Java 11 migration: patterns (t-v) (#1085)

* Moves visitor pattern to java 11

* Moves value-object pattern to java 11

* Moves unit-of-work pattern to java 11

* Moves typeobjectpattern pattern to java 11

* Moves twin pattern to java 11

* Moves trampoline pattern to java 11

* Moves tolerant-reader pattern to java 11

* Moves tls pattern to java 11

* Moves throttling pattern to java 11

* Moves thread-pool pattern to java 11

* Moves template-method pattern to java 11

template-method/src/test/java/com/iluwatar/templatemethod/AppTest.java

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

template-method/src/test/java/com/iluwatar/templatemethod/HalflingThiefTest.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.templatemethod;
 
-import org.junit.jupiter.api.Test;
-
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/29/15 - 18:15 PM
  *
@@ -41,8 +41,8 @@ public class HalflingThiefTest {
    */
   @Test
   public void testSteal() {
-    final StealingMethod method = mock(StealingMethod.class);
-    final HalflingThief thief = new HalflingThief(method);
+    final var method = mock(StealingMethod.class);
+    final var thief = new HalflingThief(method);
 
     thief.steal();
     verify(method).steal();
@@ -55,13 +55,13 @@ public class HalflingThiefTest {
    */
   @Test
   public void testChangeMethod() {
-    final StealingMethod initialMethod = mock(StealingMethod.class);
-    final HalflingThief thief = new HalflingThief(initialMethod);
+    final var initialMethod = mock(StealingMethod.class);
+    final var thief = new HalflingThief(initialMethod);
 
     thief.steal();
     verify(initialMethod).steal();
 
-    final StealingMethod newMethod = mock(StealingMethod.class);
+    final var newMethod = mock(StealingMethod.class);
     thief.changeMethod(newMethod);
 
     thief.steal();

template-method/src/test/java/com/iluwatar/templatemethod/StealingMethodTest.java

@@ -23,6 +23,9 @@
 
 package com.iluwatar.templatemethod;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+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;
@@ -33,11 +36,9 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.LoggerFactory;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 /**
  * Date: 12/30/15 - 18:12 PM
+ *
  * @param <M> Type of StealingMethod
  * @author Jeroen Meulemeester
  */

thread-pool/src/main/java/com/iluwatar/threadpool/App.java

@@ -56,7 +56,7 @@ public class App {
     LOGGER.info("Program started");
 
     // Create a list of tasks to be executed
-    List<Task> tasks = List.of(
+    var tasks = List.of(
         new PotatoPeelingTask(3),
         new PotatoPeelingTask(6),
         new CoffeeMakingTask(2),
@@ -82,10 +82,7 @@ public class App {
     // Allocate new worker for each task
     // The worker is executed when a thread becomes
     // available in the thread pool
-    for (int i = 0; i < tasks.size(); i++) {
-      var worker = new Worker(tasks.get(i));
-      executor.execute(worker);
-    }
+    tasks.stream().map(Worker::new).forEach(executor::execute);
     // All tasks were executed, now shutdown
     executor.shutdown();
     while (!executor.isTerminated()) {

thread-pool/src/test/java/com/iluwatar/threadpool/AppTest.java

@@ -27,15 +27,13 @@ import org.junit.jupiter.api.Test;
 
 /**
  * Application test
- * 
- * @author ilkka
  *
+ * @author ilkka
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 }

thread-pool/src/test/java/com/iluwatar/threadpool/TaskTest.java

@@ -23,27 +23,25 @@
 
 package com.iluwatar.threadpool;
 
-import org.junit.jupiter.api.Test;
-
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Objects;
-import java.util.concurrent.Callable;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-import java.util.function.IntFunction;
-import java.util.stream.Collectors;
-
 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 java.util.ArrayList;
+import java.util.Objects;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.function.IntFunction;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import org.junit.jupiter.api.Test;
+
 /**
- * Date: 12/30/15 - 18:22 PM
- * Test for Tasks using a Thread Pool
+ * Date: 12/30/15 - 18:22 PM Test for Tasks using a Thread Pool
+ *
  * @param <T> Type of Task
  * @author Jeroen Meulemeester
  */
@@ -87,14 +85,13 @@ public abstract class TaskTest<T extends Task> {
   @Test
   public void testIdGeneration() throws Exception {
     assertTimeout(ofMillis(10000), () -> {
-      final ExecutorService service = Executors.newFixedThreadPool(THREAD_COUNT);
+      final var service = Executors.newFixedThreadPool(THREAD_COUNT);
 
-      final List<Callable<Integer>> tasks = new ArrayList<>();
-      for (int i = 0; i < TASK_COUNT; i++) {
-        tasks.add(() -> factory.apply(1).getId());
-      }
+      final var tasks = IntStream.range(0, TASK_COUNT)
+          .<Callable<Integer>>mapToObj(i -> () -> factory.apply(1).getId())
+          .collect(Collectors.toCollection(ArrayList::new));
 
-      final List<Integer> ids = service.invokeAll(tasks)
+      final var ids = service.invokeAll(tasks)
           .stream()
           .map(TaskTest::get)
           .filter(Objects::nonNull)
@@ -102,7 +99,7 @@ public abstract class TaskTest<T extends Task> {
 
       service.shutdownNow();
 
-      final long uniqueIdCount = ids.stream()
+      final var uniqueIdCount = ids.stream()
           .distinct()
           .count();
 
@@ -117,7 +114,7 @@ public abstract class TaskTest<T extends Task> {
    */
   @Test
   public void testTimeMs() {
-    for (int i = 0; i < 10; i++) {
+    for (var i = 0; i < 10; i++) {
       assertEquals(this.expectedExecutionTime * i, this.factory.apply(i).getTimeMs());
     }
   }

thread-pool/src/test/java/com/iluwatar/threadpool/WorkerTest.java

@@ -23,13 +23,13 @@
 
 package com.iluwatar.threadpool;
 
-import org.junit.jupiter.api.Test;
-
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.verifyZeroInteractions;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/30/15 - 18:21 PM
  *
@@ -42,8 +42,8 @@ public class WorkerTest {
    */
   @Test
   public void testRun() {
-    final Task task = mock(Task.class);
-    final Worker worker = new Worker(task);
+    final var task = mock(Task.class);
+    final var worker = new Worker(task);
     verifyZeroInteractions(task);
 
     worker.run();

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

@@ -26,6 +26,7 @@ package com.iluwatar.throttling;
 import com.iluwatar.throttling.timer.ThrottleTimerImpl;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -73,14 +74,14 @@ public class App {
   private static void makeServiceCalls(Tenant tenant, CallsCount callsCount) {
     var timer = new ThrottleTimerImpl(10, callsCount);
     var service = new B2BService(timer, callsCount);
-    for (int i = 0; i < 20; i++) {
+    // Sleep is introduced to keep the output in check and easy to view and analyze the results.
+    IntStream.range(0, 20).forEach(i -> {
       service.dummyCustomerApi(tenant);
-      // Sleep is introduced to keep the output in check and easy to view and analyze the results.
       try {
         Thread.sleep(1);
       } catch (InterruptedException e) {
         LOGGER.error("Thread interrupted: {}", e.getMessage());
       }
-    }
+    });
   }
 }

throttling/src/main/java/com/iluwatar/throttling/CallsCount.java

@@ -73,8 +73,6 @@ public final class CallsCount {
    */
   public void reset() {
     LOGGER.debug("Resetting the map.");
-    for (Entry<String, AtomicLong> e : tenantCallsCount.entrySet()) {
-      tenantCallsCount.put(e.getKey(), new AtomicLong(0));
-    }
+    tenantCallsCount.replaceAll((k, v) -> new AtomicLong(0));
   }
 }

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

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

throttling/src/test/java/com/iluwatar/throttling/B2BServiceTest.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.throttling;
 
