diff --git a/core-java-modules/core-java-jpms/README.md b/core-java-modules/core-java-jpms/README.md
new file mode 100644
index 0000000000..5c424711bc
--- /dev/null
+++ b/core-java-modules/core-java-jpms/README.md
@@ -0,0 +1,3 @@
+### Relevant Articles
+
+- [Design Strategies for Decoupling Java Modules](https://www.baeldung.com/java-modules-decoupling-design-strategies)
diff --git a/core-java-modules/core-java-lang-operators/pom.xml b/core-java-modules/core-java-lang-operators/pom.xml
new file mode 100644
index 0000000000..58cab9d507
--- /dev/null
+++ b/core-java-modules/core-java-lang-operators/pom.xml
@@ -0,0 +1,43 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-lang-operators</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-lang-operators</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-lang-operators</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <!-- testing -->
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+
+</project>
diff --git a/core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/incrementdecrementunaryoperators/IncrementDecrementUnaryOperatorUnitTest.java b/core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/incrementdecrementunaryoperators/IncrementDecrementUnaryOperatorUnitTest.java
new file mode 100644
index 0000000000..8fbc2eeab8
--- /dev/null
+++ b/core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/incrementdecrementunaryoperators/IncrementDecrementUnaryOperatorUnitTest.java
@@ -0,0 +1,64 @@
+package com.baeldung.incrementdecrementunaryoperators;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class IncrementDecrementUnaryOperatorUnitTest {
+
+    @Test
+    public void givenAnOperand_whenUsingPreIncrementUnaryOperator_thenOperandIsIncrementedByOne() {
+        int operand = 1;
+        ++operand;
+        assertThat(operand).isEqualTo(2);
+    }
+
+    @Test
+    public void givenANumber_whenUsingPreIncrementUnaryOperatorInEvaluation_thenNumberIsIncrementedByOne() {
+        int operand = 1;
+        int number = ++operand;
+        assertThat(number).isEqualTo(2);
+    }
+
+    @Test
+    public void givenAnOperand_whenUsingPreDecrementUnaryOperator_thenOperandIsDecrementedByOne() {
+        int operand = 1;
+        --operand;
+        assertThat(operand).isEqualTo(0);
+    }
+
+    @Test
+    public void givenANumber_whenUsingPreDecrementUnaryOperatorInEvaluation_thenNumberIsDecrementedByOne() {
+        int operand = 1;
+        int number = --operand;
+        assertThat(number).isEqualTo(0);
+    }
+
+    @Test
+    public void givenAnOperand_whenUsingPostIncrementUnaryOperator_thenOperandIsIncrementedByOne() {
+        int operand = 1;
+        operand++;
+        assertThat(operand).isEqualTo(2);
+    }
+
+    @Test
+    public void givenANumber_whenUsingPostIncrementUnaryOperatorInEvaluation_thenNumberIsSameAsOldValue() {
+        int operand = 1;
+        int number = operand++;
+        assertThat(number).isEqualTo(1);
+    }
+
+    @Test
+    public void givenAnOperand_whenUsingPostDecrementUnaryOperator_thenOperandIsDecrementedByOne() {
+        int operand = 1;
+        operand--;
+        assertThat(operand).isEqualTo(0);
+    }
+
+    @Test
+    public void givenANumber_whenUsingPostDecrementUnaryOperatorInEvaluation_thenNumberIsSameAsOldValue() {
+        int operand = 1;
+        int number = operand--;
+        assertThat(number).isEqualTo(1);
+    }
+}
diff --git a/core-java-modules/pom.xml b/core-java-modules/pom.xml
index 2dca62005d..ecf1f4147e 100644
--- a/core-java-modules/pom.xml
+++ b/core-java-modules/pom.xml
@@ -17,6 +17,7 @@
         <module>pre-jpms</module>
         <module>core-java-exceptions</module>
         <module>core-java-optional</module>
+        <module>core-java-lang-operators</module>
         <module>core-java-networking-2</module>
     </modules>
     
diff --git a/data-structures/README.md b/data-structures/README.md
index 2d92068390..5ea9657173 100644
--- a/data-structures/README.md
+++ b/data-structures/README.md
@@ -1,4 +1,5 @@
 ## Relevant articles:
 
