Merge remote-tracking branch 'upstream/master'

.travis.yml

@@ -4,7 +4,7 @@ before_install:
   - echo "MAVEN_OPTS='-Xmx2048M -Xss128M -XX:+CMSClassUnloadingEnabled -XX:+UseG1GC -XX:-UseGCOverheadLimit'" > ~/.mavenrc
 
 install: skip
-script: travis_wait 60 mvn -q install -Pdefault
+script: travis_wait 60 mvn -q install -Pdefault-first,default-second
 
 sudo: required
 

README.md

@@ -26,3 +26,13 @@ To do the full build, do: `mvn install -Pdefault -Dgib.enabled=false`
 Building a single module
 ====================
 To build a specific module run the command: `mvn clean install -Dgib.enabled=false` in the module directory
+
+
+Running a Spring Boot module
+====================
+To run a Spring Boot module run the command: `mvn spring-boot:run -Dgib.enabled=false` in the module directory
+
+
+
+
+

algorithms/README.md

@@ -28,3 +28,6 @@
 - [Calculate the Distance Between Two Points in Java](https://www.baeldung.com/java-distance-between-two-points)
 - [Find the Intersection of Two Lines in Java](https://www.baeldung.com/java-intersection-of-two-lines)
 - [Check If a String Contains All The Letters of The Alphabet](https://www.baeldung.com/java-string-contains-all-letters)
+- [Round Up to the Nearest Hundred](https://www.baeldung.com/java-round-up-nearest-hundred)
+- [Merge Sort in Java](https://www.baeldung.com/java-merge-sort)
+- [Calculate Percentage in Java](https://www.baeldung.com/java-calculate-percentage)

algorithms/pom.xml

@@ -17,6 +17,11 @@
             <artifactId>commons-math3</artifactId>
             <version>${commons-math3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>${commons-codec.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
@@ -85,6 +90,7 @@
         <io.jenetics.version>3.7.0</io.jenetics.version>
         <org.jgrapht.core.version>1.0.1</org.jgrapht.core.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
+        <commons-codec.version>1.11</commons-codec.version>
     </properties>
 
 </project>

algorithms/src/main/java/com/baeldung/algorithms/conversion/HexStringConverter.java

@@ -0,0 +1,110 @@
+package com.baeldung.algorithms.conversion;
+
+import java.math.BigInteger;
+
+import javax.xml.bind.DatatypeConverter;
+
+import org.apache.commons.codec.DecoderException;
+import org.apache.commons.codec.binary.Hex;
+
+import com.google.common.io.BaseEncoding;
+
+public class HexStringConverter {
+
+    /**
+     * Create a byte Array from String of hexadecimal digits using Character conversion 
+     * @param hexString - Hexadecimal digits as String
+     * @return Desired byte Array
+     */
+    public byte[] decodeHexString(String hexString) {
+        if (hexString.length() % 2 == 1) {
+            throw new IllegalArgumentException("Invalid hexadecimal String supplied.");
+        }
+        byte[] bytes = new byte[hexString.length() / 2];
+
+        for (int i = 0; i < hexString.length(); i += 2) {
+            bytes[i / 2] = hexToByte(hexString.substring(i, i + 2));
+        }
+        return bytes;
+    }
+
+    /**
+     * Create a String of hexadecimal digits from a byte Array using Character conversion
+     * @param byteArray - The byte Array
+     * @return Desired String of hexadecimal digits in lower case
+     */
+    public String encodeHexString(byte[] byteArray) {
+        StringBuffer hexStringBuffer = new StringBuffer();
+        for (int i = 0; i < byteArray.length; i++) {
+            hexStringBuffer.append(byteToHex(byteArray[i]));
+        }
+        return hexStringBuffer.toString();
+    }
+
+    public String byteToHex(byte num) {
+        char[] hexDigits = new char[2];
+        hexDigits[0] = Character.forDigit((num >> 4) & 0xF, 16);
+        hexDigits[1] = Character.forDigit((num & 0xF), 16);
+        return new String(hexDigits);
+    }
+
+    public byte hexToByte(String hexString) {
+        int firstDigit = toDigit(hexString.charAt(0));
+        int secondDigit = toDigit(hexString.charAt(1));
+        return (byte) ((firstDigit << 4) + secondDigit);
+    }
+
+    private int toDigit(char hexChar) {
+        int digit = Character.digit(hexChar, 16);
+        if(digit == -1) {
+            throw new IllegalArgumentException("Invalid Hexadecimal Character: "+ hexChar);
+        }
+        return digit;
+    }
+
+    public String encodeUsingBigIntegerToString(byte[] bytes) {
+        BigInteger bigInteger = new BigInteger(1, bytes);
+        return bigInteger.toString(16);
+    }
+
+    public String encodeUsingBigIntegerStringFormat(byte[] bytes) {
+        BigInteger bigInteger = new BigInteger(1, bytes);
+        return String.format("%0" + (bytes.length << 1) + "x", bigInteger);
+    }
+
+    public byte[] decodeUsingBigInteger(String hexString) {
+        byte[] byteArray = new BigInteger(hexString, 16).toByteArray();
+        if (byteArray[0] == 0) {
+            byte[] output = new byte[byteArray.length - 1];
+            System.arraycopy(byteArray, 1, output, 0, output.length);
+            return output;
+        }
+        return byteArray;
+    }
+
+    public String encodeUsingDataTypeConverter(byte[] bytes) {
+        return DatatypeConverter.printHexBinary(bytes);
+    }
+
+    public byte[] decodeUsingDataTypeConverter(String hexString) {
+        return DatatypeConverter.parseHexBinary(hexString);
+    }
+
+    public String encodeUsingApacheCommons(byte[] bytes) throws DecoderException {
+        return Hex.encodeHexString(bytes);
+    }
+
+    public byte[] decodeUsingApacheCommons(String hexString) throws DecoderException {
+        return Hex.decodeHex(hexString);
+    }
+
+    public String encodeUsingGuava(byte[] bytes) {
+        return BaseEncoding.base16()
+            .encode(bytes);
+    }
+
+    public byte[] decodeUsingGuava(String hexString) {
+        return BaseEncoding.base16()
+            .decode(hexString.toUpperCase());
+    }
+}

