Merge pull request #1 from eugenp/master

Fork sync

.gitignore

@@ -66,3 +66,10 @@ 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/

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>

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/pom.xml

@@ -23,7 +23,7 @@
 		<dependency>
 			<groupId>com.typesafe.akka</groupId>
 			<artifactId>akka-stream_2.12</artifactId>
-			<version>2.5.11</version>
+			<version>${akka.stream.version}</version>
 		</dependency>
 		<dependency>
 			<groupId>com.typesafe.akka</groupId>
@@ -41,7 +41,6 @@
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
-		<java.version>1.8</java.version>
 		<akka.http.version>10.0.11</akka.http.version>
 		<akka.stream.version>2.5.11</akka.stream.version>
 	</properties>

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

@@ -15,3 +15,5 @@
 - [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)
 - [Java Two Pointer Technique](https://www.baeldung.com/java-two-pointer-technique)
+- [Permutations of an Array in Java](https://www.baeldung.com/java-array-permutations)
+- [Implementing Simple State Machines with Java Enums](https://www.baeldung.com/java-enum-simple-state-machine)

algorithms-miscellaneous-1/pom.xml

@@ -74,7 +74,6 @@
     </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>

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-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>

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>
@@ -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>2.9.7</jackson-databind.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <avaitility.version>1.7.0</avaitility.version>

apache-geode/pom.xml

@@ -13,22 +13,6 @@
         <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>
             <groupId>org.apache.geode</groupId>
@@ -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-meecrowave/pom.xml

@@ -7,51 +7,58 @@
     <name>apache-meecrowave</name>
     <description>A sample REST API application with Meecrowave</description>
 
-    <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>
+		<junit.version>4.10</junit.version>
+		<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-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>
@@ -54,10 +54,10 @@
     	  	<plugin>
     			<groupId>org.apache.maven.plugins</groupId>
     			<artifactId>maven-compiler-plugin</artifactId>
-    			<version>3.2</version>
+    			<version>${maven-compiler-plugin.version}</version>
     			<configuration>
-      				<source>1.8</source>
-      				<target>1.8</target>
+      				<source>${java.version}</source>
+      				<target>${java.version}</target>
     			</configuration>
   			</plugin>
       		<plugin>
@@ -85,6 +85,7 @@
         <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-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>

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/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

@@ -36,7 +36,7 @@
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-autoconfigure</artifactId>
-            <version>2.1.1.RELEASE</version>
+            <version>${spring-boot.version}</version>
             <scope>compile</scope>
         </dependency>
 

azure/pom.xml

@@ -5,9 +5,9 @@
     <groupId>com.baeldung</groupId>
     <artifactId>azure</artifactId>
     <version>0.1</version>
-    <packaging>war</packaging>
     <name>azure</name>
     <description>Demo project for Spring Boot on Azure</description>
+    <packaging>war</packaging>
 
     <parent>
         <artifactId>parent-boot-2</artifactId>
@@ -127,7 +127,6 @@
         <docker.image.prefix>${azure.containerRegistry}.azurecr.io</docker.image.prefix>
         <docker-maven-plugin.version>1.1.0</docker-maven-plugin.version>
         <azure-webapp-maven-plugin.version>1.1.0</azure-webapp-maven-plugin.version>
-        <java.version>1.8</java.version>
     </properties>
 
 </project>

blade/pom.xml

@@ -3,12 +3,12 @@
     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>blade</artifactId>
-    <name>blade</name>
-
     <!-- WITH THIS mvn integration-test DOES WORK -->
     <groupId>com.baeldung</groupId>
+    <artifactId>blade</artifactId>
     <version>1.0.0-SNAPSHOT</version>
+    <name>blade</name>
+
 
     <!-- WITH THIS mvn integration-test DOESN'T WORK -->
     <!-- <parent> -->
@@ -17,35 +17,30 @@
     <!-- <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>
         <dependency>
             <groupId>com.bladejava</groupId>
             <artifactId>blade-mvc</artifactId>
-            <version>2.0.14.RELEASE</version>
+            <version>${blade-mvc.version}</version>
         </dependency>
 
         <dependency>
             <groupId>org.webjars</groupId>
             <artifactId>bootstrap</artifactId>
-            <version>4.2.1</version>
+            <version>${bootstrap.version}</version>
         </dependency>
 
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
-            <version>3.8.1</version>
+            <version>${commons-lang3.version}</version>
         </dependency>
 
         <!-- PROVIDED -->
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
-            <version>1.18.4</version>
+            <version>${lombok.version}</version>
             <scope>provided</scope>
         </dependency>
 
@@ -53,31 +48,31 @@
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>4.12</version>
+            <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
-            <version>3.11.1</version>
+            <version>${assertj-core.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.apache.httpcomponents</groupId>
             <artifactId>httpclient</artifactId>
-            <version>4.5.6</version>
+            <version>${httpclient.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.apache.httpcomponents</groupId>
             <artifactId>httpmime</artifactId>
-            <version>4.5.6</version>
+            <version>${httpmime.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.apache.httpcomponents</groupId>
             <artifactId>httpcore</artifactId>
-            <version>4.4.10</version>
+            <version>${httpcore.version}</version>
             <scope>test</scope>
         </dependency>
     </dependencies>
@@ -88,6 +83,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
+                <version>${maven-surefire-plugin.version}</version>
                 <configuration>
                     <forkCount>3</forkCount>
                     <reuseForks>true</reuseForks>
@@ -100,7 +96,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-failsafe-plugin</artifactId>
-                <version>3.0.0-M3</version>
+                <version>${maven-failsafe-plugin.version}</version>
                 <configuration>
                     <includes>
                         <include>**/*LiveTest.java</include>
@@ -119,7 +115,7 @@
             <plugin>
                 <groupId>com.bazaarvoice.maven.plugins</groupId>
                 <artifactId>process-exec-maven-plugin</artifactId>
-                <version>0.7</version>
+                <version>${process-exec-maven-plugin.version}</version>
                 <executions>
                     <!--Start Blade -->
                     <execution>
@@ -177,13 +173,33 @@
                 </executions>
             </plugin>
             <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
                     <encoding>UTF-8</encoding>
                 </configuration>
             </plugin>
         </plugins>
     </build>
+	
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+		<blade-mvc.version>2.0.14.RELEASE</blade-mvc.version>
+		<bootstrap.version>4.2.1</bootstrap.version>
+		<commons-lang3.version>3.8.1</commons-lang3.version>
+		<lombok.version>1.18.4</lombok.version>
+		<junit.version>4.12</junit.version>
+		<httpclient.version>4.5.6</httpclient.version>
+		<httpmime.version>4.5.6</httpmime.version>
+		<httpcore.version>4.4.10</httpcore.version>
+		<assertj-core.version>3.11.1</assertj-core.version>
+		<maven-failsafe-plugin.version>3.0.0-M3</maven-failsafe-plugin.version>
+		<process-exec-maven-plugin.version>0.7</process-exec-maven-plugin.version>
+		<maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
+		<maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>
+    </properties>
 </project>

bootique/pom.xml

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

cas/cas-secured-app/pom.xml

@@ -3,9 +3,9 @@
     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>cas-secured-app</artifactId>
-    <packaging>jar</packaging>
     <name>cas-secured-app</name>
     <description>Demo project for CAS</description>
+    <packaging>jar</packaging>
 
     <parent>
         <artifactId>parent-boot-1</artifactId>

cdi/pom.xml

@@ -59,13 +59,13 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+	
     <properties>
         <cdi-api.version>2.0.SP1</cdi-api.version>
         <weld-se-core.version>3.0.5.Final</weld-se-core.version>
         <aspectjweaver.version>1.9.2</aspectjweaver.version>
         <hamcrest-core.version>1.3</hamcrest-core.version>
         <assertj-core.version>3.10.0</assertj-core.version>
-        <junit.version>4.12</junit.version>
         <spring.version>5.1.2.RELEASE</spring.version>
     </properties>
 </project>

checker-plugin/pom.xml

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

core-groovy/pom.xml

@@ -23,6 +23,12 @@
             <groupId>org.codehaus.groovy</groupId>
             <artifactId>groovy-all</artifactId>
             <version>${groovy-all.version}</version>
+            <type>pom</type>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-dateutil</artifactId>
+            <version>${groovy.version}</version>
         </dependency>
         <dependency>
             <groupId>org.codehaus.groovy</groupId>
@@ -103,9 +109,12 @@
 
     <properties>
         <junit.platform.version>1.0.0</junit.platform.version>
-        <groovy.version>2.4.13</groovy.version>
-        <groovy-all.version>2.4.13</groovy-all.version>
-        <groovy-sql.version>2.4.13</groovy-sql.version>
+<!--         <groovy.version>2.4.13</groovy.version> -->
+<!--         <groovy-all.version>2.4.13</groovy-all.version> -->
+<!--         <groovy-sql.version>2.4.13</groovy-sql.version> -->
+        <groovy.version>2.5.6</groovy.version>
+        <groovy-all.version>2.5.6</groovy-all.version>
+        <groovy-sql.version>2.5.6</groovy-sql.version>
         <hsqldb.version>2.4.0</hsqldb.version>
         <spock-core.version>1.1-groovy-2.4</spock-core.version>
         <gmavenplus-plugin.version>1.6</gmavenplus-plugin.version>

core-groovy/src/main/groovy/com/baeldung/file/ReadFile.groovy

@@ -0,0 +1,107 @@
+package com.baeldung.file
+
+class ReadFile {
+
+    /**
+     * reads file content line by line using withReader and reader.readLine
+     * @param filePath
+     * @return
+     */
+    int readFileLineByLine(String filePath) {
+        File file = new File(filePath)
+        def line, noOfLines = 0;
+        file.withReader { reader ->
+            while ((line = reader.readLine())!=null)
+            {
+                println "${line}"
+                noOfLines++
+            }
+        }
+        return noOfLines
+    }
+
+    /**
+     * reads file content in list of lines
+     * @param filePath
+     * @return
+     */
+    List<String> readFileInList(String filePath) {
+        File file = new File(filePath)
+        def lines = file.readLines()
+        return lines
+    }
+
+    /**
+     * reads file content in string using File.text
+     * @param filePath
+     * @return
+     */
+    String readFileString(String filePath) {
+        File file = new File(filePath)
+        String fileContent = file.text
+        return fileContent
+    }
+
+    /**
+     * reads file content in string with encoding using File.getText
+     * @param filePath
+     * @return
+     */
+    String readFileStringWithCharset(String filePath) {
+        File file = new File(filePath)
+        String utf8Content = file.getText("UTF-8")
+        return utf8Content
+    }
+
+    /**
+     * reads content of binary file and returns byte array
+     * @param filePath
+     * @return
+     */
+    byte[] readBinaryFile(String filePath) {
+        File file = new File(filePath)
+        byte[] binaryContent = file.bytes
+        return binaryContent
+    }
+    
+    /**
+     * More Examples of reading a file 
+     * @return
+     */
+    def moreExamples() {
+        
+        //with reader with utf-8
+        new File("src/main/resources/utf8Content.html").withReader('UTF-8') { reader ->
+            def line
+            while ((line = reader.readLine())!=null) { 
+                println "${line}"
+            }
+        }
+        
+        //collect api
+        def list = new File("src/main/resources/fileContent.txt").collect {it}
+                
+        //as operator
+        def array = new File("src/main/resources/fileContent.txt") as String[]
+              
+        //eachline  
+        new File("src/main/resources/fileContent.txt").eachLine { line ->
+            println line
+        }
+        
+        //newInputStream with eachLine
+        def is = new File("src/main/resources/fileContent.txt").newInputStream()
+        is.eachLine {
+            println it
+        }
+        is.close()
+        
+        //withInputStream
+        new File("src/main/resources/fileContent.txt").withInputStream { stream ->
+            stream.eachLine { line ->
+                println line
+            }
+        }
+    }
+
+}