-import com.iluwatar.throttling.timer.Throttler;
-import org.junit.jupiter.api.Disabled;
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import com.iluwatar.throttling.timer.Throttler;
+import java.util.stream.IntStream;
+import org.junit.jupiter.api.Test;
+
 /**
  * B2BServiceTest class to test the B2BService
  */
@@ -38,15 +38,14 @@ public class B2BServiceTest {
 
   @Test
   public void dummyCustomerApiTest() {
-    Tenant tenant = new Tenant("testTenant", 2, callsCount);
+    var tenant = new Tenant("testTenant", 2, callsCount);
     // In order to assure that throttling limits will not be reset, we use an empty throttling implementation
-    Throttler timer = () -> { };
-    B2BService service = new B2BService(timer, callsCount);
+    var timer = (Throttler) () -> {
+    };
+    var service = new B2BService(timer, callsCount);
 
-    for (int i = 0; i < 5; i++) {
-      service.dummyCustomerApi(tenant);
-    }
-    long counter = callsCount.getCount(tenant.getName());
+    IntStream.range(0, 5).mapToObj(i -> tenant).forEach(service::dummyCustomerApi);
+    var counter = callsCount.getCount(tenant.getName());
     assertEquals(2, counter, "Counter limit must be reached");
   }
 }

throttling/src/test/java/com/iluwatar/throttling/TenantTest.java

@@ -23,11 +23,10 @@
 
 package com.iluwatar.throttling;
 
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.security.InvalidParameterException;
-
-import static org.junit.jupiter.api.Assertions.assertThrows;
+import org.junit.jupiter.api.Test;
 
 /**
  * TenantTest to test the creation of Tenant with valid parameters.
@@ -37,7 +36,7 @@ public class TenantTest {
   @Test
   public void constructorTest() {
     assertThrows(InvalidParameterException.class, () -> {
-      Tenant tenant = new Tenant("FailTenant", -1, new CallsCount());
+      new Tenant("FailTenant", -1, new CallsCount());
     });
   }
 }

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

@@ -24,10 +24,7 @@
 package com.iluwatar.tls;
 
 import java.util.Calendar;
-import java.util.Date;
-import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -71,20 +68,20 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    int counterDateValues = 0;
-    int counterExceptions = 0;
+    var counterDateValues = 0;
+    var counterExceptions = 0;
 
     // Create a callable
-    DateFormatCallable callableDf = new DateFormatCallable("dd/MM/yyyy", "15/12/2015");
+    var callableDf = new DateFormatCallable("dd/MM/yyyy", "15/12/2015");
     // start 4 threads, each using the same Callable instance
-    ExecutorService executor = Executors.newCachedThreadPool();
+    var executor = Executors.newCachedThreadPool();
 
-    Future<Result> futureResult1 = executor.submit(callableDf);
-    Future<Result> futureResult2 = executor.submit(callableDf);
-    Future<Result> futureResult3 = executor.submit(callableDf);
-    Future<Result> futureResult4 = executor.submit(callableDf);
+    var futureResult1 = executor.submit(callableDf);
+    var futureResult2 = executor.submit(callableDf);
+    var futureResult3 = executor.submit(callableDf);
+    var futureResult4 = executor.submit(callableDf);
     try {
-      Result[] result = new Result[4];
+      var result = new Result[4];
       result[0] = futureResult1.get();
       result[1] = futureResult2.get();
       result[2] = futureResult3.get();
@@ -92,9 +89,9 @@ public class App {
 
       // Print results of thread executions (converted dates and raised exceptions)
       // and count them
-      for (int i = 0; i < result.length; i++) {
-        counterDateValues = counterDateValues + printAndCountDates(result[i]);
-        counterExceptions = counterExceptions + printAndCountExceptions(result[i]);
+      for (var value : result) {
+        counterDateValues = counterDateValues + printAndCountDates(value);
+        counterExceptions = counterExceptions + printAndCountExceptions(value);
       }
 
       // a correct run should deliver 20 times 15.12.2015
@@ -115,15 +112,16 @@ public class App {
    */
   private static int printAndCountDates(Result res) {
     // a correct run should deliver 5 times 15.12.2015 per each thread
-    int counter = 0;
-    for (Date dt : res.getDateList()) {
+    var counter = 0;
+    for (var dt : res.getDateList()) {
       counter++;
-      Calendar cal = Calendar.getInstance();
+      var cal = Calendar.getInstance();
       cal.setTime(dt);
       // Formatted output of the date value: DD.MM.YYYY
-      LOGGER.info(
-          cal.get(Calendar.DAY_OF_MONTH) + "." + cal.get(Calendar.MONTH) + "." + +cal
-              .get(Calendar.YEAR));
+      LOGGER.info(cal.get(Calendar.DAY_OF_MONTH) + "."
+          + cal.get(Calendar.MONTH) + "."
+          + cal.get(Calendar.YEAR)
+      );
     }
     return counter;
   }
@@ -136,8 +134,8 @@ public class App {
    */
   private static int printAndCountExceptions(Result res) {
     // a correct run shouldn't deliver any exception
-    int counter = 0;
-    for (String ex : res.getExceptionList()) {
+    var counter = 0;
+    for (var ex : res.getExceptionList()) {
       counter++;
       LOGGER.info(ex);
     }

tls/src/main/java/com/iluwatar/tls/DateFormatCallable.java

@@ -26,6 +26,7 @@ package com.iluwatar.tls;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.concurrent.Callable;
+import java.util.stream.IntStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -58,13 +59,10 @@ public class DateFormatCallable implements Callable<Result> {
    * @param inDateValue  string date value, e.g. "21/06/2016"
    */
   public DateFormatCallable(String inDateFormat, String inDateValue) {
-    final String idf = inDateFormat;                 //TLTL
-    this.df = new ThreadLocal<DateFormat>() {        //TLTL
-      @Override                                      //TLTL
-      protected DateFormat initialValue() {          //TLTL
-        return new SimpleDateFormat(idf);            //TLTL
-      }                                              //TLTL
-    };                                               //TLTL
+    final var idf = inDateFormat;                 //TLTL
+    this.df = ThreadLocal.withInitial(() -> {          //TLTL
+      return new SimpleDateFormat(idf);            //TLTL
+    });                                               //TLTL
     // this.df = new SimpleDateFormat(inDateFormat);    //NTLNTL
     this.dateValue = inDateValue;
   }
@@ -72,10 +70,10 @@ public class DateFormatCallable implements Callable<Result> {
   @Override
   public Result call() {
     LOGGER.info(Thread.currentThread() + " started executing...");
-    Result result = new Result();
+    var result = new Result();
 
     // Convert date value to date 5 times
-    for (int i = 1; i <= 5; i++) {
+    IntStream.rangeClosed(1, 5).forEach(i -> {
       try {
         // this is the statement where it is important to have the
         // instance of SimpleDateFormat locally
@@ -86,8 +84,7 @@ public class DateFormatCallable implements Callable<Result> {
         // write the Exception to a list and continue work
         result.getExceptionList().add(e.getClass() + ": " + e.getMessage());
       }
-
-    }
+    });
 
     LOGGER.info(Thread.currentThread() + " finished processing part of the thread");
 

tls/src/main/java/com/iluwatar/tls/Result.java

@@ -39,11 +39,11 @@ import java.util.List;
  */
 public class Result {
   // A list to collect the date values created in one thread
-  private List<Date> dateList = new ArrayList<Date>();
+  private List<Date> dateList = new ArrayList<>();
 
   // A list to collect Exceptions thrown in one threads (should be none in
   // this example)
-  private List<String> exceptionList = new ArrayList<String>();
+  private List<String> exceptionList = new ArrayList<>();
 
   /**
    * Get list of date values collected within a thread execution.

