Merge pull request #1 from eugenp/master

Update fork with main repo

.gitignore

@@ -19,6 +19,7 @@
 .idea/
 *.iml
 *.iws
+out/
 
 # Mac
 .DS_Store
@@ -27,6 +28,9 @@
 log/
 target/
 
+# Gradle
+.gradle/
+
 spring-openid/src/main/resources/application.properties
 .recommenders/
 /spring-hibernate4/nbproject/
@@ -66,3 +70,12 @@ jmeter/src/main/resources/*-JMeter.csv
 **/nb-configuration.xml
 core-scala/.cache-main
 core-scala/.cache-tests
+
+
+persistence-modules/hibernate5/transaction.log
+apache-avro/src/main/java/com/baeldung/avro/model/
+jta/transaction-logs/
+software-security/sql-injection-samples/derby.log
+spring-soap/src/main/java/com/baeldung/springsoap/gen/
+/report-*.json
+transaction.log

JGit/pom.xml

@@ -5,9 +5,9 @@
     <groupId>com.baeldung</groupId>
     <artifactId>JGit</artifactId>
     <version>1.0-SNAPSHOT</version>
+	<name>JGit</name>
     <packaging>jar</packaging>
     <url>http://maven.apache.org</url>
-	<name>JGit</name>
 
     <parent>
         <groupId>com.baeldung</groupId>

README.md

@@ -14,23 +14,28 @@ Java and Spring Tutorials
 ================
 
 This project is **a collection of small and focused tutorials** - each covering a single and well defined area of development in the Java ecosystem. 
-A strong focus of these is, of course, the Spring Framework - Spring, Spring Boot and Spring Securiyt. 
+A strong focus of these is, of course, the Spring Framework - Spring, Spring Boot and Spring Security. 
 In additional to Spring, the following technologies are in focus: `core Java`, `Jackson`, `HttpClient`, `Guava`. 
 
 
 Building the project
 ====================
-To do the full build, do: `mvn install -Pdefault -Dgib.enabled=false`
+To do the full build, do: `mvn clean install`
 
 
 Building a single module
 ====================
-To build a specific module run the command: `mvn clean install -Dgib.enabled=false` in the module directory
+To build a specific module run the command: `mvn clean install` in the module directory
 
 
 Running a Spring Boot module
 ====================
-To run a Spring Boot module run the command: `mvn spring-boot:run -Dgib.enabled=false` in the module directory
+To run a Spring Boot module run the command: `mvn spring-boot:run` in the module directory
+
+#Running Tests
+
+The command `mvn clean install` will run the unit tests in a module.
+To run the integration tests, use the command `mvn clean install -Pintegration-lite-first`
 
 
 

Twitter4J/pom.xml

@@ -2,8 +2,8 @@
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>Twitter4J</artifactId>
-    <packaging>jar</packaging>
     <name>Twitter4J</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>

akka-http/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Introduction to Akka HTTP](https://www.baeldung.com/akka-http)

akka-http/pom.xml

@@ -0,0 +1,47 @@
+<?xml version="1.0"?>
+<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">
+
+	<modelVersion>4.0.0</modelVersion>
+	<artifactId>akka-http</artifactId>
+	<name>akka-http</name>
+
+	<parent>
+		<artifactId>parent-modules</artifactId>
+		<groupId>com.baeldung</groupId>
+		<version>1.0.0-SNAPSHOT</version>
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-http_2.12</artifactId>
+			<version>${akka.http.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-stream_2.12</artifactId>
+			<version>${akka.stream.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-http-jackson_2.12</artifactId>
+			<version>${akka.http.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-http-testkit_2.12</artifactId>
+			<version>${akka.http.version}</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+		<akka.http.version>10.0.11</akka.http.version>
+		<akka.stream.version>2.5.11</akka.stream.version>
+	</properties>
+</project>

akka-http/src/main/java/com/baeldung/akkahttp/User.java

@@ -0,0 +1,26 @@
+package com.baeldung.akkahttp;
+
+public class User {
+
+    private final Long id;
+
+    private final String name;
+
+    public User() {
+        this.name = "";
+        this.id = null;
+    }
+
+    public User(Long id, String name) {
+        this.name = name;
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Long getId() {
+        return id;
+    }
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserActor.java

@@ -0,0 +1,41 @@
+package com.baeldung.akkahttp;
+
+import akka.actor.AbstractActor;
+import akka.actor.Props;
+import akka.japi.pf.FI;
+import com.baeldung.akkahttp.UserMessages.ActionPerformed;
+import com.baeldung.akkahttp.UserMessages.CreateUserMessage;
+import com.baeldung.akkahttp.UserMessages.GetUserMessage;
+
+
+class UserActor extends AbstractActor {
+
+  private UserService userService = new UserService();
+
+  static Props props() {
+    return Props.create(UserActor.class);
+  }
+
+  @Override
+  public Receive createReceive() {
+    return receiveBuilder()
+            .match(CreateUserMessage.class, handleCreateUser())
+            .match(GetUserMessage.class, handleGetUser())
+            .build();
+  }
+
+  private FI.UnitApply<CreateUserMessage> handleCreateUser() {
+    return createUserMessageMessage -> {
+      userService.createUser(createUserMessageMessage.getUser());
+      sender().tell(new ActionPerformed(String.format("User %s created.", createUserMessageMessage.getUser()
+              .getName())), getSelf());
+    };
+  }
+
+  private FI.UnitApply<GetUserMessage> handleGetUser() {
+    return getUserMessageMessage -> {
+      sender().tell(userService.getUser(getUserMessageMessage.getUserId()), getSelf());
+    };
+  }
+
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserMessages.java

@@ -0,0 +1,49 @@
+package com.baeldung.akkahttp;
+
+import java.io.Serializable;
+
+public interface UserMessages {
+
+  class ActionPerformed implements Serializable {
+
+    private static final long serialVersionUID = 1L;
+
+    private final String description;
+
+    public ActionPerformed(String description) {
+      this.description = description;
+    }
+
+    public String getDescription() {
+      return description;
+    }
+  }
+
+  class CreateUserMessage implements Serializable {
+
+    private static final long serialVersionUID = 1L;
+    private final User user;
+
+    public CreateUserMessage(User user) {
+      this.user = user;
+    }
+
+    public User getUser() {
+      return user;
+    }
+  }
+
+  class GetUserMessage implements Serializable {
+    private static final long serialVersionUID = 1L;
+    private final Long userId;
+
+    public GetUserMessage(Long userId) {
+      this.userId = userId;
+    }
+
+    public Long getUserId() {
+      return userId;
+    }
+  }
+
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserServer.java

@@ -0,0 +1,70 @@
+package com.baeldung.akkahttp;
+
+import java.util.Optional;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.TimeUnit;
+
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.http.javadsl.marshallers.jackson.Jackson;
+import akka.http.javadsl.model.StatusCodes;
+import akka.http.javadsl.server.HttpApp;
+import akka.http.javadsl.server.Route;
+import akka.pattern.PatternsCS;
+import akka.util.Timeout;
+import com.baeldung.akkahttp.UserMessages.ActionPerformed;
+import com.baeldung.akkahttp.UserMessages.CreateUserMessage;
+import com.baeldung.akkahttp.UserMessages.GetUserMessage;
+import scala.concurrent.duration.Duration;
+import static akka.http.javadsl.server.PathMatchers.*;
+
+class UserServer extends HttpApp {
+
+  private final ActorRef userActor;
+
+  Timeout timeout = new Timeout(Duration.create(5, TimeUnit.SECONDS));
+
+  UserServer(ActorRef userActor) {
+    this.userActor = userActor;
+  }
+
+  @Override
+  public Route routes() {
+    return path("users", this::postUser)
+            .orElse(path(segment("users").slash(longSegment()), id ->
+                    route(getUser(id))));
+  }
+
+  private Route getUser(Long id) {
+    return get(() -> {
+      CompletionStage<Optional<User>> user = PatternsCS.ask(userActor, new GetUserMessage(id), timeout)
+              .thenApply(obj -> (Optional<User>) obj);
+
+      return onSuccess(() -> user, performed -> {
+        if (performed.isPresent())
+          return complete(StatusCodes.OK, performed.get(), Jackson.marshaller());
+        else
+          return complete(StatusCodes.NOT_FOUND);
+      });
+    });
+  }
+
+  private Route postUser() {
+    return route(post(() -> entity(Jackson.unmarshaller(User.class), user -> {
+      CompletionStage<ActionPerformed> userCreated = PatternsCS.ask(userActor, new CreateUserMessage(user), timeout)
+              .thenApply(obj -> (ActionPerformed) obj);
+
+      return onSuccess(() -> userCreated, performed -> {
+        return complete(StatusCodes.CREATED, performed, Jackson.marshaller());
+      });
+    })));
+  }
+
+  public static void main(String[] args) throws Exception {
+    ActorSystem system = ActorSystem.create("userServer");
+    ActorRef userActor = system.actorOf(UserActor.props(), "userActor");
+    UserServer server = new UserServer(userActor);
+    server.startServer("localhost", 8080, system);
+  }
+
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserService.java

@@ -0,0 +1,35 @@
+package com.baeldung.akkahttp;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+public class UserService {
+
+  private final static List<User> users = new ArrayList<>();
+
+  static {
+    users.add(new User(1l, "Alice"));
+    users.add(new User(2l, "Bob"));
+    users.add(new User(3l, "Chris"));
+    users.add(new User(4l, "Dick"));
+    users.add(new User(5l, "Eve"));
+    users.add(new User(6l, "Finn"));
+  }
+
+  public Optional<User> getUser(Long id) {
+    return users.stream()
+            .filter(user -> user.getId()
+                    .equals(id))
+            .findFirst();
+  }
+
+  public void createUser(User user) {
+    users.add(user);
+  }
+
+  public List<User> getUsers(){
+    return users;
+  }
+
+}

akka-http/src/test/java/com/baeldung/akkahttp/UserServerUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.akkahttp;
+
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.http.javadsl.model.ContentTypes;
+import akka.http.javadsl.model.HttpEntities;
+import akka.http.javadsl.model.HttpRequest;
+import akka.http.javadsl.testkit.JUnitRouteTest;
+import akka.http.javadsl.testkit.TestRoute;
+import org.junit.Test;
+
+public class UserServerUnitTest extends JUnitRouteTest {
+
+  ActorSystem system = ActorSystem.create("helloAkkaHttpServer");
+
+  ActorRef userActorRef = system.actorOf(UserActor.props(), "userActor");
+
+  TestRoute appRoute = testRoute(new UserServer(userActorRef).routes());
+
+  @Test
+  public void whenRequest_thenActorResponds() {
+
+    appRoute.run(HttpRequest.GET("/users/1"))
+            .assertEntity(alice())
+            .assertStatusCode(200);
+
+    appRoute.run(HttpRequest.GET("/users/42"))
+            .assertStatusCode(404);
+
+    appRoute.run(HttpRequest.DELETE("/users/1"))
+            .assertStatusCode(200);
+
+    appRoute.run(HttpRequest.DELETE("/users/42"))
+            .assertStatusCode(200);
+
+    appRoute.run(HttpRequest.POST("/users")
+            .withEntity(HttpEntities.create(ContentTypes.APPLICATION_JSON, zaphod())))
+            .assertStatusCode(201);
+
+  }
+
+  private String alice() {
+    return "{\"id\":1,\"name\":\"Alice\"}";
+  }
+
+  private String zaphod() {
+    return "{\"id\":42,\"name\":\"Zaphod\"}";
+  }
+
+}

akka-streams/pom.xml

@@ -14,18 +14,19 @@
     <dependencies>
         <dependency>
             <groupId>com.typesafe.akka</groupId>
-            <artifactId>akka-stream_2.11</artifactId>
+            <artifactId>akka-stream_${scala.version}</artifactId>
             <version>${akkastreams.version}</version>
         </dependency>
         <dependency>
             <groupId>com.typesafe.akka</groupId>
-            <artifactId>akka-stream-testkit_2.11</artifactId>
+            <artifactId>akka-stream-testkit_${scala.version}</artifactId>
             <version>${akkastreams.version}</version>
         </dependency>
     </dependencies>
 
     <properties>
         <akkastreams.version>2.5.2</akkastreams.version>
+        <scala.version>2.11</scala.version>
     </properties>
 
 </project>

algorithms-genetic/pom.xml

@@ -54,7 +54,6 @@
     </build>
 
     <properties>
-        <lombok.version>1.16.12</lombok.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <io.jenetics.version>3.7.0</io.jenetics.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>

algorithms-miscellaneous-1/README.md

@@ -10,4 +10,9 @@
 - [Multi-Swarm Optimization Algorithm in Java](http://www.baeldung.com/java-multi-swarm-algorithm)
 - [String Search Algorithms for Large Texts](http://www.baeldung.com/java-full-text-search-algorithms)
 - [Check If a String Contains All The Letters of The Alphabet](https://www.baeldung.com/java-string-contains-all-letters)
-- [Find the Middle Element of a Linked List](http://www.baeldung.com/java-linked-list-middle-element)
+- [Find the Middle Element of a Linked List](http://www.baeldung.com/java-linked-list-middle-element)
+- [Calculate Factorial in Java](https://www.baeldung.com/java-calculate-factorial)
+- [Find Substrings That Are Palindromes in Java](https://www.baeldung.com/java-palindrome-substrings)
+- [Find the Longest Substring without Repeating Characters](https://www.baeldung.com/java-longest-substring-without-repeated-characters)
+- [Permutations of an Array in Java](https://www.baeldung.com/java-array-permutations)
+- [Generate Combinations in Java](https://www.baeldung.com/java-combinations-algorithm)

algorithms-miscellaneous-1/pom.xml

@@ -39,6 +39,11 @@
             <version>${org.assertj.core.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.github.dpaukov</groupId>
+            <artifactId>combinatoricslib3</artifactId>
+            <version>${combinatoricslib3.version}</version>
+         </dependency>
     </dependencies>
 
     <build>
@@ -74,11 +79,11 @@
     </reporting>
 
     <properties>
-        <lombok.version>1.16.12</lombok.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
-        <guava.version>25.1-jre</guava.version>
+        <guava.version>27.0.1-jre</guava.version>
+        <combinatoricslib3.version>3.3.0</combinatoricslib3.version>
     </properties>
 
 </project>

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/permutation/Permutation.java