-[The Trie Data Structure in Java](https://www.baeldung.com/trie-java)
-[Implementing a Binary Tree in Java](https://www.baeldung.com/java-binary-tree)
+- [The Trie Data Structure in Java](https://www.baeldung.com/trie-java)
+- [Implementing a Binary Tree in Java](https://www.baeldung.com/java-binary-tree)
+- [Depth First Search in Java](https://www.baeldung.com/java-depth-first-search)
diff --git a/persistence-modules/java-cassandra/pom.xml b/persistence-modules/java-cassandra/pom.xml
index 708d2b3c76..e7c93bc4e5 100644
--- a/persistence-modules/java-cassandra/pom.xml
+++ b/persistence-modules/java-cassandra/pom.xml
@@ -4,7 +4,7 @@
     <groupId>com.baeldung</groupId>
     <artifactId>java-cassandra</artifactId>
     <version>1.0.0-SNAPSHOT</version>
-	<name>java-cassandra</name>
+    <name>java-cassandra</name>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -29,6 +29,19 @@
             <version>${cassandra-unit.version}</version>
         </dependency>
 
+        <!-- DataStax Cassandra -->
+        <dependency>
+            <groupId>com.datastax.oss</groupId>
+            <artifactId>java-driver-core</artifactId>
+            <version>${datastax-cassandra.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>io.netty</groupId>
+            <artifactId>netty-handler</artifactId>
+            <version>${io-netty.version}</version>
+        </dependency>
+
     </dependencies>
 
     <build>
@@ -39,6 +52,8 @@
         <!-- Cassandra -->
         <cassandra-driver-core.version>3.1.2</cassandra-driver-core.version>
         <cassandra-unit.version>3.1.1.0</cassandra-unit.version>
+        <datastax-cassandra.version>4.1.0</datastax-cassandra.version>
+        <io-netty.version>4.1.34.Final</io-netty.version>
         <guava.version>18.0</guava.version>
     </properties>
 
