Merge branch 'master' of https://github.com/eugenp/tutorials

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/helpfulnullpointerexceptions/HelpfulNullPointerException.java

@@ -0,0 +1,56 @@
+package com.baeldung.java14.helpfulnullpointerexceptions;
+
+public class HelpfulNullPointerException {
+
+    public static void main(String[] args) {
+        Employee employee = null;
+        employee.getName();
+    }
+
+    public String getEmployeeEmailAddress(Employee employee) {
+        String emailAddress = employee.getPersonalDetails().getEmailAddress().toLowerCase();
+        return emailAddress;
+    }
+
+    static class Employee {
+        String name;
+        PersonalDetails personalDetails;
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+
+        public PersonalDetails getPersonalDetails() {
+            return personalDetails;
+        }
+
+        public void setPersonalDetails(PersonalDetails personalDetails) {
+            this.personalDetails = personalDetails;
+        }
+    }
+
+    static class PersonalDetails {
+        String emailAddress;
+        String phone;
+
+        public String getEmailAddress() {
+            return emailAddress;
+        }
+
+        public void setEmailAddress(String emailAddress) {
+            this.emailAddress = emailAddress;
+        }
+
+        public String getPhone() {
+            return phone;
+        }
+
+        public void setPhone(String phone) {
+            this.phone = phone;
+        }
+    }
+}

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/helpfulnullpointerexceptions/HelpfulNullPointerExceptionUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.java14.helpfulnullpointerexceptions;
+
+import org.junit.Test;
+
+import static com.baeldung.java14.helpfulnullpointerexceptions.HelpfulNullPointerException.Employee;
+import static com.baeldung.java14.helpfulnullpointerexceptions.HelpfulNullPointerException.PersonalDetails;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class HelpfulNullPointerExceptionUnitTest {
+
+    @Test (expected = NullPointerException.class)
+    public void givenAnEmptyPersonalDetails_whenEmailAddressIsAccessed_thenThrowNPE() {
+        var helpfulNPE = new HelpfulNullPointerException();
+
+        var employee = new Employee();
+        employee.setName("Eduard");
+        employee.setPersonalDetails(new PersonalDetails());
+        helpfulNPE.getEmployeeEmailAddress(employee);
+    }
+
+    @Test
+    public void givenCompletePersonalDetails_whenEmailAddressIsAccessed_thenSuccess() {
+        var helpfulNPE = new HelpfulNullPointerException();
+        var emailAddress = "eduard@gmx.com";
+
+        var employee = new Employee();
+        employee.setName("Eduard");
+
+        var personalDetails = new PersonalDetails();
+        personalDetails.setEmailAddress(emailAddress.toUpperCase());
+        personalDetails.setPhone("1234");
+        employee.setPersonalDetails(personalDetails);
+
+        assertThat(helpfulNPE.getEmployeeEmailAddress(employee)).isEqualTo(emailAddress);
+    }
+
+}

core-java-modules/core-java-concurrency-advanced/src/main/java/com/baeldung/concurrent/volatilekeyword/TaskRunner.java

@@ -0,0 +1,25 @@
+package com.baeldung.concurrent.volatilekeyword;
+
+public class TaskRunner {
+
+    private static int number;
+    private volatile static boolean ready;
+
+    private static class Reader extends Thread {
+
+        @Override
+        public void run() {
+            while (!ready) {
+                Thread.yield();
+            }
+
+            System.out.println(number);
+        }
+    }
+
+    public static void main(String[] args) {
+        new Reader().start();
+        number = 42;
+        ready = true;
+    }
+}

core-java-modules/core-java-lambdas/src/test/java/com/baeldung/java8/Java8SortUnitTest.java

@@ -1,18 +1,17 @@
 package com.baeldung.java8;
 
-import static org.hamcrest.Matchers.equalTo;
+import com.baeldung.java8.entity.Human;
+import com.google.common.collect.Lists;
+import com.google.common.primitives.Ints;
+import org.junit.Assert;
+import org.junit.Test;
 
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.stream.Collectors;
 
-import org.junit.Assert;
-import org.junit.Test;
-
-import com.baeldung.java8.entity.Human;
-import com.google.common.collect.Lists;
-import com.google.common.primitives.Ints;
+import static org.hamcrest.Matchers.equalTo;
 
 public class Java8SortUnitTest {
 
@@ -113,11 +112,11 @@ public class Java8SortUnitTest {
         humans.sort(Comparator.comparing(Human::getName));
         Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
     }
-    
+
     @Test
     public final void givenStreamNaturalOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
         final List<String> letters = Lists.newArrayList("B", "A", "C");
-        
+
         final List<String> sortedLetters = letters.stream().sorted().collect(Collectors.toList());
         Assert.assertThat(sortedLetters.get(0), equalTo("A"));
     }
@@ -126,7 +125,7 @@ public class Java8SortUnitTest {
     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)));
     }
@@ -164,4 +163,48 @@ public class Java8SortUnitTest {
         Assert.assertThat(reverseSortedHumans.get(0), equalTo(new Human("Sarah", 10)));
     }
 
+    @Test(expected = NullPointerException.class)
+    public final void givenANullElement_whenSortingEntitiesByName_thenThrowsNPE() {
+        final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12));
+
+        humans.sort((h1, h2) -> h1.getName().compareTo(h2.getName()));
+    }
+
+    @Test
+    public final void givenANullElement_whenSortingEntitiesByNameManually_thenMovesTheNullToLast() {
+        final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12), null);
+
+        humans.sort((h1, h2) -> {
+            if (h1 == null) return h2 == null ? 0 : 1;
+            else if (h2 == null) return -1;
+
+            return h1.getName().compareTo(h2.getName());
+        });
+
+        Assert.assertNotNull(humans.get(0));
+        Assert.assertNull(humans.get(1));
+        Assert.assertNull(humans.get(2));
+    }
+
+    @Test
+    public final void givenANullElement_whenSortingEntitiesByName_thenMovesTheNullToLast() {
+        final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12), null);
+
+        humans.sort(Comparator.nullsLast(Comparator.comparing(Human::getName)));
+
+        Assert.assertNotNull(humans.get(0));
+        Assert.assertNull(humans.get(1));
+        Assert.assertNull(humans.get(2));
+    }
+
+    @Test
+    public final void givenANullElement_whenSortingEntitiesByName_thenMovesTheNullToStart() {
+        final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12), null);
+
+        humans.sort(Comparator.nullsFirst(Comparator.comparing(Human::getName)));
+
+        Assert.assertNull(humans.get(0));
+        Assert.assertNull(humans.get(1));
+        Assert.assertNotNull(humans.get(2));
+    }
 }

core-java-modules/core-java-lang-2/src/test/java/com/baeldung/comparelong/CompareLongUnitTest.java

@@ -1,8 +1,12 @@
 package com.baeldung.comparelong;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatCode;
+
 import org.junit.Test;
 
+import java.util.Objects;
+
 public class CompareLongUnitTest {
 
     @Test
@@ -32,6 +36,33 @@ public class CompareLongUnitTest {
         assertThat(l1.equals(l2)).isTrue();
     }
 
+    @Test
+    public void givenLongValuesLessThan128_whenUsingObjectsEquals_thenSuccess() {
+
+        Long l1 = 127L;
+        Long l2 = 127L;
+
+        assertThat(Objects.equals(l1, l2)).isTrue();
+    }
+
+    @Test
+    public void givenLongValuesGreaterOrEqualsThan128_whenUsingObjectsEquals_thenSuccess() {
+
+        Long l1 = 128L;
+        Long l2 = 128L;
+
+        assertThat(Objects.equals(l1, l2)).isTrue();
+    }
+
+    @Test
+    public void givenNullReference_whenUsingObjectsEquals_thenNoException() {
+
+        Long l1 = null;
+        Long l2 = 128L;
+
+        assertThatCode(() -> Objects.equals(l1, l2)).doesNotThrowAnyException();
+    }
+
     @Test
     public void givenLongValuesGreaterOrEqualsThan128_whenUsingComparisonOperator_andLongValue_thenSuccess() {
 

core-java-modules/core-java-security-2/README.md

@@ -1,3 +1,11 @@
+## Core Java Security 
+
+This module contains articles about core Java Security
+
 ### Relevant Articles:
 
 - [Guide To The Java Authentication And Authorization Service (JAAS)](https://www.baeldung.com/java-authentication-authorization-service)
+- [MD5 Hashing in Java](http://www.baeldung.com/java-md5)
+- [Hashing a Password in Java](https://www.baeldung.com/java-password-hashing)
+- [SHA-256 and SHA3-256 Hashing in Java](https://www.baeldung.com/sha-256-hashing-java)
+- More articles: [[<-- prev]](/core-java-modules/core-java-security)

core-java-modules/core-java-security-2/pom.xml

@@ -16,4 +16,45 @@
         <relativePath>../../parent-java</relativePath>
     </parent>
 
