Java 11 migrate c-d (remaining) (#1111)

* Moves converter pattern to Java 11

* Moves cqrs pattern to Java 11

* Moves dao pattern to Java 11

* Moves data-bus pattern to Java 11

* Moves data-locality pattern to Java 11

* Moves data-mapper pattern to Java 11

* Moves data-transfer-object pattern to Java 11

* Moves decorator pattern to Java 11

* Moves delegation pattern to Java 11

* Moves dependency-injection to Java 11

* Moves dirty-flag to Java 11

* Moves double-buffer to Java 11

* Moves double-checked-locking to Java 11

* Moves double-dispatch to Java 11

* Corrects with changes thats breaking test cases

converter/README.md

@@ -63,20 +63,26 @@ The specialized converters inherit from this base class as follows.
 public class UserConverter extends Converter<UserDto, User> {
 
   public UserConverter() {
-    super(userDto -> new User(userDto.getFirstName(), userDto.getLastName(), userDto.isActive(),
+    super(UserConverter::convertToEntity, UserConverter::convertToDto);
-            userDto.getEmail()),
-        user -> new UserDto(user.getFirstName(), user.getLastName(), user.isActive(),
-            user.getUserId()));
   }
+
+  private static UserDto convertToDto(User user) {
+    return new UserDto(user.getFirstName(), user.getLastName(), user.isActive(), user.getUserId());
+  }
+
+  private static User convertToEntity(UserDto dto) {
+    return new User(dto.getFirstName(), dto.getLastName(), dto.isActive(), dto.getEmail());
+  }
+
 }
 ```
 
 Now mapping between User and UserDto becomes trivial.
 