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

@@ -27,14 +27,12 @@ import org.junit.jupiter.api.Test;
 
 /**
  * Tests that thread local storage example runs without errors.
- * 
- * @author Thomas Bauer, January 2017
  *
+ * @author Thomas Bauer, January 2017
  */
 public class AppTest {
   @Test
-  public void test() throws Exception {
-    String[] args = {};
-    App.main(args);
+  public void test() {
+    App.main(new String[]{});
   }
 }

tls/src/test/java/com/iluwatar/tls/DateFormatCallableTest.java

@@ -23,65 +23,62 @@
 
 package com.iluwatar.tls;
 
-import org.junit.jupiter.api.BeforeAll;
-import org.junit.jupiter.api.Test;
-
-import java.util.ArrayList;
-import java.util.Calendar;
-import java.util.Date;
-import java.util.List;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.fail;
 
+import java.util.ArrayList;
+import java.util.Calendar;
+import java.util.List;
+import java.util.concurrent.Executors;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
 /**
- * 
  * Test of the Callable
- * 
- * In this test {@link DateFormatCallable} is tested with only one thread (i.e. without concurrency situation)
  * <p>
- * After a successful run 5 date values should be in the result object. All dates should have
- * the same value (15.11.2015). To avoid problems with time zone not the date instances themselves
- * are compared by the test. For the test the dates are converted into string format DD.MM.YYY
+ * In this test {@link DateFormatCallable} is tested with only one thread (i.e. without concurrency
+ * situation)
  * <p>
- * Additionally the number of list entries are tested for both the list with the date values
- * and the list with the exceptions 
- * 
- * @author Thomas Bauer, January 2017
+ * After a successful run 5 date values should be in the result object. All dates should have the
+ * same value (15.11.2015). To avoid problems with time zone not the date instances themselves are
+ * compared by the test. For the test the dates are converted into string format DD.MM.YYY
+ * <p>
+ * Additionally the number of list entries are tested for both the list with the date values and the
+ * list with the exceptions
  *
+ * @author Thomas Bauer, January 2017
  */
 public class DateFormatCallableTest {
 
   // Class variables used in setup() have to be static because setup() has to be static
   /**
-   * Result object given back by DateFormatCallable
-   *   -- Array with converted date values
-   *   -- Array with thrown exceptions
+   * Result object given back by DateFormatCallable -- Array with converted date values -- Array
+   * with thrown exceptions
    */
-  static Result result;
+  private static Result result;
 
   /**
-   * The date values created by the run of of DateFormatRunnalbe. List will be filled in the setup() method
+   * The date values created by the run of of DateFormatRunnalbe. List will be filled in the setup()
+   * method
    */
-  static List<String> createdDateValues = new ArrayList<String>();
+  private static List<String> createdDateValues = new ArrayList<>();
 
   /**
    * Expected number of date values in the date value list created by the run of DateFormatRunnalbe
    */
-  int expectedCounterDateValues = 5;
+  private int expectedCounterDateValues = 5;
 
   /**
-   * Expected number of exceptions in the exception list created by the run of DateFormatRunnalbe. 
+   * Expected number of exceptions in the exception list created by the run of DateFormatRunnalbe.
    */
-  int expectedCounterExceptions = 0;
+  private int expectedCounterExceptions = 0;
 
   /**
-   * Expected content of the list containing the date values created by the run of DateFormatRunnalbe
+   * Expected content of the list containing the date values created by the run of
+   * DateFormatRunnalbe
    */
-  List<String> expectedDateValues = List.of("15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015");
+  private List<String> expectedDateValues =
+      List.of("15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015");
 
   /**
    * Run Callable and prepare results for usage in the test methods
@@ -89,10 +86,10 @@ public class DateFormatCallableTest {
   @BeforeAll
   public static void setup() {
     // Create a callable
-    DateFormatCallable callableDf = new DateFormatCallable("dd/MM/yyyy", "15/12/2015");
+    var callableDf = new DateFormatCallable("dd/MM/yyyy", "15/12/2015");
     // start thread using the Callable instance
-    ExecutorService executor = Executors.newCachedThreadPool();
-    Future<Result> futureResult = executor.submit(callableDf);
+    var executor = Executors.newCachedThreadPool();
+    var futureResult = executor.submit(callableDf);
     try {
       result = futureResult.get();
       createdDateValues = convertDatesToString(result);
@@ -107,18 +104,22 @@ public class DateFormatCallableTest {
     if (res == null || res.getDateList() == null || res.getDateList().size() == 0) {
       return null;
     }
-    List<String> returnList = new ArrayList<String>();
+    var returnList = new ArrayList<String>();
 
-    for (Date dt : res.getDateList()) {
-      Calendar cal = Calendar.getInstance();
+    for (var dt : res.getDateList()) {
+      var cal = Calendar.getInstance();
       cal.setTime(dt);
-      returnList.add(cal.get(Calendar.DAY_OF_MONTH) + "." + cal.get(Calendar.MONTH) + "." + cal.get(Calendar.YEAR));
+      returnList.add(cal.get(Calendar.DAY_OF_MONTH) + "."
+          + cal.get(Calendar.MONTH) + "."
+          + cal.get(Calendar.YEAR)
+      );
     }
     return returnList;
   }
 
   /**
-   * Test date values after the run of DateFormatRunnalbe. A correct run should deliver 5 times 15.12.2015
+   * Test date values after the run of DateFormatRunnalbe. A correct run should deliver 5 times
+   * 15.12.2015
    */
   @Test
   public void testDateValues() {
@@ -126,7 +127,8 @@ public class DateFormatCallableTest {
   }
 
   /**
-   * Test number of dates in the list after the run of DateFormatRunnalbe. A correct run should deliver 5 date values
+   * Test number of dates in the list after the run of DateFormatRunnalbe. A correct run should
+   * deliver 5 date values
    */
   @Test
   public void testCounterDateValues() {
@@ -134,8 +136,8 @@ public class DateFormatCallableTest {
   }
 
   /**
-   * Test number of Exceptions in the list after the run of DateFormatRunnalbe. A correct run should deliver 
-   * no exceptions
+   * Test number of Exceptions in the list after the run of DateFormatRunnalbe. A correct run should
+   * deliver no exceptions
    */
   @Test
   public void testCounterExceptions() {

tls/src/test/java/com/iluwatar/tls/DateFormatCallableTestIncorrectDateFormat.java

@@ -23,63 +23,55 @@
 
 package com.iluwatar.tls;
 
-import org.junit.jupiter.api.BeforeAll;
-import org.junit.jupiter.api.Test;
-
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.fail;
 
+import java.util.List;
+import java.util.concurrent.Executors;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
 /**
- * 
  * Test of the Callable
- * 
- * In this test {@link DateFormatCallable} is tested with only one thread (i.e. without concurrency situation)
  * <p>
- * An incorrect formatted date is passed to the Callable
- * After a successful run 0 date values and 5 exceptions should be in the result object. 
- * 
- * @author Thomas Bauer, January 2017
+ * In this test {@link DateFormatCallable} is tested with only one thread (i.e. without concurrency
+ * situation)
+ * <p>
+ * An incorrect formatted date is passed to the Callable After a successful run 0 date values and 5
+ * exceptions should be in the result object.
  *
+ * @author Thomas Bauer, January 2017
  */
 public class DateFormatCallableTestIncorrectDateFormat {
 
   // Class variables used in setup() have to be static because setup() has to be static
   /**
-   * Result object given back by DateFormatCallable
-   *   -- Array with converted date values
-   *   -- Array with thrown exceptions
+   * Result object given back by DateFormatCallable -- Array with converted date values -- Array
+   * with thrown exceptions
    */
-  static Result result;
-
-  /**
-   * The date values created by the run of DateFormatRunnalbe. List will be filled in the setup() method
-   */
-  static List<String> createdExceptions = new ArrayList<String>();
+  private static Result result;
 
   /**
    * Expected number of date values in the date value list created by the run of DateFormatRunnalbe
    */
-  int expectedCounterDateValues = 0;
+  private int expectedCounterDateValues = 0;
 
   /**
-   * Expected number of exceptions in the exception list created by the run of DateFormatRunnalbe. 
+   * Expected number of exceptions in the exception list created by the run of DateFormatRunnalbe.
    */
-  int expectedCounterExceptions = 5;
+  private int expectedCounterExceptions = 5;
 
