14 @@ package com.iluwatar.commander;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 
 /**
- * Database abstract class is extended by all databases in our example. The add and get
+ * Database abstract class is extended by all databases in our example. The add and get methods are
- * methods are used by the respective service to add to database or get from database.
+ * used by the respective service to add to database or get from database.
+ *
  * @param <T> T is the type of object being held by database.
  */
 
 public abstract class Database<T> {
   public abstract T add(T obj) throws DatabaseUnavailableException;
-  public abstract T get(String tId) throws DatabaseUnavailableException;
+
+  public abstract T get(String id) throws DatabaseUnavailableException;
 }

commander/src/main/java/com/iluwatar/commander/Order.java

@@ -34,11 +34,15 @@ public class Order { //can store all transactions ids also
 
   enum PaymentStatus {
     NotDone, Trying, Done
-  };
+  }
-  
+
+  ;
+
   enum MessageSent {
     NoneSent, PaymentFail, PaymentTrying, PaymentSuccessful
-  };
+  }
+
+  ;
 
   final User user;
   final String item;
@@ -78,5 +82,5 @@ public class Order { //can store all transactions ids also
     }
     return random.toString();
   }
-  
+
 }

commander/src/main/java/com/iluwatar/commander/Retry.java

@@ -30,29 +30,31 @@ import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Predicate;
 
 /**
- * Retry pattern 
+ * Retry pattern.
+ *
  * @param <T> is the type of object passed into HandleErrorIssue as a parameter.
  */
 
 public class Retry<T> {
 
- /**
+  /**
-  * Operation Interface will define method to be implemented. 
+   * Operation Interface will define method to be implemented.
-  */
+   */
 
   public interface Operation {
-    void operation(ArrayList<Exception> list) throws Exception; 
+    void operation(ArrayList<Exception> list) throws Exception;
   }
 
- /**
+  /**
-  * HandleErrorIssue defines how to handle errors.
+   * HandleErrorIssue defines how to handle errors.
-  * @param <T> is the type of object to be passed into the method as parameter.
+   *
-  */
+   * @param <T> is the type of object to be passed into the method as parameter.
-  
+   */
+
   public interface HandleErrorIssue<T> {
     void handleIssue(T obj, Exception e);
   }
-  
+
   private static final Random RANDOM = new Random();
 
   private final Operation op;
@@ -64,7 +66,7 @@ public class Retry<T> {
   private final ArrayList<Exception> errors;
 
   Retry(Operation op, HandleErrorIssue handleError, int maxAttempts,
-      long maxDelay, Predicate<Exception>... ignoreTests) {
+        long maxDelay, Predicate<Exception>... ignoreTests) {
     this.op = op;
     this.handleError = handleError;
     this.maxAttempts = maxAttempts;
@@ -76,10 +78,11 @@ public class Retry<T> {
 
   /**
    * Performing the operation with retries.
+   *
    * @param list is the exception list
-   * @param obj is the parameter to be passed into handleIsuue method
+   * @param obj  is the parameter to be passed into handleIsuue method
    */
-  
+
   public void perform(ArrayList<Exception> list, T obj) throws Exception {
     do {
       try {
@@ -92,15 +95,15 @@ public class Retry<T> {
           return; //return here...dont go further
         }
         try {
-          long testDelay = (long) Math.pow(2, this.attempts.intValue()) * 1000 + RANDOM.nextInt(1000);
+          long testDelay =
+              (long) Math.pow(2, this.attempts.intValue()) * 1000 + RANDOM.nextInt(1000);
           long delay = testDelay < this.maxDelay ? testDelay : maxDelay;
           Thread.sleep(delay);
         } catch (InterruptedException f) {
           //ignore
         }
       }
-    }
+    } while (true);
-    while (true);
   }
 
 }

commander/src/main/java/com/iluwatar/commander/Service.java

@@ -23,35 +23,37 @@
 
 package com.iluwatar.commander;
 
