Merge branch 'master' into master

2019-04-13 14:22:12 +03:00 · 2019-04-13 14:22:12 +03:00 · 3990032d76
parent eaf1d3e35b 9df90567d4
commit 3990032d76
1331 changed files with 72513 additions and 4984 deletions
--- a/akka-streams/pom.xml
+++ b/akka-streams/pom.xml
@ -14,18 +14,19 @@
    <dependencies>
        <dependency>
            <groupId>com.typesafe.akka</groupId>
-            <artifactId>akka-stream_2.11</artifactId>
+            <artifactId>akka-stream_${scala.version}</artifactId>
            <version>${akkastreams.version}</version>
        </dependency>
        <dependency>
            <groupId>com.typesafe.akka</groupId>
-            <artifactId>akka-stream-testkit_2.11</artifactId>
+            <artifactId>akka-stream-testkit_${scala.version}</artifactId>
            <version>${akkastreams.version}</version>
        </dependency>
    </dependencies>

    <properties>
        <akkastreams.version>2.5.2</akkastreams.version>
+        <scala.version>2.11</scala.version>
    </properties>

 </project>
--- a/algorithms-miscellaneous-1/README.md
+++ b/algorithms-miscellaneous-1/README.md
@ -17,3 +17,4 @@
 - [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)
+- [Generate Combinations in Java](https://www.baeldung.com/java-combinations-algorithm)
--- a/algorithms-miscellaneous-1/pom.xml
+++ b/algorithms-miscellaneous-1/pom.xml
@ -39,6 +39,11 @@
            <version>${org.assertj.core.version}</version>
            <scope>test</scope>
        </dependency>
+        <dependency>
+            <groupId>com.github.dpaukov</groupId>
+            <artifactId>combinatoricslib3</artifactId>
+            <version>3.3.0</version>
+         </dependency>
    </dependencies>

    <build>
@ -77,7 +82,7 @@
        <commons-math3.version>3.6.1</commons-math3.version>
        <org.assertj.core.version>3.9.0</org.assertj.core.version>
        <commons-codec.version>1.11</commons-codec.version>
-        <guava.version>25.1-jre</guava.version>
+        <guava.version>27.0.1-jre</guava.version>
    </properties>

 </project>
--- a/algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/relativelyprime/RelativelyPrime.java
+++ b/algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/relativelyprime/RelativelyPrime.java
@ -0,0 +1,45 @@
+package com.baeldung.algorithms.relativelyprime;
+
+import java.math.BigInteger;
+
+class RelativelyPrime {
+
+    static boolean iterativeRelativelyPrime(int a, int b) {
+        return iterativeGCD(a, b) == 1;
+    }
+
+    static boolean recursiveRelativelyPrime(int a, int b) {
+        return recursiveGCD(a, b) == 1;
+    }
+
+    static boolean bigIntegerRelativelyPrime(int a, int b) {
+        return BigInteger.valueOf(a).gcd(BigInteger.valueOf(b)).equals(BigInteger.ONE);
+    }
+
+    private static int iterativeGCD(int a, int b) {
+        int tmp;
+        while (b != 0) {
+            if (a < b) {
+                tmp = a;
+                a = b;
+                b = tmp;
+            }
+            tmp = b;
+            b = a % b;
+            a = tmp;
+        }
+        return a;
+    }
+
+    private static int recursiveGCD(int a, int b) {
+        if (b == 0) {
+            return a;
+        }
+        if (a < b) {
+            return recursiveGCD(b, a);
+        }
+        return recursiveGCD(b, a % b);
+    }
+
+
+}
--- a/algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeNode.java
+++ b/algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeNode.java
@ -0,0 +1,42 @@
+package com.baeldung.algorithms.reversingtree;
+
+public class TreeNode {
+
+    private int value;
+    private TreeNode rightChild;
+    private TreeNode leftChild;
+
+    public int getValue() {
+        return value;
+    }
+
+    public void setValue(int value) {
+        this.value = value;
+    }
+
+    public TreeNode getRightChild() {
+        return rightChild;
+    }
+
+    public void setRightChild(TreeNode rightChild) {
+        this.rightChild = rightChild;
+    }
+
+    public TreeNode getLeftChild() {
+        return leftChild;
+    }
+
+    public void setLeftChild(TreeNode leftChild) {
+        this.leftChild = leftChild;
+    }
+
+    public TreeNode(int value, TreeNode leftChild, TreeNode rightChild) {
+        this.value = value;
+        this.rightChild = rightChild;
+        this.leftChild = leftChild;
+    }
+
+    public TreeNode(int value) {
+        this.value = value;
+    }
+}
--- a/algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeReverser.java
+++ b/algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeReverser.java
@ -0,0 +1,53 @@
+package com.baeldung.algorithms.reversingtree;
+
+import java.util.LinkedList;
+
+public class TreeReverser {
+
+    public void reverseRecursive(TreeNode treeNode) {
+        if (treeNode == null) {
+            return;
+        }
+
+        TreeNode temp = treeNode.getLeftChild();
+        treeNode.setLeftChild(treeNode.getRightChild());
+        treeNode.setRightChild(temp);
+
+        reverseRecursive(treeNode.getLeftChild());
+        reverseRecursive(treeNode.getRightChild());
+    }
+
+    public void reverseIterative(TreeNode treeNode) {
+        LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
+
+        if (treeNode != null) {
+            queue.add(treeNode);
+        }
+
+        while (!queue.isEmpty()) {
+
+            TreeNode node = queue.poll();
+            if (node.getLeftChild() != null)
+                queue.add(node.getLeftChild());
+            if (node.getRightChild() != null)
+                queue.add(node.getRightChild());
+
+            TreeNode temp = node.getLeftChild();
+            node.setLeftChild(node.getRightChild());
+            node.setRightChild(temp);
+        }
+    }
+
+    public String toString(TreeNode root) {
+        if (root == null) {
+            return "";
+        }
+
+        StringBuffer buffer = new StringBuffer(String.valueOf(root.getValue())).append(" ");
+
+        buffer.append(toString(root.getLeftChild()));
+        buffer.append(toString(root.getRightChild()));
+
+        return buffer.toString();
+    }
+}
--- a/algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/relativelyprime/RelativelyPrimeUnitTest.java
+++ b/algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/relativelyprime/RelativelyPrimeUnitTest.java
@ -0,0 +1,51 @@
+package com.baeldung.algorithms.relativelyprime;
+
+import org.junit.Test;
+
+import static com.baeldung.algorithms.relativelyprime.RelativelyPrime.*;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class RelativelyPrimeUnitTest {
+
+    @Test
+    public void givenNonRelativelyPrimeNumbers_whenCheckingIteratively_shouldReturnFalse() {
+
+        boolean result = iterativeRelativelyPrime(45, 35);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenRelativelyPrimeNumbers_whenCheckingIteratively_shouldReturnTrue() {
+
+        boolean result = iterativeRelativelyPrime(500, 501);
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenNonRelativelyPrimeNumbers_whenCheckingRecursively_shouldReturnFalse() {
+
+        boolean result = recursiveRelativelyPrime(45, 35);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenRelativelyPrimeNumbers_whenCheckingRecursively_shouldReturnTrue() {
+
+        boolean result = recursiveRelativelyPrime(500, 501);
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenNonRelativelyPrimeNumbers_whenCheckingUsingBigIntegers_shouldReturnFalse() {
+
+        boolean result = bigIntegerRelativelyPrime(45, 35);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenRelativelyPrimeNumbers_whenCheckingBigIntegers_shouldReturnTrue() {
+
+        boolean result = bigIntegerRelativelyPrime(500, 501);
+        assertThat(result).isTrue();
+    }
+}
--- a/algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/reversingtree/TreeReverserUnitTest.java
+++ b/algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/reversingtree/TreeReverserUnitTest.java
@ -0,0 +1,47 @@
+package com.baeldung.algorithms.reversingtree;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class TreeReverserUnitTest {
+
+    @Test
+    public void givenTreeWhenReversingRecursivelyThenReversed() {
+        TreeReverser reverser = new TreeReverser();
+
+        TreeNode treeNode = createBinaryTree();
+
+        reverser.reverseRecursive(treeNode);
+
+        assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode)
+            .trim());
+    }
+
+    @Test
+    public void givenTreeWhenReversingIterativelyThenReversed() {
+        TreeReverser reverser = new TreeReverser();
+
+        TreeNode treeNode = createBinaryTree();
+
+        reverser.reverseIterative(treeNode);
+
+        assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode)
+            .trim());
+    }
+
+    private TreeNode createBinaryTree() {
+
+        TreeNode leaf1 = new TreeNode(1);
+        TreeNode leaf2 = new TreeNode(3);
+        TreeNode leaf3 = new TreeNode(6);
+        TreeNode leaf4 = new TreeNode(9);
+
+        TreeNode nodeRight = new TreeNode(7, leaf3, leaf4);
+        TreeNode nodeLeft = new TreeNode(2, leaf1, leaf2);
+
+        TreeNode root = new TreeNode(4, nodeLeft, nodeRight);
+
+        return root;
+    }
+}
--- a/antlr/pom.xml
+++ b/antlr/pom.xml
@ -10,6 +10,14 @@
        <version>1.0.0-SNAPSHOT</version>
    </parent>

+    <dependencies>
+        <dependency>
+            <groupId>org.antlr</groupId>
+            <artifactId>antlr4-runtime</artifactId>
+            <version>${antlr.version}</version>
+        </dependency>
+    </dependencies>
+
    <build>
        <plugins>
            <plugin>
@ -44,13 +52,7 @@
            </plugin>
        </plugins>
    </build>
-    <dependencies>
-        <dependency>
-            <groupId>org.antlr</groupId>
-            <artifactId>antlr4-runtime</artifactId>
-            <version>${antlr.version}</version>
-        </dependency>
-    </dependencies>
+    	
    <properties>
        <antlr.version>4.7.1</antlr.version>
        <mojo.version>3.0.0</mojo.version>
--- a/apache-cxf/sse-jaxrs/sse-jaxrs-client/pom.xml
+++ b/apache-cxf/sse-jaxrs/sse-jaxrs-client/pom.xml
@ -12,9 +12,18 @@
        <version>0.0.1-SNAPSHOT</version>
    </parent>

-    <properties>
-        <cxf-version>3.2.0</cxf-version>
-    </properties>
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.cxf</groupId>
+            <artifactId>cxf-rt-rs-client</artifactId>
+            <version>${cxf-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.cxf</groupId>
+            <artifactId>cxf-rt-rs-sse</artifactId>
+            <version>${cxf-version}</version>
+        </dependency>
+    </dependencies>

    <build>
        <plugins>
@ -45,17 +54,8 @@
        </plugins>
    </build>

-    <dependencies>
-        <dependency>
-            <groupId>org.apache.cxf</groupId>
-            <artifactId>cxf-rt-rs-client</artifactId>
-            <version>${cxf-version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.cxf</groupId>
-            <artifactId>cxf-rt-rs-sse</artifactId>
-            <version>${cxf-version}</version>
-        </dependency>
-    </dependencies>
+    <properties>
+        <cxf-version>3.2.0</cxf-version>
+    </properties>

 </project>
--- a/apache-cxf/sse-jaxrs/sse-jaxrs-server/pom.xml
+++ b/apache-cxf/sse-jaxrs/sse-jaxrs-server/pom.xml
@ -13,11 +13,28 @@
        <version>0.0.1-SNAPSHOT</version>
    </parent>

-    <properties>
-        <liberty-maven-plugin.version>2.4.2</liberty-maven-plugin.version>
-        <failOnMissingWebXml>false</failOnMissingWebXml>
-        <openliberty-version>18.0.0.2</openliberty-version>
-    </properties>
+    <dependencies>
+
+        <dependency>
+            <groupId>javax.ws.rs</groupId>
+            <artifactId>javax.ws.rs-api</artifactId>
+            <version>2.1</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>javax.enterprise</groupId>
+            <artifactId>cdi-api</artifactId>
+            <version>2.0</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>javax.json.bind</groupId>
+            <artifactId>javax.json.bind-api</artifactId>
+            <version>1.0</version>
+            <scope>provided</scope>
+        </dependency>
+
+    </dependencies>

    <build>
        <finalName>${project.artifactId}</finalName>
@ -59,27 +76,10 @@
        </plugins>
    </build>

-    <dependencies>
-
-        <dependency>
-            <groupId>javax.ws.rs</groupId>
-            <artifactId>javax.ws.rs-api</artifactId>
-            <version>2.1</version>
-            <scope>provided</scope>
-        </dependency>
-        <dependency>
-            <groupId>javax.enterprise</groupId>
-            <artifactId>cdi-api</artifactId>
-            <version>2.0</version>
-            <scope>provided</scope>
-        </dependency>
-        <dependency>
-            <groupId>javax.json.bind</groupId>
-            <artifactId>javax.json.bind-api</artifactId>
-            <version>1.0</version>
-            <scope>provided</scope>
-        </dependency>
-
-    </dependencies>
+    <properties>
+        <liberty-maven-plugin.version>2.4.2</liberty-maven-plugin.version>
+        <failOnMissingWebXml>false</failOnMissingWebXml>
+        <openliberty-version>18.0.0.2</openliberty-version>
+    </properties>

 </project>
--- a/apache-fop/README.md
+++ b/apache-fop/README.md
@ -3,7 +3,3 @@
 ## Core Java Cookbooks and Examples

 ### Relevant Articles: 
- [Immutable ArrayList in Java](http://www.baeldung.com/java-immutable-list)
- [Java - Reading a Large File Efficiently](http://www.baeldung.com/java-read-lines-large-file)
- [Java InputStream to String](http://www.baeldung.com/convert-input-stream-to-string)
-
--- a/apache-meecrowave/pom.xml
+++ b/apache-meecrowave/pom.xml
@ -7,6 +7,12 @@
    <name>apache-meecrowave</name>
    <description>A sample REST API application with Meecrowave</description>
    
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.apache.meecrowave/meecrowave-core -->
        <dependency>
--- a/apache-meecrowave/src/test/java/com/baeldung/meecrowave/ArticleEndpointsUnitTest.java
+++ b/apache-meecrowave/src/test/java/com/baeldung/meecrowave/ArticleEndpointsUnitTest.java
@ -17,7 +17,7 @@ import okhttp3.Request;
 import okhttp3.Response;