core-groovy/src/main/groovy/com/baeldung/strings/Concatenate.groovy

@@ -0,0 +1,43 @@
+package com.baeldung.strings;
+
+class Concatenate {
+    String first = 'Hello'
+    String last = 'Groovy'
+  
+    String doSimpleConcat() {
+        return 'My name is ' + first + ' ' + last
+    }
+
+    String doConcatUsingGString() {
+        return "My name is $first $last"
+    }
+
+    String doConcatUsingGStringClosures() {
+        return "My name is ${-> first} ${-> last}"
+    }
+
+    String doConcatUsingStringConcatMethod() {
+        return 'My name is '.concat(first).concat(' ').concat(last)
+    }
+
+    String doConcatUsingLeftShiftOperator() {
+        return 'My name is ' << first << ' ' << last
+    }
+    
+    String doConcatUsingArrayJoinMethod() {
+        return ['My name is', first, last].join(' ')
+    }
+
+    String doConcatUsingArrayInjectMethod() {
+        return  [first,' ', last]
+          .inject(new StringBuffer('My name is '), { initial, name -> initial.append(name); return initial }).toString()
+    }
+ 
+    String doConcatUsingStringBuilder() {
+        return new StringBuilder().append('My name is ').append(first).append(' ').append(last)
+    }
+
+    String doConcatUsingStringBuffer() {
+        return new StringBuffer().append('My name is ').append(first).append(' ').append(last)
+    }
+}

core-groovy/src/main/groovy/com/baeldung/traits/AnimalTrait.groovy

@@ -0,0 +1,8 @@
+package com.baeldung.traits
+
+trait AnimalTrait {
+    
+    String basicBehavior() {
+        return "Animalistic!!"
+    }
+}

core-groovy/src/main/groovy/com/baeldung/traits/Car.groovy

@@ -0,0 +1,3 @@
+package com.baeldung
+
+class Car implements VehicleTrait {}

core-groovy/src/main/groovy/com/baeldung/traits/Dog.groovy

@@ -0,0 +1,9 @@
+package com.baeldung.traits
+
+class Dog implements WalkingTrait, SpeakingTrait {
+     
+    String speakAndWalk() {
+        WalkingTrait.super.speakAndWalk()
+    }
+    
+}

core-groovy/src/main/groovy/com/baeldung/traits/Employee.groovy

@@ -0,0 +1,12 @@
+package com.baeldung.traits
+
+class Employee implements UserTrait {
+    
+    String name() {
+        return 'Bob'
+    }
+    
+    String lastName() {
+        return "Marley"
+    }
+}

core-groovy/src/main/groovy/com/baeldung/traits/Human.groovy

@@ -0,0 +1,6 @@
+package com.baeldung.traits
+
+interface Human {
+    
+    String lastName()
+}

core-groovy/src/main/groovy/com/baeldung/traits/SpeakingTrait.groovy

@@ -0,0 +1,13 @@
+package com.baeldung.traits
+
+trait SpeakingTrait {
+    
+    String basicAbility() {
+        return "Speaking!!"
+    }
+    
+    String speakAndWalk() {
+        return "Speak and walk!!"
+    }
+    
+}

core-groovy/src/main/groovy/com/baeldung/traits/UserTrait.groovy

@@ -0,0 +1,36 @@
+package com.baeldung.traits
+
+trait UserTrait implements Human {
+    
+    String sayHello() {
+        return "Hello!"
+    }
+    
+    abstract String name()
+    
+    String showName() {
+       return "Hello, ${name()}!"
+    }
+
+    private String greetingMessage() {
+        return 'Hello, from a private method!'
+    }
+    
+    String greet() {
+        def msg = greetingMessage()
+        println msg
+        msg
+    }
+    
+    def self() {
+        return this 
+    }
+    
+    String showLastName() {
+        return "Hello, ${lastName()}!"
+    }
+    
+    String email
+    String address
+}
+    

core-groovy/src/main/groovy/com/baeldung/traits/VehicleTrait.groovy

@@ -0,0 +1,9 @@
+package com.baeldung
+
+trait VehicleTrait extends WheelTrait {
+    
+    String showWheels() {
+        return "Num of Wheels $noOfWheels" 
+    }
+    
+}

core-groovy/src/main/groovy/com/baeldung/traits/WalkingTrait.groovy

@@ -0,0 +1,13 @@
+package com.baeldung.traits
+
+trait WalkingTrait {
+    
+    String basicAbility() {
+        return "Walking!!"
+    }
+    
+    String speakAndWalk() {
+        return "Walk and speak!!"
+    }
+    
+}

core-groovy/src/main/groovy/com/baeldung/traits/WheelTrait.groovy

@@ -0,0 +1,7 @@
+package com.baeldung
+
+trait WheelTrait {
+    
+    int noOfWheels
+    
+}

core-groovy/src/main/resources/fileContent.txt

@@ -0,0 +1,3 @@
+Line 1 : Hello World!!!
+Line 2 : This is a file content.
+Line 3 : String content

core-groovy/src/main/resources/utf8Content.html

@@ -0,0 +1,12 @@
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml">
+<meta charset="UTF-8">
+<body>
+<pre>
+ᚠᛇᚻ᛫ᛒᛦᚦ᛫ᚠᚱᚩᚠᚢᚱ᛫ᚠᛁᚱᚪ᛫ᚷᛖᚻᚹᛦᛚᚳᚢᛗ
+ᛋᚳᛖᚪᛚ᛫ᚦᛖᚪᚻ᛫ᛗᚪᚾᚾᚪ᛫ᚷᛖᚻᚹᛦᛚᚳ᛫ᛗᛁᚳᛚᚢᚾ᛫ᚻᛦᛏ᛫ᛞᚫᛚᚪᚾ
+ᚷᛁᚠ᛫ᚻᛖ᛫ᚹᛁᛚᛖ᛫ᚠᚩᚱ᛫ᛞᚱᛁᚻᛏᚾᛖ᛫ᛞᚩᛗᛖᛋ᛫ᚻᛚᛇᛏᚪᚾ
+</pre>
+</body>
+</html>

core-groovy/src/test/groovy/com/baeldung/date/DateTest.groovy

@@ -0,0 +1,57 @@
+package com.baeldung.groovy.sql
+
+import static org.junit.Assert.*
+import java.util.Calendar.*
+import java.time.LocalDate 
+import java.text.SimpleDateFormat 
+import org.junit.Test
+
+
+class DateTest {
+
+    def dateStr = "2019-02-28"
+    def pattern = "yyyy-MM-dd"  
+
+    @Test
+    void whenGetStringRepresentation_thenCorrectlyConvertIntoDate() {
+        def dateFormat = new SimpleDateFormat(pattern)
+        def date = dateFormat.parse(dateStr)
+                
+        println("       String to Date with DateFormatter : " + date)
+
+        def cal = new GregorianCalendar();
+        cal.setTime(date);
+
+        assertEquals(cal.get(Calendar.YEAR),2019)
+        assertEquals(cal.get(Calendar.DAY_OF_MONTH),28)
+        assertEquals(cal.get(Calendar.MONTH),java.util.Calendar.FEBRUARY)
+    }
+
+    @Test
+    void whenGetStringRepresentation_thenCorrectlyConvertWithDateUtilsExtension() {
+    
+        def date = Date.parse(pattern, dateStr)
+                
+        println("       String to Date with Date.parse : " + date)
+    
+        def cal = new GregorianCalendar();
+        cal.setTime(date);
+
+        assertEquals(cal.get(Calendar.YEAR),2019)
+        assertEquals(cal.get(Calendar.DAY_OF_MONTH),28)
+        assertEquals(cal.get(Calendar.MONTH),java.util.Calendar.FEBRUARY)
+    }    
+
+    @Test
+    void whenGetStringRepresentation_thenCorrectlyConvertIntoDateWithLocalDate() {
+        def date = LocalDate.parse(dateStr, pattern)
+
+        println("       String to Date with LocalDate     : " + date)
+
+        assertEquals(date.getYear(),2019)
+        assertEquals(date.getMonth(),java.time.Month.FEBRUARY)
+        assertEquals(date.getDayOfMonth(),28)
+    }
+
+
+}

core-groovy/src/test/groovy/com/baeldung/file/ReadFileUnitTest.groovy

@@ -0,0 +1,70 @@
+package com.baeldung.file
+
+import spock.lang.Specification
+
+class ReadFileUnitTest extends Specification {
+
+    ReadFile readFile
+
+    void setup () {
+        readFile = new ReadFile()
+    }
+
+    def 'Should return number of lines in File using ReadFile.readFileLineByLine given filePath' () {
+        given:
+            def filePath = "src/main/resources/fileContent.txt"
+        when:
+            def noOfLines = readFile.readFileLineByLine(filePath)
+        then:
+            noOfLines
+            noOfLines instanceof Integer
+            assert noOfLines, 3
+    }
+    
+    def 'Should return File Content in list of lines using ReadFile.readFileInList given filePath' () {
+        given:
+            def filePath = "src/main/resources/fileContent.txt"
+        when:
+            def lines = readFile.readFileInList(filePath)
+        then:
+            lines
+            lines instanceof List<String>
+            assert lines.size(), 3
+    }
+    
+    def 'Should return file content in string using ReadFile.readFileString given filePath' () {
+        given:
+            def filePath = "src/main/resources/fileContent.txt"
+        when:
+            def fileContent = readFile.readFileString(filePath)
+        then:
+            fileContent
+            fileContent instanceof String
+            fileContent.contains("""Line 1 : Hello World!!!
+Line 2 : This is a file content.
+Line 3 : String content""")
+    
+    }
+
+    def 'Should return UTF-8 encoded file content in string using ReadFile.readFileStringWithCharset given filePath' () {
+        given:
+            def filePath = "src/main/resources/utf8Content.html"
+        when:
+            def encodedContent = readFile.readFileStringWithCharset(filePath)
+        then:
+            encodedContent
+            encodedContent instanceof String
+    }
+    
+    def 'Should return binary file content in byte array using ReadFile.readBinaryFile given filePath' () {
+        given:
+            def filePath = "src/main/resources/sample.png"
+        when:
+            def binaryContent = readFile.readBinaryFile(filePath)
+        then:
+            binaryContent
+            binaryContent instanceof byte[]
+            binaryContent.length == 329
+    }
+    
+}