-import java.util.*;
-
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
+import java.util.ArrayList;
+import java.util.Hashtable;
+import java.util.List;
+import java.util.Random;
 
 /**
- * Service class is an abstract class extended by all services in this example. They
+ * Service class is an abstract class extended by all services in this example. They all have a
- * all have a public receiveRequest method to receive requests, which could also contain
+ * public receiveRequest method to receive requests, which could also contain details of the user
- * details of the user other than the implementation details (though we are not doing
+ * other than the implementation details (though we are not doing that here) and updateDb method
- * that here) and updateDb method which adds to their respective databases. There is a
+ * which adds to their respective databases. There is a method to generate transaction/request id
- * method to generate transaction/request id for the transactions/requests, which are
+ * for the transactions/requests, which are then sent back. These could be stored by the {@link
- * then sent back. These could be stored by the {@link Commander} class in a separate
+ * Commander} class in a separate database for reference (though we are not doing that here).
- * database for reference (though we are not doing that here).
  */
 
 public abstract class Service {
-  
+
   protected final Database database;
   public ArrayList<Exception> exceptionsList;
   private static final Random RANDOM = new Random();
   private static final String ALL_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
   private static final Hashtable<String, Boolean> USED_IDS = new Hashtable<>();
 
-  protected Service(Database db, Exception...exc) {
+  protected Service(Database db, Exception... exc) {
     this.database = db;
     this.exceptionsList = new ArrayList<>(List.of(exc));
   }
 
-  public abstract String receiveRequest(Object...parameters) throws DatabaseUnavailableException;
+  public abstract String receiveRequest(Object... parameters) throws DatabaseUnavailableException;
-  protected abstract String updateDb(Object...parameters) throws DatabaseUnavailableException;
+
+  protected abstract String updateDb(Object... parameters) throws DatabaseUnavailableException;
 
   protected String generateId() {
     StringBuilder random = new StringBuilder();

commander/src/main/java/com/iluwatar/commander/employeehandle/EmployeeDatabase.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.commander.employeehandle;
 
-import java.util.Hashtable;
 import com.iluwatar.commander.Database;
 import com.iluwatar.commander.Order;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
+import java.util.Hashtable;
 
 /**
  * The Employee Database is where orders which have encountered some issue(s) are added.
@@ -41,11 +41,11 @@ public class EmployeeDatabase extends Database<Order> {
 
   @Override
   public Order add(Order o) throws DatabaseUnavailableException {
-    return data.put(o.id,o);
+    return data.put(o.id, o);
   }
 
   @Override
-  public Order get(String oId) throws DatabaseUnavailableException {
+  public Order get(String orderId) throws DatabaseUnavailableException {
-    return data.get(oId);
+    return data.get(orderId);
   }
 }

commander/src/main/java/com/iluwatar/commander/employeehandle/EmployeeHandle.java

@@ -28,21 +28,21 @@ import com.iluwatar.commander.Service;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 
 /**
- * The EmployeeHandle class is the middle-man between {@link Commander} and 
+ * The EmployeeHandle class is the middle-man between {@link Commander} and {@link
- * {@link EmployeeDatabase}.
+ * EmployeeDatabase}.
  */
 
 public class EmployeeHandle extends Service {
 
-  public EmployeeHandle(EmployeeDatabase db, Exception...exc) {
+  public EmployeeHandle(EmployeeDatabase db, Exception... exc) {
     super(db, exc);
   }
 
-  public String receiveRequest(Object...parameters) throws DatabaseUnavailableException {
+  public String receiveRequest(Object... parameters) throws DatabaseUnavailableException {
-    return updateDb((Order)parameters[0]);
+    return updateDb((Order) parameters[0]);
   }
 
-  protected String updateDb(Object...parameters) throws DatabaseUnavailableException {
+  protected String updateDb(Object... parameters) throws DatabaseUnavailableException {
     Order o = (Order) parameters[0];
     if (database.get(o.id) == null) {
       database.add(o);

commander/src/main/java/com/iluwatar/commander/exceptions/DatabaseUnavailableException.java