+    <dependencies>
+
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>${commons-codec.version}</version>
+        </dependency>
+        
+        <dependency>
+            <groupId>org.bouncycastle</groupId>
+            <artifactId>bcprov-jdk15on</artifactId>
+            <version>${bouncycastle.version}</version>
+        </dependency>
+        
+         <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <!-- https://mvnrepository.com/artifact/javax.xml.bind/jaxb-api -->
+        <dependency>
+            <groupId>javax.xml.bind</groupId>
+            <artifactId>jaxb-api</artifactId>
+            <version>2.3.1</version>
+        </dependency>
+
+
+    </dependencies>
+    
+    <properties>
+        <!-- util -->
+        <bouncycastle.version>1.60</bouncycastle.version>
+        <commons-codec.version>1.11</commons-codec.version>
+
+        <!-- testing -->
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+
 </project>

core-java-modules/core-java-security-2/src/main/java/com/baeldung/checksums/ChecksumUtils.java

@@ -0,0 +1,23 @@
+package com.baeldung.checksums;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.zip.CRC32;
+import java.util.zip.CheckedInputStream;
+import java.util.zip.Checksum;
+
+public class ChecksumUtils {
+
+    public static long getChecksumCRC32(byte[] bytes) {
+        Checksum crc32 = new CRC32();
+        crc32.update(bytes, 0, bytes.length);
+        return crc32.getValue();
+    }
+
+    public static long getChecksumCRC32(InputStream stream, int bufferSize) throws IOException {
+        CheckedInputStream checkedInputStream = new CheckedInputStream(stream, new CRC32());
+        byte[] buffer = new byte[bufferSize];
+        while (checkedInputStream.read(buffer, 0, buffer.length) >= 0) {}
+        return checkedInputStream.getChecksum().getValue();
+    }
+}

core-java-modules/core-java-security-2/src/test/java/com/baeldung/checksums/ChecksumUtilsUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.checksums;
+
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ChecksumUtilsUnitTest {
+
+    byte[] arr;
+
+    @Before
+    void setUp() {
+        arr =  new byte[]{0,10,21,20,35,40,120,56,72,22};
+    }
+
+    @Test
+    void givenByteArray_whenChecksumCreated_checkCorrect() {
+
+        long checksum = ChecksumUtils.getChecksumCRC32(arr);
+
+        assertEquals(3915397664L, checksum);
+    }
+
+    @Test
+    void givenTwoDifferentStrings_whenChecksumCreated_checkCollision() {
+
+        String plumless = "plumless";
+        String buckeroo = "buckeroo";
+
+        long plumlessChecksum = ChecksumUtils.getChecksumCRC32(plumless.getBytes());
+        long buckerooChecksum = ChecksumUtils.getChecksumCRC32(buckeroo.getBytes());
+
+        assertEquals(plumlessChecksum, buckerooChecksum);
+    }
+
+    @Test
+    void givenInputString_whenChecksumCreated_checkCorrect() throws IOException {
+
+        InputStream inputStream = new ByteArrayInputStream(arr);
+        long checksum = ChecksumUtils.getChecksumCRC32(inputStream, 10);
+
+        assertEquals(3915397664L, checksum);
+
+    }
+}

core-java-modules/core-java-security/README.md

@@ -3,17 +3,16 @@
 This module contains articles about core Java Security
 
 ### Relevant Articles: 
-- [MD5 Hashing in Java](http://www.baeldung.com/java-md5)
+
 - [Guide to the Cipher Class](http://www.baeldung.com/java-cipher-class)
 - [Introduction to SSL in Java](http://www.baeldung.com/java-ssl)
 - [Java KeyStore API](http://www.baeldung.com/java-keystore)
 - [Encrypting and Decrypting Files in Java](http://www.baeldung.com/java-cipher-input-output-stream)
-- [Hashing a Password in Java](https://www.baeldung.com/java-password-hashing)
 - [SSL Handshake Failures](https://www.baeldung.com/java-ssl-handshake-failures)
-- [SHA-256 and SHA3-256 Hashing in Java](https://www.baeldung.com/sha-256-hashing-java)
 - [Enabling TLS v1.2 in Java 7](https://www.baeldung.com/java-7-tls-v12)
 - [The Java SecureRandom Class](https://www.baeldung.com/java-secure-random)
 - [An Introduction to Java SASL](https://www.baeldung.com/java-sasl)
 - [A Guide to Java GSS API](https://www.baeldung.com/java-gss)
 - [Intro to the Java SecurityManager](https://www.baeldung.com/java-security-manager)
+- More articles: [[next -->]](/core-java-modules/core-java-security-2)
 

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

@@ -24,24 +24,9 @@
             <version>${assertj-core.version}</version>
             <scope>test</scope>
         </dependency>
-
-        <dependency>
-            <groupId>commons-codec</groupId>
-            <artifactId>commons-codec</artifactId>
-            <version>${commons-codec.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.bouncycastle</groupId>
-            <artifactId>bcprov-jdk15on</artifactId>
-            <version>${bouncycastle.version}</version>
-        </dependency>
     </dependencies>
 
     <properties>
-        <!-- util -->
-        <bouncycastle.version>1.60</bouncycastle.version>
-        <commons-codec.version>1.11</commons-codec.version>
-
         <!-- testing -->
         <assertj-core.version>3.10.0</assertj-core.version>
     </properties>

core-java-modules/core-java-streams-3/src/test/java/com/baeldung/streams/bigdecimals/AddNumbersUnitTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.streams.bigdecimals;
+
+import static org.junit.Assert.assertEquals;
+
+import java.math.BigDecimal;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+import org.junit.Test;
+
+public class AddNumbersUnitTest {
+
+    @Test
+    public void givenIntStream_whenSum_thenResultIsCorrect() {
+        IntStream intNumbers = IntStream.range(0, 3);
+        assertEquals(3, intNumbers.sum());
+    }
+
+    @Test
+    public void givenCollectionOfDouble_whenUsingMapToDoubleToSum_thenResultIsCorrect() {
+        List<Double> doubleNumbers = Arrays.asList(23.48, 52.26, 13.5);
+        double result = doubleNumbers.stream()
+            .mapToDouble(Double::doubleValue)
+            .sum();
+        assertEquals(89.24, result, .1);
+    }
+
+    public void givenStreamOfIntegers_whenUsingReduceToSum_thenResultIsCorrect() {
+        Stream<Integer> intNumbers = Stream.of(0, 1, 2);
+        int result = intNumbers.reduce(0, Integer::sum);
+        assertEquals(106, result);
+    }
+
+    public void givenStreamOfBigDecimals_whenUsingReduceToSum_thenResultIsCorrect() {
+        Stream<BigDecimal> bigDecimalNumber = Stream.of(BigDecimal.ZERO, BigDecimal.ONE, BigDecimal.TEN);
+        BigDecimal result = bigDecimalNumber.reduce(BigDecimal.ZERO, BigDecimal::add);
+        assertEquals(11, result);
+    }
+
+}

guava-collections-map/src/main/java/com/baeldung/guava/mapmaker/Profile.java

@@ -0,0 +1,20 @@
+package com.baeldung.guava.mapmaker;
+
+public class Profile {
+    private long id;
+    private String type;
+
+    public Profile(long id, String type) {
+        this.id = id;
+        this.type = type;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public String getName() {
+        return type;
+    }
+
+}

guava-collections-map/src/main/java/com/baeldung/guava/mapmaker/Session.java

@@ -0,0 +1,13 @@
+package com.baeldung.guava.mapmaker;
+
+public class Session {
+    private long id;
+
+    public Session(long id) {
+        this.id = id;
+    }
+
+    public long getId() {
+        return id;
+    }
+}

guava-collections-map/src/main/java/com/baeldung/guava/mapmaker/User.java

@@ -0,0 +1,20 @@
+package com.baeldung.guava.mapmaker;
+
+public class User {
+    private long id;
+    private String name;
+
+    public User(long id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+}

guava-collections-map/src/test/java/com/baeldung/guava/mapmaker/GuavaMapMakerUnitTest.java

