java concurrency (#2502)

* fix spring config * fix spring config * fix spring config * minor fix * fix spring-boot module * fix pom * upgrade jackson * minor fix * java concurrency * cleanup
2017-08-27 12:14:26 +02:00
parent 09d10ac85f
commit 25263f1d6f
93 changed files with 362 additions and 44 deletions
--- a/core-java-concurrency/src/test/java/com/baeldung/completablefuture/CompletableFutureLongRunningUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/completablefuture/CompletableFutureLongRunningUnitTest.java
@@ -0,0 +1,184 @@
+package com.baeldung.completablefuture;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class CompletableFutureLongRunningUnitTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(CompletableFutureLongRunningUnitTest.class);
+
+    @Test
+    public void whenRunningCompletableFutureAsynchronously_thenGetMethodWaitsForResult() throws InterruptedException, ExecutionException {
+        Future<String> completableFuture = calculateAsync();
+
+        String result = completableFuture.get();
+        assertEquals("Hello", result);
+    }
+
+    private Future<String> calculateAsync() throws InterruptedException {
+        CompletableFuture<String> completableFuture = new CompletableFuture<>();
+
+        Executors.newCachedThreadPool()
+            .submit(() -> {
+                Thread.sleep(500);
+                completableFuture.complete("Hello");
+                return null;
+            });
+
+        return completableFuture;
+    }
+
+    @Test
+    public void whenRunningCompletableFutureWithResult_thenGetMethodReturnsImmediately() throws InterruptedException, ExecutionException {
+        Future<String> completableFuture = CompletableFuture.completedFuture("Hello");
+
+        String result = completableFuture.get();
+        assertEquals("Hello", result);
+    }
+
+    private Future<String> calculateAsyncWithCancellation() throws InterruptedException {
+        CompletableFuture<String> completableFuture = new CompletableFuture<>();
+
+        Executors.newCachedThreadPool()
+            .submit(() -> {
+                Thread.sleep(500);
+                completableFuture.cancel(false);
+                return null;
+            });
+
+        return completableFuture;
+    }
+
+    @Test(expected = CancellationException.class)
+    public void whenCancelingTheFuture_thenThrowsCancellationException() throws ExecutionException, InterruptedException {
+        Future<String> future = calculateAsyncWithCancellation();
+        future.get();
+    }
+
+    @Test
+    public void whenCreatingCompletableFutureWithSupplyAsync_thenFutureReturnsValue() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> "Hello");
+
+        assertEquals("Hello", future.get());
+    }
+
+    @Test
+    public void whenAddingThenAcceptToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
+
+        CompletableFuture<Void> future = completableFuture.thenAccept(s -> LOG.debug("Computation returned: " + s));
+
+        future.get();
+    }
+
+    @Test
+    public void whenAddingThenRunToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
+
+        CompletableFuture<Void> future = completableFuture.thenRun(() -> LOG.debug("Computation finished."));
+
+        future.get();
+    }
+
+    @Test
+    public void whenAddingThenApplyToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
+
+        CompletableFuture<String> future = completableFuture.thenApply(s -> s + " World");
+
+        assertEquals("Hello World", future.get());
+    }
+
+    @Test
+    public void whenUsingThenCompose_thenFuturesExecuteSequentially() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello")
+            .thenCompose(s -> CompletableFuture.supplyAsync(() -> s + " World"));
+
+        assertEquals("Hello World", completableFuture.get());
+    }
+
+    @Test
+    public void whenUsingThenCombine_thenWaitForExecutionOfBothFutures() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello")
+            .thenCombine(CompletableFuture.supplyAsync(() -> " World"), (s1, s2) -> s1 + s2);
+
+        assertEquals("Hello World", completableFuture.get());
+    }
+
+    @Test
+    public void whenUsingThenAcceptBoth_thenWaitForExecutionOfBothFutures() throws ExecutionException, InterruptedException {
+        CompletableFuture.supplyAsync(() -> "Hello")
+            .thenAcceptBoth(CompletableFuture.supplyAsync(() -> " World"), (s1, s2) -> LOG.debug(s1 + s2));
+    }
+
+    @Test
+    public void whenFutureCombinedWithAllOfCompletes_thenAllFuturesAreDone() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> future1 = CompletableFuture.supplyAsync(() -> "Hello");
+        CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> "Beautiful");
+        CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> "World");
+
+        CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(future1, future2, future3);
+
+        // ...
+
+        combinedFuture.get();
+
+        assertTrue(future1.isDone());
+        assertTrue(future2.isDone());
+        assertTrue(future3.isDone());
+
+        String combined = Stream.of(future1, future2, future3)
+            .map(CompletableFuture::join)
+            .collect(Collectors.joining(" "));
+
+        assertEquals("Hello Beautiful World", combined);
+    }
+
+    @Test
+    public void whenFutureThrows_thenHandleMethodReceivesException() throws ExecutionException, InterruptedException {
+        String name = null;
+
+        // ...
+
+        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> {
+            if (name == null) {
+                throw new RuntimeException("Computation error!");
+            }
+            return "Hello, " + name;
+        })
+            .handle((s, t) -> s != null ? s : "Hello, Stranger!");
+
+        assertEquals("Hello, Stranger!", completableFuture.get());
+    }
+
+    @Test(expected = ExecutionException.class)
+    public void whenCompletingFutureExceptionally_thenGetMethodThrows() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> completableFuture = new CompletableFuture<>();
+
+        // ...
+
+        completableFuture.completeExceptionally(new RuntimeException("Calculation failed!"));
+
+        // ...
+
+        completableFuture.get();
+    }
+
+    @Test
+    public void whenAddingThenApplyAsyncToFuture_thenFunctionExecutesAfterComputationIsFinished() throws ExecutionException, InterruptedException {
+        CompletableFuture<String> completableFuture = CompletableFuture.supplyAsync(() -> "Hello");
+
+        CompletableFuture<String> future = completableFuture.thenApplyAsync(s -> s + " World");
+
+        assertEquals("Hello World", future.get());
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/accumulator/LongAccumulatorUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/accumulator/LongAccumulatorUnitTest.java
@@ -0,0 +1,38 @@
+package com.baeldung.concurrent.accumulator;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.LongAccumulator;
+import java.util.function.LongBinaryOperator;
+import java.util.stream.IntStream;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class LongAccumulatorUnitTest {
+
+    @Test
+    public void givenLongAccumulator_whenApplyActionOnItFromMultipleThrads_thenShouldProduceProperResult() throws InterruptedException {
+        // given
+        ExecutorService executorService = Executors.newFixedThreadPool(8);
+        LongBinaryOperator sum = Long::sum;
+        LongAccumulator accumulator = new LongAccumulator(sum, 0L);
+        int numberOfThreads = 4;
+        int numberOfIncrements = 100;
+
+        // when
+        Runnable accumulateAction = () -> IntStream.rangeClosed(0, numberOfIncrements).forEach(accumulator::accumulate);
+
+        for (int i = 0; i < numberOfThreads; i++) {
+            executorService.execute(accumulateAction);
+        }
+
+        // then
+        executorService.awaitTermination(500, TimeUnit.MILLISECONDS);
+        executorService.shutdown();
+        assertEquals(accumulator.get(), 20200);
+
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/adder/LongAdderUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/adder/LongAdderUnitTest.java
@@ -0,0 +1,67 @@
+package com.baeldung.concurrent.adder;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.LongAdder;
+import java.util.stream.IntStream;
+
+import static com.jayway.awaitility.Awaitility.await;
+import static junit.framework.TestCase.assertEquals;
+
+public class LongAdderUnitTest {
+    @Test
+    public void givenMultipleThread_whenTheyWriteToSharedLongAdder_thenShouldCalculateSumForThem() throws InterruptedException {
+        //given
+        LongAdder counter = new LongAdder();
+        ExecutorService executorService = Executors.newFixedThreadPool(8);
+
+        int numberOfThreads = 4;
+        int numberOfIncrements = 100;
+
+        //when
+        Runnable incrementAction = () -> IntStream
+          .range(0, numberOfIncrements)
+          .forEach((i) -> counter.increment());
+
+        for (int i = 0; i < numberOfThreads; i++) {
+            executorService.execute(incrementAction);
+        }
+
+        //then
+        executorService.awaitTermination(500, TimeUnit.MILLISECONDS);
+        executorService.shutdown();
+
+        assertEquals(counter.sum(), numberOfIncrements * numberOfThreads);
+        assertEquals(counter.sum(), numberOfIncrements * numberOfThreads);
+    }
+
+    @Test
+    public void givenMultipleThread_whenTheyWriteToSharedLongAdder_thenShouldCalculateSumForThemAndResetAdderAfterward() throws InterruptedException {
+        //given
+        LongAdder counter = new LongAdder();
+        ExecutorService executorService = Executors.newFixedThreadPool(8);
+
+        int numberOfThreads = 4;
+        int numberOfIncrements = 100;
+
+        //when
+        Runnable incrementAction = () -> IntStream
+          .range(0, numberOfIncrements)
+          .forEach((i) -> counter.increment());
+
+        for (int i = 0; i < numberOfThreads; i++) {
+            executorService.execute(incrementAction);
+        }
+
+        //then
+        executorService.awaitTermination(500, TimeUnit.MILLISECONDS);
+        executorService.shutdown();
+
+        assertEquals(counter.sumThenReset(), numberOfIncrements * numberOfThreads);
+
+        await().until(() -> assertEquals(counter.sum(), 0));
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/atomic/ThreadSafeCounterTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/atomic/ThreadSafeCounterTest.java
@@ -0,0 +1,38 @@
+package com.baeldung.concurrent.atomic;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import org.junit.Test;
+
+public class ThreadSafeCounterTest {
+
+    @Test
+    public void givenMultiThread_whenSafeCounterWithLockIncrement() throws InterruptedException {
+        ExecutorService service = Executors.newFixedThreadPool(3);
+        SafeCounterWithLock safeCounter = new SafeCounterWithLock();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(safeCounter::increment));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, safeCounter.getValue());
+    }
+    
+    @Test
+    public void givenMultiThread_whenSafeCounterWithoutLockIncrement() throws InterruptedException {
+        ExecutorService service = Executors.newFixedThreadPool(3);
+        SafeCounterWithoutLock safeCounter = new SafeCounterWithoutLock();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(safeCounter::increment));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, safeCounter.getValue());
+    }
+    
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/atomic/ThreadUnsafeCounterManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/atomic/ThreadUnsafeCounterManualTest.java
@@ -0,0 +1,33 @@
+package com.baeldung.concurrent.atomic;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import org.junit.Test;
+
+/**
+ * This test shows the behaviour of a thread-unsafe class in a multithreaded scenario. We are calling
+ * the increment methods 1000 times from a pool of 3 threads. In most of the cases, the counter will 
+ * less than 1000, because of lost updates, however, occasionally it may reach 1000, when no threads
+ * called the method simultaneously. This may cause the build to fail occasionally. Hence excluding this
+ * test from build by adding this in manual test
+ */
+public class ThreadUnsafeCounterManualTest {
+
+    @Test
+    public void givenMultiThread_whenUnsafeCounterIncrement() throws InterruptedException {
+        ExecutorService service = Executors.newFixedThreadPool(3);
+        UnsafeCounter unsafeCounter = new UnsafeCounter();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(unsafeCounter::increment));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, unsafeCounter.getValue());
+    }
+    
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/copyonwrite/CopyOnWriteArrayListUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/copyonwrite/CopyOnWriteArrayListUnitTest.java
@@ -0,0 +1,53 @@
+package com.baeldung.concurrent.copyonwrite;
+
+
+import org.junit.Test;
+
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+
+public class CopyOnWriteArrayListUnitTest {
+
+    @Test
+    public void givenCopyOnWriteList_whenIterateAndAddElementToUnderneathList_thenShouldNotChangeIterator() {
+        //given
+        final CopyOnWriteArrayList<Integer> numbers =
+          new CopyOnWriteArrayList<>(new Integer[]{1, 3, 5, 8});
+
+        //when
+        Iterator<Integer> iterator = numbers.iterator();
+        numbers.add(10);
+
+        //then
+        List<Integer> result = new LinkedList<>();
+        iterator.forEachRemaining(result::add);
+        assertThat(result).containsOnly(1, 3, 5, 8);
+
+        //and
+        Iterator<Integer> iterator2 = numbers.iterator();
+        List<Integer> result2 = new LinkedList<>();
+        iterator2.forEachRemaining(result2::add);
+
+        //then
+        assertThat(result2).containsOnly(1, 3, 5, 8, 10);
+
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void givenCopyOnWriteList_whenIterateOverItAndTryToRemoveElement_thenShouldThrowException() {
+        //given
+        final CopyOnWriteArrayList<Integer> numbers =
+          new CopyOnWriteArrayList<>(new Integer[]{1, 3, 5, 8});
+
+        //when
+        Iterator<Integer> iterator = numbers.iterator();
+        while (iterator.hasNext()) {
+            iterator.remove();
+        }
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchExampleIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchExampleIntegrationTest.java
@@ -0,0 +1,70 @@
+package com.baeldung.concurrent.countdownlatch;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Stream;
+
+import static java.util.stream.Collectors.toList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class CountdownLatchExampleIntegrationTest {
+    @Test
+    public void whenParallelProcessing_thenMainThreadWillBlockUntilCompletion() throws InterruptedException {
+        // Given
+        List<String> outputScraper = Collections.synchronizedList(new ArrayList<>());
+        CountDownLatch countDownLatch = new CountDownLatch(5);
+        List<Thread> workers = Stream.generate(() -> new Thread(new Worker(outputScraper, countDownLatch))).limit(5).collect(toList());
+
+        // When
+        workers.forEach(Thread::start);
+        countDownLatch.await(); // Block until workers finish
+        outputScraper.add("Latch released");
+
+        // Then
+        outputScraper.forEach(Object::toString);
+        assertThat(outputScraper).containsExactly("Counted down", "Counted down", "Counted down", "Counted down", "Counted down", "Latch released");
+    }
+
+    @Test
+    public void whenFailingToParallelProcess_thenMainThreadShouldTimeout() throws InterruptedException {
+        // Given
+        List<String> outputScraper = Collections.synchronizedList(new ArrayList<>());
+        CountDownLatch countDownLatch = new CountDownLatch(5);
+        List<Thread> workers = Stream.generate(() -> new Thread(new BrokenWorker(outputScraper, countDownLatch))).limit(5).collect(toList());
+
+        // When
+        workers.forEach(Thread::start);
+        final boolean result = countDownLatch.await(3L, TimeUnit.SECONDS);
+
+        // Then
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void whenDoingLotsOfThreadsInParallel_thenStartThemAtTheSameTime() throws InterruptedException {
+        // Given
+        List<String> outputScraper = Collections.synchronizedList(new ArrayList<>());
+        CountDownLatch readyThreadCounter = new CountDownLatch(5);
+        CountDownLatch callingThreadBlocker = new CountDownLatch(1);
+        CountDownLatch completedThreadCounter = new CountDownLatch(5);
+        List<Thread> workers = Stream.generate(() -> new Thread(new WaitingWorker(outputScraper, readyThreadCounter, callingThreadBlocker, completedThreadCounter))).limit(5).collect(toList());
+
+        // When
+        workers.forEach(Thread::start);
+        readyThreadCounter.await(); // Block until workers start
+        outputScraper.add("Workers ready");
+        callingThreadBlocker.countDown(); // Start workers
+        completedThreadCounter.await(); // Block until workers finish
+        outputScraper.add("Workers complete");
+
+        // Then
+        outputScraper.forEach(Object::toString);
+        assertThat(outputScraper).containsExactly("Workers ready", "Counted down", "Counted down", "Counted down", "Counted down", "Counted down", "Workers complete");
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/delayqueue/DelayQueueIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/delayqueue/DelayQueueIntegrationTest.java
@@ -0,0 +1,82 @@
+package com.baeldung.concurrent.delayqueue;
+
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.DelayQueue;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import static junit.framework.TestCase.assertEquals;
+
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class DelayQueueIntegrationTest {
+    @Test
+    public void givenDelayQueue_whenProduceElement_thenShouldConsumeAfterGivenDelay() throws InterruptedException {
+        //given
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        BlockingQueue<DelayObject> queue = new DelayQueue<>();
+        int numberOfElementsToProduce = 2;
+        int delayOfEachProducedMessageMilliseconds = 500;
+        DelayQueueConsumer consumer = new DelayQueueConsumer(queue, numberOfElementsToProduce);
+        DelayQueueProducer producer
+          = new DelayQueueProducer(queue, numberOfElementsToProduce, delayOfEachProducedMessageMilliseconds);
+
+        //when
+        executor.submit(producer);
+        executor.submit(consumer);
+
+        //then
+        executor.awaitTermination(5, TimeUnit.SECONDS);
+        executor.shutdown();
+        assertEquals(consumer.numberOfConsumedElements.get(), numberOfElementsToProduce);
+
+    }
+
+    @Test
+    public void givenDelayQueue_whenProduceElementWithHugeDelay_thenConsumerWasNotAbleToConsumeMessageInGivenTime() throws InterruptedException {
+        //given
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        BlockingQueue<DelayObject> queue = new DelayQueue<>();
+        int numberOfElementsToProduce = 1;
+        int delayOfEachProducedMessageMilliseconds = 10_000;
+        DelayQueueConsumer consumer = new DelayQueueConsumer(queue, numberOfElementsToProduce);
+        DelayQueueProducer producer
+          = new DelayQueueProducer(queue, numberOfElementsToProduce, delayOfEachProducedMessageMilliseconds);
+
+        //when
+        executor.submit(producer);
+        executor.submit(consumer);
+
+        //then
+        executor.awaitTermination(5, TimeUnit.SECONDS);
+        executor.shutdown();
+        assertEquals(consumer.numberOfConsumedElements.get(), 0);
+
+    }
+
+    @Test
+    public void givenDelayQueue_whenProduceElementWithNegativeDelay_thenConsumeMessageImmediately() throws InterruptedException {
+        //given
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        BlockingQueue<DelayObject> queue = new DelayQueue<>();
+        int numberOfElementsToProduce = 1;
+        int delayOfEachProducedMessageMilliseconds = -10_000;
+        DelayQueueConsumer consumer = new DelayQueueConsumer(queue, numberOfElementsToProduce);
+        DelayQueueProducer producer
+          = new DelayQueueProducer(queue, numberOfElementsToProduce, delayOfEachProducedMessageMilliseconds);
+
+        //when
+        executor.submit(producer);
+        executor.submit(consumer);
+
+        //then
+        executor.awaitTermination(1, TimeUnit.SECONDS);
+        executor.shutdown();
+        assertEquals(consumer.numberOfConsumedElements.get(), 1);
+
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/future/FactorialSquareCalculatorUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/future/FactorialSquareCalculatorUnitTest.java
@@ -0,0 +1,22 @@
+package com.baeldung.concurrent.future;
+
+import org.junit.Test;
+
+import java.util.concurrent.ForkJoinPool;
+
+import static org.junit.Assert.assertEquals;
+
+public class FactorialSquareCalculatorUnitTest {