algorithms/src/main/java/com/baeldung/algorithms/heapsort/Heap.java

@@ -0,0 +1,136 @@
+package com.baeldung.algorithms.heapsort;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Heap<E extends Comparable<E>> {
+
+    private List<E> elements = new ArrayList<>();
+
+    public static <E extends Comparable<E>> List<E> sort(Iterable<E> elements) {
+        Heap<E> heap = of(elements);
+
+        List<E> result = new ArrayList<>();
+
+        while (!heap.isEmpty()) {
+            result.add(heap.pop());
+        }
+
+        return result;
+    }
+
+    public static <E extends Comparable<E>> Heap<E> of(E... elements) {
+        return of(Arrays.asList(elements));
+    }
+
+    public static <E extends Comparable<E>> Heap<E> of(Iterable<E> elements) {
+        Heap<E> result = new Heap<>();
+        for (E element : elements) {
+            result.add(element);
+        }
+        return result;
+    }
+
+    public void add(E e) {
+        elements.add(e);
+        int elementIndex = elements.size() - 1;
+        while (!isRoot(elementIndex) && !isCorrectChild(elementIndex)) {
+            int parentIndex = parentIndex(elementIndex);
+            swap(elementIndex, parentIndex);
+            elementIndex = parentIndex;
+        }
+    }
+
+    public E pop() {
+        if (isEmpty()) {
+            throw new IllegalStateException("You cannot pop from an empty heap");
+        }
+
+        E result = elementAt(0);
+
+        int lasElementIndex = elements.size() - 1;
+        swap(0, lasElementIndex);
+        elements.remove(lasElementIndex);
+
+        int elementIndex = 0;
+        while (!isLeaf(elementIndex) && !isCorrectParent(elementIndex)) {
+            int smallerChildIndex = smallerChildIndex(elementIndex);
+            swap(elementIndex, smallerChildIndex);
+            elementIndex = smallerChildIndex;
+        }
+
+        return result;
+    }
+
+    public boolean isEmpty() {
+        return elements.isEmpty();
+    }
+    
+    private boolean isRoot(int index) {
+        return index == 0;
+    }
+
+    private int smallerChildIndex(int index) {
+        int leftChildIndex = leftChildIndex(index);
+        int rightChildIndex = rightChildIndex(index);
+        
+        if (!isValidIndex(rightChildIndex)) {
+            return leftChildIndex;
+        }
+
+        if (elementAt(leftChildIndex).compareTo(elementAt(rightChildIndex)) < 0) {
+            return leftChildIndex;
+        }
+
+        return rightChildIndex;
+    }
+
+    private boolean isLeaf(int index) {
+        return !isValidIndex(leftChildIndex(index));
+    }
+
+    private boolean isCorrectParent(int index) {
+        return isCorrect(index, leftChildIndex(index)) && isCorrect(index, rightChildIndex(index));
+    }
+
+    private boolean isCorrectChild(int index) {
+        return isCorrect(parentIndex(index), index);
+    }
+
+    private boolean isCorrect(int parentIndex, int childIndex) {
+        if (!isValidIndex(parentIndex) || !isValidIndex(childIndex)) {
+            return true;
+        }
+
+        return elementAt(parentIndex).compareTo(elementAt(childIndex)) < 0;
+    }
+
+    private boolean isValidIndex(int index) {
+        return index < elements.size();
+    }
+
+    private void swap(int index1, int index2) {
+        E element1 = elementAt(index1);
+        E element2 = elementAt(index2);
+        elements.set(index1, element2);
+        elements.set(index2, element1);
+    }
+
+    private E elementAt(int index) {
+        return elements.get(index);
+    }
+
+    private int parentIndex(int index) {
+        return (index - 1) / 2;
+    }
+
+    private int leftChildIndex(int index) {
+        return 2 * index + 1;
+    }
+
+    private int rightChildIndex(int index) {
+        return 2 * index + 2;
+    }
+
+}

algorithms/src/test/java/com/baeldung/algorithms/conversion/ByteArrayConverterUnitTest.java