@@ -24,8 +24,8 @@
 package com.iluwatar.commander.exceptions;
 
 /**
- * DatabaseUnavailableException is thrown when database is unavailable and nothing
+ * DatabaseUnavailableException is thrown when database is unavailable and nothing can be added or
- * can be added or retrieved.
+ * retrieved.
  */
 
 public class DatabaseUnavailableException extends Exception {

commander/src/main/java/com/iluwatar/commander/exceptions/PaymentDetailsErrorException.java

@@ -24,8 +24,8 @@
 package com.iluwatar.commander.exceptions;
 
 /**
- * PaymentDetailsErrorException is thrown when the details entered are incorrect or
+ * PaymentDetailsErrorException is thrown when the details entered are incorrect or payment cannot
- * payment cannot be made with the details given.
+ * be made with the details given.
  */
 
 public class PaymentDetailsErrorException extends Exception {

commander/src/main/java/com/iluwatar/commander/exceptions/ShippingNotPossibleException.java

@@ -24,8 +24,8 @@
 package com.iluwatar.commander.exceptions;
 
 /**
- * ShippingNotPossibleException is thrown when the address entered cannot be shipped to
+ * ShippingNotPossibleException is thrown when the address entered cannot be shipped to by service
- * by service currently for some reason.
+ * currently for some reason.
  */
 
 public class ShippingNotPossibleException extends Exception {

commander/src/main/java/com/iluwatar/commander/messagingservice/MessagingDatabase.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.commander.messagingservice;
 
-import java.util.Hashtable;
 import com.iluwatar.commander.Database;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 import com.iluwatar.commander.messagingservice.MessagingService.MessageRequest;
+import java.util.Hashtable;
 
 /**
  * The MessagingDatabase is where the MessageRequest is added.
@@ -45,8 +45,8 @@ public class MessagingDatabase extends Database<MessageRequest> {
   }
 
   @Override
-  public MessageRequest get(String rId) throws DatabaseUnavailableException {
+  public MessageRequest get(String requestId) throws DatabaseUnavailableException {
-    return data.get(rId);
+    return data.get(requestId);
   }
 
 }

commander/src/main/java/com/iluwatar/commander/messagingservice/MessagingService.java

@@ -29,9 +29,9 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * The MessagingService is used to send messages to user regarding their order and 
+ * The MessagingService is used to send messages to user regarding their order and payment status.
- * payment status. In case an error is encountered in payment and this service is
+ * In case an error is encountered in payment and this service is found to be unavailable, the order
- * found to be unavailable, the order is added to the {@link EmployeeDatabase}.
+ * is added to the {@link EmployeeDatabase}.
  */
 
 public class MessagingService extends Service {
@@ -39,7 +39,9 @@ public class MessagingService extends Service {
 
   enum MessageToSend {
     PaymentFail, PaymentTrying, PaymentSuccessful
-  };
+  }
+
+  ;
 
   class MessageRequest {
     String reqId;
@@ -51,17 +53,16 @@ public class MessagingService extends Service {
     }
   }
 
-  public MessagingService(MessagingDatabase db, Exception...exc) {
+  public MessagingService(MessagingDatabase db, Exception... exc) {
     super(db, exc);
   }
 
   /**
    * Public method which will receive request from {@link Commander}.
    */
-  
+  public String receiveRequest(Object... parameters) throws DatabaseUnavailableException {
-  public String receiveRequest(Object...parameters) throws DatabaseUnavailableException {
     int messageToSend = (int) parameters[0];
-    String rId = generateId();
+    String id = generateId();
     MessageToSend msg = null;
     if (messageToSend == 0) {
       msg = MessageToSend.PaymentFail;
@@ -70,11 +71,11 @@ public class MessagingService extends Service {
     } else { //messageToSend == 2
       msg = MessageToSend.PaymentSuccessful;
     }
-    MessageRequest req = new MessageRequest(rId, msg);
+    MessageRequest req = new MessageRequest(id, msg);
     return updateDb(req);
   }
 
-  protected String updateDb(Object...parameters) throws DatabaseUnavailableException {
+  protected String updateDb(Object... parameters) throws DatabaseUnavailableException {
     MessageRequest req = (MessageRequest) parameters[0];
     if (this.database.get(req.reqId) == null) { //idempotence, in case db fails here
       database.add(req); //if successful:
@@ -86,13 +87,17 @@ public class MessagingService extends Service {
 
   String sendMessage(MessageToSend m) {
     if (m.equals(MessageToSend.PaymentSuccessful)) {
-      return "Msg: Your order has been placed and paid for successfully! Thank you for shopping with us!";
+      return "Msg: Your order has been placed and paid for successfully!"
+          + " Thank you for shopping with us!";
     } else if (m.equals(MessageToSend.PaymentTrying)) {
-      return "Msg: There was an error in your payment process, we are working on it and will return back to you"
+      return "Msg: There was an error in your payment process,"
-          + " shortly. Meanwhile, your order has been placed and will be shipped.";
+          + " we are working on it and will return back to you shortly."
+          + " Meanwhile, your order has been placed and will be shipped.";
     } else {
-      return "Msg: There was an error in your payment process. Your order is placed and has been converted to COD."
+      return "Msg: There was an error in your payment process."
-          + " Please reach us on CUSTOMER-CARE-NUBER in case of any queries. Thank you for shopping with us!";
+          + " Your order is placed and has been converted to COD."
+          + " Please reach us on CUSTOMER-CARE-NUBER in case of any queries."
+          + " Thank you for shopping with us!";
     }
   }
 }

commander/src/main/java/com/iluwatar/commander/paymentservice/PaymentDatabase.java

@@ -23,11 +23,10 @@
 
 package com.iluwatar.commander.paymentservice;
 
-import java.util.Hashtable;
-
 import com.iluwatar.commander.Database;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 import com.iluwatar.commander.paymentservice.PaymentService.PaymentRequest;
+import java.util.Hashtable;
 
 /**
  * PaymentDatabase is where the PaymentRequest is added, along with details.
@@ -48,8 +47,8 @@ public class PaymentDatabase extends Database<PaymentRequest> {
   }
 
   @Override
-  public PaymentRequest get(String tId) throws DatabaseUnavailableException {
+  public PaymentRequest get(String requestId) throws DatabaseUnavailableException {
-    return data.get(tId);
+    return data.get(requestId);
   }
 
 }

commander/src/main/java/com/iluwatar/commander/paymentservice/PaymentService.java

@@ -27,8 +27,8 @@ import com.iluwatar.commander.Service;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 
 /**
- * The PaymentService class receives request from the {@link Commander} and adds
+ * The PaymentService class receives request from the {@link Commander} and adds to the {@link
- * to the {@link PaymentDatabase}.
+ * PaymentDatabase}.
  */
 
 public class PaymentService extends Service {
@@ -45,22 +45,22 @@ public class PaymentService extends Service {
     }
   }
 
-  public PaymentService(PaymentDatabase db, Exception...exc) {
+  public PaymentService(PaymentDatabase db, Exception... exc) {
     super(db, exc);
   }
 
   /**
    * Public method which will receive request from {@link Commander}.
    */
-  
+
-  public String receiveRequest(Object...parameters) throws DatabaseUnavailableException {
+  public String receiveRequest(Object... parameters) throws DatabaseUnavailableException {
     //it could also be sending a userid, payment details here or something, not added here
-    String tId = generateId();
+    String id = generateId();
-    PaymentRequest req = new PaymentRequest(tId, (float)parameters[0]);
+    PaymentRequest req = new PaymentRequest(id, (float) parameters[0]);
     return updateDb(req);
   }
 