 ```java
-Converter<UserDto, User> userConverter = new UserConverter();
+var userConverter = new UserConverter();
-UserDto dtoUser = new UserDto("John", "Doe", true, "whatever[at]wherever.com");
+var dtoUser = new UserDto("John", "Doe", true, "whatever[at]wherever.com");
-User user = userConverter.convertFromDto(dtoUser);
+var user = userConverter.convertFromDto(dtoUser);
 ```
 
 ## Class diagram

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

@@ -49,8 +49,11 @@ public class App {
     User user = userConverter.convertFromDto(dtoUser);
     LOGGER.info("Entity converted from DTO:" + user);
 
-    var users = List.of(new User("Camile", "Tough", false, "124sad"),
+    var users = List.of(
-        new User("Marti", "Luther", true, "42309fd"), new User("Kate", "Smith", true, "if0243"));
+        new User("Camile", "Tough", false, "124sad"),
+        new User("Marti", "Luther", true, "42309fd"),
+        new User("Kate", "Smith", true, "if0243")
+    );
     LOGGER.info("Domain entities:");
     users.stream().map(User::toString).forEach(LOGGER::info);
 

converter/src/main/java/com/iluwatar/converter/User.java

@@ -73,7 +73,7 @@ public class User {
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
-    User user = (User) o;
+    var user = (User) o;
     return isActive == user.isActive && Objects.equals(firstName, user.firstName) && Objects
         .equals(lastName, user.lastName) && Objects.equals(userId, user.userId);
   }

converter/src/main/java/com/iluwatar/converter/UserConverter.java

@@ -28,13 +28,16 @@ package com.iluwatar.converter;
  */
 public class UserConverter extends Converter<UserDto, User> {
 
-  /**
-   * Constructor.
-   */
   public UserConverter() {
-    super(userDto -> new User(userDto.getFirstName(), userDto.getLastName(), userDto.isActive(),
+    super(UserConverter::convertToEntity, UserConverter::convertToDto);
-            userDto.getEmail()),
-        user -> new UserDto(user.getFirstName(), user.getLastName(), user.isActive(),
-            user.getUserId()));
   }
+
+  private static UserDto convertToDto(User user) {
+    return new UserDto(user.getFirstName(), user.getLastName(), user.isActive(), user.getUserId());
+  }
+
+  private static User convertToEntity(UserDto dto) {
+    return new User(dto.getFirstName(), dto.getLastName(), dto.isActive(), dto.getEmail());
+  }
+
 }

converter/src/main/java/com/iluwatar/converter/UserDto.java

@@ -74,7 +74,7 @@ public class UserDto {
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
-    UserDto userDto = (UserDto) o;
+    var userDto = (UserDto) o;
     return isActive == userDto.isActive && Objects.equals(firstName, userDto.firstName) && Objects
         .equals(lastName, userDto.lastName) && Objects.equals(email, userDto.email);
   }

converter/src/test/java/com/iluwatar/converter/AppTest.java

@@ -32,8 +32,7 @@ public class AppTest {
 
   @Test
   public void testMain() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 
 }

converter/src/test/java/com/iluwatar/converter/ConverterTest.java

@@ -23,12 +23,11 @@
 
 package com.iluwatar.converter;
 
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.List;
 import java.util.Random;
-
+import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.assertEquals;
 
 /**
  * Tests for {@link Converter}
@@ -42,8 +41,8 @@ public class ConverterTest {
    */
   @Test
   public void testConversionsStartingFromDomain() {
-    User u1 = new User("Tom", "Hanks", true, "tom@hanks.com");
+    var u1 = new User("Tom", "Hanks", true, "tom@hanks.com");
-    User u2 = userConverter.convertFromDto(userConverter.convertFromEntity(u1));
+    var u2 = userConverter.convertFromDto(userConverter.convertFromEntity(u1));
     assertEquals(u1, u2);
   }
 
@@ -52,37 +51,47 @@ public class ConverterTest {
    */
   @Test
   public void testConversionsStartingFromDto() {
-    UserDto u1 = new UserDto("Tom", "Hanks", true, "tom@hanks.com");
+    var u1 = new UserDto("Tom", "Hanks", true, "tom@hanks.com");
-    UserDto u2 = userConverter.convertFromEntity(userConverter.convertFromDto(u1));
+    var u2 = userConverter.convertFromEntity(userConverter.convertFromDto(u1));
     assertEquals(u1, u2);
   }
 
   /**
-   * Tests the custom users converter. Thanks to Java8 lambdas, converter can be easily and
+   * Tests the custom users converter. Thanks to Java8 lambdas, converter can be easily and cleanly
-   * cleanly instantiated allowing various different conversion strategies to be implemented.
+   * instantiated allowing various different conversion strategies to be implemented.
    */
   @Test
   public void testCustomConverter() {
-    Converter<UserDto, User> converter = new Converter<>(
+    var converter = new Converter<UserDto, User>(
-        userDto -> new User(userDto.getFirstName(), userDto.getLastName(), userDto.isActive(),
+        userDto -> new User(
-        String.valueOf(new Random().nextInt())),
+            userDto.getFirstName(),
-        user -> new UserDto(user.getFirstName(), user.getLastName(), user.isActive(),
+            userDto.getLastName(),
-        user.getFirstName().toLowerCase() + user.getLastName().toLowerCase() + "@whatever.com"));
+            userDto.isActive(),
-    User u1 = new User("John", "Doe", false, "12324");
+            String.valueOf(new Random().nextInt())
-    UserDto userDto = converter.convertFromEntity(u1);
+        ),
+        user -> new UserDto(
+            user.getFirstName(),
+            user.getLastName(),
+            user.isActive(),
+            user.getFirstName().toLowerCase() + user.getLastName().toLowerCase() + "@whatever.com")
+    );
+    var u1 = new User("John", "Doe", false, "12324");
+    var userDto = converter.convertFromEntity(u1);
     assertEquals("johndoe@whatever.com", userDto.getEmail());
   }
 
   /**
-   * Test whether converting a collection of Users to DTO Users and then converting them back to domain
+   * Test whether converting a collection of Users to DTO Users and then converting them back to
-   * users returns an equal collection.
+   * domain users returns an equal collection.
    */
   @Test
   public void testCollectionConversion() {
-    List<User> users = List.of(new User("Camile", "Tough", false, "124sad"),
+    var users = List.of(
-            new User("Marti", "Luther", true, "42309fd"),
+        new User("Camile", "Tough", false, "124sad"),
-            new User("Kate", "Smith", true, "if0243"));
+        new User("Marti", "Luther", true, "42309fd"),
-    List<User> fromDtos = userConverter.createFromDtos(userConverter.createFromEntities(users));
+        new User("Kate", "Smith", true, "if0243")
+    );
+    var fromDtos = userConverter.createFromDtos(userConverter.createFromEntities(users));
     assertEquals(users, fromDtos);
   }
 }

cqrs/src/main/java/com/iluwatar/cqrs/app/App.java

@@ -24,15 +24,9 @@
 package com.iluwatar.cqrs.app;
 
 import com.iluwatar.cqrs.commandes.CommandServiceImpl;
-import com.iluwatar.cqrs.commandes.ICommandService;
 import com.iluwatar.cqrs.constants.AppConstants;
-import com.iluwatar.cqrs.dto.Author;
-import com.iluwatar.cqrs.dto.Book;
-import com.iluwatar.cqrs.queries.IQueryService;
 import com.iluwatar.cqrs.queries.QueryServiceImpl;
 import com.iluwatar.cqrs.util.HibernateUtil;
-import java.math.BigInteger;
-import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -56,7 +50,7 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    ICommandService commands = new CommandServiceImpl();
+    var commands = new CommandServiceImpl();
 
     // Create Authors and Books using CommandService
     commands.authorCreated(AppConstants.E_EVANS, "Eric Evans", "evans@email.com");
@@ -72,15 +66,15 @@ public class App {
     commands.bookAddedToAuthor("Domain Specific Languages", 48.89, AppConstants.M_FOWLER);
     commands.authorNameUpdated(AppConstants.E_EVANS, "Eric J. Evans");
 
-    IQueryService queries = new QueryServiceImpl();
+    var queries = new QueryServiceImpl();
 
     // Query the database using QueryService
-    Author nullAuthor = queries.getAuthorByUsername("username");
+    var nullAuthor = queries.getAuthorByUsername("username");
-    Author evans = queries.getAuthorByUsername(AppConstants.E_EVANS);
+    var evans = queries.getAuthorByUsername(AppConstants.E_EVANS);
-    BigInteger blochBooksCount = queries.getAuthorBooksCount(AppConstants.J_BLOCH);
+    var blochBooksCount = queries.getAuthorBooksCount(AppConstants.J_BLOCH);
-    BigInteger authorsCount = queries.getAuthorsCount();
+    var authorsCount = queries.getAuthorsCount();
-    Book dddBook = queries.getBook("Domain-Driven Design");
+    var dddBook = queries.getBook("Domain-Driven Design");
-    List<Book> blochBooks = queries.getAuthorBooks(AppConstants.J_BLOCH);
+    var blochBooks = queries.getAuthorBooks(AppConstants.J_BLOCH);
 
     LOGGER.info("Author username : {}", nullAuthor);
     LOGGER.info("Author evans : {}", evans);

cqrs/src/main/java/com/iluwatar/cqrs/commandes/CommandServiceImpl.java

@@ -26,8 +26,6 @@ package com.iluwatar.cqrs.commandes;
 import com.iluwatar.cqrs.domain.model.Author;
 import com.iluwatar.cqrs.domain.model.Book;
 import com.iluwatar.cqrs.util.HibernateUtil;
-import org.hibernate.Query;
-import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 
 /**
@@ -39,9 +37,9 @@ public class CommandServiceImpl implements ICommandService {
   private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
 
   private Author getAuthorByUsername(String username) {
-    Author author = null;
+    Author author;
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
-      Query query = session.createQuery("from Author where username=:username");
+      var query = session.createQuery("from Author where username=:username");
       query.setParameter("username", username);
       author = (Author) query.uniqueResult();
     }
@@ -53,9 +51,9 @@ public class CommandServiceImpl implements ICommandService {
   }
 
   private Book getBookByTitle(String title) {
-    Book book = null;
+    Book book;
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
-      Query query = session.createQuery("from Book where title=:title");
+      var query = session.createQuery("from Book where title=:title");
       query.setParameter("title", title);
       book = (Book) query.uniqueResult();
     }
@@ -68,8 +66,8 @@ public class CommandServiceImpl implements ICommandService {
 
   @Override
   public void authorCreated(String username, String name, String email) {
-    Author author = new Author(username, name, email);
+    var author = new Author(username, name, email);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.save(author);
       session.getTransaction().commit();
@@ -78,9 +76,9 @@ public class CommandServiceImpl implements ICommandService {
 
   @Override
   public void bookAddedToAuthor(String title, double price, String username) {
-    Author author = getAuthorByUsername(username);
+    var author = getAuthorByUsername(username);
-    Book book = new Book(title, price, author);
+    var book = new Book(title, price, author);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.save(book);
       session.getTransaction().commit();
@@ -89,9 +87,9 @@ public class CommandServiceImpl implements ICommandService {
 
   @Override
   public void authorNameUpdated(String username, String name) {
-    Author author = getAuthorByUsername(username);
+    var author = getAuthorByUsername(username);
     author.setName(name);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(author);
       session.getTransaction().commit();
@@ -100,9 +98,9 @@ public class CommandServiceImpl implements ICommandService {
 
   @Override
   public void authorUsernameUpdated(String oldUsername, String newUsername) {
-    Author author = getAuthorByUsername(oldUsername);
+    var author = getAuthorByUsername(oldUsername);
     author.setUsername(newUsername);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(author);
       session.getTransaction().commit();
@@ -111,9 +109,9 @@ public class CommandServiceImpl implements ICommandService {
 
   @Override
   public void authorEmailUpdated(String username, String email) {
-    Author author = getAuthorByUsername(username);
+    var author = getAuthorByUsername(username);
     author.setEmail(email);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(author);
       session.getTransaction().commit();
@@ -122,9 +120,9 @@ public class CommandServiceImpl implements ICommandService {
 
   @Override
   public void bookTitleUpdated(String oldTitle, String newTitle) {
-    Book book = getBookByTitle(oldTitle);
+    var book = getBookByTitle(oldTitle);
     book.setTitle(newTitle);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(book);
       session.getTransaction().commit();
@@ -133,9 +131,9 @@ public class CommandServiceImpl implements ICommandService {
 
   @Override
   public void bookPriceUpdated(String title, double price) {
-    Book book = getBookByTitle(title);
+    var book = getBookByTitle(title);
     book.setPrice(price);
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
       session.beginTransaction();
       session.update(book);
       session.getTransaction().commit();

cqrs/src/main/java/com/iluwatar/cqrs/dto/Author.java

@@ -80,7 +80,7 @@ public class Author {
     if (!(obj instanceof Author)) {
       return false;
     }
-    Author other = (Author) obj;
+    var other = (Author) obj;
     return username.equals(other.getUsername()) && email.equals(other.getEmail()) && name
         .equals(other.getName());
 

cqrs/src/main/java/com/iluwatar/cqrs/dto/Book.java

@@ -73,7 +73,7 @@ public class Book {
     if (!(obj instanceof Book)) {
       return false;
     }
-    Book book = (Book) obj;
+    var book = (Book) obj;
     return title.equals(book.getTitle()) && price == book.getPrice();
   }
 

cqrs/src/main/java/com/iluwatar/cqrs/queries/QueryServiceImpl.java

@@ -29,8 +29,6 @@ import com.iluwatar.cqrs.dto.Book;
 import com.iluwatar.cqrs.util.HibernateUtil;
 import java.math.BigInteger;
 import java.util.List;
-import org.hibernate.SQLQuery;
-import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.transform.Transformers;
 
@@ -44,9 +42,9 @@ public class QueryServiceImpl implements IQueryService {
 
   @Override
   public Author getAuthorByUsername(String username) {
-    Author authorDTo = null;
+    Author authorDTo;
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
-      SQLQuery sqlQuery = session.createSQLQuery("SELECT a.username as \"username\","
+      var sqlQuery = session.createSQLQuery("SELECT a.username as \"username\","
           + " a.name as \"name\", a.email as \"email\""
           + "FROM Author a where a.username=:username");
       sqlQuery.setParameter(AppConstants.USER_NAME, username);
@@ -58,9 +56,9 @@ public class QueryServiceImpl implements IQueryService {
 
   @Override
   public Book getBook(String title) {
-    Book bookDTo = null;
+    Book bookDTo;
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
-      SQLQuery sqlQuery = session.createSQLQuery("SELECT b.title as \"title\","
+      var sqlQuery = session.createSQLQuery("SELECT b.title as \"title\","
           + " b.price as \"price\"" + " FROM Book b where b.title=:title");
       sqlQuery.setParameter("title", title);
       bookDTo =
@@ -71,9 +69,9 @@ public class QueryServiceImpl implements IQueryService {
 
   @Override
   public List<Book> getAuthorBooks(String username) {
-    List<Book> bookDTos = null;
+    List<Book> bookDTos;
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
-      SQLQuery sqlQuery = session.createSQLQuery("SELECT b.title as \"title\", b.price as \"price\""
+      var sqlQuery = session.createSQLQuery("SELECT b.title as \"title\", b.price as \"price\""
           + " FROM Author a , Book b where b.author_id = a.id and a.username=:username");
       sqlQuery.setParameter(AppConstants.USER_NAME, username);
       bookDTos = sqlQuery.setResultTransformer(Transformers.aliasToBean(Book.class)).list();
@@ -83,9 +81,9 @@ public class QueryServiceImpl implements IQueryService {
 
   @Override
   public BigInteger getAuthorBooksCount(String username) {
-    BigInteger bookcount = null;
+    BigInteger bookcount;
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
-      SQLQuery sqlQuery = session.createSQLQuery(
+      var sqlQuery = session.createSQLQuery(
           "SELECT count(b.title)" + " FROM  Book b, Author a"
               + " where b.author_id = a.id and a.username=:username");
       sqlQuery.setParameter(AppConstants.USER_NAME, username);
@@ -96,9 +94,9 @@ public class QueryServiceImpl implements IQueryService {
 