@@ -0,0 +1,123 @@
+package com.baeldung.algorithms.permutation;
+
+import java.util.Arrays;
+import java.util.Collections;
+
+public  class Permutation {
+
+    public static <T> void printAllRecursive(T[] elements, char delimiter) {
+        printAllRecursive(elements.length, elements, delimiter);
+    }
+
+    public static <T> void printAllRecursive(int n, T[] elements, char delimiter) {
+
+        if(n == 1) {
+            printArray(elements, delimiter);
+        } else {
+            for(int i = 0; i < n-1; i++) {
+                printAllRecursive(n - 1, elements, delimiter);
+                if(n % 2 == 0) {
+                    swap(elements, i, n-1);
+                } else {
+                    swap(elements, 0, n-1);
+                }
+            }
+            printAllRecursive(n - 1, elements, delimiter);
+        }
+    }
+
+    public static <T> void printAllIterative(int n, T[] elements, char delimiter) {
+
+        int[] indexes = new int[n];
+        for (int i = 0; i < n; i++) {
+            indexes[i] = 0;
+        }
+
+        printArray(elements, delimiter);
+
+        int i = 0;
+        while (i < n) {
+            if (indexes[i] < i) {
+                swap(elements, i % 2 == 0 ?  0: indexes[i], i);
+                printArray(elements, delimiter);
+                indexes[i]++;
+                i = 0;
+            }
+            else {
+                indexes[i] = 0;
+                i++;
+            }
+        }
+    }
+
+    public static <T extends Comparable<T>> void printAllOrdered(T[] elements, char delimiter) {
+
+        Arrays.sort(elements);
+        boolean hasNext = true;
+
+        while(hasNext) {
+            printArray(elements, delimiter);
+            int k = 0, l = 0;
+            hasNext = false;
+            for (int i = elements.length - 1; i > 0; i--) {
+                if (elements[i].compareTo(elements[i - 1]) > 0) {
+                    k = i - 1;
+                    hasNext = true;
+                    break;
+                }
+            }
+
+            for (int i = elements.length - 1; i > k; i--) {
+                if (elements[i].compareTo(elements[k]) > 0) {
+                    l = i;
+                    break;
+                }
+            }
+
+            swap(elements, k, l);
+            Collections.reverse(Arrays.asList(elements).subList(k + 1, elements.length));
+        }
+    }
+
+    public static <T> void printRandom(T[] elements, char delimiter) {
+
+        Collections.shuffle(Arrays.asList(elements));
+        printArray(elements, delimiter);
+    }
+
+    private static <T> void swap(T[] elements, int a, int b) {
+
+        T tmp = elements[a];
+        elements[a] = elements[b];
+        elements[b] = tmp;
+    }
+
+    private static <T> void printArray(T[] elements, char delimiter) {
+
+        String delimiterSpace = delimiter + " ";
+        for(int i = 0; i < elements.length; i++) {
+            System.out.print(elements[i] + delimiterSpace);
+        }
+        System.out.print('\n');
+    }
+
+    public static void main(String[] argv) {
+
+        Integer[] elements = {1,2,3,4};
+
+        System.out.println("Rec:");
+        printAllRecursive(elements, ';');
+
+        System.out.println("Iter:");
+        printAllIterative(elements.length, elements, ';');
+
+        System.out.println("Orderes:");
+        printAllOrdered(elements, ';');
+
+        System.out.println("Random:");
+        printRandom(elements, ';');
+
+        System.out.println("Random:");
+        printRandom(elements, ';');
+    }
+}

algorithms-miscellaneous-2/README.md

@@ -8,9 +8,6 @@
 - [Create a Sudoku Solver in Java](http://www.baeldung.com/java-sudoku)
 - [Displaying Money Amounts in Words](http://www.baeldung.com/java-money-into-words)
 - [A Collaborative Filtering Recommendation System in Java](http://www.baeldung.com/java-collaborative-filtering-recommendations)
-- [Converting Between Roman and Arabic Numerals in Java](http://www.baeldung.com/java-convert-roman-arabic)
-- [Practical Java Examples of the Big O Notation](http://www.baeldung.com/java-algorithm-complexity)
-- [An Introduction to the Theory of Big-O Notation](http://www.baeldung.com/big-o-notation)
 - [Check If Two Rectangles Overlap In Java](https://www.baeldung.com/java-check-if-two-rectangles-overlap)
 - [Calculate the Distance Between Two Points in Java](https://www.baeldung.com/java-distance-between-two-points)
 - [Find the Intersection of Two Lines in Java](https://www.baeldung.com/java-intersection-of-two-lines)
@@ -18,3 +15,5 @@
 - [Calculate Percentage in Java](https://www.baeldung.com/java-calculate-percentage)
 - [Converting Between Byte Arrays and Hexadecimal Strings in Java](https://www.baeldung.com/java-byte-arrays-hex-strings)
 - [Convert Latitude and Longitude to a 2D Point in Java](https://www.baeldung.com/java-convert-latitude-longitude)
+- [Reversing a Binary Tree in Java](https://www.baeldung.com/java-reversing-a-binary-tree)
+- [Find If Two Numbers Are Relatively Prime in Java](https://www.baeldung.com/java-two-relatively-prime-numbers)

algorithms-miscellaneous-2/pom.xml

@@ -68,7 +68,7 @@
             <plugin>
                 <groupId>org.codehaus.mojo</groupId>
                 <artifactId>cobertura-maven-plugin</artifactId>
-                <version>2.7</version>
+                <version>${cobertura-maven-plugin.version}</version>
                 <configuration>
                     <instrumentation>
                         <ignores>
@@ -84,13 +84,13 @@
     </reporting>
 
     <properties>
-        <lombok.version>1.16.12</lombok.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <tradukisto.version>1.0.1</tradukisto.version>
         <org.jgrapht.core.version>1.0.1</org.jgrapht.core.version>
         <org.jgrapht.ext.version>1.0.1</org.jgrapht.ext.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
+        <cobertura-maven-plugin.version>2.7</cobertura-maven-plugin.version>
     </properties>
 
 </project>

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/relativelyprime/RelativelyPrime.java

@@ -0,0 +1,45 @@
+package com.baeldung.algorithms.relativelyprime;
+
+import java.math.BigInteger;
+
+class RelativelyPrime {
+
+    static boolean iterativeRelativelyPrime(int a, int b) {
+        return iterativeGCD(a, b) == 1;
+    }
+
+    static boolean recursiveRelativelyPrime(int a, int b) {
+        return recursiveGCD(a, b) == 1;
+    }
+
+    static boolean bigIntegerRelativelyPrime(int a, int b) {
+        return BigInteger.valueOf(a).gcd(BigInteger.valueOf(b)).equals(BigInteger.ONE);
+    }
+
+    private static int iterativeGCD(int a, int b) {
+        int tmp;
+        while (b != 0) {
+            if (a < b) {
+                tmp = a;
+                a = b;
+                b = tmp;
+            }
+            tmp = b;
+            b = a % b;
+            a = tmp;
+        }
+        return a;
+    }
+
+    private static int recursiveGCD(int a, int b) {
+        if (b == 0) {
+            return a;
+        }
+        if (a < b) {
+            return recursiveGCD(b, a);
+        }
+        return recursiveGCD(b, a % b);
+    }
+
+
+}

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeNode.java

@@ -0,0 +1,42 @@
+package com.baeldung.algorithms.reversingtree;
+
+public class TreeNode {
+
+    private int value;
+    private TreeNode rightChild;
+    private TreeNode leftChild;
+
+    public int getValue() {
+        return value;
+    }
+
+    public void setValue(int value) {
+        this.value = value;
+    }
+
+    public TreeNode getRightChild() {
+        return rightChild;
+    }
+
+    public void setRightChild(TreeNode rightChild) {
+        this.rightChild = rightChild;
+    }
+
+    public TreeNode getLeftChild() {
+        return leftChild;
+    }
+
+    public void setLeftChild(TreeNode leftChild) {
+        this.leftChild = leftChild;
+    }
+
+    public TreeNode(int value, TreeNode leftChild, TreeNode rightChild) {
+        this.value = value;
+        this.rightChild = rightChild;
+        this.leftChild = leftChild;
+    }
+
+    public TreeNode(int value) {
+        this.value = value;
+    }
+}

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeReverser.java

@@ -0,0 +1,53 @@
+package com.baeldung.algorithms.reversingtree;
+
+import java.util.LinkedList;
+
+public class TreeReverser {
+
+    public void reverseRecursive(TreeNode treeNode) {
+        if (treeNode == null) {
+            return;
+        }
+
+        TreeNode temp = treeNode.getLeftChild();
+        treeNode.setLeftChild(treeNode.getRightChild());
+        treeNode.setRightChild(temp);
+
+        reverseRecursive(treeNode.getLeftChild());
+        reverseRecursive(treeNode.getRightChild());
+    }
+
+    public void reverseIterative(TreeNode treeNode) {
+        LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
+
+        if (treeNode != null) {
+            queue.add(treeNode);
+        }
+
+        while (!queue.isEmpty()) {
+
+            TreeNode node = queue.poll();
+            if (node.getLeftChild() != null)
+                queue.add(node.getLeftChild());
+            if (node.getRightChild() != null)
+                queue.add(node.getRightChild());
+
+            TreeNode temp = node.getLeftChild();
+            node.setLeftChild(node.getRightChild());
+            node.setRightChild(temp);
+        }
+    }
+
+    public String toString(TreeNode root) {
+        if (root == null) {
+            return "";
+        }
+
+        StringBuffer buffer = new StringBuffer(String.valueOf(root.getValue())).append(" ");
+
+        buffer.append(toString(root.getLeftChild()));
+        buffer.append(toString(root.getRightChild()));
+
+        return buffer.toString();
+    }
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/relativelyprime/RelativelyPrimeUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.algorithms.relativelyprime;
+
+import org.junit.Test;
+
+import static com.baeldung.algorithms.relativelyprime.RelativelyPrime.*;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class RelativelyPrimeUnitTest {
+
+    @Test
+    public void givenNonRelativelyPrimeNumbers_whenCheckingIteratively_shouldReturnFalse() {
+
+        boolean result = iterativeRelativelyPrime(45, 35);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenRelativelyPrimeNumbers_whenCheckingIteratively_shouldReturnTrue() {
+
+        boolean result = iterativeRelativelyPrime(500, 501);
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenNonRelativelyPrimeNumbers_whenCheckingRecursively_shouldReturnFalse() {
+
+        boolean result = recursiveRelativelyPrime(45, 35);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenRelativelyPrimeNumbers_whenCheckingRecursively_shouldReturnTrue() {
+
+        boolean result = recursiveRelativelyPrime(500, 501);
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenNonRelativelyPrimeNumbers_whenCheckingUsingBigIntegers_shouldReturnFalse() {
+
+        boolean result = bigIntegerRelativelyPrime(45, 35);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenRelativelyPrimeNumbers_whenCheckingBigIntegers_shouldReturnTrue() {
+
+        boolean result = bigIntegerRelativelyPrime(500, 501);
+        assertThat(result).isTrue();
+    }
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/reversingtree/TreeReverserUnitTest.java

@@ -0,0 +1,47 @@
+package com.baeldung.algorithms.reversingtree;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class TreeReverserUnitTest {
+
+    @Test
+    public void givenTreeWhenReversingRecursivelyThenReversed() {
+        TreeReverser reverser = new TreeReverser();
+
+        TreeNode treeNode = createBinaryTree();
+
+        reverser.reverseRecursive(treeNode);
+
+        assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode)
+            .trim());
+    }
+
+    @Test
+    public void givenTreeWhenReversingIterativelyThenReversed() {
+        TreeReverser reverser = new TreeReverser();
+
+        TreeNode treeNode = createBinaryTree();
+
+        reverser.reverseIterative(treeNode);
+
+        assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode)
+            .trim());
+    }
+
+    private TreeNode createBinaryTree() {
+
+        TreeNode leaf1 = new TreeNode(1);
+        TreeNode leaf2 = new TreeNode(3);
+        TreeNode leaf3 = new TreeNode(6);
+        TreeNode leaf4 = new TreeNode(9);
+
+        TreeNode nodeRight = new TreeNode(7, leaf3, leaf4);
+        TreeNode nodeLeft = new TreeNode(2, leaf1, leaf2);
+
+        TreeNode root = new TreeNode(4, nodeLeft, nodeRight);
+
+        return root;
+    }
+}

algorithms-miscellaneous-3/.gitignore

@@ -0,0 +1,4 @@
+/target/
+.settings/
+.classpath
+.project

algorithms-miscellaneous-3/README.md

@@ -0,0 +1,9 @@
+## Relevant articles:
+
+- [Java Two Pointer Technique](https://www.baeldung.com/java-two-pointer-technique)
+- [Implementing Simple State Machines with Java Enums](https://www.baeldung.com/java-enum-simple-state-machine)
+- [Converting Between Roman and Arabic Numerals in Java](http://www.baeldung.com/java-convert-roman-arabic)
+- [Practical Java Examples of the Big O Notation](http://www.baeldung.com/java-algorithm-complexity)
+- [Checking If a List Is Sorted in Java](https://www.baeldung.com/java-check-if-list-sorted)
+- [Checking if a Java Graph has a Cycle](https://www.baeldung.com/java-graph-has-a-cycle)
+- [A Guide to the Folding Technique](https://www.baeldung.com/folding-hashing-technique)

algorithms-miscellaneous-3/pom.xml

@@ -0,0 +1,52 @@
+<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>algorithms-miscellaneous-3</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>algorithms-miscellaneous-3</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${org.assertj.core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        
+        <dependency>
+        	<groupId>org.apache.commons</groupId>
+        	<artifactId>commons-collections4</artifactId>
+        	<version>${commons-collections4.version}</version>
+        </dependency>
+        
+        <dependency>
+        	<groupId>com.google.guava</groupId>
+        	<artifactId>guava</artifactId>
+        	<version>${guava.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.codehaus.mojo</groupId>
+                    <artifactId>exec-maven-plugin</artifactId>
+                    <version>${exec-maven-plugin.version}</version>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+
+    <properties>
+        <org.assertj.core.version>3.9.0</org.assertj.core.version>
+        <commons-collections4.version>4.3</commons-collections4.version>
+        <guava.version>28.0-jre</guava.version>
+    </properties>
+</project>

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/checksortedlist/Employee.java

@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.checksortedlist;
+
+public class Employee {
+
+    long id;
+
+    String name;
+
+    public Employee() {
+    }
+
+    public Employee(long id, String name) {
+        super();
+        this.id = id;
+        this.name = name;
+    }
+
+    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;
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/checksortedlist/SortedListChecker.java