core-groovy/src/test/groovy/com/baeldung/map/MapUnitTest.groovy

@@ -0,0 +1,85 @@
+package com.baeldung.map
+
+import static org.junit.Assert.*
+import org.junit.Test
+
+class MapUnitTest {
+
+    @Test
+    void whenUsingEach_thenMapIsIterated() {
+        def map = [
+            'FF0000' : 'Red',
+            '00FF00' : 'Lime',
+            '0000FF' : 'Blue',
+            'FFFF00' : 'Yellow'
+        ]
+
+        map.each { println "Hex Code: $it.key = Color Name: $it.value" }
+    }
+
+    @Test
+    void whenUsingEachWithEntry_thenMapIsIterated() {
+        def map = [
+            'E6E6FA' : 'Lavender',
+            'D8BFD8' : 'Thistle',
+            'DDA0DD' : 'Plum',
+        ]
+
+        map.each { entry -> println "Hex Code: $entry.key = Color Name: $entry.value" }
+    }
+
+    @Test
+    void whenUsingEachWithKeyAndValue_thenMapIsIterated() {
+        def map = [
+            '000000' : 'Black',
+            'FFFFFF' : 'White',
+            '808080' : 'Gray'
+        ]
+
+        map.each { key, val ->
+            println "Hex Code: $key = Color Name $val"
+        }
+    }
+
+    @Test
+    void whenUsingEachWithIndexAndEntry_thenMapIsIterated() {
+        def map = [
+            '800080' : 'Purple',
+            '4B0082' : 'Indigo',
+            '6A5ACD' : 'Slate Blue'
+        ]
+
+        map.eachWithIndex { entry, index ->
+            def indent = ((index == 0 || index % 2 == 0) ? "   " : "")
+            println "$indent Hex Code: $entry.key = Color Name: $entry.value"
+        }
+    }
+
+    @Test
+    void whenUsingEachWithIndexAndKeyAndValue_thenMapIsIterated() {
+        def map = [
+            'FFA07A' : 'Light Salmon',
+            'FF7F50' : 'Coral',
+            'FF6347' : 'Tomato',
+            'FF4500' : 'Orange Red'
+        ]
+        
+        map.eachWithIndex { key, val, index ->
+            def indent = ((index == 0 || index % 2 == 0) ? "   " : "")
+            println "$indent Hex Code: $key = Color Name: $val"
+        }
+    }
+
+    @Test
+    void whenUsingForLoop_thenMapIsIterated() {
+        def map = [
+            '2E8B57' : 'Seagreen',
+            '228B22' : 'Forest Green',
+            '008000' : 'Green'
+        ]
+
+        for (entry in map) {
+            println "Hex Code: $entry.key = Color Name: $entry.value"
+        }
+    }
+}

core-groovy/src/test/groovy/com/baeldung/strings/ConcatenateTest.groovy

@@ -0,0 +1,101 @@
+import com.baeldung.strings.Concatenate;
+
+class ConcatenateTest extends GroovyTestCase {
+    
+    void testSimpleConcat() {
+        def name = new Concatenate()
+        name.first = 'Joe';
+        name.last = 'Smith';
+        def expected = 'My name is Joe Smith'
+        assertToString(name.doSimpleConcat(), expected)
+    }
+    
+    void testConcatUsingGString() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingGString(), expected)
+    }
+    
+    void testConcatUsingGStringClosures() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingGStringClosures(), expected)
+    }
+    
+    void testConcatUsingStringConcatMethod() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingStringConcatMethod(), expected)
+    }
+
+    void testConcatUsingLeftShiftOperator() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingLeftShiftOperator(), expected)
+    }
+
+    void testConcatUsingArrayJoinMethod() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingArrayJoinMethod(), expected)
+    }
+
+    void testConcatUsingArrayInjectMethod() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingArrayInjectMethod(), expected)
+    }
+
+    void testConcatUsingStringBuilder() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingStringBuilder(), expected)
+    }
+
+    void testConcatUsingStringBuffer() {
+        def name = new Concatenate()
+        name.first = "Joe";
+        name.last = "Smith";
+        def expected = "My name is Joe Smith"
+        assertToString(name.doConcatUsingStringBuffer(), expected)
+    }
+
+    void testConcatMultilineUsingStringConcatMethod() {
+        def name = new Concatenate()
+        name.first = '''Joe
+                        Smith
+                        ''';
+        name.last = 'Junior';
+        def expected = '''My name is Joe
+                        Smith
+                         Junior''';
+        assertToString(name.doConcatUsingStringConcatMethod(), expected)
+    }
+
+    void testGStringvsClosure(){
+        def first = "Joe";
+        def last = "Smith";
+        def eagerGString = "My name is $first $last"
+        def lazyGString = "My name is ${-> first} ${-> last}"
+
+        assert eagerGString == "My name is Joe Smith"
+        assert lazyGString == "My name is Joe Smith"
+        first = "David";
+        assert eagerGString == "My name is Joe Smith"
+        assert lazyGString == "My name is David Smith"
+    }  
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/CharacterInGroovy.groovy

@@ -0,0 +1,19 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Assert
+import org.junit.Test
+
+class CharacterInGroovy {
+
+    @Test
+    void 'character'() {
+        char a = 'A' as char
+        char b = 'B' as char
+        char c = (char) 'C'
+
+        Assert.assertTrue(a instanceof Character)
+        Assert.assertTrue(b instanceof Character)
+        Assert.assertTrue(c instanceof Character)
+    }
+
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/DollarSlashyString.groovy

@@ -0,0 +1,24 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Test
+
+class DollarSlashyString {
+
+    @Test
+    void 'dollar slashy string'() {
+        def name = "John"
+
+        def dollarSlashy = $/
+            Hello $name!,
+
+            I can show you $ sign or escaped dollar sign: $$ 
+            Both slashes works: \ or /, but we can still escape it: $/
+            
+            We have to escape opening and closing delimiter:
+            - $$$/  
+            - $/$$
+        /$
+
+        print(dollarSlashy)
+    }
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/DoubleQuotedString.groovy

@@ -0,0 +1,67 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Assert
+import org.junit.Test
+
+class DoubleQuotedString {
+
+    @Test
+    void 'escape double quoted string'() {
+        def example = "Hello \"world\"!"
+
+        println(example)
+    }
+
+    @Test
+    void 'String ang GString'() {
+        def string = "example"
+        def stringWithExpression = "example${2}"
+
+        Assert.assertTrue(string instanceof String)
+        Assert.assertTrue(stringWithExpression instanceof GString)
+        Assert.assertTrue(stringWithExpression.toString() instanceof String)
+    }
+
+    @Test
+    void 'placeholder with variable'() {
+        def name = "John"
+        def helloName = "Hello $name!".toString()
+
+        Assert.assertEquals("Hello John!", helloName)
+    }
+
+    @Test
+    void 'placeholder with expression'() {
+        def result = "result is ${2 * 2}".toString()
+
+        Assert.assertEquals("result is 4", result)
+    }
+
+    @Test
+    void 'placeholder with dotted access'() {
+        def person = [name: 'John']
+
+        def myNameIs = "I'm $person.name, and you?".toString()
+
+        Assert.assertEquals("I'm John, and you?", myNameIs)
+    }
+
+    @Test
+    void 'placeholder with method call'() {
+        def name = 'John'
+
+        def result = "Uppercase name: ${name.toUpperCase()}".toString()
+
+        Assert.assertEquals("Uppercase name: JOHN", result)
+    }
+
+
+    @Test
+    void 'GString and String hashcode'() {
+        def string = "2+2 is 4"
+        def gstring = "2+2 is ${4}"
+
+        Assert.assertTrue(string.hashCode() != gstring.hashCode())
+    }
+
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/SingleQuotedString.groovy

@@ -0,0 +1,15 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Assert
+import org.junit.Test
+
+class SingleQuotedString {
+
+    @Test
+    void 'single quoted string'() {
+        def example = 'Hello world'
+
+        Assert.assertEquals('Hello world!', 'Hello' + ' world!')
+    }
+
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/SlashyString.groovy

@@ -0,0 +1,31 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Assert
+import org.junit.Test
+
+class SlashyString {
+
+    @Test
+    void 'slashy string'() {
+        def pattern = /.*foobar.*\/hello.*/
+
+        Assert.assertTrue("I'm matching foobar /hello regexp pattern".matches(pattern))
+    }
+
+    void 'wont compile'() {
+//        if ('' == //) {
+//            println("I can't compile")
+//        }
+    }
+
+    @Test
+    void 'interpolate and multiline'() {
+        def name = 'John'
+
+        def example = /
+            Hello $name
+            second line        
+        /
+    }
+
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/Strings.groovy

@@ -0,0 +1,26 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Assert
+import org.junit.Test
+
+class Strings {
+
+    @Test
+    void 'string interpolation '() {
+        def name = "Kacper"
+
+        def result = "Hello ${name}!"
+
+        Assert.assertEquals("Hello Kacper!", result.toString())
+    }
+
+    @Test
+    void 'string concatenation'() {
+        def first = "first"
+        def second = "second"
+
+        def concatenation = first + second
+
+        Assert.assertEquals("firstsecond", concatenation)
+    }
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/TripleDoubleQuotedString.groovy

@@ -0,0 +1,19 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Test
+
+class TripleDoubleQuotedString {
+
+    @Test
+    void 'triple-quoted strings with interpolation'() {
+        def name = "John"
+
+        def multiLine = """
+            I'm $name.
+            "This is quotation"
+        """
+
+        println(multiLine)
+    }
+
+}

core-groovy/src/test/groovy/com/baeldung/stringtypes/TripleSingleQuotedString.groovy

@@ -0,0 +1,67 @@
+package groovy.com.baeldung.stringtypes
+
+import org.junit.Assert
+import org.junit.Test
+
+class TripleSingleQuotedString {
+
+    def 'formatted json'() {
+        def jsonContent = '''
+        {
+            "name": "John",
+            "age": 20,
+            "birthDate": null
+        }
+        '''
+    }
+
+    def 'triple single quoted'() {
+        def triple = '''im triple single quoted string'''
+    }
+
+    @Test
+    void 'triple single quoted with multiline string'() {
+        def triple = '''
+            firstline
+            secondline
+        '''
+
+        Assert.assertTrue(triple.startsWith("\n"))
+    }
+
+    @Test
+    void 'triple single quoted with multiline string with stripIndent() and removing newline characters'() {
+        def triple = '''\
+            firstline
+            secondline'''.stripIndent()
+
+        Assert.assertEquals("firstline\nsecondline", triple)
+    }
+
+    @Test
+    void 'triple single quoted with multiline string with last line with only whitespaces'() {
+        def triple = '''\
+            firstline
+                secondline\
+        '''.stripIndent()
+
+        println(triple)
+    }
+
+    @Test
+    void 'triple single quoted with multiline string with stripMargin(Character) and removing newline characters'() {
+        def triple = '''\
+            |firstline
+            |secondline'''.stripMargin()
+
+        println(triple)
+    }
+
+    @Test
+    void 'striple single quoted with special characters'() {
+        def specialCharacters = '''hello \'John\'. This is backslash - \\. \nSecond line starts here'''
+
+        println(specialCharacters)
+    }
+
+}