@@ -0,0 +1,53 @@
+package com.baeldung.guava.mapmaker;
+
+import com.google.common.collect.MapMaker;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.concurrent.ConcurrentMap;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertNotNull;
+
+public class GuavaMapMakerUnitTest {
+    @Test
+    public void whenCreateCaches_thenCreated() {
+        ConcurrentMap<User, Session> sessionCache = new MapMaker().makeMap();
+        assertNotNull(sessionCache);
+
+        ConcurrentMap<User, Profile> profileCache = new MapMaker().makeMap();
+        assertNotNull(profileCache);
+
+        User userA = new User(1, "UserA");
+
+        sessionCache.put(userA, new Session(100));
+        Assert.assertThat(sessionCache.size(), equalTo(1));
+
+        profileCache.put(userA, new Profile(1000, "Personal"));
+        Assert.assertThat(profileCache.size(), equalTo(1));
+    }
+
+    @Test
+    public void whenCreateCacheWithInitialCapacity_thenCreated() {
+        ConcurrentMap<User, Profile> profileCache = new MapMaker().initialCapacity(100).makeMap();
+        assertNotNull(profileCache);
+    }
+
+    @Test
+    public void whenCreateCacheWithConcurrencyLevel_thenCreated() {
+        ConcurrentMap<User, Session> sessionCache = new MapMaker().concurrencyLevel(10).makeMap();
+        assertNotNull(sessionCache);
+    }
+
+    @Test
+    public void whenCreateCacheWithWeakKeys_thenCreated() {
+        ConcurrentMap<User, Session> sessionCache = new MapMaker().weakKeys().makeMap();
+        assertNotNull(sessionCache);
+    }
+
+    @Test
+    public void whenCreateCacheWithWeakValues_thenCreated() {
+        ConcurrentMap<User, Profile> profileCache = new MapMaker().weakValues().makeMap();
+        assertNotNull(profileCache);
+    }
+}

java-collections-maps-2/README.md

@@ -13,5 +13,4 @@ This module contains articles about Map data structures in Java.
 - [Sort a HashMap in Java](https://www.baeldung.com/java-hashmap-sort)
 - [Finding the Highest Value in a Java Map](https://www.baeldung.com/java-find-map-max)
 - [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
-- [Java TreeMap vs HashMap](https://www.baeldung.com/java-treemap-vs-hashmap)
-- More articles: [[<-- prev>]](/../java-collections-maps)
+- More articles: [[<-- prev]](/java-collections-maps) [[next -->]](/java-collections-maps-3)

java-collections-maps-3/README.md

@@ -0,0 +1,8 @@
+## Java Collections Cookbooks and Examples
+
+This module contains articles about Map data structures in Java.
+
+### Relevant Articles: 
+- [Java TreeMap vs HashMap](https://www.baeldung.com/java-treemap-vs-hashmap)
+- [Comparing Two HashMaps in Java](https://www.baeldung.com/java-compare-hashmaps)
+- More articles: [[<-- prev]](/java-collections-maps-2)

java-collections-maps-3/pom.xml

@@ -0,0 +1,26 @@
+<?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>java-collections-maps-3</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>java-collections-maps-3</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>
+        
+    </dependencies>
+
+    <properties>
+        
+    </properties>
+
+</project>

java-collections-maps/README.md

@@ -10,8 +10,7 @@ This module contains articles about Map data structures in Java.
 - [How to Store Duplicate Keys in a Map in Java?](https://www.baeldung.com/java-map-duplicate-keys)
 - [Get the Key for a Value from a Java Map](https://www.baeldung.com/java-map-key-from-value)
 - [How to Check If a Key Exists in a Map](https://www.baeldung.com/java-map-key-exists)
-- [Comparing Two HashMaps in Java](https://www.baeldung.com/java-compare-hashmaps)
 - [Immutable Map Implementations in Java](https://www.baeldung.com/java-immutable-maps) 
 - [Guide to Apache Commons MultiValuedMap](https://www.baeldung.com/apache-commons-multi-valued-map)
 - [The Java HashMap Under the Hood](https://www.baeldung.com/java-hashmap-advanced)
-- More articles: [[next -->]](/../java-collections-maps-2)
+- More articles: [[next -->]](/java-collections-maps-2)

java-numbers-3/src/test/java/com/baeldung/abstractnumber/AbstractNumberUnitTest.java

@@ -0,0 +1,52 @@
+package com.baeldung.abstractnumber;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class AbstractNumberUnitTest {
+
+    private final static double DOUBLE_VALUE = 9999.999;
+    private final static float FLOAT_VALUE = 101.99F;
+    private final static long LONG_VALUE = 1000L;
+    private final static int INTEGER_VALUE = 100;
+    private final static short SHORT_VALUE = 127;
+    private final static byte BYTE_VALUE = 120;
+
+    @Test
+    public void givenDoubleValue_whenShortValueUsed_thenShortValueReturned() {
+        Double doubleValue = Double.valueOf(DOUBLE_VALUE);
+        assertEquals(9999, doubleValue.shortValue());
+    }
+
+    @Test
+    public void givenFloatValue_whenByteValueUsed_thenByteValueReturned() {
+        Float floatValue = Float.valueOf(FLOAT_VALUE);
+        assertEquals(101, floatValue.byteValue());
+    }
+
+    @Test
+    public void givenLongValue_whenInitValueUsed_thenInitValueReturned() {
+        Long longValue = Long.valueOf(LONG_VALUE);
+        assertEquals(1000, longValue.intValue());
+    }
+
+    @Test
+    public void givenIntegerValue_whenLongValueUsed_thenLongValueReturned() {
+        Integer integerValue = Integer.valueOf(INTEGER_VALUE);
+        assertEquals(100, integerValue.longValue());
+    }
+
+    @Test
+    public void givenShortValue_whenFloatValueUsed_thenFloatValueReturned() {
+        Short shortValue = Short.valueOf(SHORT_VALUE);
+        assertEquals(127.0F, shortValue.floatValue(), 0);
+    }
+
+    @Test
+    public void givenByteValue_whenDoubleValueUsed_thenDoubleValueReturned() {
+        Byte byteValue = Byte.valueOf(BYTE_VALUE);
+        assertEquals(120.0, byteValue.doubleValue(), 0);
+    }
+
+}

libraries-concurrency/coroutines-with-quasar/pom.xml

@@ -0,0 +1,84 @@
+<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>coroutines-with-quasar</artifactId>
+    <name>coroutines-with-quasar</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>libraries-concurrency</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>co.paralleluniverse</groupId>
+            <artifactId>quasar-core</artifactId>
+            <version>0.8.0</version>
+        </dependency>
+        <dependency>
+            <groupId>co.paralleluniverse</groupId>
+            <artifactId>quasar-actors</artifactId>
+            <version>0.8.0</version>
+        </dependency>
+        <dependency>
+            <groupId>co.paralleluniverse</groupId>
+            <artifactId>quasar-reactive-streams</artifactId>
+            <version>0.8.0</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <version>3.1.2</version>
+                <executions>
+                    <execution>
+                        <id>getClasspathFilenames</id>
+                        <goals>
+                            <goal>properties</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.6.0</version>
+                <configuration>
+                    <mainClass>com.baeldung.quasar.App</mainClass>
+                    <workingDirectory>target/classes</workingDirectory>
+                    <executable>java</executable>
+                    <arguments>
+                        <!-- Turn off before production -->
+                        <argument>-Dco.paralleluniverse.fibers.verifyInstrumentation=true</argument>
+
+                        <!-- Quasar Agent -->
+                        <argument>-javaagent:${co.paralleluniverse:quasar-core:jar}</argument>
+
+                        <!-- Classpath -->
+                        <argument>-classpath</argument>
+                        <classpath />
+
+                        <!-- Main class -->
+                        <argument>com.baeldung.quasar.App</argument>
+                    </arguments>
+                </configuration>
+            </plugin>
+            <plugin>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.0</version>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>12</source>
+                    <target>12</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

libraries-concurrency/coroutines-with-quasar/src/main/java/com/baeldung/quasar/App.java

@@ -0,0 +1,11 @@
+package com.baeldung.quasar;
+
+import co.paralleluniverse.fibers.Fiber;
+
+public class App {
+    public static void main(String[] args) {
+        new Fiber<Void>(() -> {
+            System.out.println("Inside fiber coroutine...");
+        }).start();
+    }
+}

libraries-concurrency/pom.xml

@@ -0,0 +1,20 @@
+<?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>libraries-concurrency</artifactId>
+    <name>libraries-concurrency</name>
+    <packaging>pom</packaging>
+
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <modules>
+        <!-- <module>coroutines-with-quasar</module>  --><!-- we haven't upgraded to Java 12 -->
+    </modules>
+
+</project>

netty/README.md

@@ -0,0 +1,6 @@
+## Netty
+
+This module contains articles about Netty.
+
+### Relevant Articles:
+

netty/pom.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>netty</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>netty</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    
+    <dependencies>
+        <dependency>
+            <groupId>io.netty</groupId>
+            <artifactId>netty-all</artifactId>
+            <version>${netty.version}</version>
+        </dependency>
+
+       <dependency>
+            <groupId>org.conscrypt</groupId>
+            <artifactId>conscrypt-openjdk-uber</artifactId>
+            <version>2.4.0</version>
+        </dependency>
+
+    </dependencies>
+
+    <properties>
+        <netty.version>4.1.48.Final</netty.version>
+    </properties>
+
+</project>