   /**
-   * Expected content of the list containing the exceptions created by the run of DateFormatRunnalbe
+   * Expected content of the list containing the exceptions created by the run of
+   * DateFormatRunnalbe
    */
-  List<String> expectedExceptions = List.of("class java.text.ParseException: Unparseable date: \"15.12.2015\"",
+  private List<String> expectedExceptions = List.of(
       "class java.text.ParseException: Unparseable date: \"15.12.2015\"",
       "class java.text.ParseException: Unparseable date: \"15.12.2015\"",
       "class java.text.ParseException: Unparseable date: \"15.12.2015\"",
-      "class java.text.ParseException: Unparseable date: \"15.12.2015\"");
+      "class java.text.ParseException: Unparseable date: \"15.12.2015\"",
+      "class java.text.ParseException: Unparseable date: \"15.12.2015\""
+  );
 
   /**
    * Run Callable and prepare results for usage in the test methods
@@ -87,10 +79,10 @@ public class DateFormatCallableTestIncorrectDateFormat {
   @BeforeAll
   public static void setup() {
     // Create a callable. Pass a string date value not matching the format string
-    DateFormatCallable callableDf = new DateFormatCallable("dd/MM/yyyy", "15.12.2015");
+    var callableDf = new DateFormatCallable("dd/MM/yyyy", "15.12.2015");
     // start thread using the Callable instance
-    ExecutorService executor = Executors.newCachedThreadPool();
-    Future<Result> futureResult = executor.submit(callableDf);
+    var executor = Executors.newCachedThreadPool();
+    var futureResult = executor.submit(callableDf);
     try {
       result = futureResult.get();
     } catch (Exception e) {
@@ -109,7 +101,8 @@ public class DateFormatCallableTestIncorrectDateFormat {
   }
 
   /**
-   * Test number of dates in the list after the run of DateFormatRunnalbe. A correct run should deliver no date values
+   * Test number of dates in the list after the run of DateFormatRunnalbe. A correct run should
+   * deliver no date values
    */
   @Test
   public void testCounterDateValues() {
@@ -117,7 +110,7 @@ public class DateFormatCallableTestIncorrectDateFormat {
   }
 
   /**
-   * Test number of Exceptions in the list after the run of DateFormatRunnalbe. A correct run should 
+   * Test number of Exceptions in the list after the run of DateFormatRunnalbe. A correct run should
    * deliver 5 exceptions
    */
   @Test

tls/src/test/java/com/iluwatar/tls/DateFormatCallableTestMultiThread.java

@@ -23,69 +23,66 @@
 
 package com.iluwatar.tls;
 
-import org.junit.jupiter.api.BeforeAll;
-import org.junit.jupiter.api.Test;
-
-import java.util.ArrayList;
-import java.util.Calendar;
-import java.util.Date;
-import java.util.List;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.fail;
 
+import java.util.ArrayList;
+import java.util.Calendar;
+import java.util.List;
+import java.util.concurrent.Executors;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
 /**
- * 
  * Test of the Callable
- * 
+ * <p>
  * In this test {@link DateFormatCallable} is used by 4 threads in parallel
  * <p>
- * After a successful run 5 date values should be in the result object of each thread. All dates 
+ * After a successful run 5 date values should be in the result object of each thread. All dates
  * should have the same value (15.11.2015). To avoid problems with time zone not the date instances
- * themselves are compared by the test. For the test the dates are converted into string format DD.MM.YYY
+ * themselves are compared by the test. For the test the dates are converted into string format
+ * DD.MM.YYY
  * <p>
- * Additionally the number of list entries are tested for both the list with the date values
- * and the list with the exceptions 
- * 
- * @author Thomas Bauer, January 2017
+ * Additionally the number of list entries are tested for both the list with the date values and the
+ * list with the exceptions
  *
+ * @author Thomas Bauer, January 2017
  */
 public class DateFormatCallableTestMultiThread {
 
   // Class variables used in setup() have to be static because setup() has to be static
   /**
-   * Result object given back by DateFormatCallable, one for each thread
-   *   -- Array with converted date values
-   *   -- Array with thrown exceptions
+   * Result object given back by DateFormatCallable, one for each thread -- Array with converted
+   * date values -- Array with thrown exceptions
    */
-  static Result[] result = new Result[4];
+  private static Result[] result = new Result[4];
 
   /**
-   * The date values created by the run of of DateFormatRunnalbe. List will be filled in the setup() method
+   * The date values created by the run of of DateFormatRunnalbe. List will be filled in the setup()
+   * method
    */
   @SuppressWarnings("serial")
-  static class StringArrayList extends ArrayList<String> {
+  private static class StringArrayList extends ArrayList<String> {
     /* nothing needed here */
   }
-  static List<String>[] createdDateValues = new StringArrayList[4];
+
+  private static List<String>[] createdDateValues = new StringArrayList[4];
 
   /**
    * Expected number of date values in the date value list created by each thread
    */
-  int expectedCounterDateValues = 5;
+  private int expectedCounterDateValues = 5;
 
   /**
-   * Expected number of exceptions in the exception list created by each thread 
+   * Expected number of exceptions in the exception list created by each thread
    */
-  int expectedCounterExceptions = 0;
+  private int expectedCounterExceptions = 0;
 
   /**
-   * Expected content of the list containing the date values created by each thread 
+   * Expected content of the list containing the date values created by each thread
    */
-  List<String> expectedDateValues = List.of("15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015");
+  private List<String> expectedDateValues =
+      List.of("15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015", "15.11.2015");
 
   /**
    * Run Callable and prepare results for usage in the test methods
@@ -93,19 +90,19 @@ public class DateFormatCallableTestMultiThread {
   @BeforeAll
   public static void setup() {
     // Create a callable
-    DateFormatCallable callableDf = new DateFormatCallable("dd/MM/yyyy", "15/12/2015");
+    var callableDf = new DateFormatCallable("dd/MM/yyyy", "15/12/2015");
     // start thread using the Callable instance
-    ExecutorService executor = Executors.newCachedThreadPool();
-    Future<Result> futureResult1 = executor.submit(callableDf);
-    Future<Result> futureResult2 = executor.submit(callableDf);
-    Future<Result> futureResult3 = executor.submit(callableDf);
-    Future<Result> futureResult4 = executor.submit(callableDf);
+    var executor = Executors.newCachedThreadPool();
+    var futureResult1 = executor.submit(callableDf);
+    var futureResult2 = executor.submit(callableDf);
+    var futureResult3 = executor.submit(callableDf);
+    var futureResult4 = executor.submit(callableDf);
     try {
       result[0] = futureResult1.get();
       result[1] = futureResult2.get();
       result[2] = futureResult3.get();
       result[3] = futureResult4.get();
-      for (int i = 0; i < result.length; i++) {
+      for (var i = 0; i < result.length; i++) {
         createdDateValues[i] = convertDatesToString(result[i]);
       }
     } catch (Exception e) {
@@ -119,46 +116,49 @@ public class DateFormatCallableTestMultiThread {
     if (res == null || res.getDateList() == null || res.getDateList().size() == 0) {
       return null;
     }
-    List<String> returnList = new StringArrayList();
+    var returnList = new StringArrayList();
 
-    for (Date dt : res.getDateList()) {
-      Calendar cal = Calendar.getInstance();
+    for (var dt : res.getDateList()) {
+      var cal = Calendar.getInstance();
       cal.setTime(dt);
-      returnList.add(cal.get(Calendar.DAY_OF_MONTH) + "." + cal.get(Calendar.MONTH) + "." + cal.get(Calendar.YEAR));
+      returnList.add(cal.get(Calendar.DAY_OF_MONTH) + "."
+          + cal.get(Calendar.MONTH) + "."
+          + cal.get(Calendar.YEAR)
+      );
     }
     return returnList;
   }
 