core-groovy/src/test/groovy/com/baeldung/traits/TraitsUnitTest.groovy

@@ -0,0 +1,114 @@
+package com.baeldung.traits
+
+import spock.lang.Specification
+
+class TraitsUnitTest extends Specification {
+
+    Employee employee
+    Dog dog
+
+    void setup () {
+        employee = new Employee()
+        dog = new Dog()
+    }
+
+    def 'Should return msg string when using Employee.sayHello method provided by UserTrait' () {
+        when:
+            def msg = employee.sayHello()
+        then:
+            msg
+            msg instanceof String
+            assert msg == "Hello!"
+    }
+    
+    def 'Should return displayMsg string when using Employee.showName method' () {
+        when:
+            def displayMsg = employee.showName()
+        then:
+            displayMsg
+            displayMsg instanceof String
+            assert displayMsg == "Hello, Bob!"
+    }
+    
+    def 'Should return greetMsg string when using Employee.greet method' () {
+        when:
+            def greetMsg = employee.greet()
+        then:
+            greetMsg
+            greetMsg instanceof String
+            assert greetMsg == "Hello, from a private method!"
+    }
+    
+    def 'Should return MissingMethodException when using Employee.greetingMessage method' () {
+        when:
+            def exception
+            try {
+                employee.greetingMessage()
+            }catch(Exception e) {
+                exception = e
+            }
+            
+        then:
+            exception
+            exception instanceof groovy.lang.MissingMethodException
+            assert exception.message == "No signature of method: com.baeldung.traits.Employee.greetingMessage()"+
+            " is applicable for argument types: () values: []"
+    }
+    
+    def 'Should return employee instance when using Employee.whoAmI method' () {
+        when:
+            def emp = employee.self()
+        then:
+            emp
+            emp instanceof Employee
+            assert emp.is(employee)
+    }
+    
+    def 'Should display lastName when using Employee.showLastName method' () {
+        when:
+            def lastNameMsg = employee.showLastName()
+        then:
+            lastNameMsg
+            lastNameMsg instanceof String
+            assert lastNameMsg == "Hello, Marley!"
+    }
+    
+    def 'Should be able to define properties of UserTrait in Employee instance' () {
+        when:
+            employee = new Employee(email: "a@e.com", address: "baeldung.com")
+        then:
+            employee
+            employee instanceof Employee
+            assert employee.email == "a@e.com"
+            assert employee.address == "baeldung.com"
+    }
+    
+    def 'Should execute basicAbility method from SpeakingTrait and return msg string' () {
+        when:
+            def speakMsg = dog.basicAbility()
+        then:
+            speakMsg
+            speakMsg instanceof String
+            assert speakMsg == "Speaking!!"
+    }
+    
+    def 'Should verify multiple inheritance with traits and execute overridden traits method' () {
+        when:
+            def walkSpeakMsg = dog.speakAndWalk()
+            println walkSpeakMsg
+        then:
+            walkSpeakMsg
+            walkSpeakMsg instanceof String
+            assert walkSpeakMsg == "Walk and speak!!"
+    }
+    
+    def 'Should implement AnimalTrait at runtime and access basicBehavior method' () {
+        when:
+            def dogInstance = new Dog() as AnimalTrait
+            def basicBehaviorMsg = dogInstance.basicBehavior()
+        then:
+            basicBehaviorMsg
+            basicBehaviorMsg instanceof String
+            assert basicBehaviorMsg == "Animalistic!!"
+    }
+}

core-java-10/pom.xml

@@ -3,9 +3,9 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.baeldung</groupId>
     <artifactId>core-java-10</artifactId>
-    <packaging>jar</packaging>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-10</name>
+    <packaging>jar</packaging>
     <url>http://maven.apache.org</url>
 
     <parent>

core-java-11/README.md

@@ -3,3 +3,4 @@
 - [Java 11 Single File Source Code](https://www.baeldung.com/java-single-file-source-code)
 - [Java 11 Local Variable Syntax for Lambda Parameters](https://www.baeldung.com/java-var-lambda-params)
 - [Java 11 String API Additions](https://www.baeldung.com/java-11-string-api)
+- [Java 11 Nest Based Access Control](https://www.baeldung.com/java-nest-based-access-control)

core-java-11/pom.xml

@@ -3,9 +3,9 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.baeldung</groupId>
     <artifactId>core-java-11</artifactId>
-    <packaging>jar</packaging>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-11</name>
+    <packaging>jar</packaging>
     <url>http://maven.apache.org</url>
 
     <parent>

core-java-11/src/main/java/com/baeldung/epsilongc/MemoryPolluter.java

@@ -0,0 +1,18 @@
+package com.baeldung.epsilongc;
+
+public class MemoryPolluter {
+
+    private static final int MEGABYTE_IN_BYTES = 1024 * 1024;
+    private static final int ITERATION_COUNT = 1024 * 10;
+
+    public static void main(String[] args) {
+        System.out.println("Starting pollution");
+
+        for (int i = 0; i < ITERATION_COUNT; i++) {
+            byte[] array = new byte[MEGABYTE_IN_BYTES];
+        }
+
+        System.out.println("Terminating");
+    }
+
+}

core-java-11/src/main/java/com/baeldung/java11/httpclient/HttpClientExample.java

@@ -0,0 +1,132 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package com.baeldung.java11.httpclient;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpClient.Version;
+import java.net.http.HttpRequest;
+import java.net.http.HttpRequest.BodyPublishers;
+import java.net.http.HttpResponse;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.net.http.HttpResponse.PushPromiseHandler;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class HttpClientExample {
+
+    public static void main(String[] args) throws Exception {
+        httpGetRequest();
+        httpPostRequest();
+        asynchronousGetRequest();
+        asynchronousMultipleRequests();
+        pushRequest();
+    }
+
+    public static void httpGetRequest() throws URISyntaxException, IOException, InterruptedException {
+        HttpClient client = HttpClient.newHttpClient();
+        HttpRequest request = HttpRequest.newBuilder()
+            .version(HttpClient.Version.HTTP_2)
+            .uri(URI.create("http://jsonplaceholder.typicode.com/posts/1"))
+            .headers("Accept-Enconding", "gzip, deflate")
+            .build();
+        HttpResponse<String> response = client.send(request, BodyHandlers.ofString());
+
+        String responseBody = response.body();
+        int responseStatusCode = response.statusCode();
+
+        System.out.println("httpGetRequest: " + responseBody);
+        System.out.println("httpGetRequest status code: " + responseStatusCode);
+    }
+
+    public static void httpPostRequest() throws URISyntaxException, IOException, InterruptedException {
+        HttpClient client = HttpClient.newBuilder()
+            .version(HttpClient.Version.HTTP_2)
+            .build();
+        HttpRequest request = HttpRequest.newBuilder(new URI("http://jsonplaceholder.typicode.com/posts"))
+            .version(HttpClient.Version.HTTP_2)
+            .POST(BodyPublishers.ofString("Sample Post Request"))
+            .build();
+        HttpResponse<String> response = client.send(request, BodyHandlers.ofString());
+        String responseBody = response.body();
+        System.out.println("httpPostRequest : " + responseBody);
+    }
+
+    public static void asynchronousGetRequest() throws URISyntaxException {
+        HttpClient client = HttpClient.newHttpClient();
+        URI httpURI = new URI("http://jsonplaceholder.typicode.com/posts/1");
+        HttpRequest request = HttpRequest.newBuilder(httpURI)
+            .version(HttpClient.Version.HTTP_2)
+            .build();
+        CompletableFuture<Void> futureResponse = client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
+            .thenAccept(resp -> {
+                System.out.println("Got pushed response " + resp.uri());
+                System.out.println("Response statuscode: " + resp.statusCode());
+                System.out.println("Response body: " + resp.body());
+            });
+        System.out.println("futureResponse" + futureResponse);
+
+    }
+
+    public static void asynchronousMultipleRequests() throws URISyntaxException {
+        HttpClient client = HttpClient.newHttpClient();
+        List<URI> uris = Arrays.asList(new URI("http://jsonplaceholder.typicode.com/posts/1"), new URI("http://jsonplaceholder.typicode.com/posts/2"));
+        List<HttpRequest> requests = uris.stream()
+            .map(HttpRequest::newBuilder)
+            .map(reqBuilder -> reqBuilder.build())
+            .collect(Collectors.toList());
+        System.out.println("Got pushed response1 " + requests);
+        CompletableFuture.allOf(requests.stream()
+            .map(request -> client.sendAsync(request, BodyHandlers.ofString()))
+            .toArray(CompletableFuture<?>[]::new))
+            .thenAccept(System.out::println)
+            .join();
+    }
+
+    public static void pushRequest() throws URISyntaxException, InterruptedException {
+        System.out.println("Running HTTP/2 Server Push example...");
+
+        HttpClient httpClient = HttpClient.newBuilder()
+            .version(Version.HTTP_2)
+            .build();
+
+        HttpRequest pageRequest = HttpRequest.newBuilder()
+            .uri(URI.create("https://http2.golang.org/serverpush"))
+            .build();
+
+        // Interface HttpResponse.PushPromiseHandler<T>
+        // void applyPushPromise​(HttpRequest initiatingRequest, HttpRequest pushPromiseRequest, Function<HttpResponse.BodyHandler<T>,​CompletableFuture<HttpResponse<T>>> acceptor)
+        httpClient.sendAsync(pageRequest, BodyHandlers.ofString(), pushPromiseHandler())
+            .thenAccept(pageResponse -> {
+                System.out.println("Page response status code: " + pageResponse.statusCode());
+                System.out.println("Page response headers: " + pageResponse.headers());
+                String responseBody = pageResponse.body();
+                System.out.println(responseBody);
+            }).join();
+
+        Thread.sleep(1000); // waiting for full response
+    }
+
+    private static PushPromiseHandler<String> pushPromiseHandler() {
+        return (HttpRequest initiatingRequest, 
+            HttpRequest pushPromiseRequest, 
+            Function<HttpResponse.BodyHandler<String>, 
+            CompletableFuture<HttpResponse<String>>> acceptor) -> {
+            acceptor.apply(BodyHandlers.ofString())
+                .thenAccept(resp -> {
+                    System.out.println(" Pushed response: " + resp.uri() + ", headers: " + resp.headers());
+                });
+            System.out.println("Promise request: " + pushPromiseRequest.uri());
+            System.out.println("Promise request: " + pushPromiseRequest.headers());
+        };
+    }
+
+}

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

@@ -0,0 +1,240 @@
+package com.baeldung.java11.httpclient.test;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+import java.io.IOException;
+import java.net.Authenticator;
+import java.net.CookieManager;
+import java.net.CookiePolicy;
+import java.net.HttpURLConnection;
+import java.net.PasswordAuthentication;
+import java.net.ProxySelector;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+
+public class HttpClientTest {
+
+    @Test
+    public void shouldReturnSampleDataContentWhenConnectViaSystemProxy() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/post"))
+            .headers("Content-Type", "text/plain;charset=UTF-8")
+            .POST(HttpRequest.BodyPublishers.ofString("Sample body"))
+            .build();
+      
+        
+        HttpResponse<String> response = HttpClient.newBuilder()
+            .proxy(ProxySelector.getDefault())
+            .build()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+        
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response.body(), containsString("Sample body"));
+    }
+
+    @Test
+    public void shouldNotFollowRedirectWhenSetToDefaultNever() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("http://stackoverflow.com"))
+            .version(HttpClient.Version.HTTP_1_1)
+            .GET()
+            .build();
+        HttpResponse<String> response = HttpClient.newBuilder()
+            .build()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_MOVED_PERM));
+        assertThat(response.body(), containsString("https://stackoverflow.com/"));
+    }
+
+    @Test
+    public void shouldFollowRedirectWhenSetToAlways() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("http://stackoverflow.com"))
+            .version(HttpClient.Version.HTTP_1_1)
+            .GET()
+            .build();
+        HttpResponse<String> response = HttpClient.newBuilder()
+            .followRedirects(HttpClient.Redirect.ALWAYS)
+            .build()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response.request()
+            .uri()
+            .toString(), equalTo("https://stackoverflow.com/"));
+    }
+
+    @Test
+    public void shouldReturnOKStatusForAuthenticatedAccess() throws URISyntaxException, IOException, InterruptedException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/basic-auth"))
+            .GET()
+            .build();
+        HttpResponse<String> response = HttpClient.newBuilder()
+            .authenticator(new Authenticator() {
+                @Override
+                protected PasswordAuthentication getPasswordAuthentication() {
+                    return new PasswordAuthentication("postman", "password".toCharArray());
+                }
+            })
+            .build()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+    }
+
+    @Test
+    public void shouldSendRequestAsync() throws URISyntaxException, InterruptedException, ExecutionException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/post"))
+            .headers("Content-Type", "text/plain;charset=UTF-8")
+            .POST(HttpRequest.BodyPublishers.ofString("Sample body"))
+            .build();
+        CompletableFuture<HttpResponse<String>> response = HttpClient.newBuilder()
+            .build()
+            .sendAsync(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.get()
+            .statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+    }
+
+    @Test
+    public void shouldUseJustTwoThreadWhenProcessingSendAsyncRequest() throws URISyntaxException, InterruptedException, ExecutionException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .GET()
+            .build();
+
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+
+        CompletableFuture<HttpResponse<String>> response1 = HttpClient.newBuilder()
+            .executor(executorService)
+            .build()
+            .sendAsync(request, HttpResponse.BodyHandlers.ofString());
+
+        CompletableFuture<HttpResponse<String>> response2 = HttpClient.newBuilder()
+            .executor(executorService)
+            .build()
+            .sendAsync(request, HttpResponse.BodyHandlers.ofString());
+
+        CompletableFuture<HttpResponse<String>> response3 = HttpClient.newBuilder()
+            .executor(executorService)
+            .build()
+            .sendAsync(request, HttpResponse.BodyHandlers.ofString());
+
+        CompletableFuture.allOf(response1, response2, response3)
+            .join();
+
+        assertThat(response1.get()
+            .statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response2.get()
+            .statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response3.get()
+            .statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+    }
+
+    @Test
+    public void shouldNotStoreCookieWhenPolicyAcceptNone() throws URISyntaxException, IOException, InterruptedException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .GET()
+            .build();
+
+        HttpClient httpClient = HttpClient.newBuilder()
+            .cookieHandler(new CookieManager(null, CookiePolicy.ACCEPT_NONE))
+            .build();
+
+        httpClient.send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertTrue(httpClient.cookieHandler()
+            .isPresent());
+    }
+
+    @Test
+    public void shouldStoreCookieWhenPolicyAcceptAll() throws URISyntaxException, IOException, InterruptedException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .GET()
+            .build();
+
+        HttpClient httpClient = HttpClient.newBuilder()
+            .cookieHandler(new CookieManager(null, CookiePolicy.ACCEPT_ALL))
+            .build();
+
+        httpClient.send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertTrue(httpClient.cookieHandler()
+            .isPresent());
+    }
+
+    @Test
+    public void shouldProcessMultipleRequestViaStream() throws URISyntaxException, ExecutionException, InterruptedException {
+        List<URI> targets = Arrays.asList(new URI("https://postman-echo.com/get?foo1=bar1"), new URI("https://postman-echo.com/get?foo2=bar2"));
+
+        HttpClient client = HttpClient.newHttpClient();
+
+        List<CompletableFuture<String>> futures = targets.stream()
+            .map(target -> client.sendAsync(HttpRequest.newBuilder(target)
+                .GET()
+                .build(), HttpResponse.BodyHandlers.ofString())
+                .thenApply(response -> response.body()))
+            .collect(Collectors.toList());
+
+        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0]))
+            .join();
+
+        if (futures.get(0)
+            .get()
+            .contains("foo1")) {
+            assertThat(futures.get(0)
+                .get(), containsString("bar1"));
+            assertThat(futures.get(1)
+                .get(), containsString("bar2"));
+        } else {
+            assertThat(futures.get(1)
+                .get(), containsString("bar2"));
+            assertThat(futures.get(1)
+                .get(), containsString("bar1"));
+        }
+
+    }
+    
+    @Test
+    public void completeExceptionallyExample() {
+        CompletableFuture<String> cf = CompletableFuture.completedFuture("message").thenApplyAsync(String::toUpperCase,
+                CompletableFuture.delayedExecutor(1, TimeUnit.SECONDS));
+        CompletableFuture<String> exceptionHandler = cf.handle((s, th) -> { return (th != null) ? "message upon cancel" : ""; });
+        cf.completeExceptionally(new RuntimeException("completed exceptionally"));
+        assertTrue("Was not completed exceptionally", cf.isCompletedExceptionally());
+        try {
+            cf.join();
+            fail("Should have thrown an exception");
+        } catch (CompletionException ex) { // just for testing
+            assertEquals("completed exceptionally", ex.getCause().getMessage());
+        }
+
+        assertEquals("message upon cancel", exceptionHandler.join());
+    }
+
+}

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

@@ -0,0 +1,168 @@
+package com.baeldung.java11.httpclient.test;
+
+import static java.time.temporal.ChronoUnit.SECONDS;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertThat;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.file.Paths;
+import java.security.NoSuchAlgorithmException;
+import java.time.Duration;
+
+import org.junit.Test;
+
+public class HttpRequestTest {
+
+    @Test
+    public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .GET()
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+    }
+
+    @Test
+    public void shouldUseHttp2WhenWebsiteUsesHttp2() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://stackoverflow.com"))
+            .version(HttpClient.Version.HTTP_2)
+            .GET()
+            .build();
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response.version(), equalTo(HttpClient.Version.HTTP_2));
+    }
+
+    @Test
+    public void shouldFallbackToHttp1_1WhenWebsiteDoesNotUseHttp2() throws IOException, InterruptedException, URISyntaxException, NoSuchAlgorithmException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .version(HttpClient.Version.HTTP_2)
+            .GET()
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.version(), equalTo(HttpClient.Version.HTTP_1_1));
+    }
+
+    @Test
+    public void shouldReturnStatusOKWhenSendGetRequestWithDummyHeaders() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .headers("key1", "value1", "key2", "value2")
+            .GET()
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+    }
+
+    @Test
+    public void shouldReturnStatusOKWhenSendGetRequestTimeoutSet() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .timeout(Duration.of(10, SECONDS))
+            .GET()
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+    }
+
+    @Test
+    public void shouldReturnNoContentWhenPostWithNoBody() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/post"))
+            .POST(HttpRequest.BodyPublishers.noBody())
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+    }
+
+    @Test
+    public void shouldReturnSampleDataContentWhenPostWithBodyText() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/post"))
+            .headers("Content-Type", "text/plain;charset=UTF-8")
+            .POST(HttpRequest.BodyPublishers.ofString("Sample request body"))
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response.body(), containsString("Sample request body"));
+    }
+
+    @Test
+    public void shouldReturnSampleDataContentWhenPostWithInputStream() throws IOException, InterruptedException, URISyntaxException {
+        byte[] sampleData = "Sample request body".getBytes();
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/post"))
+            .headers("Content-Type", "text/plain;charset=UTF-8")
+            .POST(HttpRequest.BodyPublishers.ofInputStream(() -> new ByteArrayInputStream(sampleData)))
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response.body(), containsString("Sample request body"));
+    }
+
+    @Test
+    public void shouldReturnSampleDataContentWhenPostWithByteArrayProcessorStream() throws IOException, InterruptedException, URISyntaxException {
+        byte[] sampleData = "Sample request body".getBytes();
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/post"))
+            .headers("Content-Type", "text/plain;charset=UTF-8")
+            .POST(HttpRequest.BodyPublishers.ofByteArray(sampleData))
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response.body(), containsString("Sample request body"));
+    }
+
+    @Test
+    public void shouldReturnSampleDataContentWhenPostWithFileProcessorStream() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/post"))
+            .headers("Content-Type", "text/plain;charset=UTF-8")
+            .POST(HttpRequest.BodyPublishers.ofFile(Paths.get("src/test/resources/sample.txt")))
+            .build();
+
+        HttpResponse<String> response = HttpClient.newHttpClient()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertThat(response.body(), containsString("Sample file content"));
+    }
+
+}

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

@@ -0,0 +1,54 @@
+package com.baeldung.java11.httpclient.test;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThat;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+
+import org.junit.Test;
+
+public class HttpResponseTest {
+
+    @Test
+    public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("https://postman-echo.com/get"))
+            .version(HttpClient.Version.HTTP_2)
+            .GET()
+            .build();
+
+        HttpResponse<String> response = HttpClient.newBuilder()
+            .followRedirects(HttpClient.Redirect.NORMAL)
+            .build()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_OK));
+        assertNotNull(response.body());
+    }
+
+    @Test
+    public void shouldResponseURIDifferentThanRequestUIRWhenRedirect() throws IOException, InterruptedException, URISyntaxException {
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(new URI("http://stackoverflow.com"))
+            .version(HttpClient.Version.HTTP_2)
+            .GET()
+            .build();
+        HttpResponse<String> response = HttpClient.newBuilder()
+            .followRedirects(HttpClient.Redirect.NORMAL)
+            .build()
+            .send(request, HttpResponse.BodyHandlers.ofString());
+
+        assertThat(request.uri()
+            .toString(), equalTo("http://stackoverflow.com"));
+        assertThat(response.uri()
+            .toString(), equalTo("https://stackoverflow.com/"));
+    }
+
+}

core-java-8/pom.xml

@@ -4,8 +4,8 @@
     <groupId>com.baeldung</groupId>
     <artifactId>core-java-8</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>core-java-8</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -180,7 +180,6 @@
         <commons-collections4.version>4.1</commons-collections4.version>
         <collections-generic.version>4.01</collections-generic.version>
         <commons-codec.version>1.10</commons-codec.version>
-        <lombok.version>1.16.12</lombok.version>
         <vavr.version>0.9.0</vavr.version>
         <protonpack.version>1.13</protonpack.version>
         <joda.version>2.10</joda.version>

core-java-8/src/main/java/com/baeldung/customannotations/Init.java

@@ -0,0 +1,13 @@
+package com.baeldung.customannotations;
+
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+@Retention(RUNTIME)
+@Target(METHOD)
+public @interface Init {
+
+}

core-java-8/src/main/java/com/baeldung/customannotations/JsonElement.java

@@ -0,0 +1,13 @@
+package com.baeldung.customannotations;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+@Retention(RUNTIME)
+@Target({ FIELD })
+public @interface JsonElement {
+    public String key() default "";
+}

core-java-8/src/main/java/com/baeldung/customannotations/JsonSerializable.java

@@ -0,0 +1,13 @@
+package com.baeldung.customannotations;
+
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+@Retention(RUNTIME)
+@Target(TYPE)
+public @interface JsonSerializable {
+
+}

core-java-8/src/main/java/com/baeldung/customannotations/JsonSerializationException.java

@@ -0,0 +1,10 @@
+package com.baeldung.customannotations;
+
+public class JsonSerializationException extends RuntimeException {
+
+    private static final long serialVersionUID = 1L;
+
+    public JsonSerializationException(String message) {
+        super(message);
+    }
+}

core-java-8/src/main/java/com/baeldung/customannotations/ObjectToJsonConverter.java

@@ -0,0 +1,67 @@
+package com.baeldung.customannotations;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+public class ObjectToJsonConverter {
+    public String convertToJson(Object object) throws JsonSerializationException {
+        try {
+
+            checkIfSerializable(object);
+            initializeObject(object);
+            return getJsonString(object);
+
+        } catch (Exception e) {
+            throw new JsonSerializationException(e.getMessage());
+        }
+    }
+
+    private void checkIfSerializable(Object object) {
+        if (Objects.isNull(object)) {
+            throw new JsonSerializationException("Can't serialize a null object");
+        }
+
+        Class<?> clazz = object.getClass();
+        if (!clazz.isAnnotationPresent(JsonSerializable.class)) {
+            throw new JsonSerializationException("The class " + clazz.getSimpleName() + " is not annotated with JsonSerializable");
+        }
+    }
+
+    private void initializeObject(Object object) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {
+        Class<?> clazz = object.getClass();
+        for (Method method : clazz.getDeclaredMethods()) {
+            if (method.isAnnotationPresent(Init.class)) {
+                method.setAccessible(true);
+                method.invoke(object);
+            }
+        }
+    }
+
+    private String getJsonString(Object object) throws IllegalArgumentException, IllegalAccessException {
+        Class<?> clazz = object.getClass();
+        Map<String, String> jsonElementsMap = new HashMap<>();
+        for (Field field : clazz.getDeclaredFields()) {
+            field.setAccessible(true);
+            if (field.isAnnotationPresent(JsonElement.class)) {
+                jsonElementsMap.put(getKey(field), (String) field.get(object));
+            }
+        }
+
+        String jsonString = jsonElementsMap.entrySet()
+            .stream()
+            .map(entry -> "\"" + entry.getKey() + "\":\"" + entry.getValue() + "\"")
+            .collect(Collectors.joining(","));
+        return "{" + jsonString + "}";
+    }
+
+    private String getKey(Field field) {
+        String value = field.getAnnotation(JsonElement.class)
+            .key();
+        return value.isEmpty() ? field.getName() : value;
+    }
+}

core-java-8/src/main/java/com/baeldung/customannotations/Person.java

@@ -0,0 +1,66 @@
+package com.baeldung.customannotations;
+
+@JsonSerializable
+public class Person {
+    @JsonElement
+    private String firstName;
+    @JsonElement
+    private String lastName;
+    @JsonElement(key = "personAge")
+    private String age;
+
+    private String address;
+
+    public Person(String firstName, String lastName) {
+        super();
+        this.firstName = firstName;
+        this.lastName = lastName;
+    }
+
+    public Person(String firstName, String lastName, String age) {
+        this.firstName = firstName;
+        this.lastName = lastName;
+        this.age = age;
+    }
+
+    @Init
+    private void initNames() {
+        this.firstName = this.firstName.substring(0, 1)
+            .toUpperCase() + this.firstName.substring(1);
+        this.lastName = this.lastName.substring(0, 1)
+            .toUpperCase() + this.lastName.substring(1);
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    public String getAge() {
+        return age;
+    }
+
+    public void setAge(String age) {
+        this.age = age;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+}

core-java-8/src/main/java/com/baeldung/streamreduce/application/Application.java

@@ -0,0 +1,62 @@
+package com.baeldung.streamreduce.application;
+
+import com.baeldung.streamreduce.entities.User;
+import com.baeldung.streamreduce.utilities.NumberUtils;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Application {
+
+    public static void main(String[] args) {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        int result1 = numbers.stream().reduce(0, (a, b) -> a + b);
+        System.out.println(result1);
+        
+        int result2 = numbers.stream().reduce(0, Integer::sum);
+        System.out.println(result2);
+
+        List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
+        String result3 = letters.stream().reduce("", (a, b) -> a + b);
+        System.out.println(result3);
+        
+        String result4 = letters.stream().reduce("", String::concat);
+        System.out.println(result4);
+
+        String result5 = letters.stream().reduce("", (a, b) -> a.toUpperCase() + b.toUpperCase());
+        System.out.println(result5);
+        
+        List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
+        int result6 = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        System.out.println(result6);
+        
+        String result7 = letters.parallelStream().reduce("", String::concat);
+        System.out.println(result7);
+        
+        int result8 = users.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        System.out.println(result8);
+        
+        List<User> userList = new ArrayList<>();
+        for (int i = 0; i <= 1000000; i++) {
+            userList.add(new User("John" + i, i));
+        }
+        
+        long t1 = System.currentTimeMillis();
+        int result9 = userList.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        long t2 = System.currentTimeMillis();
+        System.out.println(result9);
+        System.out.println("Sequential stream time: " + (t2 - t1) + "ms");
+        
+        long t3 = System.currentTimeMillis();
+        int result10 = userList.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        long t4 = System.currentTimeMillis();
+        System.out.println(result10);
+        System.out.println("Parallel stream time: " + (t4 - t3) + "ms");
+        
+        int result11 = NumberUtils.divideListElements(numbers, 1);
+        System.out.println(result11);
+        
+        int result12 = NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 0);
+        System.out.println(result12);
+    }    
+}

core-java-8/src/main/java/com/baeldung/streamreduce/entities/User.java

@@ -0,0 +1,25 @@
+package com.baeldung.streamreduce.entities;
+
+public class User {
+
+    private final String name;
+    private final int age;
+
+    public User(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+    
+    @Override
+    public String toString() {
+        return "User{" + "name=" + name + ", age=" + age + '}';
+    }
+}

core-java-8/src/main/java/com/baeldung/streamreduce/utilities/NumberUtils.java

@@ -0,0 +1,52 @@
+package com.baeldung.streamreduce.utilities;
+
+import java.util.List;
+import java.util.function.BiFunction;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public abstract class NumberUtils {
+
+    private static final Logger LOGGER = Logger.getLogger(NumberUtils.class.getName());
+
+    public static int divideListElements(List<Integer> values, Integer divider) {
+        return values.stream()
+                .reduce(0, (a, b) -> {
+                    try {
+                        return a / divider + b / divider;
+                    } catch (ArithmeticException e) {
+                        LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
+                    }
+                    return 0;
+                });
+    }
+    
+    public static int divideListElementsWithExtractedTryCatchBlock(List<Integer> values, int divider) {
+        return values.stream().reduce(0, (a, b) -> divide(a, divider) + divide(b, divider));
+    }
+    
+    public static int divideListElementsWithApplyFunctionMethod(List<Integer> values, int divider) {
+        BiFunction<Integer, Integer, Integer> division = (a, b) -> a / b;
+        return values.stream().reduce(0, (a, b) -> applyFunction(division, a, divider) + applyFunction(division, b, divider));
+    }
+    
+    private static int divide(int value, int factor) {
+        int result = 0;
+        try {
+            result = value / factor;
+        } catch (ArithmeticException e) {
+            LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
+        }
+        return result;
+    }
+    
+    private static int applyFunction(BiFunction<Integer, Integer, Integer> function, int a, int b) {
+        try {
+            return function.apply(a, b);
+        }
+        catch(Exception e) {
+            LOGGER.log(Level.INFO, "Exception occurred!");
+        }
+        return 0;
+    }
+}

core-java-8/src/test/java/com/baeldung/collectors/Java8CollectorsUnitTest.java

@@ -39,6 +39,7 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
 public class Java8CollectorsUnitTest {
 
     private final List<String> givenList = Arrays.asList("a", "bb", "ccc", "dd");
+    private final List<String> listWithDuplicates = Arrays.asList("a", "bb", "c", "d", "bb");
 
     @Test
     public void whenCollectingToList_shouldCollectToList() throws Exception {
@@ -48,12 +49,19 @@ public class Java8CollectorsUnitTest {
     }
 
     @Test
-    public void whenCollectingToList_shouldCollectToSet() throws Exception {
+    public void whenCollectingToSet_shouldCollectToSet() throws Exception {
         final Set<String> result = givenList.stream().collect(toSet());
 
         assertThat(result).containsAll(givenList);
     }
 
+    @Test
+    public void givenContainsDuplicateElements_whenCollectingToSet_shouldAddDuplicateElementsOnlyOnce() throws Exception {
+        final Set<String> result = listWithDuplicates.stream().collect(toSet());
+
+        assertThat(result).hasSize(4);
+    }
+
     @Test
     public void whenCollectingToCollection_shouldCollectToCollection() throws Exception {
         final List<String> result = givenList.stream().collect(toCollection(LinkedList::new));
@@ -77,10 +85,23 @@ public class Java8CollectorsUnitTest {
     }
 
     @Test
-    public void whenCollectingToMap_shouldCollectToMapMerging() throws Exception {
-        final Map<String, Integer> result = givenList.stream().collect(toMap(Function.identity(), String::length, (i1, i2) -> i1));
+    public void whenCollectingToMapwWithDuplicates_shouldCollectToMapMergingTheIdenticalItems() throws Exception {
+        final Map<String, Integer> result = listWithDuplicates.stream().collect(
+          toMap(
+            Function.identity(),
+            String::length,
+            (item, identicalItem) -> item
+          )
+        );
 
-        assertThat(result).containsEntry("a", 1).containsEntry("bb", 2).containsEntry("ccc", 3).containsEntry("dd", 2);
+        assertThat(result).containsEntry("a", 1).containsEntry("bb", 2).containsEntry("c", 1).containsEntry("d", 1);
+    }
+
+    @Test
+    public void givenContainsDuplicateElements_whenCollectingToMap_shouldThrowException() throws Exception {
+        assertThatThrownBy(() -> {
+            listWithDuplicates.stream().collect(toMap(Function.identity(), String::length));
+        }).isInstanceOf(IllegalStateException.class);
     }
 
     @Test

core-java-8/src/test/java/com/baeldung/customannotations/JsonSerializerUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.customannotations;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+public class JsonSerializerUnitTest {
+
+    @Test
+    public void givenObjectNotSerializedThenExceptionThrown() throws JsonSerializationException {
+        Object object = new Object();
+        ObjectToJsonConverter serializer = new ObjectToJsonConverter();
+        assertThrows(JsonSerializationException.class, () -> {
+            serializer.convertToJson(object);
+        });
+    }
+
+    @Test
+    public void givenObjectSerializedThenTrueReturned() throws JsonSerializationException {
+        Person person = new Person("soufiane", "cheouati", "34");
+        ObjectToJsonConverter serializer = new ObjectToJsonConverter();
+        String jsonString = serializer.convertToJson(person);
+        assertEquals("{\"personAge\":\"34\",\"firstName\":\"Soufiane\",\"lastName\":\"Cheouati\"}", jsonString);
+    }
+}

core-java-8/src/test/java/com/baeldung/java8/lambda/methodreference/Bicycle.java

@@ -5,6 +5,11 @@ public class Bicycle {
     private String brand;
     private Integer frameSize;
 
+    public Bicycle(String brand) {
+        this.brand = brand;
+        this.frameSize = 0;
+    }
+
     public Bicycle(String brand, Integer frameSize) {
         this.brand = brand;
         this.frameSize = frameSize;

core-java-8/src/test/java/com/baeldung/java8/lambda/methodreference/MethodReferenceUnitTest.java

@@ -5,9 +5,10 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.function.BiFunction;
 
+import org.apache.commons.lang3.StringUtils;
 import org.junit.Test;
 
-public class MethodReferenceExamples {
+public class MethodReferenceUnitTest {
 
     private static <T> void doNothingAtAll(Object... o) {
     }
@@ -17,10 +18,8 @@ public class MethodReferenceExamples {
     @Test
     public void referenceToStaticMethod() {
         List<String> messages = Arrays.asList("Hello", "Baeldung", "readers!");
-        messages.forEach((word) -> {
-            System.out.println(word);
-        });
-        messages.forEach(System.out::println);
+        messages.forEach(word -> StringUtils.capitalize(word));
+        messages.forEach(StringUtils::capitalize);
     }
 
     @Test
@@ -52,10 +51,18 @@ public class MethodReferenceExamples {
         bikes.add(bikeCreatorMethodReference.apply("GT", 40));
     }
 
+    @Test
+    public void referenceToConstructorSimpleExample() {
+        List<String> bikeBrands = Arrays.asList("Giant", "Scott", "Trek", "GT");
+        bikeBrands.stream()
+            .map(Bicycle::new)
+            .toArray(Bicycle[]::new);
+    }
+
     @Test
     public void limitationsAndAdditionalExamples() {
         createBicyclesList().forEach(b -> System.out.printf("Bike brand is '%s' and frame size is '%d'%n", b.getBrand(), b.getFrameSize()));
-        createBicyclesList().forEach((o) -> this.doNothingAtAll(o));
+        createBicyclesList().forEach((o) -> MethodReferenceUnitTest.doNothingAtAll(o));
     }
 
     private List<Bicycle> createBicyclesList() {

core-java-8/src/test/java/com/baeldung/streamreduce/tests/StreamReduceManualTest.java

@@ -0,0 +1,126 @@
+package com.baeldung.streamreduce.tests;
+
+import com.baeldung.streamreduce.entities.User;
+import com.baeldung.streamreduce.utilities.NumberUtils;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class StreamReduceManualTest {
+
+    @Test
+    public void givenIntegerList_whenReduceWithSumAccumulatorLambda_thenCorrect() {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        
+        int result = numbers.stream().reduce(0, (a, b) -> a + b);
+        
+        assertThat(result).isEqualTo(21);
+    }
+
+    @Test
+    public void givenIntegerList_whenReduceWithSumAccumulatorMethodReference_thenCorrect() {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        
+        int result = numbers.stream().reduce(0, Integer::sum);
+        
+        assertThat(result).isEqualTo(21);
+    }
+
+    @Test
+    public void givenStringList_whenReduceWithConcatenatorAccumulatorLambda_thenCorrect() {
+        List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
+        
+        String result = letters.stream().reduce("", (a, b) -> a + b);
+        
+        assertThat(result).isEqualTo("abcde");
+    }
+
+    @Test
+    public void givenStringList_whenReduceWithConcatenatorAccumulatorMethodReference_thenCorrect() {
+        List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
+        
+        String result = letters.stream().reduce("", String::concat);
+        
+        assertThat(result).isEqualTo("abcde");
+    }
+
+    @Test
+    public void givenStringList_whenReduceWithUppercaseConcatenatorAccumulator_thenCorrect() {
+        List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
+        
+        String result = letters.stream().reduce("", (a, b) -> a.toUpperCase() + b.toUpperCase());
+        
+        assertThat(result).isEqualTo("ABCDE");
+    }
+
+    @Test
+    public void givenUserList_whenReduceWithAgeAccumulatorAndSumCombiner_thenCorrect() {
+        List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
+        
+        int result = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        
+        assertThat(result).isEqualTo(65);
+    }
+
+    @Test
+    public void givenStringList_whenReduceWithParallelStream_thenCorrect() {
+        List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
+        
+        String result = letters.parallelStream().reduce("", String::concat);
+        
+        assertThat(result).isEqualTo("abcde");
+    }
+
+    @Test
+    public void givenNumberUtilsClass_whenCalledDivideListElements_thenCorrect() {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        
+        assertThat(NumberUtils.divideListElements(numbers, 1)).isEqualTo(21);
+    }
+
+    @Test
+    public void givenNumberUtilsClass_whenCalledDivideListElementsWithExtractedTryCatchBlock_thenCorrect() {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        
+        assertThat(NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 1)).isEqualTo(21);
+    }
+
+    @Test
+    public void givenNumberUtilsClass_whenCalledDivideListElementsWithExtractedTryCatchBlockAndListContainsZero_thenCorrect() {
+        List<Integer> numbers = Arrays.asList(0, 1, 2, 3, 4, 5, 6);
+        
+        assertThat(NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 1)).isEqualTo(21);
+    }
+    
+    @Test
+    public void givenNumberUtilsClass_whenCalledDivideListElementsWithExtractedTryCatchBlockAndDividerIsZero_thenCorrect() {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        
+        assertThat(NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 0)).isEqualTo(0);
+    }
+    
+    @Test
+    public void givenStream_whneCalleddivideListElementsWithApplyFunctionMethod_thenCorrect() {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        
+        assertThat(NumberUtils.divideListElementsWithApplyFunctionMethod(numbers, 1)).isEqualTo(21);
+    }
+    
+    @Test
+    public void givenTwoStreams_whenCalledReduceOnParallelizedStream_thenFasterExecutionTime() {
+        List<User> userList = new ArrayList<>();
+        for (int i = 0; i <= 1000000; i++) {
+            userList.add(new User("John" + i, i));
+        }
+        long currentTime1 = System.currentTimeMillis();
+        userList.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        long sequentialExecutionTime = System.currentTimeMillis() -currentTime1;
+        long currentTime2 = System.currentTimeMillis();
+        userList.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        long parallelizedExecutionTime = System.currentTimeMillis() - currentTime2;
+        
+        assertThat(parallelizedExecutionTime).isLessThan(sequentialExecutionTime);
+    }
+}

core-java-9/README.md

@@ -26,3 +26,4 @@
 - [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
 - [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
 - [Guide to java.lang.Process API](https://www.baeldung.com/java-process-api)
+- [Immutable Set in Java](https://www.baeldung.com/java-immutable-set)

core-java-9/compile-aot.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+cd src/main/java
+javac com/baeldung/java9/aot/JaotCompilation.java
+jaotc --output jaotCompilation.so com/baeldung/java9/aot/JaotCompilation.class
+

core-java-9/run-aot.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+cd src/main/java
+java -XX:AOTLibrary=./jaotCompilation.so com/baeldung/java9/aot/JaotCompilation

core-java-9/src/main/java/com/baeldung/java9/aot/JaotCompilation.java

@@ -0,0 +1,12 @@
+package com.baeldung.java9.aot;
+
+public class JaotCompilation {
+
+    public static void main(String[] argv) {
+        System.out.println(message());
+    }
+
+    public static String message() {
+        return "The JAOT compiler says 'Hello'";
+    }
+}

core-java-9/src/main/java/com/baeldung/multireleaseapp/App.java

@@ -0,0 +1,16 @@
+package com.baeldung.multireleaseapp;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class App {
+
+    private static final Logger logger = LoggerFactory.getLogger(App.class);
+    
+    public static void main(String[] args) throws Exception {
+        String dateToCheck = args[0];
+        boolean isLeapYear = DateHelper.checkIfLeapYear(dateToCheck);
+        logger.info("Date given " + dateToCheck + " is leap year: " + isLeapYear);
+    }
+
+}

core-java-9/src/main/java/com/baeldung/multireleaseapp/DateHelper.java

@@ -0,0 +1,22 @@
+package com.baeldung.multireleaseapp;
+
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+import java.util.GregorianCalendar;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class DateHelper {
+
+    private static final Logger logger = LoggerFactory.getLogger(DateHelper.class);
+
+    public static boolean checkIfLeapYear(String dateStr) throws Exception {
+        logger.info("Checking for leap year using Java 1 calendar API");
+        Calendar cal = Calendar.getInstance();
+        cal.setTime(new SimpleDateFormat("yyyy-MM-dd").parse(dateStr));
+        int year = cal.get(Calendar.YEAR);
+        return (new GregorianCalendar()).isLeapYear(year);
+    }
+
+}

core-java-9/src/main/java9/com/baeldung/multireleaseapp/DateHelper.java

@@ -0,0 +1,18 @@
+package com.baeldung.multireleaseapp;
+
+import java.time.LocalDate;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class DateHelper {
+
+    private static final Logger logger = LoggerFactory.getLogger(DateHelper.class);
+
+    public static boolean checkIfLeapYear(String dateStr) throws Exception {
+        logger.info("Checking for leap year using Java 9 Date Api");
+        return LocalDate.parse(dateStr)
+            .isLeapYear();
+    }
+
+}

core-java-arrays/README.md

@@ -14,3 +14,4 @@
 - [Array Operations in Java](http://www.baeldung.com/java-common-array-operations)
 - [Intersection Between two Integer Arrays](https://www.baeldung.com/java-array-intersection)
 - [Sorting Arrays in Java](https://www.baeldung.com/java-sorting-arrays)
+- [Convert a Float to a Byte Array in Java](https://www.baeldung.com/java-convert-float-to-byte-array)

core-java-arrays/pom.xml

@@ -4,8 +4,8 @@
     <groupId>com.baeldung</groupId>
     <artifactId>core-java-arrays</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>core-java-arrays</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -390,7 +390,6 @@
 
         <!-- util -->
         <commons-lang3.version>3.8.1</commons-lang3.version>
-        <lombok.version>1.16.12</lombok.version>
         
         <jmh-core.version>1.19</jmh-core.version>
         <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>

core-java-collections-list/README.md

@@ -27,3 +27,4 @@
 - [Flattening Nested Collections in Java](http://www.baeldung.com/java-flatten-nested-collections)
 - [Intersection of Two Lists in Java](https://www.baeldung.com/java-lists-intersection)
 - [Multi Dimensional ArrayList in Java](https://www.baeldung.com/java-multi-dimensional-arraylist)
+- [Determine If All Elements Are the Same in a Java List](https://www.baeldung.com/java-list-all-equal)

core-java-collections-list/pom.xml

@@ -3,8 +3,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-collections-list</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>core-java-collections-list</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -36,6 +36,33 @@
             <version>${lombok.version}</version>
             <scope>provided</scope>
         </dependency>
+
+        <dependency>
+            <groupId>net.sf.trove4j</groupId>
+            <artifactId>trove4j</artifactId>
+            <version>${trove4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>it.unimi.dsi</groupId>
+            <artifactId>fastutil</artifactId>
+            <version>${fastutil.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>colt</groupId>
+            <artifactId>colt</artifactId>
+            <version>${colt.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>
@@ -43,6 +70,8 @@
         <commons-lang3.version>3.8.1</commons-lang3.version>
         <avaitility.version>1.7.0</avaitility.version>
         <assertj.version>3.11.1</assertj.version>
-        <lombok.version>1.16.12</lombok.version>
+		<trove4j.version>3.0.2</trove4j.version>
+		<fastutil.version>8.1.0</fastutil.version>
+		<colt.version>1.2.0</colt.version>
     </properties>
 </project>

core-java-collections-list/src/main/java/com/baeldung/allequalelements/VerifyAllEqualListElements.java

@@ -0,0 +1,55 @@
+package com.baeldung.allequalelements;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import org.apache.commons.collections4.IterableUtils;
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
+
+public class VerifyAllEqualListElements {
+
+    public boolean verifyAllEqualUsingALoop(List<String> list) {
+        for (String s : list) {
+            if (!s.equals(list.get(0)))
+                return false;
+        }
+        return true;
+    }
+
+    public boolean verifyAllEqualUsingHashSet(List<String> list) {
+        return new HashSet<String>(list).size() <= 1;
+    }
+
+    public boolean verifyAllEqualUsingFrequency(List<String> list) {
+        return list.isEmpty() || Collections.frequency(list, list.get(0)) == list.size();
+    }
+
+    public boolean verifyAllEqualUsingStream(List<String> list) {
+        return list.stream()
+            .distinct()
+            .count() <= 1;
+    }
+
+    public boolean verifyAllEqualAnotherUsingStream(List<String> list) {
+        return list.isEmpty() || list.stream()
+            .allMatch(list.get(0)::equals);
+    }
+
+    public boolean verifyAllEqualUsingGuava(List<String> list) {
+        return Iterables.all(list, new Predicate<String>() {
+            public boolean apply(String s) {
+                return s.equals(list.get(0));
+            }
+        });
+    }
+
+    public boolean verifyAllEqualUsingApacheCommon(List<String> list) {
+        return IterableUtils.matchesAll(list, new org.apache.commons.collections4.Predicate<String>() {
+            public boolean evaluate(String s) {
+                return s.equals(list.get(0));
+            }
+        });
+    }
+
+}

core-java-collections-list/src/main/java/com/baeldung/list/primitive/PrimitiveCollections.java

@@ -0,0 +1,52 @@
+package com.baeldung.list.primitive;
+
+import com.google.common.primitives.ImmutableIntArray;
+import com.google.common.primitives.Ints;
+import gnu.trove.list.array.TIntArrayList;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.OptionalDouble;
+import java.util.function.IntPredicate;
+import java.util.stream.IntStream;
+
+public class PrimitiveCollections {
+
+    public static void main(String[] args) {
+
+        int[] primitives = new int[] {5, 10, 0, 2, -8};
+
+        guavaPrimitives(primitives);
+
+        intStream(primitives);
+
+        TIntArrayList tList = new TIntArrayList(primitives);
+
+        cern.colt.list.IntArrayList coltList = new cern.colt.list.IntArrayList(primitives);
+
+        IntArrayList fastUtilList = new IntArrayList(primitives);
+
+        System.out.println(tList);
+
+        System.out.println(coltList);
+
+        System.out.println(fastUtilList);
+    }
+
+    private static void intStream(int[] primitives) {
+
+        IntStream stream = IntStream.of(5, 10, 0, 2, -8);
+
+        IntStream newStream = IntStream.of(primitives);
+
+        OptionalDouble average = stream.filter(i -> i > 0).average();
+    }
+
+
+    private static void guavaPrimitives(int[] primitives) {
+
+        ImmutableIntArray immutableIntArray = ImmutableIntArray.builder().addAll(primitives).build();
+        System.out.println(immutableIntArray);
+    }
+}

core-java-collections-list/src/main/java/com/baeldung/list/primitive/PrimitivesListPerformance.java

@@ -0,0 +1,96 @@
+package com.baeldung.list.primitive;
+
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import gnu.trove.list.array.TIntArrayList;
+import org.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+@BenchmarkMode(Mode.SingleShotTime)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@Measurement(batchSize = 100000, iterations = 10)
+@Warmup(batchSize = 100000, iterations = 10)
+@State(Scope.Thread)
+public class PrimitivesListPerformance {
+
+    private List<Integer> arrayList = new ArrayList<>();
+    private TIntArrayList tList = new TIntArrayList();
+    private cern.colt.list.IntArrayList coltList = new cern.colt.list.IntArrayList();
+    private IntArrayList fastUtilList = new IntArrayList();
+
+    private int getValue = 10;
+
+    @Benchmark
+    public boolean addArrayList() {
+        return arrayList.add(getValue);
+    }
+
+    @Benchmark
+    public boolean addTroveIntList() {
+        return tList.add(getValue);
+    }
+
+    @Benchmark
+    public void addColtIntList() {
+        coltList.add(getValue);
+    }
+
+    @Benchmark
+    public boolean addFastUtilIntList() {
+        return fastUtilList.add(getValue);
+    }
+
+    @Benchmark
+    public int getArrayList() {
+        return arrayList.get(getValue);
+    }
+
+    @Benchmark
+    public int getTroveIntList() {
+        return tList.get(getValue);
+    }
+
+    @Benchmark
+    public int getColtIntList() {
+        return coltList.get(getValue);
+    }
+
+    @Benchmark
+    public int getFastUtilIntList() {
+        return fastUtilList.getInt(getValue);
+    }
+
+    @Benchmark
+    public boolean containsArrayList() {
+        return arrayList.contains(getValue);
+    }
+
+    @Benchmark
+    public boolean containsTroveIntList() {
+        return tList.contains(getValue);
+    }
+
+    @Benchmark
+    public boolean containsColtIntList() {
+        return coltList.contains(getValue);
+    }
+
+    @Benchmark
+    public boolean containsFastUtilIntList() {
+        return fastUtilList.contains(getValue);
+    }
+
+    public static void main(String[] args) throws Exception {
+        Options options = new OptionsBuilder()
+                .include(PrimitivesListPerformance.class.getSimpleName()).threads(1)
+                .forks(1).shouldFailOnError(true)
+                .shouldDoGC(true)
+                .jvmArgs("-server").build();
+        new Runner(options).run();
+    }
+}

core-java-collections-list/src/test/java/com/baeldung/allequalelements/VerifyAllEqualListElementsUnitTest.java

@@ -0,0 +1,172 @@
+package com.baeldung.allequalelements;
+
+import org.junit.Test;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import static org.junit.Assert.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class VerifyAllEqualListElementsUnitTest {
+
+    private static List<String> notAllEqualList = new ArrayList<>();
+
+    private static List<String> emptyList = new ArrayList<>();
+
+    private static List<String> allEqualList = new ArrayList<>();
+
+    static {
+        notAllEqualList = Arrays.asList("Jack", "James", "Sam", "James");
+        emptyList = Arrays.asList();
+        allEqualList = Arrays.asList("Jack", "Jack", "Jack", "Jack");
+    }
+
+    private static VerifyAllEqualListElements verifyAllEqualListElements = new VerifyAllEqualListElements();
+
+    @Test
+    public void givenNotAllEqualList_whenUsingALoop_thenReturnFalse() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingALoop(notAllEqualList);
+
+        assertFalse(allEqual);
+    }
+
+    @Test
+    public void givenEmptyList_whenUsingALoop_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingALoop(emptyList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenAllEqualList_whenUsingALoop_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingALoop(allEqualList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenNotAllEqualList_whenUsingHashSet_thenReturnFalse() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingHashSet(notAllEqualList);
+
+        assertFalse(allEqual);
+    }
+
+    @Test
+    public void givenEmptyList_whenUsingHashSet_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingHashSet(emptyList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenAllEqualList_whenUsingHashSet_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingHashSet(allEqualList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenNotAllEqualList_whenUsingFrequency_thenReturnFalse() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingFrequency(notAllEqualList);
+
+        assertFalse(allEqual);
+    }
+
+    @Test
+    public void givenEmptyList_whenUsingFrequency_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingFrequency(emptyList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenAllEqualList_whenUsingFrequency_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingFrequency(allEqualList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenNotAllEqualList_whenUsingStream_thenReturnFalse() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingStream(notAllEqualList);
+
+        assertFalse(allEqual);
+    }
+
+    @Test
+    public void givenEmptyList_whenUsingStream_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingStream(emptyList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenAllEqualList_whenUsingStream_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingStream(allEqualList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenNotAllEqualList_whenUsingAnotherStream_thenReturnFalse() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualAnotherUsingStream(notAllEqualList);
+
+        assertFalse(allEqual);
+    }
+
+    @Test
+    public void givenEmptyList_whenUsingAnotherStream_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualAnotherUsingStream(emptyList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenAllEqualList_whenUsingAnotherStream_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualAnotherUsingStream(allEqualList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenNotAllEqualList_whenUsingGuava_thenReturnFalse() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingGuava(notAllEqualList);
+
+        assertFalse(allEqual);
+    }
+
+    @Test
+    public void givenEmptyList_whenUsingGuava_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingGuava(emptyList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenAllEqualList_whenUsingGuava_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingGuava(allEqualList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenNotAllEqualList_whenUsingApacheCommon_thenReturnFalse() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingApacheCommon(notAllEqualList);
+
+        assertFalse(allEqual);
+    }
+
+    @Test
+    public void givenEmptyList_whenUsingApacheCommon_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingApacheCommon(emptyList);
+
+        assertTrue(allEqual);
+    }
+
+    @Test
+    public void givenAllEqualList_whenUsingApacheCommon_thenReturnTrue() {
+        boolean allEqual = verifyAllEqualListElements.verifyAllEqualUsingApacheCommon(allEqualList);
+
+        assertTrue(allEqual);
+    }
+}

core-java-collections/README.md

@@ -31,3 +31,4 @@
 - [A Guide to EnumMap](https://www.baeldung.com/java-enum-map)
 - [A Guide to Iterator in Java](http://www.baeldung.com/java-iterator)
 - [Differences Between HashMap and Hashtable](https://www.baeldung.com/hashmap-hashtable-differences)
+- [Java ArrayList vs Vector](https://www.baeldung.com/java-arraylist-vs-vector)

core-java-collections/pom.xml

@@ -3,8 +3,8 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-collections</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
     <name>core-java-collections</name>
+    <packaging>jar</packaging>
 
     <parent>
         <groupId>com.baeldung</groupId>
@@ -54,7 +54,7 @@
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-exec</artifactId>
-            <version>1.3</version>
+            <version>${commons-exec.version}</version>
         </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
@@ -73,6 +73,6 @@
         <avaitility.version>1.7.0</avaitility.version>
         <assertj.version>3.11.1</assertj.version>
         <eclipse.collections.version>7.1.0</eclipse.collections.version>
-        <lombok.version>1.16.12</lombok.version>
+		<commons-exec.version>1.3</commons-exec.version>
     </properties>
 </project>

core-java-collections/src/main/java/com/baeldung/charstack/CharStack.java

@@ -0,0 +1,37 @@
+package com.baeldung.charstack;
+
+import java.util.Iterator;
+import java.util.LinkedList;
+
+public class CharStack {
+
+    private LinkedList<Character> items;
+
+    public CharStack() {
+        this.items = new LinkedList<Character>();
+    }
+
+    public void push(Character item) {
+        items.push(item);
+    }
+
+    public Character peek() {
+        return items.getFirst();
+    }
+
+    public Character pop() {
+
+        Iterator<Character> iter = items.iterator();
+        Character item = iter.next();
+        if (item != null) {
+            iter.remove();
+            return item;
+        }
+        return null;
+    }
+
+    public int size() {
+        return items.size();
+    }
+
+}