@@ -0,0 +1,87 @@
+package com.baeldung.algorithms.checksortedlist;
+
+import static org.apache.commons.collections4.CollectionUtils.isEmpty;
+
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.List;
+
+import com.google.common.collect.Comparators;
+import com.google.common.collect.Ordering;;
+
+public class SortedListChecker {
+
+    private SortedListChecker() {
+        throw new AssertionError();
+    }
+
+    public static boolean checkIfSortedUsingIterativeApproach(List<String> listOfStrings) {
+        if (isEmpty(listOfStrings) || listOfStrings.size() == 1) {
+            return true;
+        }
+
+        Iterator<String> iter = listOfStrings.iterator();
+        String current, previous = iter.next();
+        while (iter.hasNext()) {
+            current = iter.next();
+            if (previous.compareTo(current) > 0) {
+                return false;
+            }
+            previous = current;
+        }
+        return true;
+    }
+
+    public static boolean checkIfSortedUsingIterativeApproach(List<Employee> employees, Comparator<Employee> employeeComparator) {
+        if (isEmpty(employees) || employees.size() == 1) {
+            return true;
+        }
+
+        Iterator<Employee> iter = employees.iterator();
+        Employee current, previous = iter.next();
+        while (iter.hasNext()) {
+            current = iter.next();
+            if (employeeComparator.compare(previous, current) > 0) {
+                return false;
+            }
+            previous = current;
+        }
+        return true;
+    }
+
+    public static boolean checkIfSortedUsingRecursion(List<String> listOfStrings) {
+        return isSortedRecursive(listOfStrings, listOfStrings.size());
+    }
+
+    public static boolean isSortedRecursive(List<String> listOfStrings, int index) {
+        if (index < 2) {
+            return true;
+        } else if (listOfStrings.get(index - 2)
+            .compareTo(listOfStrings.get(index - 1)) > 0) {
+            return false;
+        } else {
+            return isSortedRecursive(listOfStrings, index - 1);
+        }
+    }
+
+    public static boolean checkIfSortedUsingOrderingClass(List<String> listOfStrings) {
+        return Ordering.<String> natural()
+            .isOrdered(listOfStrings);
+    }
+
+    public static boolean checkIfSortedUsingOrderingClass(List<Employee> employees, Comparator<Employee> employeeComparator) {
+        return Ordering.from(employeeComparator)
+            .isOrdered(employees);
+    }
+
+    public static boolean checkIfSortedUsingOrderingClassHandlingNull(List<String> listOfStrings) {
+        return Ordering.<String> natural()
+            .nullsLast()
+            .isOrdered(listOfStrings);
+    }
+
+    public static boolean checkIfSortedUsingComparators(List<String> listOfStrings) {
+        return Comparators.isInOrder(listOfStrings, Comparator.<String> naturalOrder());
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/enumstatemachine/LeaveRequestState.java

@@ -0,0 +1,46 @@
+package com.baeldung.algorithms.enumstatemachine;
+
+public enum LeaveRequestState {
+
+    Submitted {
+        @Override
+        public LeaveRequestState nextState() {
+            System.out.println("Starting the Leave Request and sending to Team Leader for approval.");
+            return Escalated;
+        }
+
+        @Override
+        public String responsiblePerson() {
+            return "Employee";
+        }
+    },
+    Escalated {
+        @Override
+        public LeaveRequestState nextState() {
+            System.out.println("Reviewing the Leave Request and escalating to Department Manager.");
+            return Approved;
+        }
+
+        @Override
+        public String responsiblePerson() {
+            return "Team Leader";
+        }
+    },
+    Approved {
+        @Override
+        public LeaveRequestState nextState() {
+            System.out.println("Approving the Leave Request.");
+            return this;
+        }
+
+        @Override
+        public String responsiblePerson() {
+            return "Department Manager";
+        }
+    };
+
+    public abstract String responsiblePerson();
+
+    public abstract LeaveRequestState nextState();
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/graphcycledetection/domain/Graph.java

@@ -0,0 +1,51 @@
+package com.baeldung.algorithms.graphcycledetection.domain;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Graph {
+
+    private List<Vertex> vertices;
+
+    public Graph() {
+        this.vertices = new ArrayList<>();
+    }
+
+    public Graph(List<Vertex> vertices) {
+        this.vertices = vertices;
+    }
+
+    public void addVertex(Vertex vertex) {
+        this.vertices.add(vertex);
+    }
+
+    public void addEdge(Vertex from, Vertex to) {
+        from.addNeighbour(to);
+    }
+
+    public boolean hasCycle() {
+        for (Vertex vertex : vertices) {
+            if (!vertex.isVisited() && hasCycle(vertex)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public boolean hasCycle(Vertex sourceVertex) {
+        sourceVertex.setBeingVisited(true);
+
+        for (Vertex neighbour : sourceVertex.getAdjacencyList()) {
+            if (neighbour.isBeingVisited()) {
+                // backward edge exists
+                return true;
+            } else if (!neighbour.isVisited() && hasCycle(neighbour)) {
+                return true;
+            }
+        }
+
+        sourceVertex.setBeingVisited(false);
+        sourceVertex.setVisited(true);
+        return false;
+    }
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/graphcycledetection/domain/Vertex.java

@@ -0,0 +1,56 @@
+package com.baeldung.algorithms.graphcycledetection.domain;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Vertex {
+
+    private String label;
+
+    private boolean visited;
+
+    private boolean beingVisited;
+
+    private List<Vertex> adjacencyList;
+
+    public Vertex(String label) {
+        this.label = label;
+        this.adjacencyList = new ArrayList<>();
+    }
+
+    public String getLabel() {
+        return label;
+    }
+
+    public void setLabel(String label) {
+        this.label = label;
+    }
+
+    public boolean isVisited() {
+        return visited;
+    }
+
+    public void setVisited(boolean visited) {
+        this.visited = visited;
+    }
+
+    public boolean isBeingVisited() {
+        return beingVisited;
+    }
+
+    public void setBeingVisited(boolean beingVisited) {
+        this.beingVisited = beingVisited;
+    }
+
+    public List<Vertex> getAdjacencyList() {
+        return adjacencyList;
+    }
+
+    public void setAdjacencyList(List<Vertex> adjacencyList) {
+        this.adjacencyList = adjacencyList;
+    }
+
+    public void addNeighbour(Vertex adjacent) {
+        this.adjacencyList.add(adjacent);
+    }
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/twopointertechnique/LinkedListFindMiddle.java

@@ -0,0 +1,16 @@
+package com.baeldung.algorithms.twopointertechnique;
+
+public class LinkedListFindMiddle {
+
+    public <T> T findMiddle(MyNode<T> head) {
+        MyNode<T> slowPointer = head;
+        MyNode<T> fastPointer = head;
+
+        while (fastPointer.next != null && fastPointer.next.next != null) {
+            fastPointer = fastPointer.next.next;
+            slowPointer = slowPointer.next;
+        }
+        return slowPointer.data;
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/twopointertechnique/MyNode.java

@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.twopointertechnique;
+
+public class MyNode<E> {
+    MyNode<E> next;
+    E data;
+
+    public MyNode(E value) {
+        data = value;
+        next = null;
+    }
+
+    public MyNode(E value, MyNode<E> n) {
+        data = value;
+        next = n;
+    }
+
+    public void setNext(MyNode<E> n) {
+        next = n;
+    }
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/twopointertechnique/RotateArray.java

@@ -0,0 +1,22 @@
+package com.baeldung.algorithms.twopointertechnique;
+
+public class RotateArray {
+
+    public void rotate(int[] input, int step) {
+        step %= input.length;
+        reverse(input, 0, input.length - 1);
+        reverse(input, 0, step - 1);
+        reverse(input, step, input.length - 1);
+    }
+
+    private void reverse(int[] input, int start, int end) {
+        while (start < end) {
+            int temp = input[start];
+            input[start] = input[end];
+            input[end] = temp;
+            start++;
+            end--;
+        }
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/twopointertechnique/TwoSum.java

@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.twopointertechnique;
+
+public class TwoSum {
+
+    public boolean twoSum(int[] input, int targetValue) {
+
+        int pointerOne = 0;
+        int pointerTwo = input.length - 1;
+
+        while (pointerOne < pointerTwo) {
+            int sum = input[pointerOne] + input[pointerTwo];
+
+            if (sum == targetValue) {
+                return true;
+            } else if (sum < targetValue) {
+                pointerOne++;
+            } else {
+                pointerTwo--;
+            }
+        }
+
+        return false;
+    }
+
+    public boolean twoSumSlow(int[] input, int targetValue) {
+
+        for (int i = 0; i < input.length; i++) {
+            for (int j = 1; j < input.length; j++) {
+                if (input[i] + input[j] == targetValue) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/folding/FoldingHash.java

@@ -0,0 +1,78 @@
+package com.baeldung.folding;
+
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+/**
+ * Calculate a hash value for the strings using the folding technique.
+ * 
+ * The implementation serves only to the illustration purposes and is far
+ * from being the most efficient. 
+ * 
+ * @author A.Shcherbakov
+ *
+ */
+public class FoldingHash {
+
+    /**
+     * Calculate the hash value of a given string.
+     * 
+     * @param str Assume it is not null
+     * @param groupSize the group size in the folding technique
+     * @param maxValue defines a max value that the hash may acquire (exclusive)     
+     * @return integer value from 0 (inclusive) to maxValue (exclusive)
+     */
+    public int hash(String str, int groupSize, int maxValue) {
+        final int[] codes = this.toAsciiCodes(str);
+        return IntStream.range(0, str.length())
+            .filter(i -> i % groupSize == 0)
+            .mapToObj(i -> extract(codes, i, groupSize))
+            .map(block -> concatenate(block))
+            .reduce(0, (a, b) -> (a + b) % maxValue);
+    }
+
+    /**
+     * Returns a new array of given length whose elements are take from 
+     * the original one starting from the offset.
+     *  
+     * If the original array has not enough elements, the returning array will contain 
+     * element from the offset till the end of the original array.
+     *  
+     * @param numbers original array. Assume it is not null.
+     * @param offset index of the element to start from. Assume it is less than the size of the array 
+     * @param length max size of the resulting array
+     * @return
+     */
+    public int[] extract(int[] numbers, int offset, int length) {
+        final int defect = numbers.length - (offset + length);
+        final int s = defect < 0 ? length + defect : length;
+        int[] result = new int[s];
+        for (int index = 0; index < s; index++) {
+            result[index] = numbers[index + offset];
+        }
+        return result;
+    }
+
+    /**
+     * Concatenate the numbers into a single number as if they were strings.
+     * Assume that the procedure does not suffer from the overflow.
+     * @param numbers integers to concatenate
+     * @return
+     */
+    public int concatenate(int[] numbers) {
+        final String merged = IntStream.of(numbers)
+            .mapToObj(number -> "" + number)
+            .collect(Collectors.joining());
+        return Integer.parseInt(merged, 10);
+    }
+
+    /**
+     * Convert the string into its characters' ASCII codes.
+     * @param str input string
+     * @return
+     */
+    private int[] toAsciiCodes(String str) {
+        return str.chars()
+            .toArray();
+    }
+}

algorithms-miscellaneous-3/src/main/java/com/baeldung/folding/Main.java

@@ -0,0 +1,17 @@
+package com.baeldung.folding;
+
+/**
+ * Code snippet for article "A Guide to the Folding Technique".
+ *  
+ * @author A.Shcherbakov
+ *
+ */
+public class Main {
+
+    public static void main(String... arg) {
+        FoldingHash hasher = new FoldingHash();
+        final String str = "Java language";
+        System.out.println(hasher.hash(str, 2, 100_000));
+        System.out.println(hasher.hash(str, 3, 1_000));
+    }
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/checksortedlist/SortedListCheckerUnitTest.java

@@ -0,0 +1,106 @@
+package com.baeldung.algorithms.checksortedlist;
+
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingComparators;
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingIterativeApproach;
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingOrderingClass;
+import static com.baeldung.algorithms.checksortedlist.SortedListChecker.checkIfSortedUsingRecursion;
+import static java.util.Arrays.asList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class SortedListCheckerUnitTest {
+
+    private List<String> sortedListOfString;
+    private List<String> unsortedListOfString;
+    private List<String> singletonList;
+
+    private List<Employee> employeesSortedByName;
+    private List<Employee> employeesNotSortedByName;
+
+    @Before
+    public void setUp() {
+        sortedListOfString = asList("Canada", "HK", "LA", "NJ", "NY");
+        unsortedListOfString = asList("LA", "HK", "NJ", "NY", "Canada");
+        singletonList = Collections.singletonList("NY");
+
+        employeesSortedByName = asList(new Employee(1L, "John"), new Employee(2L, "Kevin"), new Employee(3L, "Mike"));
+        employeesNotSortedByName = asList(new Employee(1L, "Kevin"), new Employee(2L, "John"), new Employee(3L, "Mike"));
+    }
+
+    @Test
+    public void givenSortedList_whenUsingIterativeApproach_thenReturnTrue() {
+        assertThat(checkIfSortedUsingIterativeApproach(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenSingleElementList_whenUsingIterativeApproach_thenReturnTrue() {
+        assertThat(checkIfSortedUsingIterativeApproach(singletonList)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingIterativeApproach_thenReturnFalse() {
+        assertThat(checkIfSortedUsingIterativeApproach(unsortedListOfString)).isFalse();
+    }
+
+    @Test
+    public void givenSortedListOfEmployees_whenUsingIterativeApproach_thenReturnTrue() {
+        assertThat(checkIfSortedUsingIterativeApproach(employeesSortedByName, Comparator.comparing(Employee::getName))).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedListOfEmployees_whenUsingIterativeApproach_thenReturnFalse() {
+        assertThat(checkIfSortedUsingIterativeApproach(employeesNotSortedByName, Comparator.comparing(Employee::getName))).isFalse();
+    }
+
+    @Test
+    public void givenSortedList_whenUsingRecursion_thenReturnTrue() {
+        assertThat(checkIfSortedUsingRecursion(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenSingleElementList_whenUsingRecursion_thenReturnTrue() {
+        assertThat(checkIfSortedUsingRecursion(singletonList)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingRecursion_thenReturnFalse() {
+        assertThat(checkIfSortedUsingRecursion(unsortedListOfString)).isFalse();
+    }
+
+    @Test
+    public void givenSortedList_whenUsingGuavaOrdering_thenReturnTrue() {
+        assertThat(checkIfSortedUsingOrderingClass(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingGuavaOrdering_thenReturnFalse() {
+        assertThat(checkIfSortedUsingOrderingClass(unsortedListOfString)).isFalse();
+    }
+
+    @Test
+    public void givenSortedListOfEmployees_whenUsingGuavaOrdering_thenReturnTrue() {
+        assertThat(checkIfSortedUsingOrderingClass(employeesSortedByName, Comparator.comparing(Employee::getName))).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedListOfEmployees_whenUsingGuavaOrdering_thenReturnFalse() {
+        assertThat(checkIfSortedUsingOrderingClass(employeesNotSortedByName, Comparator.comparing(Employee::getName))).isFalse();
+    }
+
+    @Test
+    public void givenSortedList_whenUsingGuavaComparators_thenReturnTrue() {
+        assertThat(checkIfSortedUsingComparators(sortedListOfString)).isTrue();
+    }
+
+    @Test
+    public void givenUnsortedList_whenUsingGuavaComparators_thenReturnFalse() {
+        assertThat(checkIfSortedUsingComparators(unsortedListOfString)).isFalse();
+    }
+
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/enumstatemachine/LeaveRequestStateUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.algorithms.enumstatemachine;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class LeaveRequestStateUnitTest {
+
+    @Test
+    public void givenLeaveRequest_whenStateEscalated_thenResponsibleIsTeamLeader() {
+        LeaveRequestState state = LeaveRequestState.Escalated;
+
+        assertEquals(state.responsiblePerson(), "Team Leader");
+    }
+
+
+    @Test
+    public void givenLeaveRequest_whenStateApproved_thenResponsibleIsDepartmentManager() {
+        LeaveRequestState state = LeaveRequestState.Approved;
+
+        assertEquals(state.responsiblePerson(), "Department Manager");
+    }
+
+    @Test
+    public void givenLeaveRequest_whenNextStateIsCalled_thenStateIsChanged() {
+        LeaveRequestState state = LeaveRequestState.Submitted;
+
+        state = state.nextState();
+        assertEquals(state, LeaveRequestState.Escalated);
+
+        state = state.nextState();
+        assertEquals(state, LeaveRequestState.Approved);
+
+        state = state.nextState();
+        assertEquals(state, LeaveRequestState.Approved);
+    }
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/graphcycledetection/GraphCycleDetectionUnitTest.java

@@ -0,0 +1,56 @@
+package com.baeldung.algorithms.graphcycledetection;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+import com.baeldung.algorithms.graphcycledetection.domain.Graph;
+import com.baeldung.algorithms.graphcycledetection.domain.Vertex;
+
+public class GraphCycleDetectionUnitTest {
+
+    @Test
+    public void givenGraph_whenCycleExists_thenReturnTrue() {
+
+        Vertex vertexA = new Vertex("A");
+        Vertex vertexB = new Vertex("B");
+        Vertex vertexC = new Vertex("C");
+        Vertex vertexD = new Vertex("D");
+
+        Graph graph = new Graph();
+        graph.addVertex(vertexA);
+        graph.addVertex(vertexB);
+        graph.addVertex(vertexC);
+        graph.addVertex(vertexD);
+
+        graph.addEdge(vertexA, vertexB);
+        graph.addEdge(vertexB, vertexC);
+        graph.addEdge(vertexC, vertexA);
+        graph.addEdge(vertexD, vertexC);
+
+        assertTrue(graph.hasCycle());
+    }
+
+    @Test
+    public void givenGraph_whenNoCycleExists_thenReturnFalse() {
+
+        Vertex vertexA = new Vertex("A");
+        Vertex vertexB = new Vertex("B");
+        Vertex vertexC = new Vertex("C");
+        Vertex vertexD = new Vertex("D");
+
+        Graph graph = new Graph();
+        graph.addVertex(vertexA);
+        graph.addVertex(vertexB);
+        graph.addVertex(vertexC);
+        graph.addVertex(vertexD);
+
+        graph.addEdge(vertexA, vertexB);
+        graph.addEdge(vertexB, vertexC);
+        graph.addEdge(vertexA, vertexC);
+        graph.addEdge(vertexD, vertexC);
+
+        assertFalse(graph.hasCycle());
+    }
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/twopointertechnique/LinkedListFindMiddleUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.algorithms.twopointertechnique;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class LinkedListFindMiddleUnitTest {
+
+    LinkedListFindMiddle linkedListFindMiddle = new LinkedListFindMiddle();
+
+    @Test
+    public void givenLinkedListOfMyNodes_whenLinkedListFindMiddle_thenCorrect() {
+
+        MyNode<String> head = createNodesList(8);
+
+        assertThat(linkedListFindMiddle.findMiddle(head)).isEqualTo("4");
+
+        head = createNodesList(9);
+
+        assertThat(linkedListFindMiddle.findMiddle(head)).isEqualTo("5");
+    }
+
+    private static MyNode<String> createNodesList(int n) {
+
+        MyNode<String> head = new MyNode<String>("1");
+        MyNode<String> current = head;
+
+        for (int i = 2; i <= n; i++) {
+            MyNode<String> newNode = new MyNode<String>(String.valueOf(i));
+            current.setNext(newNode);
+            current = newNode;
+        }
+
+        return head;
+    }
+
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/twopointertechnique/RotateArrayUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.twopointertechnique;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class RotateArrayUnitTest {
+
+    private RotateArray rotateArray = new RotateArray();
+
+    private int[] inputArray;
+
+    private int step;
+
+    @Test
+    public void givenAnArrayOfIntegers_whenRotateKsteps_thenCorrect() {
+
+        inputArray = new int[] { 1, 2, 3, 4, 5, 6, 7 };
+        step = 4;
+
+        rotateArray.rotate(inputArray, step);
+
+        assertThat(inputArray).containsExactly(new int[] { 4, 5, 6, 7, 1, 2, 3 });
+    }
+
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/algorithms/twopointertechnique/TwoSumUnitTest.java

@@ -0,0 +1,56 @@
+package com.baeldung.algorithms.twopointertechnique;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class TwoSumUnitTest {
+
+    private TwoSum twoSum = new TwoSum();
+
+    private int[] sortedArray;
+
+    private int targetValue;
+
+    @Test
+    public void givenASortedArrayOfIntegers_whenTwoSumSlow_thenPairExists() {
+
+        sortedArray = new int[] { 0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9 };
+
+        targetValue = 12;
+
+        assertTrue(twoSum.twoSumSlow(sortedArray, targetValue));
+    }
+
+    @Test
+    public void givenASortedArrayOfIntegers_whenTwoSumSlow_thenPairDoesNotExists() {
+
+        sortedArray = new int[] { 0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9 };
+
+        targetValue = 20;
+
+        assertFalse(twoSum.twoSumSlow(sortedArray, targetValue));
+    }
+
+    @Test
+    public void givenASortedArrayOfIntegers_whenTwoSum_thenPairExists() {
+
+        sortedArray = new int[] { 0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9 };
+
+        targetValue = 12;
+
+        assertTrue(twoSum.twoSum(sortedArray, targetValue));
+    }
+
+    @Test
+    public void givenASortedArrayOfIntegers_whenTwoSum_thenPairDoesNotExists() {
+
+        sortedArray = new int[] { 0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9 };
+
+        targetValue = 20;
+
+        assertFalse(twoSum.twoSum(sortedArray, targetValue));
+    }
+
+}

algorithms-miscellaneous-3/src/test/java/com/baeldung/folding/FoldingHashUnitTest.java

@@ -0,0 +1,54 @@
+package com.baeldung.folding;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class FoldingHashUnitTest {
+
+    @Test
+    public void givenStringJavaLanguage_whenSize2Capacity100000_then48933() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int value = hasher.hash("Java language", 2, 100_000);
+        assertEquals(value, 48933);
+    }
+
+    @Test
+    public void givenStringVaJaLanguage_whenSize2Capacity100000_thenSameAsJavaLanguage() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int java = hasher.hash("Java language", 2, 100_000);
+        final int vaja = hasher.hash("vaJa language", 2, 100_000);
+        assertTrue(java == vaja);
+    }
+
+    @Test
+    public void givenSingleElementArray_whenOffset0Size2_thenSingleElement() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 5 }, 0, 2);
+        assertArrayEquals(new int[] { 5 }, value);
+    }
+
+    @Test
+    public void givenFiveElementArray_whenOffset0Size3_thenFirstThreeElements() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 0, 3);
+        assertArrayEquals(new int[] { 1, 2, 3 }, value);
+    }
+
+    @Test
+    public void givenFiveElementArray_whenOffset1Size2_thenTwoElements() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 1, 2);
+        assertArrayEquals(new int[] { 2, 3 }, value);
+    }
+
+    @Test
+    public void givenFiveElementArray_whenOffset2SizeTooBig_thenElementsToTheEnd() throws Exception {
+        final FoldingHash hasher = new FoldingHash();
+        final int[] value = hasher.extract(new int[] { 1, 2, 3, 4, 5 }, 2, 2000);
+        assertArrayEquals(new int[] { 3, 4, 5 }, value);
+    }
+
+}

algorithms-sorting/pom.xml

@@ -49,7 +49,6 @@
     </build>
 
     <properties>
-        <lombok.version>1.16.12</lombok.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>

animal-sniffer-mvn-plugin/pom.xml

@@ -3,9 +3,9 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.baeldung</groupId>
     <artifactId>animal-sniffer-mvn-plugin</artifactId>
-    <packaging>jar</packaging>
     <version>1.0-SNAPSHOT</version>
     <name>animal-sniffer-mvn-plugin</name>
+    <packaging>jar</packaging>
     <url>http://maven.apache.org</url>
 
     <parent>

annotations/pom.xml

@@ -3,8 +3,8 @@
     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>annotations</artifactId>
-    <packaging>pom</packaging>
     <name>annotations</name>
+    <packaging>pom</packaging>
     
     <parent>
         <artifactId>parent-modules</artifactId>

antlr/pom.xml

@@ -10,6 +10,14 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.antlr</groupId>
+            <artifactId>antlr4-runtime</artifactId>
+            <version>${antlr.version}</version>
+        </dependency>
+    </dependencies>
+
     <build>
         <plugins>
             <plugin>
@@ -44,13 +52,7 @@
             </plugin>
         </plugins>
     </build>
-    <dependencies>
-        <dependency>
-            <groupId>org.antlr</groupId>
-            <artifactId>antlr4-runtime</artifactId>
-            <version>${antlr.version}</version>
-        </dependency>
-    </dependencies>
+    	
     <properties>
         <antlr.version>4.7.1</antlr.version>
         <mojo.version>3.0.0</mojo.version>

apache-avro/pom.xml

@@ -7,14 +7,6 @@
     <version>0.0.1-SNAPSHOT</version>
 	<name>apache-avro</name>
 
-    <properties>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <compiler-plugin.version>3.5</compiler-plugin.version>
-        <avro.version>1.8.2</avro.version>
-        <java.version>1.8</java.version>
-        <slf4j.version>1.7.25</slf4j.version>
-    </properties>
-	
     <parent>
         <groupId>com.baeldung</groupId>
         <artifactId>parent-modules</artifactId>
@@ -25,7 +17,7 @@
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>4.10</version>
+            <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -85,4 +77,12 @@
             </plugin>
         </plugins>
     </build>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <compiler-plugin.version>3.5</compiler-plugin.version>
+        <avro.version>1.8.2</avro.version>
+        <slf4j.version>1.7.25</slf4j.version>
+    </properties>
+	
 </project>

apache-curator/pom.xml

@@ -3,8 +3,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>apache-curator</artifactId>
     <version>0.0.1-SNAPSHOT</version>
-    <packaging>jar</packaging>
 	<name>apache-curator</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -39,7 +39,7 @@
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
-            <version>${jackson-databind.version}</version>
+            <version>${jackson.version}</version>
         </dependency>
         <!-- test scoped -->
         <dependency>
@@ -59,7 +59,6 @@
     <properties>
         <curator.version>4.0.1</curator.version>
         <zookeeper.version>3.4.11</zookeeper.version>
-        <jackson-databind.version>2.9.4</jackson-databind.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <avaitility.version>1.7.0</avaitility.version>

apache-cxf/sse-jaxrs/sse-jaxrs-client/pom.xml

@@ -12,9 +12,18 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
-    <properties>
-        <cxf-version>3.2.0</cxf-version>
-    </properties>
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.cxf</groupId>
+            <artifactId>cxf-rt-rs-client</artifactId>
+            <version>${cxf-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.cxf</groupId>
+            <artifactId>cxf-rt-rs-sse</artifactId>
+            <version>${cxf-version}</version>
+        </dependency>
+    </dependencies>
 
     <build>
         <plugins>
@@ -45,17 +54,8 @@
         </plugins>
     </build>
 
-    <dependencies>
-        <dependency>
-            <groupId>org.apache.cxf</groupId>
-            <artifactId>cxf-rt-rs-client</artifactId>
-            <version>${cxf-version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.cxf</groupId>
-            <artifactId>cxf-rt-rs-sse</artifactId>
-            <version>${cxf-version}</version>
-        </dependency>
-    </dependencies>
+    <properties>
+        <cxf-version>3.2.0</cxf-version>
+    </properties>
 
 </project>

apache-cxf/sse-jaxrs/sse-jaxrs-server/pom.xml

@@ -13,11 +13,28 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
-    <properties>
-        <liberty-maven-plugin.version>2.4.2</liberty-maven-plugin.version>
-        <failOnMissingWebXml>false</failOnMissingWebXml>
-        <openliberty-version>18.0.0.2</openliberty-version>
-    </properties>
+    <dependencies>
+
+        <dependency>
+            <groupId>javax.ws.rs</groupId>
+            <artifactId>javax.ws.rs-api</artifactId>
+            <version>2.1</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>javax.enterprise</groupId>
+            <artifactId>cdi-api</artifactId>
+            <version>2.0</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>javax.json.bind</groupId>
+            <artifactId>javax.json.bind-api</artifactId>
+            <version>1.0</version>
+            <scope>provided</scope>
+        </dependency>
+
+    </dependencies>
 
     <build>
         <finalName>${project.artifactId}</finalName>
@@ -59,27 +76,10 @@
         </plugins>
     </build>
 
-    <dependencies>
-
-        <dependency>
-            <groupId>javax.ws.rs</groupId>
-            <artifactId>javax.ws.rs-api</artifactId>
-            <version>2.1</version>
-            <scope>provided</scope>
-        </dependency>
-        <dependency>
-            <groupId>javax.enterprise</groupId>
-            <artifactId>cdi-api</artifactId>
-            <version>2.0</version>
-            <scope>provided</scope>
-        </dependency>
-        <dependency>
-            <groupId>javax.json.bind</groupId>
-            <artifactId>javax.json.bind-api</artifactId>
-            <version>1.0</version>
-            <scope>provided</scope>
-        </dependency>
-
-    </dependencies>
+    <properties>
+        <liberty-maven-plugin.version>2.4.2</liberty-maven-plugin.version>
+        <failOnMissingWebXml>false</failOnMissingWebXml>
+        <openliberty-version>18.0.0.2</openliberty-version>
+    </properties>
 
 </project>

apache-fop/README.md

@@ -3,7 +3,3 @@
 ## Core Java Cookbooks and Examples
 
 ### Relevant Articles: 
-- [Immutable ArrayList in Java](http://www.baeldung.com/java-immutable-list)
-- [Java - Reading a Large File Efficiently](http://www.baeldung.com/java-read-lines-large-file)
-- [Java InputStream to String](http://www.baeldung.com/convert-input-stream-to-string)
-

apache-geode/pom.xml

@@ -12,22 +12,6 @@
         <artifactId>parent-modules</artifactId>
         <version>1.0.0-SNAPSHOT</version>
     </parent>
-    
-    <properties>
-        <geode.core>1.6.0</geode.core>
-    </properties>
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
 
     <dependencies>
         <dependency>
@@ -38,8 +22,24 @@
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>RELEASE</version>
+            <version>${junit.version}</version>
         </dependency>
     </dependencies>
     
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${java.version}</source>
+                    <target>${java.version}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+	
+    <properties>
+        <geode.core>1.6.0</geode.core>
+    </properties>
 </project>

apache-geode/src/test/java/com/baeldung/geode/GeodeSamplesLiveTest.java

@@ -21,7 +21,7 @@ import java.util.stream.Stream;
 
 import static org.junit.Assert.assertEquals;
 
-public class GeodeSamplesIntegrationTest {
+public class GeodeSamplesLiveTest {
 
     ClientCache cache = null;
     Region<String, String> region = null;

apache-meecrowave/pom.xml

@@ -6,52 +6,64 @@
     <version>0.0.1</version>
     <name>apache-meecrowave</name>
     <description>A sample REST API application with Meecrowave</description>
+    
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
 
-    <properties>
-        <maven.compiler.source>1.8</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
-    </properties>
     <dependencies>
         <!-- https://mvnrepository.com/artifact/org.apache.meecrowave/meecrowave-core -->
         <dependency>
             <groupId>org.apache.meecrowave</groupId>
             <artifactId>meecrowave-core</artifactId>
-            <version>1.2.1</version>
+            <version>${meecrowave-core.version}</version>
         </dependency>
         <!-- https://mvnrepository.com/artifact/org.apache.meecrowave/meecrowave-jpa -->
         <dependency>
             <groupId>org.apache.meecrowave</groupId>
             <artifactId>meecrowave-jpa</artifactId>
-            <version>1.2.1</version>
+            <version>${meecrowave-jpa.version}</version>
         </dependency>
 