   /**
-   * Test date values after the run of DateFormatRunnalbe. A correct run should deliver 5 times 15.12.2015
-   * by each thread
+   * Test date values after the run of DateFormatRunnalbe. A correct run should deliver 5 times
+   * 15.12.2015 by each thread
    */
   @Test
   public void testDateValues() {
-    for (int i = 0; i < createdDateValues.length; i++) {
-      assertEquals(expectedDateValues, createdDateValues[i]);
+    for (var createdDateValue : createdDateValues) {
+      assertEquals(expectedDateValues, createdDateValue);
     }
   }
 
   /**
-   * Test number of dates in the list after the run of DateFormatRunnalbe. A correct run should 
+   * Test number of dates in the list after the run of DateFormatRunnalbe. A correct run should
    * deliver 5 date values by each thread
    */
   @Test
   public void testCounterDateValues() {
-    for (int i = 0; i < result.length; i++) {
-      assertEquals(expectedCounterDateValues, result[i].getDateList().size());
+    for (var value : result) {
+      assertEquals(expectedCounterDateValues, value.getDateList().size());
     }
   }
 
   /**
-   * Test number of Exceptions in the list after the run of DateFormatRunnalbe. A correct run should 
+   * Test number of Exceptions in the list after the run of DateFormatRunnalbe. A correct run should
    * deliver no exceptions
    */
   @Test
   public void testCounterExceptions() {
-    for (int i = 0; i < result.length; i++) {
-      assertEquals(expectedCounterExceptions, result[i].getExceptionList().size());
+    for (var value : result) {
+      assertEquals(expectedCounterExceptions, value.getExceptionList().size());
     }
   }
 }

tolerant-reader/src/main/java/com/iluwatar/tolerantreader/RainbowFishSerializer.java

@@ -82,15 +82,18 @@ public final class RainbowFishSerializer {
    * Read V1 RainbowFish from file.
    */
   public static RainbowFish readV1(String filename) throws IOException, ClassNotFoundException {
-    Map<String, String> map = null;
+    Map<String, String> map;
 
     try (var fileIn = new FileInputStream(filename);
          var objIn = new ObjectInputStream(fileIn)) {
       map = (Map<String, String>) objIn.readObject();
     }
 
-    return new RainbowFish(map.get("name"), Integer.parseInt(map.get("age")), Integer
-        .parseInt(map.get("lengthMeters")),
-        Integer.parseInt(map.get("weightTons")));
+    return new RainbowFish(
+        map.get("name"),
+        Integer.parseInt(map.get("age")),
+        Integer.parseInt(map.get("lengthMeters")),
+        Integer.parseInt(map.get("weightTons"))
+    );
   }
 }

tolerant-reader/src/test/java/com/iluwatar/tolerantreader/AppTest.java

@@ -23,32 +23,28 @@
 
 package com.iluwatar.tolerantreader;
 
+import java.io.File;
+import java.io.IOException;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import java.io.File;
-import java.io.IOException;
-
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() throws ClassNotFoundException, IOException {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 
   @BeforeEach
   @AfterEach
   public void cleanup() {
-    File file1 = new File("fish1.out");
+    var file1 = new File("fish1.out");
     file1.delete();
-    File file2 = new File("fish2.out");
+    var file2 = new File("fish2.out");
     file2.delete();
   }
 }

tolerant-reader/src/test/java/com/iluwatar/tolerantreader/RainbowFishSerializerTest.java

@@ -23,16 +23,15 @@
 
 package com.iluwatar.tolerantreader;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+
+import java.io.File;
 import org.junit.Rule;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.migrationsupport.rules.EnableRuleMigrationSupport;
 import org.junit.rules.TemporaryFolder;
 
-import java.io.File;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotSame;
-
 /**
  * Date: 12/30/15 - 18:39 PM
  *
@@ -62,10 +61,10 @@ public class RainbowFishSerializerTest {
    */
   @Test
   public void testWriteV1ReadV1() throws Exception {
-    final File outputFile = this.testFolder.newFile();
+    final var outputFile = this.testFolder.newFile();
     RainbowFishSerializer.writeV1(V1, outputFile.getPath());
 
-    final RainbowFish fish = RainbowFishSerializer.readV1(outputFile.getPath());
+    final var fish = RainbowFishSerializer.readV1(outputFile.getPath());
     assertNotSame(V1, fish);
     assertEquals(V1.getName(), fish.getName());
     assertEquals(V1.getAge(), fish.getAge());
@@ -79,10 +78,10 @@ public class RainbowFishSerializerTest {
    */
   @Test
   public void testWriteV2ReadV1() throws Exception {
-    final File outputFile = this.testFolder.newFile();
+    final var outputFile = this.testFolder.newFile();
     RainbowFishSerializer.writeV2(V2, outputFile.getPath());
 
-    final RainbowFish fish = RainbowFishSerializer.readV1(outputFile.getPath());
+    final var fish = RainbowFishSerializer.readV1(outputFile.getPath());
     assertNotSame(V2, fish);
     assertEquals(V2.getName(), fish.getName());
     assertEquals(V2.getAge(), fish.getAge());

tolerant-reader/src/test/java/com/iluwatar/tolerantreader/RainbowFishTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.tolerantreader;
 
-import org.junit.Test;
-
 import static org.junit.Assert.assertEquals;
 
+import org.junit.Test;
+
 /**
  * Date: 12/30/15 - 18:34 PM
  *
@@ -39,7 +39,7 @@ public class RainbowFishTest {
    */
   @Test
   public void testValues() {
-    final RainbowFish fish = new RainbowFish("name", 1, 2, 3);
+    final var fish = new RainbowFish("name", 1, 2, 3);
     assertEquals("name", fish.getName());
     assertEquals(1, fish.getAge());
     assertEquals(2, fish.getLengthMeters());

tolerant-reader/src/test/java/com/iluwatar/tolerantreader/RainbowFishV2Test.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.tolerantreader;
 
-import org.junit.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.Test;
+
 /**
  * Date: 12/30/15 - 18:35 PM
  *
@@ -41,7 +41,7 @@ public class RainbowFishV2Test {
    */
   @Test
   public void testValues() {
-    final RainbowFishV2 fish = new RainbowFishV2("name", 1, 2, 3, false, true, false);
+    final var fish = new RainbowFishV2("name", 1, 2, 3, false, true, false);
     assertEquals("name", fish.getName());
     assertEquals(1, fish.getAge());
     assertEquals(2, fish.getLengthMeters());

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

@@ -99,13 +99,11 @@ public interface Trampoline<T> {
       }
 
       T trampoline(final Trampoline<T> trampoline) {
-
         return Stream.iterate(trampoline, Trampoline::jump)
             .filter(Trampoline::complete)
             .findFirst()
-            .get()
-            .result();
-
+            .map(Trampoline::result)
+            .orElseThrow();
       }
     };
   }

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

@@ -40,7 +40,7 @@ public class TrampolineApp {
    */
   public static void main(String[] args) {
     log.info("start pattern");
-    Integer result = loop(10, 1).result();
+    var result = loop(10, 1).result();
     log.info("result {}", result);
 
   }

trampoline/src/test/java/com/iluwatar/trampoline/TrampolineAppTest.java

@@ -23,22 +23,20 @@
 
 package com.iluwatar.trampoline;
 
+import static org.junit.Assert.assertEquals;
+
 import org.junit.Test;
 
-import java.io.IOException;
-
-import static org.junit.Assert.*;
-
 
 /**
  * Test for trampoline pattern.
- * */
+ */
 public class TrampolineAppTest {
 
 
   @Test
   public void testTrampolineWithFactorialFunction() {
-    int result = TrampolineApp.loop(10, 1).result();
+    long result = TrampolineApp.loop(10, 1).result();
     assertEquals("Be equal", 3628800, result);
   }
 

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

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

twin/src/test/java/com/iluwatar/twin/BallItemTest.java

@@ -34,11 +34,10 @@ import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.AppenderBase;
 import java.util.LinkedList;
 import java.util.List;
-
+import java.util.stream.IntStream;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.mockito.InOrder;
 import org.slf4j.LoggerFactory;
 
 /**
@@ -62,27 +61,26 @@ public class BallItemTest {
 
   @Test
   public void testClick() {
-    final BallThread ballThread = mock(BallThread.class);
-    final BallItem ballItem = new BallItem();
+    final var ballThread = mock(BallThread.class);
+    final var ballItem = new BallItem();
     ballItem.setTwin(ballThread);
 
-    final InOrder inOrder = inOrder(ballThread);
+    final var inOrder = inOrder(ballThread);
 
-    for (int i = 0; i < 10; i++) {
+    IntStream.range(0, 10).forEach(i -> {
       ballItem.click();
       inOrder.verify(ballThread).suspendMe();
-
       ballItem.click();
       inOrder.verify(ballThread).resumeMe();
-    }
+    });
 
     inOrder.verifyNoMoreInteractions();
   }
 
   @Test
   public void testDoDraw() {
-    final BallItem ballItem = new BallItem();
-    final BallThread ballThread = mock(BallThread.class);
+    final var ballItem = new BallItem();
+    final var ballThread = mock(BallThread.class);
     ballItem.setTwin(ballThread);
 
     ballItem.draw();
@@ -95,8 +93,8 @@ public class BallItemTest {
 
   @Test
   public void testMove() {
-    final BallItem ballItem = new BallItem();
-    final BallThread ballThread = mock(BallThread.class);
+    final var ballItem = new BallItem();
+    final var ballThread = mock(BallThread.class);
     ballItem.setTwin(ballThread);
 
     ballItem.move();

twin/src/test/java/com/iluwatar/twin/BallThreadTest.java

@@ -23,15 +23,19 @@
 
 package com.iluwatar.twin;
 
-import org.junit.jupiter.api.Test;
-
 import static java.lang.Thread.UncaughtExceptionHandler;
 import static java.lang.Thread.sleep;
 import static java.time.Duration.ofMillis;
 import static org.junit.jupiter.api.Assertions.assertTimeout;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.eq;
-import static org.mockito.Mockito.*;
+import static org.mockito.Mockito.atLeastOnce;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.verifyZeroInteractions;
+
+import org.junit.jupiter.api.Test;
 
 /**
  * Date: 12/30/15 - 18:55 PM
@@ -44,11 +48,11 @@ public class BallThreadTest {
    * Verify if the {@link BallThread} can be resumed
    */
   @Test
-  public void testSuspend() throws Exception {
+  public void testSuspend() {
     assertTimeout(ofMillis(5000), () -> {
-      final BallThread ballThread = new BallThread();
+      final var ballThread = new BallThread();
 
-      final BallItem ballItem = mock(BallItem.class);
+      final var ballItem = mock(BallItem.class);
       ballThread.setTwin(ballItem);
 
       ballThread.start();
@@ -72,9 +76,9 @@ public class BallThreadTest {
   @Test
   public void testResume() {
     assertTimeout(ofMillis(5000), () -> {
-      final BallThread ballThread = new BallThread();
+      final var ballThread = new BallThread();
 
-      final BallItem ballItem = mock(BallItem.class);
+      final var ballItem = mock(BallItem.class);
       ballThread.setTwin(ballItem);
 
       ballThread.suspendMe();
@@ -102,8 +106,8 @@ public class BallThreadTest {
   @Test
   public void testInterrupt() {
     assertTimeout(ofMillis(5000), () -> {
-      final BallThread ballThread = new BallThread();
-      final UncaughtExceptionHandler exceptionHandler = mock(UncaughtExceptionHandler.class);
+      final var ballThread = new BallThread();
+      final var exceptionHandler = mock(UncaughtExceptionHandler.class);
       ballThread.setUncaughtExceptionHandler(exceptionHandler);
       ballThread.setTwin(mock(BallItem.class));
       ballThread.start();

typeobjectpattern/src/main/java/com/iluwatar/typeobject/CandyGame.java

@@ -25,6 +25,7 @@ package com.iluwatar.typeobject;
 
 import com.iluwatar.typeobject.Candy.Type;
 import java.util.ArrayList;
+import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -55,21 +56,17 @@ public class CandyGame {
   }
 
   static String numOfSpaces(int num) {
-    String result = "";
-    for (var i = 0; i < num; i++) {
-      result += " ";
-    }
-    return result;
+    return " ".repeat(Math.max(0, num));
   }
 
   void printGameStatus() {
     LOGGER.info("");
-    for (var i = 0; i < cells.length; i++) {
+    for (Cell[] cell : cells) {
       for (var j = 0; j < cells.length; j++) {
-        var candyName = cells[i][j].candy.name;
+        var candyName = cell[j].candy.name;
         if (candyName.length() < 20) {
           var totalSpaces = 20 - candyName.length();
-          LOGGER.info(numOfSpaces(totalSpaces / 2) + cells[i][j].candy.name
+          LOGGER.info(numOfSpaces(totalSpaces / 2) + cell[j].candy.name
               + numOfSpaces(totalSpaces - totalSpaces / 2) + "|");
         } else {
           LOGGER.info(candyName + "|");
@@ -80,8 +77,8 @@ public class CandyGame {
     LOGGER.info("");
   }
 
-  ArrayList<Cell> adjacentCells(int y, int x) {
-    ArrayList<Cell> adjacent = new ArrayList<Cell>();
+  List<Cell> adjacentCells(int y, int x) {
+    var adjacent = new ArrayList<Cell>();
     if (y == 0) {
       adjacent.add(this.cells[1][x]);
     }
@@ -115,8 +112,8 @@ public class CandyGame {
       for (var j = 0; j < this.cells.length; j++) {
         if (!this.cells[i][j].candy.getType().equals(Type.rewardFruit)) {
           var adj = adjacentCells(i, j);
-          for (var a = 0; a < adj.size(); a++) {
-            if (this.cells[i][j].candy.name.equals(adj.get(a).candy.name)) {
+          for (Cell cell : adj) {
+            if (this.cells[i][j].candy.name.equals(cell.candy.name)) {
               return true;
             }
           }
@@ -157,11 +154,11 @@ public class CandyGame {
           }
         }
       }
-      for (var i = 0; i < this.cells.length; i++) {
+      for (Cell[] cell : this.cells) {
         var j = 0;
         var points = 0;
         while (j < cells.length - 1) {
-          points = this.cells[i][j].interact(this.cells[i][j + 1], this.pool, this.cells);
+          points = cell[j].interact(cell[j + 1], this.pool, this.cells);
           if (points != 0) {
             handleChange(points);
           } else {

typeobjectpattern/src/main/java/com/iluwatar/typeobject/CellPool.java

@@ -27,6 +27,7 @@ import com.iluwatar.typeobject.Candy.Type;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.List;
 import java.util.Random;
 import org.json.simple.parser.ParseException;
 
@@ -38,12 +39,12 @@ import org.json.simple.parser.ParseException;
 
 public class CellPool {
   private static final Random RANDOM = new Random();
-  ArrayList<Cell> pool;
+  List<Cell> pool;
   int pointer;
   Candy[] randomCode;
 
   CellPool(int num) {
-    this.pool = new ArrayList<Cell>(num);
+    this.pool = new ArrayList<>(num);
     try {
       this.randomCode = assignRandomCandytypes();
     } catch (Exception e) {

typeobjectpattern/src/main/java/com/iluwatar/typeobject/JsonParser.java

@@ -25,11 +25,11 @@ package com.iluwatar.typeobject;
 
 import com.iluwatar.typeobject.Candy.Type;
 import java.io.File;
-import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
-import java.util.Enumeration;
 import java.util.Hashtable;
+import java.util.List;
+import java.util.stream.Collectors;
 import org.json.simple.JSONArray;
 import org.json.simple.JSONObject;
 import org.json.simple.parser.JSONParser;
@@ -43,24 +43,24 @@ public class JsonParser {
   Hashtable<String, Candy> candies;
 