+
+    @Test
+    public void whenCalculatesFactorialSquare_thenReturnCorrectValue() {
+        ForkJoinPool forkJoinPool = new ForkJoinPool();
+
+        FactorialSquareCalculator calculator = new FactorialSquareCalculator(10);
+
+        forkJoinPool.execute(calculator);
+
+        assertEquals("The sum of the squares from 1 to 10 is 385", 385, calculator.join().intValue());
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/future/SquareCalculatorIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/future/SquareCalculatorIntegrationTest.java
@@ -0,0 +1,99 @@
+package com.baeldung.concurrent.future;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TestName;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class SquareCalculatorIntegrationTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(SquareCalculatorIntegrationTest.class);
+
+
+    @Rule
+    public TestName name = new TestName();
+
+    private long start;
+
+    private SquareCalculator squareCalculator;
+
+    @Test
+    public void givenExecutorIsSingleThreaded_whenTwoExecutionsAreTriggered_thenRunInSequence() throws InterruptedException, ExecutionException {
+        squareCalculator = new SquareCalculator(Executors.newSingleThreadExecutor());
+
+        Future<Integer> result1 = squareCalculator.calculate(4);
+        Future<Integer> result2 = squareCalculator.calculate(1000);
+
+        while (!result1.isDone() || !result2.isDone()) {
+            LOG.debug(String.format("Task 1 is %s and Task 2 is %s.", result1.isDone() ? "done" : "not done", result2.isDone() ? "done" : "not done"));
+
+            Thread.sleep(300);
+        }
+
+        assertEquals(16, result1.get().intValue());
+        assertEquals(1000000, result2.get().intValue());
+    }
+
+    @Test(expected = TimeoutException.class)
+    public void whenGetWithTimeoutLowerThanExecutionTime_thenThrowException() throws InterruptedException, ExecutionException, TimeoutException {
+        squareCalculator = new SquareCalculator(Executors.newSingleThreadExecutor());
+
+        Future<Integer> result = squareCalculator.calculate(4);
+
+        result.get(500, TimeUnit.MILLISECONDS);
+    }
+
+    @Test
+    public void givenExecutorIsMultiThreaded_whenTwoExecutionsAreTriggered_thenRunInParallel() throws InterruptedException, ExecutionException {
+        squareCalculator = new SquareCalculator(Executors.newFixedThreadPool(2));
+
+        Future<Integer> result1 = squareCalculator.calculate(4);
+        Future<Integer> result2 = squareCalculator.calculate(1000);
+
+        while (!result1.isDone() || !result2.isDone()) {
+            LOG.debug(String.format("Task 1 is %s and Task 2 is %s.", result1.isDone() ? "done" : "not done", result2.isDone() ? "done" : "not done"));
+
+            Thread.sleep(300);
+        }
+
+        assertEquals(16, result1.get().intValue());
+        assertEquals(1000000, result2.get().intValue());
+    }
+
+    @Test(expected = CancellationException.class)
+    public void whenCancelFutureAndCallGet_thenThrowException() throws InterruptedException, ExecutionException, TimeoutException {
+        squareCalculator = new SquareCalculator(Executors.newSingleThreadExecutor());
+
+        Future<Integer> result = squareCalculator.calculate(4);
+
+        boolean canceled = result.cancel(true);
+
+        assertTrue("Future was canceled", canceled);
+        assertTrue("Future was canceled", result.isCancelled());
+
+        result.get();
+    }
+
+    @Before
+    public void start() {
+        start = System.currentTimeMillis();
+    }
+
+    @After
+    public void end() {
+        LOG.debug(String.format("Test %s took %s ms \n", name.getMethodName(), System.currentTimeMillis() - start));
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/locks/SharedObjectWithLockManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/locks/SharedObjectWithLockManualTest.java
@@ -0,0 +1,73 @@
+package com.baeldung.concurrent.locks;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class SharedObjectWithLockManualTest {
+
+    @Test
+    public void whenLockAcquired_ThenLockedIsTrue() {
+        final SharedObjectWithLock object = new SharedObjectWithLock();
+
+        final int threadCount = 2;
+        final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+        executeThreads(object, threadCount, service);
+
+        assertEquals(true, object.isLocked());
+
+        service.shutdown();
+    }
+
+    @Test
+    public void whenLocked_ThenQueuedThread() {
+        final int threadCount = 4;
+        final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+        final SharedObjectWithLock object = new SharedObjectWithLock();
+
+        executeThreads(object, threadCount, service);
+
+        assertEquals(object.hasQueuedThreads(), true);
+
+        service.shutdown();
+
+    }
+
+    public void whenTryLock_ThenQueuedThread() {
+        final SharedObjectWithLock object = new SharedObjectWithLock();
+
+        final int threadCount = 2;
+        final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+        executeThreads(object, threadCount, service);
+
+        assertEquals(true, object.isLocked());
+
+        service.shutdown();
+    }
+
+    @Test
+    public void whenGetCount_ThenCorrectCount() throws InterruptedException {
+        final int threadCount = 4;
+        final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+        final SharedObjectWithLock object = new SharedObjectWithLock();
+
+        executeThreads(object, threadCount, service);
+        Thread.sleep(1000);
+        assertEquals(object.getCounter(), 4);
+
+        service.shutdown();
+
+    }
+
+    private void executeThreads(SharedObjectWithLock object, int threadCount, ExecutorService service) {
+        for (int i = 0; i < threadCount; i++) {
+            service.execute(object::perform);
+        }
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/locks/SynchronizedHashMapWithRWLockManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/locks/SynchronizedHashMapWithRWLockManualTest.java
@@ -0,0 +1,57 @@
+package com.baeldung.concurrent.locks;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class SynchronizedHashMapWithRWLockManualTest {
+
+    @Test
+    public void whenWriting_ThenNoReading() {
+        SynchronizedHashMapWithRWLock object = new SynchronizedHashMapWithRWLock();
+        final int threadCount = 3;
+        final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+        executeWriterThreads(object, threadCount, service);
+
+        assertEquals(object.isReadLockAvailable(), false);
+
+        service.shutdown();
+    }
+
+    @Test
+    public void whenReading_ThenMultipleReadingAllowed() {
+        SynchronizedHashMapWithRWLock object = new SynchronizedHashMapWithRWLock();
+        final int threadCount = 5;
+        final ExecutorService service = Executors.newFixedThreadPool(threadCount);
+
+        executeReaderThreads(object, threadCount, service);
+
+        assertEquals(object.isReadLockAvailable(), true);
+
+        service.shutdown();
+    }
+
+    private void executeWriterThreads(SynchronizedHashMapWithRWLock object, int threadCount, ExecutorService service) {
+        for (int i = 0; i < threadCount; i++) {
+            service.execute(() -> {
+                try {
+                    object.put("key" + threadCount, "value" + threadCount);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+            });
+        }
+    }
+
+    private void executeReaderThreads(SynchronizedHashMapWithRWLock object, int threadCount, ExecutorService service) {
+        for (int i = 0; i < threadCount; i++)
+            service.execute(() -> {
+                object.get("key" + threadCount);
+            });
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/phaser/PhaserUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/phaser/PhaserUnitTest.java
@@ -0,0 +1,41 @@
+package com.baeldung.concurrent.phaser;
+
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Phaser;
+
+import static junit.framework.TestCase.assertEquals;
+
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class PhaserUnitTest {
+
+    @Test
+    public void givenPhaser_whenCoordinateWorksBetweenThreads_thenShouldCoordinateBetweenMultiplePhases() {
+        //given
+        ExecutorService executorService = Executors.newCachedThreadPool();
+        Phaser ph = new Phaser(1);
+        assertEquals(0, ph.getPhase());
+
+        //when
+        executorService.submit(new LongRunningAction("thread-1", ph));
+        executorService.submit(new LongRunningAction("thread-2", ph));
+        executorService.submit(new LongRunningAction("thread-3", ph));
+
+        //then
+        ph.arriveAndAwaitAdvance();
+        assertEquals(1, ph.getPhase());
+
+        //and
+        executorService.submit(new LongRunningAction("thread-4", ph));
+        executorService.submit(new LongRunningAction("thread-5", ph));
+        ph.arriveAndAwaitAdvance();
+        assertEquals(2, ph.getPhase());
+
+
+        ph.arriveAndDeregister();
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/priorityblockingqueue/PriorityBlockingQueueIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/priorityblockingqueue/PriorityBlockingQueueIntegrationTest.java
@@ -0,0 +1,57 @@
+package com.baeldung.concurrent.priorityblockingqueue;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.concurrent.PriorityBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.util.Lists.newArrayList;
+
+public class PriorityBlockingQueueIntegrationTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(PriorityBlockingQueueIntegrationTest.class);
+
+
+    @Test
+    public void givenUnorderedValues_whenPolling_thenShouldOrderQueue() throws InterruptedException {
+        PriorityBlockingQueue<Integer> queue = new PriorityBlockingQueue<>();
+        ArrayList<Integer> polledElements = new ArrayList<>();
+
+        queue.add(1);
+        queue.add(5);
+        queue.add(2);
+        queue.add(3);
+        queue.add(4);
+
+        queue.drainTo(polledElements);
+
+        assertThat(polledElements).containsExactly(1, 2, 3, 4, 5);
+    }
+
+    @Test
+    public void whenPollingEmptyQueue_thenShouldBlockThread() throws InterruptedException {
+        PriorityBlockingQueue<Integer> queue = new PriorityBlockingQueue<>();
+
+        final Thread thread = new Thread(() -> {
+            LOG.debug("Polling...");
+            while (true) {
+                try {
+                    Integer poll = queue.take();
+                    LOG.debug("Polled: " + poll);
+                } catch (InterruptedException ignored) {
+                }
+            }
+        });
+        thread.start();
+
+        Thread.sleep(TimeUnit.SECONDS.toMillis(5));
+        LOG.debug("Adding to queue");
+
+        queue.addAll(newArrayList(1, 5, 6, 1, 2, 6, 7));
+        Thread.sleep(TimeUnit.SECONDS.toMillis(1));
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/semaphores/SemaphoresManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/semaphores/SemaphoresManualTest.java
@@ -0,0 +1,114 @@
+package com.baeldung.concurrent.semaphores;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class SemaphoresManualTest {
+
+    // ========= login queue ======
+
+    @Test
+    public void givenLoginQueue_whenReachLimit_thenBlocked() {
+        final int slots = 10;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final LoginQueueUsingSemaphore loginQueue = new LoginQueueUsingSemaphore(slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(loginQueue::tryLogin));
+        executorService.shutdown();
+
+        assertEquals(0, loginQueue.availableSlots());
+        assertFalse(loginQueue.tryLogin());
+    }
+
+    @Test
+    public void givenLoginQueue_whenLogout_thenSlotsAvailable() {
+        final int slots = 10;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final LoginQueueUsingSemaphore loginQueue = new LoginQueueUsingSemaphore(slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(loginQueue::tryLogin));
+        executorService.shutdown();
+
+        assertEquals(0, loginQueue.availableSlots());
+        loginQueue.logout();
+        assertTrue(loginQueue.availableSlots() > 0);
+        assertTrue(loginQueue.tryLogin());
+    }
+
+    // ========= delay queue =======
+
+    @Test
+    public void givenDelayQueue_whenReachLimit_thenBlocked() {
+        final int slots = 50;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final DelayQueueUsingTimedSemaphore delayQueue = new DelayQueueUsingTimedSemaphore(1, slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(delayQueue::tryAdd));
+        executorService.shutdown();
+
+        assertEquals(0, delayQueue.availableSlots());
+        assertFalse(delayQueue.tryAdd());
+    }
+
+    @Test
+    public void givenDelayQueue_whenTimePass_thenSlotsAvailable() throws InterruptedException {
+        final int slots = 50;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final DelayQueueUsingTimedSemaphore delayQueue = new DelayQueueUsingTimedSemaphore(1, slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(delayQueue::tryAdd));
+        executorService.shutdown();
+
+        assertEquals(0, delayQueue.availableSlots());
+        Thread.sleep(1000);
+        assertTrue(delayQueue.availableSlots() > 0);
+        assertTrue(delayQueue.tryAdd());
+    }
+
+    // ========== mutex ========
+
+    @Test
+    public void whenMutexAndMultipleThreads_thenBlocked() throws InterruptedException {
+        final int count = 5;
+        final ExecutorService executorService = Executors.newFixedThreadPool(count);
+        final CounterUsingMutex counter = new CounterUsingMutex();
+        IntStream.range(0, count)
+          .forEach(user -> executorService.execute(() -> {
+              try {
+                  counter.increase();
+              } catch (final InterruptedException e) {
+                  e.printStackTrace();
+              }
+          }));
+        executorService.shutdown();
+
+        assertTrue(counter.hasQueuedThreads());
+    }
+
+    @Test
+    public void givenMutexAndMultipleThreads_ThenDelay_thenCorrectCount() throws InterruptedException {
+        final int count = 5;
+        final ExecutorService executorService = Executors.newFixedThreadPool(count);
+        final CounterUsingMutex counter = new CounterUsingMutex();
+        IntStream.range(0, count)
+          .forEach(user -> executorService.execute(() -> {
+              try {
+                  counter.increase();
+              } catch (final InterruptedException e) {
+                  e.printStackTrace();
+              }
+          }));
+        executorService.shutdown();
+        assertTrue(counter.hasQueuedThreads());
+        Thread.sleep(5000);
+        assertFalse(counter.hasQueuedThreads());
+        assertEquals(count, counter.getCount());
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/skiplist/ConcurrentSkipListSetIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/skiplist/ConcurrentSkipListSetIntegrationTest.java
@@ -0,0 +1,120 @@
+package com.baeldung.concurrent.skiplist;
+
+import org.junit.Test;
+
+import java.time.ZonedDateTime;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentNavigableMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ConcurrentSkipListSetIntegrationTest {
+
+    @Test
+    public void givenThreadsProducingEvents_whenGetForEventsFromLastMinute_thenReturnThoseEventsInTheLockFreeWay() throws InterruptedException {
+        //given
+        ExecutorService executorService = Executors.newFixedThreadPool(3);
+        EventWindowSort eventWindowSort = new EventWindowSort();
+        int numberOfThreads = 2;
+        //when
+        Runnable producer = () -> IntStream
+          .rangeClosed(0, 100)
+          .forEach(index -> eventWindowSort.acceptEvent(new Event(ZonedDateTime
+            .now()
+            .minusSeconds(index), UUID
+            .randomUUID()
+            .toString())));
+
+        for (int i = 0; i < numberOfThreads; i++) {
+            executorService.execute(producer);
+        }
+
+        Thread.sleep(500);
+
+        ConcurrentNavigableMap<ZonedDateTime, String> eventsFromLastMinute = eventWindowSort.getEventsFromLastMinute();
+
+        long eventsOlderThanOneMinute = eventsFromLastMinute
+          .entrySet()
+          .stream()
+          .filter(e -> e
+            .getKey()
+            .isBefore(ZonedDateTime
+              .now()
+              .minusMinutes(1)))
+          .count();
+        assertEquals(eventsOlderThanOneMinute, 0);
+
+        long eventYoungerThanOneMinute = eventsFromLastMinute
+          .entrySet()
+          .stream()
+          .filter(e -> e
+            .getKey()
+            .isAfter(ZonedDateTime
+              .now()
+              .minusMinutes(1)))
+          .count();
+
+        //then
+        assertTrue(eventYoungerThanOneMinute > 0);
+
+        executorService.awaitTermination(1, TimeUnit.SECONDS);
+        executorService.shutdown();
+    }
+
+    @Test
+    public void givenThreadsProducingEvents_whenGetForEventsOlderThanOneMinute_thenReturnThoseEventsInTheLockFreeWay() throws InterruptedException {
+        //given
+        ExecutorService executorService = Executors.newFixedThreadPool(3);
+        EventWindowSort eventWindowSort = new EventWindowSort();
+        int numberOfThreads = 2;
+        //when
+        Runnable producer = () -> IntStream
+          .rangeClosed(0, 100)
+          .forEach(index -> eventWindowSort.acceptEvent(new Event(ZonedDateTime
+            .now()
+            .minusSeconds(index), UUID
+            .randomUUID()
+            .toString())));
+
+        for (int i = 0; i < numberOfThreads; i++) {
+            executorService.execute(producer);
+        }
+
+        Thread.sleep(500);
+
+        ConcurrentNavigableMap<ZonedDateTime, String> eventsFromLastMinute = eventWindowSort.getEventsOlderThatOneMinute();
+
+        long eventsOlderThanOneMinute = eventsFromLastMinute
+          .entrySet()
+          .stream()
+          .filter(e -> e
+            .getKey()
+            .isBefore(ZonedDateTime
+              .now()
+              .minusMinutes(1)))
+          .count();
+        assertTrue(eventsOlderThanOneMinute > 0);
+
+        long eventYoungerThanOneMinute = eventsFromLastMinute
+          .entrySet()
+          .stream()
+          .filter(e -> e
+            .getKey()
+            .isAfter(ZonedDateTime
+              .now()
+              .minusMinutes(1)))
+          .count();
+
+        //then
+        assertEquals(eventYoungerThanOneMinute, 0);
+
+        executorService.awaitTermination(1, TimeUnit.SECONDS);
+        executorService.shutdown();
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/synchronize/BaeldungSychronizedBlockTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/synchronize/BaeldungSychronizedBlockTest.java
@@ -0,0 +1,37 @@
+package com.baeldung.concurrent.synchronize;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertEquals;
+
+public class BaeldungSychronizedBlockTest {
+
+    @Test
+    public void givenMultiThread_whenBlockSync() throws InterruptedException {
+        ExecutorService service = Executors.newFixedThreadPool(3);
+        BaeldungSynchronizedBlocks synchronizedBlocks = new BaeldungSynchronizedBlocks();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(synchronizedBlocks::performSynchronisedTask));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, synchronizedBlocks.getCount());
+    }
+
+    @Test
+    public void givenMultiThread_whenStaticSyncBlock() throws InterruptedException {
+        ExecutorService service = Executors.newCachedThreadPool();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(BaeldungSynchronizedBlocks::performStaticSyncTask));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, BaeldungSynchronizedBlocks.getStaticCount());
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/synchronize/BaeldungSynchronizeMethodsTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/synchronize/BaeldungSynchronizeMethodsTest.java
@@ -0,0 +1,51 @@
+package com.baeldung.concurrent.synchronize;
+
+import org.junit.Ignore;
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertEquals;
+
+public class BaeldungSynchronizeMethodsTest {
+
+    @Test
+    @Ignore
+    public void givenMultiThread_whenNonSyncMethod() throws InterruptedException {
+        ExecutorService service = Executors.newFixedThreadPool(3);
+        BaeldungSynchronizedMethods method = new BaeldungSynchronizedMethods();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(method::calculate));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, method.getSum());
+    }
+
+    @Test
+    public void givenMultiThread_whenMethodSync() throws InterruptedException {
+        ExecutorService service = Executors.newFixedThreadPool(3);
+        BaeldungSynchronizedMethods method = new BaeldungSynchronizedMethods();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(method::synchronisedCalculate));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, method.getSyncSum());