         <dependency>
             <groupId>com.squareup.okhttp3</groupId>
             <artifactId>okhttp</artifactId>
-            <version>3.10.0</version>
+            <version>${okhttp.version}</version>
         </dependency>
         <dependency>
             <groupId>org.apache.meecrowave</groupId>
             <artifactId>meecrowave-junit</artifactId>
-            <version>1.2.0</version>
+            <version>${meecrowave-junit.version}</version>
             <scope>test</scope>
         </dependency>
         <!-- https://mvnrepository.com/artifact/junit/junit -->
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>4.10</version>
+            <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
-
     </dependencies>
+	
     <build>
         <plugins>
             <plugin>
                 <groupId>org.apache.meecrowave</groupId>
                 <artifactId>meecrowave-maven-plugin</artifactId>
-                <version>1.2.1</version>
+                <version>${meecrowave-maven-plugin.version}</version>
             </plugin>
         </plugins>
     </build>
+	
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+		<meecrowave-junit.version>1.2.0</meecrowave-junit.version>
+		<okhttp.version>3.10.0</okhttp.version>
+		<meecrowave-jpa.version>1.2.1</meecrowave-jpa.version>
+		<meecrowave-core.version>1.2.1</meecrowave-core.version>
+		<meecrowave-maven-plugin.version>1.2.1</meecrowave-maven-plugin.version>
+    </properties>
 </project>

apache-meecrowave/src/test/java/com/baeldung/meecrowave/ArticleEndpointsUnitTest.java

@@ -17,7 +17,7 @@ import okhttp3.Request;
 import okhttp3.Response;
 
 @RunWith(MonoMeecrowave.Runner.class)
-public class ArticleEndpointsTest {
+public class ArticleEndpointsUnitTest {
     
     @ConfigurationInject
     private Meecrowave.Builder config;

apache-olingo/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [OData Protocol Guide](https://www.baeldung.com/odata)

apache-olingo/Samples.md

@@ -0,0 +1,21 @@
+##  OData test URLs
+
+This following table contains test URLs that can be used with the Olingo V2 demo project.
+
+| URL                                      | Description                                     |
+|------------------------------------------|-------------------------------------------------|
+| `http://localhost:8180/odata/$metadata`  | fetch OData metadata document |
+| `http://localhost:8180/odata/CarMakers?$top=10&$skip=10` | Get 10 entities starting at offset 10 |
+| `http://localhost:8180/odata/CarMakers?$count` | Return total count of entities in this set |
+| `http://localhost:8180/odata/CarMakers?$filter=startswith(Name,'B')` | Return entities where the *Name* property starts with 'B' |
+| `http://localhost:8180/odata/CarModels?$filter=Year eq 2008 and CarMakerDetails/Name eq 'BWM'` | Return *CarModel* entities where the *Name* property of its maker  starts with 'B' |
+| `http://localhost:8180/odata/CarModels(1L)?$expand=CarMakerDetails` | Return the *CarModel* with primary key '1', along with its maker|
+| `http://localhost:8180/odata/CarModels(1L)?$select=Name,Sku` | Return the *CarModel* with primary key '1', returing only its *Name* and *Sku* properties |
+| `http://localhost:8180/odata/CarModels?$orderBy=Name asc,Sku desc` | Return *CarModel* entities, ordered by the their *Name* and *Sku* properties |
+| `http://localhost:8180/odata/CarModels?$format=json` | Return *CarModel* entities, using a JSON representation|
+
+
+
+
+
+

apache-olingo/olingo2/.gitignore

@@ -0,0 +1,29 @@
+HELP.md
+/target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+/build/
+
+### VS Code ###
+.vscode/

apache-olingo/olingo2/pom.xml

@@ -0,0 +1,89 @@
+<?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>org.baeldung.examples.olingo2</groupId>
+	<artifactId>olingo2-sample</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>olingo2-sample</name>
+	<description>Sample Olingo 2 Project</description>
+
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>2.1.3.RELEASE</version>
+		<relativePath /> <!-- lookup parent from repository -->
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-jersey</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-jpa</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>com.h2database</groupId>
+			<artifactId>h2</artifactId>
+			<scope>runtime</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-configuration-processor</artifactId>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+
+		<!-- Olingo 2 Dependencies -->
+		<dependency>
+			<groupId>org.apache.olingo</groupId>
+			<artifactId>olingo-odata2-core</artifactId>
+			<version>${olingo2.version}</version>
+			<!-- Avoid jax-rs version conflict by excluding Olingo's version -->
+			<exclusions>
+				<exclusion>
+					<groupId>javax.ws.rs</groupId>
+					<artifactId>javax.ws.rs-api</artifactId>
+				</exclusion>
+			</exclusions>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.olingo</groupId>
+			<artifactId>olingo-odata2-jpa-processor-core</artifactId>
+			<version>${olingo2.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.olingo</groupId>
+			<artifactId>olingo-odata2-jpa-processor-ref</artifactId>
+			<version>${olingo2.version}</version>
+			<exclusions>
+				<exclusion>
+					<groupId>org.eclipse.persistence</groupId>
+					<artifactId>eclipselink</artifactId>
+				</exclusion>
+			</exclusions>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+
+	<properties>
+		<java.version>1.8</java.version>
+		<olingo2.version>2.0.11</olingo2.version>
+	</properties>
+
+</project>

apache-olingo/olingo2/src/main/java/org/baeldung/examples/olingo2/CarsODataJPAServiceFactory.java

@@ -0,0 +1,298 @@
+package org.baeldung.examples.olingo2;
+
+import java.util.List;
+import java.util.Map;
+
+import javax.persistence.EntityGraph;
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.FlushModeType;
+import javax.persistence.LockModeType;
+import javax.persistence.Persistence;
+import javax.persistence.Query;
+import javax.persistence.StoredProcedureQuery;
+import javax.persistence.SynchronizationType;
+import javax.persistence.TypedQuery;
+import javax.persistence.criteria.CriteriaBuilder;
+import javax.persistence.criteria.CriteriaDelete;
+import javax.persistence.criteria.CriteriaQuery;
+import javax.persistence.criteria.CriteriaUpdate;
+import javax.persistence.metamodel.Metamodel;
+import javax.servlet.http.HttpServletRequest;
+
+import org.apache.olingo.odata2.api.processor.ODataContext;
+import org.apache.olingo.odata2.jpa.processor.api.ODataJPAContext;
+import org.apache.olingo.odata2.jpa.processor.api.ODataJPAServiceFactory;
+import org.apache.olingo.odata2.jpa.processor.api.exception.ODataJPARuntimeException;
+import org.baeldung.examples.olingo2.JerseyConfig.EntityManagerFilter;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.orm.jpa.EntityManagerFactoryUtils;
+import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
+import org.springframework.stereotype.Component;
+
+/**
+ * ODataJPAServiceFactory implementation for our sample domain 
+ * @author Philippe
+ *
+ */
+@Component
+public class CarsODataJPAServiceFactory extends ODataJPAServiceFactory {
+
+    private static final Logger log = LoggerFactory.getLogger(CarsODataJPAServiceFactory.class);
+
+    public CarsODataJPAServiceFactory() {
+        // Enable detailed error messages (useful for debugging)
+        setDetailErrors(true);
+    }
+
+    /**
+     * This method will be called by Olingo on every request to
+     * initialize the ODataJPAContext that will be used. 
+     */
+    @Override
+    public ODataJPAContext initializeODataJPAContext() throws ODataJPARuntimeException {
+
+        log.info("[I32] >>> initializeODataJPAContext()");
+        ODataJPAContext ctx = getODataJPAContext();
+        ODataContext octx = ctx.getODataContext();
+        HttpServletRequest request = (HttpServletRequest)octx.getParameter(ODataContext.HTTP_SERVLET_REQUEST_OBJECT);
+        EntityManager em = (EntityManager)request.getAttribute(EntityManagerFilter.EM_REQUEST_ATTRIBUTE);
+                
+        // Here we're passing the EM that was created by the EntityManagerFilter (see JerseyConfig)
+        ctx.setEntityManager(new EntityManagerWrapper(em));
+        ctx.setPersistenceUnitName("default");
+        
+        // We're managing the EM's lifecycle, so we must inform Olingo that it should not
+        // try to manage transactions and/or persistence sessions
+        ctx.setContainerManaged(true);                
+        return ctx;
+    }
+
+    static class EntityManagerWrapper implements EntityManager {
+
+        private EntityManager delegate;
+
+        public void persist(Object entity) {
+            log.info("[I68] persist: entity.class=" + entity.getClass()
+                .getSimpleName());
+            delegate.persist(entity);
+            // delegate.flush();
+        }
+
+        public <T> T merge(T entity) {
+            log.info("[I74] merge: entity.class=" + entity.getClass()
+                .getSimpleName());
+            return delegate.merge(entity);
+        }
+
+        public void remove(Object entity) {
+            log.info("[I78] remove: entity.class=" + entity.getClass()
+                .getSimpleName());
+            delegate.remove(entity);
+        }
+
+        public <T> T find(Class<T> entityClass, Object primaryKey) {
+            return delegate.find(entityClass, primaryKey);
+        }
+
+        public <T> T find(Class<T> entityClass, Object primaryKey, Map<String, Object> properties) {
+            return delegate.find(entityClass, primaryKey, properties);
+        }
+
+        public <T> T find(Class<T> entityClass, Object primaryKey, LockModeType lockMode) {
+            return delegate.find(entityClass, primaryKey, lockMode);
+        }
+
+        public <T> T find(Class<T> entityClass, Object primaryKey, LockModeType lockMode, Map<String, Object> properties) {
+            return delegate.find(entityClass, primaryKey, lockMode, properties);
+        }
+
+        public <T> T getReference(Class<T> entityClass, Object primaryKey) {
+            return delegate.getReference(entityClass, primaryKey);
+        }
+
+        public void flush() {
+            delegate.flush();
+        }
+
+        public void setFlushMode(FlushModeType flushMode) {
+            delegate.setFlushMode(flushMode);
+        }
+
+        public FlushModeType getFlushMode() {
+            return delegate.getFlushMode();
+        }
+
+        public void lock(Object entity, LockModeType lockMode) {
+            delegate.lock(entity, lockMode);
+        }
+
+        public void lock(Object entity, LockModeType lockMode, Map<String, Object> properties) {
+            delegate.lock(entity, lockMode, properties);
+        }
+
+        public void refresh(Object entity) {
+            delegate.refresh(entity);
+        }
+
+        public void refresh(Object entity, Map<String, Object> properties) {
+            delegate.refresh(entity, properties);
+        }
+
+        public void refresh(Object entity, LockModeType lockMode) {
+            delegate.refresh(entity, lockMode);
+        }
+
+        public void refresh(Object entity, LockModeType lockMode, Map<String, Object> properties) {
+            delegate.refresh(entity, lockMode, properties);
+        }
+
+        public void clear() {
+            delegate.clear();
+        }
+
+        public void detach(Object entity) {
+            delegate.detach(entity);
+        }
+
+        public boolean contains(Object entity) {
+            return delegate.contains(entity);
+        }
+
+        public LockModeType getLockMode(Object entity) {
+            return delegate.getLockMode(entity);
+        }
+
+        public void setProperty(String propertyName, Object value) {
+            delegate.setProperty(propertyName, value);
+        }
+
+        public Map<String, Object> getProperties() {
+            return delegate.getProperties();
+        }
+
+        public Query createQuery(String qlString) {
+            return delegate.createQuery(qlString);
+        }
+
+        public <T> TypedQuery<T> createQuery(CriteriaQuery<T> criteriaQuery) {
+            return delegate.createQuery(criteriaQuery);
+        }
+
+        public Query createQuery(CriteriaUpdate updateQuery) {
+            return delegate.createQuery(updateQuery);
+        }
+
+        public Query createQuery(CriteriaDelete deleteQuery) {
+            return delegate.createQuery(deleteQuery);
+        }
+
+        public <T> TypedQuery<T> createQuery(String qlString, Class<T> resultClass) {
+            return delegate.createQuery(qlString, resultClass);
+        }
+
+        public Query createNamedQuery(String name) {
+            return delegate.createNamedQuery(name);
+        }
+
+        public <T> TypedQuery<T> createNamedQuery(String name, Class<T> resultClass) {
+            return delegate.createNamedQuery(name, resultClass);
+        }
+
+        public Query createNativeQuery(String sqlString) {
+            return delegate.createNativeQuery(sqlString);
+        }
+
+        public Query createNativeQuery(String sqlString, Class resultClass) {
+            return delegate.createNativeQuery(sqlString, resultClass);
+        }
+
+        public Query createNativeQuery(String sqlString, String resultSetMapping) {
+            return delegate.createNativeQuery(sqlString, resultSetMapping);
+        }
+
+        public StoredProcedureQuery createNamedStoredProcedureQuery(String name) {
+            return delegate.createNamedStoredProcedureQuery(name);
+        }
+
+        public StoredProcedureQuery createStoredProcedureQuery(String procedureName) {
+            return delegate.createStoredProcedureQuery(procedureName);
+        }
+
+        public StoredProcedureQuery createStoredProcedureQuery(String procedureName, Class... resultClasses) {
+            return delegate.createStoredProcedureQuery(procedureName, resultClasses);
+        }
+
+        public StoredProcedureQuery createStoredProcedureQuery(String procedureName, String... resultSetMappings) {
+            return delegate.createStoredProcedureQuery(procedureName, resultSetMappings);
+        }
+
+        public void joinTransaction() {
+            delegate.joinTransaction();
+        }
+
+        public boolean isJoinedToTransaction() {
+            return delegate.isJoinedToTransaction();
+        }
+
+        public <T> T unwrap(Class<T> cls) {
+            return delegate.unwrap(cls);
+        }
+
+        public Object getDelegate() {
+            return delegate.getDelegate();
+        }
+
+        public void close() {
+            log.info("[I229] close");
+            delegate.close();
+        }
+
+        public boolean isOpen() {
+            boolean isOpen = delegate.isOpen();
+            log.info("[I236] isOpen: " + isOpen);
+            return isOpen;
+        }
+
+        public EntityTransaction getTransaction() {
+            log.info("[I240] getTransaction()");
+            return delegate.getTransaction();
+        }
+
+        public EntityManagerFactory getEntityManagerFactory() {
+            return delegate.getEntityManagerFactory();
+        }
+
+        public CriteriaBuilder getCriteriaBuilder() {
+            return delegate.getCriteriaBuilder();
+        }
+
+        public Metamodel getMetamodel() {
+            return delegate.getMetamodel();
+        }
+
+        public <T> EntityGraph<T> createEntityGraph(Class<T> rootType) {
+            return delegate.createEntityGraph(rootType);
+        }
+
+        public EntityGraph<?> createEntityGraph(String graphName) {
+            return delegate.createEntityGraph(graphName);
+        }
+
+        public EntityGraph<?> getEntityGraph(String graphName) {
+            return delegate.getEntityGraph(graphName);
+        }
+
+        public <T> List<EntityGraph<? super T>> getEntityGraphs(Class<T> entityClass) {
+            return delegate.getEntityGraphs(entityClass);
+        }
+
+        public EntityManagerWrapper(EntityManager delegate) {
+            this.delegate = delegate;
+        }
+
+    }
+
+}

apache-olingo/olingo2/src/main/java/org/baeldung/examples/olingo2/JerseyConfig.java