@RunWith(MonoMeecrowave.Runner.class)
-public class ArticleEndpointsTest {
+public class ArticleEndpointsUnitTest {
    
    @ConfigurationInject
    private Meecrowave.Builder config;
--- a/aws/README.md
+++ b/aws/README.md
@ -4,7 +4,6 @@
 - [AWS S3 with Java](http://www.baeldung.com/aws-s3-java)
 - [AWS Lambda With Java](http://www.baeldung.com/java-aws-lambda)
 - [Managing EC2 Instances in Java](http://www.baeldung.com/ec2-java)
- [http://www.baeldung.com/aws-s3-multipart-upload](https://github.com/eugenp/tutorials/tree/master/aws)
 - [Multipart Uploads in Amazon S3 with Java](http://www.baeldung.com/aws-s3-multipart-upload)
 - [Integration Testing with a Local DynamoDB Instance](http://www.baeldung.com/dynamodb-local-integration-tests)
 - [Using the JetS3t Java Client With Amazon S3](http://www.baeldung.com/jets3t-amazon-s3)
--- a/azure/README.md
+++ b/azure/README.md
@ -1,4 +1,4 @@
 ### Relevant Articles:

- [Deploy Spring Boot App to Azure](http://www.baeldung.com/spring-boot-azure)
+- [Deploy a Spring Boot App to Azure](http://www.baeldung.com/spring-boot-azure)

--- a/blade/README.md
+++ b/blade/README.md
@ -1,5 +1,5 @@
 ### Relevant Articles: 

- [Blade - A Complete GuideBook](http://www.baeldung.com/blade) 
+- [Blade – A Complete Guidebook](http://www.baeldung.com/blade) 

 Run Integration Tests with `mvn integration-test`
--- a/cas/pom.xml
+++ b/cas/pom.xml
@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
+    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</artifactId>
+    <name>cas</name>
+    <packaging>pom</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>..</relativePath>
+    </parent>
+
+    <modules>
+        <module>cas-secured-app</module>
+        <module>cas-server</module>
+    </modules>
+
+</project>
--- a/cloud-foundry-uaa/cf-uaa-config/uaa.yml
+++ b/cloud-foundry-uaa/cf-uaa-config/uaa.yml
@ -0,0 +1,68 @@
+issuer:
+  uri: http://localhost:8080/uaa
+
+spring_profiles: default,hsqldb
+  
+encryption:
+  active_key_label: CHANGE-THIS-KEY
+  encryption_keys:
+    - label: CHANGE-THIS-KEY
+      passphrase: CHANGEME
+
+login:
+  serviceProviderKey: |
+    -----BEGIN RSA PRIVATE KEY-----
+    MIICXQIBAAKBgQDHtC5gUXxBKpEqZTLkNvFwNGnNIkggNOwOQVNbpO0WVHIivig5
+    L39WqS9u0hnA+O7MCA/KlrAR4bXaeVVhwfUPYBKIpaaTWFQR5cTR1UFZJL/OF9vA
+    fpOwznoD66DDCnQVpbCjtDYWX+x6imxn8HCYxhMol6ZnTbSsFW6VZjFMjQIDAQAB
+    AoGAVOj2Yvuigi6wJD99AO2fgF64sYCm/BKkX3dFEw0vxTPIh58kiRP554Xt5ges
+    7ZCqL9QpqrChUikO4kJ+nB8Uq2AvaZHbpCEUmbip06IlgdA440o0r0CPo1mgNxGu
+    lhiWRN43Lruzfh9qKPhleg2dvyFGQxy5Gk6KW/t8IS4x4r0CQQD/dceBA+Ndj3Xp
+    ubHfxqNz4GTOxndc/AXAowPGpge2zpgIc7f50t8OHhG6XhsfJ0wyQEEvodDhZPYX
+    kKBnXNHzAkEAyCA76vAwuxqAd3MObhiebniAU3SnPf2u4fdL1EOm92dyFs1JxyyL
+    gu/DsjPjx6tRtn4YAalxCzmAMXFSb1qHfwJBAM3qx3z0gGKbUEWtPHcP7BNsrnWK
+    vw6By7VC8bk/ffpaP2yYspS66Le9fzbFwoDzMVVUO/dELVZyBnhqSRHoXQcCQQCe
+    A2WL8S5o7Vn19rC0GVgu3ZJlUrwiZEVLQdlrticFPXaFrn3Md82ICww3jmURaKHS
+    N+l4lnMda79eSp3OMmq9AkA0p79BvYsLshUJJnvbk76pCjR28PK4dV1gSDUEqQMB
+    qy45ptdwJLqLJCeNoR0JUcDNIRhOCuOPND7pcMtX6hI/
+    -----END RSA PRIVATE KEY-----
+  serviceProviderKeyPassword: password
+  serviceProviderCertificate: |
+    -----BEGIN CERTIFICATE-----
+    MIIDSTCCArKgAwIBAgIBADANBgkqhkiG9w0BAQQFADB8MQswCQYDVQQGEwJhdzEO
+    MAwGA1UECBMFYXJ1YmExDjAMBgNVBAoTBWFydWJhMQ4wDAYDVQQHEwVhcnViYTEO
+    MAwGA1UECxMFYXJ1YmExDjAMBgNVBAMTBWFydWJhMR0wGwYJKoZIhvcNAQkBFg5h
+    cnViYUBhcnViYS5hcjAeFw0xNTExMjAyMjI2MjdaFw0xNjExMTkyMjI2MjdaMHwx
+    CzAJBgNVBAYTAmF3MQ4wDAYDVQQIEwVhcnViYTEOMAwGA1UEChMFYXJ1YmExDjAM
+    BgNVBAcTBWFydWJhMQ4wDAYDVQQLEwVhcnViYTEOMAwGA1UEAxMFYXJ1YmExHTAb
+    BgkqhkiG9w0BCQEWDmFydWJhQGFydWJhLmFyMIGfMA0GCSqGSIb3DQEBAQUAA4GN
+    ADCBiQKBgQDHtC5gUXxBKpEqZTLkNvFwNGnNIkggNOwOQVNbpO0WVHIivig5L39W
+    qS9u0hnA+O7MCA/KlrAR4bXaeVVhwfUPYBKIpaaTWFQR5cTR1UFZJL/OF9vAfpOw
+    znoD66DDCnQVpbCjtDYWX+x6imxn8HCYxhMol6ZnTbSsFW6VZjFMjQIDAQABo4Ha
+    MIHXMB0GA1UdDgQWBBTx0lDzjH/iOBnOSQaSEWQLx1syGDCBpwYDVR0jBIGfMIGc
+    gBTx0lDzjH/iOBnOSQaSEWQLx1syGKGBgKR+MHwxCzAJBgNVBAYTAmF3MQ4wDAYD
+    VQQIEwVhcnViYTEOMAwGA1UEChMFYXJ1YmExDjAMBgNVBAcTBWFydWJhMQ4wDAYD
+    VQQLEwVhcnViYTEOMAwGA1UEAxMFYXJ1YmExHTAbBgkqhkiG9w0BCQEWDmFydWJh
+    QGFydWJhLmFyggEAMAwGA1UdEwQFMAMBAf8wDQYJKoZIhvcNAQEEBQADgYEAYvBJ
+    0HOZbbHClXmGUjGs+GS+xC1FO/am2suCSYqNB9dyMXfOWiJ1+TLJk+o/YZt8vuxC
+    KdcZYgl4l/L6PxJ982SRhc83ZW2dkAZI4M0/Ud3oePe84k8jm3A7EvH5wi5hvCkK
+    RpuRBwn3Ei+jCRouxTbzKPsuCVB+1sNyxMTXzf0=
+    -----END CERTIFICATE-----
+
+#The secret that an external login server will use to authenticate to the uaa using the id `login`
+LOGIN_SECRET: loginsecret
+
+jwt:
+  token:
+    signing-key: |
+      -----BEGIN RSA PRIVATE KEY-----
+      MIIEpAIBAAKCAQEAqUeygEfDGxI6c1VDQ6xIyUSLrP6iz1y97iHFbtXSxXaArL4a
+      ...
+      v6Mtt5LcRAAVP7pemunTdju4h8Q/noKYlVDVL30uLYUfKBL4UKfOBw==
+      -----END RSA PRIVATE KEY-----
+    verification-key: |
+      -----BEGIN PUBLIC KEY-----
+      MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAqUeygEfDGxI6c1VDQ6xI
+      ...
+      AwIDAQAB
+      -----END PUBLIC KEY-----
--- a/cloud-foundry-uaa/cf-uaa-oauth2-client/pom.xml
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-client/pom.xml
@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.example</groupId>
+    <artifactId>cf-uaa-oauth2-client</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>uaa-client-webapp</name>
+    <description>Demo project for Spring Boot</description>
+
+    <parent>
+        <artifactId>parent-boot-2</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-oauth2-client</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <java.version>1.8</java.version>
+    </properties>
+</project>
--- a/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/java/com/baeldung/cfuaa/oauth2/client/CFUAAOAuth2ClientApplication.java
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/java/com/baeldung/cfuaa/oauth2/client/CFUAAOAuth2ClientApplication.java
@ -0,0 +1,13 @@
+package com.baeldung.cfuaa.oauth2.client;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class CFUAAOAuth2ClientApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(CFUAAOAuth2ClientApplication.class, args);
+	}
+
+}
--- a/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/java/com/baeldung/cfuaa/oauth2/client/CFUAAOAuth2ClientController.java
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/java/com/baeldung/cfuaa/oauth2/client/CFUAAOAuth2ClientController.java
@ -0,0 +1,80 @@
+package com.baeldung.cfuaa.oauth2.client;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClient;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClientService;
+import org.springframework.security.oauth2.client.authentication.OAuth2AuthenticationToken;
+import org.springframework.security.oauth2.core.OAuth2AccessToken;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.client.HttpClientErrorException;
+import org.springframework.web.client.RestTemplate;
+
+@RestController
+public class CFUAAOAuth2ClientController {
+
+    @Value("${resource.server.url}")
+    private String remoteResourceServer;
+
+    private RestTemplate restTemplate;
+
+    private OAuth2AuthorizedClientService authorizedClientService;
+
+    public CFUAAOAuth2ClientController(OAuth2AuthorizedClientService authorizedClientService) {
+        this.authorizedClientService = authorizedClientService;
+        this.restTemplate = new RestTemplate();
+    }
+
+    @RequestMapping("/")
+    public String index(OAuth2AuthenticationToken authenticationToken) {
+        OAuth2AuthorizedClient oAuth2AuthorizedClient = this.authorizedClientService.loadAuthorizedClient(authenticationToken.getAuthorizedClientRegistrationId(), authenticationToken.getName());
+        OAuth2AccessToken oAuth2AccessToken = oAuth2AuthorizedClient.getAccessToken();
+
+        String response = "Hello, " + authenticationToken.getPrincipal().getName();
+        response += "</br></br>";
+        response += "Here is your accees token :</br>" + oAuth2AccessToken.getTokenValue();
+        response += "</br>";
+        response += "</br>You can use it to call these Resource Server APIs:";
+        response += "</br></br>";
+        response += "<a href='/read'>Call Resource Server Read API</a>";
+        response += "</br>";
+        response += "<a href='/write'>Call Resource Server Write API</a>";
+        return response;
+    }
+
+    @RequestMapping("/read")
+    public String read(OAuth2AuthenticationToken authenticationToken) {
+        String url = remoteResourceServer + "/read";
+        return callResourceServer(authenticationToken, url);
+    }
+
+    @RequestMapping("/write")
+    public String write(OAuth2AuthenticationToken authenticationToken) {
+        String url = remoteResourceServer + "/write";
+        return callResourceServer(authenticationToken, url);
+    }
+
+    private String callResourceServer(OAuth2AuthenticationToken authenticationToken, String url) {
+        OAuth2AuthorizedClient oAuth2AuthorizedClient = this.authorizedClientService.loadAuthorizedClient(authenticationToken.getAuthorizedClientRegistrationId(), authenticationToken.getName());
+        OAuth2AccessToken oAuth2AccessToken = oAuth2AuthorizedClient.getAccessToken();
+
+        HttpHeaders headers = new HttpHeaders();
+        headers.add("Authorization", "Bearer " + oAuth2AccessToken.getTokenValue());
+
+        HttpEntity<String> entity = new HttpEntity<>("parameters", headers);
+        ResponseEntity<String> responseEntity = null;
+
+        String response = null;
+        try {
+            responseEntity = restTemplate.exchange(url, HttpMethod.GET, entity, String.class);
+            response = responseEntity.getBody();
+        } catch (HttpClientErrorException e) {
+            response = e.getMessage();
+        }
+        return response;
+    }
+}
--- a/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/resources/application.properties
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/resources/application.properties
@ -0,0 +1,11 @@
+server.port=8081
+
+resource.server.url=http://localhost:8082
+
+spring.security.oauth2.client.registration.uaa.client-name=Web App Client
+spring.security.oauth2.client.registration.uaa.client-id=webappclient
+spring.security.oauth2.client.registration.uaa.client-secret=webappclientsecret
+spring.security.oauth2.client.registration.uaa.scope=resource.read,resource.write,openid,profile
+
+spring.security.oauth2.client.provider.uaa.issuer-uri=http://localhost:8080/uaa/oauth/token
+
--- a/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/resources/templates/index.html
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-client/src/main/resources/templates/index.html
@ -0,0 +1 @@
+tintin
--- a/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/pom.xml
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/pom.xml
@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung.cfuaa</groupId>
+    <artifactId>cf-uaa-oauth2-resource-server</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>cf-uaa-oauth2-resource-server</name>
+    <description>Demo project for Spring Boot</description>
+
+    <parent>
+        <artifactId>parent-boot-2</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+	
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-oauth2-resource-server</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <java.version>1.8</java.version>
+    </properties>
+
+</project>
--- a/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/java/com/baeldung/cfuaa/oauth2/resourceserver/CFUAAOAuth2ResourceServerApplication.java
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/java/com/baeldung/cfuaa/oauth2/resourceserver/CFUAAOAuth2ResourceServerApplication.java
@ -0,0 +1,13 @@
+package com.baeldung.cfuaa.oauth2.resourceserver;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class CFUAAOAuth2ResourceServerApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(CFUAAOAuth2ResourceServerApplication.class, args);
+	}
+
+}
--- a/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/java/com/baeldung/cfuaa/oauth2/resourceserver/CFUAAOAuth2ResourceServerRestController.java
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/java/com/baeldung/cfuaa/oauth2/resourceserver/CFUAAOAuth2ResourceServerRestController.java
@ -0,0 +1,28 @@
+package com.baeldung.cfuaa.oauth2.resourceserver;
+
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.oauth2.jwt.Jwt;
+import org.springframework.security.oauth2.server.resource.authentication.JwtAuthenticationToken;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.security.Principal;
+
+@RestController
+public class CFUAAOAuth2ResourceServerRestController {
+
+    @GetMapping("/")
+    public String index(@AuthenticationPrincipal Jwt jwt) {
+        return String.format("Hello, %s!", jwt.getSubject());
+    }
+
+    @GetMapping("/read")
+    public String read(JwtAuthenticationToken jwtAuthenticationToken) {
+        return "Hello write: " + jwtAuthenticationToken.getTokenAttributes();
+    }
+
+    @GetMapping("/write")
+    public String write(Principal principal) {
+        return "Hello write: " + principal.getName();
+    }
+}
--- a/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/java/com/baeldung/cfuaa/oauth2/resourceserver/CFUAAOAuth2ResourceServerSecurityConfiguration.java
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/java/com/baeldung/cfuaa/oauth2/resourceserver/CFUAAOAuth2ResourceServerSecurityConfiguration.java
@ -0,0 +1,21 @@
+package com.baeldung.cfuaa.oauth2.resourceserver;
+
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+
+@EnableWebSecurity
+public class CFUAAOAuth2ResourceServerSecurityConfiguration extends WebSecurityConfigurerAdapter {
+
+	@Override
+	protected void configure(HttpSecurity http) throws Exception {
+		http
+			.authorizeRequests()
+                .antMatchers("/read/**").hasAuthority("SCOPE_resource.read")
+                .antMatchers("/write/**").hasAuthority("SCOPE_resource.write")
+                .anyRequest().authenticated()
+				.and()
+			.oauth2ResourceServer()
+				.jwt();
+	}
+}
--- a/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/resources/application.properties
+++ b/cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/resources/application.properties
@ -0,0 +1,3 @@
+server.port=8082
+
+spring.security.oauth2.resourceserver.jwt.issuer-uri=http://localhost:8080/uaa/oauth/token
--- a/core-groovy/README.md
+++ b/core-groovy/README.md
@ -10,3 +10,6 @@
 - [An Introduction to Traits in Groovy](https://www.baeldung.com/groovy-traits)
 - [Closures in Groovy](https://www.baeldung.com/groovy-closures)
 - [Finding Elements in Collections in Groovy](https://www.baeldung.com/groovy-collections-find-elements)
+- [Lists in Groovy](https://www.baeldung.com/groovy-lists)
+- [Converting a String to a Date in Groovy](https://www.baeldung.com/groovy-string-to-date)
+- [Guide to I/O in Groovy](https://www.baeldung.com/groovy-io)
--- a/core-groovy/src/main/groovy/com/baeldung/Person.groovy
+++ b/core-groovy/src/main/groovy/com/baeldung/Person.groovy
@ -0,0 +1,37 @@
+package com.baeldung
+
+class Person {
+    private String firstname
+    private String lastname
+    private Integer age
+
+    Person(String firstname, String lastname, Integer age) {
+        this.firstname = firstname
+        this.lastname = lastname
+        this.age = age
+    }
+
+    String getFirstname() {
+        return firstname
+    }
+
+    void setFirstname(String firstname) {
+        this.firstname = firstname
+    }
+
+    String getLastname() {
+        return lastname
+    }
+
+    void setLastname(String lastname) {
+        this.lastname = lastname
+    }
+
+    Integer getAge() {
+        return age
+    }
+
+    void setAge(Integer age) {
+        this.age = age
+    }
+}
--- a/core-groovy/src/main/groovy/com/baeldung/closures/Closures.groovy
+++ b/core-groovy/src/main/groovy/com/baeldung/closures/Closures.groovy
@ -0,0 +1,87 @@
+package com.baeldung.closures
+
+class Closures {
+    
+    def printWelcome = {
+        println "Welcome to Closures!"
+    }
+    
+    def print = { name ->
+        println name
+    }
+    
+    def formatToLowerCase(name) {
+        return name.toLowerCase()
+    }
+    def formatToLowerCaseClosure = { name ->
+        return name.toLowerCase()
+    }
+    
+    def count=0
+    
+    def increaseCount = {
+        count++
+    }
+    
+    def greet = {
+        return "Hello! ${it}"
+    }
+   
+    def multiply = { x, y ->
+        return x*y
+    }
+    
+    def calculate = {int x, int y, String operation ->
+        
+        //log closure
+        def log = {
+            println "Performing $it"
+        }
+        
+        def result = 0    
+        switch(operation) {
+            case "ADD":
+                log("Addition")
+                result = x+y
+                break
+            case "SUB":
+                log("Subtraction")
+                result = x-y
+                break
+            case "MUL":
+                log("Multiplication")
+                result = x*y
+                break
+            case "DIV":
+                log("Division")
+                result = x/y
+                break
+        }
+        return result
+    }
+    
+    def addAll = { int... args ->
+        return args.sum()
+    }
+    
+    def volume(Closure areaCalculator, int... dimensions) {
+        if(dimensions.size() == 3) {
+            
+            //consider dimension[0] = length, dimension[1] = breadth, dimension[2] = height
+            //for cube and cuboid
+            return areaCalculator(dimensions[0], dimensions[1]) * dimensions[2]
+        } else if(dimensions.size() == 2) {
+            
+            //consider dimension[0] = radius, dimension[1] = height
+            //for cylinder and cone
+            return areaCalculator(dimensions[0]) * dimensions[1]
+        } else if(dimensions.size() == 1) {
+            
+            //consider dimension[0] = radius
+            //for sphere
+            return areaCalculator(dimensions[0]) * dimensions[0]
+        }
+        
+    }
+     
+}
--- a/core-groovy/src/main/groovy/com/baeldung/closures/Employee.groovy
+++ b/core-groovy/src/main/groovy/com/baeldung/closures/Employee.groovy
@ -0,0 +1,6 @@
+package com.baeldung.closures
+
+class Employee {
+    
+    String fullName
+}
--- a/core-groovy/src/main/groovy/com/baeldung/io/Task.groovy
+++ b/core-groovy/src/main/groovy/com/baeldung/io/Task.groovy
@ -0,0 +1,8 @@
+package com.baeldung.io
+
+class Task implements Serializable {
+    String description
+    Date startDate
+    Date dueDate
+    int status
+}
--- a/core-groovy/src/main/resources/binaryExample.jpg
+++ b/core-groovy/src/main/resources/binaryExample.jpg
--- a/core-groovy/src/main/resources/ioData.txt
+++ b/core-groovy/src/main/resources/ioData.txt
--- a/core-groovy/src/main/resources/ioInput.txt
+++ b/core-groovy/src/main/resources/ioInput.txt
@ -0,0 +1,4 @@
+First line of text
+Second line of text
+Third line of text
+Fourth line of text
--- a/core-groovy/src/main/resources/ioOutput.txt
+++ b/core-groovy/src/main/resources/ioOutput.txt
@ -0,0 +1,3 @@
+Line one of output example
+Line two of output example
+Line three of output example
--- a/core-groovy/src/main/resources/ioSerializedObject.txt
+++ b/core-groovy/src/main/resources/ioSerializedObject.txt
--- a/core-groovy/src/test/groovy/com/baeldung/closures/ClosuresUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/closures/ClosuresUnitTest.groovy
@ -0,0 +1,80 @@
+package com.baeldung.closures
+
+import spock.lang.Specification
+
+class ClosuresUnitTest extends GroovyTestCase {
+
+    Closures closures = new Closures()
+    
+    void testDeclaration() {
+        
+        closures.print("Hello! Closure")
+        closures.formatToLowerCaseClosure("Hello! Closure")
+        
+        closures.print.call("Hello! Closure")
+        closures.formatToLowerCaseClosure.call("Hello! Closure")
+        
+    }
+    
+    void testClosureVsMethods() {   
+        assert closures.formatToLowerCase("TONY STARK") == closures.formatToLowerCaseClosure("Tony STark")
+    }
+    
+    void testParameters() {
+        //implicit parameter
+        assert closures.greet("Alex") == "Hello! Alex"
+        
+        //multiple parameters
+        assert closures.multiply(2, 4) == 8
+        
+        assert closures.calculate(12, 4, "ADD") == 16
+        assert closures.calculate(12, 4, "SUB") == 8
+        assert closures.calculate(43, 8, "DIV") == 5.375
+                
+        //varags
+        assert closures.addAll(12, 10, 14) == 36
+       
+    }
+    
+    void testClosureAsAnArgument() {
+        assert closures.volume({ l, b -> return l*b }, 12, 6, 10) == 720
+        
+        assert closures.volume({ radius -> return Math.PI*radius*radius/3 }, 5, 10) == Math.PI * 250/3
+    }
+    
+    void testGStringsLazyEvaluation() {
+        def name = "Samwell"
+        def welcomeMsg = "Welcome! $name"
+        
+        assert welcomeMsg == "Welcome! Samwell"
+        
+        // changing the name does not affect original interpolated value
+        name = "Tarly"
+        assert welcomeMsg != "Welcome! Tarly"
+        
+        def fullName = "Tarly Samson"
+        def greetStr = "Hello! ${-> fullName}"
+        
+        assert greetStr == "Hello! Tarly Samson"
+
+        // this time changing the variable affects the interpolated String's value
+        fullName = "Jon Smith"
+        assert greetStr == "Hello! Jon Smith"
+    }
+    
+    void testClosureInLists() {
+        def list = [10, 11, 12, 13, 14, true, false, "BUNTHER"]
+        list.each {
+            println it
+        }
+        
+        assert [13, 14] == list.findAll{ it instanceof Integer && it >= 13}
+    }
+    
+    void testClosureInMaps() {
+        def map = [1:10, 2:30, 4:5]
+        
+        assert [10, 60, 20] == map.collect{it.key * it.value}
+    }
+    
+}
--- a/core-groovy/src/test/groovy/com/baeldung/io/DataAndObjectsUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/io/DataAndObjectsUnitTest.groovy
@ -0,0 +1,51 @@
+package com.baeldung.io
+
+import static org.junit.Assert.*
+
+import org.junit.Test
+
+class DataAndObjectsUnitTest {
+    @Test
+    void whenUsingWithDataOutputStream_thenDataIsSerializedToAFile() {
+        String message = 'This is a serialized string'
+        int length = message.length()
+        boolean valid = true
+        new File('src/main/resources/ioData.txt').withDataOutputStream { out ->
+            out.writeUTF(message)
+            out.writeInt(length)
+            out.writeBoolean(valid)
+        }
+
+        String loadedMessage = ""
+        int loadedLength
+        boolean loadedValid
+        
+        new File('src/main/resources/ioData.txt').withDataInputStream { is ->
+            loadedMessage = is.readUTF()
+            loadedLength = is.readInt()
+            loadedValid = is.readBoolean()
+        }
+        
+        assertEquals(message, loadedMessage)
+        assertEquals(length, loadedLength)
+        assertEquals(valid, loadedValid)
+    }
+
+    @Test
+    void whenUsingWithObjectOutputStream_thenObjectIsSerializedToFile() {
+        Task task = new Task(description:'Take out the trash', startDate:new Date(), status:0)
+        new File('src/main/resources/ioSerializedObject.txt').withObjectOutputStream { out ->
+            out.writeObject(task)
+        }
+
+        Task taskRead
+        
+        new File('src/main/resources/ioSerializedObject.txt').withObjectInputStream { is ->
+            taskRead = is.readObject()
+        }
+        
+        assertEquals(task.description, taskRead.description)
+        assertEquals(task.startDate, taskRead.startDate)
+        assertEquals(task.status, taskRead.status)
+    }
+}
--- a/core-groovy/src/test/groovy/com/baeldung/io/ReadExampleUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/io/ReadExampleUnitTest.groovy
@ -0,0 +1,134 @@
+package com.baeldung.io
+
+import static org.junit.Assert.*
+import org.junit.Test
+
+class ReadExampleUnitTest {
+
+    @Test
+    void whenUsingEachLine_thenCorrectLinesReturned() {
+        def expectedList = [
+            'First line of text', 
+            'Second line of text', 
+            'Third line of text', 
+            'Fourth line of text']
+
+        def lines = []
+
+        new File('src/main/resources/ioInput.txt').eachLine { line ->
+            lines.add(line)
+        }
+        assertEquals(expectedList, lines)
+    }
+
+    @Test
+    void whenUsingReadEachLineWithLineNumber_thenCorrectLinesReturned() {
+        def expectedList = [
+            'Second line of text', 
+            'Third line of text', 
+            'Fourth line of text']
+
+        def lineNoRange = 2..4
+        def lines = []
+
+        new File('src/main/resources/ioInput.txt').eachLine { line, lineNo ->
+            if (lineNoRange.contains(lineNo)) {
+                lines.add(line)
+            }
+        }
+        assertEquals(expectedList, lines)
+    }
+    
+    @Test
+    void whenUsingReadEachLineWithLineNumberStartAtZero_thenCorrectLinesReturned() {
+        def expectedList = [
+            'Second line of text',
+            'Third line of text',
+            'Fourth line of text']
+
+        def lineNoRange = 1..3
+        def lines = []
+
+        new File('src/main/resources/ioInput.txt').eachLine(0, { line, lineNo ->
+            if (lineNoRange.contains(lineNo)) {
+                lines.add(line)
+            }
+        })
+        assertEquals(expectedList, lines)
+    }
+
+    @Test
+    void whenUsingWithReader_thenLineCountReturned() {
+        def expectedCount = 4
+        def actualCount = 0
+        new File('src/main/resources/ioInput.txt').withReader { reader ->
+            while(reader.readLine()) {
+                actualCount++
+            }
+        }
+        assertEquals(expectedCount, actualCount)
+    }
+
+    @Test
+    void whenUsingNewReader_thenOutputFileCreated() {
+        def outputPath = 'src/main/resources/ioOut.txt'
+        def reader = new File('src/main/resources/ioInput.txt').newReader()
+        new File(outputPath).append(reader)
+        reader.close()
+        def ioOut = new File(outputPath)
+        assertTrue(ioOut.exists())
+        ioOut.delete()
+    }
+
+    @Test
+    void whenUsingWithInputStream_thenCorrectBytesAreReturned() {
+        def expectedLength = 1139
+        byte[] data = []
+        new File("src/main/resources/binaryExample.jpg").withInputStream { stream ->
+            data = stream.getBytes()
+        }
+        assertEquals(expectedLength, data.length)
+    }
+
+    @Test
+    void whenUsingNewInputStream_thenOutputFileCreated() {
+        def outputPath = 'src/main/resources/binaryOut.jpg'
+        def is = new File('src/main/resources/binaryExample.jpg').newInputStream()
+        new File(outputPath).append(is)
+        is.close()
+        def ioOut = new File(outputPath)
+        assertTrue(ioOut.exists())
+        ioOut.delete()
+    }
+
+    @Test
+    void whenUsingCollect_thenCorrectListIsReturned() {
+        def expectedList = ['First line of text', 'Second line of text', 'Third line of text', 'Fourth line of text']
+
+        def actualList = new File('src/main/resources/ioInput.txt').collect {it}
+        assertEquals(expectedList, actualList)
+    }
+
+    @Test
+    void whenUsingAsStringArray_thenCorrectArrayIsReturned() {
+        String[] expectedArray = ['First line of text', 'Second line of text', 'Third line of text', 'Fourth line of text']
+
+        def actualArray = new File('src/main/resources/ioInput.txt') as String[]
+        assertArrayEquals(expectedArray, actualArray)
+    }
+
+    @Test
+    void whenUsingText_thenCorrectStringIsReturned() {
+        def ln = System.getProperty('line.separator')
+        def expectedString = "First line of text${ln}Second line of text${ln}Third line of text${ln}Fourth line of text"
+        def actualString = new File('src/main/resources/ioInput.txt').text
+        assertEquals(expectedString.toString(), actualString)
+    }
+
+    @Test
+    void whenUsingBytes_thenByteArrayIsReturned() {
+        def expectedLength = 1139
+        def contents = new File('src/main/resources/binaryExample.jpg').bytes
+        assertEquals(expectedLength, contents.length)
+    }
+}
--- a/core-groovy/src/test/groovy/com/baeldung/io/TraverseFileTreeUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/io/TraverseFileTreeUnitTest.groovy
@ -0,0 +1,61 @@
+package com.baeldung.io
+
+import org.junit.Test
+
+import groovy.io.FileType
+import groovy.io.FileVisitResult
+
+class TraverseFileTreeUnitTest {
+    @Test
+    void whenUsingEachFile_filesAreListed() {
+        new File('src/main/resources').eachFile { file ->
+            println file.name
+        }
+    }
+    
+    @Test(expected = IllegalArgumentException)
+    void whenUsingEachFileOnAFile_anErrorOccurs() {
+        new File('src/main/resources/ioInput.txt').eachFile { file ->
+            println file.name
+        }
+    }
+    
+    @Test
+    void whenUsingEachFileMatch_filesAreListed() {
+        new File('src/main/resources').eachFileMatch(~/io.*\.txt/) { file ->
+            println file.name
+        }
+    }
+    
+    @Test
+    void whenUsingEachFileRecurse_thenFilesInSubfoldersAreListed() {
+        new File('src/main').eachFileRecurse(FileType.FILES) { file ->
+            println "$file.parent $file.name"
+        }
+    }
+    
+    @Test
+    void whenUsingEachFileRecurse_thenDirsInSubfoldersAreListed() {
+        new File('src/main').eachFileRecurse(FileType.DIRECTORIES) { file ->
+            println "$file.parent $file.name"
+        }
+    }
+    
+    @Test
+    void whenUsingEachDirRecurse_thenDirsAndSubDirsAreListed() {
+        new File('src/main').eachDirRecurse { dir ->
+            println "$dir.parent $dir.name"
+        }
+    }
+    
+    @Test
+    void whenUsingTraverse_thenDirectoryIsTraversed() {
+        new File('src/main').traverse { file ->
+            if (file.directory && file.name == 'groovy') {
+                FileVisitResult.SKIP_SUBTREE
+            } else {
+                println "$file.parent - $file.name"
+            }
+        }
+    }
+}
--- a/core-groovy/src/test/groovy/com/baeldung/io/WriteExampleUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/io/WriteExampleUnitTest.groovy
@ -0,0 +1,96 @@
+package com.baeldung.io
+
+import static org.junit.Assert.*
+
+import org.junit.Before
+import org.junit.Test
+
+class WriteExampleUnitTest {
+    @Before
+    void clearOutputFile() {
+        new File('src/main/resources/ioOutput.txt').text = ''
+        new File('src/main/resources/ioBinaryOutput.bin').delete()
+    }
+    
+    @Test
+    void whenUsingWithWriter_thenFileCreated() {
+        def outputLines = [
+            'Line one of output example',
+            'Line two of output example',
+            'Line three of output example'
+        ]
+        
+        def outputFileName = 'src/main/resources/ioOutput.txt'
+        new File(outputFileName).withWriter { writer ->
+            outputLines.each { line ->
+                writer.writeLine line
+            }
+        }
+        def writtenLines = new File(outputFileName).collect {it}
+        assertEquals(outputLines, writtenLines)
+    }
+    
+    @Test
+    void whenUsingNewWriter_thenFileCreated() {
+        def outputLines = [
+            'Line one of output example',
+            'Line two of output example',
+            'Line three of output example'
+        ]
+        
+        def outputFileName = 'src/main/resources/ioOutput.txt'
+        def writer = new File(outputFileName).newWriter()
+        outputLines.forEach {line ->
+            writer.writeLine line
+        }
+        writer.flush()
+        writer.close()
+        
+        def writtenLines = new File(outputFileName).collect {it}
+        assertEquals(outputLines, writtenLines)
+    }
+    
+    @Test
+    void whenUsingDoubleLessThanOperator_thenFileCreated() {
+        def outputLines = [
+            'Line one of output example',
+            'Line two of output example',
+            'Line three of output example'
+        ]
+        
+        def ln = System.getProperty('line.separator')
+        def outputFileName = 'src/main/resources/ioOutput.txt'
+        new File(outputFileName) << "Line one of output example${ln}Line two of output example${ln}Line three of output example"
+        def writtenLines = new File(outputFileName).collect {it}
+        assertEquals(outputLines.size(), writtenLines.size())
+    }
+    
+    @Test
+    void whenUsingBytes_thenBinaryFileCreated() {
+        def outputFileName = 'src/main/resources/ioBinaryOutput.bin'
+        def outputFile = new File(outputFileName)
+        byte[] outBytes = [44, 88, 22]
+        outputFile.bytes = outBytes
+        assertEquals(3, new File(outputFileName).size())
+    }
+    
+    @Test
+    void whenUsingWithOutputStream_thenBinaryFileCreated() {
+        def outputFileName = 'src/main/resources/ioBinaryOutput.bin'
+        byte[] outBytes = [44, 88, 22]
+        new File(outputFileName).withOutputStream { stream ->
+            stream.write(outBytes)
+        }
+        assertEquals(3, new File(outputFileName).size())
+    }
+    
+    @Test
+    void whenUsingNewOutputStream_thenBinaryFileCreated() {
+        def outputFileName = 'src/main/resources/ioBinaryOutput.bin'
+        byte[] outBytes = [44, 88, 22]
+        def os = new File(outputFileName).newOutputStream()
+        os.write(outBytes)
+        os.close()
+        assertEquals(3, new File(outputFileName).size())
+    }
+}
--- a/core-groovy/src/test/groovy/com/baeldung/lists/ListTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/lists/ListTest.groovy
@ -0,0 +1,173 @@
+package com.baeldung.groovy.lists
+
+import static groovy.test.GroovyAssert.*
+import org.junit.Test
+
+class ListTest{
+
+    @Test
+    void testCreateList() {
+
+        def list = [1, 2, 3]
+        assertNotNull(list)
+
+        def listMix = ['A', "b", 1, true]
+        assertTrue(listMix == ['A', "b", 1, true])
+
+        def linkedList = [1, 2, 3] as LinkedList
+        assertTrue(linkedList instanceof LinkedList)
+
+        ArrayList arrList = [1, 2, 3]
+        assertTrue(arrList.class == ArrayList)
+
+        def copyList = new ArrayList(arrList)
+        assertTrue(copyList == arrList)
+
+        def cloneList = arrList.clone()
+        assertTrue(cloneList == arrList)
+    }
+
+    @Test
+    void testCreateEmptyList() {
+
+        def emptyList = []
+        assertTrue(emptyList.size() == 0)
+    }
+
+    @Test
+    void testCompareTwoLists() {
+
+        def list1 = [5, 6.0, 'p']
+        def list2 = [5, 6.0, 'p']
+        assertTrue(list1 == list2)
+    }
+
+    @Test
+    void testGetItemsFromList(){
+
+        def list = ["Hello", "World"]
+
+        assertTrue(list.get(1) == "World")
+        assertTrue(list[1] == "World")
+        assertTrue(list[-1] == "World")
+        assertTrue(list.getAt(1) == "World")
+        assertTrue(list.getAt(-2) == "Hello")
+    }
+
+    @Test
+    void testAddItemsToList() {
+
+        def list = []
+
+        list << 1
+        list.add("Apple")
+        assertTrue(list == [1, "Apple"])
+
+        list[2] = "Box"
+        list[4] = true
+        assertTrue(list == [1, "Apple", "Box", null, true])
+
+        list.add(1, 6.0)
+        assertTrue(list == [1, 6.0, "Apple", "Box", null, true])
+
+        def list2 = [1, 2]
+        list += list2
+        list += 12
+        assertTrue(list == [1, 6.0, "Apple", "Box", null, true, 1, 2, 12])
+    }
+
+    @Test
+    void testUpdateItemsInList() {
+
+        def list =[1, "Apple", 80, "App"]
+        list[1] = "Box"
+        list.set(2,90)
+        assertTrue(list == [1, "Box", 90, "App"])
+    }
+
+    @Test
+    void testRemoveItemsFromList(){
+
+        def list = [1, 2, 3, 4, 5, 5, 6, 6, 7]
+
+        list.remove(3)
+        assertTrue(list == [1, 2, 3, 5, 5, 6, 6, 7])
+
+        list.removeElement(5)
+        assertTrue(list == [1, 2, 3, 5, 6, 6, 7])
+
+        assertTrue(list - 6 == [1, 2, 3, 5, 7])
+    }
+
+    @Test
+    void testIteratingOnAList(){
+
+        def list = [1, "App", 3, 4]
+        list.each{ println it * 2}
+
+        list.eachWithIndex{ it, i -> println "$i : $it" }
+    }
+
+    @Test
+    void testCollectingToAnotherList(){
+
+        def list = ["Kay", "Henry", "Justin", "Tom"]
+        assertTrue(list.collect{"Hi " + it} == ["Hi Kay", "Hi Henry", "Hi Justin", "Hi Tom"])
+    }
+
+    @Test
+    void testJoinItemsInAList(){
+        assertTrue(["One", "Two", "Three"].join(",") == "One,Two,Three")
+    }
+
+    @Test
+    void testFilteringOnLists(){
+        def filterList = [2, 1, 3, 4, 5, 6, 76]
+
+        assertTrue(filterList.find{it > 3} == 4)
+
+        assertTrue(filterList.findAll{it > 3} == [4, 5, 6, 76])
+
+        assertTrue(filterList.findAll{ it instanceof Number} == [2, 1, 3, 4, 5, 6, 76])
+
+        assertTrue(filterList.grep( Number )== [2, 1, 3, 4, 5, 6, 76])
+
+        assertTrue(filterList.grep{ it> 6 }== [76])
+
+        def conditionList = [2, 1, 3, 4, 5, 6, 76]
+
+        assertFalse(conditionList.every{ it < 6})
+
+        assertTrue(conditionList.any{ it%2 == 0})
+
+    }
+
+    @Test
+    void testGetUniqueItemsInAList(){
+        assertTrue([1, 3, 3, 4].toUnique() == [1, 3, 4])
+
+        def uniqueList = [1, 3, 3, 4]
+        uniqueList.unique()
+        assertTrue(uniqueList == [1, 3, 4])
+
+        assertTrue(["A", "B", "Ba", "Bat", "Cat"].toUnique{ it.size()} == ["A", "Ba", "Bat"])
+    }
+
+    @Test
+    void testSorting(){
+
+        assertTrue([1, 2, 1, 0].sort() == [0, 1, 1, 2])
+        Comparator mc = {a,b -> a == b? 0: a < b? 1 : -1}
+
+        def list = [1, 2, 1, 0]
+        list.sort(mc)
+        assertTrue(list == [2, 1, 1, 0])
+
+        def strList = ["na", "ppp", "as"]
+        assertTrue(strList.max() == "ppp")
+
+        Comparator minc = {a,b -> a == b? 0: a < b? -1 : 1}
+        def numberList = [3, 2, 0, 7]
+        assertTrue(numberList.min(minc) == 0)
+    }
+}
--- a/core-groovy/src/test/groovy/com/baeldung/lists/ListUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/lists/ListUnitTest.groovy
@ -0,0 +1,58 @@
+package com.baeldung.lists
+
+import com.baeldung.Person
+import org.junit.Test
+
+import static org.junit.Assert.*
+
+class ListUnitTest {
+
+    private final personList = [
+      new Person("Regina", "Fitzpatrick", 25),
+      new Person("Abagail", "Ballard", 26),
+      new Person("Lucian", "Walter", 30),
+    ]
+
+    @Test
+    void whenListContainsElement_thenCheckReturnsTrue() {
+        def list = ['a', 'b', 'c']
+
+        assertTrue(list.indexOf('a') > -1)
+        assertTrue(list.contains('a'))
+    }
+
+    @Test
+    void whenListContainsElement_thenCheckWithMembershipOperatorReturnsTrue() {
+        def list = ['a', 'b', 'c']
+
+        assertTrue('a' in list)
+    }
+
+    @Test
+    void givenListOfPerson_whenUsingStreamMatching_thenShouldEvaluateList() {
+        assertTrue(personList.stream().anyMatch {it.age > 20})
+        assertFalse(personList.stream().allMatch {it.age < 30})
+    }
+
+    @Test
+    void givenListOfPerson_whenUsingCollectionMatching_thenShouldEvaluateList() {
+        assertTrue(personList.any {it.age > 20})
+        assertFalse(personList.every {it.age < 30})
+    }
+
+    @Test
+    void givenListOfPerson_whenUsingStreamFind_thenShouldReturnMatchingElements() {
+        assertTrue(personList.stream().filter {it.age > 20}.findAny().isPresent())
+        assertFalse(personList.stream().filter {it.age > 30}.findAny().isPresent())
+        assertTrue(personList.stream().filter {it.age > 20}.findAll().size() == 3)
+        assertTrue(personList.stream().filter {it.age > 30}.findAll().isEmpty())
+    }
+
+    @Test
+    void givenListOfPerson_whenUsingCollectionFind_thenShouldReturnMatchingElements() {
+        assertNotNull(personList.find {it.age > 20})
+        assertNull(personList.find {it.age > 30})
+        assertTrue(personList.findAll {it.age > 20}.size() == 3)
+        assertTrue(personList.findAll {it.age > 30}.isEmpty())
+    }
+}
--- a/core-groovy/src/test/groovy/com/baeldung/map/MapUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/map/MapUnitTest.groovy
@ -1,10 +1,18 @@
 package com.baeldung.map

-import static org.junit.Assert.*
+import com.baeldung.Person
 import org.junit.Test

+import static org.junit.Assert.*
+
 class MapUnitTest {

+    private final personMap = [
+      Regina : new Person("Regina", "Fitzpatrick", 25),
+      Abagail: new Person("Abagail", "Ballard", 26),
+      Lucian : new Person("Lucian", "Walter", 30)
+    ]
+
    @Test
    void whenUsingEach_thenMapIsIterated() {
        def map = [
@ -82,4 +90,65 @@ class MapUnitTest {
            println "Hex Code: $entry.key = Color Name: $entry.value"
        }
    }
+
+    @Test
+    void whenMapContainsKeyElement_thenCheckReturnsTrue() {
+        def map = [a: 'd', b: 'e', c: 'f']
+
+        assertTrue(map.containsKey('a'))
+        assertFalse(map.containsKey('e'))
+        assertTrue(map.containsValue('e'))
+    }
+
+    @Test
+    void whenMapContainsKeyElement_thenCheckByMembershipReturnsTrue() {
+        def map = [a: 'd', b: 'e', c: 'f']
+
+        assertTrue('a' in map)
+        assertFalse('f' in map)
+    }
+
+    @Test
+    void whenMapContainsFalseBooleanValues_thenCheckReturnsFalse() {
+        def map = [a: true, b: false, c: null]
+
+        assertTrue(map.containsKey('b'))
+        assertTrue('a' in map)
+        assertFalse('b' in map)
+        assertFalse('c' in map)
+    }
+
+    @Test
+    void givenMapOfPerson_whenUsingStreamMatching_thenShouldEvaluateMap() {
+        assertTrue(personMap.keySet().stream().anyMatch {it == "Regina"})
+        assertFalse(personMap.keySet().stream().allMatch {it == "Albert"})
+        assertFalse(personMap.values().stream().allMatch {it.age < 30})
+        assertTrue(personMap.entrySet().stream().anyMatch {it.key == "Abagail" && it.value.lastname == "Ballard"})
+    }
+
+    @Test
+    void givenMapOfPerson_whenUsingCollectionMatching_thenShouldEvaluateMap() {
+        assertTrue(personMap.keySet().any {it == "Regina"})
+        assertFalse(personMap.keySet().every {it == "Albert"})
+        assertFalse(personMap.values().every {it.age < 30})
+        assertTrue(personMap.any {firstname, person -> firstname == "Abagail" && person.lastname == "Ballard"})
+    }
+
+    @Test
+    void givenMapOfPerson_whenUsingCollectionFind_thenShouldReturnElements() {
+        assertNotNull(personMap.find {it.key == "Abagail" && it.value.lastname == "Ballard"})
+        assertTrue(personMap.findAll {it.value.age > 20}.size() == 3)
+    }
+
+    @Test
+    void givenMapOfPerson_whenUsingStreamFind_thenShouldReturnElements() {
+        assertTrue(
+          personMap.entrySet().stream()
+            .filter {it.key == "Abagail" && it.value.lastname == "Ballard"}
+            .findAny().isPresent())
+        assertTrue(
+          personMap.entrySet().stream()
+            .filter {it.value.age > 20}
+            .findAll().size() == 3)
+    }
 }
--- a/core-groovy/src/test/groovy/com/baeldung/set/SetUnitTest.groovy
+++ b/core-groovy/src/test/groovy/com/baeldung/set/SetUnitTest.groovy
@ -0,0 +1,16 @@
+package com.baeldung.set
+
+import org.junit.Test
+
+import static org.junit.Assert.assertTrue
+
+class SetUnitTest {
+
+    @Test
+    void whenSetContainsElement_thenCheckReturnsTrue() {
+        def set = ['a', 'b', 'c'] as Set
+
+        assertTrue(set.contains('a'))
+        assertTrue('a' in set)
+    }
+}
--- a/core-java-11/README.md
+++ b/core-java-11/README.md
@ -4,4 +4,6 @@
 - [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)
+- [Exploring the New HTTP Client in Java 9 and 11](https://www.baeldung.com/java-9-http-client)
+- [An Introduction to Epsilon GC: A No-Op Experimental Garbage Collector](https://www.baeldung.com/jvm-epsilon-gc-garbage-collector)
 - [Guide to jlink](https://www.baeldung.com/jlink)
--- a/core-java-11/pom.xml
+++ b/core-java-11/pom.xml
@ -14,6 +14,14 @@
        <version>1.0.0-SNAPSHOT</version>
    </parent>

+    <dependencies>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+    </dependencies>
+
    <build>
        <plugins>
            <plugin>
@ -31,6 +39,7 @@
    <properties>
        <maven.compiler.source.version>11</maven.compiler.source.version>
        <maven.compiler.target.version>11</maven.compiler.target.version>
+        <guava.version>27.1-jre</guava.version>
    </properties>

 </project>
--- a/core-java-11/src/modules/jlinkModule/com/baeldung/jlink/HelloWorld.java
+++ b/core-java-11/src/modules/jlinkModule/com/baeldung/jlink/HelloWorld.java
@ -0,0 +1,12 @@
+package com.baeldung.jlink;
+
+import java.util.logging.Logger;
+
+public class HelloWorld {
+
+    private static final Logger LOG = Logger.getLogger(HelloWorld.class.getName());
+
+    public static void main(String[] args) {
+        LOG.info("Hello World!");
+    }
+}
--- a/core-java-11/src/modules/jlinkModule/module-info.java
+++ b/core-java-11/src/modules/jlinkModule/module-info.java
@ -0,0 +1,3 @@
+module jlinkModule {
+    requires java.logging;
+}
--- a/core-java-11/src/test/java/com/baeldung/EmptyStringToEmptyOptionalUnitTest.java
+++ b/core-java-11/src/test/java/com/baeldung/EmptyStringToEmptyOptionalUnitTest.java
@ -0,0 +1,32 @@
+package com.baeldung;
+
+import com.google.common.base.Strings;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Optional;
+import java.util.function.Predicate;
+
+public class EmptyStringToEmptyOptionalUnitTest {
+
+    @Test
+    public void givenEmptyString_whenFilteringOnOptional_thenEmptyOptionalIsReturned() {
+        String str = "";
+        Optional<String> opt = Optional.ofNullable(str).filter(s -> !s.isEmpty());
+        Assert.assertFalse(opt.isPresent());
+    }
+
+    @Test
+    public void givenEmptyString_whenFilteringOnOptionalInJava11_thenEmptyOptionalIsReturned() {
+        String str = "";
+        Optional<String> opt = Optional.ofNullable(str).filter(Predicate.not(String::isEmpty));
+        Assert.assertFalse(opt.isPresent());
+    }
+
+    @Test
+    public void givenEmptyString_whenPassingResultOfEmptyToNullToOfNullable_thenEmptyOptionalIsReturned() {
+        String str = "";
+        Optional<String> opt = Optional.ofNullable(Strings.emptyToNull(str));
+        Assert.assertFalse(opt.isPresent());
+    }
+}
--- a/core-java-12/pom.xml
+++ b/core-java-12/pom.xml
@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-12</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-12</name>
+    <packaging>jar</packaging>
+    <url>http://maven.apache.org</url>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source.version}</source>
+                    <target>${maven.compiler.target.version}</target>
+                    <compilerArgs>--enable-preview</compilerArgs>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source.version>12</maven.compiler.source.version>
+        <maven.compiler.target.version>12</maven.compiler.target.version>
+        <assertj.version>3.6.1</assertj.version>
+    </properties>
+
+</project>
--- a/core-java-12/src/test/java/com/baeldung/collectors/CollectorsUnitTest.java
+++ b/core-java-12/src/test/java/com/baeldung/collectors/CollectorsUnitTest.java
@ -0,0 +1,71 @@
+package com.baeldung.collectors;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+
+import org.junit.Test;
+
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.minBy;
+import static java.util.stream.Collectors.teeing;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for collectors additions in Java 12.
+ */
+public class CollectorsUnitTest {
+
+    @Test
+    public void whenTeeing_ItShouldCombineTheResultsAsExpected() {
+        List<Integer> numbers = Arrays.asList(42, 4, 2, 24);
+        Range range = numbers.stream()
+            .collect(teeing(minBy(Integer::compareTo), maxBy(Integer::compareTo), (min, max) -> new Range(min.orElse(null), max.orElse(null))));
+
+        assertThat(range).isEqualTo(new Range(2, 42));
+    }
+
+    /**
+     * Represents a closed range of numbers between {@link #min} and
+     * {@link #max}, both inclusive.
+     */
+    private static class Range {
+
+        private final Integer min;
+
+        private final Integer max;
+
+        Range(Integer min, Integer max) {
+            this.min = min;
+            this.max = max;
+        }
+
+        Integer getMin() {
+            return min;
+        }
+
+        Integer getMax() {
+            return max;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o)
+                return true;
+            if (o == null || getClass() != o.getClass())
+                return false;
+            Range range = (Range) o;
+            return Objects.equals(getMin(), range.getMin()) && Objects.equals(getMax(), range.getMax());
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(getMin(), getMax());
+        }
+
+        @Override
+        public String toString() {
+            return "Range{" + "min=" + min + ", max=" + max + '}';
+        }
+    }
+}
--- a/core-java-12/src/test/java/com/baeldung/switchExpression/SwitchUnitTest.java
+++ b/core-java-12/src/test/java/com/baeldung/switchExpression/SwitchUnitTest.java
@ -0,0 +1,37 @@
+package com.baeldung.switchExpression;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class SwitchUnitTest {
+
+    @Test
+    public void switchJava12(){
+
+        var month = Month.AUG;
+
+        var value = switch(month){
+            case JAN,JUN, JUL -> 3;
+            case FEB,SEP, OCT, NOV, DEC -> 1;
+            case MAR,MAY, APR, AUG -> 2;
+        };
+
+        Assert.assertEquals(value, 2);
+    }
+
+    @Test
+    public void switchLocalVariable(){
+        var month = Month.AUG;
+        int i = switch (month){
+            case JAN,JUN, JUL -> 3;
+            case FEB,SEP, OCT, NOV, DEC -> 1;
+            case MAR,MAY, APR, AUG -> {
+                int j = month.toString().length() * 4;
+                break j;
+            }
+        };
+        Assert.assertEquals(12, i);
+    }
+
+    enum Month {JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC}
+}
--- a/core-java-8-2/README.md
+++ b/core-java-8-2/README.md
@ -0,0 +1,6 @@
+=========
+
+## Core Java 8 Cookbooks and Examples (part 2)
+
+### Relevant Articles: 
+- [Anonymous Classes in Java](http://www.baeldung.com/)
--- a/core-java-8-2/pom.xml
+++ b/core-java-8-2/pom.xml
@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-8-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-8-2</name>
+    <packaging>jar</packaging>
+
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+
+    </build>
+</project>
--- a/core-java-8-2/src/main/java/com/baeldung/anonymous/Book.java
+++ b/core-java-8-2/src/main/java/com/baeldung/anonymous/Book.java
@ -0,0 +1,15 @@
+package com.baeldung.anonymous;
+
+public class Book {
+
+    final String title;
+    
+    public Book(String title) {
+        this.title = title;
+    }
+    
+    public String description() {
+        return "Title: " + title;
+    }
+
+}
--- a/core-java-8-2/src/main/java/com/baeldung/anonymous/Main.java
+++ b/core-java-8-2/src/main/java/com/baeldung/anonymous/Main.java
@ -0,0 +1,64 @@
+package com.baeldung.anonymous;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Code snippet that illustrates the usage of anonymous classes.
+ * 
+ * Note that use of Runnable instances in this example does not demonstrate their
+ * common use.
+ * 
+ * @author A. Shcherbakov
+ *
+ */
+public class Main {
+
+    public static void main(String[] args) {
+        final List<Runnable> actions = new ArrayList<Runnable>(2);
+
+        Runnable action = new Runnable() {
+            @Override
+            public void run() {
+                System.out.println("Hello from runnable.");
+            }
+
+        };
+        actions.add(action);
+
+        Book book = new Book("Design Patterns") {
+            @Override
+            public String description() {
+                return "Famous GoF book.";
+            }
+        };
+
+        System.out.println(String.format("Title: %s, description: %s", book.title, book.description()));
+
+        actions.add(new Runnable() {
+            @Override
+            public void run() {
+                System.out.println("Hello from runnable #2.");
+
+            }
+        });
+
+        int count = 1;
+
+        Runnable action2 = new Runnable() {
+            static final int x = 0;
+            // static int y = 0;
+
+            @Override
+            public void run() {
+                System.out.println(String.format("Runnable with captured variables: count = %s, x = %s", count, x));
+            }
+        };
+        actions.add(action2);
+
+        for (Runnable a : actions) {
+            a.run();
+        }
+    }
+
+}
--- a/core-java-8-2/src/test/java/com/baeldung/UnitTest.java
+++ b/core-java-8-2/src/test/java/com/baeldung/UnitTest.java
@ -0,0 +1,18 @@
+package com.baeldung;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/**
+ * Unit test for simple App.
+ */
+public class UnitTest {
+    /**
+     * Stub test
+     */
+    @Test
+    public void givenPreconditions_whenCondition_shouldResult() {
+        assertTrue(true);
+    }
+}
--- a/core-java-8/README.md
+++ b/core-java-8/README.md
@ -3,10 +3,10 @@
 ## Core Java 8 Cookbooks and Examples

 ### Relevant Articles: 
- [Java 8 Collectors](http://www.baeldung.com/java-8-collectors)
- [Guide to Java 8’s Functional Interfaces](http://www.baeldung.com/java-8-functional-interfaces)
+- [Guide to Java 8’s Collectors](http://www.baeldung.com/java-8-collectors)
+- [Functional Interfaces in Java 8](http://www.baeldung.com/java-8-functional-interfaces)
 - [Java 8 – Powerful Comparison with Lambdas](http://www.baeldung.com/java-8-sort-lambda)
- [Java 8 New Features](http://www.baeldung.com/java-8-new-features)
+- [New Features in Java 8](http://www.baeldung.com/java-8-new-features)
 - [Lambda Expressions and Functional Interfaces: Tips and Best Practices](http://www.baeldung.com/java-8-lambda-expressions-tips)
 - [The Double Colon Operator in Java 8](http://www.baeldung.com/java-8-double-colon-operator)
 - [Guide to Java 8 groupingBy Collector](http://www.baeldung.com/java-groupingby-collector)
@ -39,3 +39,4 @@
 - [Java @Deprecated Annotation](https://www.baeldung.com/java-deprecated)
 - [Java 8 Predicate Chain](https://www.baeldung.com/java-predicate-chain)
 - [Method References in Java](https://www.baeldung.com/java-method-references)
+- [Creating a Custom Annotation in Java](https://www.baeldung.com/java-custom-annotation)
--- a/core-java-8/src/main/java/com/baeldung/Adder.java
+++ b/core-java-8/src/main/java/com/baeldung/Adder.java
@ -1,12 +0,0 @@
-package com.baeldung;
-
-import java.util.function.Consumer;
-import java.util.function.Function;
-
-public interface Adder {
-
-    String addWithFunction(Function<String, String> f);
-
-    void addWithConsumer(Consumer<Integer> f);
-
-}
--- a/core-java-8/src/main/java/com/baeldung/AdderImpl.java
+++ b/core-java-8/src/main/java/com/baeldung/AdderImpl.java
@ -1,18 +0,0 @@
-package com.baeldung;
-
-
-import java.util.function.Consumer;
-import java.util.function.Function;
-
-public class AdderImpl implements Adder {
-
-    @Override
-    public String addWithFunction(final Function<String, String> f) {
-        return f.apply("Something ");
-    }
-
-    @Override
-    public void addWithConsumer(final Consumer<Integer> f) {
-    }
-
-}
--- a/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Bar.java
+++ b/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Bar.java
@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.java8.lambda.tips;


@FunctionalInterface
--- a/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Baz.java
+++ b/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Baz.java
@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.java8.lambda.tips;


@FunctionalInterface
--- a/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Foo.java
+++ b/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Foo.java
@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.java8.lambda.tips;


@FunctionalInterface
--- a/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/FooExtended.java
+++ b/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/FooExtended.java
@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.java8.lambda.tips;


@FunctionalInterface
--- a/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Processor.java
+++ b/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/Processor.java
@ -0,0 +1,12 @@
+package com.baeldung.java8.lambda.tips;
+
+import java.util.concurrent.Callable;
+import java.util.function.Supplier;
+
+public interface Processor {
+
+    String processWithCallable(Callable<String> c) throws Exception;
+
+    String processWithSupplier(Supplier<String> s);
+
+}
--- a/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/ProcessorImpl.java
+++ b/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/ProcessorImpl.java
@ -0,0 +1,20 @@
+package com.baeldung.java8.lambda.tips;
+
+
+import java.util.concurrent.Callable;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public class ProcessorImpl implements Processor {
+
+    @Override
+    public String processWithCallable(Callable<String> c) throws Exception {
+        return c.call();
+    }
+
+    @Override
+    public String processWithSupplier(Supplier<String> s) {
+        return s.get();
+    }
+}
--- a/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/UseFoo.java
+++ b/core-java-8/src/main/java/com/baeldung/java8/lambda/tips/UseFoo.java
@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.java8.lambda.tips;


 import java.util.function.Function;
--- a/core-java-8/src/test/java/com/baeldung/java8/Java8SortUnitTest.java
+++ b/core-java-8/src/test/java/com/baeldung/java8/Java8SortUnitTest.java
@ -124,11 +124,44 @@ public class Java8SortUnitTest {

    @Test
    public final void givenStreamCustomOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
-        
        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
        final Comparator<Human> nameComparator = (h1, h2) -> h1.getName().compareTo(h2.getName());
        
        final List<Human> sortedHumans = humans.stream().sorted(nameComparator).collect(Collectors.toList());
        Assert.assertThat(sortedHumans.get(0), equalTo(new Human("Jack", 12)));
    }
+
+    @Test
+    public final void givenStreamComparatorOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+
+        final List<Human> sortedHumans = humans.stream().sorted(Comparator.comparing(Human::getName)).collect(Collectors.toList());
+        Assert.assertThat(sortedHumans.get(0), equalTo(new Human("Jack", 12)));
+    }
+
+    @Test
+    public final void givenStreamNaturalOrdering_whenSortingEntitiesByNameReversed_thenCorrectlySorted() {
+        final List<String> letters = Lists.newArrayList("B", "A", "C");
+
+        final List<String> reverseSortedLetters = letters.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
+        Assert.assertThat(reverseSortedLetters.get(0), equalTo("C"));
+    }
+
+    @Test
+    public final void givenStreamCustomOrdering_whenSortingEntitiesByNameReversed_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+        final Comparator<Human> reverseNameComparator = (h1, h2) -> h2.getName().compareTo(h1.getName());
+
+        final List<Human> reverseSortedHumans = humans.stream().sorted(reverseNameComparator).collect(Collectors.toList());
+        Assert.assertThat(reverseSortedHumans.get(0), equalTo(new Human("Sarah", 10)));
+    }
+
+    @Test
+    public final void givenStreamComparatorOrdering_whenSortingEntitiesByNameReversed_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+
+        final List<Human> reverseSortedHumans = humans.stream().sorted(Comparator.comparing(Human::getName, Comparator.reverseOrder())).collect(Collectors.toList());
+        Assert.assertThat(reverseSortedHumans.get(0), equalTo(new Human("Sarah", 10)));
+    }
+
 }
--- a/core-java-8/src/test/java/com/baeldung/java8/lambda/tips/Java8FunctionalInteracesLambdasUnitTest.java
+++ b/core-java-8/src/test/java/com/baeldung/java8/lambda/tips/Java8FunctionalInteracesLambdasUnitTest.java
@ -1,8 +1,8 @@
-package com.baeldung.java8;
+package com.baeldung.java8.lambda.tips;

-import com.baeldung.Foo;
-import com.baeldung.FooExtended;
-import com.baeldung.UseFoo;
+import com.baeldung.java8.lambda.tips.Foo;
+import com.baeldung.java8.lambda.tips.FooExtended;
+import com.baeldung.java8.lambda.tips.UseFoo;
 import org.junit.Before;
 import org.junit.Test;

--- a/core-java-8/src/test/java/com/baeldung/java8/optional/OptionalChainingUnitTest.java
+++ b/core-java-8/src/test/java/com/baeldung/java8/optional/OptionalChainingUnitTest.java
@ -0,0 +1,110 @@
+package com.baeldung.java8.optional;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Optional;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.*;
+
+public class OptionalChainingUnitTest {
+
+    private boolean getEmptyEvaluated;
+    private boolean getHelloEvaluated;
+    private boolean getByeEvaluated;
+
+    @Before
+    public void setUp() {
+        getEmptyEvaluated = false;
+        getHelloEvaluated = false;
+        getByeEvaluated = false;
+    }
+
+    @Test
+    public void givenThreeOptionals_whenChaining_thenFirstNonEmptyIsReturned() {
+        Optional<String> found = Stream.of(getEmpty(), getHello(), getBye())
+                .filter(Optional::isPresent)
+                .map(Optional::get)
+                .findFirst();
+
+        assertEquals(getHello(), found);
+    }
+
+    @Test
+    public void givenTwoEmptyOptionals_whenChaining_thenEmptyOptionalIsReturned() {
+        Optional<String> found = Stream.of(getEmpty(), getEmpty())
+                .filter(Optional::isPresent)
+                .map(Optional::get)
+                .findFirst();
+
+        assertFalse(found.isPresent());
+    }
+
+    @Test
+    public void givenTwoEmptyOptionals_whenChaining_thenDefaultIsReturned() {
+        String found = Stream.<Supplier<Optional<String>>>of(
+                () -> createOptional("empty"),
+                () -> createOptional("empty")
+        )
+                .map(Supplier::get)
+                .filter(Optional::isPresent)
+                .map(Optional::get)
+                .findFirst()
+                .orElseGet(() -> "default");
+
+        assertEquals("default", found);
+    }
+
+    @Test
+    public void givenThreeOptionals_whenChaining_thenFirstNonEmptyIsReturnedAndRestNotEvaluated() {
+        Optional<String> found = Stream.<Supplier<Optional<String>>>of(this::getEmpty, this::getHello, this::getBye)
+                .map(Supplier::get)
+                .filter(Optional::isPresent)
+                .map(Optional::get)
+                .findFirst();
+
+        assertTrue(this.getEmptyEvaluated);
+        assertTrue(this.getHelloEvaluated);
+        assertFalse(this.getByeEvaluated);
+        assertEquals(getHello(), found);
+    }
+
+    @Test
+    public void givenTwoOptionalsReturnedByOneArgMethod_whenChaining_thenFirstNonEmptyIsReturned() {
+        Optional<String> found = Stream.<Supplier<Optional<String>>>of(
+                () -> createOptional("empty"),
+                () -> createOptional("hello")
+        )
+                .map(Supplier::get)
+                .filter(Optional::isPresent)
+                .map(Optional::get)
+                .findFirst();
+
+        assertEquals(createOptional("hello"), found);
+    }
+
+    private Optional<String> getEmpty() {
+        this.getEmptyEvaluated = true;
+        return Optional.empty();
+    }
+
+    private Optional<String> getHello() {
+        this.getHelloEvaluated = true;
+        return Optional.of("hello");
+    }
+
+    private Optional<String> getBye() {
+        this.getByeEvaluated = true;
+        return Optional.of("bye");
+    }
+
+    private Optional<String> createOptional(String input) {
+        if (input == null || input == "" || input == "empty") {
+            return Optional.empty();
+        }
+
+        return Optional.of(input);
+    }
+}
--- a/core-java-9/README.md
+++ b/core-java-9/README.md
@ -5,27 +5,21 @@
 [Java 9 New Features](http://www.baeldung.com/new-java-9)

 ### Relevant Articles:
- [Java 9 Stream API Improvements](http://www.baeldung.com/java-9-stream-api)
- [Java 9 Convenience Factory Methods for Collections](http://www.baeldung.com/java-9-collections-factory-methods) 
+
+- [Java 9 New Features](https://www.baeldung.com/new-java-9)
 - [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
- [Java 9 CompletableFuture API Improvements](http://www.baeldung.com/java-9-completablefuture)
- [Java 9 Process API Improvements](http://www.baeldung.com/java-9-process-api)
- [Introduction to Java 9 StackWalking API](http://www.baeldung.com/java-9-stackwalking-api)
 - [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)
- [Java 9 Optional API Additions](http://www.baeldung.com/java-9-optional)
- [Java 9 Reactive Streams](http://www.baeldung.com/java-9-reactive-streams)
- [Java 9 java.util.Objects Additions](http://www.baeldung.com/java-9-objects-new)
- [Java 9 Variable Handles Demistyfied](http://www.baeldung.com/java-variable-handles)
- [Exploring the New HTTP Client in Java 9](http://www.baeldung.com/java-9-http-client)
+- [Java 9 Variable Handles Demystified](http://www.baeldung.com/java-variable-handles)
+- [Exploring the New HTTP Client in Java 9 and 11](http://www.baeldung.com/java-9-http-client)
 - [Method Handles in Java](http://www.baeldung.com/java-method-handles)
 - [Introduction to Chronicle Queue](http://www.baeldung.com/java-chronicle-queue)
- [A Guide to Java 9 Modularity](http://www.baeldung.com/java-9-modularity)
 - [Optional orElse Optional](http://www.baeldung.com/java-optional-or-else-optional)
- [Java 9 java.lang.Module API](http://www.baeldung.com/java-9-module-api)
 - [Iterate Through a Range of Dates in Java](https://www.baeldung.com/java-iterate-date-range)
 - [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)
 - [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)
 - [Ahead of Time Compilation (AoT)](https://www.baeldung.com/ahead-of-time-compilation)
+- [Java 9 Process API Improvements](https://www.baeldung.com/java-9-process-api)
+- [Guide to java.lang.Process API](https://www.baeldung.com/java-process-api)
+
+
--- a/core-java-collections-list/README.md
+++ b/core-java-collections-list/README.md
@ -5,7 +5,7 @@
 ### Relevant Articles: 
 - [Immutable ArrayList in Java](http://www.baeldung.com/java-immutable-list)
 - [Guide to the Java ArrayList](http://www.baeldung.com/java-arraylist)
- [Random List Element](http://www.baeldung.com/java-random-list-element)
+- [Java – Get Random Item/Element From a List](http://www.baeldung.com/java-random-list-element)
 - [Removing all nulls from a List in Java](http://www.baeldung.com/java-remove-nulls-from-list)
 - [Removing all duplicates from a List in Java](http://www.baeldung.com/java-remove-duplicates-from-list)
 - [How to TDD a List Implementation in Java](http://www.baeldung.com/java-test-driven-list)
@ -30,3 +30,4 @@
 - [Determine If All Elements Are the Same in a Java List](https://www.baeldung.com/java-list-all-equal)
 - [List of Primitive Integer Values in Java](https://www.baeldung.com/java-list-primitive-int)
 - [Performance Comparison of Primitive Lists in Java](https://www.baeldung.com/java-list-primitive-performance)
+- [Filtering a Java Collection by a List](https://www.baeldung.com/java-filter-collection-by-list)
--- a/core-java-collections-list/src/main/java/com/baeldung/collection/filtering/Employee.java
+++ b/core-java-collections-list/src/main/java/com/baeldung/collection/filtering/Employee.java
@ -0,0 +1,44 @@
+package com.baeldung.collection.filtering;
+
+/**
+ * Java 8 Collection Filtering by List of Values base class.
+ *
+ * @author Rodolfo Felipe
+ */
+public class Employee {
+
+    private Integer employeeNumber;
+    private String name;
+    private Integer departmentId;
+
+    public Employee(Integer employeeNumber, String name, Integer departmentId) {
+        this.employeeNumber = employeeNumber;
+        this.name = name;
+        this.departmentId = departmentId;
+    }
+
+    public Integer getEmployeeNumber() {
+        return employeeNumber;
+    }
+
+    public void setEmployeeNumber(Integer employeeNumber) {
+        this.employeeNumber = employeeNumber;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Integer getDepartmentId() {
+        return departmentId;
+    }
+
+    public void setDepartmentId(Integer departmentId) {
+        this.departmentId = departmentId;
+    }
+
+}
--- a/core-java-collections-list/src/test/java/com/baeldung/collection/filtering/CollectionFilteringUnitTest.java
+++ b/core-java-collections-list/src/test/java/com/baeldung/collection/filtering/CollectionFilteringUnitTest.java
@ -0,0 +1,73 @@
+package com.baeldung.collection.filtering;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import org.hamcrest.Matchers;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Various filtering examples.
+ *
+ * @author Rodolfo Felipe
+ */
+public class CollectionFilteringUnitTest {
+
+    private List<Employee> buildEmployeeList() {
+        return Arrays.asList(new Employee(1, "Mike", 1), new Employee(2, "John", 1), new Employee(3, "Mary", 1), new Employee(4, "Joe", 2), new Employee(5, "Nicole", 2), new Employee(6, "Alice", 2), new Employee(7, "Bob", 3), new Employee(8, "Scarlett", 3));
+    }
+
+    private List<String> employeeNameFilter() {
+        return Arrays.asList("Alice", "Mike", "Bob");
+    }
+
+    @Test
+    public void givenEmployeeList_andNameFilterList_thenObtainFilteredEmployeeList_usingForEachLoop() {
+        List<Employee> filteredList = new ArrayList<>();
+        List<Employee> originalList = buildEmployeeList();
+        List<String> nameFilter = employeeNameFilter();
+
+        for (Employee employee : originalList) {
+            for (String name : nameFilter) {
+                if (employee.getName()
+                    .equalsIgnoreCase(name)) {
+                    filteredList.add(employee);
+                }
+            }
+        }
+
+        Assert.assertThat(filteredList.size(), Matchers.is(nameFilter.size()));
+    }
+
+    @Test
+    public void givenEmployeeList_andNameFilterList_thenObtainFilteredEmployeeList_usingLambda() {
+        List<Employee> filteredList;
+        List<Employee> originalList = buildEmployeeList();
+        List<String> nameFilter = employeeNameFilter();
+
+        filteredList = originalList.stream()
+            .filter(employee -> nameFilter.contains(employee.getName()))
+            .collect(Collectors.toList());
+
+        Assert.assertThat(filteredList.size(), Matchers.is(nameFilter.size()));
+    }
+
+    @Test
+    public void givenEmployeeList_andNameFilterList_thenObtainFilteredEmployeeList_usingLambdaAndHashSet() {
+        List<Employee> filteredList;
+        List<Employee> originalList = buildEmployeeList();
+        Set<String> nameFilterSet = employeeNameFilter().stream()
+            .collect(Collectors.toSet());
+
+        filteredList = originalList.stream()
+            .filter(employee -> nameFilterSet.contains(employee.getName()))
+            .collect(Collectors.toList());
+
+        Assert.assertThat(filteredList.size(), Matchers.is(nameFilterSet.size()));
+    }
+
+}
--- a/core-java-collections-map/README.md
+++ b/core-java-collections-map/README.md
@ -0,0 +1,6 @@
+=========
+
+## Core Java Collections 2
+
+### Relevant Articles: 
+- Java - Copying a HashMap
--- a/core-java-collections-map/pom.xml
+++ b/core-java-collections-map/pom.xml
@ -0,0 +1,78 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
+xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-collections-map</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-collections-map</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.collections</groupId>
+            <artifactId>eclipse-collections</artifactId>
+            <version>${eclipse.collections.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${openjdk.jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${openjdk.jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-exec</artifactId>
+            <version>${commons-exec.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <openjdk.jmh.version>1.19</openjdk.jmh.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <commons-lang3.version>3.8.1</commons-lang3.version>
+        <commons-collections4.version>4.1</commons-collections4.version>
+        <collections-generic.version>4.01</collections-generic.version>
+        <avaitility.version>1.7.0</avaitility.version>
+        <assertj.version>3.11.1</assertj.version>
+        <eclipse.collections.version>7.1.0</eclipse.collections.version>
+		<commons-exec.version>1.3</commons-exec.version>
+    </properties>
+</project>
--- a/core-java-collections-map/src/main/java/com/baeldung/copyinghashmap/CopyHashMap.java
+++ b/core-java-collections-map/src/main/java/com/baeldung/copyinghashmap/CopyHashMap.java
@ -0,0 +1,55 @@
+package com.baeldung.copyinghashmap;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import org.apache.commons.lang3.SerializationUtils;
+
+public class CopyHashMap {
+    
+    public static <String, Employee> HashMap<String, Employee> copyUsingConstructor(HashMap<String, Employee> originalMap) {
+        return new HashMap<String, Employee>(originalMap);
+    }
+    
+    public static <String, Employee> HashMap<String, Employee> copyUsingClone(HashMap<String, Employee> originalMap) {
+        return (HashMap<String, Employee>) originalMap.clone();
+    }
+
+    public static <String, Employee> HashMap<String, Employee> copyUsingPut(HashMap<String, Employee> originalMap) {
+        HashMap<String, Employee> shallowCopy = new HashMap<String, Employee>();
+        Set<Entry<String, Employee>> entries = originalMap.entrySet();
+        for(Map.Entry<String, Employee> mapEntry: entries) {
+            shallowCopy.put(mapEntry.getKey(), mapEntry.getValue());
+        }
+        
+        return shallowCopy;
+    }
+    
+    public static <String, Employee> HashMap<String, Employee> copyUsingPutAll(HashMap<String, Employee> originalMap) {
+        HashMap<String, Employee> shallowCopy = new HashMap<String, Employee>();
+        shallowCopy.putAll(originalMap);
+        
+        return shallowCopy;
+    }
+    
+    public static <String, Employee> HashMap<String, Employee> copyUsingJava8Stream(HashMap<String, Employee> originalMap) {
+        Set<Entry<String, Employee>> entries = originalMap.entrySet();
+        HashMap<String, Employee> shallowCopy = (HashMap<String, Employee>) entries
+            .stream()
+            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+        
+        return shallowCopy;
+    }
+    
+    public static <String, Employee> HashMap<String, Employee> shallowCopy(HashMap<String, Employee> originalMap) {
+        return (HashMap<String, Employee>) originalMap.clone();
+    }
+    
+    public static <String, Employee> HashMap<String, Employee> deepCopy(HashMap<String, Employee> originalMap) {
+        return SerializationUtils.clone(originalMap);
+    }
+    
+}
--- a/core-java-collections-map/src/test/java/com/baeldung/copyinghashmap/CopyHashMapUnitTest.java
+++ b/core-java-collections-map/src/test/java/com/baeldung/copyinghashmap/CopyHashMapUnitTest.java
@ -0,0 +1,77 @@
+package com.baeldung.copyinghashmap;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Test;
+
+import com.google.common.collect.ImmutableMap;
+
+public class CopyHashMapUnitTest {
+    
+    @Test
+    public void givenHashMap_whenShallowCopy_thenCopyisNotSameAsOriginal() {
+        
+        HashMap<String, Employee> map = new HashMap<>();
+        Employee emp1 = new Employee("John");
+        Employee emp2 = new Employee("Norman");
+        map.put("emp1",emp1);
+        map.put("emp2",emp2);
+    
+        HashMap<String, Employee> shallowCopy = CopyHashMap.shallowCopy(map);
+        
+        assertThat(shallowCopy).isNotSameAs(map);
+        
+    }
+    
+    @Test
+    public void givenHashMap_whenShallowCopyModifyingOriginalObject_thenCopyShouldChange() {
+        
+        HashMap<String, Employee> map = new HashMap<>();
+        Employee emp1 = new Employee("John");
+        Employee emp2 = new Employee("Norman");
+        map.put("emp1",emp1);
+        map.put("emp2",emp2);
+        
+        HashMap<String, Employee> shallowCopy = CopyHashMap.shallowCopy(map);
+        
+        emp1.setName("Johny");
+        
+        assertThat(shallowCopy.get("emp1")).isEqualTo(map.get("emp1"));
+        
+    }
+    
+    @Test
+    public void givenHashMap_whenDeepCopyModifyingOriginalObject_thenCopyShouldNotChange() {
+        
+        HashMap<String, Employee> map = new HashMap<>();
+        Employee emp1 = new Employee("John");
+        Employee emp2 = new Employee("Norman");
+        map.put("emp1",emp1);
+        map.put("emp2",emp2);
+        HashMap<String, Employee> deepCopy = CopyHashMap.deepCopy(map);
+        
+        emp1.setName("Johny");
+        
+        assertThat(deepCopy.get("emp1")).isNotEqualTo(map.get("emp1"));
+        
+    }
+    
+    @Test
+    public void givenImmutableMap_whenCopyUsingGuava_thenCopyShouldNotChange() {
+        Employee emp1 = new Employee("John");
+        Employee emp2 = new Employee("Norman");
+        
+        Map<String, Employee> map = ImmutableMap.<String, Employee> builder()
+            .put("emp1",emp1)
+            .put("emp2",emp2)
+            .build();
+        Map<String, Employee> shallowCopy = ImmutableMap.copyOf(map);
+        
+        assertThat(shallowCopy).isSameAs(map);
+        
+    }
+
+}
--- a/core-java-collections-map/src/test/java/com/baeldung/copyinghashmap/Employee.java
+++ b/core-java-collections-map/src/test/java/com/baeldung/copyinghashmap/Employee.java
@ -0,0 +1,28 @@
+package com.baeldung.copyinghashmap;
+
+import java.io.Serializable;
+
+public class Employee implements Serializable{
+    
+    private String name;
+    
+    public Employee(String name) {
+        super();
+        this.name = name;
+    }
+    public String getName() {
+        return name;
+    }
+    
+    public void setName(String name) {
+        this.name = name;
+    }
+    
+    @Override
+    public String toString() {
+        return this.name;
+    }
+ 
+}
+
+
--- a/core-java-collections/README.md
+++ b/core-java-collections/README.md
@ -3,7 +3,7 @@
 ## Core Java Collections Cookbooks and Examples

 ### Relevant Articles: 
- [Java - Combine Multiple Collections](http://www.baeldung.com/java-combine-multiple-collections)
+- [Java – Combine Multiple Collections](http://www.baeldung.com/java-combine-multiple-collections)
 - [HashSet and TreeSet Comparison](http://www.baeldung.com/java-hashset-vs-treeset)
 - [Collect a Java Stream to an Immutable Collection](http://www.baeldung.com/java-stream-immutable-collection)
 - [Introduction to the Java ArrayDeque](http://www.baeldung.com/java-array-deque)
@ -33,3 +33,4 @@
 - [Differences Between HashMap and Hashtable](https://www.baeldung.com/hashmap-hashtable-differences)
 - [Java ArrayList vs Vector](https://www.baeldung.com/java-arraylist-vs-vector)
 - [Defining a Char Stack in Java](https://www.baeldung.com/java-char-stack)
+- [Time Comparison of Arrays.sort(Object[]) and Arrays.sort(int[])](https://www.baeldung.com/arrays-sortobject-vs-sortint)
--- a/core-java-collections/src/main/java/com/baeldung/performance/ArraySortBenchmark.java
+++ b/core-java-collections/src/main/java/com/baeldung/performance/ArraySortBenchmark.java
@ -1,17 +1,21 @@
 package com.baeldung.performance;

-import org.openjdk.jmh.annotations.*;
+import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
 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.Arrays;
-import java.util.Collections;
-import java.util.List;
-import java.util.concurrent.TimeUnit;
-
-@BenchmarkMode(Mode.SingleShotTime)
+@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@Measurement(batchSize = 100000, iterations = 10)
@Warmup(batchSize = 100000, iterations = 10)
@ -19,8 +23,8 @@ public class ArraySortBenchmark {

    @State(Scope.Thread)
    public static class Initialize {
-        Integer[] numbers = {5, 22, 10, 0};
-        int[] primitives = {5, 22, 10, 0};
+        Integer[] numbers = { -769214442, -1283881723, 1504158300, -1260321086, -1800976432, 1278262737, 1863224321, 1895424914, 2062768552, -1051922993, 751605209, -1500919212, 2094856518, -1014488489, -931226326, -1677121986, -2080561705, 562424208, -1233745158, 41308167 };
+        int[] primitives = { -769214442, -1283881723, 1504158300, -1260321086, -1800976432, 1278262737, 1863224321, 1895424914, 2062768552, -1051922993, 751605209, -1500919212, 2094856518, -1014488489, -931226326, -1677121986, -2080561705, 562424208, -1233745158, 41308167 };
    }

    @Benchmark
--- a/core-java-concurrency-advanced/README.md
+++ b/core-java-concurrency-advanced/README.md
@ -12,7 +12,7 @@
 - [Guide to the Java Phaser](http://www.baeldung.com/java-phaser)
 - [An Introduction to Atomic Variables in Java](http://www.baeldung.com/java-atomic-variables)
 - [CyclicBarrier in Java](http://www.baeldung.com/java-cyclic-barrier)
- [Guide to Volatile Keyword in Java](http://www.baeldung.com/java-volatile)
+- [Guide to the Volatile Keyword in Java](http://www.baeldung.com/java-volatile)
 - [Semaphores in Java](http://www.baeldung.com/java-semaphore)
 - [Daemon Threads in Java](http://www.baeldung.com/java-daemon-thread)
 - [Priority-based Job Scheduling in Java](http://www.baeldung.com/java-priority-job-schedule)
@ -20,5 +20,6 @@
 - [Print Even and Odd Numbers Using 2 Threads](https://www.baeldung.com/java-even-odd-numbers-with-2-threads)
 - [Java CyclicBarrier vs CountDownLatch](https://www.baeldung.com/java-cyclicbarrier-countdownlatch)
 - [Guide to the Fork/Join Framework in Java](http://www.baeldung.com/java-fork-join)
- [A Guide to ThreadLocalRandom in Java](http://www.baeldung.com/java-thread-local-random)
+- [Guide to ThreadLocalRandom in Java](http://www.baeldung.com/java-thread-local-random)
 - [The Thread.join() Method in Java](http://www.baeldung.com/java-thread-join)
+- [Passing Parameters to Java Threads](https://www.baeldung.com/java-thread-parameters)
--- a/core-java-concurrency-basic/README.md
+++ b/core-java-concurrency-basic/README.md
@ -7,12 +7,13 @@
 - [A Guide to the Java ExecutorService](http://www.baeldung.com/java-executor-service-tutorial)
 - [Guide to java.util.concurrent.Future](http://www.baeldung.com/java-future)
 - [Difference Between Wait and Sleep in Java](http://www.baeldung.com/java-wait-and-sleep)
- [Guide to Synchronized Keyword in Java](http://www.baeldung.com/java-synchronized)
+- [Guide to the Synchronized Keyword in Java](http://www.baeldung.com/java-synchronized)
 - [Overview of the java.util.concurrent](http://www.baeldung.com/java-util-concurrent)
 - [Implementing a Runnable vs Extending a Thread](http://www.baeldung.com/java-runnable-vs-extending-thread)
 - [How to Kill a Java Thread](http://www.baeldung.com/java-thread-stop)
- [ExecutorService - Waiting for Threads to Finish](http://www.baeldung.com/java-executor-wait-for-threads)
+- [ExecutorService – Waiting for Threads to Finish](http://www.baeldung.com/java-executor-wait-for-threads)
 - [wait and notify() Methods in Java](http://www.baeldung.com/java-wait-notify)
 - [Life Cycle of a Thread in Java](http://www.baeldung.com/java-thread-lifecycle)
 - [Runnable vs. Callable in Java](http://www.baeldung.com/java-runnable-callable)
- [What is Thread-Safety and How to Achieve it](https://www.baeldung.com/java-thread-safety)
+- [What is Thread-Safety and How to Achieve it?](https://www.baeldung.com/java-thread-safety)
+- [How to Start a Thread in Java](https://www.baeldung.com/java-start-thread)
--- a/core-java-io/README.md
+++ b/core-java-io/README.md
@ -3,18 +3,18 @@
 ## Core Java IO Cookbooks and Examples

 ### Relevant Articles: 
- [Java - Reading a Large File Efficiently](http://www.baeldung.com/java-read-lines-large-file)
+- [How to Read a Large File Efficiently with Java](http://www.baeldung.com/java-read-lines-large-file)
 - [Java InputStream to String](http://www.baeldung.com/convert-input-stream-to-string)
 - [Java – Write to File](http://www.baeldung.com/java-write-to-file)
- [Java - Convert File to InputStream](http://www.baeldung.com/convert-file-to-input-stream)
+- [Java – Convert File to InputStream](http://www.baeldung.com/convert-file-to-input-stream)
 - [Java Scanner](http://www.baeldung.com/java-scanner)
 - [Java – Byte Array to Writer](http://www.baeldung.com/java-convert-byte-array-to-writer)
 - [Java – Directory Size](http://www.baeldung.com/java-folder-size)
 - [Differences Between the Java WatchService API and the Apache Commons IO Monitor Library](http://www.baeldung.com/java-watchservice-vs-apache-commons-io-monitor-library)
- [Calculate the Size of a File in Java](http://www.baeldung.com/java-file-size)
+- [File Size in Java](http://www.baeldung.com/java-file-size)
 - [Comparing getPath(), getAbsolutePath(), and getCanonicalPath() in Java](http://www.baeldung.com/java-path)
 - [Using Java MappedByteBuffer](http://www.baeldung.com/java-mapped-byte-buffer)
- [Copy a File with Java](http://www.baeldung.com/java-copy-file)
+- [How to Copy a File with Java](http://www.baeldung.com/java-copy-file)
 - [Java – Append Data to a File](http://www.baeldung.com/java-append-to-file)
 - [FileNotFoundException in Java](http://www.baeldung.com/java-filenotfound-exception)
 - [How to Read a File in Java](http://www.baeldung.com/reading-file-in-java)
@ -30,7 +30,6 @@
 - [Download a File From an URL in Java](http://www.baeldung.com/java-download-file)
 - [Create a Symbolic Link with Java](http://www.baeldung.com/java-symlink)
 - [Quick Use of FilenameFilter](http://www.baeldung.com/java-filename-filter)
- [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
 - [Read a File into an ArrayList](https://www.baeldung.com/java-file-to-arraylist)
 - [Guide to Java OutputStream](https://www.baeldung.com/java-outputstream)
 - [Reading a CSV File into an Array](https://www.baeldung.com/java-csv-file-array)
@ -40,3 +39,4 @@
 - [Create a Directory in Java](https://www.baeldung.com/java-create-directory)
 - [How to Write to a CSV File in Java](https://www.baeldung.com/java-csv)
 - [List Files in a Directory in Java](https://www.baeldung.com/java-list-directory-files)
+- [Java InputStream to Byte Array and ByteBuffer](https://www.baeldung.com/convert-input-stream-to-array-of-bytes)
--- a/core-java-jvm/README.md
+++ b/core-java-jvm/README.md
@ -0,0 +1,6 @@
+=========
+
+## Core Java JVM Cookbooks and Examples
+
+### Relevant Articles: 
+- [Method Inlining in the JVM](https://www.baeldung.com/jvm-method-inlining)
--- a/core-java-jvm/pom.xml
+++ b/core-java-jvm/pom.xml
@ -0,0 +1,40 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-jvm</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
+    <name>core-java-jvm</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <commons-lang3.version>3.5</commons-lang3.version>
+        <assertj.version>3.6.1</assertj.version>
+    </properties>
+</project>
--- a/core-java-jvm/src/main/java/com/baeldung/inlining/ConsecutiveNumbersSum.java
+++ b/core-java-jvm/src/main/java/com/baeldung/inlining/ConsecutiveNumbersSum.java
@ -0,0 +1,19 @@
+package com.baeldung.inlining;
+
+public class ConsecutiveNumbersSum {
+
+    private long totalSum;
+    private int totalNumbers;
+
+    public ConsecutiveNumbersSum(int totalNumbers) {
+        this.totalNumbers = totalNumbers;
+    }
+
+    public long getTotalSum() {
+        totalSum = 0;
+        for (int i = 1; i <= totalNumbers; i++) {
+            totalSum += i;
+        }
+        return totalSum;
+    }
+}
--- a/core-java-jvm/src/main/java/com/baeldung/inlining/InliningExample.java
+++ b/core-java-jvm/src/main/java/com/baeldung/inlining/InliningExample.java
@ -0,0 +1,16 @@
+package com.baeldung.inlining;
+
+public class InliningExample {
+
+    public static final int NUMBERS_OF_ITERATIONS = 15000;
+
+    public static void main(String[] args) {
+        for (int i = 1; i < NUMBERS_OF_ITERATIONS; i++) {
+            calculateSum(i);
+        }
+    }
+
+    private static long calculateSum(int n) {
+        return new ConsecutiveNumbersSum(n).getTotalSum();
+    }
+}
--- a/core-java-jvm/src/test/java/com/baeldung/inlining/ConsecutiveNumbersSumUnitTest.java
+++ b/core-java-jvm/src/test/java/com/baeldung/inlining/ConsecutiveNumbersSumUnitTest.java
@ -0,0 +1,22 @@
+package com.baeldung.inlining;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class ConsecutiveNumbersSumUnitTest {
+
+    private static final int TOTAL_NUMBERS = 10;
+
+    @Test
+    public void givenTotalIntegersNumber_whenSumCalculated_thenEquals() {
+        ConsecutiveNumbersSum consecutiveNumbersSum = new ConsecutiveNumbersSum(TOTAL_NUMBERS);
+        long expectedSum = calculateExpectedSum(TOTAL_NUMBERS);
+
+        assertEquals(expectedSum, consecutiveNumbersSum.getTotalSum());
+    }
+
+    private long calculateExpectedSum(int totalNumbers) {
+        return totalNumbers * (totalNumbers + 1) / 2;
+    }
+}
--- a/core-java-lambdas/pom.xml
+++ b/core-java-lambdas/pom.xml
@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <artifactId>core-java-lambdas</artifactId>
+  <version>0.1.0-SNAPSHOT</version>
+  <name>core-java</name>
+  <packaging>jar</packaging>
+
+  <parent>
+    <groupId>com.baeldung</groupId>
+    <artifactId>parent-java</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <relativePath>../parent-java</relativePath>
+  </parent>
+
+
+</project>
--- a/core-java-lambdas/src/main/java/com/baeldung/lambdas/LambdaVariables.java
+++ b/core-java-lambdas/src/main/java/com/baeldung/lambdas/LambdaVariables.java
@ -0,0 +1,88 @@
+package com.baeldung.lambdas;
+
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.function.Supplier;
+import java.util.stream.IntStream;
+
+/**
+ * Class with examples about working with capturing lambdas.
+ */
+public class LambdaVariables {
+
+    private volatile boolean run = true;
+    private int start = 0;
+
+    private ExecutorService executor = Executors.newFixedThreadPool(3);
+
+    public static void main(String[] args) {
+        new LambdaVariables().localVariableMultithreading();
+    }
+
+    Supplier<Integer> incrementer(int start) {
+        return () -> start; // can't modify start parameter inside the lambda
+    }
+
+    Supplier<Integer> incrementer() {
+        return () -> start++;
+    }
+
+    public void localVariableMultithreading() {
+        boolean run = true;
+        executor.execute(() -> {
+            while (run) {
+                // do operation
+            }
+        });
+        // commented because it doesn't compile, it's just an example of non-final local variables in lambdas
+        // run = false;
+    }
+
+    public void instanceVariableMultithreading() {
+        executor.execute(() -> {
+            while (run) {
+                // do operation
+            }
+        });
+
+        run = false;
+    }
+
+    /**
+     * WARNING: always avoid this workaround!!
+     */
+    public void workaroundSingleThread() {
+        int[] holder = new int[] { 2 };
+        IntStream sums = IntStream
+          .of(1, 2, 3)
+          .map(val -> val + holder[0]);
+
+        holder[0] = 0;
+
+        System.out.println(sums.sum());
+    }
+
+    /**
+     * WARNING: always avoid this workaround!!
+     */
+    public void workaroundMultithreading() {
+        int[] holder = new int[] { 2 };
+        Runnable runnable = () -> System.out.println(IntStream
+          .of(1, 2, 3)
+          .map(val -> val + holder[0])
+          .sum());
+
+        new Thread(runnable).start();
+
+        // simulating some processing
+        try {
+            Thread.sleep(new Random().nextInt(3) * 1000L);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+
+        holder[0] = 0;
+    }
+
+}
--- a/core-java-lang-oop-2/.gitignore
+++ b/core-java-lang-oop-2/.gitignore
@ -0,0 +1,4 @@
+target/
+.idea/
+bin/
+*.iml
--- a/core-java-lang-oop-2/README.md
+++ b/core-java-lang-oop-2/README.md
@ -0,0 +1,5 @@
+=========
+
+## Core Java Lang OOP 2 Cookbooks and Examples
+
+### Relevant Articles: 
--- a/core-java-lang-oop-2/pom.xml
+++ b/core-java-lang-oop-2/pom.xml
@ -0,0 +1,27 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-lang-oop-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-lang-oop-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <build>
+        <finalName>core-java-lang-oop-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+</project>
--- a/core-java-lang-oop-2/src/main/java/com/baeldung/supertypecompilerexception/MyClass.java
+++ b/core-java-lang-oop-2/src/main/java/com/baeldung/supertypecompilerexception/MyClass.java
@ -0,0 +1,16 @@
+package com.baeldung.supertypecompilerexception;
+
+public class MyClass {
+
+    private int myField1 = 10;
+    private int myField2;
+
+    public MyClass() {
+        //uncomment this to see the supertype compiler error:
+        //this(myField1);
+    }
+
+    public MyClass(int i) {
+        myField2 = i;
+    }
+}
--- a/core-java-lang-oop-2/src/main/java/com/baeldung/supertypecompilerexception/MyClassSolution1.java
+++ b/core-java-lang-oop-2/src/main/java/com/baeldung/supertypecompilerexception/MyClassSolution1.java
@ -0,0 +1,15 @@
+package com.baeldung.supertypecompilerexception;
+
+public class MyClassSolution1 {
+
+    private int myField1 = 10;
+    private int myField2;
+
+    public MyClassSolution1() {
+        myField2 = myField1;
+    }
+
+    public MyClassSolution1(int i) {
+        myField2 = i;
+    }
+}
--- a/Show More
+++ b/Show More