diff --git a/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/Application.java b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/Application.java
new file mode 100644
index 0000000000..23140e0455
--- /dev/null
+++ b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/Application.java
@@ -0,0 +1,46 @@
+package com.baeldung.datastax.cassandra;
+
+import com.baeldung.datastax.cassandra.domain.Video;
+import com.baeldung.datastax.cassandra.repository.KeyspaceRepository;
+import com.baeldung.datastax.cassandra.repository.VideoRepository;
+import com.datastax.oss.driver.api.core.CqlSession;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.List;
+
+public class Application {
+
+    private static final Logger LOG = LoggerFactory.getLogger(Application.class);
+
+    public static void main(String[] args) {
+        new Application().run();
+    }
+
+    public void run() {
+        CassandraConnector connector = new CassandraConnector();
+        connector.connect("127.0.0.1", 9042, "datacenter1");
+        CqlSession session = connector.getSession();
+
+        KeyspaceRepository keyspaceRepository = new KeyspaceRepository(session);
+
+        keyspaceRepository.createKeyspace("testKeyspace", "SimpleStrategy", 1);
+        keyspaceRepository.useKeyspace("testKeyspace");
+
+        VideoRepository videoRepository = new VideoRepository(session);
+
+        videoRepository.createTable();
+
+        videoRepository.insertVideo(new Video("Video Title 1", Instant.now()));
+        videoRepository.insertVideo(new Video("Video Title 2",
+            Instant.now().minus(1, ChronoUnit.DAYS)));
+
+        List<Video> videos = videoRepository.selectAll();
+
+        videos.forEach(x -> LOG.info(x.toString()));
+
+        connector.close();
+    }
+}
diff --git a/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/CassandraConnector.java b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/CassandraConnector.java
new file mode 100644
index 0000000000..d0938d060a
--- /dev/null
+++ b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/CassandraConnector.java
@@ -0,0 +1,28 @@
+package com.baeldung.datastax.cassandra;
+
+import com.datastax.oss.driver.api.core.CqlSession;
+import com.datastax.oss.driver.api.core.CqlSessionBuilder;
+
+import java.net.InetSocketAddress;
+
+public class CassandraConnector {
+
+    private CqlSession session;
+
+    public void connect(final String node, final Integer port, final String dataCenter) {
+        CqlSessionBuilder builder = CqlSession.builder();
+        builder.addContactPoint(new InetSocketAddress(node, port));
+        builder.withLocalDatacenter(dataCenter);
+
+        session = builder.build();
+    }
+
+    public CqlSession getSession() {
+        return this.session;
+    }
+
+    public void close() {
+        session.close();
+    }
+
+}
diff --git a/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/domain/Video.java b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/domain/Video.java
new file mode 100644
index 0000000000..f62a600f16
--- /dev/null
+++ b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/domain/Video.java
@@ -0,0 +1,51 @@
+package com.baeldung.datastax.cassandra.domain;
+
+import java.time.Instant;
+import java.util.UUID;
+
+public class Video {
+
+    private UUID id;
+    private String title;
+    private Instant creationDate;
+
+    public Video(UUID id, String title, Instant creationDate) {
+        this.id = id;
+        this.title = title;
+        this.creationDate = creationDate;
+    }
+
+    public Video(String title, Instant creationDate) {
+        this.title = title;
+        this.creationDate = creationDate;
+    }
+
+    public UUID getId() {
+        return id;
+    }
+
+    public void setId(UUID id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Instant getCreationDate() {
+        return creationDate;
+    }
+
+    public void setCreationDate(Instant creationDate) {
+        this.creationDate = creationDate;
+    }
+
+    @Override
+    public String toString() {
+        return "[id:" + id.toString() + ", title:" + title + ", creationDate: " + creationDate.toString() + "]";
+    }
+}
diff --git a/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/repository/KeyspaceRepository.java b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/repository/KeyspaceRepository.java
new file mode 100644
index 0000000000..fd4581d055
--- /dev/null
+++ b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/repository/KeyspaceRepository.java
@@ -0,0 +1,27 @@
+package com.baeldung.datastax.cassandra.repository;
+
+import com.datastax.oss.driver.api.core.CqlSession;
+
+public class KeyspaceRepository {
+    private final CqlSession session;
+
+    public KeyspaceRepository(CqlSession session) {
+        this.session = session;