+    }
+
+    @Test
+    public void givenMultiThread_whenStaticSyncMethod() throws InterruptedException {
+        ExecutorService service = Executors.newCachedThreadPool();
+
+        IntStream.range(0, 1000)
+          .forEach(count -> service.submit(BaeldungSynchronizedMethods::syncStaticCalculate));
+        service.awaitTermination(100, TimeUnit.MILLISECONDS);
+
+        assertEquals(1000, BaeldungSynchronizedMethods.staticSum);
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/concurrent/volatilekeyword/SharedObjectManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/concurrent/volatilekeyword/SharedObjectManualTest.java
@@ -0,0 +1,71 @@
+package com.baeldung.concurrent.volatilekeyword;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import static junit.framework.Assert.assertEquals;
+
+public class SharedObjectManualTest {
+
+    private SharedObject sharedObject;
+    private int valueReadByThread2;
+    private int valueReadByThread3;
+
+    @Before
+    public void setUp() {
+        sharedObject = new SharedObject();
+    }
+
+    @Test
+    public void whenOneThreadWrites_thenVolatileReadsFromMainMemory() throws InterruptedException {
+        Thread writer = new Thread(() -> sharedObject.increamentCount());
+        writer.start();
+
+
+        Thread readerOne = new Thread(() -> {
+            try {
+                Thread.sleep(1000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            valueReadByThread2 = sharedObject.getCount();
+        });
+        readerOne.start();
+
+        Thread readerTwo = new Thread(() -> {
+            try {
+                Thread.sleep(1000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            valueReadByThread3 = sharedObject.getCount();
+        });
+        readerTwo.start();
+
+        assertEquals(1, valueReadByThread2);
+        assertEquals(1, valueReadByThread3);
+
+    }
+
+    @Test
+    public void whenTwoThreadWrites_thenVolatileReadsFromMainMemory() throws InterruptedException {
+        Thread writerOne = new Thread(() -> sharedObject.increamentCount());
+        writerOne.start();
+        Thread.sleep(100);
+
+        Thread writerTwo = new Thread(() -> sharedObject.increamentCount());
+        writerTwo.start();
+        Thread.sleep(100);
+
+        Thread readerOne = new Thread(() -> valueReadByThread2 = sharedObject.getCount());
+        readerOne.start();
+
+        Thread readerTwo = new Thread(() -> valueReadByThread3 = sharedObject.getCount());
+        readerTwo.start();
+
+        assertEquals(2, valueReadByThread2);
+        assertEquals(2, valueReadByThread3);
+
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentMapAggregateStatusManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentMapAggregateStatusManualTest.java
@@ -0,0 +1,78 @@
+package com.baeldung.java.concurrentmap;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class ConcurrentMapAggregateStatusManualTest {
+
+    private ExecutorService executorService;
+    private Map<String, Integer> concurrentMap;
+    private List<Integer> mapSizes;
+    private int MAX_SIZE = 100000;
+
+    @Before
+    public void init() {
+        executorService = Executors.newFixedThreadPool(2);
+        concurrentMap = new ConcurrentHashMap<>();
+        mapSizes = new ArrayList<>(MAX_SIZE);
+    }
+
+    @Test
+    public void givenConcurrentMap_whenSizeWithoutConcurrentUpdates_thenCorrect() throws InterruptedException {
+        Runnable collectMapSizes = () -> {
+            for (int i = 0; i < MAX_SIZE; i++) {
+                concurrentMap.put(String.valueOf(i), i);
+                mapSizes.add(concurrentMap.size());
+            }
+        };
+        Runnable retrieveMapData = () -> {
+            for (int i = 0; i < MAX_SIZE; i++) {
+                concurrentMap.get(String.valueOf(i));
+            }
+        };
+        executorService.execute(retrieveMapData);
+        executorService.execute(collectMapSizes);
+        executorService.shutdown();
+        executorService.awaitTermination(1, TimeUnit.MINUTES);
+
+        for (int i = 1; i <= MAX_SIZE; i++) {
+            assertEquals("map size should be consistently reliable", i, mapSizes.get(i - 1)
+                .intValue());
+        }
+        assertEquals(MAX_SIZE, concurrentMap.size());
+    }
+
+    @Test
+    public void givenConcurrentMap_whenUpdatingAndGetSize_thenError() throws InterruptedException {
+        Runnable collectMapSizes = () -> {
+            for (int i = 0; i < MAX_SIZE; i++) {
+                mapSizes.add(concurrentMap.size());
+            }
+        };
+        Runnable updateMapData = () -> {
+            for (int i = 0; i < MAX_SIZE; i++) {
+                concurrentMap.put(String.valueOf(i), i);
+            }
+        };
+        executorService.execute(updateMapData);
+        executorService.execute(collectMapSizes);
+        executorService.shutdown();
+        executorService.awaitTermination(1, TimeUnit.MINUTES);
+
+        assertNotEquals("map size collected with concurrent updates not reliable", MAX_SIZE, mapSizes.get(MAX_SIZE - 1)
+            .intValue());
+        assertEquals(MAX_SIZE, concurrentMap.size());
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentMapNullKeyValueManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentMapNullKeyValueManualTest.java
@@ -0,0 +1,160 @@
+package com.baeldung.java.concurrentmap;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+import static org.junit.Assert.assertNull;
+
+public class ConcurrentMapNullKeyValueManualTest {
+
+    ConcurrentMap<String, Object> concurrentMap;
+
+    @Before
+    public void setup() {
+        concurrentMap = new ConcurrentHashMap<>();
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenGetWithNullKey_thenThrowsNPE() {
+        concurrentMap.get(null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenGetOrDefaultWithNullKey_thenThrowsNPE() {
+        concurrentMap.getOrDefault(null, new Object());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenPutWithNullKey_thenThrowsNPE() {
+        concurrentMap.put(null, new Object());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenPutNullValue_thenThrowsNPE() {
+        concurrentMap.put("test", null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMapAndKeyAbsent_whenPutWithNullKey_thenThrowsNPE() {
+        concurrentMap.putIfAbsent(null, new Object());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMapAndMapWithNullKey_whenPutNullKeyMap_thenThrowsNPE() {
+        Map<String, Object> nullKeyMap = new HashMap<>();
+        nullKeyMap.put(null, new Object());
+        concurrentMap.putAll(nullKeyMap);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMapAndMapWithNullValue_whenPutNullValueMap_thenThrowsNPE() {
+        Map<String, Object> nullValueMap = new HashMap<>();
+        nullValueMap.put("test", null);
+        concurrentMap.putAll(nullValueMap);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenReplaceNullKeyWithValues_thenThrowsNPE() {
+        concurrentMap.replace(null, new Object(), new Object());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenReplaceWithNullNewValue_thenThrowsNPE() {
+        Object o = new Object();
+        concurrentMap.replace("test", o, null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenReplaceOldNullValue_thenThrowsNPE() {
+        Object o = new Object();
+        concurrentMap.replace("test", null, o);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenReplaceWithNullValue_thenThrowsNPE() {
+        concurrentMap.replace("test", null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenReplaceNullKey_thenThrowsNPE() {
+        concurrentMap.replace(null, "test");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenReplaceAllMappingNull_thenThrowsNPE() {
+        concurrentMap.put("test", new Object());
+        concurrentMap.replaceAll((s, o) -> null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenRemoveNullKey_thenThrowsNPE() {
+        concurrentMap.remove(null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenRemoveNullKeyWithValue_thenThrowsNPE() {
+        concurrentMap.remove(null, new Object());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenMergeNullKeyWithValue_thenThrowsNPE() {
+        concurrentMap.merge(null, new Object(), (o, o2) -> o2);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenMergeKeyWithNullValue_thenThrowsNPE() {
+        concurrentMap.put("test", new Object());
+        concurrentMap.merge("test", null, (o, o2) -> o2);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMapAndAssumeKeyAbsent_whenComputeWithNullKey_thenThrowsNPE() {
+        concurrentMap.computeIfAbsent(null, s -> s);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMapAndAssumeKeyPresent_whenComputeWithNullKey_thenThrowsNPE() {
+        concurrentMap.computeIfPresent(null, (s, o) -> o);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHashMap_whenComputeWithNullKey_thenThrowsNPE() {
+        concurrentMap.compute(null, (s, o) -> o);
+    }
+
+    @Test
+    public void givenConcurrentHashMap_whenMergeKeyRemappingNull_thenRemovesMapping() {
+        Object oldValue = new Object();
+        concurrentMap.put("test", oldValue);
+        concurrentMap.merge("test", new Object(), (o, o2) -> null);
+        assertNull(concurrentMap.get("test"));
+    }
+
+    @Test
+    public void givenConcurrentHashMapAndKeyAbsent_whenComputeWithKeyRemappingNull_thenRemainsAbsent() {
+        concurrentMap.computeIfPresent("test", (s, o) -> null);
+        assertNull(concurrentMap.get("test"));
+    }
+
+    @Test
+    public void givenKeyPresent_whenComputeIfPresentRemappingNull_thenMappingRemoved() {
+        Object oldValue = new Object();
+        concurrentMap.put("test", oldValue);
+        concurrentMap.computeIfPresent("test", (s, o) -> null);
+        assertNull(concurrentMap.get("test"));
+    }
+
+    @Test
+    public void givenKeyPresent_whenComputeRemappingNull_thenMappingRemoved() {
+        Object oldValue = new Object();
+        concurrentMap.put("test", oldValue);
+        concurrentMap.compute("test", (s, o) -> null);
+        assertNull(concurrentMap.get("test"));
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentMapPerformanceManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentMapPerformanceManualTest.java
@@ -0,0 +1,99 @@
+package com.baeldung.java.concurrentmap;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Hashtable;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.Test;
+