@@ -0,0 +1,125 @@
+    package org.baeldung.examples.olingo2;
+
+import java.io.IOException;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.servlet.ServletContext;
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.ApplicationPath;
+import javax.ws.rs.Path;
+import javax.ws.rs.container.ContainerRequestContext;
+import javax.ws.rs.container.ContainerRequestFilter;
+import javax.ws.rs.container.ContainerResponseContext;
+import javax.ws.rs.container.ContainerResponseFilter;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.ext.Provider;
+
+import org.apache.olingo.odata2.api.ODataServiceFactory;
+import org.apache.olingo.odata2.core.rest.ODataRootLocator;
+import org.apache.olingo.odata2.core.rest.app.ODataApplication;
+import org.glassfish.jersey.server.ResourceConfig;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Component;
+
+/**
+ * Jersey JAX-RS configuration
+ * @author Philippe
+ *
+ */
+@Component
+@ApplicationPath("/odata")
+public class JerseyConfig extends ResourceConfig {
+    
+    
+    public JerseyConfig(CarsODataJPAServiceFactory serviceFactory, EntityManagerFactory emf) {        
+        
+        ODataApplication app = new ODataApplication();
+        
+        app
+          .getClasses()
+          .forEach( c -> {
+              // Avoid using the default RootLocator, as we want
+              // a Spring Managed one
+              if ( !ODataRootLocator.class.isAssignableFrom(c)) {
+                  register(c);
+              }
+          });
+        
+        register(new CarsRootLocator(serviceFactory)); 
+        register( new EntityManagerFilter(emf));
+    }
+    
+    /**
+     * This filter handles the EntityManager transaction lifecycle.
+     * @author Philippe
+     *
+     */
+    @Provider
+    public static class EntityManagerFilter implements ContainerRequestFilter, ContainerResponseFilter {
+
+        private static final Logger log = LoggerFactory.getLogger(EntityManagerFilter.class);
+        public static final String EM_REQUEST_ATTRIBUTE = EntityManagerFilter.class.getName() + "_ENTITY_MANAGER";
+
+        private final EntityManagerFactory emf;
+
+        @Context
+        private HttpServletRequest httpRequest;
+
+        public EntityManagerFilter(EntityManagerFactory emf) {
+            this.emf = emf;
+        }
+
+        @Override
+        public void filter(ContainerRequestContext ctx) throws IOException {
+            log.info("[I60] >>> filter");
+            EntityManager em = this.emf.createEntityManager();
+            httpRequest.setAttribute(EM_REQUEST_ATTRIBUTE, em);
+
+            // Start a new transaction unless we have a simple GET
+            if (!"GET".equalsIgnoreCase(ctx.getMethod())) {
+                em.getTransaction()
+                    .begin();
+            }
+        }
+
+        @Override
+        public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext) throws IOException {
+
+            log.info("[I68] <<< filter");
+            EntityManager em = (EntityManager) httpRequest.getAttribute(EM_REQUEST_ATTRIBUTE);
+
+            if (!"GET".equalsIgnoreCase(requestContext.getMethod())) {
+                EntityTransaction t = em.getTransaction();
+                if (t.isActive()) {
+                    if (!t.getRollbackOnly()) {
+                        t.commit();
+                    }
+                }
+            }
+
+            em.close();
+
+        }
+
+    }
+
+    @Path("/")
+    public static class CarsRootLocator extends ODataRootLocator {
+
+        private CarsODataJPAServiceFactory serviceFactory;
+
+        public CarsRootLocator(CarsODataJPAServiceFactory serviceFactory) {
+            this.serviceFactory = serviceFactory;
+        }
+
+        @Override
+        public ODataServiceFactory getServiceFactory() {
+            return this.serviceFactory;
+        }
+
+    }
+
+}

apache-olingo/olingo2/src/main/java/org/baeldung/examples/olingo2/Olingo2SampleApplication.java

@@ -0,0 +1,14 @@
+package org.baeldung.examples.olingo2;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
+
+@SpringBootApplication
+public class Olingo2SampleApplication extends SpringBootServletInitializer {
+
+    public static void main(String[] args) {        
+        SpringApplication.run(Olingo2SampleApplication.class);
+    }
+}

apache-olingo/olingo2/src/main/java/org/baeldung/examples/olingo2/domain/CarMaker.java

@@ -0,0 +1,115 @@
+package org.baeldung.examples.olingo2.domain;
+
+import java.util.List;
+
+import javax.persistence.CascadeType;
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.OneToMany;
+import javax.persistence.Table;
+import javax.validation.constraints.NotNull;
+
+@Entity
+@Table(name = "car_maker")
+public class CarMaker {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @NotNull
+    @Column(name = "name")
+    private String name;
+
+    @OneToMany(mappedBy = "maker", orphanRemoval = true, cascade = CascadeType.ALL)
+    private List<CarModel> models;
+
+    /**
+     * @return the id
+     */
+    public Long getId() {
+        return id;
+    }
+
+    /**
+     * @param id the id to set
+     */
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    /**
+     * @return the name
+     */
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * @param name the name to set
+     */
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    /**
+     * @return the models
+     */
+    public List<CarModel> getModels() {
+        return models;
+    }
+
+    /**
+     * @param models the models to set
+     */
+    public void setModels(List<CarModel> models) {
+        this.models = models;
+    }
+
+    /* (non-Javadoc)
+     * @see java.lang.Object#hashCode()
+     */
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((id == null) ? 0 : id.hashCode());
+        result = prime * result + ((models == null) ? 0 : models.hashCode());
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    /* (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        CarMaker other = (CarMaker) obj;
+        if (id == null) {
+            if (other.id != null)
+                return false;
+        } else if (!id.equals(other.id))
+            return false;
+        if (models == null) {
+            if (other.models != null)
+                return false;
+        } else if (!models.equals(other.models))
+            return false;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        return true;
+    }
+
+}

apache-olingo/olingo2/src/main/java/org/baeldung/examples/olingo2/domain/CarModel.java

@@ -0,0 +1,159 @@
+package org.baeldung.examples.olingo2.domain;
+
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.ManyToOne;
+import javax.persistence.Table;
+import javax.validation.constraints.NotNull;
+
+@Entity
+@Table(name = "car_model")
+public class CarModel {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
+    private Long id;
+
+    @NotNull
+    private String name;
+
+    @NotNull
+    private Integer year;
+
+    @NotNull
+    private String sku;
+
+    @ManyToOne(optional = false, fetch = FetchType.LAZY)
+    @JoinColumn(name = "maker_fk")
+    private CarMaker maker;
+
+    /**
+     * @return the id
+     */
+    public Long getId() {
+        return id;
+    }
+
+    /**
+     * @param id the id to set
+     */
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    /**
+     * @return the name
+     */
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * @param name the name to set
+     */
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    /**
+     * @return the year
+     */
+    public Integer getYear() {
+        return year;
+    }
+
+    /**
+     * @param year the year to set
+     */
+    public void setYear(Integer year) {
+        this.year = year;
+    }
+
+    /**
+     * @return the sku
+     */
+    public String getSku() {
+        return sku;
+    }
+
+    /**
+     * @param sku the sku to set
+     */
+    public void setSku(String sku) {
+        this.sku = sku;
+    }
+
+    /**
+     * @return the maker
+     */
+    public CarMaker getMaker() {
+        return maker;
+    }
+
+    /**
+     * @param maker the maker to set
+     */
+    public void setMaker(CarMaker maker) {
+        this.maker = maker;
+    }
+
+    /* (non-Javadoc)
+     * @see java.lang.Object#hashCode()
+     */
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((id == null) ? 0 : id.hashCode());
+        result = prime * result + ((maker == null) ? 0 : maker.hashCode());
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        result = prime * result + ((sku == null) ? 0 : sku.hashCode());
+        result = prime * result + ((year == null) ? 0 : year.hashCode());
+        return result;
+    }
+
+    /* (non-Javadoc)
+     * @see java.lang.Object#equals(java.lang.Object)
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        CarModel other = (CarModel) obj;
+        if (id == null) {
+            if (other.id != null)
+                return false;
+        } else if (!id.equals(other.id))
+            return false;
+        if (maker == null) {
+            if (other.maker != null)
+                return false;
+        } else if (!maker.equals(other.maker))
+            return false;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        if (sku == null) {
+            if (other.sku != null)
+                return false;
+        } else if (!sku.equals(other.sku))
+            return false;
+        if (year == null) {
+            if (other.year != null)
+                return false;
+        } else if (!year.equals(other.year))
+            return false;
+        return true;
+    }
+
+}

apache-olingo/olingo2/src/main/resources/application.yml

@@ -0,0 +1,12 @@
+server:
+  port: 8080
+  
+spring:
+  jersey:
+    application-path: /odata
+    
+  jpa:
+    show-sql: true
+    open-in-view: false
+    hibernate:
+      ddl-auto: update

apache-olingo/olingo2/src/main/resources/data.sql

@@ -0,0 +1,12 @@
+insert into car_maker(id,name) values (1,'Special Motors');
+insert into car_maker(id,name) values (2,'BWM');
+insert into car_maker(id,name) values (3,'Dolores');
+
+insert into car_model(id,maker_fk,name,sku,year) values(1,1,'Muze','SM001',2018);
+insert into car_model(id,maker_fk,name,sku,year) values(2,1,'Empada','SM002',2008);
+
+insert into car_model(id,maker_fk,name,sku,year) values(4,2,'BWM-100','BWM100',2008);
+insert into car_model(id,maker_fk,name,sku,year) values(5,2,'BWM-200','BWM200',2009);
+insert into car_model(id,maker_fk,name,sku,year) values(6,2,'BWM-300','BWM300',2008);
+
+alter sequence hibernate_sequence restart with 100;

apache-olingo/olingo2/src/test/java/org/baeldung/examples/olingo2/Olingo2SampleApplicationTests.java

@@ -0,0 +1,16 @@
+package org.baeldung.examples.olingo2;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class Olingo2SampleApplicationTests {
+
+	@Test
+	public void contextLoads() {
+	}
+
+}

apache-olingo/olingo2/src/test/resources/olingo2-queries.json

@@ -0,0 +1,256 @@
+{
+	"info": {
+		"_postman_id": "afa8e1e5-ab0e-4f1d-8b99-b7d1f091f975",
+		"name": "OLingo2 - Cars",
+		"schema": "https://schema.getpostman.com/json/collection/v2.0.0/collection.json"
+	},
+	"item": [
+		{
+			"name": "GET Metadata",
+			"request": {
+				"method": "GET",
+				"header": [],
+				"body": {
+					"mode": "raw",
+					"raw": ""
+				},
+				"url": "http://localhost:8080/odata/$metadata"
+			},
+			"response": []
+		},
+		{
+			"name": "GET All CarMakers",
+			"request": {
+				"method": "GET",
+				"header": [],
+				"body": {
+					"mode": "raw",
+					"raw": ""
+				},
+				"url": "http://localhost:8080/odata/CarMakers"
+			},
+			"response": []
+		},
+		{
+			"name": "GET Makers with Pagination",
+			"request": {
+				"method": "GET",
+				"header": [],
+				"body": {
+					"mode": "raw",
+					"raw": ""
+				},
+				"url": {
+					"raw": "http://localhost:8080/odata/CarMakers?$top=1&$orderby=Name&$skip=3",
+					"protocol": "http",
+					"host": [
+						"localhost"
+					],
+					"port": "8080",
+					"path": [
+						"odata",
+						"CarMakers"
+					],
+					"query": [
+						{
+							"key": "$top",
+							"value": "1"
+						},
+						{
+							"key": "$orderby",
+							"value": "Name"
+						},
+						{
+							"key": "$skip",
+							"value": "3"
+						}
+					]
+				}
+			},
+			"response": []
+		},
+		{
+			"name": "GET Makers and Models",
+			"request": {
+				"method": "GET",
+				"header": [],
+				"body": {
+					"mode": "raw",
+					"raw": ""
+				},
+				"url": {
+					"raw": "http://localhost:8080/odata/CarMakers?$expand=CarModelDetails",
+					"protocol": "http",
+					"host": [
+						"localhost"
+					],
+					"port": "8080",
+					"path": [
+						"odata",
+						"CarMakers"
+					],
+					"query": [
+						{
+							"key": "$expand",
+							"value": "CarModelDetails"
+						}
+					]
+				}
+			},
+			"response": []
+		},
+		{
+			"name": "GET Makers with filter",
+			"request": {
+				"method": "GET",
+				"header": [
+					{
+						"key": "Accept",
+						"value": "application/json",
+						"type": "text"
+					}
+				],
+				"body": {
+					"mode": "raw",
+					"raw": ""
+				},
+				"url": {
+					"raw": "http://localhost:8080/odata/CarMakers?$filter=Name eq 'BWM'&$expand=CarModelDetails",
+					"protocol": "http",
+					"host": [
+						"localhost"
+					],
+					"port": "8080",
+					"path": [
+						"odata",
+						"CarMakers"
+					],
+					"query": [
+						{
+							"key": "$filter",
+							"value": "Name eq 'BWM'"
+						},
+						{
+							"key": "$expand",
+							"value": "CarModelDetails"
+						}
+					]
+				}
+			},
+			"response": []
+		},
+		{
+			"name": "Create CarMaker",
+			"request": {
+				"method": "POST",
+				"header": [
+					{
+						"key": "Content-Type",
+						"name": "Content-Type",
+						"value": "application/atom+xml",
+						"type": "text"
+					},
+					{
+						"key": "Accept",
+						"value": "application/atom+xml",
+						"type": "text"
+					}
+				],
+				"body": {
+					"mode": "raw",
+					"raw": "<?xml version=\"1.0\" encoding=\"utf-8\" ?> \r\n<entry xmlns:d=\"http://schemas.microsoft.com/ado/2007/08/dataservices\"\r\n    xmlns:m=\"http://schemas.microsoft.com/ado/2007/08/dataservices/metadata\" \r\n    xmlns=\"http://www.w3.org/2005/Atom\">\r\n  <title type=\"text\"></title> \r\n  <updated>2019-04-02T21:36:47Z</updated>\r\n  <author> \r\n    <name /> \r\n  </author> \r\n  <category term=\"default.CarMaker\"\r\n      scheme=\"http://schemas.microsoft.com/ado/2007/08/dataservices/scheme\" /> \r\n  <content type=\"application/xml\"> \r\n    <m:properties>\r\n      <d:Name>Lucien</d:Name>\r\n    </m:properties> \r\n  </content> \r\n</entry>"
+				},
+				"url": "http://localhost:8080/odata/CarMakers"
+			},
+			"response": []
+		},
+		{
+			"name": "Create CarModel",
+			"request": {
+				"method": "POST",
+				"header": [
+					{
+						"key": "Content-Type",
+						"name": "Content-Type",
+						"type": "text",
+						"value": "application/atom+xml"
+					},
+					{
+						"key": "Accept",
+						"type": "text",
+						"value": "application/atom+xml"
+					}
+				],
+				"body": {
+					"mode": "raw",
+					"raw": "<?xml version=\"1.0\" encoding=\"utf-8\" ?> \r\n<entry xmlns:d=\"http://schemas.microsoft.com/ado/2007/08/dataservices\"\r\n    xmlns:m=\"http://schemas.microsoft.com/ado/2007/08/dataservices/metadata\" \r\n    xmlns=\"http://www.w3.org/2005/Atom\">\r\n  <title type=\"text\"></title> \r\n  <updated>2019-04-02T21:36:47Z</updated>\r\n  <author> \r\n    <name /> \r\n  </author> \r\n  <link href=\"CarModels(1L)/CarMakerDetails\" \r\n    rel=\"http://schemas.microsoft.com/ado/2007/08/dataservices/related/CarMakerDetails\" \r\n    title=\"CarMakerDetails\" \r\n    type=\"application/atom+xml;type=entry\"></link>  \r\n  <category term=\"default.CarModel\"\r\n      scheme=\"http://schemas.microsoft.com/ado/2007/08/dataservices/scheme\" /> \r\n  <content type=\"application/xml\"> \r\n    <m:properties>\r\n\t    <d:Name>Tata</d:Name>\r\n\t    <d:Sku>TT101</d:Sku>\r\n\t    <d:Year>2018</d:Year>\r\n    </m:properties> \r\n  </content> \r\n</entry>"
+				},
+				"url": "http://localhost:8080/odata/CarModels"
+			},
+			"response": []
+		},
+		{
+			"name": "Update CarMaker",
+			"request": {
+				"method": "PUT",
+				"header": [
+					{
+						"key": "Content-Type",
+						"name": "Content-Type",
+						"type": "text",
+						"value": "application/atom+xml"
+					},
+					{
+						"key": "Accept",
+						"type": "text",
+						"value": "application/atom+xml"
+					}
+				],
+				"body": {
+					"mode": "raw",
+					"raw": "<?xml version=\"1.0\" encoding=\"utf-8\" ?> \r\n<entry xmlns:d=\"http://schemas.microsoft.com/ado/2007/08/dataservices\"\r\n    xmlns:m=\"http://schemas.microsoft.com/ado/2007/08/dataservices/metadata\" \r\n    xmlns=\"http://www.w3.org/2005/Atom\">\r\n  <title type=\"text\"></title> \r\n  <updated>2019-04-02T21:36:47Z</updated>\r\n  <author> \r\n    <name /> \r\n  </author> \r\n  <category term=\"default.CarMaker\"\r\n      scheme=\"http://schemas.microsoft.com/ado/2007/08/dataservices/scheme\" /> \r\n  <content type=\"application/xml\"> \r\n    <m:properties>\r\n      <d:Id>5</d:Id>\r\n      <d:Name>KaiserWagen</d:Name>\r\n    </m:properties> \r\n  </content> \r\n</entry>"
+				},
+				"url": "http://localhost:8080/odata/CarMakers(5L)"
+			},
+			"response": []
+		},
+		{
+			"name": "All CarModels",
+			"request": {
+				"method": "GET",
+				"header": [],
+				"body": {
+					"mode": "raw",
+					"raw": ""
+				},
+				"url": "http://localhost:8080/odata/CarModels"
+			},
+			"response": []
+		},
+		{
+			"name": "Delete CarModel",
+			"request": {
+				"method": "DELETE",
+				"header": [
+					{
+						"key": "Content-Type",
+						"name": "Content-Type",
+						"type": "text",
+						"value": "application/atom+xml"
+					},
+					{
+						"key": "Accept",
+						"type": "text",
+						"value": "application/atom+xml"
+					}
+				],
+				"body": {
+					"mode": "raw",
+					"raw": ""
+				},
+				"url": "http://localhost:8080/odata/CarModels(100L)"
+			},
+			"response": []
+		}
+	]
+}