netty/src/main/java/com/baeldung/netty/http2/Http2Util.java

@@ -0,0 +1,135 @@
+package com.baeldung.netty.http2;
+
+import static io.netty.handler.logging.LogLevel.INFO;
+
+import java.security.cert.CertificateException;
+
+import javax.net.ssl.SSLException;
+
+import com.baeldung.netty.http2.client.Http2ClientResponseHandler;
+import com.baeldung.netty.http2.client.Http2SettingsHandler;
+import com.baeldung.netty.http2.server.Http2ServerResponseHandler;
+
+import io.netty.buffer.Unpooled;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPipeline;
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.HttpHeaderNames;
+import io.netty.handler.codec.http.HttpHeaderValues;
+import io.netty.handler.codec.http.HttpMethod;
+import io.netty.handler.codec.http.HttpScheme;
+import io.netty.handler.codec.http.HttpVersion;
+import io.netty.handler.codec.http2.DefaultHttp2Connection;
+import io.netty.handler.codec.http2.DelegatingDecompressorFrameListener;
+import io.netty.handler.codec.http2.Http2Connection;
+import io.netty.handler.codec.http2.Http2FrameCodecBuilder;
+import io.netty.handler.codec.http2.Http2FrameLogger;
+import io.netty.handler.codec.http2.Http2SecurityUtil;
+import io.netty.handler.codec.http2.HttpConversionUtil;
+import io.netty.handler.codec.http2.HttpToHttp2ConnectionHandler;
+import io.netty.handler.codec.http2.HttpToHttp2ConnectionHandlerBuilder;
+import io.netty.handler.codec.http2.InboundHttp2ToHttpAdapterBuilder;
+import io.netty.handler.ssl.ApplicationProtocolConfig;
+import io.netty.handler.ssl.ApplicationProtocolConfig.Protocol;
+import io.netty.handler.ssl.ApplicationProtocolConfig.SelectedListenerFailureBehavior;
+import io.netty.handler.ssl.ApplicationProtocolConfig.SelectorFailureBehavior;
+import io.netty.handler.ssl.ApplicationProtocolNames;
+import io.netty.handler.ssl.ApplicationProtocolNegotiationHandler;
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslContextBuilder;
+import io.netty.handler.ssl.SslProvider;
+import io.netty.handler.ssl.SupportedCipherSuiteFilter;
+import io.netty.handler.ssl.util.InsecureTrustManagerFactory;
+import io.netty.handler.ssl.util.SelfSignedCertificate;
+
+public class Http2Util {
+    public static SslContext createSSLContext(boolean isServer) throws SSLException, CertificateException {
+
+        SslContext sslCtx;
+
+        SelfSignedCertificate ssc = new SelfSignedCertificate();
+
+        if (isServer) {
+            sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey())
+                .sslProvider(SslProvider.JDK)
+                .ciphers(Http2SecurityUtil.CIPHERS, SupportedCipherSuiteFilter.INSTANCE)
+                .applicationProtocolConfig(new ApplicationProtocolConfig(Protocol.ALPN,
+                    SelectorFailureBehavior.NO_ADVERTISE,
+                    SelectedListenerFailureBehavior.ACCEPT, ApplicationProtocolNames.HTTP_2, ApplicationProtocolNames.HTTP_1_1))
+                .build();
+        } else {
+            sslCtx = SslContextBuilder.forClient()
+                .sslProvider(SslProvider.JDK)
+                .ciphers(Http2SecurityUtil.CIPHERS, SupportedCipherSuiteFilter.INSTANCE)
+                .trustManager(InsecureTrustManagerFactory.INSTANCE)
+                .applicationProtocolConfig(new ApplicationProtocolConfig(Protocol.ALPN,
+                    SelectorFailureBehavior.NO_ADVERTISE,
+                    SelectedListenerFailureBehavior.ACCEPT, ApplicationProtocolNames.HTTP_2))
+                .build();
+        }
+        return sslCtx;
+
+    }
+
+    public static ApplicationProtocolNegotiationHandler getServerAPNHandler() {
+        ApplicationProtocolNegotiationHandler serverAPNHandler = new ApplicationProtocolNegotiationHandler(ApplicationProtocolNames.HTTP_2) {
+
+            @Override
+            protected void configurePipeline(ChannelHandlerContext ctx, String protocol) throws Exception {
+                if (ApplicationProtocolNames.HTTP_2.equals(protocol)) {
+                    ctx.pipeline()
+                        .addLast(Http2FrameCodecBuilder.forServer()
+                            .build(), new Http2ServerResponseHandler());
+                    return;
+                }
+                throw new IllegalStateException("Protocol: " + protocol + " not supported");
+            }
+        };
+        return serverAPNHandler;
+
+    }
+
+    public static ApplicationProtocolNegotiationHandler getClientAPNHandler(int maxContentLength, Http2SettingsHandler settingsHandler, Http2ClientResponseHandler responseHandler) {
+        final Http2FrameLogger logger = new Http2FrameLogger(INFO, Http2Util.class);
+        final Http2Connection connection = new DefaultHttp2Connection(false);
+
+        HttpToHttp2ConnectionHandler connectionHandler = new HttpToHttp2ConnectionHandlerBuilder()
+            .frameListener(new DelegatingDecompressorFrameListener(connection, new InboundHttp2ToHttpAdapterBuilder(connection).maxContentLength(maxContentLength)
+            .propagateSettings(true)
+            .build()))
+            .frameLogger(logger)
+            .connection(connection)
+            .build();
+
+        ApplicationProtocolNegotiationHandler clientAPNHandler = new ApplicationProtocolNegotiationHandler(ApplicationProtocolNames.HTTP_2) {
+            @Override
+            protected void configurePipeline(ChannelHandlerContext ctx, String protocol) {
+                if (ApplicationProtocolNames.HTTP_2.equals(protocol)) {
+                    ChannelPipeline p = ctx.pipeline();
+                    p.addLast(connectionHandler);
+                    p.addLast(settingsHandler, responseHandler);
+                    return;
+                }
+                ctx.close();
+                throw new IllegalStateException("Protocol: " + protocol + " not supported");
+            }
+        };
+
+        return clientAPNHandler;
+
+    }
+
+    public static FullHttpRequest createGetRequest(String host, int port) {
+        FullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.valueOf("HTTP/2.0"), HttpMethod.GET, "/", Unpooled.EMPTY_BUFFER);
+        request.headers()
+            .add(HttpHeaderNames.HOST, new String(host + ":" + port));
+        request.headers()
+            .add(HttpConversionUtil.ExtensionHeaderNames.SCHEME.text(), HttpScheme.HTTPS);
+        request.headers()
+            .add(HttpHeaderNames.ACCEPT_ENCODING, HttpHeaderValues.GZIP);
+        request.headers()
+            .add(HttpHeaderNames.ACCEPT_ENCODING, HttpHeaderValues.DEFLATE);
+        return request;
+    }
+}

netty/src/main/java/com/baeldung/netty/http2/client/Http2ClientInitializer.java

@@ -0,0 +1,46 @@
+package com.baeldung.netty.http2.client;
+
+import com.baeldung.netty.http2.Http2Util;
+
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelPipeline;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.handler.ssl.SslContext;
+
+public class Http2ClientInitializer extends ChannelInitializer<SocketChannel> {
+
+    private final SslContext sslCtx;
+    private final int maxContentLength;
+    private Http2SettingsHandler settingsHandler;
+    private Http2ClientResponseHandler responseHandler;
+    private String host;
+    private int port;
+
+    public Http2ClientInitializer(SslContext sslCtx, int maxContentLength, String host, int port) {
+        this.sslCtx = sslCtx;
+        this.maxContentLength = maxContentLength;
+        this.host = host;
+        this.port = port;
+    }
+
+    @Override
+    public void initChannel(SocketChannel ch) throws Exception {
+
+        settingsHandler = new Http2SettingsHandler(ch.newPromise());
+        responseHandler = new Http2ClientResponseHandler();
+        
+        if (sslCtx != null) {
+            ChannelPipeline pipeline = ch.pipeline();
+            pipeline.addLast(sslCtx.newHandler(ch.alloc(), host, port));
+            pipeline.addLast(Http2Util.getClientAPNHandler(maxContentLength, settingsHandler, responseHandler));
+        }
+    }
+
+    public Http2SettingsHandler getSettingsHandler() {
+        return settingsHandler;
+    }
+    
+    public Http2ClientResponseHandler getResponseHandler() {
+        return responseHandler;
+    }
+}

netty/src/main/java/com/baeldung/netty/http2/client/Http2ClientResponseHandler.java

@@ -0,0 +1,128 @@
+package com.baeldung.netty.http2.client;
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.concurrent.TimeUnit;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPromise;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.handler.codec.http.FullHttpResponse;
+import io.netty.handler.codec.http2.HttpConversionUtil;
+import io.netty.util.CharsetUtil;
+
+public class Http2ClientResponseHandler extends SimpleChannelInboundHandler<FullHttpResponse> {
+
+    private final Logger logger = LoggerFactory.getLogger(Http2ClientResponseHandler.class);
+    private final Map<Integer, MapValues> streamidMap;
+
+    public Http2ClientResponseHandler() {
+        streamidMap = new HashMap<Integer, MapValues>();
+    }
+
+    public MapValues put(int streamId, ChannelFuture writeFuture, ChannelPromise promise) {
+        return streamidMap.put(streamId, new MapValues(writeFuture, promise));
+    }
+
+    public String awaitResponses(long timeout, TimeUnit unit) {
+
+        Iterator<Entry<Integer, MapValues>> itr = streamidMap.entrySet()
+            .iterator();
+        
+        String response = null;
+
+        while (itr.hasNext()) {
+            Entry<Integer, MapValues> entry = itr.next();
+            ChannelFuture writeFuture = entry.getValue()
+                .getWriteFuture();
+
+            if (!writeFuture.awaitUninterruptibly(timeout, unit)) {
+                throw new IllegalStateException("Timed out waiting to write for stream id " + entry.getKey());
+            }
+            if (!writeFuture.isSuccess()) {
+                throw new RuntimeException(writeFuture.cause());
+            }
+            ChannelPromise promise = entry.getValue()
+                .getPromise();
+
+            if (!promise.awaitUninterruptibly(timeout, unit)) {
+                throw new IllegalStateException("Timed out waiting for response on stream id " + entry.getKey());
+            }
+            if (!promise.isSuccess()) {
+                throw new RuntimeException(promise.cause());
+            }
+            logger.info("---Stream id: " + entry.getKey() + " received---");
+            response = entry.getValue().getResponse();
+            
+            itr.remove();
+        }
+        
+        return response;
+
+    }
+
+    @Override
+    protected void channelRead0(ChannelHandlerContext ctx, FullHttpResponse msg) throws Exception {
+        Integer streamId = msg.headers()
+            .getInt(HttpConversionUtil.ExtensionHeaderNames.STREAM_ID.text());
+        if (streamId == null) {
+            logger.error("HttpResponseHandler unexpected message received: " + msg);
+            return;
+        }
+
+        MapValues value = streamidMap.get(streamId);
+
+        if (value == null) {
+            logger.error("Message received for unknown stream id " + streamId);
+            ctx.close();
+        } else {
+            ByteBuf content = msg.content();
+            if (content.isReadable()) {
+                int contentLength = content.readableBytes();
+                byte[] arr = new byte[contentLength];
+                content.readBytes(arr);
+                String response = new String(arr, 0, contentLength, CharsetUtil.UTF_8);
+                logger.info("Response from Server: "+ (response));
+                value.setResponse(response);
+            }
+            
+            value.getPromise()
+                .setSuccess();
+        }
+    }
+
+    public static class MapValues {
+        ChannelFuture writeFuture;
+        ChannelPromise promise;
+        String response;
+
+        public String getResponse() {
+            return response;
+        }
+
+        public void setResponse(String response) {
+            this.response = response;
+        }
+
+        public MapValues(ChannelFuture writeFuture2, ChannelPromise promise2) {
+            this.writeFuture = writeFuture2;
+            this.promise = promise2;
+        }
+
+        public ChannelFuture getWriteFuture() {
+            return writeFuture;
+        }
+
+        public ChannelPromise getPromise() {
+            return promise;
+        }
+
+    }
+}

netty/src/main/java/com/baeldung/netty/http2/client/Http2SettingsHandler.java

@@ -0,0 +1,30 @@
+package com.baeldung.netty.http2.client;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPromise;
+import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.handler.codec.http2.Http2Settings;
+
+import java.util.concurrent.TimeUnit;
+
+public class Http2SettingsHandler extends SimpleChannelInboundHandler<Http2Settings> {
+    private final ChannelPromise promise;
+
+    public Http2SettingsHandler(ChannelPromise promise) {
+        this.promise = promise;
+    }
+
+    public void awaitSettings(long timeout, TimeUnit unit) throws Exception {
+        if (!promise.awaitUninterruptibly(timeout, unit)) {
+            throw new IllegalStateException("Timed out waiting for settings");
+        }
+    }
+
+    @Override
+    protected void channelRead0(ChannelHandlerContext ctx, Http2Settings msg) throws Exception {
+        promise.setSuccess();
+
+        ctx.pipeline()
+            .remove(this);
+    }
+}

netty/src/main/java/com/baeldung/netty/http2/server/Http2Server.java

@@ -0,0 +1,59 @@
+package com.baeldung.netty.http2.server;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.baeldung.netty.http2.Http2Util;
+
+import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.channel.socket.nio.NioServerSocketChannel;
+import io.netty.handler.logging.LogLevel;
+import io.netty.handler.logging.LoggingHandler;
+import io.netty.handler.ssl.SslContext;
+
+public final class Http2Server {
+
+    private static final int PORT = 8443;
+    private static final Logger logger = LoggerFactory.getLogger(Http2Server.class);
+
+    public static void main(String[] args) throws Exception {
+        SslContext sslCtx = Http2Util.createSSLContext(true);
+
+        EventLoopGroup group = new NioEventLoopGroup();
+        try {
+            ServerBootstrap b = new ServerBootstrap();
+            b.option(ChannelOption.SO_BACKLOG, 1024);
+            b.group(group)
+                .channel(NioServerSocketChannel.class)
+                .handler(new LoggingHandler(LogLevel.INFO))
+                .childHandler(new ChannelInitializer<SocketChannel>() {
+                    @Override
+                    protected void initChannel(SocketChannel ch) throws Exception {
+                        if (sslCtx != null) {
+                            ch.pipeline()
+                                .addLast(sslCtx.newHandler(ch.alloc()), Http2Util.getServerAPNHandler());
+                        }
+                    }
+
+                });
+
+            Channel ch = b.bind(PORT)
+                .sync()
+                .channel();
+
+            logger.info("HTTP/2 Server is listening on https://127.0.0.1:" + PORT + '/');
+
+            ch.closeFuture()
+                .sync();
+        } finally {
+            group.shutdownGracefully();
+        }
+    }
+
+}

netty/src/main/java/com/baeldung/netty/http2/server/Http2ServerResponseHandler.java

@@ -0,0 +1,52 @@
+package com.baeldung.netty.http2.server;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+import io.netty.channel.ChannelDuplexHandler;
+import io.netty.channel.ChannelHandler.Sharable;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.http.HttpResponseStatus;
+import io.netty.handler.codec.http2.DefaultHttp2DataFrame;
+import io.netty.handler.codec.http2.DefaultHttp2Headers;
+import io.netty.handler.codec.http2.DefaultHttp2HeadersFrame;
+import io.netty.handler.codec.http2.Http2Headers;
+import io.netty.handler.codec.http2.Http2HeadersFrame;
+import io.netty.util.CharsetUtil;
+
+@Sharable
+public class Http2ServerResponseHandler extends ChannelDuplexHandler {
+
+    static final ByteBuf RESPONSE_BYTES = Unpooled.unreleasableBuffer(Unpooled.copiedBuffer("Hello World", CharsetUtil.UTF_8));
+
+    @Override
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
+        super.exceptionCaught(ctx, cause);
+        cause.printStackTrace();
+        ctx.close();
+    }
+
+    @Override
+    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
+        if (msg instanceof Http2HeadersFrame) {
+            Http2HeadersFrame msgHeader = (Http2HeadersFrame) msg;
+            if (msgHeader.isEndStream()) {
+                ByteBuf content = ctx.alloc()
+                    .buffer();
+                content.writeBytes(RESPONSE_BYTES.duplicate());
+
+                Http2Headers headers = new DefaultHttp2Headers().status(HttpResponseStatus.OK.codeAsText());
+                ctx.write(new DefaultHttp2HeadersFrame(headers).stream(msgHeader.stream()));
+                ctx.write(new DefaultHttp2DataFrame(content, true).stream(msgHeader.stream()));
+            }
+
+        } else {
+            super.channelRead(ctx, msg);
+        }
+    }
+
+    @Override
+    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
+        ctx.flush();
+    }
+
+}

netty/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

netty/src/test/java/com/baeldung/netty/Http2ClientLiveTest.java

@@ -0,0 +1,91 @@
+package com.baeldung.netty;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.concurrent.TimeUnit;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.baeldung.netty.http2.Http2Util;
+import com.baeldung.netty.http2.client.Http2ClientInitializer;
+import com.baeldung.netty.http2.client.Http2ClientResponseHandler;
+import com.baeldung.netty.http2.client.Http2SettingsHandler;
+
+import io.netty.bootstrap.Bootstrap;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.nio.NioSocketChannel;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.ssl.SslContext;
+
+//Ensure the server class - Http2Server.java is already started before running this test
+public class Http2ClientLiveTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(Http2ClientLiveTest.class);
+
+    private static final String HOST = "127.0.0.1";
+    private static final int PORT = 8443;
+    private SslContext sslCtx;
+    private Channel channel;
+
+    @Before
+    public void setup() throws Exception {
+        sslCtx = Http2Util.createSSLContext(false);
+    }
+
+    @Test
+    public void whenRequestSent_thenHelloWorldReceived() throws Exception {
+
+        EventLoopGroup workerGroup = new NioEventLoopGroup();
+        Http2ClientInitializer initializer = new Http2ClientInitializer(sslCtx, Integer.MAX_VALUE, HOST, PORT);
+
+        try {
+            Bootstrap b = new Bootstrap();
+            b.group(workerGroup);
+            b.channel(NioSocketChannel.class);
+            b.option(ChannelOption.SO_KEEPALIVE, true);
+            b.remoteAddress(HOST, PORT);
+            b.handler(initializer);
+
+            channel = b.connect()
+                .syncUninterruptibly()
+                .channel();
+
+            logger.info("Connected to [" + HOST + ':' + PORT + ']');
+
+            Http2SettingsHandler http2SettingsHandler = initializer.getSettingsHandler();
+            http2SettingsHandler.awaitSettings(60, TimeUnit.SECONDS);
+
+            logger.info("Sending request(s)...");
+
+            FullHttpRequest request = Http2Util.createGetRequest(HOST, PORT);
+
+            Http2ClientResponseHandler responseHandler = initializer.getResponseHandler();
+            int streamId = 3;
+
+            responseHandler.put(streamId, channel.write(request), channel.newPromise());
+            channel.flush();
+            String response = responseHandler.awaitResponses(60, TimeUnit.SECONDS);
+
+            assertEquals("Hello World", response);
+
+            logger.info("Finished HTTP/2 request(s)");
+
+        } finally {
+            workerGroup.shutdownGracefully();
+        }
+
+    }
+
+    @After
+    public void cleanup() {
+        channel.close()
+            .syncUninterruptibly();
+    }
+}