+public class ConcurrentMapPerformanceManualTest {
+
+    @Test
+    public void givenMaps_whenGetPut500KTimes_thenConcurrentMapFaster() throws Exception {
+        final Map<String, Object> hashtable = new Hashtable<>();
+        final Map<String, Object> synchronizedHashMap = Collections.synchronizedMap(new HashMap<>());
+        final Map<String, Object> concurrentHashMap = new ConcurrentHashMap<>();
+
+        final long hashtableAvgRuntime = timeElapseForGetPut(hashtable);
+        final long syncHashMapAvgRuntime = timeElapseForGetPut(synchronizedHashMap);
+        final long concurrentHashMapAvgRuntime = timeElapseForGetPut(concurrentHashMap);
+
+        System.out.println(String.format("Hashtable: %s, syncHashMap: %s, ConcurrentHashMap: %s", hashtableAvgRuntime, syncHashMapAvgRuntime, concurrentHashMapAvgRuntime));
+
+        assertTrue(hashtableAvgRuntime > concurrentHashMapAvgRuntime);
+        assertTrue(syncHashMapAvgRuntime > concurrentHashMapAvgRuntime);
+
+    }
+
+    private long timeElapseForGetPut(Map<String, Object> map) throws InterruptedException {
+        final ExecutorService executorService = Executors.newFixedThreadPool(4);
+        final long startTime = System.nanoTime();
+        for (int i = 0; i < 4; i++) {
+            executorService.execute(() -> {
+                for (int j = 0; j < 500_000; j++) {
+                    final int value = ThreadLocalRandom.current().nextInt(10000);
+                    final String key = String.valueOf(value);
+                    map.put(key, value);
+                    map.get(key);
+                }
+            });
+        }
+        executorService.shutdown();
+        executorService.awaitTermination(1, TimeUnit.MINUTES);
+        return (System.nanoTime() - startTime) / 500_000;
+    }
+
+    @Test
+    public void givenConcurrentMap_whenKeyWithSameHashCode_thenPerformanceDegrades() throws InterruptedException {
+        class SameHash {
+            @Override
+            public int hashCode() {
+                return 1;
+            }
+        }
+        final int executeTimes = 5000;
+
+        final Map<SameHash, Integer> mapOfSameHash = new ConcurrentHashMap<>();
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        final long sameHashStartTime = System.currentTimeMillis();
+        for (int i = 0; i < 2; i++) {
+            executorService.execute(() -> {
+                for (int j = 0; j < executeTimes; j++) {
+                    mapOfSameHash.put(new SameHash(), 1);
+                }
+            });
+        }
+        executorService.shutdown();
+        executorService.awaitTermination(5, TimeUnit.SECONDS);
+
+        final long mapOfSameHashDuration = System.currentTimeMillis() - sameHashStartTime;
+        final Map<Object, Integer> mapOfDefaultHash = new ConcurrentHashMap<>();
+        executorService = Executors.newFixedThreadPool(2);
+        final long defaultHashStartTime = System.currentTimeMillis();
+        for (int i = 0; i < 2; i++) {
+            executorService.execute(() -> {
+                for (int j = 0; j < executeTimes; j++) {
+                    mapOfDefaultHash.put(new Object(), 1);
+                }
+            });
+        }
+        executorService.shutdown();
+        executorService.awaitTermination(5, TimeUnit.SECONDS);
+
+        final long mapOfDefaultHashDuration = System.currentTimeMillis() - defaultHashStartTime;
+        assertEquals(executeTimes * 2, mapOfDefaultHash.size());
+        assertEquals(executeTimes * 2, mapOfSameHash.size());
+        System.out.println(String.format("same-hash: %s, default-hash: %s", mapOfSameHashDuration, mapOfDefaultHashDuration));
+        assertTrue("same hashCode() should greatly degrade performance", mapOfSameHashDuration > (mapOfDefaultHashDuration * 10));
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentNavigableMapManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurrentNavigableMapManualTest.java
@@ -0,0 +1,79 @@
+package com.baeldung.java.concurrentmap;
+
+import org.junit.Test;
+
+import java.util.Iterator;
+import java.util.NavigableMap;
+import java.util.TreeMap;
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ConcurrentNavigableMapManualTest {
+
+    @Test
+    public void givenSkipListMap_whenAccessInMultiThreads_thenOrderingStable() throws InterruptedException {
+        NavigableMap<Integer, String> skipListMap = new ConcurrentSkipListMap<>();
+
+        updateMapConcurrently(skipListMap, 4);
+
+        Iterator<Integer> skipListIter = skipListMap.keySet().iterator();
+        int previous = skipListIter.next();
+        while (skipListIter.hasNext()) {
+            int current = skipListIter.next();
+            assertTrue(previous < current);
+        }
+    }
+
+    private void updateMapConcurrently(NavigableMap<Integer, String> navigableMap, int concurrencyLevel) throws InterruptedException {
+        ExecutorService executorService = Executors.newFixedThreadPool(concurrencyLevel);
+        for (int i = 0; i < concurrencyLevel; i++) {
+            executorService.execute(() -> {
+                ThreadLocalRandom random = ThreadLocalRandom.current();
+                for (int j = 0; j < 10000; j++) {
+                    navigableMap.put(random.nextInt(), "test");
+                }
+            });
+        }
+        executorService.shutdown();
+        executorService.awaitTermination(1, TimeUnit.MINUTES);
+    }
+
+    @Test
+    public void givenSkipListMap_whenNavConcurrently_thenCountCorrect() throws InterruptedException {
+        NavigableMap<Integer, Integer> skipListMap = new ConcurrentSkipListMap<>();
+        int count = countMapElementByPollingFirstEntry(skipListMap, 10000, 4);
+        assertEquals(10000 * 4, count);
+    }
+
+    @Test
+    public void givenTreeMap_whenNavConcurrently_thenCountError() throws InterruptedException {
+        NavigableMap<Integer, Integer> treeMap = new TreeMap<>();
+        int count = countMapElementByPollingFirstEntry(treeMap, 10000, 4);
+        assertNotEquals(10000 * 4, count);
+    }
+
+    private int countMapElementByPollingFirstEntry(NavigableMap<Integer, Integer> navigableMap, int elementCount, int concurrencyLevel) throws InterruptedException {
+        for (int i = 0; i < elementCount * concurrencyLevel; i++) {
+            navigableMap.put(i, i);
+        }
+        AtomicInteger counter = new AtomicInteger(0);
+        ExecutorService executorService = Executors.newFixedThreadPool(concurrencyLevel);
+        for (int j = 0; j < concurrencyLevel; j++) {
+            executorService.execute(() -> {
+                for (int i = 0; i < elementCount; i++) {
+                    if (navigableMap.pollFirstEntry() != null) {
+                        counter.incrementAndGet();
+                    }
+                }
+            });
+        }
+        executorService.shutdown();
+        executorService.awaitTermination(1, TimeUnit.MINUTES);
+        return counter.get();
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurretMapMemoryConsistencyManualTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmap/ConcurretMapMemoryConsistencyManualTest.java
@@ -0,0 +1,72 @@
+package com.baeldung.java.concurrentmap;
+
+import org.junit.Test;
+
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.*;
+
+public class ConcurretMapMemoryConsistencyManualTest {
+
+    @Test
+    public void givenConcurrentMap_whenSumParallel_thenCorrect() throws Exception {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+        List<Integer> sumList = parallelSum100(map, 1000);
+        assertEquals(1, sumList.stream()
+            .distinct()
+            .count());
+        long wrongResultCount = sumList.stream()
+            .filter(num -> num != 100)
+            .count();
+        assertEquals(0, wrongResultCount);
+    }
+
+    @Test
+    public void givenHashtable_whenSumParallel_thenCorrect() throws Exception {
+        Map<String, Integer> map = new Hashtable<>();
+        List<Integer> sumList = parallelSum100(map, 1000);
+        assertEquals(1, sumList.stream()
+            .distinct()
+            .count());
+        long wrongResultCount = sumList.stream()
+            .filter(num -> num != 100)
+            .count();
+        assertEquals(0, wrongResultCount);
+    }
+
+    @Test
+    public void givenHashMap_whenSumParallel_thenError() throws Exception {
+        Map<String, Integer> map = new HashMap<>();
+        List<Integer> sumList = parallelSum100(map, 100);
+        assertNotEquals(1, sumList.stream()
+            .distinct()
+            .count());
+        long wrongResultCount = sumList.stream()
+            .filter(num -> num != 100)
+            .count();
+        assertTrue(wrongResultCount > 0);
+    }
+
+    private List<Integer> parallelSum100(Map<String, Integer> map, int executionTimes) throws InterruptedException {
+        List<Integer> sumList = new ArrayList<>(1000);
+        for (int i = 0; i < executionTimes; i++) {
+            map.put("test", 0);
+            ExecutorService executorService = Executors.newFixedThreadPool(4);
+            for (int j = 0; j < 10; j++) {
+                executorService.execute(() -> {
+                    for (int k = 0; k < 10; k++)
+                        map.computeIfPresent("test", (key, value) -> value + 1);
+                });
+            }
+            executorService.shutdown();
+            executorService.awaitTermination(5, TimeUnit.SECONDS);
+            sumList.add(map.get("test"));
+        }
+        return sumList;
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmodification/ConcurrentModificationUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/java/concurrentmodification/ConcurrentModificationUnitTest.java
@@ -0,0 +1,80 @@
+package com.baeldung.java.concurrentmodification;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.ConcurrentModificationException;
+import java.util.Iterator;
+import java.util.List;
+
+import static java.util.stream.Collectors.toList;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.util.Lists.newArrayList;
+
+public class ConcurrentModificationUnitTest {
+    @Test(expected = ConcurrentModificationException.class)
+    public void givenIterating_whenRemoving_thenThrowException() throws InterruptedException {
+
+        List<Integer> integers = newArrayList(1, 2, 3);
+
+        for (Integer integer : integers) {
+            integers.remove(1);
+        }
+    }
+
+    @Test
+    public void givenIterating_whenUsingIteratorRemove_thenNoError() throws InterruptedException {