apache-pulsar/pom.xml

@@ -11,12 +11,14 @@
         <dependency>
             <groupId>org.apache.pulsar</groupId>
             <artifactId>pulsar-client</artifactId>
-            <version>2.1.1-incubating</version>
+            <version>${pulsar-client.version}</version>
             <scope>compile</scope>
         </dependency>
     </dependencies>
+	
     <properties>
         <maven.compiler.target>1.8</maven.compiler.target>
         <maven.compiler.source>1.8</maven.compiler.source>
+		<pulsar-client.version>2.1.1-incubating</pulsar-client.version>
     </properties>
 </project>

apache-solrj/pom.xml

@@ -4,8 +4,8 @@
     <groupId>com.baeldung</groupId>
     <artifactId>apache-solrj</artifactId>
     <version>0.0.1-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>apache-solrj</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>

apache-spark/README.md

@@ -1,3 +1,4 @@
 ### Relevant articles
 
 - [Introduction to Apache Spark](http://www.baeldung.com/apache-spark)
+- [Building a Data Pipeline with Kafka, Spark Streaming and Cassandra](https://www.baeldung.com/kafka-spark-data-pipeline)

apache-spark/pom.xml

@@ -4,8 +4,8 @@
     <groupId>com.baeldung</groupId>
     <artifactId>apache-spark</artifactId>
     <version>1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>apache-spark</name>
+    <packaging>jar</packaging>
     <url>http://maven.apache.org</url>
 
     <parent>
@@ -15,16 +15,79 @@
     </parent>
 
     <dependencies>
-        <!-- https://mvnrepository.com/artifact/org.apache.spark/spark-core_2.10 -->
         <dependency>
             <groupId>org.apache.spark</groupId>
-            <artifactId>spark-core_2.10</artifactId>
+            <artifactId>spark-core_2.11</artifactId>
             <version>${org.apache.spark.spark-core.version}</version>
+            <scope>provided</scope>
         </dependency>
+		<dependency>
+    		<groupId>org.apache.spark</groupId>
+    		<artifactId>spark-sql_2.11</artifactId>
+    		<version>${org.apache.spark.spark-sql.version}</version>
+    		<scope>provided</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.spark</groupId>
+			<artifactId>spark-streaming_2.11</artifactId>
+			<version>${org.apache.spark.spark-streaming.version}</version>
+			<scope>provided</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.spark</groupId>
+			<artifactId>spark-streaming-kafka-0-10_2.11</artifactId>
+			<version>${org.apache.spark.spark-streaming-kafka.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>com.datastax.spark</groupId>
+			<artifactId>spark-cassandra-connector_2.11</artifactId>
+			<version>${com.datastax.spark.spark-cassandra-connector.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>com.datastax.spark</groupId>
+			<artifactId>spark-cassandra-connector-java_2.11</artifactId>
+			<version>${com.datastax.spark.spark-cassandra-connector-java.version}</version>
+		</dependency>
     </dependencies>
 
+	<build>
+    	<plugins>
+    	  	<plugin>
+    			<groupId>org.apache.maven.plugins</groupId>
+    			<artifactId>maven-compiler-plugin</artifactId>
+    			<version>${maven-compiler-plugin.version}</version>
+    			<configuration>
+      				<source>${java.version}</source>
+      				<target>${java.version}</target>
+    			</configuration>
+  			</plugin>
+      		<plugin>
+        		<artifactId>maven-assembly-plugin</artifactId>
+        		<executions>
+          			<execution>
+            			<phase>package</phase>
+            			<goals>
+              				<goal>single</goal>
+            			</goals>
+          			</execution>
+        		</executions>
+        		<configuration>
+          			<descriptorRefs>
+            			<descriptorRef>jar-with-dependencies</descriptorRef>
+          			</descriptorRefs>
+        		</configuration>
+      		</plugin>
+   		</plugins>
+  	</build>
+
     <properties>
-        <org.apache.spark.spark-core.version>2.2.0</org.apache.spark.spark-core.version>
+        <org.apache.spark.spark-core.version>2.3.0</org.apache.spark.spark-core.version>
+        <org.apache.spark.spark-sql.version>2.3.0</org.apache.spark.spark-sql.version>
+        <org.apache.spark.spark-streaming.version>2.3.0</org.apache.spark.spark-streaming.version>
+        <org.apache.spark.spark-streaming-kafka.version>2.3.0</org.apache.spark.spark-streaming-kafka.version>
+        <com.datastax.spark.spark-cassandra-connector.version>2.3.0</com.datastax.spark.spark-cassandra-connector.version>
+        <com.datastax.spark.spark-cassandra-connector-java.version>1.5.2</com.datastax.spark.spark-cassandra-connector-java.version>
+		<maven-compiler-plugin.version>3.2</maven-compiler-plugin.version>
     </properties>
 
 </project>

apache-spark/src/main/java/com/baeldung/data/pipeline/Word.java

@@ -0,0 +1,25 @@
+package com.baeldung.data.pipeline;
+
+import java.io.Serializable;
+
+public class Word implements Serializable {
+    private static final long serialVersionUID = 1L;
+    private String word;
+    private int count;
+    Word(String word, int count) {
+        this.word = word;
+        this.count = count;
+    }
+    public String getWord() {
+        return word;
+    }
+    public void setWord(String word) {
+        this.word = word;
+    }
+    public int getCount() {
+        return count;
+    }
+    public void setCount(int count) {
+        this.count = count;
+    }
+}

apache-spark/src/main/java/com/baeldung/data/pipeline/WordCountingApp.java

@@ -0,0 +1,80 @@
+package com.baeldung.data.pipeline;
+
+import static com.datastax.spark.connector.japi.CassandraJavaUtil.javaFunctions;
+import static com.datastax.spark.connector.japi.CassandraJavaUtil.mapToRow;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.serialization.StringDeserializer;
+import org.apache.log4j.Level;
+import org.apache.log4j.Logger;
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.streaming.Durations;
+import org.apache.spark.streaming.api.java.JavaDStream;
+import org.apache.spark.streaming.api.java.JavaInputDStream;
+import org.apache.spark.streaming.api.java.JavaPairDStream;
+import org.apache.spark.streaming.api.java.JavaStreamingContext;
+import org.apache.spark.streaming.kafka010.ConsumerStrategies;
+import org.apache.spark.streaming.kafka010.KafkaUtils;
+import org.apache.spark.streaming.kafka010.LocationStrategies;
+
+import scala.Tuple2;
+
+public class WordCountingApp {
+
+    public static void main(String[] args) throws InterruptedException {
+        Logger.getLogger("org")
+            .setLevel(Level.OFF);
+        Logger.getLogger("akka")
+            .setLevel(Level.OFF);
+
+        Map<String, Object> kafkaParams = new HashMap<>();
+        kafkaParams.put("bootstrap.servers", "localhost:9092");
+        kafkaParams.put("key.deserializer", StringDeserializer.class);
+        kafkaParams.put("value.deserializer", StringDeserializer.class);
+        kafkaParams.put("group.id", "use_a_separate_group_id_for_each_stream");
+        kafkaParams.put("auto.offset.reset", "latest");
+        kafkaParams.put("enable.auto.commit", false);
+
+        Collection<String> topics = Arrays.asList("messages");
+
+        SparkConf sparkConf = new SparkConf();
+        sparkConf.setMaster("local[2]");
+        sparkConf.setAppName("WordCountingApp");
+        sparkConf.set("spark.cassandra.connection.host", "127.0.0.1");
+
+        JavaStreamingContext streamingContext = new JavaStreamingContext(sparkConf, Durations.seconds(1));
+
+        JavaInputDStream<ConsumerRecord<String, String>> messages = KafkaUtils.createDirectStream(streamingContext, LocationStrategies.PreferConsistent(), ConsumerStrategies.<String, String> Subscribe(topics, kafkaParams));
+
+        JavaPairDStream<String, String> results = messages.mapToPair(record -> new Tuple2<>(record.key(), record.value()));
+
+        JavaDStream<String> lines = results.map(tuple2 -> tuple2._2());
+
+        JavaDStream<String> words = lines.flatMap(x -> Arrays.asList(x.split("\\s+"))
+            .iterator());
+
+        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(s -> new Tuple2<>(s, 1))
+            .reduceByKey((i1, i2) -> i1 + i2);
+
+        wordCounts.foreachRDD(javaRdd -> {
+            Map<String, Integer> wordCountMap = javaRdd.collectAsMap();
+            for (String key : wordCountMap.keySet()) {
+                List<Word> wordList = Arrays.asList(new Word(key, wordCountMap.get(key)));
+                JavaRDD<Word> rdd = streamingContext.sparkContext()
+                    .parallelize(wordList);
+                javaFunctions(rdd).writerBuilder("vocabulary", "words", mapToRow(Word.class))
+                    .saveToCassandra();
+            }
+        });
+
+        streamingContext.start();
+        streamingContext.awaitTermination();
+    }
+}

apache-spark/src/main/java/com/baeldung/data/pipeline/WordCountingAppWithCheckpoint.java