   @Override
   public BigInteger getAuthorsCount() {
-    BigInteger authorcount = null;
+    BigInteger authorcount;
-    try (Session session = sessionFactory.openSession()) {
+    try (var session = sessionFactory.openSession()) {
-      SQLQuery sqlQuery = session.createSQLQuery("SELECT count(id) from Author");
+      var sqlQuery = session.createSQLQuery("SELECT count(id) from Author");
       authorcount = (BigInteger) sqlQuery.uniqueResult();
     }
     return authorcount;

cqrs/src/main/java/com/iluwatar/cqrs/util/HibernateUtil.java

@@ -25,7 +25,6 @@ package com.iluwatar.cqrs.util;
 
 import org.hibernate.SessionFactory;
 import org.hibernate.boot.MetadataSources;
-import org.hibernate.boot.registry.StandardServiceRegistry;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -42,8 +41,7 @@ public class HibernateUtil {
   private static SessionFactory buildSessionFactory() {
 
     // configures settings from hibernate.cfg.xml
-    final StandardServiceRegistry registry =
+    final var registry = new StandardServiceRegistryBuilder().configure().build();
-        new StandardServiceRegistryBuilder().configure().build();
     try {
       return new MetadataSources(registry).buildMetadata().buildSessionFactory();
     } catch (Exception ex) {

cqrs/src/test/java/com/iluwatar/cqrs/IntegrationTest.java

@@ -23,33 +23,28 @@
 
 package com.iluwatar.cqrs;
 
-import java.math.BigInteger;
+import static org.junit.jupiter.api.Assertions.assertEquals;
-import java.util.List;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import com.iluwatar.cqrs.commandes.CommandServiceImpl;
-import com.iluwatar.cqrs.commandes.ICommandService;
 import com.iluwatar.cqrs.dto.Author;
 import com.iluwatar.cqrs.dto.Book;
 import com.iluwatar.cqrs.queries.IQueryService;
 import com.iluwatar.cqrs.queries.QueryServiceImpl;
+import java.math.BigInteger;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 /**
  * Integration test of IQueryService and ICommandService with h2 data
- *
  */
 public class IntegrationTest {
 
   private static IQueryService queryService;
-  private static ICommandService commandService;
 
   @BeforeAll
   public static void initializeAndPopulateDatabase() {
-    commandService = new CommandServiceImpl();
+    var commandService = new CommandServiceImpl();
     queryService = new QueryServiceImpl();
 
     // create first author1
@@ -73,7 +68,7 @@ public class IntegrationTest {
 
   @Test
   public void testGetAuthorByUsername() {
-    Author author = queryService.getAuthorByUsername("username1");
+    var author = queryService.getAuthorByUsername("username1");
     assertEquals("username1", author.getUsername());
     assertEquals("name1", author.getName());
     assertEquals("email1", author.getEmail());
@@ -81,22 +76,22 @@ public class IntegrationTest {
 
   @Test
   public void testGetUpdatedAuthorByUsername() {
-    Author author = queryService.getAuthorByUsername("new_username2");
+    var author = queryService.getAuthorByUsername("new_username2");
-    Author expectedAuthor = new Author("new_name2", "new_email2", "new_username2");
+    var expectedAuthor = new Author("new_name2", "new_email2", "new_username2");
     assertEquals(expectedAuthor, author);
 
   }
 
   @Test
   public void testGetBook() {
-    Book book = queryService.getBook("title1");
+    var book = queryService.getBook("title1");
     assertEquals("title1", book.getTitle());
     assertEquals(10, book.getPrice(), 0.01);
   }
 
   @Test
   public void testGetAuthorBooks() {
-    List<Book> books = queryService.getAuthorBooks("username1");
+    var books = queryService.getAuthorBooks("username1");
     assertEquals(2, books.size());
     assertTrue(books.contains(new Book("title1", 10)));
     assertTrue(books.contains(new Book("new_title2", 30)));
@@ -104,13 +99,13 @@ public class IntegrationTest {
 
   @Test
   public void testGetAuthorBooksCount() {
-    BigInteger bookCount = queryService.getAuthorBooksCount("username1");
+    var bookCount = queryService.getAuthorBooksCount("username1");
     assertEquals(new BigInteger("2"), bookCount);
   }
 
   @Test
   public void testGetAuthorsCount() {
-    BigInteger authorCount = queryService.getAuthorsCount();
+    var authorCount = queryService.getAuthorsCount();
     assertEquals(new BigInteger("2"), authorCount);
   }
 

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

@@ -23,11 +23,8 @@
 
 package com.iluwatar.dao;
 
-import java.sql.Connection;
 import java.sql.SQLException;
-import java.sql.Statement;
 import java.util.List;
-import java.util.stream.Stream;
 import javax.sql.DataSource;
 import org.h2.jdbcx.JdbcDataSource;
 import org.slf4j.Logger;
@@ -57,32 +54,32 @@ public class App {
    * @throws Exception if any error occurs.
    */
   public static void main(final String[] args) throws Exception {
-    final CustomerDao inMemoryDao = new InMemoryCustomerDao();
+    final var inMemoryDao = new InMemoryCustomerDao();
     performOperationsUsing(inMemoryDao);
 
-    final DataSource dataSource = createDataSource();
+    final var dataSource = createDataSource();
     createSchema(dataSource);
-    final CustomerDao dbDao = new DbCustomerDao(dataSource);
+    final var dbDao = new DbCustomerDao(dataSource);
     performOperationsUsing(dbDao);
     deleteSchema(dataSource);
   }
 
   private static void deleteSchema(DataSource dataSource) throws SQLException {
-    try (Connection connection = dataSource.getConnection();
+    try (var connection = dataSource.getConnection();
-         Statement statement = connection.createStatement()) {
+         var statement = connection.createStatement()) {
       statement.execute(CustomerSchemaSql.DELETE_SCHEMA_SQL);
     }
   }
 
   private static void createSchema(DataSource dataSource) throws SQLException {
-    try (Connection connection = dataSource.getConnection();
+    try (var connection = dataSource.getConnection();
-         Statement statement = connection.createStatement()) {
+         var statement = connection.createStatement()) {
       statement.execute(CustomerSchemaSql.CREATE_SCHEMA_SQL);
     }
   }
 
   private static DataSource createDataSource() {
-    JdbcDataSource dataSource = new JdbcDataSource();
+    var dataSource = new JdbcDataSource();
     dataSource.setURL(DB_URL);
     return dataSource;
   }
@@ -90,18 +87,18 @@ public class App {
   private static void performOperationsUsing(final CustomerDao customerDao) throws Exception {
     addCustomers(customerDao);
     log.info(ALL_CUSTOMERS);
-    try (Stream<Customer> customerStream = customerDao.getAll()) {
+    try (var customerStream = customerDao.getAll()) {
       customerStream.forEach((customer) -> log.info(customer.toString()));
     }
     log.info("customerDao.getCustomerById(2): " + customerDao.getById(2));
-    final Customer customer = new Customer(4, "Dan", "Danson");
+    final var customer = new Customer(4, "Dan", "Danson");
     customerDao.add(customer);
     log.info(ALL_CUSTOMERS + customerDao.getAll());
     customer.setFirstName("Daniel");
     customer.setLastName("Danielson");
     customerDao.update(customer);
     log.info(ALL_CUSTOMERS);
-    try (Stream<Customer> customerStream = customerDao.getAll()) {
+    try (var customerStream = customerDao.getAll()) {
       customerStream.forEach((cust) -> log.info(cust.toString()));
     }
     customerDao.delete(customer);
@@ -109,7 +106,7 @@ public class App {
   }
 
   private static void addCustomers(CustomerDao customerDao) throws Exception {
-    for (Customer customer : generateSampleCustomers()) {
+    for (var customer : generateSampleCustomers()) {
       customerDao.add(customer);
     }
   }
@@ -120,9 +117,9 @@ public class App {
    * @return list of customers.
    */
   public static List<Customer> generateSampleCustomers() {
-    final Customer customer1 = new Customer(1, "Adam", "Adamson");
+    final var customer1 = new Customer(1, "Adam", "Adamson");
-    final Customer customer2 = new Customer(2, "Bob", "Bobson");
+    final var customer2 = new Customer(2, "Bob", "Bobson");
-    final Customer customer3 = new Customer(3, "Carl", "Carlson");
+    final var customer3 = new Customer(3, "Carl", "Carlson");
     return List.of(customer1, customer2, customer3);
   }
 }

dao/src/main/java/com/iluwatar/dao/Customer.java

@@ -73,11 +73,11 @@ public class Customer {
 
   @Override
   public boolean equals(final Object that) {
-    boolean isEqual = false;
+    var isEqual = false;
     if (this == that) {
       isEqual = true;
     } else if (that != null && getClass() == that.getClass()) {
-      final Customer customer = (Customer) that;
+      final var customer = (Customer) that;
       if (getId() == customer.getId()) {
         isEqual = true;
       }

dao/src/main/java/com/iluwatar/dao/DbCustomerDao.java

@@ -65,13 +65,10 @@ public class DbCustomerDao implements CustomerDao {
    */
   @Override
   public Stream<Customer> getAll() throws Exception {
-
-    Connection connection;
     try {
-      connection = getConnection();
+      var connection = getConnection();
-      PreparedStatement statement =
+      var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS");
-          connection.prepareStatement("SELECT * FROM CUSTOMERS"); // NOSONAR
+      var resultSet = statement.executeQuery(); // NOSONAR
-      ResultSet resultSet = statement.executeQuery(); // NOSONAR
       return StreamSupport.stream(new Spliterators.AbstractSpliterator<Customer>(Long.MAX_VALUE,
           Spliterator.ORDERED) {
 
@@ -121,9 +118,8 @@ public class DbCustomerDao implements CustomerDao {
 
     ResultSet resultSet = null;
 
-    try (Connection connection = getConnection();
+    try (var connection = getConnection();
-         PreparedStatement statement =
+         var statement = connection.prepareStatement("SELECT * FROM CUSTOMERS WHERE ID = ?")) {
-             connection.prepareStatement("SELECT * FROM CUSTOMERS WHERE ID = ?")) {
 
       statement.setInt(1, id);
       resultSet = statement.executeQuery();
@@ -150,9 +146,8 @@ public class DbCustomerDao implements CustomerDao {
       return false;
     }
 
-    try (Connection connection = getConnection();
+    try (var connection = getConnection();
-         PreparedStatement statement =
+         var statement = connection.prepareStatement("INSERT INTO CUSTOMERS VALUES (?,?,?)")) {
-             connection.prepareStatement("INSERT INTO CUSTOMERS VALUES (?,?,?)")) {
       statement.setInt(1, customer.getId());
       statement.setString(2, customer.getFirstName());
       statement.setString(3, customer.getLastName());
@@ -168,8 +163,8 @@ public class DbCustomerDao implements CustomerDao {
    */
   @Override
   public boolean update(Customer customer) throws Exception {
-    try (Connection connection = getConnection();
+    try (var connection = getConnection();
-         PreparedStatement statement =
+         var statement =
              connection
                  .prepareStatement("UPDATE CUSTOMERS SET FNAME = ?, LNAME = ? WHERE ID = ?")) {
       statement.setString(1, customer.getFirstName());
@@ -186,9 +181,8 @@ public class DbCustomerDao implements CustomerDao {
    */
   @Override
   public boolean delete(Customer customer) throws Exception {
-    try (Connection connection = getConnection();
+    try (var connection = getConnection();
-         PreparedStatement statement =
+         var statement = connection.prepareStatement("DELETE FROM CUSTOMERS WHERE ID = ?")) {
-             connection.prepareStatement("DELETE FROM CUSTOMERS WHERE ID = ?")) {
       statement.setInt(1, customer.getId());
       return statement.executeUpdate() > 0;
     } catch (SQLException ex) {

dao/src/test/java/com/iluwatar/dao/AppTest.java

@@ -31,7 +31,6 @@ import org.junit.jupiter.api.Test;
 public class AppTest {
   @Test
   public void test() throws Exception {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

dao/src/test/java/com/iluwatar/dao/CustomerTest.java

@@ -46,36 +46,36 @@ public class CustomerTest {
 
   @Test
   public void getAndSetId() {
-    final int newId = 2;
+    final var newId = 2;
     customer.setId(newId);
     assertEquals(newId, customer.getId());
   }
 
   @Test
   public void getAndSetFirstname() {
-    final String newFirstname = "Bill";
+    final var newFirstname = "Bill";
     customer.setFirstName(newFirstname);
     assertEquals(newFirstname, customer.getFirstName());
   }
 
   @Test
   public void getAndSetLastname() {
-    final String newLastname = "Clinton";
+    final var newLastname = "Clinton";
     customer.setLastName(newLastname);
     assertEquals(newLastname, customer.getLastName());
   }
 
   @Test
   public void notEqualWithDifferentId() {
-    final int newId = 2;
+    final var newId = 2;
-    final Customer otherCustomer = new Customer(newId, FIRSTNAME, LASTNAME);
+    final var otherCustomer = new Customer(newId, FIRSTNAME, LASTNAME);
     assertNotEquals(customer, otherCustomer);
     assertNotEquals(customer.hashCode(), otherCustomer.hashCode());
   }
 
   @Test
   public void equalsWithSameObjectValues() {
-    final Customer otherCustomer = new Customer(ID, FIRSTNAME, LASTNAME);
+    final var otherCustomer = new Customer(ID, FIRSTNAME, LASTNAME);
     assertEquals(customer, otherCustomer);
     assertEquals(customer.hashCode(), otherCustomer.hashCode());
   }

dao/src/test/java/com/iluwatar/dao/DbCustomerDaoTest.java

@@ -23,20 +23,6 @@
 
 package com.iluwatar.dao;
 
-import org.h2.jdbcx.JdbcDataSource;
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Nested;
-import org.junit.jupiter.api.Test;
-import org.mockito.Mockito;
-
-import javax.sql.DataSource;
-import java.sql.Connection;
-import java.sql.DriverManager;
-import java.sql.SQLException;
-import java.sql.Statement;
-import java.util.stream.Stream;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -46,6 +32,17 @@ import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
 
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import javax.sql.DataSource;
+import org.h2.jdbcx.JdbcDataSource;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
 /**
  * Tests {@link DbCustomerDao}.
  */
@@ -57,12 +54,13 @@ public class DbCustomerDaoTest {
 
   /**
    * Creates customers schema.
+   *
    * @throws SQLException if there is any error while creating schema.
    */
   @BeforeEach
   public void createSchema() throws SQLException {
-    try (Connection connection = DriverManager.getConnection(DB_URL);
+    try (var connection = DriverManager.getConnection(DB_URL);
-        Statement statement = connection.createStatement()) {
+         var statement = connection.createStatement()) {
       statement.execute(CustomerSchemaSql.CREATE_SCHEMA_SQL);
     }
   }
@@ -75,14 +73,15 @@ public class DbCustomerDaoTest {
 
     /**
      * Setup for connection success scenario.
+     *
      * @throws Exception if any error occurs.
      */
     @BeforeEach
     public void setUp() throws Exception {
-      JdbcDataSource dataSource = new JdbcDataSource();
+      var dataSource = new JdbcDataSource();
       dataSource.setURL(DB_URL);
       dao = new DbCustomerDao(dataSource);
-      boolean result = dao.add(existingCustomer);
+      var result = dao.add(existingCustomer);
       assertTrue(result);
     }
 
@@ -94,12 +93,12 @@ public class DbCustomerDaoTest {
 
       @Test
       public void addingShouldResultInSuccess() throws Exception {
-        try (Stream<Customer> allCustomers = dao.getAll()) {
+        try (var allCustomers = dao.getAll()) {
           assumeTrue(allCustomers.count() == 1);
         }
 
-        final Customer nonExistingCustomer = new Customer(2, "Robert", "Englund");
+        final var nonExistingCustomer = new Customer(2, "Robert", "Englund");
-        boolean result = dao.add(nonExistingCustomer);
+        var result = dao.add(nonExistingCustomer);
         assertTrue(result);
 
         assertCustomerCountIs(2);
@@ -108,8 +107,8 @@ public class DbCustomerDaoTest {
 
       @Test
       public void deletionShouldBeFailureAndNotAffectExistingCustomers() throws Exception {
-        final Customer nonExistingCustomer = new Customer(2, "Robert", "Englund");
+        final var nonExistingCustomer = new Customer(2, "Robert", "Englund");
-        boolean result = dao.delete(nonExistingCustomer);
+        var result = dao.delete(nonExistingCustomer);
 
         assertFalse(result);
         assertCustomerCountIs(1);
@@ -117,11 +116,11 @@ public class DbCustomerDaoTest {
 
       @Test
       public void updationShouldBeFailureAndNotAffectExistingCustomers() throws Exception {
-        final int nonExistingId = getNonExistingCustomerId();
+        final var nonExistingId = getNonExistingCustomerId();
-        final String newFirstname = "Douglas";
+        final var newFirstname = "Douglas";
-        final String newLastname = "MacArthur";
+        final var newLastname = "MacArthur";
-        final Customer customer = new Customer(nonExistingId, newFirstname, newLastname);
+        final var customer = new Customer(nonExistingId, newFirstname, newLastname);
-        boolean result = dao.update(customer);
+        var result = dao.update(customer);
 
         assertFalse(result);
         assertFalse(dao.getById(nonExistingId).isPresent());
@@ -136,16 +135,14 @@ public class DbCustomerDaoTest {
     /**
      * Represents a scenario where DAO operations are being performed on an already existing
      * customer.
-     *
      */
     @Nested
     public class ExistingCustomer {
 
       @Test
       public void addingShouldResultInFailureAndNotAffectExistingCustomers() throws Exception {
-        Customer existingCustomer = new Customer(1, "Freddy", "Krueger");
+        var existingCustomer = new Customer(1, "Freddy", "Krueger");
-
+        var result = dao.add(existingCustomer);
-        boolean result = dao.add(existingCustomer);
 
         assertFalse(result);
         assertCustomerCountIs(1);
@@ -154,7 +151,7 @@ public class DbCustomerDaoTest {
 
       @Test
       public void deletionShouldBeSuccessAndCustomerShouldBeNonAccessible() throws Exception {
-        boolean result = dao.delete(existingCustomer);
+        var result = dao.delete(existingCustomer);
 
         assertTrue(result);
         assertCustomerCountIs(0);
@@ -162,15 +159,16 @@ public class DbCustomerDaoTest {
       }
 
       @Test
-      public void updationShouldBeSuccessAndAccessingTheSameCustomerShouldReturnUpdatedInformation() throws Exception {
+      public void updationShouldBeSuccessAndAccessingTheSameCustomerShouldReturnUpdatedInformation() throws
-        final String newFirstname = "Bernard";
+          Exception {
-        final String newLastname = "Montgomery";
+        final var newFirstname = "Bernard";
-        final Customer customer = new Customer(existingCustomer.getId(), newFirstname, newLastname);
+        final var newLastname = "Montgomery";
-        boolean result = dao.update(customer);
+        final var customer = new Customer(existingCustomer.getId(), newFirstname, newLastname);
+        var result = dao.update(customer);
 
         assertTrue(result);
 
-        final Customer cust = dao.getById(existingCustomer.getId()).get();
+        final var cust = dao.getById(existingCustomer.getId()).get();
         assertEquals(newFirstname, cust.getFirstName());
         assertEquals(newLastname, cust.getLastName());
       }
@@ -178,28 +176,28 @@ public class DbCustomerDaoTest {
   }
 
   /**
-   * Represents a scenario where DB connectivity is not present due to network issue, or
+   * Represents a scenario where DB connectivity is not present due to network issue, or DB service
-   * DB service unavailable.
+   * unavailable.
-   * 
    */
   @Nested
   public class ConnectivityIssue {
-    
+
     private static final String EXCEPTION_CAUSE = "Connection not available";
 
     /**
      * setup a connection failure scenario.
+     *
      * @throws SQLException if any error occurs.
      */
     @BeforeEach
     public void setUp() throws SQLException {
       dao = new DbCustomerDao(mockedDatasource());
     }
-    
+
     private DataSource mockedDatasource() throws SQLException {
-      DataSource mockedDataSource = mock(DataSource.class);
+      var mockedDataSource = mock(DataSource.class);
-      Connection mockedConnection = mock(Connection.class);
+      var mockedConnection = mock(Connection.class);
-      SQLException exception = new SQLException(EXCEPTION_CAUSE);
+      var exception = new SQLException(EXCEPTION_CAUSE);
       doThrow(exception).when(mockedConnection).prepareStatement(Mockito.anyString());
       doReturn(mockedConnection).when(mockedDataSource).getConnection();
       return mockedDataSource;
@@ -211,30 +209,30 @@ public class DbCustomerDaoTest {
         dao.add(new Customer(2, "Bernard", "Montgomery"));
       });
     }
-    
+
     @Test
     public void deletingACustomerFailsWithExceptionAsFeedbackToTheClient() {
       assertThrows(Exception.class, () -> {
         dao.delete(existingCustomer);
       });
     }
-    
+
     @Test
     public void updatingACustomerFailsWithFeedbackToTheClient() {
-      final String newFirstname = "Bernard";
+      final var newFirstname = "Bernard";
-      final String newLastname = "Montgomery";
+      final var newLastname = "Montgomery";
       assertThrows(Exception.class, () -> {
         dao.update(new Customer(existingCustomer.getId(), newFirstname, newLastname));
       });
     }
-    
+
     @Test
     public void retrievingACustomerByIdFailsWithExceptionAsFeedbackToClient() {
       assertThrows(Exception.class, () -> {
         dao.getById(existingCustomer.getId());
       });
     }
-    
+
     @Test
     public void retrievingAllCustomersFailsWithExceptionAsFeedbackToClient() {
       assertThrows(Exception.class, () -> {
@@ -246,18 +244,19 @@ public class DbCustomerDaoTest {
 
   /**
    * Delete customer schema for fresh setup per test.
+   *
    * @throws SQLException if any error occurs.
    */
   @AfterEach
   public void deleteSchema() throws SQLException {
-    try (Connection connection = DriverManager.getConnection(DB_URL);
+    try (var connection = DriverManager.getConnection(DB_URL);
-        Statement statement = connection.createStatement()) {
+         var statement = connection.createStatement()) {
       statement.execute(CustomerSchemaSql.DELETE_SCHEMA_SQL);
     }
   }
 
   private void assertCustomerCountIs(int count) throws Exception {
-    try (Stream<Customer> allCustomers = dao.getAll()) {
+    try (var allCustomers = dao.getAll()) {
       assertEquals(count, allCustomers.count());
     }
   }
@@ -265,7 +264,7 @@ public class DbCustomerDaoTest {
 
   /**
    * An arbitrary number which does not correspond to an active Customer id.
-   * 
+   *
    * @return an int of a customer id which doesn't exist
    */
   private int getNonExistingCustomerId() {

dao/src/test/java/com/iluwatar/dao/InMemoryCustomerDaoTest.java

@@ -23,18 +23,15 @@
 
 package com.iluwatar.dao;
 
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Nested;
-import org.junit.jupiter.api.Test;
-
-import java.util.Optional;
-import java.util.stream.Stream;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
 /**
  * Tests {@link InMemoryCustomerDao}.
  */
@@ -50,20 +47,20 @@ public class InMemoryCustomerDaoTest {
   }
 
   /**
-   * Represents the scenario when the DAO operations are being performed on a non existent 
+   * Represents the scenario when the DAO operations are being performed on a non existent
-   * customer.  
+   * customer.
    */
   @Nested
   public class NonExistingCustomer {
 
     @Test
     public void addingShouldResultInSuccess() throws Exception {
-      try (Stream<Customer> allCustomers = dao.getAll()) {
+      try (var allCustomers = dao.getAll()) {
         assumeTrue(allCustomers.count() == 1);
       }
 
-      final Customer nonExistingCustomer = new Customer(2, "Robert", "Englund");
+      final var nonExistingCustomer = new Customer(2, "Robert", "Englund");
-      boolean result = dao.add(nonExistingCustomer);
+      var result = dao.add(nonExistingCustomer);
       assertTrue(result);
 
       assertCustomerCountIs(2);
@@ -72,8 +69,8 @@ public class InMemoryCustomerDaoTest {
 
     @Test
     public void deletionShouldBeFailureAndNotAffectExistingCustomers() throws Exception {
-      final Customer nonExistingCustomer = new Customer(2, "Robert", "Englund");
+      final var nonExistingCustomer = new Customer(2, "Robert", "Englund");
-      boolean result = dao.delete(nonExistingCustomer);
+      var result = dao.delete(nonExistingCustomer);
 
       assertFalse(result);
       assertCustomerCountIs(1);
@@ -81,11 +78,11 @@ public class InMemoryCustomerDaoTest {
 
     @Test
     public void updationShouldBeFailureAndNotAffectExistingCustomers() throws Exception {
-      final int nonExistingId = getNonExistingCustomerId();
+      final var nonExistingId = getNonExistingCustomerId();
-      final String newFirstname = "Douglas";
+      final var newFirstname = "Douglas";
-      final String newLastname = "MacArthur";
+      final var newLastname = "MacArthur";
-      final Customer customer = new Customer(nonExistingId, newFirstname, newLastname);
+      final var customer = new Customer(nonExistingId, newFirstname, newLastname);
-      boolean result = dao.update(customer);
+      var result = dao.update(customer);
 
       assertFalse(result);
       assertFalse(dao.getById(nonExistingId).isPresent());
@@ -106,7 +103,7 @@ public class InMemoryCustomerDaoTest {
 
     @Test
     public void addingShouldResultInFailureAndNotAffectExistingCustomers() throws Exception {
-      boolean result = dao.add(CUSTOMER);
+      var result = dao.add(CUSTOMER);
 
       assertFalse(result);
       assertCustomerCountIs(1);
@@ -115,7 +112,7 @@ public class InMemoryCustomerDaoTest {
 
     @Test
     public void deletionShouldBeSuccessAndCustomerShouldBeNonAccessible() throws Exception {
-      boolean result = dao.delete(CUSTOMER);
+      var result = dao.delete(CUSTOMER);
 
       assertTrue(result);
       assertCustomerCountIs(0);
@@ -123,23 +120,24 @@ public class InMemoryCustomerDaoTest {
     }
 
     @Test
-    public void updationShouldBeSuccessAndAccessingTheSameCustomerShouldReturnUpdatedInformation() throws Exception {
+    public void updationShouldBeSuccessAndAccessingTheSameCustomerShouldReturnUpdatedInformation() throws
-      final String newFirstname = "Bernard";
+        Exception {
-      final String newLastname = "Montgomery";
+      final var newFirstname = "Bernard";
-      final Customer customer = new Customer(CUSTOMER.getId(), newFirstname, newLastname);
+      final var newLastname = "Montgomery";
-      boolean result = dao.update(customer);
+      final var customer = new Customer(CUSTOMER.getId(), newFirstname, newLastname);
+      var result = dao.update(customer);
 
       assertTrue(result);
 
-      final Customer cust = dao.getById(CUSTOMER.getId()).get();
+      final var cust = dao.getById(CUSTOMER.getId()).get();
       assertEquals(newFirstname, cust.getFirstName());
       assertEquals(newLastname, cust.getLastName());
     }
-    
+
     @Test
     public void retriveShouldReturnTheCustomer() {
-      Optional<Customer> optionalCustomer = dao.getById(CUSTOMER.getId());
+      var optionalCustomer = dao.getById(CUSTOMER.getId());
-      
+
       assertTrue(optionalCustomer.isPresent());
       assertEquals(CUSTOMER, optionalCustomer.get());
     }
@@ -147,15 +145,15 @@ public class InMemoryCustomerDaoTest {
 
   /**
    * An arbitrary number which does not correspond to an active Customer id.
-   * 
+   *
    * @return an int of a customer id which doesn't exist
    */
   private int getNonExistingCustomerId() {
     return 999;
   }
-  
+
   private void assertCustomerCountIs(int count) throws Exception {
-    try (Stream<Customer> allCustomers = dao.getAll()) {
+    try (var allCustomers = dao.getAll()) {
       assertEquals(count, allCustomers.count());
     }
   }

data-bus/src/main/java/com/iluwatar/databus/App.java

@@ -59,11 +59,11 @@ import java.time.LocalDateTime;
 class App {
 
   public static void main(String[] args) {
-    final DataBus bus = DataBus.getInstance();
+    final var bus = DataBus.getInstance();
     bus.subscribe(new StatusMember(1));
     bus.subscribe(new StatusMember(2));
-    final MessageCollectorMember foo = new MessageCollectorMember("Foo");
+    final var foo = new MessageCollectorMember("Foo");
-    final MessageCollectorMember bar = new MessageCollectorMember("Bar");
+    final var bar = new MessageCollectorMember("Bar");
     bus.subscribe(foo);
     bus.publish(StartingData.of(LocalDateTime.now()));
     bus.publish(MessageData.of("Only Foo should see this"));

data-bus/src/main/java/com/iluwatar/databus/members/MessageCollectorMember.java

@@ -27,7 +27,6 @@ import com.iluwatar.databus.DataType;
 import com.iluwatar.databus.Member;
 import com.iluwatar.databus.data.MessageData;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.logging.Logger;
 
@@ -61,6 +60,6 @@ public class MessageCollectorMember implements Member {
   }
 
   public List<String> getMessages() {
-    return Collections.unmodifiableList(messages);
+    return List.copyOf(messages);
   }
 }

data-bus/src/test/java/com/iluwatar/databus/DataBusTest.java

@@ -23,14 +23,14 @@
 
 package com.iluwatar.databus;
 
+import static org.mockito.BDDMockito.then;
+import static org.mockito.Mockito.never;
+
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
-import static org.mockito.BDDMockito.then;
-import static org.mockito.Mockito.never;
-
 /**
  * Tests for {@link DataBus}.
  *
@@ -52,7 +52,7 @@ public class DataBusTest {
   @Test
   public void publishedEventIsReceivedBySubscribedMember() {
     //given
-    final DataBus dataBus = DataBus.getInstance();
+    final var dataBus = DataBus.getInstance();
     dataBus.subscribe(member);
     //when
     dataBus.publish(event);
@@ -63,7 +63,7 @@ public class DataBusTest {
   @Test
   public void publishedEventIsNotReceivedByMemberAfterUnsubscribing() {
     //given
-    final DataBus dataBus = DataBus.getInstance();
+    final var dataBus = DataBus.getInstance();
     dataBus.subscribe(member);
     dataBus.unsubscribe(member);
     //when

data-bus/src/test/java/com/iluwatar/databus/members/MessageCollectorMemberTest.java

@@ -23,15 +23,14 @@
 
 package com.iluwatar.databus.members;
 
-import com.iluwatar.databus.data.MessageData;
-import com.iluwatar.databus.data.StartingData;
-import org.junit.jupiter.api.Test;
-
-import java.time.LocalDateTime;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import com.iluwatar.databus.data.MessageData;
+import com.iluwatar.databus.data.StartingData;
+import java.time.LocalDateTime;
+import org.junit.jupiter.api.Test;
+
 /**
  * Tests for {@link MessageCollectorMember}.
  *
@@ -42,9 +41,9 @@ public class MessageCollectorMemberTest {
   @Test
   public void collectMessageFromMessageData() {
     //given
-    final String message = "message";
+    final var message = "message";
-    final MessageData messageData = new MessageData(message);
+    final var messageData = new MessageData(message);
-    final MessageCollectorMember collector = new MessageCollectorMember("collector");
+    final var collector = new MessageCollectorMember("collector");
     //when
     collector.accept(messageData);
     //then
@@ -54,8 +53,8 @@ public class MessageCollectorMemberTest {
   @Test
   public void collectIgnoresMessageFromOtherDataTypes() {
     //given
-    final StartingData startingData = new StartingData(LocalDateTime.now());
+    final var startingData = new StartingData(LocalDateTime.now());
-    final MessageCollectorMember collector = new MessageCollectorMember("collector");
+    final var collector = new MessageCollectorMember("collector");
     //when
     collector.accept(startingData);
     //then

data-bus/src/test/java/com/iluwatar/databus/members/StatusMemberTest.java

@@ -23,17 +23,16 @@
 
 package com.iluwatar.databus.members;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
 import com.iluwatar.databus.DataBus;
 import com.iluwatar.databus.data.MessageData;
 import com.iluwatar.databus.data.StartingData;
 import com.iluwatar.databus.data.StoppingData;
-import org.junit.jupiter.api.Test;
-
 import java.time.LocalDateTime;
 import java.time.Month;
-
+import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNull;
 
 /**
  * Tests for {@link StatusMember}.
@@ -45,9 +44,9 @@ public class StatusMemberTest {
   @Test
   public void statusRecordsTheStartTime() {
     //given
-    final LocalDateTime startTime = LocalDateTime.of(2017, Month.APRIL, 1, 19, 9);
+    final var startTime = LocalDateTime.of(2017, Month.APRIL, 1, 19, 9);
-    final StartingData startingData = new StartingData(startTime);
+    final var startingData = new StartingData(startTime);
-    final StatusMember statusMember = new StatusMember(1);
+    final var statusMember = new StatusMember(1);
     //when
     statusMember.accept(startingData);
     //then
@@ -57,10 +56,10 @@ public class StatusMemberTest {
   @Test