@@ -0,0 +1,127 @@
+package com.baeldung.algorithms.conversion;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+
+import org.apache.commons.codec.DecoderException;
+import org.hamcrest.text.IsEqualIgnoringCase;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.baeldung.algorithms.conversion.HexStringConverter;
+
+public class ByteArrayConverterUnitTest {
+
+    private HexStringConverter hexStringConverter;
+
+    @Before
+    public void setup() {
+        hexStringConverter = new HexStringConverter();
+    }
+
+    @Test
+    public void shouldEncodeByteArrayToHexStringUsingBigIntegerToString() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        if(hexString.charAt(0) == '0') {
+            hexString = hexString.substring(1);
+        }
+        String output = hexStringConverter.encodeUsingBigIntegerToString(bytes);
+        assertThat(output, IsEqualIgnoringCase.equalToIgnoringCase(hexString));
+    }
+
+    @Test
+    public void shouldEncodeByteArrayToHexStringUsingBigIntegerStringFormat() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        String output = hexStringConverter.encodeUsingBigIntegerStringFormat(bytes);
+        assertThat(output, IsEqualIgnoringCase.equalToIgnoringCase(hexString));
+    }
+
+    @Test
+    public void shouldDecodeHexStringToByteArrayUsingBigInteger() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        byte[] output = hexStringConverter.decodeUsingBigInteger(hexString);
+        assertArrayEquals(bytes, output);
+    }
+    
+    @Test
+    public void shouldEncodeByteArrayToHexStringUsingCharacterConversion() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        String output = hexStringConverter.encodeHexString(bytes);
+        assertThat(output, IsEqualIgnoringCase.equalToIgnoringCase(hexString));
+    }
+
+    @Test
+    public void shouldDecodeHexStringToByteArrayUsingCharacterConversion() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        byte[] output = hexStringConverter.decodeHexString(hexString);
+        assertArrayEquals(bytes, output);
+    }
+    
+    @Test(expected=IllegalArgumentException.class)
+    public void shouldDecodeHexToByteWithInvalidHexCharacter() {
+        hexStringConverter.hexToByte("fg");
+    }
+
+    @Test
+    public void shouldEncodeByteArrayToHexStringDataTypeConverter() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        String output = hexStringConverter.encodeUsingDataTypeConverter(bytes);
+        assertThat(output, IsEqualIgnoringCase.equalToIgnoringCase(hexString));
+    }
+
+    @Test
+    public void shouldDecodeHexStringToByteArrayUsingDataTypeConverter() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        byte[] output = hexStringConverter.decodeUsingDataTypeConverter(hexString);
+        assertArrayEquals(bytes, output);
+    }
+
+    @Test
+    public void shouldEncodeByteArrayToHexStringUsingGuava() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        String output = hexStringConverter.encodeUsingGuava(bytes);
+        assertThat(output, IsEqualIgnoringCase.equalToIgnoringCase(hexString));
+    }
+
+    @Test
+    public void shouldDecodeHexStringToByteArrayUsingGuava() {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        byte[] output = hexStringConverter.decodeUsingGuava(hexString);
+        assertArrayEquals(bytes, output);
+    }
+
+    @Test
+    public void shouldEncodeByteArrayToHexStringUsingApacheCommons() throws DecoderException {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        String output = hexStringConverter.encodeUsingApacheCommons(bytes);
+        assertThat(output, IsEqualIgnoringCase.equalToIgnoringCase(hexString));
+    }
+
+    @Test
+    public void shouldDecodeHexStringToByteArrayUsingApacheCommons() throws DecoderException {
+        byte[] bytes = getSampleBytes();
+        String hexString = getSampleHexString();
+        byte[] output = hexStringConverter.decodeUsingApacheCommons(hexString);
+        assertArrayEquals(bytes, output);
+    }
+
+    private String getSampleHexString() {
+        return "0af50c0e2d10";
+    }
+
+    private byte[] getSampleBytes() {
+        return new byte[] { 10, -11, 12, 14, 45, 16 };
+    }
+
+}

algorithms/src/test/java/com/baeldung/algorithms/heapsort/HeapUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.heapsort;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Test;
+
+public class HeapUnitTest {
+
+    @Test
+    public void givenNotEmptyHeap_whenPopCalled_thenItShouldReturnSmallestElement() {
+        // given
+        Heap<Integer> heap = Heap.of(3, 5, 1, 4, 2);
+
+        // when
+        int head = heap.pop();
+
+        // then
+        assertThat(head).isEqualTo(1);
+    }
+    
+    @Test
+    public void givenNotEmptyIterable_whenSortCalled_thenItShouldReturnElementsInSortedList() {
+        // given
+        List<Integer> elements = Arrays.asList(3, 5, 1, 4, 2);
+        
+        // when
+        List<Integer> sortedElements = Heap.sort(elements);
+        
+        // then
+        assertThat(sortedElements).isEqualTo(Arrays.asList(1, 2, 3, 4, 5));
+    }
+
+}

apache-pulsar/.gitignore

@@ -0,0 +1,8 @@
+.classpath
+.project
+.settings
+target
+.idea
+*.iml
+.gradle/
+build/

apache-pulsar/pom.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.baeldung.pulsar</groupId>
+  <artifactId>pulsar-java</artifactId>
+  <version>0.0.1</version>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.apache.pulsar</groupId>
+      <artifactId>pulsar-client</artifactId>
+      <version>2.1.1-incubating</version>
+      <scope>compile</scope>
+    </dependency>
+  </dependencies>
+  <properties>
+    <maven.compiler.target>1.8</maven.compiler.target>
+    <maven.compiler.source>1.8</maven.compiler.source>
+  </properties>
+</project>

apache-pulsar/src/main/java/com/baeldung/ConsumerTest.java

@@ -0,0 +1,48 @@
+package com.baeldung;
+
+import java.io.IOException;
+
+import org.apache.pulsar.client.api.Consumer;
+import org.apache.pulsar.client.api.Message;
+import org.apache.pulsar.client.api.PulsarClient;
+import org.apache.pulsar.client.api.SubscriptionType;
+
+public class ConsumerTest {
+
+    private static final String SERVICE_URL = "pulsar://localhost:6650";
+    private static final String TOPIC_NAME = "test-topic";
+    private static final String SUBSCRIPTION_NAME = "test-subscription";
+
+    public static void main(String[] args) throws IOException {
+        // Create a Pulsar client instance. A single instance can be shared across many
+        // producers and consumer within the same application
+        PulsarClient client = PulsarClient.builder()
+                .serviceUrl(SERVICE_URL)
+                .build();
+
+        //Configure consumer specific settings.
+        Consumer<byte[]> consumer = client.newConsumer()
+                .topic(TOPIC_NAME)
+                // Allow multiple consumers to attach to the same subscription
+                // and get messages dispatched as a queue
+                .subscriptionType(SubscriptionType.Shared)
+                .subscriptionName(SUBSCRIPTION_NAME)
+                .subscribe();
+
+
+        // Once the consumer is created, it can be used for the entire application lifecycle
+        System.out.println("Created consumer for the topic "+ TOPIC_NAME);
+
+        do {
+            // Wait until a message is available
+            Message<byte[]> msg = consumer.receive();
+
+            // Extract the message as a printable string and then log
+            String content = new String(msg.getData());
+            System.out.println("Received message '"+content+"' with ID "+msg.getMessageId());
+
+            // Acknowledge processing of the message so that it can be deleted
+            consumer.acknowledge(msg);
+        } while (true);
+    }
+}

apache-pulsar/src/main/java/com/baeldung/ProducerTest.java

@@ -0,0 +1,58 @@
+package com.baeldung;
+
+import org.apache.pulsar.client.api.CompressionType;
+import org.apache.pulsar.client.api.Message;
+import org.apache.pulsar.client.api.MessageBuilder;
+import org.apache.pulsar.client.api.MessageId;
+import org.apache.pulsar.client.api.Producer;
+import org.apache.pulsar.client.api.PulsarClient;
+import org.apache.pulsar.client.api.PulsarClientException;
+
+import java.io.IOException;
+import java.util.stream.IntStream;
+
+public class ProducerTest {
+
+    private static final String SERVICE_URL = "pulsar://localhost:6650";
+    private static final String TOPIC_NAME = "test-topic";
+
+    public static void main(String[] args) throws IOException {
+        // Create a Pulsar client instance. A single instance can be shared across many
+        // producers and consumer within the same application
+        PulsarClient client = PulsarClient.builder()
+                .serviceUrl(SERVICE_URL)
+                .build();
+
+        // Configure producer specific settings
+        Producer<byte[]> producer = client.newProducer()
+                // Set the topic
+                .topic(TOPIC_NAME)
+                // Enable compression
+                .compressionType(CompressionType.LZ4)
+                .create();
+
+        // Once the producer is created, it can be used for the entire application life-cycle
+        System.out.println("Created producer for the topic "+TOPIC_NAME);
+
+        // Send 5 test messages
+        IntStream.range(1, 5).forEach(i -> {
+            String content = String.format("hi-pulsar-%d", i);
+
+            // Build a message object
+            Message<byte[]> msg = MessageBuilder.create()
+                    .setContent(content.getBytes())
+                    .build();
+
+            // Send each message and log message content and ID when successfully received
+            try {
+                MessageId msgId = producer.send(msg);
+
+                System.out.println("Published message '"+content+"' with the ID "+msgId);
+            } catch (PulsarClientException e) {
+                System.out.println(e.getMessage());
+            }
+        });
+
+        client.close();
+    }
+}

apache-pulsar/src/main/java/com/baeldung/subscriptions/ExclusiveSubscriptionTest.java

@@ -0,0 +1,59 @@
+package com.baeldung.subscriptions;
+
+import org.apache.pulsar.client.api.ConsumerBuilder;
+import org.apache.pulsar.client.api.Message;
+import org.apache.pulsar.client.api.MessageBuilder;
+import org.apache.pulsar.client.api.Producer;
+import org.apache.pulsar.client.api.PulsarClient;
+import org.apache.pulsar.client.api.PulsarClientException;
+import org.apache.pulsar.client.api.SubscriptionType;
+
+import java.util.stream.IntStream;
+
+public class ExclusiveSubscriptionTest {
+    private static final String SERVICE_URL = "pulsar://localhost:6650";
+    private static final String TOPIC_NAME = "test-topic";
+    private static final String SUBSCRIPTION_NAME = "test-subscription";
+    private static final SubscriptionType SUBSCRIPTION_TYPE = SubscriptionType.Exclusive;
+
+    public static void main(String[] args) throws PulsarClientException {
+        PulsarClient client = PulsarClient.builder()
+                .serviceUrl(SERVICE_URL)
+                .build();
+
+        Producer<byte[]> producer = client.newProducer()
+                .topic(TOPIC_NAME)
+                .create();
+
+        ConsumerBuilder<byte[]> consumer1 = client.newConsumer()
+                .topic(TOPIC_NAME)
+                .subscriptionName(SUBSCRIPTION_NAME)
+                .subscriptionType(SUBSCRIPTION_TYPE);
+
+        ConsumerBuilder<byte[]> consumer2 = client.newConsumer()
+                .topic(TOPIC_NAME)
+                .subscriptionName(SUBSCRIPTION_NAME)
+                .subscriptionType(SUBSCRIPTION_TYPE);
+
+        IntStream.range(0, 999).forEach(i -> {
+            Message<byte[]> msg = MessageBuilder.create()
+                    .setContent(String.format("message-%d", i).getBytes())
+                    .build();
+            try {
+                producer.send(msg);
+            } catch (PulsarClientException e) {
+                System.out.println(e.getMessage());
+            }
+        });
+
+        // Consumer 1 can subscribe to the topic
+        consumer1.subscribe();
+
+        // Consumer 2 cannot due to the exclusive subscription held by consumer 1
+        consumer2.subscribeAsync()
+                .handle((consumer, exception) -> {
+                    System.out.println(exception.getMessage());
+                    return null;
+                });
+    }
+}