parent-boot-2/pom.xml

@@ -81,7 +81,7 @@
         <rest-assured.version>3.3.0</rest-assured.version>
         <!-- plugins -->
         <thin.version>1.0.22.RELEASE</thin.version>
-        <spring-boot.version>2.2.2.RELEASE</spring-boot.version>
+        <spring-boot.version>2.2.6.RELEASE</spring-boot.version>
     </properties>
 
 </project>

parent-spring-5/pom.xml

@@ -31,8 +31,8 @@
     </dependencies>
 
     <properties>
-        <spring.version>5.2.2.RELEASE</spring.version>
-        <spring-security.version>5.2.1.RELEASE</spring-security.version>
+        <spring.version>5.2.5.RELEASE</spring.version>
+        <spring-security.version>5.2.3.RELEASE</spring-security.version>
     </properties>
 
 </project>

pom.xml

@@ -455,6 +455,7 @@
                 <module>java-collections-conversions-2</module>
                 <module>java-collections-maps</module>
                 <module>java-collections-maps-2</module>
+                <module>java-collections-maps-3</module>
                 <!-- <module>java-ee-8-security-api</module> --> <!-- long running -->
 
                 <module>javafx</module>
@@ -535,6 +536,7 @@
                 <module>mybatis</module>
 
                 <module>netflix-modules</module>
+                <!-- <module>netty</module> --> <!-- we haven't upgraded to Java 13 -->
                 <module>ninja</module>
                 <module>open-liberty</module>
 
@@ -966,6 +968,7 @@
                 <module>java-collections-conversions-2</module>
                 <module>java-collections-maps</module>
                 <module>java-collections-maps-2</module>
+                <module>java-collections-maps-3</module>
                 <!-- <module>java-ee-8-security-api</module> --> <!-- long running -->
 
                 <module>javafx</module>
@@ -1045,6 +1048,7 @@
                 <module>mybatis</module>
 
                 <module>netflix-modules</module>
+                <!-- <module>netty</module> --> <!-- we haven't upgraded to Java 13 -->
                 <module>ninja</module>
                 <module>open-liberty</module>
 
@@ -1261,6 +1265,7 @@
                 <module>wildfly</module>
                 <module>xml</module>
                 <module>xstream</module>
+                <module>libraries-concurrency</module>
             </modules>
 
         </profile>

spring-batch/src/main/java/org/baeldung/conditionalflow/ConditionalFlowApplication.java

@@ -0,0 +1,21 @@
+package org.baeldung.conditionalflow;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class ConditionalFlowApplication implements CommandLineRunner {
+    private static Logger logger = LoggerFactory.getLogger(ConditionalFlowApplication.class);
+
+    public static void main(String[] args) {
+        SpringApplication.run(ConditionalFlowApplication.class, args);
+    }
+
+    @Override
+    public void run(String... args) throws Exception {
+        logger.info("Running conditional flow application...");
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/NumberInfoDecider.java

@@ -0,0 +1,29 @@
+package org.baeldung.conditionalflow;
+
+import org.springframework.batch.core.JobExecution;
+import org.springframework.batch.core.StepExecution;
+import org.springframework.batch.core.job.flow.FlowExecutionStatus;
+import org.springframework.batch.core.job.flow.JobExecutionDecider;
+
+public class NumberInfoDecider implements JobExecutionDecider {
+
+    public static final String NOTIFY = "NOTIFY";
+    public static final String QUIET = "QUIET";
+
+    /**
+     * Method that determines notification status of job
+     * @return true if notifications should be sent.
+     */
+    private boolean shouldNotify() {
+        return true;
+    }
+
+    @Override
+    public FlowExecutionStatus decide(JobExecution jobExecution, StepExecution stepExecution) {
+        if (shouldNotify()) {
+            return new FlowExecutionStatus(NOTIFY);
+        } else {
+            return new FlowExecutionStatus(QUIET);
+        }
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/config/NumberInfoConfig.java

@@ -0,0 +1,91 @@
+package org.baeldung.conditionalflow.config;
+
+import org.baeldung.conditionalflow.NumberInfoDecider;
+import org.baeldung.conditionalflow.model.NumberInfo;
+import org.baeldung.conditionalflow.step.*;
+import org.springframework.batch.core.Job;
+import org.springframework.batch.core.Step;
+import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
+import org.springframework.batch.core.configuration.annotation.JobBuilderFactory;
+import org.springframework.batch.core.configuration.annotation.StepBuilderFactory;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Primary;
+
+import static org.baeldung.conditionalflow.NumberInfoDecider.NOTIFY;
+
+@Configuration
+@EnableBatchProcessing
+public class NumberInfoConfig {
+
+    @Bean
+    @Qualifier("NotificationStep")
+    public Step notificationStep(StepBuilderFactory sbf) {
+        return sbf.get("Notify step")
+            .tasklet(new NotifierTasklet())
+            .build();
+    }
+
+    public Step numberGeneratorStep(StepBuilderFactory sbf, int[] values, String prepend) {
+        return sbf.get("Number generator")
+            .<NumberInfo, Integer> chunk(1)
+            .reader(new NumberInfoGenerator(values))
+            .processor(new NumberInfoClassifier())
+            .writer(new PrependingStdoutWriter<>(prepend))
+            .build();
+    }
+
+    public Step numberGeneratorStepDecider(StepBuilderFactory sbf, int[] values, String prepend) {
+        return sbf.get("Number generator decider")
+            .<NumberInfo, Integer> chunk(1)
+            .reader(new NumberInfoGenerator(values))
+            .processor(new NumberInfoClassifierWithDecider())
+            .writer(new PrependingStdoutWriter<>(prepend))
+            .build();
+    }
+
+    @Bean
+    @Qualifier("first_job")
+    public Job numberGeneratorNonNotifierJob(JobBuilderFactory jobBuilderFactory, StepBuilderFactory stepBuilderFactory, @Qualifier("NotificationStep") Step notificationStep) {
+        int[] nonNotifierData = { -1, -2, -3 };
+        Step step = numberGeneratorStep(stepBuilderFactory, nonNotifierData, "First Dataset Processor");
+        return jobBuilderFactory.get("Number generator - first dataset")
+            .start(step)
+            .on(NOTIFY)
+            .to(notificationStep)
+            .from(step)
+            .on("*")
+            .stop()
+            .end()
+            .build();
+    }
+
+    @Bean
+    @Qualifier("second_job")
+    public Job numberGeneratorNotifierJob(JobBuilderFactory jobBuilderFactory, StepBuilderFactory stepBuilderFactory, @Qualifier("NotificationStep") Step notificationStep) {
+        int[] billableData = { 11, -2, -3 };
+        Step dataProviderStep = numberGeneratorStep(stepBuilderFactory, billableData, "Second Dataset Processor");
+        return jobBuilderFactory.get("Number generator - second dataset")
+            .start(dataProviderStep)
+            .on(NOTIFY)
+            .to(notificationStep)
+            .end()
+            .build();
+    }
+
+    @Bean
+    @Qualifier("third_job")
+    @Primary
+    public Job numberGeneratorNotifierJobWithDecider(JobBuilderFactory jobBuilderFactory, StepBuilderFactory stepBuilderFactory, @Qualifier("NotificationStep") Step notificationStep) {
+        int[] billableData = { 11, -2, -3 };
+        Step dataProviderStep = numberGeneratorStepDecider(stepBuilderFactory, billableData, "Third Dataset Processor");
+        return jobBuilderFactory.get("Number generator - third dataset")
+            .start(dataProviderStep)
+            .next(new NumberInfoDecider())
+            .on(NOTIFY)
+            .to(notificationStep)
+            .end()
+            .build();
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/model/NumberInfo.java

