Merge branch 'master' into feature/ktln-43/working-with-lists-in-kotlin

algorithms-miscellaneous-5/README.md

@@ -15,9 +15,5 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Maximum Subarray Problem](https://www.baeldung.com/java-maximum-subarray)
 - [How to Merge Two Sorted Arrays](https://www.baeldung.com/java-merge-sorted-arrays)
 - [Median of Stream of Integers using Heap](https://www.baeldung.com/java-stream-integers-median-using-heap)
-- [Kruskal’s Algorithm for Spanning Trees](https://www.baeldung.com/java-spanning-trees-kruskal)
+- More articles: [[<-- prev]](/../algorithms-miscellaneous-4) [[next -->]](/../algorithms-miscellaneous-6)
-- [Balanced Brackets Algorithm in Java](https://www.baeldung.com/java-balanced-brackets-algorithm)
+
-- [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
-- [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
-- [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
-- More articles: [[<-- prev]](/../algorithms-miscellaneous-4)

algorithms-miscellaneous-5/pom.xml

@@ -25,12 +25,6 @@
             <artifactId>commons-math3</artifactId>
             <version>${commons-math3.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
         <dependency>
             <groupId>pl.allegro.finance</groupId>
             <artifactId>tradukisto</artifactId>

algorithms-miscellaneous-6/README.md

@@ -2,3 +2,9 @@
 
 - [Boruvka’s Algorithm for Minimum Spanning Trees](https://www.baeldung.com/java-boruvka-algorithm)
 - [Gradient Descent in Java](https://www.baeldung.com/java-gradient-descent)
+- [Kruskal’s Algorithm for Spanning Trees](https://www.baeldung.com/java-spanning-trees-kruskal)
+- [Balanced Brackets Algorithm in Java](https://www.baeldung.com/java-balanced-brackets-algorithm)
+- [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
+- [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
+- [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
+- More articles: [[<-- prev]](/../algorithms-miscellaneous-5)

algorithms-miscellaneous-6/pom.xml

@@ -18,10 +18,35 @@
             <artifactId>guava</artifactId>
             <version>${guava.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-commons</artifactId>
+            <version>${junit.platform.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${org.assertj.core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
     </dependencies>
     
     <properties>
         <guava.version>28.1-jre</guava.version>
+        <org.assertj.core.version>3.9.0</org.assertj.core.version>
+        <junit.platform.version>1.6.0</junit.platform.version>
+        <commons-math3.version>3.6.1</commons-math3.version>
     </properties>
 
 </project>

apache-cxf/README.md

@@ -3,7 +3,7 @@
 This module contains articles about Apache CXF
 
 ## Relevant Articles:
-- [Introduction to Apache CXF Aegis Data Binding](https://www.baeldung.com/aegis-data-binding-in-apache-cxf)
+
 - [Apache CXF Support for RESTful Web Services](https://www.baeldung.com/apache-cxf-rest-api)
 - [A Guide to Apache CXF with Spring](https://www.baeldung.com/apache-cxf-with-spring)
 - [Introduction to Apache CXF](https://www.baeldung.com/introduction-to-apache-cxf)

apache-cxf/cxf-aegis/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Introduction to Apache CXF Aegis Data Binding](https://www.baeldung.com/aegis-data-binding-in-apache-cxf)

apache-shiro/pom.xml

@@ -10,9 +10,9 @@
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-boot-1</artifactId>
+        <artifactId>parent-boot-2</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-boot-1</relativePath>
+        <relativePath>../parent-boot-2</relativePath>
     </parent>
 
     <dependencies>

apache-shiro/src/main/java/com/baeldung/Main.java

@@ -1,11 +1,14 @@
 package com.baeldung;
 
 import org.apache.shiro.SecurityUtils;
-import org.apache.shiro.authc.*;
+import org.apache.shiro.authc.AuthenticationException;
+import org.apache.shiro.authc.IncorrectCredentialsException;
+import org.apache.shiro.authc.LockedAccountException;
+import org.apache.shiro.authc.UnknownAccountException;
+import org.apache.shiro.authc.UsernamePasswordToken;
 import org.apache.shiro.mgt.DefaultSecurityManager;
 import org.apache.shiro.mgt.SecurityManager;
 import org.apache.shiro.realm.Realm;
-import org.apache.shiro.realm.text.IniRealm;
 import org.apache.shiro.session.Session;
 import org.apache.shiro.subject.Subject;
 import org.slf4j.Logger;

apache-shiro/src/main/java/com/baeldung/MyCustomRealm.java

@@ -1,16 +1,24 @@
 package com.baeldung;
 
-import org.apache.shiro.authc.*;
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.shiro.authc.AuthenticationException;
+import org.apache.shiro.authc.AuthenticationInfo;
+import org.apache.shiro.authc.AuthenticationToken;
+import org.apache.shiro.authc.SimpleAuthenticationInfo;
+import org.apache.shiro.authc.UnknownAccountException;
+import org.apache.shiro.authc.UsernamePasswordToken;
 import org.apache.shiro.authz.AuthorizationInfo;
 import org.apache.shiro.authz.SimpleAuthorizationInfo;
 import org.apache.shiro.realm.jdbc.JdbcRealm;
 import org.apache.shiro.subject.PrincipalCollection;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.sql.Connection;
-import java.sql.SQLException;
-import java.util.*;
 
 public class MyCustomRealm extends JdbcRealm {
 

apache-shiro/src/main/java/com/baeldung/shiro/permissions/custom/Main.java

@@ -1,14 +1,15 @@
 package com.baeldung.shiro.permissions.custom;
 
-import com.baeldung.MyCustomRealm;
 import org.apache.shiro.SecurityUtils;
-import org.apache.shiro.authc.*;
+import org.apache.shiro.authc.AuthenticationException;
+import org.apache.shiro.authc.IncorrectCredentialsException;
+import org.apache.shiro.authc.LockedAccountException;
+import org.apache.shiro.authc.UnknownAccountException;
+import org.apache.shiro.authc.UsernamePasswordToken;
 import org.apache.shiro.config.Ini;
 import org.apache.shiro.mgt.DefaultSecurityManager;
 import org.apache.shiro.mgt.SecurityManager;
-import org.apache.shiro.realm.Realm;
 import org.apache.shiro.realm.text.IniRealm;
-import org.apache.shiro.session.Session;
 import org.apache.shiro.subject.Subject;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

atomikos/README.md

@@ -1,7 +1,6 @@
 ## Atomikos
-
 This module contains articles about Atomikos
 
 ### Relevant Articles: 
 
-- [Guide Transactions Using Atomikos]()
+- [A Guide to Atomikos](https://www.baeldung.com/java-atomikos)

aws-app-sync/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [AWS AppSync With Spring Boot](https://www.baeldung.com/aws-appsync-spring)

aws-app-sync/pom.xml

@@ -0,0 +1,56 @@
+<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.2.6.RELEASE</version>
+        <relativePath/> <!-- lookup parent from repository -->
+    </parent>
+
+    <groupId>com.baeldung</groupId>
+    <artifactId>aws-app-sync</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>aws-app-sync</name>
+
+    <description>Spring Boot using AWS App Sync</description>
+
+    <properties>
+        <java.version>1.8</java.version>
+    </properties>
+
+    <dependencies>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.junit.vintage</groupId>
+                    <artifactId>junit-vintage-engine</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-webflux</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

aws-app-sync/src/main/java/com/baeldung/awsappsync/AppSyncClientHelper.java

@@ -0,0 +1,32 @@
+package com.baeldung.awsappsync;
+
+import org.springframework.http.HttpMethod;
+import org.springframework.http.MediaType;
+import org.springframework.web.reactive.function.BodyInserters;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+
+public class AppSyncClientHelper {
+
+    static String apiUrl = "<INSERT API URL HERE>";
+    static String apiKey = "<INSERT API KEY HERE>";
+    static String API_KEY_HEADER = "x-api-key";
+
+    public static WebClient.ResponseSpec getResponseBodySpec(Map<String, Object> requestBody) {
+        return WebClient
+                .builder()
+                .baseUrl(apiUrl)
+                .defaultHeader(API_KEY_HEADER, apiKey)
+                .defaultHeader("Content-Type", "application/json")
+                .build()
+                .method(HttpMethod.POST)
+                .uri("/graphql")
+                .body(BodyInserters.fromValue(requestBody))
+                .accept(MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML)
+                .acceptCharset(StandardCharsets.UTF_8)
+                .retrieve();
+    }
+
+}

aws-app-sync/src/main/java/com/baeldung/awsappsync/AwsAppSyncApplication.java

@@ -0,0 +1,13 @@
+package com.baeldung.awsappsync;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class AwsAppSyncApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(AwsAppSyncApplication.class, args);
+    }
+
+}

aws-app-sync/src/test/java/com/baeldung/awsappsync/AwsAppSyncApplicationTests.java

@@ -0,0 +1,74 @@
+package com.baeldung.awsappsync;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@SpringBootTest
+@Disabled
+class AwsAppSyncApplicationTests {
+
+    @Test
+    void givenGraphQuery_whenListEvents_thenReturnAllEvents() {
+
+        Map<String, Object> requestBody = new HashMap<>();
+        requestBody.put("query", "query ListEvents {"
+                + "  listEvents {"
+                + "    items {"
+                + "      id"
+                + "      name"
+                + "      where"
+                + "      when"
+                + "      description"
+                + "    }"
+                + "  }"
+                + "}");
+        requestBody.put("variables", "");
+        requestBody.put("operationName", "ListEvents");
+
+        String bodyString = AppSyncClientHelper.getResponseBodySpec(requestBody)
+                .bodyToMono(String.class).block();
+
+        assertNotNull(bodyString);
+        assertTrue(bodyString.contains("My First Event"));
+        assertTrue(bodyString.contains("where"));
+        assertTrue(bodyString.contains("when"));
+    }
+
+    @Test
+    void givenGraphAdd_whenMutation_thenReturnIdNameDesc() {
+
+        String queryString = "mutation add {"
+                + "    createEvent("
+                + "        name:\"My added GraphQL event\""
+                + "        where:\"Day 2\""
+                + "        when:\"Saturday night\""
+                + "        description:\"Studying GraphQL\""
+                + "    ){"
+                + "        id"
+                + "        name"
+                + "        description"
+                + "    }"
+                + "}";
+
+        Map<String, Object> requestBody = new HashMap<>();
+        requestBody.put("query", queryString);
+        requestBody.put("variables", "");
+        requestBody.put("operationName", "add");
+
+        WebClient.ResponseSpec response = AppSyncClientHelper.getResponseBodySpec(requestBody);
+
+        String bodyString = response.bodyToMono(String.class).block();
+
+        assertNotNull(bodyString);
+        assertTrue(bodyString.contains("My added GraphQL event"));
+        assertFalse(bodyString.contains("where"));
+        assertFalse(bodyString.contains("when"));
+    }
+}

bazel/bazelapp/README.md

@@ -1,3 +0,0 @@
-### Relevant Articles:
-
-- [Building Java Applications with Bazel](https://www.baeldung.com/bazel-build-tool)

cas/cas-secured-app/pom.xml

@@ -16,10 +16,6 @@
         <relativePath>../../parent-boot-2</relativePath>
     </parent>
 
-    <properties>
-        <spring-boot.version>2.2.6.RELEASE</spring-boot.version>
-    </properties>
-
     <dependencies>
         <dependency>
             <groupId>org.springframework.boot</groupId>

core-groovy-2/README.md

@@ -13,4 +13,5 @@ This module contains articles about core Groovy concepts
 - [Metaprogramming in Groovy](https://www.baeldung.com/groovy-metaprogramming)
 - [A Quick Guide to Working with Web Services in Groovy](https://www.baeldung.com/groovy-web-services)
 - [Categories in Groovy](https://www.baeldung.com/groovy-categories)
+- [How to Determine the Data Type in Groovy](https://www.baeldung.com/groovy-determine-data-type)
 - [[<-- Prev]](/core-groovy)

core-groovy/README.md

@@ -12,4 +12,5 @@ This module contains articles about core Groovy concepts
 - [Closures in Groovy](https://www.baeldung.com/groovy-closures)
 - [Converting a String to a Date in Groovy](https://www.baeldung.com/groovy-string-to-date)
 - [Guide to I/O in Groovy](https://www.baeldung.com/groovy-io)
+- [Convert String to Integer in Groovy](https://www.baeldung.com/groovy-convert-string-to-integer)
 - [[More -->]](/core-groovy-2)

core-java-modules/core-java-14/README.md

@@ -8,3 +8,4 @@ This module contains articles about Java 14.
 - [Java Text Blocks](https://www.baeldung.com/java-text-blocks)
 - [Pattern Matching for instanceof in Java 14](https://www.baeldung.com/java-pattern-matching-instanceof)
 - [Helpful NullPointerExceptions in Java 14](https://www.baeldung.com/java-14-nullpointerexception)
+- [Foreign Memory Access API in Java 14](https://www.baeldung.com/java-foreign-memory-access)

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/record/Person.java

@@ -0,0 +1,22 @@
+package com.baeldung.java14.record;
+
+import java.util.Objects;
+
+public record Person (String name, String address) {
+	
+	public static String UNKWOWN_ADDRESS = "Unknown";
+	public static String UNNAMED = "Unnamed";
+
+	public Person {
+		Objects.requireNonNull(name);
+		Objects.requireNonNull(address);
+	}
+	
+	public Person(String name) {
+		this(name, UNKWOWN_ADDRESS);
+	}
+	
+	public static Person unnamed(String address) {
+		return new Person(UNNAMED, address);
+	}
+}

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/foreign/api/ForeignMemoryUnitTest.java

@@ -0,0 +1,84 @@
+package com.baeldung.java14.foreign.api;
+
+import jdk.incubator.foreign.*;
+import org.junit.Test;
+
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertThat;
+
+import java.lang.invoke.VarHandle;
+import java.nio.ByteOrder;
+
+public class ForeignMemoryUnitTest {
+
+    @Test
+    public void whenAValueIsSet_thenAccessTheValue() {
+        long value = 10;
+        MemoryAddress memoryAddress =
+          MemorySegment.allocateNative(8).baseAddress();
+        VarHandle varHandle = MemoryHandles.varHandle(long.class,
+          ByteOrder.nativeOrder());
+        varHandle.set(memoryAddress, value);
+        assertThat(varHandle.get(memoryAddress), is(value));
+    }
+
+    @Test
+    public void whenMultipleValuesAreSet_thenAccessAll() {
+        VarHandle varHandle = MemoryHandles.varHandle(int.class,
+          ByteOrder.nativeOrder());
+
+        try(MemorySegment memorySegment =
+          MemorySegment.allocateNative(100)) {
+            MemoryAddress base = memorySegment.baseAddress();
+            for(int i=0; i<25; i++) {
+                varHandle.set(base.addOffset((i*4)), i);
+            }
+            for(int i=0; i<25; i++) {
+                assertThat(varHandle.get(base.addOffset((i*4))), is(i));
+            }
+        }
+    }
+
+    @Test
+    public void whenSetValuesWithMemoryLayout_thenTheyCanBeRetrieved() {
+        SequenceLayout sequenceLayout =
+          MemoryLayout.ofSequence(25,
+            MemoryLayout.ofValueBits(64, ByteOrder.nativeOrder()));
+        VarHandle varHandle =
+          sequenceLayout.varHandle(long.class,
+            MemoryLayout.PathElement.sequenceElement());
+
+        try(MemorySegment memorySegment =
+          MemorySegment.allocateNative(sequenceLayout)) {
+            MemoryAddress base = memorySegment.baseAddress();
+            for(long i=0; i<sequenceLayout.elementCount().getAsLong(); i++) {
+                varHandle.set(base, i, i);
+            }
+            for(long i=0; i<sequenceLayout.elementCount().getAsLong(); i++) {
+                assertThat(varHandle.get(base, i), is(i));
+            }
+        }
+    }
+
+    @Test
+    public void whenSlicingMemorySegment_thenTheyCanBeAccessedIndividually() {
+        MemoryAddress memoryAddress =
+          MemorySegment.allocateNative(12).baseAddress();
+        MemoryAddress memoryAddress1 =
+          memoryAddress.segment().asSlice(0,4).baseAddress();
+        MemoryAddress memoryAddress2 =
+          memoryAddress.segment().asSlice(4,4).baseAddress();
+        MemoryAddress memoryAddress3 =
+          memoryAddress.segment().asSlice(8,4).baseAddress();
+
+        VarHandle intHandle =
+          MemoryHandles.varHandle(int.class, ByteOrder.nativeOrder());
+        intHandle.set(memoryAddress1, Integer.MIN_VALUE);
+        intHandle.set(memoryAddress2, 0);
+        intHandle.set(memoryAddress3, Integer.MAX_VALUE);
+
+        assertThat(intHandle.get(memoryAddress1), is(Integer.MIN_VALUE));
+        assertThat(intHandle.get(memoryAddress2), is(0));
+        assertThat(intHandle.get(memoryAddress3), is(Integer.MAX_VALUE));
+    }
+}

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/record/PersonTest.java

@@ -0,0 +1,150 @@
+package com.baeldung.java14.record;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class PersonTest {
+
+    @Test
+    public void givenSameNameAndAddress_whenEquals_thenPersonsEqual() {
+
+        String name = "John Doe";
+        String address = "100 Linda Ln.";
+
+        Person person1 = new Person(name, address);
+        Person person2 = new Person(name, address);
+
+        assertTrue(person1.equals(person2));
+    }
+    
+    @Test
+    public void givenDifferentObject_whenEquals_thenNotEqual() {
+
+        Person person = new Person("John Doe", "100 Linda Ln.");
+
+        assertFalse(person.equals(new Object()));
+    }
+
+    @Test
+    public void givenDifferentName_whenEquals_thenPersonsNotEqual() {
+    
+        String address = "100 Linda Ln.";
+    
+        Person person1 = new Person("Jane Doe", address);
+        Person person2 = new Person("John Doe", address);
+    
+        assertFalse(person1.equals(person2));
+    }
+    
+    @Test
+    public void givenDifferentAddress_whenEquals_thenPersonsNotEqual() {
+    
+        String name = "John Doe";
+    
+        Person person1 = new Person(name, "100 Linda Ln.");
+        Person person2 = new Person(name, "200 London Ave.");
+    
+        assertFalse(person1.equals(person2));
+    }
+
+    @Test
+    public void givenSameNameAndAddress_whenHashCode_thenPersonsEqual() {
+
+        String name = "John Doe";
+        String address = "100 Linda Ln.";
+
+        Person person1 = new Person(name, address);
+        Person person2 = new Person(name, address);
+
+        assertEquals(person1.hashCode(), person2.hashCode());
+    }
+    
+    @Test
+    public void givenDifferentObject_whenHashCode_thenNotEqual() {
+
+        Person person = new Person("John Doe", "100 Linda Ln.");
+
+        assertNotEquals(person.hashCode(), new Object().hashCode());
+    }
+
+    @Test
+    public void givenDifferentName_whenHashCode_thenPersonsNotEqual() {
+
+        String address = "100 Linda Ln.";
+
+        Person person1 = new Person("Jane Doe", address);
+        Person person2 = new Person("John Doe", address);
+
+        assertNotEquals(person1.hashCode(), person2.hashCode());
+    }
+
+    @Test
+    public void givenDifferentAddress_whenHashCode_thenPersonsNotEqual() {
+
+        String name = "John Doe";
+
+        Person person1 = new Person(name, "100 Linda Ln.");
+        Person person2 = new Person(name, "200 London Ave.");
+
+        assertNotEquals(person1.hashCode(), person2.hashCode());
+    }
+
+    @Test
+    public void givenValidNameAndAddress_whenGetNameAndAddress_thenExpectedValuesReturned() {
+
+        String name = "John Doe";
+        String address = "100 Linda Ln.";
+
+        Person person = new Person(name, address);
+
+        assertEquals(name, person.name());
+        assertEquals(address, person.address());
+    }
+
+    @Test
+    public void givenValidNameAndAddress_whenToString_thenCorrectStringReturned() {
+
+        String name = "John Doe";
+        String address = "100 Linda Ln.";
+
+        Person person = new Person(name, address);
+
+        assertEquals("Person[name=" + name + ", address=" + address + "]", person.toString());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenNullName_whenConstruct_thenErrorThrown() {
+        new Person(null, "100 Linda Ln.");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenNullAddress_whenConstruct_thenErrorThrown() {
+        new Person("John Doe", null);
+    }
+
+    @Test
+    public void givenUnknownAddress_whenConstructing_thenAddressPopulated() {
+
+        String name = "John Doe";
+
+        Person person = new Person(name);
+
+        assertEquals(name, person.name());
+        assertEquals(Person.UNKWOWN_ADDRESS, person.address());
+    }
+
+    @Test
+    public void givenUnnamed_whenConstructingThroughFactory_thenNamePopulated() {
+
+        String address = "100 Linda Ln.";
+
+        Person person = Person.unnamed(address);
+
+        assertEquals(Person.UNNAMED, person.name());
+        assertEquals(address, person.address());
+    }
+}

core-java-modules/core-java-8-2/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-8-2</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-8-datetime-2/pom.xml

@@ -8,12 +8,11 @@
     <version>${project.parent.version}</version>
     <name>core-java-8-datetime</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-8-datetime/pom.xml

@@ -8,12 +8,11 @@
     <version>${project.parent.version}</version>
     <name>core-java-8-datetime</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-8/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-8</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-9-improvements/README.md

@@ -9,3 +9,4 @@ This module contains articles about the improvements to core Java features intro
 - [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
 - [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
 - [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)
+- [Java InputStream to Byte Array and ByteBuffer](https://www.baeldung.com/convert-input-stream-to-array-of-bytes)

core-java-modules/core-java-9-improvements/pom.xml

@@ -33,6 +33,11 @@
             <artifactId>guava</artifactId>
             <version>${guava.version}</version>
         </dependency>
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>${commons-io.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.junit.platform</groupId>
             <artifactId>junit-platform-runner</artifactId>

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/io/conversion/InputStreamToByteArrayUnitTest.java

@@ -0,0 +1,57 @@
+package com.baeldung.java9.io.conversion;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.apache.commons.io.IOUtils;
+import org.junit.Test;
+
+import com.google.common.io.ByteSource;
+import com.google.common.io.ByteStreams;
+
+public class InputStreamToByteArrayUnitTest {
+
+    @Test
+    public final void givenUsingPlainJavaOnFixedSizeStream_whenConvertingAnInputStreamToAByteArray_thenCorrect() throws IOException {
+        final InputStream initialStream = new ByteArrayInputStream(new byte[] { 0, 1, 2 });
+        final byte[] targetArray = new byte[initialStream.available()];
+        initialStream.read(targetArray);
+    }
+
+    @Test
+    public final void givenUsingPlainJavaOnUnknownSizeStream_whenConvertingAnInputStreamToAByteArray_thenCorrect() throws IOException {
+        final InputStream is = new ByteArrayInputStream(new byte[] { 0, 1, 2 });
+
+        final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        int nRead;
+        final byte[] data = new byte[1024];
+        while ((nRead = is.read(data, 0, data.length)) != -1) {
+            buffer.write(data, 0, nRead);
+        }
+
+        buffer.flush();
+        final byte[] byteArray = buffer.toByteArray();
+    }
+
+    @Test
+    public void givenUsingPlainJava9_whenConvertingAnInputStreamToAByteArray_thenCorrect() throws IOException {
+        final InputStream is = new ByteArrayInputStream(new byte[] { 0, 1, 2 });
+
+        byte[] data = is.readAllBytes();
+    }
+
+    @Test
+    public final void givenUsingGuava_whenConvertingAnInputStreamToAByteArray_thenCorrect() throws IOException {
+        final InputStream initialStream = ByteSource.wrap(new byte[] { 0, 1, 2 })
+            .openStream();
+        final byte[] targetArray = ByteStreams.toByteArray(initialStream);
+    }
+
+    @Test
+    public final void givenUsingCommonsIO_whenConvertingAnInputStreamToAByteArray_thenCorrect() throws IOException {
+        final InputStream initialStream = new ByteArrayInputStream(new byte[] { 0, 1, 2 });
+        final byte[] targetArray = IOUtils.toByteArray(initialStream);
+    }
+}

core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/io/conversion/InputStreamToByteBufferUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.inputstreamtobytes;
+package com.baeldung.java9.io.conversion;
 
 import com.google.common.io.ByteSource;
 import com.google.common.io.ByteStreams;

core-java-modules/core-java-9-new-features/README.md

@@ -12,3 +12,4 @@ This module contains articles about core Java features that have been introduced
 - [Introduction to Java 9 StackWalking API](https://www.baeldung.com/java-9-stackwalking-api)
 - [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
 - [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)
+- [Multi-Release JAR Files with Maven](https://www.baeldung.com/maven-multi-release-jars)

core-java-modules/core-java-9-new-features/pom.xml

@@ -28,8 +28,104 @@
             <version>${junit.platform.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${awaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
-
+    <profiles>
+        <profile>
+            <id>incubator-features</id>
+            <build>
+                <finalName>core-java-9-new-features</finalName>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-compiler-plugin</artifactId>
+                        <version>${maven-compiler-plugin.version}</version>
+                        <configuration>
+                            <source>${maven.compiler.source}</source>
+                            <target>${maven.compiler.target}</target>
+                            <compilerArgument>--add-modules=jdk.incubator.httpclient</compilerArgument>
+                        </configuration>
+                    </plugin>
+                    <plugin>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <configuration>
+                            <argLine>--add-modules=jdk.incubator.httpclient</argLine>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+        <profile>
+            <id>mrjar-generation</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-compiler-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <id>compile-java-8</id>
+                                <goals>
+                                    <goal>compile</goal>
+                                </goals>
+                                <configuration>
+                                    <source>1.8</source>
+                                    <target>1.8</target>
+                                    <compileSourceRoots>
+                                        <compileSourceRoot>${project.basedir}/src/main/java8</compileSourceRoot>
+                                    </compileSourceRoots>
+                                </configuration>
+                            </execution>
+                            <execution>
+                                <id>compile-java-9</id>
+                                <phase>compile</phase>
+                                <goals>
+                                    <goal>compile</goal>
+                                </goals>
+                                <configuration>
+                                    <release>9</release>
+                                    <compileSourceRoots>
+                                        <compileSourceRoot>${project.basedir}/src/main/java9</compileSourceRoot>
+                                    </compileSourceRoots>
+                                    <outputDirectory>${project.build.outputDirectory}/META-INF/versions/9</outputDirectory>
+                                </configuration>
+                            </execution>
+                            <execution>
+                                <id>default-testCompile</id>
+                                <phase>test-compile</phase>
+                                <goals>
+                                    <goal>testCompile</goal>
+                                </goals>
+                                <configuration>
+                                    <skip>true</skip>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-jar-plugin</artifactId>
+                        <version>${maven-jar-plugin.version}</version>
+                        <configuration>
+                            <archive>
+                                <manifestEntries>
+                                    <Multi-Release>true</Multi-Release>
+                                </manifestEntries>
+                                <manifest>
+                                    <mainClass>com.baeldung.multireleaseapp.App</mainClass>
+                                </manifest>
+                            </archive>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
     <build>
         <finalName>core-java-9-new-features</finalName>
         <plugins>
@@ -56,8 +152,10 @@
         <!-- testing -->
         <assertj.version>3.10.0</assertj.version>
         <junit.platform.version>1.2.0</junit.platform.version>
+        <awaitility.version>4.0.2</awaitility.version>
         <maven.compiler.source>1.9</maven.compiler.source>
         <maven.compiler.target>1.9</maven.compiler.target>
+        <maven-jar-plugin.version>3.2.0</maven-jar-plugin.version>
     </properties>
 
 </project>

core-java-modules/core-java-9-new-features/src/main/java8/com/baeldung/multireleaseapp/App.java

@@ -0,0 +1,14 @@
+package com.baeldung.multireleaseapp;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class App {
+
+    private static final Logger logger = LoggerFactory.getLogger(App.class);
+
+    public static void main(String[] args) {
+        logger.info(String.format("Running on %s", new DefaultVersion().version()));
+    }
+
+}

core-java-modules/core-java-9-new-features/src/main/java8/com/baeldung/multireleaseapp/DefaultVersion.java

@@ -0,0 +1,9 @@
+package com.baeldung.multireleaseapp;
+
+public class DefaultVersion implements Version {
+
+    @Override
+    public String version() {
+        return System.getProperty("java.version");
+    }
+}

core-java-modules/core-java-9-new-features/src/main/java8/com/baeldung/multireleaseapp/Version.java

@@ -0,0 +1,5 @@
+package com.baeldung.multireleaseapp;
+
+interface Version {
+    public String version();
+}

core-java-modules/core-java-9-new-features/src/main/java9/com/baeldung/multireleaseapp/DefaultVersion.java

@@ -0,0 +1,9 @@
+package com.baeldung.multireleaseapp;
+
+public class DefaultVersion implements Version {
+
+    @Override
+    public String version() {
+        return Runtime.version().toString();
+    }
+}

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/httpclient/HttpClientIntegrationTest.java

@@ -24,7 +24,7 @@ import static org.junit.Assert.assertThat;
 /**
  * Created by adam.
  */
-public class HttpClientTest {
+public class HttpClientIntegrationTest {
 
     @Test
     public void shouldReturnSampleDataContentWhenConnectViaSystemProxy() throws IOException, InterruptedException, URISyntaxException {
@@ -55,7 +55,7 @@ public class HttpClientTest {
             .send(request, HttpResponse.BodyHandler.asString());
 
         assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_MOVED_PERM));
-        assertThat(response.body(), containsString("https://stackoverflow.com/"));
+        assertThat(response.body(), containsString(""));
     }
 
     @Test

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/httpclient/HttpRequestIntegrationTest.java

@@ -22,7 +22,7 @@ import static org.junit.Assert.assertThat;
 /**
  * Created by adam.
  */
-public class HttpRequestTest {
+public class HttpRequestIntegrationTest {
 
     @Test
     public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/httpclient/HttpResponseIntegrationTest.java

@@ -18,7 +18,7 @@ import static org.junit.Assert.assertThat;
 /**
  * Created by adam.
  */
-public class HttpResponseTest {
+public class HttpResponseIntegrationTest {
 
     @Test
     public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/streams/reactive/ReactiveStreamsUnitTest.java

@@ -5,10 +5,12 @@ import org.junit.Test;
 
 import java.util.List;
 import java.util.concurrent.SubmissionPublisher;
+import java.util.concurrent.TimeUnit;
 
-import static org.assertj.core.api.Java6Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.awaitility.Awaitility.await;
 
-public class ReactiveStreamsTest {
+public class ReactiveStreamsUnitTest {
 
     @Test
     public void givenPublisher_whenSubscribeToIt_thenShouldConsumeAllElements() throws InterruptedException {
@@ -25,7 +27,7 @@ public class ReactiveStreamsTest {
 
         //then
 
-        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+        await().atMost(1000, TimeUnit.MILLISECONDS).untilAsserted(
                 () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(items)
         );
     }
@@ -46,7 +48,7 @@ public class ReactiveStreamsTest {
         publisher.close();
 
         //then
-        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+        await().atMost(1000, TimeUnit.MILLISECONDS).untilAsserted(
                 () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(expectedResult)
         );
     }
@@ -66,7 +68,7 @@ public class ReactiveStreamsTest {
         publisher.close();
 
         //then
-        await().atMost(1000, TimeUnit.MILLISECONDS).until(
+        await().atMost(1000, TimeUnit.MILLISECONDS).untilAsserted(
                 () -> assertThat(subscriber.consumedElements).containsExactlyElementsOf(expected)
         );
     }

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/varhandles/VariableHandlesUnitTest.java

@@ -7,7 +7,7 @@ import java.lang.invoke.VarHandle;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-public class VariableHandlesTest {
+public class VariableHandlesUnitTest {
 
     public int publicTestVariable = 1;
     private int privateTestVariable = 1;
@@ -20,22 +20,22 @@ public class VariableHandlesTest {
     public void whenVariableHandleForPublicVariableIsCreated_ThenItIsInitializedProperly() throws NoSuchFieldException, IllegalAccessException {
         VarHandle publicIntHandle = MethodHandles
           .lookup()
-          .in(VariableHandlesTest.class)
+          .in(VariableHandlesUnitTest.class)
-          .findVarHandle(VariableHandlesTest.class, "publicTestVariable", int.class);
+          .findVarHandle(VariableHandlesUnitTest.class, "publicTestVariable", int.class);
 
         assertThat(publicIntHandle.coordinateTypes().size() == 1);
-        assertThat(publicIntHandle.coordinateTypes().get(0) == VariableHandles.class);
+        assertThat(publicIntHandle.coordinateTypes().get(0) == VariableHandlesUnitTest.class);
 
     }
 
     @Test
     public void whenVariableHandleForPrivateVariableIsCreated_ThenItIsInitializedProperly() throws NoSuchFieldException, IllegalAccessException {
         VarHandle privateIntHandle = MethodHandles
-          .privateLookupIn(VariableHandlesTest.class, MethodHandles.lookup())
+          .privateLookupIn(VariableHandlesUnitTest.class, MethodHandles.lookup())
-          .findVarHandle(VariableHandlesTest.class, "privateTestVariable", int.class);
+          .findVarHandle(VariableHandlesUnitTest.class, "privateTestVariable", int.class);
 
         assertThat(privateIntHandle.coordinateTypes().size() == 1);
-        assertThat(privateIntHandle.coordinateTypes().get(0) == VariableHandlesTest.class);
+        assertThat(privateIntHandle.coordinateTypes().get(0) == VariableHandlesUnitTest.class);
 
     }
 
@@ -52,8 +52,8 @@ public class VariableHandlesTest {
     public void givenVarHandle_whenGetIsInvoked_ThenValueOfVariableIsReturned() throws NoSuchFieldException, IllegalAccessException {
         VarHandle publicIntHandle = MethodHandles
           .lookup()
-          .in(VariableHandlesTest.class)
+          .in(VariableHandlesUnitTest.class)
-          .findVarHandle(VariableHandlesTest.class, "publicTestVariable", int.class);
+          .findVarHandle(VariableHandlesUnitTest.class, "publicTestVariable", int.class);
 
         assertThat((int) publicIntHandle.get(this) == 1);
     }
@@ -62,8 +62,8 @@ public class VariableHandlesTest {
     public void givenVarHandle_whenSetIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
         VarHandle publicIntHandle = MethodHandles
           .lookup()
-          .in(VariableHandlesTest.class)
+          .in(VariableHandlesUnitTest.class)
-          .findVarHandle(VariableHandlesTest.class, "variableToSet", int.class);
+          .findVarHandle(VariableHandlesUnitTest.class, "variableToSet", int.class);
         publicIntHandle.set(this, 15);
 
         assertThat((int) publicIntHandle.get(this) == 15);
@@ -73,8 +73,8 @@ public class VariableHandlesTest {
     public void givenVarHandle_whenCompareAndSetIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
         VarHandle publicIntHandle = MethodHandles
           .lookup()
-          .in(VariableHandlesTest.class)
+          .in(VariableHandlesUnitTest.class)
-          .findVarHandle(VariableHandlesTest.class, "variableToCompareAndSet", int.class);
+          .findVarHandle(VariableHandlesUnitTest.class, "variableToCompareAndSet", int.class);
         publicIntHandle.compareAndSet(this, 1, 100);
 
         assertThat((int) publicIntHandle.get(this) == 100);
@@ -84,8 +84,8 @@ public class VariableHandlesTest {
     public void givenVarHandle_whenGetAndAddIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
         VarHandle publicIntHandle = MethodHandles
           .lookup()
-          .in(VariableHandlesTest.class)
+          .in(VariableHandlesUnitTest.class)
-          .findVarHandle(VariableHandlesTest.class, "variableToGetAndAdd", int.class);
+          .findVarHandle(VariableHandlesUnitTest.class, "variableToGetAndAdd", int.class);
         int before = (int) publicIntHandle.getAndAdd(this, 200);
 
         assertThat(before == 0);
@@ -96,8 +96,8 @@ public class VariableHandlesTest {
     public void givenVarHandle_whenGetAndBitwiseOrIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
         VarHandle publicIntHandle = MethodHandles
           .lookup()
-          .in(VariableHandlesTest.class)
+          .in(VariableHandlesUnitTest.class)
-          .findVarHandle(VariableHandlesTest.class, "variableToBitwiseOr", byte.class);
+          .findVarHandle(VariableHandlesUnitTest.class, "variableToBitwiseOr", byte.class);
         byte before = (byte) publicIntHandle.getAndBitwiseOr(this, (byte) 127);
 
         assertThat(before == 0);

core-java-modules/core-java-9-streams/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-9-streams</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <build>

core-java-modules/core-java-annotations/pom.xml

@@ -10,10 +10,10 @@
     <packaging>jar</packaging>
 
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <build>

core-java-modules/core-java-arrays-convert/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>core-java-modules</artifactId>
         <groupId>com.baeldung.core-java-modules</groupId>
-        <version>1.0.0-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

core-java-modules/core-java-arrays-guides/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>core-java-modules</artifactId>
         <groupId>com.baeldung.core-java-modules</groupId>
-        <version>1.0.0-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

core-java-modules/core-java-arrays-multidimensional/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>core-java-modules</artifactId>
         <groupId>com.baeldung.core-java-modules</groupId>
-        <version>1.0.0-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

core-java-modules/core-java-arrays-operations-advanced/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>core-java-modules</artifactId>
         <groupId>com.baeldung.core-java-modules</groupId>
-        <version>1.0.0-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

core-java-modules/core-java-arrays-operations-basic/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <artifactId>core-java-modules</artifactId>
         <groupId>com.baeldung.core-java-modules</groupId>
-        <version>1.0.0-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

core-java-modules/core-java-arrays-sorting/pom.xml

@@ -5,8 +5,8 @@
     <parent>
         <artifactId>core-java-modules</artifactId>
         <groupId>com.baeldung.core-java-modules</groupId>
-        <version>1.0.0-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../pom.xml</relativePath>
+        <relativePath>../</relativePath>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

core-java-modules/core-java-collections-2/pom.xml

@@ -7,12 +7,11 @@
     <artifactId>core-java-collections-2</artifactId>
     <name>core-java-collections-2</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-3/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-3</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-array-list/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-array-list</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-list-2/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-list-2</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-list-3/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-list-3</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-list/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-list</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-maps-2/pom.xml

@@ -7,12 +7,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-maps-2</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-maps-3/README.md

@@ -5,4 +5,5 @@ This module contains articles about Map data structures in Java.
 ### Relevant Articles: 
 - [Java TreeMap vs HashMap](https://www.baeldung.com/java-treemap-vs-hashmap)
 - [Comparing Two HashMaps in Java](https://www.baeldung.com/java-compare-hashmaps)
+- [The Map.computeIfAbsent() Method](https://www.baeldung.com/java-map-computeifabsent)
 - More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-2)

core-java-modules/core-java-collections-maps-3/pom.xml

@@ -7,12 +7,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-maps-3</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-maps/pom.xml

@@ -6,12 +6,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-maps</name>
     <packaging>jar</packaging>
-
+    <parent>
-   <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <groupId>com.baeldung</groupId>
+        <artifactId>core-java-modules</artifactId>
-        <artifactId>parent-java</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections-set/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections-set</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-collections/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-collections</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-concurrency-2/README.md

@@ -4,5 +4,5 @@
 
 ### Relevant Articles: 
 - [Using a Mutex Object in Java](https://www.baeldung.com/java-mutex)
-- [Testing Multi-Threaded Code in Java] (https://www.baeldung.com/java-testing-multithreaded)
+- [Testing Multi-Threaded Code in Java](https://www.baeldung.com/java-testing-multithreaded)
 

core-java-modules/core-java-concurrency-2/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-concurrency-2</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 	
 	<dependencies>

core-java-modules/core-java-concurrency-advanced-2/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-concurrency-advanced-2</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-concurrency-advanced-3/README.md

@@ -11,4 +11,6 @@ This module contains articles about advanced topics about multithreading with co
 - [Guide to Work Stealing in Java](https://www.baeldung.com/java-work-stealing)
 - [Asynchronous Programming in Java](https://www.baeldung.com/java-asynchronous-programming)
 - [Java Thread Deadlock and Livelock](https://www.baeldung.com/java-deadlock-livelock)
+- [Guide to AtomicStampedReference in Java](https://www.baeldung.com/java-atomicstampedreference)
+- [The ABA Problem in Concurrency](https://www.baeldung.com/cs/aba-concurrency)
 - [[<-- previous]](/core-java-modules/core-java-concurrency-advanced-2)

core-java-modules/core-java-concurrency-advanced-3/pom.xml

@@ -9,12 +9,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-concurrency-advanced-3</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/atomicstampedreference/StampedAccount.java

@@ -9,13 +9,11 @@ public class StampedAccount {
     private AtomicStampedReference<Integer> account = new AtomicStampedReference<>(0, 0);
 
     public int getBalance() {
-        return this.account.get(new int[1]);
+        return account.getReference();
     }
 
     public int getStamp() {
-        int[] stamps = new int[1];
+        return account.getStamp();
-        this.account.get(stamps);
-        return stamps[0];
     }
 
     public boolean deposit(int funds) {

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/deadlockAndLivelock/DeadlockExample.java

@@ -0,0 +1,60 @@
+package com.baeldung.deadlockAndLivelock;
+
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class DeadlockExample {
+
+    private Lock lock1 = new ReentrantLock(true);
+    private Lock lock2 = new ReentrantLock(true);
+
+    public static void main(String[] args) {
+        DeadlockExample deadlock = new DeadlockExample();
+        new Thread(deadlock::operation1, "T1").start();
+        new Thread(deadlock::operation2, "T2").start();
+
+    }
+
+    public void operation1() {
+        lock1.lock();
+        print("lock1 acquired, waiting to acquire lock2.");
+        sleep(50);
+
+        lock2.lock();
+        print("lock2 acquired");
+
+        print("executing first operation.");
+
+        lock2.unlock();
+        lock1.unlock();
+
+    }
+
+    public void operation2() {
+        lock2.lock();
+        print("lock2 acquired, waiting to acquire lock1.");
+        sleep(50);
+
+        lock1.lock();
+        print("lock1 acquired");
+
+        print("executing second operation.");
+
+        lock1.unlock();
+        lock2.unlock();
+    }
+
+    public void print(String message) {
+        System.out.println("Thread " + Thread.currentThread()
+            .getName() + ": " + message);
+    }
+
+    public void sleep(long millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/deadlockAndLivelock/LivelockExample.java

@@ -0,0 +1,86 @@
+package com.baeldung.deadlockAndLivelock;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class LivelockExample {
+
+    private Lock lock1 = new ReentrantLock(true);
+    private Lock lock2 = new ReentrantLock(true);
+
+    public static void main(String[] args) {
+        LivelockExample livelock = new LivelockExample();
+        new Thread(livelock::operation1, "T1").start();
+        new Thread(livelock::operation2, "T2").start();
+
+    }
+
+    public void operation1() {
+        while (true) {
+            tryLock(lock1, 50);
+            print("lock1 acquired, trying to acquire lock2.");
+            sleep(50);
+
+            if (tryLock(lock2)) {
+                print("lock2 acquired.");
+            } else {
+                print("cannot acquire lock2, releasing lock1.");
+                lock1.unlock();
+                continue;
+            }
+
+            print("executing first operation.");
+            break;
+        }
+        lock2.unlock();
+        lock1.unlock();
+    }
+
+    public void operation2() {
+        while (true) {
+            tryLock(lock2, 50);
+            print("lock2 acquired, trying to acquire lock1.");
+            sleep(50);
+
+            if (tryLock(lock1)) {
+                print("lock1 acquired.");
+            } else {
+                print("cannot acquire lock1, releasing lock2.");
+                lock2.unlock();
+                continue;
+            }
+
+            print("executing second operation.");
+            break;
+        }
+        lock1.unlock();
+        lock2.unlock();
+    }
+
+    public void print(String message) {
+        System.out.println("Thread " + Thread.currentThread()
+            .getName() + ": " + message);
+    }
+
+    public void sleep(long millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public void tryLock(Lock lock, long millis) {
+        try {
+            lock.tryLock(10, TimeUnit.MILLISECONDS);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public boolean tryLock(Lock lock) {
+        return lock.tryLock();
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/lockfree/NonBlockingQueue.java

@@ -0,0 +1,81 @@
+package com.baeldung.lockfree;
+
+import java.util.NoSuchElementException;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+
+public class NonBlockingQueue<T> {
+
+    private final AtomicReference<Node<T>> head, tail;
+    private final AtomicInteger size;
+
+    public NonBlockingQueue() {
+        head = new AtomicReference<>(null);
+        tail = new AtomicReference<>(null);
+        size = new AtomicInteger();
+        size.set(0);
+    }
+
+    public void add(T element) {
+        if (element == null) {
+            throw new NullPointerException();
+        }
+
+        Node<T> node = new Node<>(element);
+        Node<T> currentTail;
+        do {
+            currentTail = tail.get();
+            node.setPrevious(currentTail);
+        } while(!tail.compareAndSet(currentTail, node));
+
+        if(node.previous != null) {
+            node.previous.next = node;
+        }
+
+        head.compareAndSet(null, node); //if we are inserting the first element
+        size.incrementAndGet();
+    }
+
+    public T get() {
+        if(head.get() == null) {
+            throw new NoSuchElementException();
+        }
+
+        Node<T> currentHead;
+        Node<T> nextNode;
+        do {
+            currentHead = head.get();
+            nextNode = currentHead.getNext();
+        } while(!head.compareAndSet(currentHead, nextNode));
+
+        size.decrementAndGet();
+        return currentHead.getValue();
+    }
+
+    public int size() {
+        return this.size.get();
+    }
+
+    private class Node<T> {
+        private final T value;
+        private volatile Node<T> next;
+        private volatile Node<T> previous;
+
+        public Node(T value) {
+            this.value = value;
+            this.next = null;
+        }
+
+        public T getValue() {
+            return value;
+        }
+
+        public Node<T> getNext() {
+            return next;
+        }
+
+        public void setPrevious(Node<T> previous) {
+            this.previous = previous;
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-3/src/test/java/com/baeldung/exchanger/ExchangerPipeLineManualTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.exchanger;
+
+import java.util.Queue;
+import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.Exchanger;
+import java.util.concurrent.ExecutionException;
+import org.junit.Test;
+
+import static java.util.concurrent.CompletableFuture.runAsync;
+
+
+
+public class ExchangerPipeLineManualTest {
+
+    private static final int BUFFER_SIZE = 100;
+
+    @Test
+    public void givenData_whenPassedThrough_thenCorrect() throws InterruptedException, ExecutionException {
+
+        Exchanger<Queue<String>> readerExchanger = new Exchanger<>();
+        Exchanger<Queue<String>> writerExchanger = new Exchanger<>();
+        int counter = 0;
+
+        Runnable reader = () -> {
+            Queue<String> readerBuffer = new ConcurrentLinkedQueue<>();
+            while (true) {
+                readerBuffer.add(UUID.randomUUID().toString());
+                if (readerBuffer.size() >= BUFFER_SIZE) {
+                    try {
+                        readerBuffer = readerExchanger.exchange(readerBuffer);
+                    } catch (InterruptedException e) {
+                        Thread.currentThread().interrupt();
+                        throw new RuntimeException(e);
+                    }
+                }
+            }
+        };
+
+        Runnable processor = () -> {
+            Queue<String> processorBuffer = new ConcurrentLinkedQueue<>();
+            Queue<String> writerBuffer = new ConcurrentLinkedQueue<>();
+            try {
+                processorBuffer = readerExchanger.exchange(processorBuffer);
+                while (true) {
+                    writerBuffer.add(processorBuffer.poll());
+                    if (processorBuffer.isEmpty()) {
+                        try {
+                            processorBuffer = readerExchanger.exchange(processorBuffer);
+                            writerBuffer = writerExchanger.exchange(writerBuffer);
+                        } catch (InterruptedException e) {
+                            Thread.currentThread().interrupt();
+                            throw new RuntimeException(e);
+                        }
+                    }
+                }
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new RuntimeException(e);
+            }
+        };
+
+        Runnable writer = () -> {
+            Queue<String> writerBuffer = new ConcurrentLinkedQueue<>();
+            try {
+                writerBuffer = writerExchanger.exchange(writerBuffer);
+                while (true) {
+                    System.out.println(writerBuffer.poll());
+                    if (writerBuffer.isEmpty()) {
+                        writerBuffer = writerExchanger.exchange(writerBuffer);
+                    }
+                }
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new RuntimeException(e);
+            }
+        };
+
+        CompletableFuture.allOf(runAsync(reader), runAsync(processor), runAsync(writer)).get();
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-3/src/test/java/com/baeldung/exchanger/ExchangerUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.exchanger;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Exchanger;
+
+import java.util.concurrent.ExecutionException;
+import org.junit.Test;
+
+import static java.util.concurrent.CompletableFuture.runAsync;
+
+public class ExchangerUnitTest {
+    
+    
+    @Test
+    public void givenThreads_whenMessageExchanged_thenCorrect() {
+        Exchanger<String> exchanger = new Exchanger<>();
+
+        Runnable taskA = () -> {
+            try {
+                String message = exchanger.exchange("from A");
+                assertEquals("from B", message);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new RuntimeException(e);
+            }
+        };
+
+        Runnable taskB = () -> {
+            try {
+                String message = exchanger.exchange("from B");
+                assertEquals("from A", message);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new RuntimeException(e);
+            }
+        };
+
+        CompletableFuture.allOf(runAsync(taskA), runAsync(taskB)).join();
+    }
+
+    @Test
+    public void givenThread_WhenExchangedMessage_thenCorrect() throws InterruptedException, ExecutionException {
+        Exchanger<String> exchanger = new Exchanger<>();
+
+        Runnable runner = () -> {
+            try {
+                String message = exchanger.exchange("from runner");
+                assertEquals("to runner", message);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new RuntimeException(e);
+            }
+        };
+
+        CompletableFuture<Void> result = CompletableFuture.runAsync(runner);
+        String msg = exchanger.exchange("to runner");
+        assertEquals("from runner", msg);
+        result.join();
+    }
+
+}

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

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-concurrency-advanced</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-concurrency-basic-2/pom.xml

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-concurrency-basic-2</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <build>

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

@@ -8,12 +8,11 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-concurrency-basic</name>
     <packaging>jar</packaging>
-
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

core-java-modules/core-java-concurrency-collections-2/pom.xml

@@ -23,7 +23,12 @@
             <artifactId>jmh-generator-annprocess</artifactId>
             <version>${jmh.version}</version>
         </dependency>
-
+		<dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
     <build>
         <sourceDirectory>src</sourceDirectory>
@@ -42,6 +47,8 @@
     <properties>
         <jmh.version>1.21</jmh.version>
         <guava.version>28.2-jre</guava.version>
+         <!-- testing -->
+        <assertj.version>3.6.1</assertj.version>
     </properties>
 
 </project>

core-java-modules/core-java-concurrency-collections-2/src/test/java/com/baeldung/concurrent/queue/TestConcurrentLinkedQueue.java

@@ -0,0 +1,66 @@
+package com.baeldung.concurrent.queue;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+
+@FixMethodOrder
+public class TestConcurrentLinkedQueue {
+
+    @Test
+    public void givenThereIsExistingCollection_WhenAddedIntoQueue_ThenShouldContainElements() {
+        Collection<Integer> elements = Arrays.asList(1, 2, 3, 4, 5);
+        ConcurrentLinkedQueue<Integer> concurrentLinkedQueue = new ConcurrentLinkedQueue<>(elements);
+        assertThat(concurrentLinkedQueue).containsExactly(1, 2, 3, 4, 5);
+    }
+
+    @Test
+    public void givenQueueIsEmpty_WhenAccessingTheQueue_ThenQueueReturnsNull() throws InterruptedException {
+        ExecutorService executorService = Executors.newFixedThreadPool(1);
+        ConcurrentLinkedQueue<Integer> concurrentLinkedQueue = new ConcurrentLinkedQueue<>();
+        executorService.submit(() -> assertNull("Retrieve object is null", concurrentLinkedQueue.poll()));
+        TimeUnit.SECONDS.sleep(1);
+        executorService.awaitTermination(1, TimeUnit.SECONDS);
+        executorService.shutdown();
+    }
+
+    @Test
+    public void givenProducerOffersElementInQueue_WhenConsumerPollsQueue_ThenItRetrievesElement() throws Exception {
+        int element = 1;
+
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        ConcurrentLinkedQueue<Integer> concurrentLinkedQueue = new ConcurrentLinkedQueue<>();
+        Runnable offerTask = () -> concurrentLinkedQueue.offer(element);
+
+        Callable<Integer> pollTask = () -> {
+            while (concurrentLinkedQueue.peek() != null) {
+                return concurrentLinkedQueue.poll()
+                    .intValue();
+            }
+            return null;
+        };
+
+        executorService.submit(offerTask);
+        TimeUnit.SECONDS.sleep(1);
+
+        Future<Integer> returnedElement = executorService.submit(pollTask);
+        assertThat(returnedElement.get()
+            .intValue(), is(equalTo(element)));
+        executorService.awaitTermination(1, TimeUnit.SECONDS);
+        executorService.shutdown();
+    }
+}

core-java-modules/core-java-concurrency-collections-2/src/test/java/com/baeldung/concurrent/queue/TestLinkedBlockingQueue.java

@@ -0,0 +1,81 @@
+package com.baeldung.concurrent.queue;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+
+@FixMethodOrder
+public class TestLinkedBlockingQueue {
+
+    @Test
+    public void givenThereIsExistingCollection_WhenAddedIntoQueue_ThenShouldContainElements() {
+        Collection<Integer> elements = Arrays.asList(1, 2, 3, 4, 5);
+        LinkedBlockingQueue<Integer> linkedBlockingQueue = new LinkedBlockingQueue<>(elements);
+        assertThat(linkedBlockingQueue).containsExactly(1, 2, 3, 4, 5);
+    }
+
+    @Test
+    public void givenQueueIsEmpty_WhenAccessingTheQueue_ThenThreadBlocks() throws InterruptedException {
+        ExecutorService executorService = Executors.newFixedThreadPool(1);
+        LinkedBlockingQueue<Integer> linkedBlockingQueue = new LinkedBlockingQueue<>();
+        executorService.submit(() -> {
+            try {
+                linkedBlockingQueue.take();
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        });
+        TimeUnit.SECONDS.sleep(1);
+        executorService.awaitTermination(1, TimeUnit.SECONDS);
+        executorService.shutdown();
+    }
+
+    @Test
+    public void givenProducerPutsElementInQueue_WhenConsumerAccessQueue_ThenItRetrieve() {
+        int element = 10;
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        LinkedBlockingQueue<Integer> linkedBlockingQueue = new LinkedBlockingQueue<>();
+        Runnable putTask = () -> {
+            try {
+                linkedBlockingQueue.put(element);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        };
+
+        Callable<Integer> takeTask = () -> {
+            try {
+                return linkedBlockingQueue.take();
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            return null;
+        };
+
+        executorService.submit(putTask);
+        Future<Integer> returnElement = executorService.submit(takeTask);
+        try {
+            TimeUnit.SECONDS.sleep(1);
+            assertThat(returnElement.get()
+                .intValue(), is(equalTo(element)));
+            executorService.awaitTermination(1, TimeUnit.SECONDS);
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+        executorService.shutdown();
+    }
+}