   public void statusRecordsTheStopTime() {
     //given
-    final LocalDateTime stop = LocalDateTime.of(2017, Month.APRIL, 1, 19, 12);
+    final var stop = LocalDateTime.of(2017, Month.APRIL, 1, 19, 12);
-    final StoppingData stoppingData = new StoppingData(stop);
+    final var stoppingData = new StoppingData(stop);
     stoppingData.setDataBus(DataBus.getInstance());
-    final StatusMember statusMember = new StatusMember(1);
+    final var statusMember = new StatusMember(1);
     //when
     statusMember.accept(stoppingData);
     //then
@@ -70,8 +69,8 @@ public class StatusMemberTest {
   @Test
   public void statusIgnoresMessageData() {
     //given
-    final MessageData messageData = new MessageData("message");
+    final var messageData = new MessageData("message");
-    final StatusMember statusMember = new StatusMember(1);
+    final var statusMember = new StatusMember(1);
     //when
     statusMember.accept(messageData);
     //then

data-locality/src/main/java/com/iluwatar/data/locality/Application.java

@@ -46,7 +46,7 @@ public class Application {
    */
   public static void main(String[] args) {
     LOGGER.info("Start Game Application using Data-Locality pattern");
-    GameEntity gameEntity = new GameEntity(NUM_ENTITIES);
+    var gameEntity = new GameEntity(NUM_ENTITIES);
     gameEntity.start();
     gameEntity.update();
   }

data-locality/src/main/java/com/iluwatar/data/locality/game/component/manager/AiComponentManager.java

@@ -25,6 +25,7 @@ package com.iluwatar.data.locality.game.component.manager;
 
 import com.iluwatar.data.locality.game.component.AiComponent;
 import com.iluwatar.data.locality.game.component.Component;
+import java.util.stream.IntStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -50,9 +51,7 @@ public class AiComponentManager {
    */
   public void start() {
     LOGGER.info("Start AI Game Component");
-    for (int i = 0; i < numEntities; i++) {
+    IntStream.range(0, numEntities).forEach(i -> AI_COMPONENTS[i] = new AiComponent());
-      AI_COMPONENTS[i] = new AiComponent();
-    }
   }
 
   /**
@@ -60,10 +59,8 @@ public class AiComponentManager {
    */
   public void update() {
     LOGGER.info("Update AI Game Component");
-    for (int i = 0; i < numEntities; i++) {
+    IntStream.range(0, numEntities)
-      if (AI_COMPONENTS.length > i && AI_COMPONENTS[i] != null) {
+        .filter(i -> AI_COMPONENTS.length > i && AI_COMPONENTS[i] != null)
-        AI_COMPONENTS[i].update();
+        .forEach(i -> AI_COMPONENTS[i].update());
-      }
-    }
   }
 }

data-locality/src/main/java/com/iluwatar/data/locality/game/component/manager/PhysicsComponentManager.java

@@ -25,6 +25,7 @@ package com.iluwatar.data.locality.game.component.manager;
 
 import com.iluwatar.data.locality.game.component.Component;
 import com.iluwatar.data.locality.game.component.PhysicsComponent;
+import java.util.stream.IntStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -50,9 +51,7 @@ public class PhysicsComponentManager {
    */
   public void start() {
     LOGGER.info("Start Physics Game Component ");
-    for (int i = 0; i < numEntities; i++) {
+    IntStream.range(0, numEntities).forEach(i -> PHYSICS_COMPONENTS[i] = new PhysicsComponent());
-      PHYSICS_COMPONENTS[i] = new PhysicsComponent();
-    }
   }
 
 
@@ -62,10 +61,8 @@ public class PhysicsComponentManager {
   public void update() {
     LOGGER.info("Update Physics Game Component ");
     // Process physics.
-    for (int i = 0; i < numEntities; i++) {
+    IntStream.range(0, numEntities)
-      if (PHYSICS_COMPONENTS.length > i && PHYSICS_COMPONENTS[i] != null) {
+        .filter(i -> PHYSICS_COMPONENTS.length > i && PHYSICS_COMPONENTS[i] != null)
-        PHYSICS_COMPONENTS[i].update();
+        .forEach(i -> PHYSICS_COMPONENTS[i].update());
-      }
-    }
   }
 }

data-locality/src/main/java/com/iluwatar/data/locality/game/component/manager/RenderComponentManager.java

@@ -25,6 +25,7 @@ package com.iluwatar.data.locality.game.component.manager;
 
 import com.iluwatar.data.locality.game.component.Component;
 import com.iluwatar.data.locality.game.component.RenderComponent;
+import java.util.stream.IntStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -50,9 +51,7 @@ public class RenderComponentManager {
    */
   public void start() {
     LOGGER.info("Start Render Game Component ");
-    for (int i = 0; i < numEntities; i++) {
+    IntStream.range(0, numEntities).forEach(i -> RENDER_COMPONENTS[i] = new RenderComponent());
-      RENDER_COMPONENTS[i] = new RenderComponent();
-    }
   }
 
 
@@ -62,10 +61,8 @@ public class RenderComponentManager {
   public void render() {
     LOGGER.info("Update Render Game Component ");
     // Process Render.
-    for (int i = 0; i < numEntities; i++) {
+    IntStream.range(0, numEntities)
-      if (RENDER_COMPONENTS.length > i && RENDER_COMPONENTS[i] != null) {
+        .filter(i -> RENDER_COMPONENTS.length > i && RENDER_COMPONENTS[i] != null)
-        RENDER_COMPONENTS[i].render();
+        .forEach(i -> RENDER_COMPONENTS[i].render());
-      }
-    }
   }
 }

data-mapper/src/main/java/com/iluwatar/datamapper/App.java

@@ -23,7 +23,6 @@
 
 package com.iluwatar.datamapper;
 
-import java.util.Optional;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -51,10 +50,10 @@ public final class App {
   public static void main(final String... args) {
 
     /* Create new data mapper for type 'first' */
-    final StudentDataMapper mapper = new StudentDataMapperImpl();
+    final var mapper = new StudentDataMapperImpl();
 
     /* Create new student */
-    Student student = new Student(1, "Adam", 'A');
+    var student = new Student(1, "Adam", 'A');
 
     /* Add student in respectibe store */
     mapper.insert(student);
@@ -62,7 +61,7 @@ public final class App {
     log.debug(STUDENT_STRING + student + ", is inserted");
 
     /* Find this student */
-    final Optional<Student> studentToBeFound = mapper.find(student.getStudentId());
+    final var studentToBeFound = mapper.find(student.getStudentId());
 
     log.debug(STUDENT_STRING + studentToBeFound + ", is searched");
 

data-mapper/src/main/java/com/iluwatar/datamapper/Student.java

@@ -85,7 +85,7 @@ public final class Student implements Serializable {
       isEqual = true;
     } else if (inputObject != null && getClass() == inputObject.getClass()) {
 
-      final Student inputStudent = (Student) inputObject;
+      final var inputStudent = (Student) inputObject;
 
       /* If student id matched */
       if (this.getStudentId() == inputStudent.getStudentId()) {

data-mapper/src/main/java/com/iluwatar/datamapper/StudentDataMapperImpl.java

@@ -37,71 +37,36 @@ public final class StudentDataMapperImpl implements StudentDataMapper {
 
   @Override
   public Optional<Student> find(int studentId) {
-
+    return this.getStudents().stream().filter(x -> x.getStudentId() == studentId).findFirst();
-    /* Compare with existing students */
-    for (final Student student : this.getStudents()) {
-
-      /* Check if student is found */
-      if (student.getStudentId() == studentId) {
-
-        return Optional.of(student);
-      }
-    }
-
-    /* Return empty value */
-    return Optional.empty();
   }
 
   @Override
   public void update(Student studentToBeUpdated) throws DataMapperException {
-
+    String name = studentToBeUpdated.getName();
-
+    Integer index = Optional.of(studentToBeUpdated)
-    /* Check with existing students */
+        .map(Student::getStudentId)
-    if (this.getStudents().contains(studentToBeUpdated)) {
+        .flatMap(this::find)
-
+        .map(students::indexOf)
-      /* Get the index of student in list */
+        .orElseThrow(() -> new DataMapperException("Student [" + name + "] is not found"));
-      final int index = this.getStudents().indexOf(studentToBeUpdated);
+    students.set(index, studentToBeUpdated);
-
-      /* Update the student in list */
-      this.getStudents().set(index, studentToBeUpdated);
-
-    } else {
-
-      /* Throw user error after wrapping in a runtime exception */
-      throw new DataMapperException("Student [" + studentToBeUpdated.getName() + "] is not found");
-    }
   }
 
   @Override
   public void insert(Student studentToBeInserted) throws DataMapperException {
-
+    Optional<Student> student = find(studentToBeInserted.getStudentId());
-    /* Check with existing students */
+    if (student.isPresent()) {
-    if (!this.getStudents().contains(studentToBeInserted)) {
+      String name = studentToBeInserted.getName();
-
+      throw new DataMapperException("Student already [" + name + "] exists");
-      /* Add student in list */
-      this.getStudents().add(studentToBeInserted);
-
-    } else {
-
-      /* Throw user error after wrapping in a runtime exception */
-      throw new DataMapperException("Student already [" + studentToBeInserted
-          .getName() + "] exists");
     }
+
+    students.add(studentToBeInserted);
   }
 
   @Override
   public void delete(Student studentToBeDeleted) throws DataMapperException {
-
+    if (!students.remove(studentToBeDeleted)) {
-    /* Check with existing students */
+      String name = studentToBeDeleted.getName();
-    if (this.getStudents().contains(studentToBeDeleted)) {
+      throw new DataMapperException("Student [" + name + "] is not found");
-
-      /* Delete the student from list */
-      this.getStudents().remove(studentToBeDeleted);
-
-    } else {
-
-      /* Throw user error after wrapping in a runtime exception */
-      throw new DataMapperException("Student [" + studentToBeDeleted.getName() + "] is not found");
     }
   }
 

data-mapper/src/test/java/com/iluwatar/datamapper/AppTest.java

@@ -32,7 +32,6 @@ public final class AppTest {
 
   @Test
   public void test() {
-    final String[] args = {};
+    App.main();
-    App.main(args);
   }
 }

data-mapper/src/test/java/com/iluwatar/datamapper/DataMapperTest.java

@@ -23,11 +23,11 @@
 
 package com.iluwatar.datamapper;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * The Data Mapper (DM) is a layer of software that separates the in-memory objects from the
  * database. Its responsibility is to transfer data between the two and also to isolate them from
@@ -46,11 +46,11 @@ public class DataMapperTest {
   public void testFirstDataMapper() {
 
     /* Create new data mapper of first type */
-    final StudentDataMapper mapper = new StudentDataMapperImpl();
+    final var mapper = new StudentDataMapperImpl();
 
     /* Create new student */
-    int studentId = 1;
+    var studentId = 1;
-    Student student = new Student(studentId, "Adam", 'A');
+    var student = new Student(studentId, "Adam", 'A');
 
     /* Add student in respectibe db */
     mapper.insert(student);
@@ -59,7 +59,7 @@ public class DataMapperTest {
     assertEquals(studentId, mapper.find(student.getStudentId()).get().getStudentId());
 
     /* Update existing student object */
-    String updatedName = "AdamUpdated";
+    var updatedName = "AdamUpdated";
     student = new Student(student.getStudentId(), updatedName, 'A');
 
     /* Update student in respectibe db */

data-mapper/src/test/java/com/iluwatar/datamapper/StudentTest.java

@@ -23,12 +23,10 @@
 
 package com.iluwatar.datamapper;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
 
 /**
  * Tests {@link Student}.
@@ -36,8 +34,8 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 public final class StudentTest {
 
   /**
-   * This API tests the equality behaviour of Student object
+   * This API tests the equality behaviour of Student object Object Equality should work as per
-   * Object Equality should work as per logic defined in equals method
+   * logic defined in equals method
    *
    * @throws Exception if any execution error during test
    */
@@ -45,9 +43,9 @@ public final class StudentTest {
   public void testEquality() throws Exception {
 
     /* Create some students */
-    final Student firstStudent = new Student(1, "Adam", 'A');
+    final var firstStudent = new Student(1, "Adam", 'A');
-    final Student secondStudent = new Student(2, "Donald", 'B');
+    final var secondStudent = new Student(2, "Donald", 'B');
-    final Student secondSameStudent = new Student(2, "Donald", 'B');
+    final var secondSameStudent = new Student(2, "Donald", 'B');
 
     /* Check equals functionality: should return 'true' */
     assertEquals(firstStudent, firstStudent);

data-transfer-object/src/main/java/com/iluwatar/datatransfer/CustomerClientApp.java

@@ -48,16 +48,14 @@ public class CustomerClientApp {
    * @param args program argument.
    */
   public static void main(String[] args) {
-    List<CustomerDto> customers = new ArrayList<>();
+    var customerOne = new CustomerDto("1", "Kelly", "Brown");
-    CustomerDto customerOne = new CustomerDto("1", "Kelly", "Brown");
+    var customerTwo = new CustomerDto("2", "Alfonso", "Bass");
-    CustomerDto customerTwo = new CustomerDto("2", "Alfonso", "Bass");
+    var customers = new ArrayList<>(List.of(customerOne, customerTwo));
-    customers.add(customerOne);
-    customers.add(customerTwo);
 
-    CustomerResource customerResource = new CustomerResource(customers);
+    var customerResource = new CustomerResource(customers);
 
     LOGGER.info("All customers:-");
-    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
+    var allCustomers = customerResource.getAllCustomers();
     printCustomerDetails(allCustomers);
 
     LOGGER.info("----------------------------------------------------------");
@@ -70,7 +68,7 @@ public class CustomerClientApp {
     LOGGER.info("----------------------------------------------------------");
 
     LOGGER.info("Adding customer three}");
-    CustomerDto customerThree = new CustomerDto("3", "Lynda", "Blair");
+    var customerThree = new CustomerDto("3", "Lynda", "Blair");
     customerResource.save(customerThree);
     allCustomers = customerResource.getAllCustomers();
     printCustomerDetails(allCustomers);

data-transfer-object/src/test/java/com/iluwatar/datatransfer/CustomerResourceTest.java

@@ -23,13 +23,12 @@
 
 package com.iluwatar.datatransfer;
 
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.ArrayList;
 import java.util.List;
-
+import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
 
 /**
  * tests {@link CustomerResource}.
@@ -37,13 +36,9 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 public class CustomerResourceTest {
   @Test
   public void shouldGetAllCustomers() {
-    CustomerDto customer = new CustomerDto("1", "Melody", "Yates");
+    var customers = List.of(new CustomerDto("1", "Melody", "Yates"));
-    List<CustomerDto> customers = new ArrayList<>();
+    var customerResource = new CustomerResource(customers);
-    customers.add(customer);
+    var allCustomers = customerResource.getAllCustomers();
-
-    CustomerResource customerResource = new CustomerResource(customers);
-
-    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
 
     assertEquals(1, allCustomers.size());
     assertEquals("1", allCustomers.get(0).getId());
@@ -53,12 +48,12 @@ public class CustomerResourceTest {
 
   @Test
   public void shouldSaveCustomer() {
-    CustomerDto customer = new CustomerDto("1", "Rita", "Reynolds");
+    var customer = new CustomerDto("1", "Rita", "Reynolds");
-    CustomerResource customerResource = new CustomerResource(new ArrayList<>());
+    var customerResource = new CustomerResource(new ArrayList<>());
 
     customerResource.save(customer);
 
-    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
+    var allCustomers = customerResource.getAllCustomers();
     assertEquals("1", allCustomers.get(0).getId());
     assertEquals("Rita", allCustomers.get(0).getFirstName());
     assertEquals("Reynolds", allCustomers.get(0).getLastName());
@@ -66,15 +61,13 @@ public class CustomerResourceTest {
 
   @Test
   public void shouldDeleteCustomer() {
-    CustomerDto customer = new CustomerDto("1", "Terry", "Nguyen");
+    var customer = new CustomerDto("1", "Terry", "Nguyen");
-    List<CustomerDto> customers = new ArrayList<>();
+    var customers = new ArrayList<>(List.of(customer));
-    customers.add(customer);
+    var customerResource = new CustomerResource(customers);
-
-    CustomerResource customerResource = new CustomerResource(customers);
 
     customerResource.delete(customer.getId());
 
-    List<CustomerDto> allCustomers = customerResource.getAllCustomers();
+    var allCustomers = customerResource.getAllCustomers();
     assertTrue(allCustomers.isEmpty());
   }
 

decorator/README.md

@@ -98,12 +98,12 @@ Here's the troll in action
 
 ```java
 // simple troll
-Troll troll = new SimpleTroll();
+var troll = new SimpleTroll();
 troll.attack(); // The troll tries to grab you!
 troll.fleeBattle(); // The troll shrieks in horror and runs away!
 
 // change the behavior of the simple troll by adding a decorator
-Troll clubbedTroll = new ClubbedTroll(troll);
+var clubbedTroll = new ClubbedTroll(troll);
 clubbedTroll.attack(); // The troll tries to grab you! The troll swings at you with a club!
 clubbedTroll.fleeBattle(); // The troll shrieks in horror and runs away!
 ```

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

@@ -49,14 +49,14 @@ public class App {
 
     // simple troll
     LOGGER.info("A simple looking troll approaches.");
-    Troll troll = new SimpleTroll();
+    var troll = new SimpleTroll();
     troll.attack();
     troll.fleeBattle();
     LOGGER.info("Simple troll power {}.\n", troll.getAttackPower());
 
     // change the behavior of the simple troll by adding a decorator
     LOGGER.info("A troll with huge club surprises you.");
-    Troll clubbedTroll = new ClubbedTroll(troll);
+    var clubbedTroll = new ClubbedTroll(troll);
     clubbedTroll.attack();
     clubbedTroll.fleeBattle();
     LOGGER.info("Clubbed troll power {}.\n", clubbedTroll.getAttackPower());

decorator/src/test/java/com/iluwatar/decorator/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.decorator;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

decorator/src/test/java/com/iluwatar/decorator/ClubbedTrollTest.java

@@ -23,14 +23,14 @@
 
 package com.iluwatar.decorator;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.internal.verification.VerificationModeFactory.times;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Tests for {@link ClubbedTroll}
  */
@@ -39,10 +39,10 @@ public class ClubbedTrollTest {
   @Test
   public void testClubbedTroll() {
     // Create a normal troll first, but make sure we can spy on it later on.
-    final Troll simpleTroll = spy(new SimpleTroll());
+    final var simpleTroll = spy(new SimpleTroll());
 
     // Now we want to decorate the troll to make it stronger ...
-    final Troll clubbed = new ClubbedTroll(simpleTroll);
+    final var clubbed = new ClubbedTroll(simpleTroll);
     assertEquals(20, clubbed.getAttackPower());
     verify(simpleTroll, times(1)).getAttackPower();
 

decorator/src/test/java/com/iluwatar/decorator/SimpleTrollTest.java

@@ -23,19 +23,18 @@
 
 package com.iluwatar.decorator;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import ch.qos.logback.classic.Logger;
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.AppenderBase;
+import java.util.LinkedList;
+import java.util.List;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.LoggerFactory;
 
-import java.util.LinkedList;
-import java.util.List;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
 /**
  * Tests for {@link SimpleTroll}
  */
@@ -55,7 +54,7 @@ public class SimpleTrollTest {
 
   @Test
   public void testTrollActions() {
-    final SimpleTroll troll = new SimpleTroll();
+    final var troll = new SimpleTroll();
     assertEquals(10, troll.getAttackPower());
 
     troll.attack();

delegation/src/main/java/com/iluwatar/delegation/simple/App.java

@@ -51,9 +51,9 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    PrinterController hpPrinterController = new PrinterController(new HpPrinter());
+    var hpPrinterController = new PrinterController(new HpPrinter());
-    PrinterController canonPrinterController = new PrinterController(new CanonPrinter());
+    var canonPrinterController = new PrinterController(new CanonPrinter());
-    PrinterController epsonPrinterController = new PrinterController(new EpsonPrinter());
+    var epsonPrinterController = new PrinterController(new EpsonPrinter());
 
     hpPrinterController.print(MESSAGE_TO_PRINT);
     canonPrinterController.print(MESSAGE_TO_PRINT);

delegation/src/test/java/com/iluwatar/delegation/simple/AppTest.java

@@ -32,8 +32,7 @@ public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 
 }

delegation/src/test/java/com/iluwatar/delegation/simple/DelegateTest.java

@@ -23,22 +23,21 @@
 
 package com.iluwatar.delegation.simple;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import ch.qos.logback.classic.Logger;
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.AppenderBase;
 import com.iluwatar.delegation.simple.printers.CanonPrinter;
 import com.iluwatar.delegation.simple.printers.EpsonPrinter;
 import com.iluwatar.delegation.simple.printers.HpPrinter;
+import java.util.LinkedList;
+import java.util.List;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.LoggerFactory;
 
-import java.util.LinkedList;
-import java.util.List;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
 /**
  * Test for Delegation Pattern
  */
@@ -60,7 +59,7 @@ public class DelegateTest {
 
   @Test
   public void testCanonPrinter() throws Exception {
-    PrinterController printerController = new PrinterController(new CanonPrinter());
+    var printerController = new PrinterController(new CanonPrinter());
     printerController.print(MESSAGE);
 
     assertEquals("Canon Printer : Test Message Printed", appender.getLastMessage());
@@ -68,7 +67,7 @@ public class DelegateTest {
 
   @Test
   public void testHpPrinter() throws Exception {
-    PrinterController printerController = new PrinterController(new HpPrinter());
+    var printerController = new PrinterController(new HpPrinter());
     printerController.print(MESSAGE);
 
     assertEquals("HP Printer : Test Message Printed", appender.getLastMessage());
@@ -76,7 +75,7 @@ public class DelegateTest {
 
   @Test
   public void testEpsonPrinter() throws Exception {
-    PrinterController printerController = new PrinterController(new EpsonPrinter());
+    var printerController = new PrinterController(new EpsonPrinter());
     printerController.print(MESSAGE);
 
     assertEquals("Epson Printer : Test Message Printed", appender.getLastMessage());

dependency-injection/src/main/java/com/iluwatar/dependency/injection/App.java

@@ -24,7 +24,6 @@
 package com.iluwatar.dependency.injection;
 
 import com.google.inject.Guice;
-import com.google.inject.Injector;
 
 /**
  * Dependency Injection pattern deals with how objects handle their dependencies. The pattern
@@ -55,18 +54,18 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    SimpleWizard simpleWizard = new SimpleWizard();
+    var simpleWizard = new SimpleWizard();
     simpleWizard.smoke();
 
-    AdvancedWizard advancedWizard = new AdvancedWizard(new SecondBreakfastTobacco());
+    var advancedWizard = new AdvancedWizard(new SecondBreakfastTobacco());
     advancedWizard.smoke();
 
-    AdvancedSorceress advancedSorceress = new AdvancedSorceress();
+    var advancedSorceress = new AdvancedSorceress();
     advancedSorceress.setTobacco(new SecondBreakfastTobacco());
     advancedSorceress.smoke();
 
-    Injector injector = Guice.createInjector(new TobaccoModule());
+    var injector = Guice.createInjector(new TobaccoModule());
-    GuiceWizard guiceWizard = injector.getInstance(GuiceWizard.class);
+    var guiceWizard = injector.getInstance(GuiceWizard.class);
     guiceWizard.smoke();
   }
 }

dependency-injection/src/test/java/com/iluwatar/dependency/injection/AdvancedSorceressTest.java

@@ -23,13 +23,14 @@
 
 package com.iluwatar.dependency.injection;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import com.iluwatar.dependency.injection.utils.InMemoryAppender;
+import java.util.List;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
 
 /**
  * Date: 28/04/17 - 7:40 AM
@@ -52,27 +53,29 @@ public class AdvancedSorceressTest {
   }
 
   /**
-   * Test if the {@link AdvancedSorceress} smokes whatever instance of {@link Tobacco} is passed to her
+   * Test if the {@link AdvancedSorceress} smokes whatever instance of {@link Tobacco} is passed to
-   * through the setter's parameter
+   * her through the setter's parameter
    */
   @Test
   public void testSmokeEveryThing() throws Exception {
 
-    final Tobacco[] tobaccos = {
+    List<Tobacco> tobaccos = List.of(
-        new OldTobyTobacco(), new RivendellTobacco(), new SecondBreakfastTobacco()
+        new OldTobyTobacco(),
-    };
+        new RivendellTobacco(),
+        new SecondBreakfastTobacco()
+    );
 
-    for (final Tobacco tobacco : tobaccos) {
+    // Verify if the sorceress is smoking the correct tobacco ...
-      final AdvancedSorceress advancedSorceress = new AdvancedSorceress();
+    tobaccos.forEach(tobacco -> {
+      final var advancedSorceress = new AdvancedSorceress();
       advancedSorceress.setTobacco(tobacco);
       advancedSorceress.smoke();
-      // Verify if the sorceress is smoking the correct tobacco ...
+      String lastMessage = appender.getLastMessage();
-      assertEquals("AdvancedSorceress smoking " + tobacco.getClass().getSimpleName(), appender.getLastMessage());
+      assertEquals("AdvancedSorceress smoking " + tobacco.getClass().getSimpleName(), lastMessage);
-
+    });
-    }
 
     // ... and nothing else is happening.
-    assertEquals(tobaccos.length, appender.getLogSize());
+    assertEquals(tobaccos.size(), appender.getLogSize());
 
   }
 }

dependency-injection/src/test/java/com/iluwatar/dependency/injection/AdvancedWizardTest.java

@@ -23,13 +23,14 @@
 
 package com.iluwatar.dependency.injection;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import com.iluwatar.dependency.injection.utils.InMemoryAppender;
+import java.util.List;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
 
 /**
  * Date: 12/10/15 - 8:40 PM
@@ -57,21 +58,22 @@ public class AdvancedWizardTest {
   @Test
   public void testSmokeEveryThing() throws Exception {
 
-    final Tobacco[] tobaccos = {
+    List<Tobacco> tobaccos = List.of(
-        new OldTobyTobacco(), new RivendellTobacco(), new SecondBreakfastTobacco()
+        new OldTobyTobacco(),
-    };
+        new RivendellTobacco(),
+        new SecondBreakfastTobacco()
+    );
 
-    for (final Tobacco tobacco : tobaccos) {
+    // Verify if the wizard is smoking the correct tobacco ...
+    tobaccos.forEach(tobacco -> {
       final AdvancedWizard advancedWizard = new AdvancedWizard(tobacco);
       advancedWizard.smoke();
-
+      String lastMessage = appender.getLastMessage();
-      // Verify if the wizard is smoking the correct tobacco ...
+      assertEquals("AdvancedWizard smoking " + tobacco.getClass().getSimpleName(), lastMessage);
-      assertEquals("AdvancedWizard smoking " + tobacco.getClass().getSimpleName(), appender.getLastMessage());
+    });
-
-    }
 
     // ... and nothing else is happening.
-    assertEquals(tobaccos.length, appender.getLogSize());
+    assertEquals(tobaccos.size(), appender.getLogSize());
 
   }
 

dependency-injection/src/test/java/com/iluwatar/dependency/injection/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.dependency.injection;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

dependency-injection/src/test/java/com/iluwatar/dependency/injection/GuiceWizardTest.java

@@ -23,16 +23,16 @@
 
 package com.iluwatar.dependency.injection;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
-import com.google.inject.Injector;
 import com.iluwatar.dependency.injection.utils.InMemoryAppender;
+import java.util.List;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
 /**
  * Date: 12/10/15 - 8:57 PM
  *
@@ -59,20 +59,22 @@ public class GuiceWizardTest {
   @Test
   public void testSmokeEveryThingThroughConstructor() throws Exception {
 
-    final Tobacco[] tobaccos = {
+    List<Tobacco> tobaccos = List.of(
-        new OldTobyTobacco(), new RivendellTobacco(), new SecondBreakfastTobacco()
+        new OldTobyTobacco(),
-    };
+        new RivendellTobacco(),
+        new SecondBreakfastTobacco()
+    );
 
-    for (final Tobacco tobacco : tobaccos) {
+    // Verify if the wizard is smoking the correct tobacco ...
+    tobaccos.forEach(tobacco -> {
       final GuiceWizard guiceWizard = new GuiceWizard(tobacco);
       guiceWizard.smoke();
-
+      String lastMessage = appender.getLastMessage();
-      // Verify if the wizard is smoking the correct tobacco ...
+      assertEquals("GuiceWizard smoking " + tobacco.getClass().getSimpleName(), lastMessage);
-      assertEquals("GuiceWizard smoking " + tobacco.getClass().getSimpleName(), appender.getLastMessage());
+    });
-    }
 
     // ... and nothing else is happening.
-    assertEquals(tobaccos.length, appender.getLogSize());
+    assertEquals(tobaccos.size(), appender.getLogSize());
   }
 
   /**
@@ -82,30 +84,30 @@ public class GuiceWizardTest {
   @Test
   public void testSmokeEveryThingThroughInjectionFramework() throws Exception {
 
-    @SuppressWarnings("unchecked")
+    List<Class<? extends Tobacco>> tobaccos = List.of(
-    final Class<? extends Tobacco>[] tobaccos = new Class[]{
+        OldTobyTobacco.class,
-        OldTobyTobacco.class, RivendellTobacco.class, SecondBreakfastTobacco.class
+        RivendellTobacco.class,
-    };
+        SecondBreakfastTobacco.class
+    );
 
-    for (final Class<? extends Tobacco> tobaccoClass : tobaccos) {
+    // Configure the tobacco in the injection framework ...
-      // Configure the tobacco in the injection framework ...
+    // ... and create a new wizard with it
-      final Injector injector = Guice.createInjector(new AbstractModule() {
+    // Verify if the wizard is smoking the correct tobacco ...
+    tobaccos.forEach(tobaccoClass -> {
+      final var injector = Guice.createInjector(new AbstractModule() {
         @Override
         protected void configure() {
           bind(Tobacco.class).to(tobaccoClass);
         }
       });
-
+      final var guiceWizard = injector.getInstance(GuiceWizard.class);
-      // ... and create a new wizard with it
-      final GuiceWizard guiceWizard = injector.getInstance(GuiceWizard.class);
       guiceWizard.smoke();
-
+      String lastMessage = appender.getLastMessage();
-      // Verify if the wizard is smoking the correct tobacco ...
+      assertEquals("GuiceWizard smoking " + tobaccoClass.getSimpleName(), lastMessage);
-      assertEquals("GuiceWizard smoking " + tobaccoClass.getSimpleName(), appender.getLastMessage());
+    });
-    }
 
     // ... and nothing else is happening.
-    assertEquals(tobaccos.length, appender.getLogSize());
+    assertEquals(tobaccos.size(), appender.getLogSize());
   }
 
 }

dependency-injection/src/test/java/com/iluwatar/dependency/injection/SimpleWizardTest.java

@@ -23,13 +23,13 @@
 
 package com.iluwatar.dependency.injection;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import com.iluwatar.dependency.injection.utils.InMemoryAppender;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
 /**
  * Date: 12/10/15 - 8:26 PM
  *
@@ -55,7 +55,7 @@ public class SimpleWizardTest {
    */
   @Test
   public void testSmoke() {
-    final SimpleWizard simpleWizard = new SimpleWizard();
+    final var simpleWizard = new SimpleWizard();
     simpleWizard.smoke();
     assertEquals("SimpleWizard smoking OldTobyTobacco", appender.getLastMessage());
     assertEquals(1, appender.getLogSize());

dirty-flag/src/main/java/com/iluwatar/dirtyflag/App.java

@@ -23,9 +23,7 @@
 
 package com.iluwatar.dirtyflag;
 
-import java.util.List;
 import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -61,18 +59,15 @@ public class App {
    * Program execution point.
    */
   public void run() {
-
+    final var executorService = Executors.newSingleThreadScheduledExecutor();
-    final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
     executorService.scheduleAtFixedRate(new Runnable() {
       final World world = new World();
 
       @Override
       public void run() {
-        List<String> countries = world.fetch();
+        var countries = world.fetch();
         LOGGER.info("Our world currently has the following countries:-");
-        for (String country : countries) {
+        countries.stream().map(country -> "\t" + country).forEach(LOGGER::info);
-          LOGGER.info("\t" + country);
-        }
       }
     }, 0, 15, TimeUnit.SECONDS); // Run at every 15 seconds.
   }
@@ -83,8 +78,7 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    App app = new App();
+    var app = new App();
-
     app.run();
   }
 

dirty-flag/src/main/java/com/iluwatar/dirtyflag/DataFetcher.java

@@ -27,8 +27,8 @@ import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.List;
+import java.util.stream.Collectors;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -62,24 +62,18 @@ public class DataFetcher {
    * @return List of strings
    */
   public List<String> fetch() {
-    ClassLoader classLoader = getClass().getClassLoader();
+    var classLoader = getClass().getClassLoader();
-    File file = new File(classLoader.getResource(filename).getFile());
+    var file = new File(classLoader.getResource(filename).getFile());
 
     if (isDirty(file.lastModified())) {
       LOGGER.info(filename + " is dirty! Re-fetching file content...");
-
+      try (var br = new BufferedReader(new FileReader(file))) {
-      List<String> data = new ArrayList<String>();
+        return br.lines().collect(Collectors.collectingAndThen(Collectors.toList(), List::copyOf));
-      try (BufferedReader br = new BufferedReader(new FileReader(file))) {
-        String line;
-        while ((line = br.readLine()) != null) {
-          data.add(line);
-        }
       } catch (IOException e) {
         e.printStackTrace();
       }
-      return data;
     }
 
-    return new ArrayList<String>();
+    return List.of();
   }
 }

dirty-flag/src/main/java/com/iluwatar/dirtyflag/World.java

@@ -47,10 +47,8 @@ public class World {
    * @return List of strings
    */
   public List<String> fetch() {
-    List<String> data = df.fetch();
+    var data = df.fetch();
-
     countries = data.isEmpty() ? countries : data;
-
     return countries;
   }
 }

dirty-flag/src/test/java/org/dirty/flag/AppTest.java

@@ -23,19 +23,15 @@
 
 package org.dirty.flag;
 
-import java.io.IOException;
-
-import org.junit.jupiter.api.Test;
-
 import com.iluwatar.dirtyflag.App;
+import org.junit.jupiter.api.Test;
 
 /**
  * Tests that Dirty-Flag example runs without errors.
  */
 public class AppTest {
   @Test
-  public void test() throws IOException {
+  public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

dirty-flag/src/test/java/org/dirty/flag/DirtyFlagTest.java

@@ -26,31 +26,26 @@ package org.dirty.flag;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
-import java.util.List;
+import com.iluwatar.dirtyflag.DataFetcher;
-
 import org.junit.jupiter.api.Test;
 
-import com.iluwatar.dirtyflag.DataFetcher;
-
 /**
- *
  * Application test
- *
  */
 public class DirtyFlagTest {
 
   @Test
   public void testIsDirty() {
-    DataFetcher df = new DataFetcher();
+    var df = new DataFetcher();
-    List<String> countries = df.fetch();
+    var countries = df.fetch();
     assertFalse(countries.isEmpty());
   }
 
   @Test
   public void testIsNotDirty() {
-    DataFetcher df = new DataFetcher();
+    var df = new DataFetcher();
     df.fetch();
-    List<String> countries = df.fetch();
+    var countries = df.fetch();
     assertTrue(countries.isEmpty());
   }
 }

double-buffer/src/main/java/com/iluwatar/doublebuffer/App.java

@@ -23,10 +23,8 @@
 
 package com.iluwatar.doublebuffer;
 
-import java.util.ArrayList;
 import java.util.List;
 import org.apache.commons.lang3.tuple.MutablePair;
-import org.apache.commons.lang3.tuple.Pair;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -48,37 +46,34 @@ public class App {
    */
   public static void main(String[] args) {
     final var scene = new Scene();
-    List<Pair<Integer, Integer>> drawPixels = new ArrayList<>();
+    var drawPixels1 = List.of(
-    Pair<Integer, Integer> pixel1 = new MutablePair<>(1, 1);
+        new MutablePair<>(1, 1),
-    Pair<Integer, Integer> pixel2 = new MutablePair<>(5, 6);
+        new MutablePair<>(5, 6),
-    Pair<Integer, Integer> pixel3 = new MutablePair<>(3, 2);
+        new MutablePair<>(3, 2)
-    drawPixels.add(pixel1);
+    );
-    drawPixels.add(pixel2);
+    scene.draw(drawPixels1);
-    drawPixels.add(pixel3);
-    scene.draw(drawPixels);
     var buffer1 = scene.getBuffer();
     printBlackPixelCoordinate(buffer1);
 
-    drawPixels.clear();
+    var drawPixels2 = List.of(
-    Pair<Integer, Integer> pixel4 = new MutablePair<>(3, 7);
+        new MutablePair<>(3, 7),
-    Pair<Integer, Integer> pixel5 = new MutablePair<>(6, 1);
+        new MutablePair<>(6, 1)
-    drawPixels.add(pixel4);
+    );
-    drawPixels.add(pixel5);
+    scene.draw(drawPixels2);
-    scene.draw(drawPixels);
+    var buffer2 = scene.getBuffer();
-    Buffer buffer2 = scene.getBuffer();
     printBlackPixelCoordinate(buffer2);
   }
 
   private static void printBlackPixelCoordinate(Buffer buffer) {
-    var log = "Black Pixels: ";
+    StringBuilder log = new StringBuilder("Black Pixels: ");
-    Pixel[] pixels = buffer.getPixels();
+    var pixels = buffer.getPixels();
     for (var i = 0; i < pixels.length; ++i) {
       if (pixels[i] == Pixel.BLACK) {
         var y = i / FrameBuffer.WIDTH;
         var x = i % FrameBuffer.WIDTH;
-        log += " (" + x + ", " + y + ")";
+        log.append(" (").append(x).append(", ").append(y).append(")");
       }
     }
-    LOGGER.info(log);
+    LOGGER.info(log.toString());
   }
 }

double-buffer/src/main/java/com/iluwatar/doublebuffer/FrameBuffer.java

@@ -23,6 +23,8 @@
 
 package com.iluwatar.doublebuffer;
 
+import java.util.Arrays;
+
 /**
  * FrameBuffer implementation class.
  */
@@ -49,9 +51,7 @@ public class FrameBuffer implements Buffer {
 
   @Override
   public void clearAll() {
-    for (var i = 0; i < pixels.length; ++i) {
+    Arrays.fill(pixels, Pixel.WHITE);
-      pixels[i] = Pixel.WHITE;
-    }
   }
 
   @Override

double-buffer/src/main/java/com/iluwatar/doublebuffer/Scene.java

@@ -57,15 +57,15 @@ public class Scene {
    *
    * @param coordinateList list of pixels of which the color should be black
    */
-  public void draw(List<Pair<Integer, Integer>> coordinateList) {
+  public void draw(List<? extends Pair<Integer, Integer>> coordinateList) {
     LOGGER.info("Start drawing next frame");
     LOGGER.info("Current buffer: " + current + " Next buffer: " + next);
     frameBuffers[next].clearAll();
-    for (Pair<Integer, Integer> coordinate : coordinateList) {
+    coordinateList.forEach(coordinate -> {
       var x = coordinate.getKey();
       var y = coordinate.getValue();
       frameBuffers[next].draw(x, y);
-    }
+    });
     LOGGER.info("Swap current and next buffer");
     swap();
     LOGGER.info("Finish swapping");

double-buffer/src/test/java/com/iluwatar/doublebuffer/AppTest.java

@@ -32,8 +32,7 @@ public class AppTest {
 
   @Test
   public void testMain() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 
 }

double-buffer/src/test/java/com/iluwatar/doublebuffer/FrameBufferTest.java

@@ -23,6 +23,7 @@
 
 package com.iluwatar.doublebuffer;
 
+import java.util.Arrays;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -35,10 +36,8 @@ public class FrameBufferTest {
   public void testClearAll() {
     try {
       var field = FrameBuffer.class.getDeclaredField("pixels");
-      Pixel[] pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
+      var pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
-      for (int i = 0; i < pixels.length; ++i) {
+      Arrays.fill(pixels, Pixel.WHITE);
-        pixels[i] = Pixel.WHITE;
-      }
       pixels[0] = Pixel.BLACK;
       var frameBuffer = new FrameBuffer();
       field.setAccessible(true);
@@ -54,10 +53,8 @@ public class FrameBufferTest {
   public void testClear() {
     try {
       var field = FrameBuffer.class.getDeclaredField("pixels");
-      Pixel[] pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
+      var pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
-      for (int i = 0; i < pixels.length; ++i) {
+      Arrays.fill(pixels, Pixel.WHITE);
-        pixels[i] = Pixel.WHITE;
-      }
       pixels[0] = Pixel.BLACK;
       var frameBuffer = new FrameBuffer();
       field.setAccessible(true);
@@ -80,10 +77,8 @@ public class FrameBufferTest {
   public void testGetPixels() {
     try {
       var field = FrameBuffer.class.getDeclaredField("pixels");
-      Pixel[] pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
+      var pixels = new Pixel[FrameBuffer.HEIGHT * FrameBuffer.WIDTH];
-      for (int i = 0; i < pixels.length; ++i) {
+      Arrays.fill(pixels, Pixel.WHITE);
-        pixels[i] = Pixel.WHITE;
-      }
       pixels[0] = Pixel.BLACK;
       var frameBuffer = new FrameBuffer();
       field.setAccessible(true);

double-buffer/src/test/java/com/iluwatar/doublebuffer/SceneTest.java

@@ -23,12 +23,10 @@
 
 package com.iluwatar.doublebuffer;
 
+import java.util.ArrayList;
 import org.junit.Assert;
 import org.junit.Test;
 
-import java.lang.reflect.Field;
-import java.util.ArrayList;
-
 /**
  * Scene unit tests.
  */
@@ -41,8 +39,8 @@ public class SceneTest {
       var field1 = Scene.class.getDeclaredField("current");
       field1.setAccessible(true);
       field1.set(scene, 0);
-      FrameBuffer[] frameBuffers = new FrameBuffer[2];
+      var frameBuffers = new FrameBuffer[2];
-      FrameBuffer frameBuffer = new FrameBuffer();
+      var frameBuffer = new FrameBuffer();
       frameBuffer.draw(0, 0);
       frameBuffers[0] = frameBuffer;
       var field2 = Scene.class.getDeclaredField("frameBuffers");

double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/App.java

@@ -23,9 +23,9 @@
 
 package com.iluwatar.doublechecked.locking;
 
-import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -50,15 +50,13 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    final Inventory inventory = new Inventory(1000);
+    final var inventory = new Inventory(1000);
-    ExecutorService executorService = Executors.newFixedThreadPool(3);
+    var executorService = Executors.newFixedThreadPool(3);
-    for (int i = 0; i < 3; i++) {
+    IntStream.range(0, 3).<Runnable>mapToObj(i -> () -> {
-      executorService.execute(() -> {
+      while (inventory.addItem(new Item())) {
-        while (inventory.addItem(new Item())) {
+        LOGGER.info("Adding another item");
-          LOGGER.info("Adding another item");
+      }
-        }
+    }).forEach(executorService::execute);
-      });
-    }
 
     executorService.shutdown();
     try {

double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/Inventory.java

@@ -24,7 +24,6 @@
 package com.iluwatar.doublechecked.locking;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
@@ -60,8 +59,8 @@ public class Inventory {
       try {
         if (items.size() < inventorySize) {
           items.add(item);
-          LOGGER.info("{}: items.size()={}, inventorySize={}", Thread.currentThread(), items
+          var thread = Thread.currentThread();
-              .size(), inventorySize);
+          LOGGER.info("{}: items.size()={}, inventorySize={}", thread, items.size(), inventorySize);
           return true;
         }
       } finally {
@@ -77,7 +76,7 @@ public class Inventory {
    * @return All the items of the inventory, as an unmodifiable list
    */
   public final List<Item> getItems() {
-    return Collections.unmodifiableList(items);
+    return List.copyOf(items);
   }
 
 }

double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.doublechecked.locking;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/InventoryTest.java

@@ -23,25 +23,24 @@
 
 package com.iluwatar.doublechecked.locking;
 
-import ch.qos.logback.classic.Logger;
-import ch.qos.logback.classic.spi.ILoggingEvent;
-import ch.qos.logback.core.AppenderBase;
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-import org.slf4j.LoggerFactory;
-
-import java.util.LinkedList;
-import java.util.List;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-
 import static java.time.Duration.ofMillis;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTimeout;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.AppenderBase;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
 
 /**
  * Date: 12/10/15 - 9:34 PM
@@ -83,34 +82,32 @@ public class InventoryTest {
   public void testAddItem() throws Exception {
     assertTimeout(ofMillis(10000), () -> {
       // Create a new inventory with a limit of 1000 items and put some load on the add method
-      final Inventory inventory = new Inventory(INVENTORY_SIZE);
+      final var inventory = new Inventory(INVENTORY_SIZE);
-      final ExecutorService executorService = Executors.newFixedThreadPool(THREAD_COUNT);
+      final var executorService = Executors.newFixedThreadPool(THREAD_COUNT);
-      for (int i = 0; i < THREAD_COUNT; i++) {
+      IntStream.range(0, THREAD_COUNT).<Runnable>mapToObj(i -> () -> {
-        executorService.execute(() -> {
+        while (inventory.addItem(new Item())) ;
-          while (inventory.addItem(new Item())) {};
+      }).forEach(executorService::execute);
-        });
-      }
 
       // Wait until all threads have finished
       executorService.shutdown();
       executorService.awaitTermination(5, TimeUnit.SECONDS);
 
       // Check the number of items in the inventory. It should not have exceeded the allowed maximum
-      final List<Item> items = inventory.getItems();
+      final var items = inventory.getItems();
       assertNotNull(items);
       assertEquals(INVENTORY_SIZE, items.size());
 
       assertEquals(INVENTORY_SIZE, appender.getLogSize());
 
       // ... and check if the inventory size is increasing continuously
-      for (int i = 0; i < items.size(); i++) {
+      IntStream.range(0, items.size())
-        assertTrue(appender.log.get(i).getFormattedMessage().contains("items.size()=" + (i + 1)));
+          .mapToObj(i -> appender.log.get(i).getFormattedMessage()
-      }
+              .contains("items.size()=" + (i + 1)))
+          .forEach(Assertions::assertTrue);
     });
   }
 
 
-
   private class InMemoryAppender extends AppenderBase<ILoggingEvent> {
     private List<ILoggingEvent> log = new LinkedList<>();
 

double-dispatch/src/main/java/com/iluwatar/doubledispatch/App.java

@@ -57,16 +57,17 @@ public class App {
    */
   public static void main(String[] args) {
     // initialize game objects and print their status
-    List<GameObject> objects = List.of(
+    var objects = List.of(
         new FlamingAsteroid(0, 0, 5, 5),
         new SpaceStationMir(1, 1, 2, 2),
         new Meteoroid(10, 10, 15, 15),
-        new SpaceStationIss(12, 12, 14, 14));
+        new SpaceStationIss(12, 12, 14, 14)
-    objects.stream().forEach(o -> LOGGER.info(o.toString()));
+    );
+    objects.forEach(o -> LOGGER.info(o.toString()));
     LOGGER.info("");
 
     // collision check
-    objects.stream().forEach(o1 -> objects.stream().forEach(o2 -> {
+    objects.forEach(o1 -> objects.forEach(o2 -> {
       if (o1 != o2 && o1.intersectsWith(o2)) {
         o1.collision(o2);
       }
@@ -74,7 +75,7 @@ public class App {
     LOGGER.info("");
 
     // output eventual object statuses
-    objects.stream().forEach(o -> LOGGER.info(o.toString()));
+    objects.forEach(o -> LOGGER.info(o.toString()));
     LOGGER.info("");
   }
 }

double-dispatch/src/test/java/com/iluwatar/doubledispatch/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.doubledispatch;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

double-dispatch/src/test/java/com/iluwatar/doubledispatch/CollisionTest.java

@@ -23,13 +23,13 @@
 
 package com.iluwatar.doubledispatch;
 
-import java.util.Objects;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import java.util.Objects;
+
 /**
- * Date: 12/10/15 - 8:37 PM
+ * Date: 12/10/15 - 8:37 PM Test for Collision
- * Test for Collision
+ *
  * @param <O> Type of GameObject
  * @author Jeroen Meulemeester
  */
@@ -51,15 +51,14 @@ public abstract class CollisionTest<O extends GameObject> {
    * @param otherOnFire  Indicates if the other object should be burning after the collision
    * @param thisDamaged  Indicates if the test object should be damaged after the collision
    * @param thisOnFire   Indicates if the other object should be burning after the collision
-   * @param description  The expected description of the collision
    */
   void testCollision(final GameObject other, final boolean otherDamaged, final boolean otherOnFire,
-                     final boolean thisDamaged, final boolean thisOnFire, final String description) {
+                     final boolean thisDamaged, final boolean thisOnFire) {
 
     Objects.requireNonNull(other);
     Objects.requireNonNull(getTestedObject());
 
-    final O tested = getTestedObject();
+    final var tested = getTestedObject();
 
     tested.collision(other);
 
@@ -80,10 +79,10 @@ public abstract class CollisionTest<O extends GameObject> {
    * @param expectTargetOnFire The expected state of fire on the target object
    */
   private void testOnFire(final GameObject target, final GameObject other, final boolean expectTargetOnFire) {
-    final String targetName = target.getClass().getSimpleName();
+    final var targetName = target.getClass().getSimpleName();
-    final String otherName = other.getClass().getSimpleName();
+    final var otherName = other.getClass().getSimpleName();
 
-    final String errorMessage = expectTargetOnFire
+    final var errorMessage = expectTargetOnFire
         ? "Expected [" + targetName + "] to be on fire after colliding with [" + otherName + "] but it was not!"
         : "Expected [" + targetName + "] not to be on fire after colliding with [" + otherName + "] but it was!";
 
@@ -99,10 +98,10 @@ public abstract class CollisionTest<O extends GameObject> {
    * @param expectedDamage The expected state of damage on the target object
    */
   private void testDamaged(final GameObject target, final GameObject other, final boolean expectedDamage) {
-    final String targetName = target.getClass().getSimpleName();
+    final var targetName = target.getClass().getSimpleName();
-    final String otherName = other.getClass().getSimpleName();
+    final var otherName = other.getClass().getSimpleName();
 
-    final String errorMessage = expectedDamage
+    final var errorMessage = expectedDamage
         ? "Expected [" + targetName + "] to be damaged after colliding with [" + otherName + "] but it was not!"
         : "Expected [" + targetName + "] not to be damaged after colliding with [" + otherName + "] but it was!";
 

double-dispatch/src/test/java/com/iluwatar/doubledispatch/FlamingAsteroidTest.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.doubledispatch;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/10/15 - 11:31 PM
  *
@@ -46,7 +46,7 @@ public class FlamingAsteroidTest extends CollisionTest<FlamingAsteroid> {
    */
   @Test
   public void testConstructor() {
-    final FlamingAsteroid asteroid = new FlamingAsteroid(1, 2, 3, 4);
+    final var asteroid = new FlamingAsteroid(1, 2, 3, 4);
     assertEquals(1, asteroid.getLeft());
     assertEquals(2, asteroid.getTop());
     assertEquals(3, asteroid.getRight());
@@ -64,8 +64,7 @@ public class FlamingAsteroidTest extends CollisionTest<FlamingAsteroid> {
     testCollision(
         new FlamingAsteroid(1, 2, 3, 4),
         false, true,
-        false, true,
+        false, true
-        "FlamingAsteroid hits FlamingAsteroid."
     );
   }
 
@@ -77,8 +76,7 @@ public class FlamingAsteroidTest extends CollisionTest<FlamingAsteroid> {
     testCollision(
         new Meteoroid(1, 1, 3, 4),
         false, false,
-        false, true,
+        false, true
-        "FlamingAsteroid hits Meteoroid."
     );
   }
 
@@ -90,8 +88,7 @@ public class FlamingAsteroidTest extends CollisionTest<FlamingAsteroid> {
     testCollision(
         new SpaceStationIss(1, 1, 3, 4),
         true, true,
-        false, true,
+        false, true
-        "FlamingAsteroid hits SpaceStationIss. SpaceStationIss is damaged! SpaceStationIss is set on fire!"
     );
   }
 
@@ -103,8 +100,7 @@ public class FlamingAsteroidTest extends CollisionTest<FlamingAsteroid> {
     testCollision(
         new SpaceStationMir(1, 1, 3, 4),
         true, true,
-        false, true,
+        false, true
-        "FlamingAsteroid hits SpaceStationMir. SpaceStationMir is damaged! SpaceStationMir is set on fire!"
     );
   }
 

double-dispatch/src/test/java/com/iluwatar/doubledispatch/MeteoroidTest.java

@@ -23,11 +23,11 @@
 
 package com.iluwatar.doubledispatch;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/10/15 - 11:31 PM
  *
@@ -45,7 +45,7 @@ public class MeteoroidTest extends CollisionTest<Meteoroid> {
    */
   @Test
   public void testConstructor() {
-    final Meteoroid meteoroid = new Meteoroid(1, 2, 3, 4);
+    final var meteoroid = new Meteoroid(1, 2, 3, 4);
     assertEquals(1, meteoroid.getLeft());
     assertEquals(2, meteoroid.getTop());
     assertEquals(3, meteoroid.getRight());
@@ -63,8 +63,7 @@ public class MeteoroidTest extends CollisionTest<Meteoroid> {
     testCollision(
         new FlamingAsteroid(1, 1, 3, 4),
         false, true,
-        false, false,
+        false, false
-        "Meteoroid hits FlamingAsteroid."
     );
   }
 
@@ -76,8 +75,7 @@ public class MeteoroidTest extends CollisionTest<Meteoroid> {
     testCollision(
         new Meteoroid(1, 1, 3, 4),
         false, false,
-        false, false,
+        false, false
-        "Meteoroid hits Meteoroid."
     );
   }
 
@@ -89,8 +87,7 @@ public class MeteoroidTest extends CollisionTest<Meteoroid> {
     testCollision(
         new SpaceStationIss(1, 1, 3, 4),
         true, false,
-        false, false,
+        false, false
-        "Meteoroid hits SpaceStationIss. SpaceStationIss is damaged!"
     );
   }
 
@@ -102,8 +99,7 @@ public class MeteoroidTest extends CollisionTest<Meteoroid> {
     testCollision(
         new SpaceStationMir(1, 1, 3, 4),
         true, false,
-        false, false,
+        false, false
-        "Meteoroid hits SpaceStationMir. SpaceStationMir is damaged!"
     );
   }
 

double-dispatch/src/test/java/com/iluwatar/doubledispatch/RectangleTest.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.doubledispatch;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Unit test for Rectangle
  */
@@ -39,7 +39,7 @@ public class RectangleTest {
    */
   @Test
   public void testConstructor() {
-    final Rectangle rectangle = new Rectangle(1, 2, 3, 4);
+    final var rectangle = new Rectangle(1, 2, 3, 4);
     assertEquals(1, rectangle.getLeft());
     assertEquals(2, rectangle.getTop());
     assertEquals(3, rectangle.getRight());
@@ -52,7 +52,7 @@ public class RectangleTest {
    */
   @Test
   public void testToString() throws Exception {
-    final Rectangle rectangle = new Rectangle(1, 2, 3, 4);
+    final var rectangle = new Rectangle(1, 2, 3, 4);
     assertEquals("[1,2,3,4]", rectangle.toString());
   }
 

double-dispatch/src/test/java/com/iluwatar/doubledispatch/SpaceStationIssTest.java

@@ -23,11 +23,11 @@
 
 package com.iluwatar.doubledispatch;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/10/15 - 11:31 PM
  *
@@ -45,7 +45,7 @@ public class SpaceStationIssTest extends CollisionTest<SpaceStationIss> {
    */
   @Test
   public void testConstructor() {
-    final SpaceStationIss iss = new SpaceStationIss(1, 2, 3, 4);
+    final var iss = new SpaceStationIss(1, 2, 3, 4);
     assertEquals(1, iss.getLeft());
     assertEquals(2, iss.getTop());
     assertEquals(3, iss.getRight());
@@ -63,8 +63,7 @@ public class SpaceStationIssTest extends CollisionTest<SpaceStationIss> {
     testCollision(
         new FlamingAsteroid(1, 1, 3, 4),
         false, true,
-        false, false,
+        false, false
-        "SpaceStationIss hits FlamingAsteroid."
     );
   }
 
@@ -76,8 +75,7 @@ public class SpaceStationIssTest extends CollisionTest<SpaceStationIss> {
     testCollision(
         new Meteoroid(1, 1, 3, 4),
         false, false,
-        false, false,
+        false, false
-        "SpaceStationIss hits Meteoroid."
     );
   }
 
@@ -89,8 +87,7 @@ public class SpaceStationIssTest extends CollisionTest<SpaceStationIss> {
     testCollision(
         new SpaceStationIss(1, 1, 3, 4),
         true, false,
-        false, false,
+        false, false
-        "SpaceStationIss hits SpaceStationIss. SpaceStationIss is damaged!"
     );
   }
 
@@ -102,8 +99,7 @@ public class SpaceStationIssTest extends CollisionTest<SpaceStationIss> {
     testCollision(
         new SpaceStationMir(1, 1, 3, 4),
         true, false,
-        false, false,
+        false, false
-        "SpaceStationIss hits SpaceStationMir. SpaceStationMir is damaged!"
     );
   }
 

double-dispatch/src/test/java/com/iluwatar/doubledispatch/SpaceStationMirTest.java

@@ -23,11 +23,11 @@
 
 package com.iluwatar.doubledispatch;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/10/15 - 11:31 PM
  *
@@ -45,7 +45,7 @@ public class SpaceStationMirTest extends CollisionTest<SpaceStationMir> {
    */
   @Test
   public void testConstructor() {
-    final SpaceStationMir mir = new SpaceStationMir(1, 2, 3, 4);
+    final var mir = new SpaceStationMir(1, 2, 3, 4);
     assertEquals(1, mir.getLeft());
     assertEquals(2, mir.getTop());
     assertEquals(3, mir.getRight());
@@ -63,8 +63,7 @@ public class SpaceStationMirTest extends CollisionTest<SpaceStationMir> {
     testCollision(
         new FlamingAsteroid(1, 1, 3, 4),
         false, true,
-        false, false,
+        false, false
-        "SpaceStationMir hits FlamingAsteroid."
     );
   }
 
@@ -76,8 +75,7 @@ public class SpaceStationMirTest extends CollisionTest<SpaceStationMir> {
     testCollision(
         new Meteoroid(1, 1, 3, 4),
         false, false,
-        false, false,
+        false, false
-        "SpaceStationMir hits Meteoroid."
     );
   }
 
@@ -89,8 +87,7 @@ public class SpaceStationMirTest extends CollisionTest<SpaceStationMir> {
     testCollision(
         new SpaceStationIss(1, 1, 3, 4),
         true, false,
-        false, false,
+        false, false
-        "SpaceStationMir hits SpaceStationIss. SpaceStationIss is damaged!"
     );
   }
 
@@ -102,8 +99,7 @@ public class SpaceStationMirTest extends CollisionTest<SpaceStationMir> {
     testCollision(
         new SpaceStationMir(1, 1, 3, 4),
         true, false,
-        false, false,
+        false, false
-        "SpaceStationMir hits SpaceStationMir. SpaceStationMir is damaged!"
     );
   }