@@ -0,0 +1,47 @@
+package org.baeldung.conditionalflow.model;
+
+import java.util.Objects;
+
+public class NumberInfo {
+    private int number;
+
+    public NumberInfo(int number) {
+        this.number = number;
+    }
+
+    public static NumberInfo from(int number) {
+        return new NumberInfo(number);
+    }
+
+    public boolean isPositive() {
+        return number > 0;
+    }
+
+    public boolean isEven() {
+        return number % 2 == 0;
+    }
+
+    public int getNumber() {
+        return number;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        NumberInfo that = (NumberInfo) o;
+        return number == that.number;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(number);
+    }
+
+    @Override
+    public String toString() {
+        return "NumberInfo{" + "number=" + number + '}';
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/step/NotifierTasklet.java

@@ -0,0 +1,15 @@
+package org.baeldung.conditionalflow.step;
+
+import org.springframework.batch.core.StepContribution;
+import org.springframework.batch.core.scope.context.ChunkContext;
+import org.springframework.batch.core.step.tasklet.Tasklet;
+import org.springframework.batch.repeat.RepeatStatus;
+
+public class NotifierTasklet implements Tasklet {
+    @Override
+    public RepeatStatus execute(StepContribution stepContribution, ChunkContext chunkContext) throws Exception {
+        System.err.println("[" + chunkContext.getStepContext()
+            .getJobName() + "] contains interesting data!!");
+        return RepeatStatus.FINISHED;
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/step/NumberInfoClassifier.java

@@ -0,0 +1,35 @@
+package org.baeldung.conditionalflow.step;
+
+import org.baeldung.conditionalflow.model.NumberInfo;
+import org.springframework.batch.core.ExitStatus;
+import org.springframework.batch.core.StepExecution;
+import org.springframework.batch.core.annotation.BeforeStep;
+import org.springframework.batch.core.listener.ItemListenerSupport;
+import org.springframework.batch.item.ItemProcessor;
+
+import static org.baeldung.conditionalflow.NumberInfoDecider.NOTIFY;
+import static org.baeldung.conditionalflow.NumberInfoDecider.QUIET;
+
+public class NumberInfoClassifier extends ItemListenerSupport<NumberInfo, Integer>
+        implements ItemProcessor<NumberInfo, Integer> {
+    private StepExecution stepExecution;
+
+    @BeforeStep
+    public void beforeStep(StepExecution stepExecution) {
+        this.stepExecution = stepExecution;
+        this.stepExecution.setExitStatus(new ExitStatus(QUIET));
+    }
+
+    @Override
+    public void afterProcess(NumberInfo item, Integer result) {
+        super.afterProcess(item, result);
+        if (item.isPositive()) {
+            stepExecution.setExitStatus(new ExitStatus(NOTIFY));
+        }
+    }
+
+    @Override
+    public Integer process(NumberInfo numberInfo) throws Exception {
+        return Integer.valueOf(numberInfo.getNumber());
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/step/NumberInfoClassifierWithDecider.java

@@ -0,0 +1,13 @@
+package org.baeldung.conditionalflow.step;
+
+import org.baeldung.conditionalflow.model.NumberInfo;
+import org.springframework.batch.core.listener.ItemListenerSupport;
+import org.springframework.batch.item.ItemProcessor;
+
+public class NumberInfoClassifierWithDecider extends ItemListenerSupport<NumberInfo, Integer> implements ItemProcessor<NumberInfo, Integer> {
+
+    @Override
+    public Integer process(NumberInfo numberInfo) throws Exception {
+        return Integer.valueOf(numberInfo.getNumber());
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/step/NumberInfoGenerator.java

@@ -0,0 +1,23 @@
+package org.baeldung.conditionalflow.step;
+
+import org.baeldung.conditionalflow.model.NumberInfo;
+import org.springframework.batch.item.ItemReader;
+
+public class NumberInfoGenerator implements ItemReader<NumberInfo> {
+    private int[] values;
+    private int counter;
+
+    public NumberInfoGenerator(int[] values) {
+        this.values = values;
+        counter = 0;
+    }
+
+    @Override
+    public NumberInfo read() {
+        if (counter == values.length) {
+            return null;
+        } else {
+            return new NumberInfo(values[counter++]);
+        }
+    }
+}

spring-batch/src/main/java/org/baeldung/conditionalflow/step/PrependingStdoutWriter.java

@@ -0,0 +1,20 @@
+package org.baeldung.conditionalflow.step;
+
+import java.util.List;
+
+import org.springframework.batch.item.ItemWriter;
+
+public class PrependingStdoutWriter<T> implements ItemWriter<T> {
+    private String prependText;
+
+    public PrependingStdoutWriter(String prependText) {
+        this.prependText = prependText;
+    }
+
+    @Override
+    public void write(List<? extends T> list) {
+        for (T listItem : list) {
+            System.out.println(prependText + " " + listItem.toString());
+        }
+    }
+}

spring-batch/src/test/java/org/baeldung/conditionalflow/DeciderJobIntegrationTest.java

@@ -0,0 +1,56 @@
+package org.baeldung.conditionalflow;
+
+import org.baeldung.conditionalflow.config.NumberInfoConfig;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.batch.core.ExitStatus;
+import org.springframework.batch.core.JobExecution;
+import org.springframework.batch.core.StepExecution;
+import org.springframework.batch.test.JobLauncherTestUtils;
+import org.springframework.batch.test.context.SpringBatchTest;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.TestExecutionListeners;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.context.support.DependencyInjectionTestExecutionListener;
+import org.springframework.test.context.support.DirtiesContextTestExecutionListener;
+
+import java.util.Collection;
+import java.util.Iterator;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+@RunWith(SpringRunner.class)
+@SpringBatchTest
+@EnableAutoConfiguration
+@ContextConfiguration(classes = { NumberInfoConfig.class })
+@TestExecutionListeners({ DependencyInjectionTestExecutionListener.class, DirtiesContextTestExecutionListener.class })
+@DirtiesContext(classMode = DirtiesContext.ClassMode.AFTER_CLASS)
+public class DeciderJobIntegrationTest {
+    @Autowired
+    private JobLauncherTestUtils jobLauncherTestUtils;
+
+    @Test
+    public void givenNumberGeneratorDecider_whenDeciderRuns_thenStatusIsNotify() throws Exception {
+        JobExecution jobExecution = jobLauncherTestUtils.launchJob();
+        Collection<StepExecution> actualStepExecutions = jobExecution.getStepExecutions();
+        ExitStatus actualJobExitStatus = jobExecution.getExitStatus();
+
+        assertEquals("COMPLETED", actualJobExitStatus.getExitCode()
+            .toString());
+        assertEquals(2, actualStepExecutions.size());
+        boolean notifyStepDidRun = false;
+        Iterator<StepExecution> iterator = actualStepExecutions.iterator();
+        while (iterator.hasNext() && !notifyStepDidRun) {
+            if (iterator.next()
+                .getStepName()
+                .equals("Notify step")) {
+                notifyStepDidRun = true;
+            }
+        }
+        assertTrue(notifyStepDidRun);
+    }
+}

spring-batch/src/test/java/org/baeldung/conditionalflow/model/NumberInfoUnitTest.java

@@ -0,0 +1,71 @@
+package org.baeldung.conditionalflow.model;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+import org.junit.runner.RunWith;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+class NumberInfoUnitTest {
+
+    @Test
+    void givenPositive_whenFrom_isPositive() {
+        assertTrue(NumberInfo.from(1)
+            .isPositive());
+        assertTrue(NumberInfo.from(11)
+            .isPositive());
+        assertFalse(NumberInfo.from(0)
+            .isPositive());
+    }
+
+    @Test
+    void givenNegative_whenFrom_isNegative() {
+        assertFalse(NumberInfo.from(-1)
+            .isPositive());
+        assertFalse(NumberInfo.from(-10)
+            .isPositive());
+    }
+
+    @Test
+    void givenEven_whenFrom_isEven() {
+        assertTrue(NumberInfo.from(0)
+            .isEven());
+        assertTrue(NumberInfo.from(-2)
+            .isEven());
+        assertTrue(NumberInfo.from(2)
+            .isEven());
+        assertTrue(NumberInfo.from(-22)
+            .isEven());
+        assertTrue(NumberInfo.from(22)
+            .isEven());
+    }
+
+    @Test
+    void givenOdd_whenFrom_isOdd() {
+
+        assertFalse(NumberInfo.from(1)
+            .isEven());
+        assertFalse(NumberInfo.from(-1)
+            .isEven());
+
+        assertFalse(NumberInfo.from(13)
+            .isEven());
+        assertFalse(NumberInfo.from(-13)
+            .isEven());
+        assertFalse(NumberInfo.from(31)
+            .isEven());
+        assertFalse(NumberInfo.from(-51)
+            .isEven());
+    }
+
+    @Test
+    void giveGeneratedInt_whenFrom_isNumberFromGenerator() {
+        for (int i = -100; i < 100; i++) {
+            assertEquals(i, NumberInfo.from(i)
+                .getNumber());
+        }
+    }
+}

spring-batch/src/test/java/org/baeldung/conditionalflow/step/NumberInfoClassifierUnitTest.java