+    }
+
+    public void createKeyspace(String keyspaceName, String replicationStrategy, int numberOfReplicas) {
+        StringBuilder sb = new StringBuilder("CREATE KEYSPACE IF NOT EXISTS ").append(keyspaceName)
+            .append(" WITH replication = {")
+            .append("'class':'").append(replicationStrategy)
+            .append("','replication_factor':").append(numberOfReplicas)
+            .append("};");
+
+        final String query = sb.toString();
+
+        session.execute(query);
+    }
+
+    public void useKeyspace(String keyspace) {
+        session.execute("USE " + keyspace);
+    }
+}
diff --git a/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/repository/VideoRepository.java b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/repository/VideoRepository.java
new file mode 100644
index 0000000000..9a09d77072
--- /dev/null
+++ b/persistence-modules/java-cassandra/src/main/java/com/baeldung/datastax/cassandra/repository/VideoRepository.java
@@ -0,0 +1,94 @@
+package com.baeldung.datastax.cassandra.repository;
+
+import com.baeldung.datastax.cassandra.domain.Video;
+import com.datastax.oss.driver.api.core.CqlIdentifier;
+import com.datastax.oss.driver.api.core.CqlSession;
+import com.datastax.oss.driver.api.core.cql.BoundStatement;
+import com.datastax.oss.driver.api.core.cql.PreparedStatement;
+import com.datastax.oss.driver.api.core.cql.ResultSet;
+import com.datastax.oss.driver.api.core.cql.SimpleStatement;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+public class VideoRepository {
+
+    private static final String TABLE_NAME = "videos";
+
+    private final CqlSession session;
+
+    public VideoRepository(CqlSession session) {
+        this.session = session;
+    }
+
+    public void createTable() {
+        createTable(null);
+    }
+
+    public void createTable(String keyspace) {
+        StringBuilder sb = new StringBuilder("CREATE TABLE IF NOT EXISTS ").append(TABLE_NAME).append(" (")
+            .append("video_id UUID,")
+            .append("title TEXT,")
+            .append("creation_date TIMESTAMP,")
+            .append("PRIMARY KEY(video_id));");
+
+        String query = sb.toString();
+
+        executeStatement(SimpleStatement.newInstance(query), keyspace);
+    }
+
+    public UUID insertVideo(Video video) {
+        return insertVideo(video, null);
+    }
+
+    public UUID insertVideo(Video video, String keyspace) {
+        UUID videoId = UUID.randomUUID();
+
+        video.setId(videoId);
+
+        String absoluteTableName = keyspace != null ? keyspace + "." + TABLE_NAME: TABLE_NAME;
+
+        StringBuilder sb = new StringBuilder("INSERT INTO ").append(absoluteTableName)
+            .append("(video_id, title, creation_date) values (:video_id, :title, :creation_date)");
+
+        PreparedStatement preparedStatement = session.prepare(sb.toString());
+
+        BoundStatement statement = preparedStatement.bind()
+            .setUuid("video_id", video.getId())
+            .setString("title", video.getTitle())
+            .setInstant("creation_date", video.getCreationDate());
+
+        session.execute(statement);
+
+        return videoId;
+    }
+
+    public List<Video> selectAll() {
+        return selectAll(null);
+    }
+
+    public List<Video> selectAll(String keyspace) {
+        StringBuilder sb = new StringBuilder("SELECT * FROM ").append(TABLE_NAME);
+
+        String query = sb.toString();
+
+        ResultSet resultSet = executeStatement(SimpleStatement.newInstance(query), keyspace);
+
+        List<Video> result = new ArrayList<>();
+
+        resultSet.forEach(x -> result.add(
+            new Video(x.getUuid("video_id"), x.getString("title"), x.getInstant("creation_date"))
+        ));
+
+        return result;
+    }
+
+    private ResultSet executeStatement(SimpleStatement statement, String keyspace) {
+        if (keyspace != null) {
+            statement.setKeyspace(CqlIdentifier.fromCql(keyspace));
+        }
+
+        return session.execute(statement);
+    }
+}
diff --git a/twitter4j/src/test/java/com/baeldung/ApplicationIntegrationTest.java b/twitter4j/src/test/java/com/baeldung/ApplicationLiveTest.java
similarity index 95%
rename from twitter4j/src/test/java/com/baeldung/ApplicationIntegrationTest.java
rename to twitter4j/src/test/java/com/baeldung/ApplicationLiveTest.java
index 4696283faa..0d4114e72d 100644
--- a/twitter4j/src/test/java/com/baeldung/ApplicationIntegrationTest.java
+++ b/twitter4j/src/test/java/com/baeldung/ApplicationLiveTest.java
@@ -9,7 +9,7 @@ import org.junit.Test;
 
 import twitter4j.TwitterException;
 
-public class ApplicationIntegrationTest {
+public class ApplicationLiveTest {
 
 	/**
 	 * In order run this jUnit test you need to configure your API details in the twitter4j.properties