apache-pulsar/src/main/java/com/baeldung/subscriptions/FailoverSubscriptionTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.subscriptions;
+
+import org.apache.pulsar.client.api.Consumer;
+import org.apache.pulsar.client.api.ConsumerBuilder;
+import org.apache.pulsar.client.api.Message;
+import org.apache.pulsar.client.api.MessageBuilder;
+import org.apache.pulsar.client.api.Producer;
+import org.apache.pulsar.client.api.PulsarClient;
+import org.apache.pulsar.client.api.PulsarClientException;
+import org.apache.pulsar.client.api.SubscriptionType;
+
+import java.util.stream.IntStream;
+
+public class FailoverSubscriptionTest {
+    private static final String SERVICE_URL = "pulsar://localhost:6650";
+    private static final String TOPIC_NAME = "failover-subscription-test-topic";
+    private static final String SUBSCRIPTION_NAME = "test-subscription";
+    private static final SubscriptionType SUBSCRIPTION_TYPE = SubscriptionType.Failover;
+    private static final int NUM_MSGS = 10;
+
+    public static void main(String[] args) throws PulsarClientException {
+        PulsarClient client = PulsarClient.builder()
+                .serviceUrl(SERVICE_URL)
+                .build();
+
+        Producer<byte[]> producer = client.newProducer()
+                .topic(TOPIC_NAME)
+                .create();
+
+        ConsumerBuilder<byte[]> consumerBuilder = client.newConsumer()
+                .topic(TOPIC_NAME)
+                .subscriptionName(SUBSCRIPTION_NAME)
+                .subscriptionType(SUBSCRIPTION_TYPE);
+
+        Consumer<byte[]> mainConsumer = consumerBuilder
+                .consumerName("consumer-a")
+                .messageListener((consumer, msg) -> {
+                    System.out.println("Message received by main consumer");
+
+                    try {
+                        consumer.acknowledge(msg);
+                    } catch (PulsarClientException e) {
+                        System.out.println(e.getMessage());
+                    }
+                })
+                .subscribe();
+
+        Consumer<byte[]> failoverConsumer = consumerBuilder
+                .consumerName("consumer-b")
+                .messageListener((consumer, msg) -> {
+                    System.out.println("Message received by failover consumer");
+
+                    try {
+                        consumer.acknowledge(msg);
+                    } catch (PulsarClientException e) {
+                        System.out.println(e.getMessage());
+                    }
+                })
+                .subscribe();
+
+        IntStream.range(0, NUM_MSGS).forEach(i -> {
+            Message<byte[]> msg = MessageBuilder.create()
+                    .setContent(String.format("message-%d", i).getBytes())
+                    .build();
+            try {
+                producer.send(msg);
+
+                Thread.sleep(100);
+
+                if (i > 5) mainConsumer.close();
+            } catch (InterruptedException | PulsarClientException e) {
+                System.out.println(e.getMessage());
+            }
+        });
+    }
+}

aws/README.md

@@ -9,4 +9,4 @@
 - [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)
 - [Managing Amazon SQS Queues in Java](http://www.baeldung.com/aws-queues-java)
-
+- [Guide to AWS Aurora RDS with Java](https://www.baeldung.com/aws-aurora-rds-java)

core-java-8/README.md

@@ -32,3 +32,4 @@
 - [Set the Time Zone of a Date in Java](https://www.baeldung.com/java-set-date-time-zone)
 - [An Overview of Regular Expressions Performance in Java](https://www.baeldung.com/java-regex-performance)
 - [Java Primitives versus Objects](https://www.baeldung.com/java-primitives-vs-objects)
+- [How to Use if/else Logic in Java 8 Streams](https://www.baeldung.com/java-8-streams-if-else-logic)

core-java-9/README.md

@@ -26,3 +26,4 @@
 - [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)

core-java-collections/README.md

@@ -4,37 +4,23 @@
 
 ### Relevant Articles: 
 - [Immutable ArrayList in Java](http://www.baeldung.com/java-immutable-list)
-- [Converting between an Array and a List in Java](http://www.baeldung.com/convert-array-to-list-and-list-to-array)
-- [Converting between an Array and a Set in Java](http://www.baeldung.com/convert-array-to-set-and-set-to-array)
-- [Converting between a List and a Set in Java](http://www.baeldung.com/convert-list-to-set-and-set-to-list)
-- [Convert a Map to an Array, List or Set in Java](http://www.baeldung.com/convert-map-values-to-array-list-set)
 - [Guide to the Java ArrayList](http://www.baeldung.com/java-arraylist)
 - [Random List Element](http://www.baeldung.com/java-random-list-element)
 - [Java - Combine Multiple Collections](http://www.baeldung.com/java-combine-multiple-collections)
-- [Guide to WeakHashMap in Java](http://www.baeldung.com/java-weakhashmap)
-- [Guide to the Guava BiMap](http://www.baeldung.com/guava-bimap)
-- [The Java HashMap Under the Hood](http://www.baeldung.com/java-hashmap)
-- [A Guide to LinkedHashMap in Java](http://www.baeldung.com/java-linked-hashmap)
-- [A Guide to TreeMap in Java](http://www.baeldung.com/java-treemap)
 - [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)
 - [Flattening Nested Collections in Java](http://www.baeldung.com/java-flatten-nested-collections)
 - [HashSet and TreeSet Comparison](http://www.baeldung.com/java-hashset-vs-treeset)
-- [Iterate over a Map in Java](http://www.baeldung.com/java-iterate-map)
 - [Collect a Java Stream to an Immutable Collection](http://www.baeldung.com/java-stream-immutable-collection)
-- [Converting a List to String in Java](http://www.baeldung.com/java-list-to-string)
 - [Introduction to the Java ArrayDeque](http://www.baeldung.com/java-array-deque)
 - [A Guide to HashSet in Java](http://www.baeldung.com/java-hashset)
 - [A Guide to TreeSet in Java](http://www.baeldung.com/java-tree-set)
-- [Java TreeMap vs HashMap](http://www.baeldung.com/java-treemap-vs-hashmap)
 - [How to TDD a List Implementation in Java](http://www.baeldung.com/java-test-driven-list)
-- [How to Store Duplicate Keys in a Map in Java?](http://www.baeldung.com/java-map-duplicate-keys)
 - [Getting the Size of an Iterable in Java](http://www.baeldung.com/java-iterable-size)
 - [Iterating Backward Through a List](http://www.baeldung.com/java-list-iterate-backwards)
 - [How to Filter a Collection in Java](http://www.baeldung.com/java-collection-filtering)
 - [Add Multiple Items to an Java ArrayList](http://www.baeldung.com/java-add-items-array-list)
 - [Remove the First Element from a List](http://www.baeldung.com/java-remove-first-element-from-list)
-- [How to Convert List to Map in Java](http://www.baeldung.com/java-list-to-map)
 - [Initializing HashSet at the Time of Construction](http://www.baeldung.com/java-initialize-hashset)
 - [Removing the First Element of an Array](https://www.baeldung.com/java-array-remove-first-element)
 - [Fail-Safe Iterator vs Fail-Fast Iterator](http://www.baeldung.com/java-fail-safe-vs-fail-fast-iterator)
@@ -47,8 +33,8 @@
 - [Remove All Occurrences of a Specific Value from a List](https://www.baeldung.com/java-remove-value-from-list)
 - [Thread Safe LIFO Data Structure Implementations](https://www.baeldung.com/java-lifo-thread-safe)
 - [Collections.emptyList() vs. New List Instance](https://www.baeldung.com/java-collections-emptylist-new-list)
-- [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
 - [Differences Between Collection.clear() and Collection.removeAll()](https://www.baeldung.com/java-collection-clear-vs-removeall)
 - [Performance of contains() in a HashSet vs ArrayList](https://www.baeldung.com/java-hashset-arraylist-contains-performance)
-- [Get the Key for a Value from a Java Map](https://www.baeldung.com/java-map-key-from-value)
 - [Time Complexity of Java Collections](https://www.baeldung.com/java-collections-complexity)
+- [Operating on and Removing an Item from Stream](https://www.baeldung.com/java-use-remove-item-stream)
+- [An Introduction to Synchronized Java Collections](https://www.baeldung.com/java-synchronized-collections)

core-java-collections/pom.xml

@@ -14,22 +14,11 @@
     </parent>
 
     <dependencies>
-        <dependency>
-            <groupId>net.sourceforge.collections</groupId>
-            <artifactId>collections-generic</artifactId>
-            <version>${collections-generic.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
-        <dependency>
-            <groupId>com.jayway.awaitility</groupId>
-            <artifactId>awaitility</artifactId>
-            <version>${avaitility.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
@@ -67,12 +56,6 @@
             <artifactId>commons-exec</artifactId>
             <version>1.3</version>
         </dependency>
-        
-        <dependency>
-            <groupId>one.util</groupId>
-            <artifactId>streamex</artifactId>
-            <version>0.6.5</version>
-        </dependency>
     </dependencies>
 
     <properties>

core-java-collections/src/main/java/com/baeldung/enumset/EnumSets.java

@@ -0,0 +1,45 @@
+package com.baeldung.enumset;
+
+import java.util.ArrayList;
+import java.util.EnumSet;
+import java.util.List;
+
+public class EnumSets {
+
+    public enum Color {
+        RED, YELLOW, GREEN, BLUE, BLACK, WHITE
+    }
+
+    public static void main(String[] args) {
+        EnumSet<Color> allColors = EnumSet.allOf(Color.class);
+        System.out.println(allColors);
+
+        EnumSet<Color> noColors = EnumSet.noneOf(Color.class);
+        System.out.println(noColors);
+
+        EnumSet<Color> blackAndWhite = EnumSet.of(Color.BLACK, Color.WHITE);
+        System.out.println(blackAndWhite);
+
+        EnumSet<Color> noBlackOrWhite = EnumSet.complementOf(blackAndWhite);
+        System.out.println(noBlackOrWhite);
+
+        EnumSet<Color> range = EnumSet.range(Color.YELLOW, Color.BLUE);
+        System.out.println(range);
+
+        EnumSet<Color> blackAndWhiteCopy = EnumSet.copyOf(EnumSet.of(Color.BLACK, Color.WHITE));
+        System.out.println(blackAndWhiteCopy);
+
+        List<Color> colorsList = new ArrayList<>();
+        colorsList.add(Color.RED);
+        EnumSet<Color> listCopy = EnumSet.copyOf(colorsList);
+        System.out.println(listCopy);
+
+        EnumSet<Color> set = EnumSet.noneOf(Color.class);
+        set.add(Color.RED);
+        set.add(Color.YELLOW);
+        set.contains(Color.RED);
+        set.forEach(System.out::println);
+        set.remove(Color.RED);
+    }
+
+}

core-java-collections/src/main/java/com/baeldung/removal/CollectionRemoveIf.java

@@ -0,0 +1,19 @@
+package com.baeldung.removal;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+public class CollectionRemoveIf {
+
+    public static void main(String args[]) {
+        Collection<String> names = new ArrayList<>();
+        names.add("John");
+        names.add("Ana");
+        names.add("Mary");
+        names.add("Anthony");
+        names.add("Mark");
+
+        names.removeIf(e -> e.startsWith("A"));
+        System.out.println(String.join(",", names));
+    }
+}

core-java-collections/src/main/java/com/baeldung/removal/Iterators.java

@@ -0,0 +1,28 @@
+package com.baeldung.removal;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+
+public class Iterators {
+
+    public static void main(String args[]) {
+        Collection<String> names = new ArrayList<>();
+        names.add("John");
+        names.add("Ana");
+        names.add("Mary");
+        names.add("Anthony");
+        names.add("Mark");
+
+        Iterator<String> i = names.iterator();
+
+        while (i.hasNext()) {
+            String e = i.next();
+            if (e.startsWith("A")) {
+                i.remove();
+            }
+        }
+
+        System.out.println(String.join(",", names));
+    }
+}

core-java-collections/src/main/java/com/baeldung/removal/StreamFilterAndCollector.java

@@ -0,0 +1,23 @@
+package com.baeldung.removal;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.stream.Collectors;
+
+public class StreamFilterAndCollector {
+
+    public static void main(String args[]) {
+        Collection<String> names = new ArrayList<>();
+        names.add("John");
+        names.add("Ana");
+        names.add("Mary");
+        names.add("Anthony");
+        names.add("Mark");
+
+        Collection<String> filteredCollection = names
+                .stream()
+                .filter(e -> !e.startsWith("A"))
+                .collect(Collectors.toList());
+        System.out.println(String.join(",", filteredCollection));
+    }
+}

core-java-collections/src/main/java/com/baeldung/removal/StreamPartitioningBy.java

@@ -0,0 +1,28 @@
+package com.baeldung.removal;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class StreamPartitioningBy {
+
+    public static void main(String args[]) {
+        Collection<String> names = new ArrayList<>();
+        names.add("John");
+        names.add("Ana");
+        names.add("Mary");
+        names.add("Anthony");
+        names.add("Mark");
+
+        Map<Boolean, List<String>> classifiedElements = names
+                .stream()
+                .collect(Collectors.partitioningBy((String e) -> !e.startsWith("A")));
+
+        String matching = String.join(",", classifiedElements.get(Boolean.TRUE));
+        String nonMatching = String.join(",", classifiedElements.get(Boolean.FALSE));
+        System.out.println("Matching elements: " + matching);
+        System.out.println("Non matching elements: " + nonMatching);
+    }
+}

core-java-collections/src/test/java/com/baeldung/findItems/FindItemsBasedOnOtherStreamUnitTest.java

@@ -0,0 +1,89 @@
+package com.baeldung.findItems;
+
+import static org.junit.Assert.assertEquals;
+
+import java.text.ParseException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+
+public class FindItemsBasedOnOtherStreamUnitTest {
+
+    private List<Employee> employeeList = new ArrayList<Employee>();
+
+    private List<Department> departmentList = new ArrayList<Department>();
+
+    @Test
+    public void givenDepartmentList_thenEmployeeListIsFilteredCorrectly() {
+        Integer expectedId = 1002;
+
+        populate(employeeList, departmentList);
+
+        List<Employee> filteredList = employeeList.stream()
+            .filter(empl -> departmentList.stream()
+                .anyMatch(dept -> dept.getDepartment()
+                    .equals("sales") && empl.getEmployeeId()
+                    .equals(dept.getEmployeeId())))
+            .collect(Collectors.toList());
+
+        assertEquals(expectedId, filteredList.get(0)
+            .getEmployeeId());
+    }
+
+    private void populate(List<Employee> EmplList, List<Department> deptList) {
+        Employee employee1 = new Employee(1001, "empl1");
+        Employee employee2 = new Employee(1002, "empl2");
+        Employee employee3 = new Employee(1003, "empl3");
+
+        Collections.addAll(EmplList, employee1, employee2, employee3);
+
+        Department department1 = new Department(1002, "sales");
+        Department department2 = new Department(1003, "marketing");
+        Department department3 = new Department(1004, "sales");
+
+        Collections.addAll(deptList, department1, department2, department3);
+    }
+}
+
+class Employee {
+    private Integer employeeId;
+    private String employeeName;
+
+    Employee(Integer employeeId, String employeeName) {
+        super();
+        this.employeeId = employeeId;
+        this.employeeName = employeeName;
+    }
+
+    Integer getEmployeeId() {
+        return employeeId;
+    }
+
+    public String getEmployeeName() {
+        return employeeName;
+    }
+
+}
+
+class Department {
+    private Integer employeeId;
+    private String department;
+
+    Department(Integer employeeId, String department) {
+        super();
+        this.employeeId = employeeId;
+        this.department = department;
+    }
+
+    Integer getEmployeeId() {
+        return employeeId;
+    }
+
+    String getDepartment() {
+        return department;
+    }
+
+}

core-java-collections/src/test/java/com/baeldung/removal/RemovalUnitTest.java

@@ -0,0 +1,77 @@
+package com.baeldung.removal;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+
+public class RemovalUnitTest {
+
+    Collection<String> names;
+    Collection<String> expected;
+    Collection<String> removed;
+
+    @Before
+    public void setupTestData() {
+        names = new ArrayList<>();
+        expected = new ArrayList<>();
+        removed = new ArrayList<>();
+
+        names.add("John");
+        names.add("Ana");
+        names.add("Mary");
+        names.add("Anthony");
+        names.add("Mark");
+
+        expected.add("John");
+        expected.add("Mary");
+        expected.add("Mark");
+
+        removed.add("Ana");
+        removed.add("Anthony");
+    }
+
+    @Test
+    public void givenCollectionOfNames_whenUsingIteratorToRemoveAllNamesStartingWithLetterA_finalListShouldContainNoNamesStartingWithLetterA() {
+        Iterator<String> i = names.iterator();
+
+        while (i.hasNext()) {
+            String e = i.next();
+            if (e.startsWith("A")) {
+                i.remove();
+            }
+        }
+
+        assertThat(names, is(expected));
+    }
+
+    @Test
+    public void givenCollectionOfNames_whenUsingRemoveIfToRemoveAllNamesStartingWithLetterA_finalListShouldContainNoNamesStartingWithLetterA() {
+        names.removeIf(e -> e.startsWith("A"));
+        assertThat(names, is(expected));
+    }
+
+    @Test
+    public void givenCollectionOfNames_whenUsingStreamToFilterAllNamesStartingWithLetterA_finalListShouldContainNoNamesStartingWithLetterA() {
+        Collection<String> filteredCollection = names
+                .stream()
+                .filter(e -> !e.startsWith("A"))
+                .collect(Collectors.toList());
+        assertThat(filteredCollection, is(expected));
+    }
+
+    @Test
+    public void givenCollectionOfNames_whenUsingStreamAndPartitioningByToFindNamesThatStartWithLetterA_shouldFind3MatchingAnd2NonMatching() {
+        Map<Boolean, List<String>> classifiedElements = names
+                .stream()
+                .collect(Collectors.partitioningBy((String e) -> !e.startsWith("A")));
+
+        assertThat(classifiedElements.get(Boolean.TRUE), is(expected));
+        assertThat(classifiedElements.get(Boolean.FALSE), is(removed));
+    }
+
+}

core-java-concurrency/README.md

@@ -29,3 +29,4 @@
 - [A Custom Spring SecurityConfigurer](http://www.baeldung.com/spring-security-custom-configurer)
 - [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)
+- [Brief Introduction to Java Thread.yield()](https://www.baeldung.com/java-thread-yield)

core-java-concurrency/src/test/java/com/baeldung/completablefuture/CompletableFutureLongRunningUnitTest.java

@@ -184,5 +184,25 @@ public class CompletableFutureLongRunningUnitTest {
 
         assertEquals("Hello World", future.get());
     }
+    
+    @Test
+    public void whenPassingTransformation_thenFunctionExecutionWithThenApply() throws InterruptedException, ExecutionException {
+        CompletableFuture<Integer> finalResult = compute().thenApply(s -> s + 1);
+        assertTrue(finalResult.get() == 11);
+    }
+    
+    @Test
+    public void whenPassingPreviousStage_thenFunctionExecutionWithThenCompose() throws InterruptedException, ExecutionException {
+        CompletableFuture<Integer> finalResult = compute().thenCompose(this::computeAnother);
+        assertTrue(finalResult.get() == 20);
+    }
+    
+    public CompletableFuture<Integer> compute(){
+        return CompletableFuture.supplyAsync(() -> 10);
+    }
+    
+    public CompletableFuture<Integer> computeAnother(Integer i){
+        return CompletableFuture.supplyAsync(() -> 10 + i);
+    }
 
 }

core-java-io/src/main/resources/zipTest/test1.txt

@@ -0,0 +1 @@
+Test1

core-java-io/src/main/resources/zipTest/test2.txt

@@ -0,0 +1 @@
+Test2