@@ -0,0 +1,16 @@
+package org.baeldung.conditionalflow.step;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.baeldung.conditionalflow.model.NumberInfo;
+import org.junit.jupiter.api.Test;
+
+class NumberInfoClassifierUnitTest {
+
+    @Test
+    void givenNumberInfo_whenProcess_thenConvertsToInteger() throws Exception {
+        NumberInfoClassifier nic = new NumberInfoClassifier();
+        assertEquals(Integer.valueOf(4), nic.process(NumberInfo.from(4)));
+        assertEquals(Integer.valueOf(-4), nic.process(NumberInfo.from(-4)));
+    }
+}

spring-batch/src/test/java/org/baeldung/conditionalflow/step/NumberInfoGeneratorUnitTest.java

@@ -0,0 +1,21 @@
+package org.baeldung.conditionalflow.step;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import org.baeldung.conditionalflow.model.NumberInfo;
+import org.junit.jupiter.api.Test;
+
+public class NumberInfoGeneratorUnitTest {
+
+    @Test
+    public void givenArray_whenGenerator_correctOrderAndValue() {
+        int[] numbers = new int[] { 1, -2, 4, -10 };
+        NumberInfoGenerator numberGenerator = new NumberInfoGenerator(numbers);
+        assertEquals(new NumberInfo(numbers[0]), numberGenerator.read());
+        assertEquals(new NumberInfo(numbers[1]), numberGenerator.read());
+        assertEquals(new NumberInfo(numbers[2]), numberGenerator.read());
+        assertEquals(new NumberInfo(numbers[3]), numberGenerator.read());
+        assertNull(numberGenerator.read());
+    }
+}

spring-boot-modules/spring-boot-admin/spring-boot-admin-client/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-admin/spring-boot-admin-server/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-angular/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-artifacts/pom.xml

@@ -208,7 +208,7 @@
 
     <properties>
         <!-- The main class to start by executing java -jar -->
-        <start-class>org.baeldung.boot.Application</start-class>
+        <start-class>com.baeldung.boot.Application</start-class>
         <jquery.version>3.1.1</jquery.version>
         <bootstrap.version>3.3.7-1</bootstrap.version>
         <jpa.version>2.2</jpa.version>

spring-boot-modules/spring-boot-camel/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-client/src/main/java/com/baeldung/boot/Application.java

@@ -1,4 +1,4 @@
-package org.baeldung.boot;
+package com.baeldung.boot;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;

spring-boot-modules/spring-boot-client/src/main/java/com/baeldung/boot/client/Details.java

@@ -1,4 +1,4 @@
-package org.baeldung.boot.client;
+package com.baeldung.boot.client;
 
 public class Details {
 

spring-boot-modules/spring-boot-client/src/main/java/com/baeldung/boot/client/DetailsServiceClient.java

@@ -1,4 +1,4 @@
-package org.baeldung.boot.client;
+package com.baeldung.boot.client;
 
 import org.springframework.boot.web.client.RestTemplateBuilder;
 import org.springframework.stereotype.Service;

spring-boot-modules/spring-boot-client/src/main/java/com/baeldung/websocket/client/Message.java

@@ -1,4 +1,4 @@
-package org.baeldung.websocket.client;
+package com.baeldung.websocket.client;
 
 public class Message {
 

spring-boot-modules/spring-boot-client/src/main/java/com/baeldung/websocket/client/MyStompSessionHandler.java

@@ -1,4 +1,4 @@
-package org.baeldung.websocket.client;
+package com.baeldung.websocket.client;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;

spring-boot-modules/spring-boot-client/src/main/java/com/baeldung/websocket/client/StompClient.java

@@ -1,4 +1,4 @@
-package org.baeldung.websocket.client;
+package com.baeldung.websocket.client;
 
 import java.util.Scanner;
 

spring-boot-modules/spring-boot-client/src/test/java/com/baeldung/SpringContextTest.java

@@ -1,6 +1,6 @@
-package org.baeldung;
+package com.baeldung;
 
-import org.baeldung.boot.Application;
+import com.baeldung.boot.Application;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.springframework.boot.test.context.SpringBootTest;

spring-boot-modules/spring-boot-client/src/test/java/com/baeldung/boot/client/DetailsServiceClientIntegrationTest.java

@@ -1,10 +1,12 @@
-package org.baeldung.boot.client;
+package com.baeldung.boot.client;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.client.match.MockRestRequestMatchers.requestTo;
 import static org.springframework.test.web.client.response.MockRestResponseCreators.withSuccess;
 
-import org.baeldung.boot.Application;
+import com.baeldung.boot.Application;
+import com.baeldung.boot.client.Details;
+import com.baeldung.boot.client.DetailsServiceClient;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-client/src/test/java/com/baeldung/websocket/client/MyStompSessionHandlerIntegrationTest.java

@@ -1,6 +1,5 @@
 package com.baeldung.websocket.client;
 
-import org.baeldung.websocket.client.MyStompSessionHandler;
 import org.junit.Test;
 import org.mockito.Mockito;
 import org.springframework.messaging.simp.stomp.StompHeaders;

spring-boot-modules/spring-boot-ctx-fluent/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 

spring-boot-modules/spring-boot-custom-starter/greeter-spring-boot-autoconfigure/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-custom-starter/greeter-spring-boot-sample-app/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-deployment/pom.xml

@@ -190,7 +190,7 @@
 
     <properties>
         <!-- The main class to start by executing java -jar -->
-        <start-class>org.baeldung.boot.Application</start-class>
+        <start-class>com.baeldung.boot.Application</start-class>
         <jquery.version>3.1.1</jquery.version>
         <bootstrap.version>3.3.7-1</bootstrap.version>
         <jpa.version>2.2</jpa.version>

spring-boot-modules/spring-boot-gradle/build.gradle

@@ -21,7 +21,7 @@ apply plugin: 'io.spring.dependency-management'
 //add tasks thinJar and thinResolve for thin JAR deployments
 apply plugin: 'org.springframework.boot.experimental.thin-launcher'
 
-group = 'org.baeldung'
+group = 'com.baeldung'
 version = '0.0.1-SNAPSHOT'
 sourceCompatibility = 1.8
 
@@ -35,16 +35,16 @@ dependencies {
 }
 
 springBoot {
-    mainClassName = 'org.baeldung.DemoApplication'
+    mainClassName = 'com.baeldung.DemoApplication'
 }
 
 bootJar {
 //    This is overridden by the mainClassName in springBoot{} and added here for reference purposes.
-    mainClassName = 'org.baeldung.DemoApplication'
+    mainClassName = 'com.baeldung.DemoApplication'
 
 //    This block serves the same purpose as the above thus commented out. Added here for reference purposes
 //    manifest {
-//        attributes 'Start-Class': 'org.baeldung.DemoApplication'
+//        attributes 'Start-Class': 'com.baeldung.DemoApplication'
 //    }
 }
 

spring-boot-modules/spring-boot-gradle/src/main/java/com/baeldung/DemoApplication.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;

spring-boot-modules/spring-boot-gradle/src/test/java/com/baeldung/DemoApplicationTests.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-jasypt/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-keycloak/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-logging-log4j2/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-mvc/src/test/java/org/baeldung/SpringContextLiveTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-mvc/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-properties/src/main/java/com/baeldung/properties/external/ExternalPropertiesWithJavaConfig.java

@@ -7,7 +7,7 @@ import org.springframework.context.annotation.PropertySource;
 import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
 
 @Configuration
-@ComponentScan("org.baeldung.properties.core")
+@ComponentScan("com.baeldung.properties.core")
 @PropertySource("classpath:foo.properties")
 public class ExternalPropertiesWithJavaConfig {
 

spring-boot-modules/spring-boot-properties/src/main/java/com/baeldung/properties/external/ExternalPropertiesWithXmlConfig.java

@@ -6,7 +6,7 @@ import org.springframework.context.annotation.ImportResource;
 
 @Configuration
 @ImportResource("classpath:configForProperties.xml")
-@ComponentScan("org.baeldung.core")
+@ComponentScan("com.baeldung.core")
 public class ExternalPropertiesWithXmlConfig {
 
     public ExternalPropertiesWithXmlConfig() {

spring-boot-modules/spring-boot-properties/src/main/java/com/baeldung/properties/external/ExternalPropertiesWithXmlConfigOne.java

@@ -6,7 +6,7 @@ import org.springframework.context.annotation.ImportResource;
 
 @Configuration
 @ImportResource("classpath:configForPropertiesOne.xml")
-@ComponentScan("org.baeldung.core")
+@ComponentScan("com.baeldung.core")
 public class ExternalPropertiesWithXmlConfigOne {
 
     public ExternalPropertiesWithXmlConfigOne() {

spring-boot-modules/spring-boot-property-exp/property-exp-custom-config/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-property-exp/property-exp-default-config/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot-vue/src/test/java/org/baeldung/SpringContextTest.java

@@ -1,4 +1,4 @@
-package org.baeldung;
+package com.baeldung;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

spring-boot-modules/spring-boot/src/main/java/com/baeldung/boot/Application.java

@@ -1,4 +1,4 @@
-package org.baeldung.boot;
+package com.baeldung.boot;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;