-  protected String updateDb(Object...parameters) throws DatabaseUnavailableException {
+  protected String updateDb(Object... parameters) throws DatabaseUnavailableException {
     PaymentRequest req = (PaymentRequest) parameters[0];
     if (database.get(req.transactionId) == null || !req.paid) {
       database.add(req);

commander/src/main/java/com/iluwatar/commander/queue/Queue.java

@@ -27,6 +27,7 @@ import com.iluwatar.commander.exceptions.IsEmptyException;
 
 /**
  * Queue data structure implementation.
+ *
  * @param <T> is the type of object the queue will hold.
  */
 
@@ -47,15 +48,14 @@ public class Queue<T> {
   }
 
   /**
-   * Queue constructor
+   * Queue constructor.
    */
-  
   Queue() {
     front = null;
     rear = null;
     size = 0;
   }
-  
+
   boolean isEmpty() {
     if (size == 0) {
       return true;
@@ -63,7 +63,7 @@ public class Queue<T> {
       return false;
     }
   }
-  
+
   void enqueue(T obj) {
     if (front == null) {
       front = new Node(obj, null);
@@ -75,7 +75,7 @@ public class Queue<T> {
     }
     size++;
   }
-  
+
   T dequeue() throws IsEmptyException {
     if (isEmpty()) {
       throw new IsEmptyException();
@@ -86,12 +86,12 @@ public class Queue<T> {
       return (T) temp.value;
     }
   }
-  
+
   T peek() throws IsEmptyException {
     if (isEmpty()) {
       throw new IsEmptyException();
     } else {
-      return (T)front.value;
+      return (T) front.value;
     }
   }
 }

commander/src/main/java/com/iluwatar/commander/queue/QueueDatabase.java

@@ -26,7 +26,6 @@ package com.iluwatar.commander.queue;
 import com.iluwatar.commander.Database;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 import com.iluwatar.commander.exceptions.IsEmptyException;
-
 import java.util.ArrayList;
 import java.util.List;
 
@@ -39,7 +38,7 @@ public class QueueDatabase extends Database<QueueTask> {
   private Queue<QueueTask> data;
   public ArrayList<Exception> exceptionsList;
 
-  public QueueDatabase(Exception...exc) {
+  public QueueDatabase(Exception... exc) {
     this.data = new Queue<>();
     this.exceptionsList = new ArrayList<>(List.of(exc));
   }
@@ -52,31 +51,33 @@ public class QueueDatabase extends Database<QueueTask> {
   }
 
   /**
-   * peek method returns object at front without removing it from queue
+   * peek method returns object at front without removing it from queue.
+   *
    * @return object at front of queue
-   * @throws IsEmptyException if queue is empty
+   * @throws IsEmptyException             if queue is empty
    * @throws DatabaseUnavailableException if queue db is unavailable
    */
-  
+
   public QueueTask peek() throws IsEmptyException, DatabaseUnavailableException {
     QueueTask qt = this.data.peek();
     return qt;
   }
 
   /**
-   * dequeue method removes the object at front and returns it
+   * dequeue method removes the object at front and returns it.
+   *
    * @return object at front of queue
-   * @throws IsEmptyException if queue is empty
+   * @throws IsEmptyException             if queue is empty
    * @throws DatabaseUnavailableException if queue db is unavailable
    */
-  
+
   public QueueTask dequeue() throws IsEmptyException, DatabaseUnavailableException {
     QueueTask qt = this.data.dequeue();
     return qt;
   }
 
   @Override
-  public QueueTask get(String tId) throws DatabaseUnavailableException {
+  public QueueTask get(String taskId) throws DatabaseUnavailableException {
     return null;
   }
 

commander/src/main/java/com/iluwatar/commander/queue/QueueTask.java

@@ -31,13 +31,15 @@ import com.iluwatar.commander.Order;
 
 public class QueueTask {
 
-/**
+  /**
- * TaskType is the type of task to be done.
+   * TaskType is the type of task to be done.
- */
+   */
 
   public enum TaskType {
     Messaging, Payment, EmployeeDb
-  };
+  }
+
+  ;
 
   public Order order;
   public TaskType taskType;
@@ -46,26 +48,28 @@ public class QueueTask {
   but keeping it simple here*/
   public long firstAttemptTime; //when first time attempt made to do task
 
