Adding code for article tracked under BAEL-3573. (#8999)

Co-authored-by: CHANDRAKANT Kumar <kumar.chandrakant@soprabanking.com>

core-java-modules/core-java-concurrency-testing/.gitignore

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+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+*.txt
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-modules/core-java-concurrency-testing/README.md

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+=========
+
+## Core Java Concurrency Testing Examples
+
+### Relevant Articles: 
+- [Testing Multi-Threaded Code in Java](https://www.baeldung.com/java-testing-multithreaded)
+

core-java-modules/core-java-concurrency-testing/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<artifactId>core-java-concurrency-testing</artifactId>
+	<version>0.1.0-SNAPSHOT</version>
+	<name>core-java-concurrency-testing</name>
+	<packaging>jar</packaging>
+
+	<parent>
+		<groupId>com.baeldung</groupId>
+		<artifactId>parent-java</artifactId>
+		<version>0.0.1-SNAPSHOT</version>
+		<relativePath>../../parent-java</relativePath>
+	</parent>
+	
+	<dependencies>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.13</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>com.googlecode.thread-weaver</groupId>
+			<artifactId>threadweaver</artifactId>
+			<version>0.2</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>com.google.code.tempus-fugit</groupId>
+			<artifactId>tempus-fugit</artifactId>
+			<version>1.1</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>com.googlecode.multithreadedtc</groupId>
+			<artifactId>multithreadedtc</artifactId>
+			<version>1.01</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.openjdk.jcstress</groupId>
+			<artifactId>jcstress-core</artifactId>
+			<version>0.5</version>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>3.1</version>
+				<configuration>
+					<compilerVersion>${javac.target}</compilerVersion>
+					<source>${javac.target}</source>
+					<target>${javac.target}</target>
+				</configuration>
+			</plugin>
+
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-shade-plugin</artifactId>
+				<version>2.2</version>
+				<executions>
+					<execution>
+						<id>main</id>
+						<phase>package</phase>
+						<goals>
+							<goal>shade</goal>
+						</goals>
+						<configuration>
+							<finalName>jcstress</finalName>
+							<transformers>
+								<transformer
+									implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+									<mainClass>org.openjdk.jcstress.Main</mainClass>
+								</transformer>
+								<transformer
+									implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
+									<resource>META-INF/TestList</resource>
+								</transformer>
+							</transformers>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

core-java-modules/core-java-concurrency-testing/src/main/java/com/baeldung/concurrent/MyCounter.java

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+package com.baeldung.concurrent;
+
+public class MyCounter {
+
+    private int count;
+
+    public void increment() {
+        int temp = count;
+        count = temp + 1;
+    }
+
+    public synchronized void incrementWithWait() throws InterruptedException {
+        int temp = count;
+        wait(100);
+        count = temp + 1;
+    }
+
+    public int getCount() {
+        return count;
+    }
+
+}

core-java-modules/core-java-concurrency-testing/src/main/resources/logback.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <logger name="org.springframework" level="WARN" />
+    <logger name="org.springframework.transaction" level="WARN" />
+
+    <!-- in order to debug some marshalling issues, this needs to be TRACE -->
+    <logger name="org.springframework.web.servlet.mvc" level="WARN" />
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

core-java-modules/core-java-concurrency-testing/src/test/java/com/baeldung/concurrent/MyCounterJCStressUnitTest.java

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+package com.baeldung.concurrent;
+
+import static org.openjdk.jcstress.annotations.Expect.ACCEPTABLE;
+import static org.openjdk.jcstress.annotations.Expect.ACCEPTABLE_INTERESTING;
+
+import org.openjdk.jcstress.annotations.Actor;
+import org.openjdk.jcstress.annotations.Arbiter;
+import org.openjdk.jcstress.annotations.JCStressTest;
+import org.openjdk.jcstress.annotations.Outcome;
+import org.openjdk.jcstress.annotations.State;
+import org.openjdk.jcstress.infra.results.I_Result;
+
+@JCStressTest
+@Outcome(id = "1", expect = ACCEPTABLE_INTERESTING, desc = "One update lost.")
+@Outcome(id = "2", expect = ACCEPTABLE, desc = "Both updates.")
+@State
+public class MyCounterJCStressUnitTest {
+
+    private MyCounter counter;
+
+    @Actor
+    public void actor1() {
+        counter.increment();
+    }
+
+    @Actor
+    public void actor2() {
+        counter.increment();
+    }
+
+    @Arbiter
+    public void arbiter(I_Result r) {
+        r.r1 = counter.getCount();
+    }
+
+}

core-java-modules/core-java-concurrency-testing/src/test/java/com/baeldung/concurrent/MyCounterMultithreadedTCUnitTest.java

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+package com.baeldung.concurrent;
+
+import org.junit.Test;
+
+import edu.umd.cs.mtc.MultithreadedTestCase;
+import edu.umd.cs.mtc.TestFramework;
+
+public class MyCounterMultithreadedTCUnitTest extends MultithreadedTestCase {
+
+    private MyCounter counter;
+
+    @Override
+    public void initialize() {
+        counter = new MyCounter();
+    }
+
+    public void thread1() throws InterruptedException {
+        counter.increment();
+    }
+
+    public void thread2() throws InterruptedException {
+        counter.increment();
+    }
+
+    @SuppressWarnings("deprecation")
+    @Override
+    public void finish() {
+        assertEquals(2, counter.getCount());
+    }
+
+    @Test
+    public void testCounter() throws Throwable {
+        TestFramework.runManyTimes(new MyCounterMultithreadedTCUnitTest(), 1000);
+    }
+}

core-java-modules/core-java-concurrency-testing/src/test/java/com/baeldung/concurrent/MyCounterSimpleUnitTest.java

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+package com.baeldung.concurrent;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import org.junit.Test;
+
+public class MyCounterSimpleUnitTest {
+
+    @Test
+    public void testCounter() {
+        MyCounter counter = new MyCounter();
+        for (int i = 0; i < 500; i++)
+            counter.increment();
+        assertEquals(500, counter.getCount());
+    }
+
+    // @Test
+    public void testCounterWithConcurrency() throws InterruptedException {
+        int numberOfThreads = 100;
+        ExecutorService service = Executors.newFixedThreadPool(10);
+        CountDownLatch latch = new CountDownLatch(numberOfThreads);
+        MyCounter counter = new MyCounter();
+        for (int i = 0; i < numberOfThreads; i++) {
+            service.execute(() -> {
+                counter.increment();
+                latch.countDown();
+            });
+        }
+        latch.await();
+        assertEquals(numberOfThreads, counter.getCount());
+    }
+
+    // @Test
+    public void testSummationWithConcurrencyAndWait() throws InterruptedException {
+        int numberOfThreads = 2;
+        ExecutorService service = Executors.newFixedThreadPool(10);
+        CountDownLatch latch = new CountDownLatch(numberOfThreads);
+        MyCounter counter = new MyCounter();
+        for (int i = 0; i < numberOfThreads; i++) {
+            service.submit(() -> {
+                try {
+                    counter.incrementWithWait();
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+                latch.countDown();
+            });
+        }
+        latch.await();
+        assertEquals(numberOfThreads, counter.getCount());
+    }
+
+}

core-java-modules/core-java-concurrency-testing/src/test/java/com/baeldung/concurrent/MyCounterTempusFugitUnitTest.java

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+package com.baeldung.concurrent;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.AfterClass;
+import org.junit.Rule;
+import org.junit.Test;
+
+import com.google.code.tempusfugit.concurrency.ConcurrentRule;
+import com.google.code.tempusfugit.concurrency.RepeatingRule;
+import com.google.code.tempusfugit.concurrency.annotations.Concurrent;
+import com.google.code.tempusfugit.concurrency.annotations.Repeating;
+
+public class MyCounterTempusFugitUnitTest {
+
+    @Rule
+    public ConcurrentRule concurrently = new ConcurrentRule();
+    @Rule
+    public RepeatingRule rule = new RepeatingRule();
+
+    private static MyCounter counter = new MyCounter();
+
+    @Test
+    @Concurrent(count = 2)
+    @Repeating(repetition = 10)
+    public void runsMultipleTimes() {
+        counter.increment();
+    }
+
+    @AfterClass
+    public static void annotatedTestRunsMultipleTimes() throws InterruptedException {
+        assertEquals(counter.getCount(), 20);
+    }
+
+}

core-java-modules/core-java-concurrency-testing/src/test/java/com/baeldung/concurrent/MyCounterThreadWeaverUnitTest.java

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+package com.baeldung.concurrent;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.google.testing.threadtester.AnnotatedTestRunner;
+import com.google.testing.threadtester.ThreadedAfter;
+import com.google.testing.threadtester.ThreadedBefore;
+import com.google.testing.threadtester.ThreadedMain;
+import com.google.testing.threadtester.ThreadedSecondary;
+
+public class MyCounterThreadWeaverUnitTest {
+
+    private MyCounter counter;
+
+    @ThreadedBefore
+    public void before() {
+        counter = new MyCounter();
+    }
+
+    @ThreadedMain
+    public void mainThread() {
+        counter.increment();
+    }
+
+    @ThreadedSecondary
+    public void secondThread() {
+        counter.increment();
+    }
+
+    @ThreadedAfter
+    public void after() {
+        assertEquals(2, counter.getCount());
+    }
+
+    @Test
+    public void testCounter() {
+        new AnnotatedTestRunner().runTests(this.getClass(), MyCounter.class);
+    }
+
+}

core-java-modules/core-java-concurrency-testing/src/test/resources/.gitignore

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+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear