Merge remote-tracking branch 'eugenp/master'

core-java-modules/core-java-11/pom.xml

@@ -1,5 +1,7 @@
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+<project
-    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+        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>
     <groupId>com.baeldung</groupId>
     <artifactId>core-java-11</artifactId>
@@ -12,7 +14,7 @@
         <groupId>com.baeldung</groupId>
         <artifactId>parent-modules</artifactId>
         <version>1.0.0-SNAPSHOT</version>
-        <relativePath>../../</relativePath>
+        <relativePath>../..</relativePath>
     </parent>
 
     <dependencies>
@@ -21,6 +23,12 @@
             <artifactId>guava</artifactId>
             <version>${guava.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
@@ -41,6 +49,7 @@
         <maven.compiler.source.version>11</maven.compiler.source.version>
         <maven.compiler.target.version>11</maven.compiler.target.version>
         <guava.version>27.1-jre</guava.version>
+        <assertj.version>3.11.1</assertj.version>
     </properties>
 
 </project>

core-java-modules/core-java-11/src/main/java/com/baeldung/predicate/not/Person.java

@@ -0,0 +1,19 @@
+package com.baeldung.predicate.not;
+
+public class Person {
+    private static final int ADULT_AGE = 18;
+
+    private int age;
+
+    public Person(int age) {
+        this.age = age;
+    }
+
+    public boolean isAdult() {
+        return age >= ADULT_AGE;
+    }
+
+    public boolean isNotAdult() {
+        return !isAdult();
+    }
+}

core-java-modules/core-java-11/src/test/java/com/baeldung/AppUnitTest.java

@@ -7,7 +7,7 @@ import junit.framework.TestSuite;
 /**
  * Unit test for simple App.
  */
-public class AppTest 
+public class AppUnitTest
     extends TestCase
 {
     /**
@@ -15,7 +15,7 @@ public class AppTest
      *
      * @param testName name of the test case
      */
-    public AppTest( String testName )
+    public AppUnitTest(String testName )
     {
         super( testName );
     }
@@ -25,7 +25,7 @@ public class AppTest
      */
     public static Test suite()
     {
-        return new TestSuite( AppTest.class );
+        return new TestSuite( AppUnitTest.class );
     }
 
     /**

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpClientUnitTest.java

@@ -32,7 +32,7 @@ import java.util.stream.Collectors;
 
 import org.junit.jupiter.api.Test;
 
-public class HttpClientTest {
+public class HttpClientUnitTest {
 
     @Test
     public void shouldReturnSampleDataContentWhenConnectViaSystemProxy() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpRequestUnitTest.java

@@ -19,7 +19,7 @@ import java.time.Duration;
 
 import org.junit.Test;
 
-public class HttpRequestTest {
+public class HttpRequestUnitTest {
 
     @Test
     public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpResponseUnitTest.java

@@ -14,7 +14,7 @@ import java.net.http.HttpResponse;
 
 import org.junit.Test;
 
-public class HttpResponseTest {
+public class HttpResponseUnitTest {
 
     @Test
     public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-11/src/test/java/com/baeldung/predicate/not/PersonUnitTest.java

@@ -0,0 +1,61 @@
+package com.baeldung.predicate.not;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static java.util.function.Predicate.not;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class PersonUnitTest {
+    private List<Person> people;
+
+    @BeforeEach
+    void preparePeople() {
+        people = Arrays.asList(
+          new Person(1),
+          new Person(18),
+          new Person(2)
+        );
+    }
+
+    @Test
+    void givenPeople_whenFilterIsAdult_thenOneResult() {
+        List<Person> adults = people.stream()
+          .filter(Person::isAdult)
+          .collect(Collectors.toList());
+
+        assertThat(adults).size().isEqualTo(1);
+    }
+
+    @Test
+    void givenPeople_whenFilterIsAdultNegated_thenTwoResults() {
+        List<Person> nonAdults = people.stream()
+          .filter(person -> !person.isAdult())
+          .collect(Collectors.toList());
+
+        assertThat(nonAdults).size().isEqualTo(2);
+    }
+
+    @Test
+    void givenPeople_whenFilterIsNotAdult_thenTwoResults() {
+        List<Person> nonAdults = people.stream()
+          .filter(Person::isNotAdult)
+          .collect(Collectors.toList());
+
+        assertThat(nonAdults).size().isEqualTo(2);
+    }
+
+    @Test
+    void givenPeople_whenFilterNotIsAdult_thenTwoResults() {
+        List<Person> nonAdults = people.stream()
+          .filter(not(Person::isAdult))
+          .collect(Collectors.toList());
+
+        assertThat(nonAdults).size().isEqualTo(2);
+    }
+}

core-java-modules/core-java-12/src/test/java/com/baeldung/string/StringAPITest.java

@@ -0,0 +1,43 @@
+package com.baeldung.string;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class StringAPITest {
+
+    @Test
+    public void whenPositiveArgument_thenReturnIndentedString() {
+        String multilineStr = "This is\na multiline\nstring.";
+        String outputStr = "   This is\n   a multiline\n   string.\n";
+
+        String postIndent = multilineStr.indent(3);
+
+        assertThat(postIndent, equalTo(outputStr));
+    }
+
+    @Test
+    public void whenNegativeArgument_thenReturnReducedIndentedString() {
+        String multilineStr = "   This is\n   a multiline\n   string.";
+        String outputStr = " This is\n a multiline\n string.\n";
+
+        String postIndent = multilineStr.indent(-2);
+
+        assertThat(postIndent, equalTo(outputStr));
+    }
+
+    @Test
+    public void whenTransformUsingLamda_thenReturnTransformedString() {
+        String result = "hello".transform(input -> input + " world!");
+
+        assertThat(result, equalTo("hello world!"));
+    }
+
+    @Test
+    public void whenTransformUsingParseInt_thenReturnInt() {
+        int result = "42".transform(Integer::parseInt);
+
+        assertThat(result, equalTo(42));
+    }
+}

core-java-modules/core-java-8-2/src/main/java/com/baeldung/delay/Delay.java

@@ -0,0 +1,91 @@
+package com.baeldung.delay;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+
+public class Delay {
+
+    public static void main(String args[]) throws InterruptedException {
+        
+        threadSleep(4, 1);
+
+        timeunitSleep(4, 1);
+
+        delayedServiceTask(5);
+
+        fixedRateServiceTask(5);
+
+        System.out.println("Done.");
+
+        return;
+
+    }
+
+    private static void threadSleep(Integer iterations, Integer secondsToSleep) {
+
+        for (Integer i = 0; i < iterations; i++) {
+
+            System.out.println("This is loop iteration number " + i.toString());
+
+            try {
+                Thread.sleep(secondsToSleep * 1000);
+            } catch (InterruptedException ie) {
+                Thread.currentThread().interrupt();
+            }
+
+        }
+
+    }
+
+    private static void timeunitSleep(Integer iterations, Integer secondsToSleep) {
+
+        for (Integer i = 0; i < iterations; i++) {
+
+            System.out.println("This is loop iteration number " + i.toString());
+
+            try {
+                TimeUnit.SECONDS.sleep(secondsToSleep);
+            } catch (InterruptedException ie) {
+                Thread.currentThread().interrupt();
+            }
+
+        }
+
+    }
+
+    private static void delayedServiceTask(Integer delayInSeconds) {
+
+        ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
+
+        executorService.schedule(Delay::someTask1, delayInSeconds, TimeUnit.SECONDS);
+
+    }
+
+    private static void fixedRateServiceTask(Integer delayInSeconds) {
+
+        ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
+
+        ScheduledFuture<?> sf = executorService.scheduleAtFixedRate(Delay::someTask2, 0, delayInSeconds,
+                TimeUnit.SECONDS);
+
+        try {
+            TimeUnit.SECONDS.sleep(20);
+        } catch (InterruptedException ie) {
+            Thread.currentThread().interrupt();
+        }
+
+        sf.cancel(true);
+
+    }
+
+    private static void someTask1() {
+        System.out.println("Task 1 completed.");
+    }
+
+    private static void someTask2() {
+        System.out.println("Task 2 completed.");
+    }
+
+}

core-java-modules/core-java-collections-array-list/README.md

@@ -0,0 +1,10 @@
+=========
+
+## Core Java Collections Array List Cookbooks and Examples
+
+### Relevant Articles: 
+- [Immutable ArrayList in Java](http://www.baeldung.com/java-immutable-list)
+- [Guide to the Java ArrayList](http://www.baeldung.com/java-arraylist)
+- [Add Multiple Items to an Java ArrayList](http://www.baeldung.com/java-add-items-array-list)
+- [ClassCastException: Arrays$ArrayList cannot be cast to ArrayList](https://www.baeldung.com/java-classcastexception-arrays-arraylist)
+- [Multi Dimensional ArrayList in Java](https://www.baeldung.com/java-multi-dimensional-arraylist)

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

@@ -0,0 +1,46 @@
+<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-collections-array-list</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-collections-array-list</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>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <commons-collections4.version>4.1</commons-collections4.version>
+        <commons-lang3.version>3.8.1</commons-lang3.version>
+        <assertj.version>3.11.1</assertj.version>
+    </properties>
+</project>

core-java-modules/core-java-collections-array-list/src/main/java/com/baeldung/java/list/Flower.java

@@ -0,0 +1,28 @@
+package com.baeldung.java.list;
+
+public class Flower {
+
+    private String name;
+    private int petals;
+
+    public Flower(String name, int petals) {
+        this.name = name;
+        this.petals = petals;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getPetals() {
+        return petals;
+    }
+
+    public void setPetals(int petals) {
+        this.petals = petals;
+    }
+}

core-java-modules/core-java-collections-array-list/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?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>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

core-java-modules/core-java-collections-list-2/README.md

@@ -0,0 +1,17 @@
+=========
+
+## Core Java Collections List Cookbooks and Examples
+
+### Relevant Articles: 
+- [Check If Two Lists are Equal in Java](http://www.baeldung.com/java-test-a-list-for-ordinality-and-equality)
+- [Java 8 Streams: Find Items From One List Based On Values From Another List](https://www.baeldung.com/java-streams-find-list-items)
+- [A Guide to the Java LinkedList](http://www.baeldung.com/java-linkedlist)
+- [Java List UnsupportedOperationException](http://www.baeldung.com/java-list-unsupported-operation-exception)
+- [Java List Initialization in One Line](https://www.baeldung.com/java-init-list-one-line)
+- [Ways to Iterate Over a List in Java](https://www.baeldung.com/java-iterate-list)
+- [Flattening Nested Collections in Java](http://www.baeldung.com/java-flatten-nested-collections)
+- [Intersection of Two Lists in Java](https://www.baeldung.com/java-lists-intersection)
+- [Determine If All Elements Are the Same in a Java List](https://www.baeldung.com/java-list-all-equal)
+- [List of Primitive Integer Values in Java](https://www.baeldung.com/java-list-primitive-int)
+- [Performance Comparison of Primitive Lists in Java](https://www.baeldung.com/java-list-primitive-performance)
+- [Filtering a Java Collection by a List](https://www.baeldung.com/java-filter-collection-by-list)

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

@@ -0,0 +1,76 @@
+<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-collections-list-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-collections-list-2</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>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>net.sf.trove4j</groupId>
+            <artifactId>trove4j</artifactId>
+            <version>${trove4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>it.unimi.dsi</groupId>
+            <artifactId>fastutil</artifactId>
+            <version>${fastutil.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>colt</groupId>
+            <artifactId>colt</artifactId>
+            <version>${colt.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <commons-collections4.version>4.1</commons-collections4.version>
+        <commons-lang3.version>3.8.1</commons-lang3.version>
+        <assertj.version>3.11.1</assertj.version>
+		<trove4j.version>3.0.2</trove4j.version>
+		<fastutil.version>8.1.0</fastutil.version>
+		<colt.version>1.2.0</colt.version>
+    </properties>
+</project>

core-java-modules/core-java-collections-list-2/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?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>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

core-java-modules/core-java-collections-list/README.md

@@ -3,31 +3,14 @@
 ## Core Java Collections List Cookbooks and Examples
 
 ### Relevant Articles: 
-- [Immutable ArrayList in Java](http://www.baeldung.com/java-immutable-list)
-- [Guide to the Java ArrayList](http://www.baeldung.com/java-arraylist)
 - [Java – Get Random Item/Element From a List](http://www.baeldung.com/java-random-list-element)
 - [Removing all nulls from a List in Java](http://www.baeldung.com/java-remove-nulls-from-list)
 - [Removing all duplicates from a List in Java](http://www.baeldung.com/java-remove-duplicates-from-list)
 - [How to TDD a List Implementation in Java](http://www.baeldung.com/java-test-driven-list)
 - [Iterating Backward Through a List](http://www.baeldung.com/java-list-iterate-backwards)
-- [Add Multiple Items to an Java ArrayList](http://www.baeldung.com/java-add-items-array-list)
 - [Remove the First Element from a List](http://www.baeldung.com/java-remove-first-element-from-list)
 - [How to Find an Element in a List with Java](http://www.baeldung.com/find-list-element-java)
 - [Copy a List to Another List in Java](http://www.baeldung.com/java-copy-list-to-another)
 - [Finding Max/Min of a List or Collection](http://www.baeldung.com/java-collection-min-max)
 - [Collections.emptyList() vs. New List Instance](https://www.baeldung.com/java-collections-emptylist-new-list)
 - [Remove All Occurrences of a Specific Value from a List](https://www.baeldung.com/java-remove-value-from-list)
-- [Check If Two Lists are Equal in Java](http://www.baeldung.com/java-test-a-list-for-ordinality-and-equality)
-- [Java 8 Streams: Find Items From One List Based On Values From Another List](https://www.baeldung.com/java-streams-find-list-items)
-- [A Guide to the Java LinkedList](http://www.baeldung.com/java-linkedlist)
-- [Java List UnsupportedOperationException](http://www.baeldung.com/java-list-unsupported-operation-exception)
-- [Java List Initialization in One Line](https://www.baeldung.com/java-init-list-one-line)
-- [Ways to Iterate Over a List in Java](https://www.baeldung.com/java-iterate-list)
-- [ClassCastException: Arrays$ArrayList cannot be cast to ArrayList](https://www.baeldung.com/java-classcastexception-arrays-arraylist)
-- [Flattening Nested Collections in Java](http://www.baeldung.com/java-flatten-nested-collections)
-- [Intersection of Two Lists in Java](https://www.baeldung.com/java-lists-intersection)
-- [Multi Dimensional ArrayList in Java](https://www.baeldung.com/java-multi-dimensional-arraylist)
-- [Determine If All Elements Are the Same in a Java List](https://www.baeldung.com/java-list-all-equal)
-- [List of Primitive Integer Values in Java](https://www.baeldung.com/java-list-primitive-int)
-- [Performance Comparison of Primitive Lists in Java](https://www.baeldung.com/java-list-primitive-performance)
-- [Filtering a Java Collection by a List](https://www.baeldung.com/java-filter-collection-by-list)

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

@@ -36,42 +36,12 @@
             <version>${lombok.version}</version>
             <scope>provided</scope>
         </dependency>
-
-        <dependency>
-            <groupId>net.sf.trove4j</groupId>
-            <artifactId>trove4j</artifactId>
-            <version>${trove4j.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>it.unimi.dsi</groupId>
-            <artifactId>fastutil</artifactId>
-            <version>${fastutil.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>colt</groupId>
-            <artifactId>colt</artifactId>
-            <version>${colt.version}</version>
-        </dependency>
-
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-core</artifactId>
-            <version>${jmh-core.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-annprocess</artifactId>
-            <version>${jmh-core.version}</version>
-        </dependency>
     </dependencies>
 
     <properties>
         <commons-collections4.version>4.1</commons-collections4.version>
         <commons-lang3.version>3.8.1</commons-lang3.version>
-        <avaitility.version>1.7.0</avaitility.version>
         <assertj.version>3.11.1</assertj.version>
 		<trove4j.version>3.0.2</trove4j.version>
-		<fastutil.version>8.1.0</fastutil.version>
-		<colt.version>1.2.0</colt.version>
     </properties>
 </project>

core-java-modules/core-java-jpms/decoupling-pattern1/consumermodule/pom.xml

@@ -0,0 +1,30 @@
+<?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>consumermodule</artifactId>
+    <packaging>jar</packaging>
+    <version>1.0</version>
+    
+    <parent>
+        <groupId>com.baeldung.decoupling-pattern1</groupId>
+        <artifactId>decoupling-pattern1</artifactId>
+        <version>1.0</version>
+    </parent>
+    
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+    
+    <dependencies>
+        <dependency>
+            <groupId>com.baeldung.servicemodule</groupId>
+            <artifactId>servicemodule</artifactId>
+            <version>1.0</version>           
+        </dependency>
+    </dependencies>
+</project>

core-java-modules/core-java-jpms/decoupling-pattern1/consumermodule/src/main/java/com/baeldung/consumermodule/Application.java

@@ -0,0 +1,13 @@
+package com.baeldung.consumermodule;
+
+import com.baeldung.servicemodule.external.TextService;
+import com.baeldung.servicemodule.external.TextServiceFactory;
+
+public class Application {
+    
+    public static void main(String args[]) {
+        TextService textService = TextServiceFactory.getTextService("lowercase");
+        System.out.println(textService.processText("Hello from Baeldung!"));
+    }
+    
+}

core-java-modules/core-java-jpms/decoupling-pattern1/consumermodule/src/main/java/module-info.java

@@ -0,0 +1,3 @@
+module com.baeldung.consumermodule {
+    requires com.baeldung.servicemodule;
+}

core-java-modules/core-java-jpms/decoupling-pattern1/pom.xml

@@ -0,0 +1,35 @@
+<?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>
+    <groupId>com.baeldung.decoupling-pattern1</groupId>
+    <artifactId>decoupling-pattern1</artifactId>
+    <version>1.0</version>
+    <packaging>pom</packaging>
+    
+    <modules>
+        <module>servicemodule</module>
+        <module>consumermodule</module>
+    </modules>
+    
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-compiler-plugin</artifactId>
+                    <version>3.8.0</version>
+                    <configuration>
+                        <source>11</source>
+                        <target>11</target>
+                    </configuration>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+    
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+</project>

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/pom.xml

@@ -0,0 +1,24 @@
+<?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>
+    
+    <groupId>com.baeldung.servicemodule</groupId>
+    <artifactId>servicemodule</artifactId>
+    <packaging>jar</packaging>
+    
+    <parent>
+        <groupId>com.baeldung.decoupling-pattern1</groupId>
+        <artifactId>decoupling-pattern1</artifactId>
+        <version>1.0</version>
+    </parent>
+    
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+   
+</project>

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/src/main/java/com/baeldung/servicemodule/external/TextService.java

@@ -0,0 +1,7 @@
+package com.baeldung.servicemodule.external;
+
+public interface TextService {
+    
+    String processText(String text);
+    
+}

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/src/main/java/com/baeldung/servicemodule/external/TextServiceFactory.java

@@ -0,0 +1,14 @@
+package com.baeldung.servicemodule.external;
+
+import com.baeldung.servicemodule.internal.LowercaseTextService;
+import com.baeldung.servicemodule.internal.UppercaseTextService;
+
+public class TextServiceFactory {
+    
+    private TextServiceFactory() {}
+    
+    public static TextService getTextService(String name) {
+        return name.equalsIgnoreCase("lowercase") ? new LowercaseTextService(): new UppercaseTextService();
+    }
+    
+}

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/src/main/java/com/baeldung/servicemodule/internal/LowercaseTextService.java

@@ -0,0 +1,12 @@
+package com.baeldung.servicemodule.internal;
+
+import com.baeldung.servicemodule.external.TextService;
+
+public class LowercaseTextService implements TextService {
+
+    @Override
+    public String processText(String text) {
+        return text.toLowerCase();
+    }
+    
+}

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/src/main/java/com/baeldung/servicemodule/internal/UppercaseTextService.java

@@ -0,0 +1,12 @@
+package com.baeldung.servicemodule.internal;
+
+import com.baeldung.servicemodule.external.TextService;
+
+public class UppercaseTextService implements TextService {
+    
+    @Override
+    public String processText(String text) {
+        return text.toUpperCase();
+    }
+    
+}

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/src/main/java/module-info.java

@@ -0,0 +1,3 @@
+module com.baeldung.servicemodule {
+    exports com.baeldung.servicemodule.external;
+}

core-java-modules/core-java-jpms/decoupling-pattern2/consumermodule/pom.xml

@@ -0,0 +1,38 @@
+<?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">
+    <parent>
+        <artifactId>com.baeldung.decoupling-pattern2</artifactId>
+        <groupId>decoupling-pattern2</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.baeldung.consumermodule</groupId>
+    <artifactId>consumermodule</artifactId>
+    <version>1.0</version>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.baeldung.servicemodule</groupId>
+            <artifactId>servicemodule</artifactId>
+            <version>1.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.baeldung.providermodule</groupId>
+            <artifactId>providermodule</artifactId>
+            <version>1.0</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

core-java-modules/core-java-jpms/decoupling-pattern2/consumermodule/src/main/java/com/baeldung/consumermodule/Application.java

@@ -0,0 +1,15 @@
+package com.baeldung.consumermodule;
+
+import com.baeldung.servicemodule.TextService;
+
+import java.util.ServiceLoader;
+
+public class Application {
+
+    public static void main(String[] args) {
+        ServiceLoader<TextService> services = ServiceLoader.load(TextService.class);
+        for (final TextService service: services) {
+            System.out.println("The service " + service.getClass().getSimpleName() + " says: " + service.parseText("Hello from Baeldung!"));
+        }
+    }
+}

core-java-modules/core-java-jpms/decoupling-pattern2/consumermodule/src/main/java/module-info.java

@@ -0,0 +1,4 @@
+module com.baeldung.consumermodule {
+    requires com.baeldung.servicemodule;
+    uses com.baeldung.servicemodule.TextService;
+}

core-java-modules/core-java-jpms/decoupling-pattern2/pom.xml

@@ -0,0 +1,34 @@
+<?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>
+
+    <groupId>com.baeldung.decoupling-pattern2</groupId>
+    <artifactId>decoupling-pattern2</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <packaging>pom</packaging>
+
+    <modules>
+        <module>servicemodule</module>
+        <module>providermodule</module>
+        <module>consumermodule</module>
+    </modules>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-compiler-plugin</artifactId>
+                    <version>3.8.0</version>
+                    <configuration>
+                        <source>11</source>
+                        <target>11</target>
+                    </configuration>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+
+</project>

core-java-modules/core-java-jpms/decoupling-pattern2/providermodule/pom.xml

@@ -0,0 +1,34 @@
+<?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>
+    <groupId>com.baeldung.providermodule</groupId>
+    <artifactId>providermodule</artifactId>
+    <version>1.0</version>
+
+    <parent>
+        <artifactId>com.baeldung.decoupling-pattern2</artifactId>
+        <groupId>decoupling-pattern2</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.baeldung.servicemodule</groupId>
+            <artifactId>servicemodule</artifactId>
+            <version>1.0</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

core-java-modules/core-java-jpms/decoupling-pattern2/providermodule/src/main/java/com/baeldung/providermodule/LowercaseTextService.java

@@ -0,0 +1,10 @@
+package com.baeldung.providermodule;
+
+import com.baeldung.servicemodule.TextService;
+
+public class LowercaseTextService implements TextService {
+    @Override
+    public String parseText(String text) {
+        return text.toLowerCase();
+    }
+}

core-java-modules/core-java-jpms/decoupling-pattern2/providermodule/src/main/java/module-info.java

@@ -0,0 +1,4 @@
+module com.baeldung.providermodule {
+    requires com.baeldung.servicemodule;
+    provides com.baeldung.servicemodule.TextService with com.baeldung.providermodule.LowercaseTextService;
+}

core-java-modules/core-java-jpms/decoupling-pattern2/servicemodule/pom.xml

@@ -0,0 +1,25 @@
+<?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>
+    <parent>
+        <artifactId>>com.baeldung.decoupling-pattern2</artifactId>
+        <groupId>decoupling-pattern2</groupId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <groupId>com.baeldung.servicemodule</groupId>
+    <artifactId>servicemodule</artifactId>
+    <version>1.0</version>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

core-java-modules/core-java-jpms/decoupling-pattern2/servicemodule/src/main/java/com/baeldung/servicemodule/TextService.java

@@ -0,0 +1,6 @@
+package com.baeldung.servicemodule;
+
+public interface TextService {
+
+    String parseText(String text);
+}

core-java-modules/core-java-jpms/decoupling-pattern2/servicemodule/src/main/java/module-info.java

@@ -0,0 +1,3 @@
+module com.baeldung.servicemodule {
+    exports com.baeldung.servicemodule;
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/AmountBasedDiscountPolicy.java

@@ -0,0 +1,15 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import org.joda.money.CurrencyUnit;
+import org.joda.money.Money;
+
+public class AmountBasedDiscountPolicy implements DiscountPolicy {
+    @Override
+    public double discount(Order order) {
+        if (order.totalCost()
+            .isGreaterThan(Money.of(CurrencyUnit.USD, 500.00))) {
+            return 0.10;
+        } else
+            return 0;
+    }
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/DiscountPolicy.java

@@ -0,0 +1,5 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+public interface DiscountPolicy {
+    double discount(Order order);
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/FlatDiscountPolicy.java

@@ -0,0 +1,8 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+public class FlatDiscountPolicy implements DiscountPolicy {
+    @Override
+    public double discount(Order order) {
+        return 0.01;
+    }
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/Order.java

@@ -0,0 +1,29 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import java.math.RoundingMode;
+import java.util.List;
+
+import org.joda.money.Money;
+
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.visitor.OrderVisitor;
+import com.baeldung.ddd.order.doubledispatch.visitor.Visitable;
+
+public class Order extends com.baeldung.ddd.order.Order implements Visitable<OrderVisitor> {
+    public Order(List<OrderLine> orderLines) {
+        super(orderLines);        
+    }
+
+    public Money totalCost(SpecialDiscountPolicy discountPolicy) {
+        return totalCost().multipliedBy(1 - applyDiscountPolicy(discountPolicy), RoundingMode.HALF_UP);
+    }
+
+    protected double applyDiscountPolicy(SpecialDiscountPolicy discountPolicy) {
+        return discountPolicy.discount(this);
+    }
+    
+    @Override
+    public void accept(OrderVisitor visitor) {
+        visitor.visit(this);        
+    }
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/SpecialDiscountPolicy.java

@@ -0,0 +1,5 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+public interface SpecialDiscountPolicy extends DiscountPolicy {
+    double discount(SpecialOrder order);
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/SpecialOrder.java

@@ -0,0 +1,36 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import java.util.List;
+
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.visitor.OrderVisitor;
+
+public class SpecialOrder extends Order {
+
+    private boolean eligibleForExtraDiscount;
+
+    public SpecialOrder(List<OrderLine> orderLines) {
+        super(orderLines);
+        this.eligibleForExtraDiscount = false;
+    }
+
+    public SpecialOrder(List<OrderLine> orderLines, boolean eligibleForSpecialDiscount) {
+        super(orderLines);
+        this.eligibleForExtraDiscount = eligibleForSpecialDiscount;
+    }
+
+    public boolean isEligibleForExtraDiscount() {
+        return eligibleForExtraDiscount;
+    }
+
+    @Override
+    protected double applyDiscountPolicy(SpecialDiscountPolicy discountPolicy) {
+        return discountPolicy.discount(this);
+    }
+
+    @Override
+    public void accept(OrderVisitor visitor) {
+        visitor.visit(this);
+    }
+
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/visitor/HtmlOrderViewCreator.java

@@ -0,0 +1,24 @@
+package com.baeldung.ddd.order.doubledispatch.visitor;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.doubledispatch.SpecialOrder;
+
+public class HtmlOrderViewCreator implements OrderVisitor {
+    
+    private String html;
+    
+    public String getHtml() {
+        return html;
+    }
+
+    @Override
+    public void visit(Order order) {
+        html = String.format("<p>Regular order total cost: %s</p>", order.totalCost());
+    }
+
+    @Override
+    public void visit(SpecialOrder order) {
+        html = String.format("<h1>Special Order</h1><p>total cost: %s</p>", order.totalCost());
+    }
+
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/visitor/OrderVisitor.java

@@ -0,0 +1,9 @@
+package com.baeldung.ddd.order.doubledispatch.visitor;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.doubledispatch.SpecialOrder;
+
+public interface OrderVisitor {
+    void visit(Order order);
+    void visit(SpecialOrder order);
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/visitor/Visitable.java

@@ -0,0 +1,5 @@
+package com.baeldung.ddd.order.doubledispatch.visitor;
+
+public interface Visitable<V> {
+    void accept(V visitor);
+}

ddd/src/main/java/com/baeldung/ddd/order/jpa/JpaOrder.java

@@ -92,7 +92,7 @@ class JpaOrder {
     }
 
     void removeLineItem(int line) {
-        JpaOrderLine removedLine = orderLines.remove(line);
+        orderLines.remove(line);
     }
 
     void setCurrencyUnit(String currencyUnit) {

ddd/src/main/java/com/baeldung/ddd/order/jpa/JpaProduct.java

@@ -15,7 +15,7 @@ class JpaProduct {
     public JpaProduct(BigDecimal price, String currencyUnit) {
         super();
         this.price = price;
-        currencyUnit = currencyUnit;
+        this.currencyUnit = currencyUnit;
     }
 
     @Override

ddd/src/test/java/com/baeldung/ddd/order/OrderFixtureUtils.java

@@ -0,0 +1,17 @@
+package com.baeldung.ddd.order;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.joda.money.CurrencyUnit;
+import org.joda.money.Money;
+
+public class OrderFixtureUtils {
+    public static List<OrderLine> anyOrderLines() {
+        return Arrays.asList(new OrderLine(new Product(Money.of(CurrencyUnit.USD, 100)), 1));
+    }
+
+    public static List<OrderLine> orderLineItemsWorthNDollars(int totalCost) {
+        return Arrays.asList(new OrderLine(new Product(Money.of(CurrencyUnit.USD, totalCost)), 1));
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/DoubleDispatchDiscountPolicyUnitTest.java

@@ -0,0 +1,77 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.joda.money.CurrencyUnit;
+import org.joda.money.Money;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.OrderFixtureUtils;
+
+public class DoubleDispatchDiscountPolicyUnitTest {
+    // @formatter:off
+    @DisplayName(
+        "given regular order with items worth $100 total, " +
+        "when apply 10% discount policy, " +
+        "then cost after discount is $90"
+        )
+    // @formatter:on
+    @Test
+    void test() throws Exception {
+        // given
+        Order order = new Order(OrderFixtureUtils.orderLineItemsWorthNDollars(100));
+        SpecialDiscountPolicy discountPolicy = new SpecialDiscountPolicy() {
+
+            @Override
+            public double discount(Order order) {
+                return 0.10;
+            }
+
+            @Override
+            public double discount(SpecialOrder order) {
+                return 0;
+            }
+        };
+
+        // when
+        Money totalCostAfterDiscount = order.totalCost(discountPolicy);
+
+        // then
+        assertThat(totalCostAfterDiscount).isEqualTo(Money.of(CurrencyUnit.USD, 90));
+    }
+
+    // @formatter:off
+    @DisplayName(
+        "given special order eligible for extra discount with items worth $100 total, " +
+        "when apply 20% discount policy for extra discount orders, " +
+        "then cost after discount is $80"
+        )
+    // @formatter:on
+    @Test
+    void test1() throws Exception {
+        // given
+        boolean eligibleForExtraDiscount = true;
+        Order order = new SpecialOrder(OrderFixtureUtils.orderLineItemsWorthNDollars(100), eligibleForExtraDiscount);
+        SpecialDiscountPolicy discountPolicy = new SpecialDiscountPolicy() {
+
+            @Override
+            public double discount(Order order) {
+                return 0;
+            }
+
+            @Override
+            public double discount(SpecialOrder order) {
+                if (order.isEligibleForExtraDiscount())
+                    return 0.20;
+                return 0.10;
+            }
+        };
+
+        // when
+        Money totalCostAfterDiscount = order.totalCost(discountPolicy);
+
+        // then
+        assertThat(totalCostAfterDiscount).isEqualTo(Money.of(CurrencyUnit.USD, 80.00));
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/HtmlOrderViewCreatorUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.OrderFixtureUtils;
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.visitor.HtmlOrderViewCreator;
+
+public class HtmlOrderViewCreatorUnitTest {
+    // @formatter:off 
+    @DisplayName(
+            "given collection of regular and special orders, " +
+            "when create HTML view using visitor for each order, " +
+            "then the dedicated view is created for each order"   
+        )
+    // @formatter:on
+    @Test
+    void test() throws Exception {
+        // given
+        List<OrderLine> anyOrderLines = OrderFixtureUtils.anyOrderLines();
+        List<Order> orders = Arrays.asList(new Order(anyOrderLines), new SpecialOrder(anyOrderLines));
+        HtmlOrderViewCreator htmlOrderViewCreator = new HtmlOrderViewCreator();
+
+        // when
+        orders.get(0)
+            .accept(htmlOrderViewCreator);
+        String regularOrderHtml = htmlOrderViewCreator.getHtml();
+        orders.get(1)
+            .accept(htmlOrderViewCreator);
+        String specialOrderHtml = htmlOrderViewCreator.getHtml();
+
+        // then
+        assertThat(regularOrderHtml).containsPattern("<p>Regular order total cost: .*</p>");
+        assertThat(specialOrderHtml).containsPattern("<h1>Special Order</h1><p>total cost: .*</p>");
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/MethodOverloadExampleUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.OrderFixtureUtils;
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.SpecialDiscountPolicy;
+import com.baeldung.ddd.order.doubledispatch.SpecialOrder;
+
+public class MethodOverloadExampleUnitTest {
+// @formatter:off
+@DisplayName(
+    "given discount policy accepting special orders, " +
+    "when apply the policy on special order declared as regular order, " +
+    "then regular discount method is used"
+    )
+// @formatter:on    
+    @Test
+    void test() throws Exception {
+        // given
+        SpecialDiscountPolicy specialPolicy = new SpecialDiscountPolicy() {
+            @Override
+            public double discount(Order order) {
+                return 0.01;
+            }
+
+            @Override
+            public double discount(SpecialOrder order) {
+                return 0.10;
+            }
+        };
+        Order specialOrder = new SpecialOrder(anyOrderLines());
+
+        // when
+        double discount = specialPolicy.discount(specialOrder);
+
+        // then
+        assertThat(discount).isEqualTo(0.01);
+    }
+
+    private List<OrderLine> anyOrderLines() {
+        return OrderFixtureUtils.anyOrderLines();
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/SingleDispatchDiscountPolicyUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.OrderFixtureUtils;
+
+public class SingleDispatchDiscountPolicyUnitTest {
+    // @formatter:off
+    @DisplayName(
+        "given two discount policies, " +
+        "when use these policies, " +
+        "then single dispatch chooses the implementation based on runtime type"
+        )
+    // @formatter:on    
+    @Test
+    void test() throws Exception {
+        // given
+        DiscountPolicy flatPolicy = new FlatDiscountPolicy();
+        DiscountPolicy amountPolicy = new AmountBasedDiscountPolicy();
+        Order orderWorth501Dollars = orderWorthNDollars(501);
+
+        // when
+        double flatDiscount = flatPolicy.discount(orderWorth501Dollars);
+        double amountDiscount = amountPolicy.discount(orderWorth501Dollars);
+
+        // then
+        assertThat(flatDiscount).isEqualTo(0.01);
+        assertThat(amountDiscount).isEqualTo(0.1);
+    }
+
+    private Order orderWorthNDollars(int totalCost) {
+        return new Order(OrderFixtureUtils.orderLineItemsWorthNDollars(totalCost));
+    }
+}

guava-collections-set/README.md

@@ -1,4 +1,8 @@
+# Guava
 
-### Relevant Articles: 
+## Relevant Articles:
 
+- [Guava – Sets](http://www.baeldung.com/guava-sets)
+- [Guide to Guava RangeSet](http://www.baeldung.com/guava-rangeset)
+- [Guava Set + Function = Map](http://www.baeldung.com/guava-set-function-map-tutorial)
 - [Guide to Guava Multiset](https://www.baeldung.com/guava-multiset)

guava-collections-set/src/test/java/org/baeldung/guava/GuavaMapFromSet.java

@@ -1,14 +1,9 @@
 package org.baeldung.guava;
 
-import java.util.AbstractMap;
-import java.util.AbstractSet;
-import java.util.Iterator;
-import java.util.Map;
-import java.util.Set;
-import java.util.WeakHashMap;
-
 import com.google.common.base.Function;
 
+import java.util.*;
+
 public class GuavaMapFromSet<K, V> extends AbstractMap<K, V> {
 
     private class SingleEntry implements Entry<K, V> {

guava-collections-set/src/test/java/org/baeldung/guava/GuavaMapFromSetUnitTest.java

@@ -1,15 +1,14 @@
 package org.baeldung.guava;
 
-import static org.junit.Assert.assertTrue;
+import com.google.common.base.Function;
+import org.junit.Test;
 
 import java.util.Arrays;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
 
-import org.junit.Test;
+import static org.junit.Assert.assertTrue;
-
-import com.google.common.base.Function;
 
 public class GuavaMapFromSetUnitTest {
 

guava-collections-set/src/test/java/org/baeldung/guava/GuavaRangeSetUnitTest.java

@@ -1,13 +1,12 @@
 package org.baeldung.guava;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.assertFalse;
-import org.junit.Test;
 import com.google.common.collect.ImmutableRangeSet;
 import com.google.common.collect.Range;
 import com.google.common.collect.RangeSet;
 import com.google.common.collect.TreeRangeSet;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
 
 public class GuavaRangeSetUnitTest {
 
@@ -122,6 +121,5 @@ public class GuavaRangeSetUnitTest {
 	    .add(Range.closed(0, 2))
 	    .add(Range.closed(3, 5))
 	    .add(Range.closed(5, 8)).build();
-
     }
 }

guava-collections-set/src/test/java/org/baeldung/guava/GuavaSetOperationsUnitTest.java

@@ -0,0 +1,131 @@
+package org.baeldung.guava;
+
+import com.google.common.base.Function;
+import com.google.common.base.Joiner;
+import com.google.common.collect.*;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Set;
+
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+public class GuavaSetOperationsUnitTest {
+
+    @Test
+    public void whenCalculatingUnionOfSets_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
+        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
+
+        final Set<Character> union = Sets.union(first, second);
+        assertThat(union, containsInAnyOrder('a', 'b', 'c', 'd'));
+    }
+
+    @Test
+    public void whenCalculatingCartesianProductOfSets_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b');
+        final Set<Character> second = ImmutableSet.of('c', 'd');
+        final Set<List<Character>> result = Sets.cartesianProduct(ImmutableList.of(first, second));
+
+        final Function<List<Character>, String> func = new Function<List<Character>, String>() {
+            @Override
+            public final String apply(final List<Character> input) {
+                return Joiner
+                  .on(" ").join(input);
+            }
+        };
+
+        final Iterable<String> joined = Iterables.transform(result, func);
+        assertThat(joined, containsInAnyOrder("a c", "a d", "b c", "b d"));
+    }
+
+    @Test
+    public void whenCalculatingSetIntersection_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
+        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
+
+        final Set<Character> intersection = Sets.intersection(first, second);
+        assertThat(intersection, containsInAnyOrder('b', 'c'));
+    }
+
+    @Test
+    public void whenCalculatingSetSymmetricDifference_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
+        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
+
+        final Set<Character> intersection = Sets.symmetricDifference(first, second);
+        assertThat(intersection, containsInAnyOrder('a', 'd'));
+    }
+
+    @Test
+    public void whenCalculatingPowerSet_thenCorrect() {
+        final Set<Character> chars = ImmutableSet.of('a', 'b');
+        final Set<Set<Character>> result = Sets.powerSet(chars);
+
+        final Set<Character> empty = ImmutableSet.<Character> builder().build();
+        final Set<Character> a = ImmutableSet.of('a');
+        final Set<Character> b = ImmutableSet.of('b');
+        final Set<Character> aB = ImmutableSet.of('a', 'b');
+
+        assertThat(result, contains(empty, a, b, aB));
+    }
+
+    @Test
+    public void whenCreatingRangeOfIntegersSet_thenCreated() {
+        final int start = 10;
+        final int end = 30;
+        final ContiguousSet<Integer> set = ContiguousSet.create(Range.closed(start, end), DiscreteDomain.integers());
+
+        assertEquals(21, set.size());
+        assertEquals(10, set.first().intValue());
+        assertEquals(30, set.last().intValue());
+    }
+
+    @Test
+    public void whenUsingRangeSet_thenCorrect() {
+        final RangeSet<Integer> rangeSet = TreeRangeSet.create();
+        rangeSet.add(Range.closed(1, 10));
+        rangeSet.add(Range.closed(12, 15));
+
+        assertEquals(2, rangeSet.asRanges().size());
+
+        rangeSet.add(Range.closed(10, 12));
+        assertTrue(rangeSet.encloses(Range.closed(1, 15)));
+        assertEquals(1, rangeSet.asRanges().size());
+    }
+
+    @Test
+    public void whenInsertDuplicatesInMultiSet_thenInserted() {
+        final Multiset<String> names = HashMultiset.create();
+        names.add("John");
+        names.add("Adam", 3);
+        names.add("John");
+
+        assertEquals(2, names.count("John"));
+        names.remove("John");
+        assertEquals(1, names.count("John"));
+
+        assertEquals(3, names.count("Adam"));
+        names.remove("Adam", 2);
+        assertEquals(1, names.count("Adam"));
+    }
+
+    @Test
+    public void whenGetTopOcurringElementsWithMultiSet_thenCorrect() {
+        final Multiset<String> names = HashMultiset.create();
+        names.add("John");
+        names.add("Adam", 5);
+        names.add("Jane");
+        names.add("Tom", 2);
+
+        final Set<String> sorted = Multisets.copyHighestCountFirst(names).elementSet();
+        final List<String> topTwo = Lists.newArrayList(sorted).subList(0, 2);
+        assertEquals(2, topTwo.size());
+        assertEquals("Adam", topTwo.get(0));
+        assertEquals("Tom", topTwo.get(1));
+    }
+}

guava-collections/README.md

@@ -11,13 +11,10 @@
 - [Filtering and Transforming Collections in Guava](http://www.baeldung.com/guava-filter-and-transform-a-collection)
 - [Guava – Join and Split Collections](http://www.baeldung.com/guava-joiner-and-splitter-tutorial)
 - [Guava – Lists](http://www.baeldung.com/guava-lists)
-- [Guava – Sets](http://www.baeldung.com/guava-sets)
 - [Guava – Maps](http://www.baeldung.com/guava-maps)
 - [Guide to Guava Multimap](http://www.baeldung.com/guava-multimap)
-- [Guide to Guava RangeSet](http://www.baeldung.com/guava-rangeset)
 - [Guide to Guava RangeMap](http://www.baeldung.com/guava-rangemap)
 - [Guide to Guava MinMaxPriorityQueue and EvictingQueue](http://www.baeldung.com/guava-minmax-priority-queue-and-evicting-queue)
 - [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
-- [Guava Set + Function = Map](http://www.baeldung.com/guava-set-function-map-tutorial)
 - [Guide to Guava Table](http://www.baeldung.com/guava-table)
 - [Guide to Guava ClassToInstanceMap](http://www.baeldung.com/guava-class-to-instance-map)

guava-collections/src/test/java/org/baeldung/guava/GuavaCollectionTypesUnitTest.java

@@ -111,120 +111,6 @@ public class GuavaCollectionTypesUnitTest {
         assertThat(immutable, contains("John", "Adam", "Jane", "Tom"));
     }
 
-    // sets
-
-    @Test
-    public void whenCalculateUnionOfSets_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
-        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
-
-        final Set<Character> union = Sets.union(first, second);
-        assertThat(union, containsInAnyOrder('a', 'b', 'c', 'd'));
-    }
-
-    @Test
-    public void whenCalculateSetsProduct_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b');
-        final Set<Character> second = ImmutableSet.of('c', 'd');
-        final Set<List<Character>> result = Sets.cartesianProduct(ImmutableList.of(first, second));
-
-        final Function<List<Character>, String> func = new Function<List<Character>, String>() {
-            @Override
-            public final String apply(final List<Character> input) {
-                return Joiner.on(" ").join(input);
-            }
-        };
-
-        final Iterable<String> joined = Iterables.transform(result, func);
-        assertThat(joined, containsInAnyOrder("a c", "a d", "b c", "b d"));
-    }
-
-    @Test
-    public void whenCalculatingSetIntersection_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
-        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
-
-        final Set<Character> intersection = Sets.intersection(first, second);
-        assertThat(intersection, containsInAnyOrder('b', 'c'));
-    }
-
-    @Test
-    public void whenCalculatingSetSymmetricDifference_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
-        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
-
-        final Set<Character> intersection = Sets.symmetricDifference(first, second);
-        assertThat(intersection, containsInAnyOrder('a', 'd'));
-    }
-
-    @Test
-    public void whenCalculatingPowerSet_thenCorrect() {
-        final Set<Character> chars = ImmutableSet.of('a', 'b');
-        final Set<Set<Character>> result = Sets.powerSet(chars);
-
-        final Set<Character> empty = ImmutableSet.<Character> builder().build();
-        final Set<Character> a = ImmutableSet.of('a');
-        final Set<Character> b = ImmutableSet.of('b');
-        final Set<Character> aB = ImmutableSet.of('a', 'b');
-
-        assertThat(result, contains(empty, a, b, aB));
-    }
-
-    @Test
-    public void whenCreateRangeOfIntegersSet_thenCreated() {
-        final int start = 10;
-        final int end = 30;
-        final ContiguousSet<Integer> set = ContiguousSet.create(Range.closed(start, end), DiscreteDomain.integers());
-
-        assertEquals(21, set.size());
-        assertEquals(10, set.first().intValue());
-        assertEquals(30, set.last().intValue());
-    }
-
-    @Test
-    public void whenCreateRangeSet_thenCreated() {
-        final RangeSet<Integer> rangeSet = TreeRangeSet.create();
-        rangeSet.add(Range.closed(1, 10));
-        rangeSet.add(Range.closed(12, 15));
-
-        assertEquals(2, rangeSet.asRanges().size());
-
-        rangeSet.add(Range.closed(10, 12));
-        assertTrue(rangeSet.encloses(Range.closed(1, 15)));
-        assertEquals(1, rangeSet.asRanges().size());
-    }
-
-    @Test
-    public void whenInsertDuplicatesInMultiSet_thenInserted() {
-        final Multiset<String> names = HashMultiset.create();
-        names.add("John");
-        names.add("Adam", 3);
-        names.add("John");
-
-        assertEquals(2, names.count("John"));
-        names.remove("John");
-        assertEquals(1, names.count("John"));
-
-        assertEquals(3, names.count("Adam"));
-        names.remove("Adam", 2);
-        assertEquals(1, names.count("Adam"));
-    }
-
-    @Test
-    public void whenGetTopUsingMultiSet_thenCorrect() {
-        final Multiset<String> names = HashMultiset.create();
-        names.add("John");
-        names.add("Adam", 5);
-        names.add("Jane");
-        names.add("Tom", 2);
-
-        final Set<String> sorted = Multisets.copyHighestCountFirst(names).elementSet();
-        final List<String> topTwo = Lists.newArrayList(sorted).subList(0, 2);
-        assertEquals(2, topTwo.size());
-        assertEquals("Adam", topTwo.get(0));
-        assertEquals("Tom", topTwo.get(1));
-    }
-
     @Test
     public void whenCreateImmutableMap_thenCreated() {
         final Map<String, Integer> salary = ImmutableMap.<String, Integer> builder().put("John", 1000).put("Jane", 1500).put("Adam", 2000).put("Tom", 2000).build();

java-strings-2/README.MD

@@ -2,3 +2,4 @@
 
 - [Java Localization – Formatting Messages](https://www.baeldung.com/java-localization-messages-formatting)
 - [Check If a String Contains a Substring](https://www.baeldung.com/java-string-contains-substring)
+- [Removing Stopwords from a String in Java](https://www.baeldung.com/java-string-remove-stopwords)

java-strings-2/src/test/java/com/baeldung/initialization/StringInitializationUnitTest.java

@@ -0,0 +1,58 @@
+package com.baeldung.initialization;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+
+import org.junit.Test;
+
+public class StringInitializationUnitTest {
+
+    private String fieldString;
+
+    void printDeclaredOnlyString() {
+        String localVarString = null;
+
+        System.out.println(localVarString); // compilation error
+        System.out.println(fieldString);
+    }
+
+    @Test
+    public void givenDeclaredFeldStringAndNullString_thenCompareEquals() {
+        String localVarString = null;
+
+        assertEquals(fieldString, localVarString);
+    }
+
+    @Test
+    public void givenTwoStringsWithSameLiteral_thenCompareReferencesEquals() {
+        String literalOne = "Baeldung";
+        String literalTwo = "Baeldung";
+
+        assertTrue(literalOne == literalTwo);
+    }
+
+    @Test
+    public void givenTwoStringsUsingNew_thenCompareReferencesNotEquals() {
+        String newStringOne = new String("Baeldung");
+        String newStringTwo = new String("Baeldung");
+
+        assertFalse(newStringOne == newStringTwo);
+    }
+
+    @Test
+    public void givenEmptyLiteralStringsAndNewObject_thenCompareEquals() {
+        String emptyLiteral = "";
+        String emptyNewString = new String("");
+
+        assertEquals(emptyLiteral, emptyNewString);
+    }
+
+    @Test
+    public void givenEmptyStringObjects_thenCompareEquals() {
+        String emptyNewString = new String("");
+        String emptyNewStringTwo = new String();
+
+        assertEquals(emptyNewString, emptyNewStringTwo);
+    }
+}

jee-7/src/test/java/com/baeldung/singleton/CarServiceIntegrationTest.java

@@ -10,6 +10,10 @@ import java.util.Map;
 import java.util.UUID;
 
 import javax.ejb.EJB;
+import javax.enterprise.context.spi.CreationalContext;
+import javax.enterprise.inject.spi.Bean;
+import javax.enterprise.inject.spi.BeanManager;
+import javax.enterprise.inject.spi.CDI;
 import javax.inject.Inject;
 
 import org.jboss.arquillian.container.test.api.Deployment;
@@ -48,67 +52,30 @@ public class CarServiceIntegrationTest {
     @EJB
     private CarServiceEjbSingleton carServiceEjbSingleton;
     
-    private static Map<String, UUID> idMap = new HashMap<>();
+    @Test
-
+    public void givenASingleton_whenGetBeanIsCalledTwice_thenTheSameInstanceIsReturned() {       
-    @Before
+        CarServiceSingleton one = getBean(CarServiceSingleton.class);
-    public void setUp() {
+        CarServiceSingleton two = getBean(CarServiceSingleton.class);
-        // populate idMap only on first run
+        assertTrue(one == two);
-        if (idMap.isEmpty()) {
-            LOG.info("setUp::carServiceBean: {}", carServiceBean.getId());
-            idMap.put("carServiceBeanId", carServiceBean.getId());
-
-            LOG.info("setUp::carServiceSingleton: {}", carServiceSingleton.getId());
-            idMap.put("carServiceSingletonId", carServiceSingleton.getId());
-
-            LOG.info("setUp::carServiceEjbSingleton: {}", carServiceEjbSingleton.getId());
-            idMap.put("carServiceEjbSingletonId", carServiceEjbSingleton.getId());
-        }
     }
     
     @Test
-    public void givenRun1_whenGetId_thenSingletonIdEqual() {
+    public void givenAPojo_whenGetBeanIsCalledTwice_thenDifferentInstancesAreReturned() {       
-        int testRun = 1;
+        CarServiceBean one = getBean(CarServiceBean.class);
+        CarServiceBean two = getBean(CarServiceBean.class);
+        assertTrue(one != two);
+    }
 
-        assertNotNull(carServiceBean);
+    @SuppressWarnings("unchecked")
-        assertNotNull(carServiceSingleton);
+    private <T> T getBean(Class<T> beanClass) {
-        assertNotNull(carServiceEjbSingleton);
+        BeanManager bm = CDI.current().getBeanManager();
-
+        Bean<T> bean = (Bean<T>) bm.getBeans(beanClass).iterator().next();
-        UUID carServiceBeanId = carServiceBean.getId();
+        CreationalContext<T> ctx = bm.createCreationalContext(bean);
-        assertEquals(idMap.get("carServiceBeanId"), carServiceBeanId);
+        return (T) bm.getReference(bean, beanClass, ctx);
-        LOG.info("Test run {}::carServiceBeanId: {}", testRun, carServiceBeanId);
-
-        UUID carServiceSingletonId = carServiceSingleton.getId();
-        assertEquals(idMap.get("carServiceSingletonId"), carServiceSingletonId);
-        LOG.info("Test run {}::carServiceSingletonId: {}", testRun, carServiceSingletonId);
-
-        UUID carServiceEjbSingletonId = carServiceEjbSingleton.getId();
-        assertEquals(idMap.get("carServiceEjbSingletonId"), carServiceEjbSingletonId);
-        LOG.info("Test run {}::carServiceEjbSingletonId: {}", testRun, carServiceEjbSingletonId);
     }
 
     @Test
-    public void givenRun2_whenGetId_thenSingletonIdEqual() {
+    public void givenCDI_whenConcurrentAccess_thenLockingIsNotProvided() {
-        int testRun = 2;
-
-        assertNotNull(carServiceBean);
-        assertNotNull(carServiceSingleton);
-        assertNotNull(carServiceEjbSingleton);
-
-        UUID carServiceBeanId = carServiceBean.getId();
-        assertNotEquals(idMap.get("carServiceBeanId"), carServiceBeanId);
-        LOG.info("Test run {}::carServiceBeanId: {}", testRun, carServiceBeanId);
-
-        UUID carServiceSingletonId = carServiceSingleton.getId();
-        assertEquals(idMap.get("carServiceSingletonId"), carServiceSingletonId);
-        LOG.info("Test run {}::carServiceSingletonId: {}", testRun, carServiceSingletonId);
-
-        UUID carServiceEjbSingletonId = carServiceEjbSingleton.getId();
-        assertEquals(idMap.get("carServiceEjbSingletonId"), carServiceEjbSingletonId);
-        LOG.info("Test run {}::carServiceEjbSingletonId: {}", testRun, carServiceEjbSingletonId);
-    }
-
-    @Test
-    public void givenRun3_whenSingleton_thenNoLocking() {
         for (int i = 0; i < 10; i++) {
             new Thread(new Runnable() {
                 @Override
@@ -124,7 +91,7 @@ public class CarServiceIntegrationTest {
     }
     
     @Test
-    public void givenRun4_whenEjb_thenLocking() {
+    public void givenEJB_whenConcurrentAccess_thenLockingIsProvided() {
         for (int i = 0; i < 10; i++) {
             new Thread(new Runnable() {
                 @Override

kotlin-libraries-2/pom.xml

@@ -18,14 +18,16 @@
             <groupId>com.fasterxml.jackson.module</groupId>
             <artifactId>jackson-module-kotlin</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.reactivex.rxjava2</groupId>
+            <artifactId>rxkotlin</artifactId>
+            <version>2.3.0</version>
+        </dependency>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <scope>test</scope>
         </dependency>
-
-
-        
     </dependencies>
 
     <properties>

kotlin-libraries-2/src/test/kotlin/com/baeldung/kotlin/rxkotlin/RxKotlinTest.kt

@@ -0,0 +1,157 @@
+package com.baeldung.kotlin.rxkotlin
+
+import io.reactivex.Maybe
+import io.reactivex.Observable
+import io.reactivex.functions.BiFunction
+import io.reactivex.rxkotlin.*
+import io.reactivex.subjects.PublishSubject
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+
+class RxKotlinTest {
+
+    @Test
+    fun whenBooleanArrayToObserver_thenBooleanObserver() {
+        val observable = listOf(true, false, false).toObservable()
+        observable.test().assertValues(true, false, false)
+    }
+
+    @Test
+    fun whenBooleanArrayToFlowable_thenBooleanFlowable() {
+        val flowable = listOf(true, false, false).toFlowable()
+        flowable.buffer(2).test().assertValues(listOf(true, false), listOf(false))
+    }
+
+    @Test
+    fun whenIntArrayToObserver_thenIntObserver() {
+        val observable = listOf(1, 1, 2, 3).toObservable()
+        observable.test().assertValues(1, 1, 2, 3)
+    }
+
+    @Test
+    fun whenIntArrayToFlowable_thenIntFlowable() {
+        val flowable = listOf(1, 1, 2, 3).toFlowable()
+        flowable.buffer(2).test().assertValues(listOf(1, 1), listOf(2, 3))
+    }
+
+    @Test
+    fun whenObservablePairToMap_thenSingleNoDuplicates() {
+        val list = listOf(Pair("a", 1), Pair("b", 2), Pair("c", 3), Pair("a", 4))
+        val observable = list.toObservable()
+        val map = observable.toMap()
+        assertEquals(mapOf(Pair("a", 4), Pair("b", 2), Pair("c", 3)), map.blockingGet())
+    }
+
+    @Test
+    fun whenObservablePairToMap_thenSingleWithDuplicates() {
+        val list = listOf(Pair("a", 1), Pair("b", 2), Pair("c", 3), Pair("a", 4))
+        val observable = list.toObservable()
+        val map = observable.toMultimap()
+        assertEquals(
+                mapOf(Pair("a", listOf(1, 4)), Pair("b", listOf(2)), Pair("c", listOf(3))),
+                map.blockingGet())
+    }
+
+    @Test
+    fun whenMergeAll_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.mergeAll()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenConcatAll_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.concatAll()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenSwitchLatest_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.switchLatest()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenMergeAllMaybes_thenObservable() {
+        val subject = PublishSubject.create<Maybe<Int>>()
+        val observable = subject.mergeAllMaybes()
+        val testObserver = observable.test()
+        subject.onNext(Maybe.just(1))
+        subject.onNext(Maybe.just(2))
+        subject.onNext(Maybe.empty())
+        testObserver.assertValues(1, 2)
+        subject.onNext(Maybe.error(Exception("")))
+        subject.onNext(Maybe.just(3))
+        testObserver.assertValues(1, 2).assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenMerge_thenStream() {
+        val observables = mutableListOf(Observable.just("first", "second"))
+        val observable = observables.merge()
+        observables.add(Observable.just("third", "fourth"))
+        observables.add(Observable.error(Exception("e")))
+        observables.add(Observable.just("fifth"))
+
+        observable.test().assertValues("first", "second", "third", "fourth").assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenMergeDelayError_thenStream() {
+        val observables = mutableListOf<Observable<String>>(Observable.error(Exception("e1")))
+        val observable = observables.mergeDelayError()
+        observables.add(Observable.just("1", "2"))
+        observables.add(Observable.error(Exception("e2")))
+        observables.add(Observable.just("3"))
+
+        observable.test().assertValues("1", "2", "3").assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenCast_thenUniformType() {
+        val observable = Observable.just<Number>(1, 1, 2, 3)
+        observable.cast<Int>().test().assertValues(1, 1, 2, 3)
+    }
+
+    @Test
+    fun whenOfType_thenFilter() {
+        val observable = Observable.just(1, "and", 2, "and")
+        observable.ofType<Int>().test().assertValues(1, 2)
+    }
+
+    @Test
+    fun whenFunction_thenCompletable() {
+        var value = 0
+        val completable = { value = 3 }.toCompletable()
+        assertFalse(completable.test().isCancelled)
+        assertEquals(3, value)
+    }
+
+    @Test
+    fun whenHelper_thenMoreIdiomaticKotlin() {
+        val zipWith = Observable.just(1).zipWith(Observable.just(2)) { a, b -> a + b }
+        zipWith.subscribeBy(onNext = { println(it) })
+        val zip = Observables.zip(Observable.just(1), Observable.just(2)) { a, b -> a + b }
+        zip.subscribeBy(onNext = { println(it) })
+        val zipOrig = Observable.zip(Observable.just(1), Observable.just(2), BiFunction<Int, Int, Int> { a, b -> a + b })
+        zipOrig.subscribeBy(onNext = { println(it) })
+    }
+}

kotlin-libraries/build.gradle

@@ -54,9 +54,8 @@ dependencies {
     testCompile group: 'org.jetbrains.spek', name: 'spek-subject-extension', version: '1.1.5'
     testCompile group: 'org.jetbrains.spek', name: 'spek-junit-platform-engine', version: '1.1.5'
     implementation 'com.beust:klaxon:3.0.1'
-    implementation 'io.reactivex.rxjava2:rxkotlin:2.3.0'
-
 }
+
 task runServer(type: JavaExec) {
     main = 'APIServer'
    classpath = sourceSets.main.runtimeClasspath

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/entity/Student.java

@@ -0,0 +1,75 @@
+package com.baeldung.jpa.entity;
+
+import java.util.Date;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.EnumType;
+import javax.persistence.Enumerated;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Table;
+import javax.persistence.Temporal;
+import javax.persistence.TemporalType;
+import javax.persistence.Transient;
+
+import com.baeldung.util.Gender;
+
+@Entity
+@Table(name="STUDENT")
+public class Student {
+
+	@Id
+	@GeneratedValue(strategy = GenerationType.AUTO)
+	private Long id;
+	@Column(name = "STUDENT_NAME", length = 50, nullable = false, unique = false)
+	private String name;
+	@Transient
+	private Integer age;
+	@Temporal(TemporalType.DATE)
+	private Date birthDate;
+	@Enumerated(EnumType.STRING)
+	private Gender gender;
+
+	public Long getId() {
+		return id;
+	}
+
+	public void setId(Long id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public Integer getAge() {
+		return age;
+	}
+
+	public void setAge(Integer age) {
+		this.age = age;
+	}
+
+	public Date getBirthDate() {
+		return birthDate;
+	}
+
+	public void setBirthDate(Date birthDate) {
+		this.birthDate = birthDate;
+	}
+
+	public Gender getGender() {
+		return gender;
+	}
+
+	public void setGender(Gender gender) {
+		this.gender = gender;
+	}
+
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Article.java

@@ -0,0 +1,91 @@
+package com.baeldung.jpa.enums;
+
+import javax.persistence.*;
+
+@Entity
+public class Article {
+
+    @Id
+    private int id;
+
+    private String title;
+
+    @Enumerated(EnumType.ORDINAL)
+    private Status status;
+
+    @Enumerated(EnumType.STRING)
+    private Type type;
+
+    @Basic
+    private int priorityValue;
+
+    @Transient
+    private Priority priority;
+
+    private Category category;
+
+    public Article() {
+    }
+
+    @PostLoad
+    void fillTransient() {
+        if (priorityValue > 0) {
+            this.priority = Priority.of(priorityValue);
+        }
+    }
+
+    @PrePersist
+    void fillPersistent() {
+        if (priority != null) {
+            this.priorityValue = priority.getPriority();
+        }
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Status getStatus() {
+        return status;
+    }
+
+    public void setStatus(Status status) {
+        this.status = status;
+    }
+
+    public Type getType() {
+        return type;
+    }
+
+    public void setType(Type type) {
+        this.type = type;
+    }
+
+    public Priority getPriority() {
+        return priority;
+    }
+
+    public void setPriority(Priority priority) {
+        this.priority = priority;
+    }
+
+    public Category getCategory() {
+        return category;
+    }
+
+    public void setCategory(Category category) {
+        this.category = category;
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Category.java

@@ -0,0 +1,17 @@
+package com.baeldung.jpa.enums;
+
+import java.util.stream.Stream;
+
+public enum Category {
+    SPORT("S"), MUSIC("M"), TECHNOLOGY("T");
+
+    private String code;
+
+    Category(String code) {
+        this.code = code;
+    }
+
+    public String getCode() {
+        return code;
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/CategoryConverter.java

@@ -0,0 +1,28 @@
+package com.baeldung.jpa.enums;
+
+import javax.persistence.AttributeConverter;
+import javax.persistence.Converter;
+import java.util.stream.Stream;
+
+@Converter(autoApply = true)
+public class CategoryConverter implements AttributeConverter<Category, String> {
+    @Override
+    public String convertToDatabaseColumn(Category category) {
+        if (category == null) {
+            return null;
+        }
+        return category.getCode();
+    }
+
+    @Override
+    public Category convertToEntityAttribute(final String code) {
+        if (code == null) {
+            return null;
+        }
+
+        return Stream.of(Category.values())
+                .filter(c -> c.getCode().equals(code))
+                .findFirst()
+                .orElseThrow(IllegalArgumentException::new);
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Priority.java

@@ -0,0 +1,24 @@
+package com.baeldung.jpa.enums;
+
+import java.util.stream.Stream;
+
+public enum Priority {
+    LOW(100), MEDIUM(200), HIGH(300);
+
+    private int priority;
+
+    private Priority(int priority) {
+        this.priority = priority;
+    }
+
+    public int getPriority() {
+        return priority;
+    }
+
+    public static Priority of(int priority) {
+        return Stream.of(Priority.values())
+                .filter(p -> p.getPriority() == priority)
+                .findFirst()
+                .orElseThrow(IllegalArgumentException::new);
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Status.java

@@ -0,0 +1,5 @@
+package com.baeldung.jpa.enums;
+
+public enum Status {
+    OPEN, REVIEW, APPROVED, REJECTED;
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Type.java

@@ -0,0 +1,5 @@
+package com.baeldung.jpa.enums;
+
+enum Type {
+    INTERNAL, EXTERNAL;
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/util/Gender.java

@@ -0,0 +1,6 @@
+package com.baeldung.util;
+
+public enum Gender {
+	MALE,
+	FEMALE
+}

persistence-modules/java-jpa/src/main/resources/META-INF/persistence.xml

@@ -26,6 +26,8 @@
     <persistence-unit name="jpa-h2">
         <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
         <class>com.baeldung.jpa.stringcast.Message</class>
+        <class>com.baeldung.jpa.enums.Article</class>
+        <class>com.baeldung.jpa.enums.CategoryConverter</class>
         <exclude-unlisted-classes>true</exclude-unlisted-classes>
         <properties>
             <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
@@ -146,4 +148,19 @@
         </properties>
     </persistence-unit>
     
+    <persistence-unit name="jpa-entity-definition">
+        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
+        <class>com.baeldung.jpa.entity.Student</class>
+        <exclude-unlisted-classes>true</exclude-unlisted-classes>
+        <properties>
+            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver" />
+            <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test" />
+            <property name="javax.persistence.jdbc.user" value="sa" />
+            <property name="javax.persistence.jdbc.password" value="" />
+            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect" />
+            <property name="hibernate.hbm2ddl.auto" value="create-drop" />
+            <property name="show_sql" value="true" />
+            <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false" />
+        </properties>
+    </persistence-unit>
 </persistence>

persistence-modules/java-jpa/src/test/java/com/baeldung/jpa/entity/StudentEntityIntegrationTest.java

@@ -0,0 +1,91 @@
+package com.baeldung.jpa.entity;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Date;
+import java.util.List;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Persistence;
+import javax.persistence.TypedQuery;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.baeldung.util.Gender;
+
+public class StudentEntityIntegrationTest {
+
+	private EntityManagerFactory emf;
+	private EntityManager em;
+
+	@Before
+	public void setup() {
+		emf = Persistence.createEntityManagerFactory("jpa-entity-definition");
+		em = emf.createEntityManager();
+	}
+
+	@Test
+	public void persistStudentThenRetrieveTheDetails() {
+		Student student = createStudentWithRelevantDetails();
+		persist(student);
+		clearThePersistenceContext();
+		List<Student> students = getStudentsFromTable();
+		checkAssertionsWith(students);
+	}
+
+	@After
+	public void destroy() {
+		if (em != null) {
+			em.close();
+		}
+		if (emf != null) {
+			emf.close();
+		}
+	}
+
+	private void clearThePersistenceContext() {
+		em.clear();
+	}
+
+	private void checkAssertionsWith(List<Student> students) {
+		assertEquals(1, students.size());
+		Student john = students.get(0);
+		assertEquals(1L, john.getId().longValue());
+		assertEquals(null, john.getAge());
+		assertEquals("John", john.getName());
+	}
+
+	private List<Student> getStudentsFromTable() {
+		String selectQuery = "SELECT student FROM Student student";
+		TypedQuery<Student> selectFromStudentTypedQuery = em.createQuery(selectQuery, Student.class);
+		List<Student> students = selectFromStudentTypedQuery.getResultList();
+		return students;
+	}
+
+	private void persist(Student student) {
+		em.getTransaction().begin();
+		em.persist(student);
+		em.getTransaction().commit();
+	}
+
+	private Student createStudentWithRelevantDetails() {
+		Student student = new Student();
+		student.setAge(20); // the 'age' field has been annotated with @Transient
+		student.setName("John");
+		Date date = getDate();
+		student.setBirthDate(date);
+		student.setGender(Gender.MALE);
+		return student;
+	}
+
+	private Date getDate() {
+		LocalDate localDate = LocalDate.of(2008, 7, 20);
+		return Date.from(localDate.atStartOfDay(ZoneId.systemDefault()).toInstant());
+	}
+
+}

persistence-modules/java-jpa/src/test/java/com/baeldung/jpa/enums/ArticleUnitTest.java

@@ -0,0 +1,118 @@
+package com.baeldung.jpa.enums;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ArticleUnitTest {
+
+    private static EntityManager em;
+    private static EntityManagerFactory emFactory;
+
+    @BeforeClass
+    public static void setup() {
+        Map properties = new HashMap();
+        properties.put("hibernate.show_sql", "true");
+        properties.put("hibernate.format_sql", "true");
+        emFactory = Persistence.createEntityManagerFactory("jpa-h2", properties);
+        em = emFactory.createEntityManager();
+    }
+
+    @Test
+    public void shouldPersistStatusEnumOrdinalValue() {
+        // given
+        Article article = new Article();
+        article.setId(1);
+        article.setTitle("ordinal title");
+        article.setStatus(Status.OPEN);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 1);
+
+        assertEquals(1, persistedArticle.getId());
+        assertEquals("ordinal title", persistedArticle.getTitle());
+        assertEquals(Status.OPEN, persistedArticle.getStatus());
+    }
+
+    @Test
+    public void shouldPersistTypeEnumStringValue() {
+        // given
+        Article article = new Article();
+        article.setId(2);
+        article.setTitle("string title");
+        article.setType(Type.EXTERNAL);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 2);
+
+        assertEquals(2, persistedArticle.getId());
+        assertEquals("string title", persistedArticle.getTitle());
+        assertEquals(Type.EXTERNAL, persistedArticle.getType());
+    }
+
+    @Test
+    public void shouldPersistPriorityIntValue() {
+        // given
+        Article article = new Article();
+        article.setId(3);
+        article.setTitle("callback title");
+        article.setPriority(Priority.HIGH);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 3);
+
+        assertEquals(3, persistedArticle.getId());
+        assertEquals("callback title", persistedArticle.getTitle());
+        assertEquals(Priority.HIGH, persistedArticle.getPriority());
+
+    }
+
+    @Test
+    public void shouldPersistCategoryEnumConvertedValue() {
+        // given
+        Article article = new Article();
+        article.setId(4);
+        article.setTitle("converted title");
+        article.setCategory(Category.MUSIC);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 4);
+
+        assertEquals(4, persistedArticle.getId());
+        assertEquals("converted title", persistedArticle.getTitle());
+        assertEquals(Category.MUSIC, persistedArticle.getCategory());
+    }
+
+}

persistence-modules/spring-data-jpa-2/src/main/java/com/baeldung/like/model/Movie.java

@@ -0,0 +1,58 @@
+package com.baeldung.like.model;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity
+public class Movie {
+    @Id
+    @GeneratedValue(strategy = GenerationType.SEQUENCE)
+    private Long id;
+    private String title;
+    private String director;
+    private String rating;
+    private int duration;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public String getDirector() {
+        return director;
+    }
+
+    public void setDirector(String director) {
+        this.director = director;
+    }
+
+    public String getRating() {
+        return rating;
+    }
+
+    public void setRating(String rating) {
+        this.rating = rating;
+    }
+
+    public int getDuration() {
+        return duration;
+    }
+
+    public void setDuration(int duration) {
+        this.duration = duration;
+    }
+
+}