   JsonParser() {
-    this.candies = new Hashtable<String, Candy>();
+    this.candies = new Hashtable<>();
   }
 
-  void parse() throws FileNotFoundException, IOException, ParseException {
+  void parse() throws IOException, ParseException {
     var parser = new JSONParser();
-    var jo = (JSONObject) parser.parse(new FileReader(new File("").getAbsolutePath()
-        + "\\src\\main\\java\\com\\iluwatar\\typeobject\\candy.json"));
+    var workingDirectory = new File("").getAbsolutePath();
+    var filePath = List.of("src", "main", "java", "com", "iluwatar", "typeobject", "candy.json");
+    var absolutePath = workingDirectory + File.separator + String.join(File.separator, filePath);
+    var jo = (JSONObject) parser.parse(new FileReader(absolutePath));
     var a = (JSONArray) jo.get("candies");
     for (var o : a) {
       var candy = (JSONObject) o;
       var name = (String) candy.get("name");
       var parentName = (String) candy.get("parent");
       var t = (String) candy.get("type");
-      Type type = null;
+      var type = Type.crushableCandy;
       if (t.equals("rewardFruit")) {
         type = Type.rewardFruit;
-      } else {
-        type = Type.crushableCandy;
       }
       var points = Integer.parseInt((String) candy.get("points"));
       var c = new Candy(name, parentName, type, points);
@@ -70,7 +70,7 @@ public class JsonParser {
   }
 
   void setParentAndPoints() {
-    for (Enumeration<String> e = this.candies.keys(); e.hasMoreElements(); ) {
+    for (var e = this.candies.keys(); e.hasMoreElements(); ) {
       var c = this.candies.get(e.nextElement());
       if (c.parentName == null) {
         c.parent = null;

typeobjectpattern/src/test/java/com/iluwatar/typeobject/CandyGameTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.typeobject;
 
-import static org.junit.jupiter.api.Assertions.*;
-import org.junit.jupiter.api.Test;
-import java.util.ArrayList;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import com.iluwatar.typeobject.Candy.Type;
+import org.junit.jupiter.api.Test;
 
 /**
  * The CandyGameTest class tests the methods in the {@link CandyGame} class.
@@ -36,7 +36,7 @@ class CandyGameTest {
 
   @Test
   void adjacentCellsTest() {
-    var cg = new CandyGame(3,new CellPool(9));
+    var cg = new CandyGame(3, new CellPool(9));
     var arr1 = cg.adjacentCells(0, 0);
     var arr2 = cg.adjacentCells(1, 2);
     var arr3 = cg.adjacentCells(1, 1);
@@ -49,19 +49,19 @@ class CandyGameTest {
     var c1 = new Candy("green jelly", "jelly", Type.crushableCandy, 5);
     var c2 = new Candy("purple jelly", "jelly", Type.crushableCandy, 5);
     var c3 = new Candy("green apple", "apple", Type.rewardFruit, 10);
-    matrix[0][0] = new Cell(c1,0,0);;
-    matrix[0][1] = new Cell(c2,1,0);
-    matrix[1][0] = new Cell(c3,0,1);
-    matrix[1][1] = new Cell(c2,1,1);
+    matrix[0][0] = new Cell(c1, 0, 0);
+    matrix[0][1] = new Cell(c2, 1, 0);
+    matrix[1][0] = new Cell(c3, 0, 1);
+    matrix[1][1] = new Cell(c2, 1, 1);
     var p = new CellPool(4);
-    var cg = new CandyGame(2,p);
+    var cg = new CandyGame(2, p);
     cg.cells = matrix;
     var fruitInLastRow = cg.continueRound();
     matrix[1][0].crush(p, matrix);
-    matrix[0][0] = new Cell(c3,0,0);
-    var matchingCandy = cg.continueRound(); 
-    matrix[0][1].crush(p,matrix);
-    matrix[0][1] = new Cell(c3,1,0);
+    matrix[0][0] = new Cell(c3, 0, 0);
+    var matchingCandy = cg.continueRound();
+    matrix[0][1].crush(p, matrix);
+    matrix[0][1] = new Cell(c3, 1, 0);
     var noneLeft = cg.continueRound();
     assertTrue(fruitInLastRow && matchingCandy && !noneLeft);
   }

typeobjectpattern/src/test/java/com/iluwatar/typeobject/CellPoolTest.java

@@ -23,9 +23,10 @@
 
 package com.iluwatar.typeobject;
 
-import static org.junit.jupiter.api.Assertions.*;
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import java.util.Hashtable;
+import org.junit.jupiter.api.Test;
 
 /**
  * The CellPoolTest class tests the methods in the {@link CellPool} class.
@@ -39,9 +40,7 @@ class CellPoolTest {
     var ht = new Hashtable<String, Boolean>();
     var parentTypes = 0;
     for (var i = 0; i < cp.randomCode.length; i++) {
-      if (ht.get(cp.randomCode[i].name) == null) {
-        ht.put(cp.randomCode[i].name, true);
-      }
+      ht.putIfAbsent(cp.randomCode[i].name, true);
       if (cp.randomCode[i].name.equals("fruit") || cp.randomCode[i].name.equals("candy")) {
         parentTypes++;
       }

typeobjectpattern/src/test/java/com/iluwatar/typeobject/CellTest.java

@@ -23,14 +23,15 @@
 
 package com.iluwatar.typeobject;
 
-import static org.junit.jupiter.api.Assertions.*;
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import com.iluwatar.typeobject.Candy.Type;
+import org.junit.jupiter.api.Test;
 
 /**
  * The CellTest class tests the methods in the {@link Cell} class.
  */
-
 class CellTest {
 
   @Test
@@ -38,10 +39,10 @@ class CellTest {
     var c1 = new Candy("green jelly", "jelly", Type.crushableCandy, 5);
     var c2 = new Candy("green apple", "apple", Type.rewardFruit, 10);
     var matrix = new Cell[4][4];
-    matrix[0][0] = new Cell(c1,0,0);
-    matrix[0][1] = new Cell(c1,1,0);
-    matrix[0][2] = new Cell(c2,2,0);
-    matrix[0][3] = new Cell(c1,3,0);
+    matrix[0][0] = new Cell(c1, 0, 0);
+    matrix[0][1] = new Cell(c1, 1, 0);
+    matrix[0][2] = new Cell(c2, 2, 0);
+    matrix[0][3] = new Cell(c1, 3, 0);
     var cp = new CellPool(5);
     var points1 = matrix[0][0].interact(matrix[0][1], cp, matrix);
     var points2 = matrix[0][2].interact(matrix[0][3], cp, matrix);
@@ -53,9 +54,9 @@ class CellTest {
     var c1 = new Candy("green jelly", "jelly", Type.crushableCandy, 5);
     var c2 = new Candy("purple candy", "candy", Type.crushableCandy, 5);
     var matrix = new Cell[4][4];
-    matrix[0][0] = new Cell(c1,0,0);
-    matrix[1][0] = new Cell(c2,0,1);
+    matrix[0][0] = new Cell(c1, 0, 0);
+    matrix[1][0] = new Cell(c2, 0, 1);
     matrix[1][0].crush(new CellPool(5), matrix);
-    assertTrue(matrix[1][0].candy.name.equals("green jelly"));
+    assertEquals("green jelly", matrix[1][0].candy.name);
   }
 }

unit-of-work/src/test/java/com/iluwatar/unitofwork/AppTest.java

@@ -25,15 +25,12 @@ package com.iluwatar.unitofwork;
 
 import org.junit.Test;
 
-import java.io.IOException;
-
 /**
  * AppTest
  */
 public class AppTest {
   @Test
   public void test() {
-    String[] args = {};
-    App.main(args);
+    App.main(new String[]{});
   }
 }

unit-of-work/src/test/java/com/iluwatar/unitofwork/StudentRepositoryTest.java

@@ -23,20 +23,22 @@
 
 package com.iluwatar.unitofwork;
 
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.verifyZeroInteractions;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.runners.MockitoJUnitRunner;
 
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-import static org.junit.Assert.assertEquals;
-import static org.mockito.Mockito.*;
-
 /**
  * tests {@link StudentRepository}
  */
@@ -51,7 +53,7 @@ public class StudentRepositoryTest {
   private StudentRepository studentRepository;
 
   @Before
-  public void setUp() throws Exception {
+  public void setUp() {
     context = new HashMap<>();
     studentRepository = new StudentRepository(context, studentDatabase);
   }
@@ -85,9 +87,9 @@ public class StudentRepositoryTest {
 
   @Test
   public void shouldSaveAllLocalChangesToDb() {
-    context.put(IUnitOfWork.INSERT, Collections.singletonList(student1));
-    context.put(IUnitOfWork.MODIFY, Collections.singletonList(student1));
-    context.put(IUnitOfWork.DELETE, Collections.singletonList(student1));
+    context.put(IUnitOfWork.INSERT, List.of(student1));
+    context.put(IUnitOfWork.MODIFY, List.of(student1));
+    context.put(IUnitOfWork.DELETE, List.of(student1));
 
     studentRepository.commit();
 
@@ -116,8 +118,8 @@ public class StudentRepositoryTest {
 
   @Test
   public void shouldNotInsertToDbIfNoRegisteredStudentsToBeCommitted() {
-    context.put(IUnitOfWork.MODIFY, Collections.singletonList(student1));
-    context.put(IUnitOfWork.DELETE, Collections.singletonList(student1));
+    context.put(IUnitOfWork.MODIFY, List.of(student1));
+    context.put(IUnitOfWork.DELETE, List.of(student1));
 
     studentRepository.commit();
 
@@ -126,8 +128,8 @@ public class StudentRepositoryTest {
 
   @Test
   public void shouldNotModifyToDbIfNotRegisteredStudentsToBeCommitted() {
-    context.put(IUnitOfWork.INSERT, Collections.singletonList(student1));
-    context.put(IUnitOfWork.DELETE, Collections.singletonList(student1));
+    context.put(IUnitOfWork.INSERT, List.of(student1));
+    context.put(IUnitOfWork.DELETE, List.of(student1));
 
     studentRepository.commit();
 
@@ -136,8 +138,8 @@ public class StudentRepositoryTest {
 
   @Test
   public void shouldNotDeleteFromDbIfNotRegisteredStudentsToBeCommitted() {
-    context.put(IUnitOfWork.INSERT, Collections.singletonList(student1));
-    context.put(IUnitOfWork.MODIFY, Collections.singletonList(student1));
+    context.put(IUnitOfWork.INSERT, List.of(student1));
+    context.put(IUnitOfWork.MODIFY, List.of(student1));
 
     studentRepository.commit();
 

value-object/src/test/java/com/iluwatar/value/object/AppTest.java

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

value-object/src/test/java/com/iluwatar/value/object/HeroStatTest.java

@@ -23,13 +23,13 @@
 
 package com.iluwatar.value.object;
 
-import com.google.common.testing.EqualsTester;
-import org.junit.jupiter.api.Test;
-
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.not;
 import static org.junit.Assert.assertThat;
 
+import com.google.common.testing.EqualsTester;
+import org.junit.jupiter.api.Test;
+
 /**
  * Unit test for HeroStat.
  */
@@ -37,12 +37,10 @@ public class HeroStatTest {
 
   /**
    * Tester for equals() and hashCode() methods of a class. Using guava's EqualsTester.
-   * 
+   *
    * @see <a href="http://static.javadoc.io/com.google.guava/guava-testlib/19.0/com/google/common/testing/EqualsTester.html">
-   * http://static.javadoc.io/com.google.guava/guava-testlib/19.0/com/google/common/testing/EqualsTester.html
-   * </a>
-   *
-   *
+   *     http://static.javadoc.io/com.google.guava/guava-testlib/19.0/com/google/common/testing/EqualsTester.html
+   *     </a>
    */
   @Test
   public void testEquals() {

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

@@ -28,22 +28,22 @@ package com.iluwatar.visitor;
  * can be added without altering the node interface.</p>
  *
  * <p>In this example there is a unit hierarchy beginning from {@link Commander}. This hierarchy is
- * traversed by visitors. {@link SoldierVisitor} applies its operation on {@link Soldier}s,
- * {@link SergeantVisitor} on {@link Sergeant}s and so on.</p>
- * 
+ * traversed by visitors. {@link SoldierVisitor} applies its operation on {@link Soldier}s, {@link
+ * SergeantVisitor} on {@link Sergeant}s and so on.</p>
  */
 public class App {
 
   /**
    * Program entry point.
-   * 
+   *
    * @param args command line args
    */
   public static void main(String[] args) {
 
-    var commander =
-        new Commander(new Sergeant(new Soldier(), new Soldier(), new Soldier()), new Sergeant(
-            new Soldier(), new Soldier(), new Soldier()));
+    var commander = new Commander(
+        new Sergeant(new Soldier(), new Soldier(), new Soldier()),
+        new Sergeant(new Soldier(), new Soldier(), new Soldier())
+    );
     commander.accept(new SoldierVisitor());
     commander.accept(new SergeantVisitor());
     commander.accept(new CommanderVisitor());

visitor/src/main/java/com/iluwatar/visitor/Unit.java

@@ -23,6 +23,8 @@
 
 package com.iluwatar.visitor;
 
+import java.util.Arrays;
+
 /**
  * Interface for the nodes in hierarchy.
  */
@@ -38,8 +40,6 @@ public abstract class Unit {
    * Accept visitor.
    */
   public void accept(UnitVisitor visitor) {
-    for (var child : children) {
-      child.accept(visitor);
-    }
+    Arrays.stream(children).forEach(child -> child.accept(visitor));
   }
 }

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

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

visitor/src/test/java/com/iluwatar/visitor/UnitTest.java

@@ -30,12 +30,11 @@ import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 import java.util.Arrays;
 import java.util.function.Function;
-
 import org.junit.jupiter.api.Test;
 
 /**
- * Date: 12/30/15 - 18:59 PM.
- * Test related to Units
+ * Date: 12/30/15 - 18:59 PM. Test related to Units
+ *
  * @param <U> Type of Unit
  * @author Jeroen Meulemeester
  */
@@ -65,9 +64,7 @@ public abstract class UnitTest<U extends Unit> {
     unit.accept(visitor);
     verifyVisit(unit, visitor);
 
-    for (final var child : children) {
-      verify(child).accept(eq(visitor));
-    }
+    Arrays.stream(children).forEach(child -> verify(child).accept(eq(visitor)));
 
     verifyNoMoreInteractions(children);
     verifyNoMoreInteractions(visitor);

visitor/src/test/java/com/iluwatar/visitor/VisitorTest.java

@@ -31,15 +31,14 @@ import ch.qos.logback.core.AppenderBase;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Optional;
-
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.LoggerFactory;
 
 /**
- * Date: 12/30/15 - 18:59 PM.
- * Test case for Visitor Pattern
+ * Date: 12/30/15 - 18:59 PM. Test case for Visitor Pattern
+ *
  * @param <V> Type of UnitVisitor
  * @author Jeroen Meulemeester
  */
@@ -84,11 +83,12 @@ public abstract class VisitorTest<V extends UnitVisitor> {
    * @param sergeantResponse  The optional expected response when being visited by a sergeant
    * @param soldierResponse   The optional expected response when being visited by a soldier
    */
-  public VisitorTest(final V visitor,
-                     final Optional<String> commanderResponse,
-                     final Optional<String> sergeantResponse,
-                     final Optional<String> soldierResponse) {
-
+  public VisitorTest(
+      final V visitor,
+      final Optional<String> commanderResponse,
+      final Optional<String> sergeantResponse,
+      final Optional<String> soldierResponse
+  ) {
     this.visitor = visitor;
     this.commanderResponse = commanderResponse;
     this.sergeantResponse = sergeantResponse;