-/**
+  /**
- * QueueTask constructor
+   * QueueTask constructor.
- * @param o is the order for which the queuetask is being created
+   *
- * @param t is the type of task to be done
+   * @param o           is the order for which the queuetask is being created
- * @param messageType if it is a message, which type of message - this could have instead been object varargs,
+   * @param t           is the type of task to be done
- *     and contained all additional details related to tasktype.
+   * @param messageType if it is a message, which type of message - this could have instead been
- */
+   *                    object varargs, and contained all additional details related to tasktype.
-  
+   */
+
   public QueueTask(Order o, TaskType t, int messageType) {
     this.order = o;
     this.taskType = t;
     this.messageType = messageType;
     this.firstAttemptTime = -1;
   }
-  
+
   /**
-   * getType method 
+   * getType method.
+   *
    * @return String representing type of task
    */
-  
+
   public String getType() {
     if (!this.taskType.equals(TaskType.Messaging)) {
       return this.taskType.toString();

commander/src/main/java/com/iluwatar/commander/shippingservice/ShippingDatabase.java

@@ -23,17 +23,17 @@
 
 package com.iluwatar.commander.shippingservice;
 
-import java.util.Hashtable;
 import com.iluwatar.commander.Database;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 import com.iluwatar.commander.shippingservice.ShippingService.ShippingRequest;
+import java.util.Hashtable;
 
 /**
  * ShippingDatabase is where the ShippingRequest objects are added.
  */
 
 public class ShippingDatabase extends Database<ShippingRequest> {
-  
+
   private Hashtable<String, ShippingRequest> data;
 
   public ShippingDatabase() {
@@ -45,8 +45,8 @@ public class ShippingDatabase extends Database<ShippingRequest> {
     return data.put(r.transactionId, r);
   }
 
-  public ShippingRequest get(String transactionId) throws DatabaseUnavailableException {
+  public ShippingRequest get(String trasnactionId) throws DatabaseUnavailableException {
-    return data.get(transactionId);
+    return data.get(trasnactionId);
   }
 
 }

commander/src/main/java/com/iluwatar/commander/shippingservice/ShippingService.java

@@ -27,8 +27,8 @@ import com.iluwatar.commander.Service;
 import com.iluwatar.commander.exceptions.DatabaseUnavailableException;
 
 /**
- * ShippingService class receives request from {@link Commander} class and adds it
+ * ShippingService class receives request from {@link Commander} class and adds it to the {@link
- * to the {@link ShippingDatabase}.
+ * ShippingDatabase}.
  */
 
 public class ShippingService extends Service {
@@ -45,21 +45,22 @@ public class ShippingService extends Service {
     }
   }
 
-  public ShippingService(ShippingDatabase db, Exception...exc) {
+  public ShippingService(ShippingDatabase db, Exception... exc) {
     super(db, exc);
   }
 
   /**
    * Public method which will receive request from {@link Commander}.
    */
-  
+
-  public String receiveRequest(Object...parameters) throws DatabaseUnavailableException {
+  public String receiveRequest(Object... parameters) throws DatabaseUnavailableException {
-    String tId = generateId();
+    String id = generateId();
-    ShippingRequest req = new ShippingRequest(tId, (String) parameters[0] /*item*/, (String) parameters[1]/*address*/);
+    ShippingRequest req =
+        new ShippingRequest(id, (String) parameters[0] /*item*/, (String) parameters[1]/*address*/);
     return updateDb(req);
   }
 
-  protected String updateDb(Object...parameters) throws DatabaseUnavailableException {
+  protected String updateDb(Object... parameters) throws DatabaseUnavailableException {
     ShippingRequest req = (ShippingRequest) parameters[0];
     if (this.database.get(req.transactionId) == null) {
       database.add(req);