@@ -0,0 +1,97 @@
+package com.baeldung.data.pipeline;
+
+import static com.datastax.spark.connector.japi.CassandraJavaUtil.javaFunctions;
+import static com.datastax.spark.connector.japi.CassandraJavaUtil.mapToRow;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.common.serialization.StringDeserializer;
+import org.apache.log4j.Level;
+import org.apache.log4j.Logger;
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.apache.spark.api.java.function.Function2;
+import org.apache.spark.streaming.Durations;
+import org.apache.spark.streaming.StateSpec;
+import org.apache.spark.streaming.api.java.JavaDStream;
+import org.apache.spark.streaming.api.java.JavaInputDStream;
+import org.apache.spark.streaming.api.java.JavaMapWithStateDStream;
+import org.apache.spark.streaming.api.java.JavaPairDStream;
+import org.apache.spark.streaming.api.java.JavaStreamingContext;
+import org.apache.spark.streaming.kafka010.ConsumerStrategies;
+import org.apache.spark.streaming.kafka010.KafkaUtils;
+import org.apache.spark.streaming.kafka010.LocationStrategies;
+
+import scala.Tuple2;
+
+public class WordCountingAppWithCheckpoint {
+
+    public static JavaSparkContext sparkContext;
+
+    public static void main(String[] args) throws InterruptedException {
+
+        Logger.getLogger("org")
+            .setLevel(Level.OFF);
+        Logger.getLogger("akka")
+            .setLevel(Level.OFF);
+
+        Map<String, Object> kafkaParams = new HashMap<>();
+        kafkaParams.put("bootstrap.servers", "localhost:9092");
+        kafkaParams.put("key.deserializer", StringDeserializer.class);
+        kafkaParams.put("value.deserializer", StringDeserializer.class);
+        kafkaParams.put("group.id", "use_a_separate_group_id_for_each_stream");
+        kafkaParams.put("auto.offset.reset", "latest");
+        kafkaParams.put("enable.auto.commit", false);
+
+        Collection<String> topics = Arrays.asList("messages");
+
+        SparkConf sparkConf = new SparkConf();
+        sparkConf.setMaster("local[2]");
+        sparkConf.setAppName("WordCountingAppWithCheckpoint");
+        sparkConf.set("spark.cassandra.connection.host", "127.0.0.1");
+
+        JavaStreamingContext streamingContext = new JavaStreamingContext(sparkConf, Durations.seconds(1));
+
+        sparkContext = streamingContext.sparkContext();
+
+        streamingContext.checkpoint("./.checkpoint");
+
+        JavaInputDStream<ConsumerRecord<String, String>> messages = KafkaUtils.createDirectStream(streamingContext, LocationStrategies.PreferConsistent(), ConsumerStrategies.<String, String> Subscribe(topics, kafkaParams));
+
+        JavaPairDStream<String, String> results = messages.mapToPair(record -> new Tuple2<>(record.key(), record.value()));
+
+        JavaDStream<String> lines = results.map(tuple2 -> tuple2._2());
+
+        JavaDStream<String> words = lines.flatMap(x -> Arrays.asList(x.split("\\s+"))
+            .iterator());
+
+        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(s -> new Tuple2<>(s, 1))
+            .reduceByKey((Function2<Integer, Integer, Integer>) (i1, i2) -> i1 + i2);
+
+        JavaMapWithStateDStream<String, Integer, Integer, Tuple2<String, Integer>> cumulativeWordCounts = wordCounts.mapWithState(StateSpec.function((word, one, state) -> {
+            int sum = one.orElse(0) + (state.exists() ? state.get() : 0);
+            Tuple2<String, Integer> output = new Tuple2<>(word, sum);
+            state.update(sum);
+            return output;
+        }));
+
+        cumulativeWordCounts.foreachRDD(javaRdd -> {
+            List<Tuple2<String, Integer>> wordCountList = javaRdd.collect();
+            for (Tuple2<String, Integer> tuple : wordCountList) {
+                List<Word> wordList = Arrays.asList(new Word(tuple._1, tuple._2));
+                JavaRDD<Word> rdd = sparkContext.parallelize(wordList);
+                javaFunctions(rdd).writerBuilder("vocabulary", "words", mapToRow(Word.class))
+                    .saveToCassandra();
+            }
+        });
+
+        streamingContext.start();
+        streamingContext.awaitTermination();
+    }
+}

apache-velocity/pom.xml

@@ -4,8 +4,8 @@
     <groupId>com.baeldung</groupId>
     <version>0.1-SNAPSHOT</version>
     <artifactId>apache-velocity</artifactId>
-    <packaging>war</packaging>
     <name>apache-velocity</name>
+    <packaging>war</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -59,7 +59,6 @@
     </build>
 
     <properties>
-        <jstl.version>1.2</jstl.version>
         <org.apache.httpcomponents.version>4.5.2</org.apache.httpcomponents.version>
         <velocity-version>1.7</velocity-version>
         <velocity-tools-version>2.0</velocity-tools-version>

autovalue/README.md

@@ -1,3 +1,4 @@
 ### Relevant Articles:
 - [Introduction to AutoValue](http://www.baeldung.com/introduction-to-autovalue)
 - [Introduction to AutoFactory](http://www.baeldung.com/autofactory)
+- [Google AutoService](https://www.baeldung.com/google-autoservice)

autovalue/pom.xml

@@ -29,6 +29,12 @@
                 </exclusion>
             </exclusions>
         </dependency>
+        <dependency>
+            <groupId>com.google.auto.service</groupId>
+            <artifactId>auto-service</artifactId>
+            <version>${auto-service.version}</version>
+            <optional>true</optional>
+        </dependency>
 
         <dependency>
             <groupId>com.google.inject</groupId>
@@ -40,6 +46,7 @@
     <properties>
         <auto-value.version>1.3</auto-value.version>
         <auto-factory.version>1.0-beta5</auto-factory.version>
+        <auto-service.version>1.0-rc5</auto-service.version>
         <guice.version>4.2.0</guice.version>
     </properties>
 

autovalue/src/main/java/com/baeldung/autofactory/provided/IntermediateAssembler.java

@@ -1,8 +1,9 @@
 package com.baeldung.autofactory.provided;
 
+import com.baeldung.autofactory.model.Camera;
 import com.google.auto.factory.AutoFactory;
 import com.google.auto.factory.Provided;
-import javafx.scene.Camera;
+
 
 import javax.inject.Provider;
 

autovalue/src/main/java/com/baeldung/autoservice/BingTranslationServiceProvider.java

@@ -0,0 +1,14 @@
+package com.baeldung.autoservice;
+
+import com.google.auto.service.AutoService;
+
+import java.util.Locale;
+
+@AutoService(TranslationService.class)
+public class BingTranslationServiceProvider implements TranslationService {
+    @Override
+    public String translate(String message, Locale from, Locale to) {
+        // implementation details
+        return message + " (translated by Bing)"; 
+    }
+}

autovalue/src/main/java/com/baeldung/autoservice/GoogleTranslationServiceProvider.java

@@ -0,0 +1,14 @@
+package com.baeldung.autoservice;
+
+import com.google.auto.service.AutoService;
+
+import java.util.Locale;
+
+@AutoService(TranslationService.class)
+public class GoogleTranslationServiceProvider implements TranslationService {
+    @Override
+    public String translate(String message, Locale from, Locale to) {
+        // implementation details
+        return message + " (translated by Google)"; 
+    }
+}

autovalue/src/main/java/com/baeldung/autoservice/TranslationService.java

@@ -0,0 +1,7 @@
+package com.baeldung.autoservice;
+
+import java.util.Locale;
+
+public interface TranslationService {
+    String translate(String message, Locale from, Locale to);
+}

autovalue/src/test/java/com/baeldung/autoservice/TranslationServiceUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.autoservice;
+
+import com.baeldung.autoservice.TranslationService;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ServiceLoader;
+import java.util.stream.StreamSupport;
+
+import static org.junit.Assert.assertEquals;
+
+public class TranslationServiceUnitTest {
+
+    private ServiceLoader<TranslationService> loader;
+
+    @Before
+    public void setUp() {
+        loader = ServiceLoader.load(TranslationService.class);
+    }
+
+    @Test
+    public void whenServiceLoaderLoads_thenLoadsAllProviders() {
+        long count = StreamSupport.stream(loader.spliterator(), false).count();
+        assertEquals(2, count);
+    }
+
+    @Test
+    public void whenServiceLoaderLoadsGoogleService_thenGoogleIsLoaded() {
+        TranslationService googleService = StreamSupport.stream(loader.spliterator(), false)
+          .filter(p -> p.getClass().getSimpleName().equals("GoogleTranslationServiceProvider"))
+          .findFirst()
+          .get();
+		
+        String message = "message";
+        assertEquals(message + " (translated by Google)", googleService.translate(message, null, null));
+    }
+}

aws-lambda/pom.xml

@@ -5,8 +5,8 @@
     <groupId>com.baeldung</groupId>
     <artifactId>aws-lambda</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>aws-lambda</name>
+    <packaging>jar</packaging>
 
     <parent>
         <artifactId>parent-modules</artifactId>

aws/README.md

@@ -4,7 +4,6 @@
 - [AWS S3 with Java](http://www.baeldung.com/aws-s3-java)
 - [AWS Lambda With Java](http://www.baeldung.com/java-aws-lambda)
 - [Managing EC2 Instances in Java](http://www.baeldung.com/ec2-java)
-- [http://www.baeldung.com/aws-s3-multipart-upload](https://github.com/eugenp/tutorials/tree/master/aws)
 - [Multipart Uploads in Amazon S3 with Java](http://www.baeldung.com/aws-s3-multipart-upload)
 - [Integration Testing with a Local DynamoDB Instance](http://www.baeldung.com/dynamodb-local-integration-tests)
 - [Using the JetS3t Java Client With Amazon S3](http://www.baeldung.com/jets3t-amazon-s3)

aws/pom.xml

@@ -4,8 +4,8 @@
     <groupId>com.baeldung</groupId>
     <artifactId>aws</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>aws</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>

axon/pom.xml

@@ -4,29 +4,61 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>axon</artifactId>
     <name>axon</name>
-        
+    <description>Basic Axon Framework with Spring Boot configuration tutorial</description>
+
     <parent>
-        <artifactId>parent-modules</artifactId>
         <groupId>com.baeldung</groupId>
-        <version>1.0.0-SNAPSHOT</version>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-boot-2</relativePath>
     </parent>
 
     <dependencies>
+        <dependency>
+            <groupId>org.axonframework</groupId>
+            <artifactId>axon-spring-boot-starter</artifactId>
+            <version>${axon.version}</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.axonframework</groupId>
+                    <artifactId>axon-server-connector</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+
         <dependency>
             <groupId>org.axonframework</groupId>
             <artifactId>axon-test</artifactId>
             <version>${axon.version}</version>
             <scope>test</scope>
         </dependency>
+
         <dependency>
-            <groupId>org.axonframework</groupId>
-            <artifactId>axon-core</artifactId>
-            <version>${axon.version}</version>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-autoconfigure</artifactId>
+            <version>${spring-boot.version}</version>
+            <scope>compile</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
         </dependency>
     </dependencies>
 
     <properties>
-        <axon.version>3.0.2</axon.version>
+        <axon.version>4.0.3</axon.version>
     </properties>
 
 </project>

axon/src/main/java/com/baeldung/axon/MessagesRunner.java

@@ -1,54 +0,0 @@
-package com.baeldung.axon;
-
-import com.baeldung.axon.aggregates.MessagesAggregate;
-import com.baeldung.axon.commands.CreateMessageCommand;
-import com.baeldung.axon.commands.MarkReadMessageCommand;
-import com.baeldung.axon.eventhandlers.MessagesEventHandler;
-import org.axonframework.commandhandling.AggregateAnnotationCommandHandler;
-import org.axonframework.commandhandling.CommandBus;
-import org.axonframework.commandhandling.SimpleCommandBus;
-import org.axonframework.commandhandling.gateway.CommandGateway;
-import org.axonframework.commandhandling.gateway.DefaultCommandGateway;
-import org.axonframework.eventhandling.AnnotationEventListenerAdapter;
-import org.axonframework.eventsourcing.EventSourcingRepository;
-import org.axonframework.eventsourcing.eventstore.EmbeddedEventStore;
-import org.axonframework.eventsourcing.eventstore.EventStore;
-import org.axonframework.eventsourcing.eventstore.inmemory.InMemoryEventStorageEngine;
-
-import java.util.UUID;
-
-public class MessagesRunner {
-
-    public static void main(String[] args) {
-        CommandBus commandBus = new SimpleCommandBus();
-
-        CommandGateway commandGateway = new DefaultCommandGateway(commandBus);
-
-        EventStore eventStore = new EmbeddedEventStore(new InMemoryEventStorageEngine());
-
-        EventSourcingRepository<MessagesAggregate> repository =
-                new EventSourcingRepository<>(MessagesAggregate.class, eventStore);
-
-
-        AggregateAnnotationCommandHandler<MessagesAggregate> messagesAggregateAggregateAnnotationCommandHandler =
-                new AggregateAnnotationCommandHandler<MessagesAggregate>(MessagesAggregate.class, repository);
-        messagesAggregateAggregateAnnotationCommandHandler.subscribe(commandBus);
-
-        final AnnotationEventListenerAdapter annotationEventListenerAdapter =
-                new AnnotationEventListenerAdapter(new MessagesEventHandler());
-        eventStore.subscribe(eventMessages -> eventMessages.forEach(e -> {
-                    try {
-                        annotationEventListenerAdapter.handle(e);
-                    } catch (Exception e1) {
-                        throw new RuntimeException(e1);
-
-                    }
-                }
-
-        ));
-
-        final String itemId = UUID.randomUUID().toString();
-        commandGateway.send(new CreateMessageCommand(itemId, "Hello, how is your day? :-)"));
-        commandGateway.send(new MarkReadMessageCommand(itemId));
-    }
-}

axon/src/main/java/com/baeldung/axon/OrderApplication.java

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

axon/src/main/java/com/baeldung/axon/aggregates/MessagesAggregate.java

@@ -1,36 +0,0 @@
-package com.baeldung.axon.aggregates;
-
-import com.baeldung.axon.commands.CreateMessageCommand;
-import com.baeldung.axon.commands.MarkReadMessageCommand;
-import com.baeldung.axon.events.MessageCreatedEvent;
-import com.baeldung.axon.events.MessageReadEvent;
-import org.axonframework.commandhandling.CommandHandler;
-import org.axonframework.commandhandling.model.AggregateIdentifier;
-import org.axonframework.eventhandling.EventHandler;
-
-import static org.axonframework.commandhandling.model.AggregateLifecycle.apply;
-
-
-public class MessagesAggregate {
-
-    @AggregateIdentifier
-    private String id;
-
-    public MessagesAggregate() {
-    }
-
-    @CommandHandler
-    public MessagesAggregate(CreateMessageCommand command) {
-        apply(new MessageCreatedEvent(command.getId(), command.getText()));
-    }
-
-    @EventHandler
-    public void on(MessageCreatedEvent event) {
-        this.id = event.getId();
-    }
-
-    @CommandHandler
-    public void markRead(MarkReadMessageCommand command) {
-        apply(new MessageReadEvent(id));
-    }
-}

axon/src/main/java/com/baeldung/axon/commandmodel/OrderAggregate.java

@@ -0,0 +1,58 @@
+package com.baeldung.axon.commandmodel;
+
+import static org.axonframework.modelling.command.AggregateLifecycle.apply;
+
+import org.axonframework.commandhandling.CommandHandler;
+import org.axonframework.eventsourcing.EventSourcingHandler;
+import org.axonframework.modelling.command.AggregateIdentifier;
+import org.axonframework.spring.stereotype.Aggregate;
+
+import com.baeldung.axon.coreapi.commands.ConfirmOrderCommand;
+import com.baeldung.axon.coreapi.commands.PlaceOrderCommand;
+import com.baeldung.axon.coreapi.commands.ShipOrderCommand;
+import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
+import com.baeldung.axon.coreapi.events.OrderPlacedEvent;
+import com.baeldung.axon.coreapi.events.OrderShippedEvent;
+
+@Aggregate
+public class OrderAggregate {
+
+    @AggregateIdentifier
+    private String orderId;
+    private boolean orderConfirmed;
+
+    @CommandHandler
+    public OrderAggregate(PlaceOrderCommand command) {
+        apply(new OrderPlacedEvent(command.getOrderId(), command.getProduct()));
+    }
+
+    @CommandHandler
+    public void handle(ConfirmOrderCommand command) {
+        apply(new OrderConfirmedEvent(orderId));
+    }
+
+    @CommandHandler
+    public void handle(ShipOrderCommand command) {
+        if (!orderConfirmed) {
+            throw new IllegalStateException("Cannot ship an order which has not been confirmed yet.");
+        }
+
+        apply(new OrderShippedEvent(orderId));
+    }
+
+    @EventSourcingHandler
+    public void on(OrderPlacedEvent event) {
+        this.orderId = event.getOrderId();
+        orderConfirmed = false;
+    }
+
+    @EventSourcingHandler
+    public void on(OrderConfirmedEvent event) {
+        orderConfirmed = true;
+    }
+
+    protected OrderAggregate() {
+        // Required by Axon to build a default Aggregate prior to Event Sourcing
+    }
+
+}