+
+        List<Integer> integers = newArrayList(1, 2, 3);
+
+        for (Iterator<Integer> iterator = integers.iterator(); iterator.hasNext();) {
+            Integer integer = iterator.next();
+            if(integer == 2) {
+                iterator.remove();
+            }
+        }
+
+        assertThat(integers).containsExactly(1, 3);
+    }
+
+    @Test
+    public void givenIterating_whenUsingRemovalList_thenNoError() throws InterruptedException {
+
+        List<Integer> integers = newArrayList(1, 2, 3);
+        List<Integer> toRemove = newArrayList();
+
+        for (Integer integer : integers) {
+            if(integer == 2) {
+                toRemove.add(integer);
+            }
+        }
+        integers.removeAll(toRemove);
+
+        assertThat(integers).containsExactly(1, 3);
+    }
+
+    @Test
+    public void whenUsingRemoveIf_thenRemoveElements() throws InterruptedException {
+
+        Collection<Integer> integers = newArrayList(1, 2, 3);
+
+        integers.removeIf(i -> i == 2);
+
+        assertThat(integers).containsExactly(1, 3);
+    }
+
+    @Test
+    public void whenUsingStream_thenRemoveElements() {
+        Collection<Integer> integers = newArrayList(1, 2, 3);
+
+        List<String> collected = integers
+                .stream()
+                .filter(i -> i != 2)
+                .map(Object::toString)
+                .collect(toList());
+
+        assertThat(collected).containsExactly("1", "3");
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/java8/Java8ExecutorServiceIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/java8/Java8ExecutorServiceIntegrationTest.java
@@ -0,0 +1,162 @@
+package com.baeldung.java8;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.List;
+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.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class Java8ExecutorServiceIntegrationTest {
+
+    private Runnable runnableTask;
+    private Callable<String> callableTask;
+    private List<Callable<String>> callableTasks;
+
+    @Before
+    public void init() {
+
+        runnableTask = () -> {
+            try {
+                TimeUnit.MILLISECONDS.sleep(300);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        };
+
+        callableTask = () -> {
+            TimeUnit.MILLISECONDS.sleep(300);
+            return "Task's execution";
+        };
+
+        callableTasks = new ArrayList<>();
+        callableTasks.add(callableTask);
+        callableTasks.add(callableTask);
+        callableTasks.add(callableTask);
+    }
+
+    @Test
+    public void creationSubmittingTaskShuttingDown_whenShutDown_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+        executorService.submit(runnableTask);
+        executorService.submit(callableTask);
+        executorService.shutdown();
+
+        assertTrue(executorService.isShutdown());
+    }
+
+    @Test
+    public void creationSubmittingTasksShuttingDownNow_whenShutDownAfterAwating_thenCorrect() {
+
+        ExecutorService threadPoolExecutor = new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>());
+
+        for (int i = 0; i < 100; i++) {
+            threadPoolExecutor.submit(callableTask);
+        }
+
+        List<Runnable> notExecutedTasks = smartShutdown(threadPoolExecutor);
+
+        assertTrue(threadPoolExecutor.isShutdown());
+        assertFalse(notExecutedTasks.isEmpty());
+        assertTrue(notExecutedTasks.size() > 0 && notExecutedTasks.size() < 98);
+    }
+
+    private List<Runnable> smartShutdown(ExecutorService executorService) {
+
+        List<Runnable> notExecutedTasks = new ArrayList<>();
+        executorService.shutdown();
+        try {
+            if (!executorService.awaitTermination(800, TimeUnit.MILLISECONDS)) {
+                notExecutedTasks = executorService.shutdownNow();
+            }
+        } catch (InterruptedException e) {
+            notExecutedTasks = executorService.shutdownNow();
+        }
+        return notExecutedTasks;
+    }
+
+    @Test
+    public void submittingTasks_whenExecutedOneAndAll_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        String result = null;
+        List<Future<String>> futures = new ArrayList<>();
+        try {
+            result = executorService.invokeAny(callableTasks);
+            futures = executorService.invokeAll(callableTasks);
+        } catch (InterruptedException | ExecutionException e) {
+            e.printStackTrace();
+        }
+
+        assertEquals("Task's execution", result);
+        assertTrue(futures.size() == 3);
+    }
+
+    @Test
+    public void submittingTaskShuttingDown_whenGetExpectedResult_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        Future<String> future = executorService.submit(callableTask);
+        String result = null;
+        try {
+            result = future.get();
+            result = future.get(200, TimeUnit.MILLISECONDS);
+        } catch (InterruptedException | ExecutionException | TimeoutException e) {
+            e.printStackTrace();
+        }
+
+        executorService.shutdown();
+
+        assertEquals("Task's execution", result);
+    }
+
+    @Test
+    public void submittingTask_whenCanceled_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        Future<String> future = executorService.submit(callableTask);
+
+        boolean canceled = future.cancel(true);
+        boolean isCancelled = future.isCancelled();
+
+        executorService.shutdown();
+
+        assertTrue(canceled);
+        assertTrue(isCancelled);
+    }
+
+    @Test
+    public void submittingTaskScheduling_whenExecuted_thenCorrect() {
+
+        ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
+
+        Future<String> resultFuture = executorService.schedule(callableTask, 1, TimeUnit.SECONDS);
+        String result = null;
+        try {
+            result = resultFuture.get();
+        } catch (InterruptedException | ExecutionException e) {
+            e.printStackTrace();
+        }
+
+        executorService.shutdown();
+
+        assertEquals("Task's execution", result);
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/synchronousqueue/SynchronousQueueIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/synchronousqueue/SynchronousQueueIntegrationTest.java
@@ -0,0 +1,88 @@
+package com.baeldung.synchronousqueue;
+
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static junit.framework.TestCase.assertEquals;
+
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class SynchronousQueueIntegrationTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(SynchronousQueueIntegrationTest.class);
+
+
+    @Test
+    public void givenTwoThreads_whenWantToExchangeUsingLockGuardedVariable_thenItSucceed() throws InterruptedException {
+        //given
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        AtomicInteger sharedState = new AtomicInteger();
+        CountDownLatch countDownLatch = new CountDownLatch(1);
+
+        Runnable producer = () -> {
+            Integer producedElement = ThreadLocalRandom.current().nextInt();
+            LOG.debug("Saving an element: " + producedElement + " to the exchange point");
+            sharedState.set(producedElement);
+            countDownLatch.countDown();
+        };
+
+        Runnable consumer = () -> {
+            try {
+                countDownLatch.await();
+                Integer consumedElement = sharedState.get();
+                LOG.debug("consumed an element: " + consumedElement + " from the exchange point");
+            } catch (InterruptedException ex) {
+                ex.printStackTrace();
+            }
+        };
+
+        //when
+        executor.execute(producer);
+        executor.execute(consumer);
+
+        //then
+        executor.awaitTermination(500, TimeUnit.MILLISECONDS);
+        executor.shutdown();
+        assertEquals(countDownLatch.getCount(), 0);
+    }
+
+    @Test
+    public void givenTwoThreads_whenWantToExchangeUsingSynchronousQueue_thenItSucceed() throws InterruptedException {
+        //given
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        final SynchronousQueue<Integer> queue = new SynchronousQueue<>();
+
+        Runnable producer = () -> {
+            Integer producedElement = ThreadLocalRandom.current().nextInt();
+            try {
+                LOG.debug("Saving an element: " + producedElement + " to the exchange point");
+                queue.put(producedElement);
+            } catch (InterruptedException ex) {
+                ex.printStackTrace();
+            }
+        };
+
+        Runnable consumer = () -> {
+            try {
+                Integer consumedElement = queue.take();
+                LOG.debug("consumed an element: " + consumedElement + " from the exchange point");
+            } catch (InterruptedException ex) {
+                ex.printStackTrace();
+            }
+        };
+
+        //when
+        executor.execute(producer);
+        executor.execute(consumer);
+
+        //then
+        executor.awaitTermination(500, TimeUnit.MILLISECONDS);
+        executor.shutdown();
+        assertEquals(queue.size(), 0);
+    }
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/threadlocal/ThreadLocalIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/threadlocal/ThreadLocalIntegrationTest.java
@@ -0,0 +1,35 @@
+package com.baeldung.threadlocal;
+
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutionException;
+
+import static org.junit.Assert.assertEquals;
+
+public class ThreadLocalIntegrationTest {
+    @Test
+    public void givenThreadThatStoresContextInAMap_whenStartThread_thenShouldSetContextForBothUsers() throws ExecutionException, InterruptedException {
+        //when
+        SharedMapWithUserContext firstUser = new SharedMapWithUserContext(1);
+        SharedMapWithUserContext secondUser = new SharedMapWithUserContext(2);
+        new Thread(firstUser).start();
+        new Thread(secondUser).start();
+
+        Thread.sleep(3000);
+        //then
+        assertEquals(SharedMapWithUserContext.userContextPerUserId.size(), 2);
+    }
+
+    @Test
+    public void givenThreadThatStoresContextInThreadLocal_whenStartThread_thenShouldStoreContextInThreadLocal() throws ExecutionException, InterruptedException {
+        //when
+        ThreadLocalWithUserContext firstUser = new ThreadLocalWithUserContext(1);
+        ThreadLocalWithUserContext secondUser = new ThreadLocalWithUserContext(2);
+        new Thread(firstUser).start();
+        new Thread(secondUser).start();
+
+        Thread.sleep(3000);
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/threadpool/CoreThreadPoolIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/threadpool/CoreThreadPoolIntegrationTest.java
@@ -0,0 +1,147 @@
+package com.baeldung.threadpool;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+
+public class CoreThreadPoolIntegrationTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(CoreThreadPoolIntegrationTest.class);
+
+    @Test(timeout = 1000)
+    public void whenCallingExecuteWithRunnable_thenRunnableIsExecuted() throws InterruptedException {
+
+        CountDownLatch lock = new CountDownLatch(1);
+
+        Executor executor = Executors.newSingleThreadExecutor();
+        executor.execute(() -> {
+            LOG.debug("Hello World");
+            lock.countDown();
+        });
+
+        lock.await(1000, TimeUnit.MILLISECONDS);
+    }
+
+    @Test
+    public void whenUsingExecutorServiceAndFuture_thenCanWaitOnFutureResult() throws InterruptedException, ExecutionException {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+        Future<String> future = executorService.submit(() -> "Hello World");
+        String result = future.get();
+
+        assertEquals("Hello World", result);
+
+    }
+
+    @Test
+    public void whenUsingFixedThreadPool_thenCoreAndMaximumThreadSizeAreTheSame() {
+
+        ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(2);
+        executor.submit(() -> {
+            Thread.sleep(1000);
+            return null;
+        });
+        executor.submit(() -> {
+            Thread.sleep(1000);
+            return null;
+        });
+        executor.submit(() -> {
+            Thread.sleep(1000);
+            return null;
+        });
+
+        assertEquals(2, executor.getPoolSize());
+        assertEquals(1, executor.getQueue().size());
+
+    }
+
+    @Test
+    public void whenUsingCachedThreadPool_thenPoolSizeGrowsUnbounded() {
+        ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newCachedThreadPool();
+        executor.submit(() -> {
+            Thread.sleep(1000);
+            return null;
+        });
+        executor.submit(() -> {
+            Thread.sleep(1000);
+            return null;
+        });
+        executor.submit(() -> {
+            Thread.sleep(1000);
+            return null;
+        });
+
+        assertEquals(3, executor.getPoolSize());
+        assertEquals(0, executor.getQueue().size());
+
+    }
+
+    @Test(timeout = 1000)
+    public void whenUsingSingleThreadPool_thenTasksExecuteSequentially() throws InterruptedException {
+
+        CountDownLatch lock = new CountDownLatch(2);
+        AtomicInteger counter = new AtomicInteger();
+
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+        executor.submit(() -> {
+            counter.set(1);
+            lock.countDown();
+        });
+        executor.submit(() -> {
+            counter.compareAndSet(1, 2);
+            lock.countDown();
+        });
+
+        lock.await(1000, TimeUnit.MILLISECONDS);
+        assertEquals(2, counter.get());
+
+    }
+
+    @Test(timeout = 1000)
+    public void whenSchedulingTask_thenTaskExecutesWithinGivenPeriod() throws InterruptedException {
+
+        CountDownLatch lock = new CountDownLatch(1);
+
+        ScheduledExecutorService executor = Executors.newScheduledThreadPool(5);
+        executor.schedule(() -> {
+            LOG.debug("Hello World");
+            lock.countDown();
+        }, 500, TimeUnit.MILLISECONDS);
+
+        lock.await(1000, TimeUnit.MILLISECONDS);
+
+    }
+
+    @Test(timeout = 1000)
+    public void whenSchedulingTaskWithFixedPeriod_thenTaskExecutesMultipleTimes() throws InterruptedException {
+
+        CountDownLatch lock = new CountDownLatch(3);
+
+        ScheduledExecutorService executor = Executors.newScheduledThreadPool(5);
+        ScheduledFuture<?> future = executor.scheduleAtFixedRate(() -> {
+            LOG.debug("Hello World");
+            lock.countDown();
+        }, 500, 100, TimeUnit.MILLISECONDS);
+
+        lock.await();
+        future.cancel(true);
+
+    }
+
+    @Test
+    public void whenUsingForkJoinPool_thenSumOfTreeElementsIsCalculatedCorrectly() {
+
+        TreeNode tree = new TreeNode(5, new TreeNode(3), new TreeNode(2, new TreeNode(2), new TreeNode(8)));
+
+        ForkJoinPool forkJoinPool = ForkJoinPool.commonPool();
+        int sum = forkJoinPool.invoke(new CountingTask(tree));
+
+        assertEquals(20, sum);
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/threadpool/GuavaThreadPoolIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/threadpool/GuavaThreadPoolIntegrationTest.java
@@ -0,0 +1,54 @@
+package com.baeldung.threadpool;
+
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.stream.Collectors;
+
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.common.util.concurrent.MoreExecutors;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class GuavaThreadPoolIntegrationTest {
+
+    @Test
+    public void whenExecutingTaskWithDirectExecutor_thenTheTaskIsExecutedInTheCurrentThread() {
+
+        Executor executor = MoreExecutors.directExecutor();
+
+        AtomicBoolean executed = new AtomicBoolean();
+
+        executor.execute(() -> {
+            try {
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            executed.set(true);
+        });
+
+        assertTrue(executed.get());
+    }
+
+    @Test
+    public void whenJoiningFuturesWithAllAsList_thenCombinedFutureCompletesAfterAllFuturesComplete() throws ExecutionException, InterruptedException {
+
+        ExecutorService executorService = Executors.newCachedThreadPool();
+        ListeningExecutorService listeningExecutorService = MoreExecutors.listeningDecorator(executorService);
+
+        ListenableFuture<String> future1 = listeningExecutorService.submit(() -> "Hello");
+        ListenableFuture<String> future2 = listeningExecutorService.submit(() -> "World");
+
+        String greeting = Futures.allAsList(future1, future2).get().stream().collect(Collectors.joining(" "));
+        assertEquals("Hello World", greeting);
+
+    }
+
+}
--- a/core-java-concurrency/src/test/java/com/baeldung/transferqueue/TransferQueueIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/transferqueue/TransferQueueIntegrationTest.java
@@ -0,0 +1,74 @@
+package com.baeldung.transferqueue;
+
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+
+import java.util.concurrent.*;
+
+import static junit.framework.TestCase.assertEquals;
+
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class TransferQueueIntegrationTest {
+
+    @Test
+    public void whenMultipleConsumersAndProducers_thenProcessAllMessages() throws InterruptedException {
+        //given
+        TransferQueue<String> transferQueue = new LinkedTransferQueue<>();
+        ExecutorService exService = Executors.newFixedThreadPool(3);
+        Producer producer1 = new Producer(transferQueue, "1", 3);
+        Producer producer2 = new Producer(transferQueue, "2", 3);
+        Consumer consumer1 = new Consumer(transferQueue, "1", 3);
+        Consumer consumer2 = new Consumer(transferQueue, "2", 3);
+
+        //when
+        exService.execute(producer1);
+        exService.execute(producer2);
+        exService.execute(consumer1);
+        exService.execute(consumer2);
+
+        //then
+        exService.awaitTermination(5000, TimeUnit.MILLISECONDS);
+        exService.shutdown();
+
+        assertEquals(producer1.numberOfProducedMessages.intValue(), 3);
+        assertEquals(producer2.numberOfProducedMessages.intValue(), 3);
+    }
+
+    @Test
+    public void whenUseOneConsumerAndOneProducer_thenShouldProcessAllMessages() throws InterruptedException {
+        //given
+        TransferQueue<String> transferQueue = new LinkedTransferQueue<>();
+        ExecutorService exService = Executors.newFixedThreadPool(2);
+        Producer producer = new Producer(transferQueue, "1", 3);
+        Consumer consumer = new Consumer(transferQueue, "1", 3);
+
+        //when
+        exService.execute(producer);
+        exService.execute(consumer);
+
+        //then
+        exService.awaitTermination(5000, TimeUnit.MILLISECONDS);
+        exService.shutdown();
+
+        assertEquals(producer.numberOfProducedMessages.intValue(), 3);
+        assertEquals(consumer.numberOfConsumedMessages.intValue(), 3);
+    }
+
+    @Test
+    public void whenUseOneProducerAndNoConsumers_thenShouldFailWithTimeout() throws InterruptedException {
+        //given
+        TransferQueue<String> transferQueue = new LinkedTransferQueue<>();
+        ExecutorService exService = Executors.newFixedThreadPool(2);
+        Producer producer = new Producer(transferQueue, "1", 3);
+
+        //when
+        exService.execute(producer);
+
+        //then
+        exService.awaitTermination(5000, TimeUnit.MILLISECONDS);
+        exService.shutdown();
+
+        assertEquals(producer.numberOfProducedMessages.intValue(), 0);
+    }
+}
--- a/core-java-concurrency/src/test/java/org/baeldung/java/streams/ThreadPoolInParallelStreamIntegrationTest.java
+++ b/core-java-concurrency/src/test/java/org/baeldung/java/streams/ThreadPoolInParallelStreamIntegrationTest.java
@@ -0,0 +1,38 @@
+package org.baeldung.java.streams;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ForkJoinPool;
+import java.util.stream.Collectors;
+import java.util.stream.LongStream;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ThreadPoolInParallelStreamIntegrationTest {
+
+    @Test
+    public void giveRangeOfLongs_whenSummedInParallel_shouldBeEqualToExpectedTotal() throws InterruptedException, ExecutionException {
+        long firstNum = 1;
+        long lastNum = 1_000_000;
+
+        List<Long> aList = LongStream.rangeClosed(firstNum, lastNum).boxed().collect(Collectors.toList());
+
+        ForkJoinPool customThreadPool = new ForkJoinPool(4);
+        long actualTotal = customThreadPool.submit(() -> aList.parallelStream().reduce(0L, Long::sum)).get();
+
+        assertEquals((lastNum + firstNum) * lastNum / 2, actualTotal);
+    }
+
+    @Test
+    public void givenList_whenCallingParallelStream_shouldBeParallelStream() {
+        List<Long> aList = new ArrayList<>();
+        Stream<Long> parallelStream = aList.parallelStream();
+
+        assertTrue(parallelStream.isParallel());
+    }
+}
--- a/core-java-concurrency/src/test/resources/.gitignore
+++ b/core-java-concurrency/src/test/resources/.gitignore
@@ -0,0 +1,13 @@
+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear