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

algorithms-miscellaneous-1/README.md

@@ -10,4 +10,4 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Introduction to Minimax Algorithm](https://www.baeldung.com/java-minimax-algorithm)
 - [How to Calculate Levenshtein Distance in Java?](https://www.baeldung.com/java-levenshtein-distance)
 - [How to Find the Kth Largest Element in Java](https://www.baeldung.com/java-kth-largest-element)
-- More articles: [[next -->]](/../algorithms-miscellaneous-2)
+- More articles: [[next -->]](/algorithms-miscellaneous-2)

algorithms-miscellaneous-2/README.md

@@ -14,4 +14,4 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Displaying Money Amounts in Words](https://www.baeldung.com/java-money-into-words)
 - [A Collaborative Filtering Recommendation System in Java](https://www.baeldung.com/java-collaborative-filtering-recommendations)
 - [Implementing A* Pathfinding in Java](https://www.baeldung.com/java-a-star-pathfinding)
-- More articles: [[<-- prev]](/../algorithms-miscellaneous-1) [[next -->]](/../algorithms-miscellaneous-3)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-1) [[next -->]](/algorithms-miscellaneous-3)

algorithms-miscellaneous-5/README.md

@@ -15,5 +15,5 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Maximum Subarray Problem](https://www.baeldung.com/java-maximum-subarray)
 - [How to Merge Two Sorted Arrays](https://www.baeldung.com/java-merge-sorted-arrays)
 - [Median of Stream of Integers using Heap](https://www.baeldung.com/java-stream-integers-median-using-heap)
-- More articles: [[<-- prev]](/../algorithms-miscellaneous-4) [[next -->]](/../algorithms-miscellaneous-6)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-4) [[next -->]](/algorithms-miscellaneous-6)
 

algorithms-miscellaneous-6/README.md

@@ -9,4 +9,5 @@
 - [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
 - [Implementing a 2048 Solver in Java](https://www.baeldung.com/2048-java-solver)
 - [Finding Top K Elements in an Array](https://www.baeldung.com/java-array-top-elements)
-- More articles: [[<-- prev]](/../algorithms-miscellaneous-5)
+- [Reversing a Linked List in Java](https://www.baeldung.com/java-reverse-linked-list)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-5)

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/linkedlist/LinkedListReversal.java

@@ -0,0 +1,30 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class LinkedListReversal {
+
+    ListNode reverseList(ListNode head) {
+        ListNode previous = null;
+        ListNode current = head;
+        while (current != null) {
+            ListNode nextElement = current.getNext();
+            current.setNext(previous);
+            previous = current;
+            current = nextElement;
+        }
+        return previous;
+    }
+
+    ListNode reverseListRecursive(ListNode head) {
+        if (head == null) {
+            return null;
+        }
+        if (head.getNext() == null) {
+            return head;
+        }
+        ListNode node = reverseListRecursive(head.getNext());
+        head.getNext().setNext(head);
+        head.setNext(null);
+        return node;
+    }
+
+}

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/linkedlist/ListNode.java

@@ -0,0 +1,28 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class ListNode {
+
+    private int data;
+    private ListNode next;
+
+    ListNode(int data) {
+        this.data = data;
+        this.next = null;
+    }
+
+    public int getData() {
+        return data;
+    }
+
+    public ListNode getNext() {
+        return next;
+    }
+
+    public void setData(int data) {
+        this.data = data;
+    }
+
+    public void setNext(ListNode next) {
+        this.next = next;
+    }
+}

algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/linkedlist/LinkedListReversalUnitTest.java

@@ -0,0 +1,59 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+public class LinkedListReversalUnitTest {
+    @Test
+    public void givenLinkedList_whenIterativeReverse_thenOutputCorrectResult() {
+        ListNode head = constructLinkedList();
+        ListNode node = head;
+        for (int i = 1; i <= 5; i++) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+        LinkedListReversal reversal = new LinkedListReversal();
+        node = reversal.reverseList(head);
+        for (int i = 5; i >= 1; i--) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+    }
+
+    @Test
+    public void givenLinkedList_whenRecursiveReverse_thenOutputCorrectResult() {
+        ListNode head = constructLinkedList();
+        ListNode node = head;
+        for (int i = 1; i <= 5; i++) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+        LinkedListReversal reversal = new LinkedListReversal();
+        node = reversal.reverseListRecursive(head);
+        for (int i = 5; i >= 1; i--) {
+            assertNotNull(node);
+            assertEquals(i, node.getData());
+            node = node.getNext();
+        }
+    }
+
+    private ListNode constructLinkedList() {
+        ListNode head = null;
+        ListNode tail = null;
+        for (int i = 1; i <= 5; i++) {
+            ListNode node = new ListNode(i);
+            if (head == null) {
+                head = node;
+            } else {
+                tail.setNext(node);
+            }
+            tail = node;
+        }
+        return head;
+    }
+}

apache-libraries/pom.xml

@@ -129,6 +129,11 @@
             <artifactId>zookeeper</artifactId>
             <version>${zookeeper.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-core</artifactId>
+            <version>${jackson.version}</version>
+        </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>

apache-spark/src/main/java/com/baeldung/differences/dataframe/dataset/rdd/TouristData.java

@@ -0,0 +1,75 @@
+package com.baeldung.differences.dataframe.dataset.rdd;
+
+
+public class TouristData {
+
+    private String region;
+    private String country;
+    private String year;
+    private String series;
+    private Double value;
+    private String footnotes;
+    private String source;
+
+    public String getRegion() {
+        return region;
+    }
+
+    public void setRegion(String region) {
+        this.region = region;
+    }
+
+    public String getCountry() {
+        return country;
+    }
+
+    public void setCountry(String country) {
+        this.country = country;
+    }
+
+    public String getYear() {
+        return year;
+    }
+
+    public void setYear(String year) {
+        this.year = year;
+    }
+
+    public String getSeries() {
+        return series;
+    }
+
+    public void setSeries(String series) {
+        this.series = series;
+    }
+
+    public Double getValue() {
+        return value;
+    }
+
+    public void setValue(Double value) {
+        this.value = value;
+    }
+
+    public String getFootnotes() {
+        return footnotes;
+    }
+
+    public void setFootnotes(String footnotes) {
+        this.footnotes = footnotes;
+    }
+
+    public String getSource() {
+        return source;
+    }
+
+    public void setSource(String source) {
+        this.source = source;
+    }
+
+    @Override
+    public String toString() {
+        return "TouristData [region=" + region + ", country=" + country + ", year=" + year + ", series=" + series + ", value=" + value + ", footnotes=" + footnotes + ", source=" + source + "]";
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/ActionsUnitTest.java

@@ -0,0 +1,67 @@
+package com.baeldung.differences.rdd;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.List;
+
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaPairRDD;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import scala.Tuple2;
+
+public class ActionsUnitTest {
+    private static JavaRDD<String> tourists;
+    private static JavaSparkContext sc;
+    public static final String COMMA_DELIMITER = ",(?=([^\"]*\"[^\"]*\")*[^\"]*$)";
+    
+    @BeforeClass
+    public static void init() {
+        SparkConf conf = new SparkConf().setAppName("reduce")
+            .setMaster("local[*]");
+        sc = new JavaSparkContext(conf);
+        tourists = sc.textFile("data/Tourist.csv").filter(line -> !line.startsWith("Region"));
+    }
+    
+    @AfterClass
+    public static void cleanup() {
+        sc.close();
+    }
+
+    @Test
+    public void whenDistinctCount_thenReturnDistinctNumRecords() {
+        JavaRDD<String> countries = tourists.map(line -> {
+            String[] columns = line.split(COMMA_DELIMITER);
+            return columns[1];
+        })
+            .distinct();
+        Long numberOfCountries = countries.count();
+        System.out.println("Count: " + numberOfCountries);
+        
+        assertEquals(Long.valueOf(220), numberOfCountries);
+    }
+    
+    @Test
+    public void whenReduceByKeySum_thenTotalValuePerKey() {
+        JavaRDD<String> touristsExpenditure = tourists.filter(line -> line.split(COMMA_DELIMITER)[3].contains("expenditure"));
+
+        JavaPairRDD<String, Double> expenditurePairRdd = touristsExpenditure.mapToPair(line -> {
+            String[] columns = line.split(COMMA_DELIMITER);
+            return new Tuple2<>(columns[1], Double.valueOf(columns[6]));
+        });
+        List<Tuple2<String, Double>> totalByCountry = expenditurePairRdd.reduceByKey((x, y) -> x + y)
+            .collect();
+        System.out.println("Total per Country: " + totalByCountry);
+        
+        for(Tuple2<String, Double> tuple : totalByCountry) {
+            if (tuple._1.equals("Mexico")) {
+                assertEquals(Double.valueOf(99164), tuple._2);
+            }
+        }
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/DataFrameUnitTest.java

@@ -0,0 +1,74 @@
+package com.baeldung.differences.rdd;
+
+import static org.apache.spark.sql.functions.col;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.spark.sql.DataFrameReader;
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SparkSession;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class DataFrameUnitTest {
+    private static SparkSession session;
+    private static Dataset<Row> data;
+
+    @BeforeClass
+    public static void init() {
+        session = SparkSession.builder()
+            .appName("TouristDataFrameExample")
+            .master("local[*]")
+            .getOrCreate();
+        DataFrameReader dataFrameReader = session.read();
+        data = dataFrameReader.option("header", "true")
+            .csv("data/Tourist.csv");
+    }
+
+    @AfterClass
+    public static void cleanup() {
+        session.stop();
+    }
+
+    @Test
+    public void whenSelectSpecificColumns_thenColumnsFiltered() {
+        Dataset<Row> selectedData = data.select(col("country"), col("year"), col("value"));
+        selectedData.show();
+        
+        List<String> resultList = Arrays.asList(selectedData.columns());
+        assertTrue(resultList.contains("country"));
+        assertTrue(resultList.contains("year"));
+        assertTrue(resultList.contains("value"));
+        assertFalse(resultList.contains("Series"));
+
+    }
+
+    @Test
+    public void whenFilteringByCountry_thenCountryRecordsSelected() {
+        Dataset<Row> filteredData = data.filter(col("country").equalTo("Mexico"));
+        filteredData.show();
+        
+        filteredData.foreach(record -> {
+            assertEquals("Mexico", record.get(1));
+        });
+        
+    }
+
+    @Test
+    public void whenGroupCountByCountry_thenContryTotalRecords() {
+        Dataset<Row> recordsPerCountry = data.groupBy(col("country"))
+            .count();
+        recordsPerCountry.show();
+        
+        Dataset<Row> filteredData = recordsPerCountry.filter(col("country").equalTo("Sweden"));
+        assertEquals(new Long(12), filteredData.first()
+            .get(1));
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/DatasetUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.differences.rdd;
+
+import static org.apache.spark.sql.functions.col;
+import static org.apache.spark.sql.functions.sum;
+import static org.junit.Assert.assertEquals;
+
+import org.apache.spark.api.java.function.FilterFunction;
+import org.apache.spark.sql.DataFrameReader;
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Encoders;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SparkSession;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import com.baeldung.differences.dataframe.dataset.rdd.TouristData;
+
+public class DatasetUnitTest {
+    private static SparkSession session;
+    private static Dataset<TouristData> typedDataset;
+
+    @BeforeClass
+    public static void init() {
+        session = SparkSession.builder()
+            .appName("TouristDatasetExample")
+            .master("local[*]")
+            .getOrCreate();
+        DataFrameReader dataFrameReader = session.read();
+        Dataset<Row> data = dataFrameReader.option("header", "true")
+            .csv("data/Tourist.csv");
+        Dataset<Row> responseWithSelectedColumns = data.select(col("region"), 
+            col("country"), col("year"), col("series"), col("value").cast("double"), 
+            col("footnotes"), col("source"));
+        typedDataset = responseWithSelectedColumns.as(Encoders.bean(TouristData.class));
+    }
+
+    @AfterClass
+    public static void cleanup() {
+        session.stop();
+    }
+
+    @Test
+    public void whenFilteringByCountry_thenCountryRecordsSelected() {
+        Dataset<TouristData> selectedData = typedDataset
+            .filter((FilterFunction<TouristData>) record -> record.getCountry()
+            .equals("Norway"));
+        selectedData.show();
+
+        selectedData.foreach(record -> {
+            assertEquals("Norway", record.getCountry());
+        });
+    }
+
+    @Test
+    public void whenGroupCountByCountry_thenContryTotalRecords() {
+        Dataset<Row> countriesCount = typedDataset.groupBy(typedDataset.col("country"))
+            .count();
+        countriesCount.show();
+
+        assertEquals(Long.valueOf(220), Long.valueOf(countriesCount.count()));
+    }
+
+    @Test
+    public void whenFilteredByPropertyRange_thenRetreiveValidRecords() {
+        // Filter records with existing data for years between 2010 and 2017
+        typedDataset.filter((FilterFunction<TouristData>) record -> record.getYear() != null 
+            && (Long.valueOf(record.getYear()) > 2010 && Long.valueOf(record.getYear()) < 2017))
+            .show();
+    }
+    
+    @Test
+    public void whenSumValue_thenRetreiveTotalValue() {
+        // Total tourist expenditure by country
+        typedDataset.filter((FilterFunction<TouristData>) record -> record.getValue() != null 
+            && record.getSeries()
+            .contains("expenditure"))
+            .groupBy("country")
+            .agg(sum("value"))
+            .show();
+    }
+
+}

apache-spark/src/test/java/com/baeldung/differences/rdd/TransformationsUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.differences.rdd;
+
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class TransformationsUnitTest {
+    
+    public static final String COMMA_DELIMITER = ",(?=([^\"]*\"[^\"]*\")*[^\"]*$)";
+    private static JavaSparkContext sc;
+    private static JavaRDD<String> tourists;
+    
+    @BeforeClass
+    public static void init() {
+        SparkConf conf = new SparkConf().setAppName("uppercaseCountries")
+            .setMaster("local[*]");
+        sc = new JavaSparkContext(conf);
+        tourists = sc.textFile("data/Tourist.csv")
+            .filter(line -> !line.startsWith("Region")); //filter header row
+    }
+    
+    @AfterClass
+    public static void cleanup() {
+        sc.close();
+    }
+
+    @Test
+    public void whenMapUpperCase_thenCountryNameUppercased() {
+        JavaRDD<String> upperCaseCountries = tourists.map(line -> {
+            String[] columns = line.split(COMMA_DELIMITER);
+            return columns[1].toUpperCase();
+        })
+            .distinct();
+        
+        upperCaseCountries.saveAsTextFile("data/output/uppercase.txt");
+        
+        upperCaseCountries.foreach(country -> {
+            //replace non alphanumerical characters
+            country = country.replaceAll("[^a-zA-Z]", "");
+            assertTrue(StringUtils.isAllUpperCase(country));
+        });
+    }
+
+    @Test
+    public void whenFilterByCountry_thenShowRequestedCountryRecords() {
+        JavaRDD<String> touristsInMexico = tourists.filter(line -> line.split(COMMA_DELIMITER)[1].equals("Mexico"));
+        
+        touristsInMexico.saveAsTextFile("data/output/touristInMexico.txt");
+        
+        touristsInMexico.foreach(record -> {
+            assertEquals("Mexico", record.split(COMMA_DELIMITER)[1]);
+        });
+    }
+
+}

aws-lambda/README.md

@@ -5,3 +5,4 @@ This module contains articles about AWS Lambda
 ### Relevant Articles: 
 - [Using AWS Lambda with API Gateway](https://www.baeldung.com/aws-lambda-api-gateway)
 - [Introduction to AWS Serverless Application Model](https://www.baeldung.com/aws-serverless)
+- [How to Implement Hibernate in an AWS Lambda Function in Java](https://www.baeldung.com/java-aws-lambda-hibernate)

core-groovy-strings/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [How to Remove a Prefix From Strings in Groovy](https://www.baeldung.com/groovy-remove-string-prefix)

core-groovy-strings/pom.xml

@@ -0,0 +1,122 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project
+    xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-groovy-strings</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <name>core-groovy-strings</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy</artifactId>
+            <version>${groovy.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-all</artifactId>
+            <version>${groovy-all.version}</version>
+            <type>pom</type>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-dateutil</artifactId>
+            <version>${groovy.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-sql</artifactId>
+            <version>${groovy-sql.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.hsqldb</groupId>
+            <artifactId>hsqldb</artifactId>
+            <version>${hsqldb.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.spockframework</groupId>
+            <artifactId>spock-core</artifactId>
+            <version>${spock-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.gmavenplus</groupId>
+                <artifactId>gmavenplus-plugin</artifactId>
+                <version>${gmavenplus-plugin.version}</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>addSources</goal>
+                            <goal>addTestSources</goal>
+                            <goal>compile</goal>
+                            <goal>compileTests</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <artifactId>maven-failsafe-plugin</artifactId>
+                <version>${maven-failsafe-plugin.version}</version>
+                <dependencies>
+                    <dependency>
+                        <groupId>org.junit.platform</groupId>
+                        <artifactId>junit-platform-surefire-provider</artifactId>
+                        <version>${junit.platform.version}</version>
+                    </dependency>
+                </dependencies>
+                <executions>
+                    <execution>
+                        <id>junit5</id>
+                        <goals>
+                            <goal>integration-test</goal>
+                            <goal>verify</goal>
+                        </goals>
+                        <configuration>
+                            <includes>
+                                <include>**/*Test5.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <repositories>
+        <repository>
+            <id>central</id>
+            <url>https://jcenter.bintray.com</url>
+        </repository>
+    </repositories>
+
+    <properties>
+        <junit.platform.version>1.0.0</junit.platform.version>
+        <groovy.version>2.5.6</groovy.version>
+        <groovy-all.version>2.5.6</groovy-all.version>
+        <groovy-sql.version>2.5.6</groovy-sql.version>
+        <hsqldb.version>2.4.0</hsqldb.version>
+        <spock-core.version>1.1-groovy-2.4</spock-core.version>
+        <gmavenplus-plugin.version>1.6</gmavenplus-plugin.version>
+    </properties>
+
+</project>

core-groovy-strings/src/test/groovy/com/baeldung/removeprefix/RemovePrefixTest.groovy

@@ -0,0 +1,70 @@
+package com.baeldung.removeprefix
+
+import org.junit.Assert
+import org.junit.Test
+
+class RemovePrefixTest {
+
+
+    @Test
+    public void whenCasePrefixIsRemoved_thenReturnTrue() {
+        def trimPrefix = {
+            it.startsWith('Groovy-') ? it.minus('Groovy-') : it
+        }
+        
+        def actual = trimPrefix("Groovy-Tutorials at Baeldung")
+        def expected = "Tutorials at Baeldung"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test
+    public void whenPrefixIsRemoved_thenReturnTrue() {
+
+        String prefix = "groovy-"
+        String trimPrefix = "Groovy-Tutorials at Baeldung"
+        def actual;
+        if(trimPrefix.startsWithIgnoreCase(prefix)) {
+            actual = trimPrefix.substring(prefix.length())
+        }
+        
+        def expected = "Tutorials at Baeldung"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test
+    public void whenPrefixIsRemovedUsingRegex_thenReturnTrue() {
+
+        def regex = ~"^([Gg])roovy-"
+        String trimPrefix = "Groovy-Tutorials at Baeldung"
+        String actual = trimPrefix - regex
+        
+        def expected = "Tutorials at Baeldung"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test 
+    public void whenPrefixIsRemovedUsingReplaceFirst_thenReturnTrue() {
+        def regex = ~"^groovy" 
+        String trimPrefix = "groovyTutorials at Baeldung's groovy page" 
+        String actual = trimPrefix.replaceFirst(regex, "")
+        
+        def expected = "Tutorials at Baeldung's groovy page"
+        
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test
+    public void whenPrefixIsRemovedUsingReplaceAll_thenReturnTrue() {
+
+        String trimPrefix = "groovyTutorials at Baeldung groovy"
+        String actual = trimPrefix.replaceAll(/^groovy/, "")
+        
+        def expected = "Tutorials at Baeldung groovy"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+}

core-java-modules/core-java-10/src/test/java/com/baeldung/AppUnitTest.java

@@ -7,7 +7,7 @@ import junit.framework.TestSuite;
 /**
  * Unit test for simple App.
  */
-public class AppTest 
+public class AppUnitTest
     extends TestCase
 {
     /**
@@ -15,7 +15,7 @@ public class AppTest
      *
      * @param testName name of the test case
      */
-    public AppTest( String testName )
+    public AppUnitTest(String testName )
     {
         super( testName );
     }
@@ -25,7 +25,7 @@ public class AppTest
      */
     public static Test suite()
     {
-        return new TestSuite( AppTest.class );
+        return new TestSuite( AppUnitTest.class );
     }
 
     /**

core-java-modules/core-java-12/src/test/java/com/baeldung/string/StringAPIUnitTest.java

@@ -5,7 +5,7 @@ import static org.hamcrest.MatcherAssert.assertThat;
 
 import org.junit.Test;
 
-public class StringAPITest {
+public class StringAPIUnitTest {
 
     @Test
     public void whenPositiveArgument_thenReturnIndentedString() {

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/record/PersonUnitTest.java

@@ -7,7 +7,7 @@ import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
 
-public class PersonTest {
+public class PersonUnitTest {
 
     @Test
     public void givenSameNameAndAddress_whenEquals_thenPersonsEqual() {

core-java-modules/core-java-9-jigsaw/src/modules/com.baeldung.student.service.dbimpl/com/baeldung/student/service/dbimpl/StudentDbService.java

@@ -19,12 +19,12 @@ public class StudentDbService implements StudentService {
     }
 
     public Student update(Student student) {
-        logger.log(Level.INFO, "Updating sutdent in DB...");
+        logger.log(Level.INFO, "Updating student in DB...");
         return student;
     }
 
     public String delete(String registrationId) {
-        logger.log(Level.INFO, "Deleteing sutdent in DB...");
+        logger.log(Level.INFO, "Deleting student in DB...");
         return registrationId;
     }
 }

core-java-modules/core-java-9/pom.xml

@@ -44,6 +44,16 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.11</version>
+        </dependency>
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>2.7</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -77,6 +87,7 @@
         <maven.compiler.target>1.9</maven.compiler.target>
         <guava.version>25.1-jre</guava.version>
         <commons-collections4.version>4.1</commons-collections4.version>
+        <commons-collections3.version>3.2.2</commons-collections3.version>
     </properties>
 
 </project>

core-java-modules/core-java-9/src/test/java/com/baeldung/java9/methodhandles/MethodHandlesUnitTest.java

@@ -17,7 +17,7 @@ import org.junit.Test;
 /**
  * Test case for the {@link MethodHandles} API
  */
-public class MethodHandlesTest {
+public class MethodHandlesUnitTest {
 
     @Test
     public void givenConcatMethodHandle_whenInvoked_thenCorrectlyConcatenated() throws Throwable {

core-java-modules/core-java-arrays-guides/README.md

@@ -6,3 +6,4 @@ This module contains complete guides about arrays in Java
 - [Arrays in Java: A Reference Guide](https://www.baeldung.com/java-arrays-guide)
 - [Guide to the java.util.Arrays Class](https://www.baeldung.com/java-util-arrays)
 - [What is \[Ljava.lang.Object;?](https://www.baeldung.com/java-tostring-array)
+- [Guide to ArrayStoreException](https://www.baeldung.com/java-arraystoreexception)

core-java-modules/core-java-collections-3/README.md

@@ -13,3 +13,4 @@
 - [Quick Guide to the Java Stack](https://www.baeldung.com/java-stack)
 - [Convert an Array of Primitives to a List](https://www.baeldung.com/java-primitive-array-to-list)
 - [A Guide to BitSet in Java](https://www.baeldung.com/java-bitset)
+- [Get the First Key and Value From a HashMap](https://www.baeldung.com/java-hashmap-get-first-entry)

core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/removeallperformance/HashSetBenchmark.java

@@ -0,0 +1,103 @@
+package com.baeldung.collections.removeallperformance;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.commons.lang3.RandomStringUtils;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+import com.baeldung.collections.containsperformance.Employee;
+
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Warmup(iterations = 5)
+public class HashSetBenchmark {
+
+    @State(Scope.Thread)
+    public static class MyState {
+        private Set<Employee> employeeSet1 = new HashSet<>();
+        private List<Employee> employeeList1 = new ArrayList<>();
+        private Set<Employee> employeeSet2 = new HashSet<>();
+        private List<Employee> employeeList2 = new ArrayList<>();
+        private Set<Employee> employeeSet3 = new HashSet<>();
+        private Set<Employee> employeeSet4 = new HashSet<>();
+
+        private long set1Size = 60000;
+        private long list1Size = 50000;
+        private long set2Size = 50000;
+        private long list2Size = 60000;
+        private long set3Size = 50000;
+        private long set4Size = 60000;
+
+        @Setup(Level.Trial)
+        public void setUp() {
+
+            for (long i = 0; i < set1Size; i++) {
+                employeeSet1.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+            for (long i = 0; i < list1Size; i++) {
+                employeeList1.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+            for (long i = 0; i < set2Size; i++) {
+                employeeSet2.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+            for (long i = 0; i < list2Size; i++) {
+                employeeList2.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+            
+            for (long i = 0; i < set3Size; i++) {
+                employeeSet3.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+            for (long i = 0; i < set4Size; i++) {
+                employeeSet4.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+        }
+
+    }
+
+    @Benchmark
+    public boolean given_SizeOfHashsetGreaterThanSizeOfCollection_When_RemoveAllFromHashSet_Then_GoodPerformance(MyState state) {
+        return state.employeeSet1.removeAll(state.employeeList1);
+    }
+
+    @Benchmark
+    public boolean given_SizeOfHashsetSmallerThanSizeOfCollection_When_RemoveAllFromHashSet_Then_BadPerformance(MyState state) {
+        return state.employeeSet2.removeAll(state.employeeList2);
+    }
+    
+    @Benchmark
+    public boolean given_SizeOfHashsetSmallerThanSizeOfAnotherHashSet_When_RemoveAllFromHashSet_Then_GoodPerformance(MyState state) {
+        return state.employeeSet3.removeAll(state.employeeSet4);
+    }
+
+    public static void main(String[] args) throws Exception {
+        Options options = new OptionsBuilder().include(HashSetBenchmark.class.getSimpleName())
+            .threads(1)
+            .forks(1)
+            .shouldFailOnError(true)
+            .shouldDoGC(true)
+            .jvmArgs("-server")
+            .build();
+        new Runner(options).run();
+    }
+
+}

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/hashset/HashSetUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.collections.hashset;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.jupiter.api.Test;
+
+class HashSetUnitTest {
+
+    @Test
+    void whenRemoveAllFromHashset_thenRemovesAllElementsFromHashsetThatArePresentInCollection() {
+        Set<Integer> set = new HashSet<>();
+        Collection<Integer> collection = new ArrayList<>();
+        set.add(1);
+        set.add(2);
+        set.add(3);
+        set.add(4);
+        collection.add(1);
+        collection.add(3);
+
+        set.removeAll(collection);
+
+        assertEquals(2, set.size());
+        Integer[] actualElements = new Integer[set.size()];
+        Integer[] expectedElements = new Integer[] { 2, 4 };
+        assertArrayEquals(expectedElements, set.toArray(actualElements));
+    }
+
+}

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/mapfirstpair/MapFirstPairUnitTest.java

@@ -15,21 +15,24 @@ import org.junit.Test;
 public class MapFirstPairUnitTest {
 
     private Map.Entry<Integer, String> getFirstPairUsingIterator(Map<Integer, String> map) {
-        if (map == null || map.size() == 0)
+        if (map == null || map.size() == 0) {
             return null;
+        }
 
         Iterator<Map.Entry<Integer, String>> iterator = map.entrySet()
             .iterator();
 
-        if (iterator.hasNext())
+        if (iterator.hasNext()) {
             return iterator.next();
+        }
 
         return null;
     }
 
     private Map.Entry<Integer, String> getFirstPairUsingStream(Map<Integer, String> map) {
-        if (map == null || map.size() == 0)
+        if (map == null || map.size() == 0) {
             return null;
+        }
 
         Set<Map.Entry<Integer, String>> entrySet = map.entrySet();
 

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/deadlockAndLivelock/LivelockExample.java

@@ -73,7 +73,7 @@ public class LivelockExample {
 
     public void tryLock(Lock lock, long millis) {
         try {
-            lock.tryLock(10, TimeUnit.MILLISECONDS);
+            lock.tryLock(millis, TimeUnit.MILLISECONDS);
         } catch (InterruptedException e) {
             e.printStackTrace();
         }

core-java-modules/core-java-concurrency-basic-2/README.md

@@ -11,4 +11,5 @@ This module contains articles about basic Java concurrency
 - [Life Cycle of a Thread in Java](https://www.baeldung.com/java-thread-lifecycle)
 - [Guide to AtomicMarkableReference](https://www.baeldung.com/java-atomicmarkablereference)
 - [Why are Local Variables Thread-Safe in Java](https://www.baeldung.com/java-local-variables-thread-safe)
+- [How to Stop Execution After a Certain Time in Java](https://www.baeldung.com/java-stop-execution-after-certain-time)
 - [[<-- Prev]](/core-java-modules/core-java-concurrency-basic)

core-java-modules/core-java-date-operations-1/src/test/java/com/baeldung/date/DateDiffUnitTest.java

@@ -1,6 +1,8 @@
 package com.baeldung.date;
 
-import static org.junit.Assert.assertEquals;
+import org.joda.time.Days;
+import org.joda.time.Minutes;
+import org.junit.Test;
 
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
@@ -16,7 +18,7 @@ import java.util.Locale;
 import java.util.TimeZone;
 import java.util.concurrent.TimeUnit;
 
-import org.junit.Test;
+import static org.junit.Assert.*;
 
 public class DateDiffUnitTest {
 
@@ -29,18 +31,39 @@ public class DateDiffUnitTest {
         long diffInMillies = Math.abs(secondDate.getTime() - firstDate.getTime());
         long diff = TimeUnit.DAYS.convert(diffInMillies, TimeUnit.MILLISECONDS);
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
-    public void givenTwoDatesInJava8_whenDifferentiating_thenWeGetSix() {
-        LocalDate now = LocalDate.now();
-        LocalDate sixDaysBehind = now.minusDays(6);
+    public void givenTwoDatesInJava8_whenUsingPeriodGetDays_thenWorks() {
+        LocalDate aDate = LocalDate.of(2020, 9, 11);
+        LocalDate sixDaysBehind = aDate.minusDays(6);
 
-        Period period = Period.between(now, sixDaysBehind);
+        Period period = Period.between(aDate, sixDaysBehind);
         int diff = Math.abs(period.getDays());
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
+    }
+
+    @Test
+    public void givenTwoDatesInJava8_whenUsingPeriodGetDays_thenDoesNotWork() {
+        LocalDate aDate = LocalDate.of(2020, 9, 11);
+        LocalDate sixtyDaysBehind = aDate.minusDays(60);
+        Period period = Period.between(aDate, sixtyDaysBehind);
+        int diff = Math.abs(period.getDays());
+        //not equals
+        assertNotEquals(60, diff);
+    }
+
+    @Test
+    public void givenTwoDatesInJava8_whenUsingPeriod_thenWeGet0Year1Month29Days() {
+        LocalDate aDate = LocalDate.of(2020, 9, 11);
+        LocalDate sixtyDaysBehind = aDate.minusDays(60);
+        Period period = Period.between(aDate, sixtyDaysBehind);
+        int years = Math.abs(period.getYears());
+        int months = Math.abs(period.getMonths());
+        int days = Math.abs(period.getDays());
+        assertArrayEquals(new int[] { 0, 1, 29 }, new int[] { years, months, days });
     }
 
     @Test
@@ -51,7 +74,7 @@ public class DateDiffUnitTest {
         Duration duration = Duration.between(now, sixMinutesBehind);
         long diff = Math.abs(duration.toMinutes());
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
@@ -61,7 +84,7 @@ public class DateDiffUnitTest {
 
         long diff = ChronoUnit.SECONDS.between(now, tenSecondsLater);
 
-        assertEquals(diff, 10);
+        assertEquals(10, diff);
     }
 
     @Test
@@ -69,9 +92,9 @@ public class DateDiffUnitTest {
         LocalDateTime ldt = LocalDateTime.now();
         ZonedDateTime now = ldt.atZone(ZoneId.of("America/Montreal"));
         ZonedDateTime sixDaysBehind = now.withZoneSameInstant(ZoneId.of("Asia/Singapore"))
-            .minusDays(6);
+                                         .minusDays(6);
         long diff = ChronoUnit.DAYS.between(sixDaysBehind, now);
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
@@ -81,7 +104,7 @@ public class DateDiffUnitTest {
 
         long diff = now.until(tenSecondsLater, ChronoUnit.SECONDS);
 
-        assertEquals(diff, 10);
+        assertEquals(10, diff);
     }
 
     @Test
@@ -89,10 +112,9 @@ public class DateDiffUnitTest {
         org.joda.time.LocalDate now = org.joda.time.LocalDate.now();
         org.joda.time.LocalDate sixDaysBehind = now.minusDays(6);
 
-        org.joda.time.Period period = new org.joda.time.Period(now, sixDaysBehind);
-        long diff = Math.abs(period.getDays());
+        long diff = Math.abs(Days.daysBetween(now, sixDaysBehind).getDays());
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
@@ -100,8 +122,9 @@ public class DateDiffUnitTest {
         org.joda.time.LocalDateTime now = org.joda.time.LocalDateTime.now();
         org.joda.time.LocalDateTime sixMinutesBehind = now.minusMinutes(6);
 
-        org.joda.time.Period period = new org.joda.time.Period(now, sixMinutesBehind);
-        long diff = Math.abs(period.getDays());
+        long diff = Math.abs(Minutes.minutesBetween(now, sixMinutesBehind).getMinutes());
+        assertEquals(6, diff);
+
     }
 
     @Test
@@ -111,6 +134,6 @@ public class DateDiffUnitTest {
 
         long diff = Math.abs(now.numDaysFrom(sixDaysBehind));
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
-}
+}

core-java-modules/core-java-datetime-string/src/test/java/com/baeldung/timestamp/TimestampToStringConverterUnitTest.java

@@ -6,7 +6,7 @@ import org.junit.jupiter.api.Test;
 import java.sql.Timestamp;
 import java.time.format.DateTimeFormatter;
 
-public class TimestampToStringConverterTest {
+public class TimestampToStringConverterUnitTest {
 
     @Test
     public void givenDatePattern_whenFormatting_thenResultingStringIsCorrect() {

core-java-modules/core-java-exceptions-3/README.md

@@ -1,3 +1,5 @@
 ### Relevant Articles:
 
 - [NoSuchMethodError in Java](https://www.baeldung.com/java-nosuchmethod-error)
+- [IllegalArgumentException or NullPointerException for a Null Parameter?](https://www.baeldung.com/java-illegalargumentexception-or-nullpointerexception)
+- [IllegalMonitorStateException in Java](https://www.baeldung.com/java-illegalmonitorstateexception)

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/classcastexception/Animal.java

@@ -0,0 +1,6 @@
+package com.baeldung.exceptions.classcastexception;
+
+public interface Animal {
+
+    String getName();
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/classcastexception/Box.java

@@ -0,0 +1,14 @@
+package com.baeldung.exceptions.classcastexception;
+
+public class Box<T> {
+
+    private T content;
+
+    public T getContent() {
+        return content;
+    }
+
+    public void setContent(T content) {
+        this.content = content;
+    }
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/classcastexception/Frog.java

@@ -0,0 +1,9 @@
+package com.baeldung.exceptions.classcastexception;
+
+public class Frog extends Reptile {
+
+    @Override
+    public String getName() {
+        return super.getName() + ": Frog";
+    }
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/classcastexception/Mammal.java

@@ -0,0 +1,9 @@
+package com.baeldung.exceptions.classcastexception;
+
+public class Mammal implements Animal {
+
+    @Override
+    public String getName() {
+        return "Mammal";
+    }
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/classcastexception/Reptile.java

@@ -0,0 +1,9 @@
+package com.baeldung.exceptions.classcastexception;
+
+public class Reptile implements Animal {
+
+    @Override
+    public String getName() {
+        return "Reptile";
+    }
+}

core-java-modules/core-java-exceptions-3/src/test/java/com/baeldung/exceptions/classcastexception/CheckedCastsUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.exceptions.classcastexception;
+
+import org.junit.Test;
+
+import java.io.Serializable;
+
+public class CheckedCastsUnitTest {
+
+    @Test(expected = ClassCastException.class)
+    public void givenBaseTypeVariableReferencingChildInstance_whenCastToIncompatibleSubtype_thenClassCastException() {
+        Animal animal = new Frog();
+
+        //A checked downcast to Mammal is incompatible from Frog because Frog is not a subtype of Mammal.
+        Mammal mammal = (Mammal) animal;
+    }
+
+    @Test(expected = ClassCastException.class)
+    public void givenBaseTypeVariableReferencingChildInstance_whenCastToIncompatibleInterface_thenClassCastException() {
+        Animal animal = new Frog();
+
+        //A checked cast to Serializable is incompatible from Frog because Frog is not a subtype of Serializable.
+        Serializable serial = (Serializable) animal;
+    }
+
+    @Test(expected = ClassCastException.class)
+    public void givenObjectVariableReferencingPrimitiveArray_whenCastToBoxedTypeArray_thenClassCastException() {
+        Object primitives = new int[1];
+
+        //A checked cast to Integer[] is incompatible from primitive arrays. Auto-boxing does not work for arrays.
+        Integer[] integers = (Integer[]) primitives;
+    }
+
+    @Test(expected = ClassCastException.class)
+    public void givenObjectVariableReferencingPrimitiveArray_whenCastToPromotedTypeArray_thenClassCastException() {
+        Object primitives = new int[1];
+
+        //A checked cast to long[] is incompatible from int[]. Type promotion does not work for arrays.
+        long[] longs = (long[]) primitives;
+    }
+}

core-java-modules/core-java-exceptions-3/src/test/java/com/baeldung/exceptions/classcastexception/GenericConversionUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.exceptions.classcastexception;
+
+import org.junit.Test;
+
+public class GenericConversionUnitTest {
+
+    @Test(expected = ClassCastException.class)
+    public void givenIncompatibleType_whenConvertInstanceOfObject_thenClassCastException() {
+        // Should have been null, but due to type erasure, inside convertInstanceOfObject,
+        // it will attempt to cast to Object instead of String, so it casts to Object, which is always possible.
+        String shouldBeNull = convertInstanceOfObject(123);
+    }
+
+    public static <T> T convertInstanceOfObject(Object o) {
+        try {
+            return (T) o; // Casts to Object due to type erasure
+        } catch (ClassCastException e) {
+            return null; // Will never reach this
+        }
+    }
+}

core-java-modules/core-java-exceptions-3/src/test/java/com/baeldung/exceptions/classcastexception/UncheckedConversionUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.exceptions.classcastexception;
+
+import org.junit.Test;
+
+public class UncheckedConversionUnitTest {
+
+    @Test(expected = ClassCastException.class)
+    public void givenPollutedGenericType_whenGetProperty_thenClassCastException() {
+        Box<Long> originalBox = new Box<>();
+        Box raw = originalBox;
+        raw.setContent(2.5);
+        Box<Long> bound = (Box<Long>) raw;
+
+        //An incompatible element was found in the raw box.
+        Long content = bound.getContent();
+    }
+}

core-java-modules/core-java-io-3/README.md

@@ -9,4 +9,7 @@ This module contains articles about core Java input and output (IO)
 - [Check If a File or Directory Exists in Java](https://www.baeldung.com/java-file-directory-exists)
 - [Copy a Directory in Java](https://www.baeldung.com/java-copy-directory)
 - [Java Files Open Options](https://www.baeldung.com/java-file-options)
+- [Creating Temporary Directories in Java](https://www.baeldung.com/java-temp-directories)
+- [Reading a Line at a Given Line Number From a File in Java](https://www.baeldung.com/java-read-line-at-number)
+- [Find the Last Modified File in a Directory with Java](https://www.baeldung.com/java-last-modified-file)
 - [[<-- Prev]](/core-java-modules/core-java-io-2)

core-java-modules/core-java-io-3/src/main/java/com/baeldung/lastmodifiedfile/LastModifiedFileApp.java

@@ -0,0 +1,61 @@
+package com.baeldung.lastmodifiedfile;
+
+import java.io.File;
+import java.io.FileFilter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.Optional;
+
+import org.apache.commons.io.comparator.LastModifiedFileComparator;
+import org.apache.commons.io.filefilter.FileFilterUtils;
+
+public class LastModifiedFileApp {
+
+    public static File findUsingIOApi(String sdir) {
+        File dir = new File(sdir);
+        if (dir.isDirectory()) {
+            Optional<File> opFile = Arrays.stream(dir.listFiles(File::isFile))
+              .max((f1, f2) -> Long.compare(f1.lastModified(), f2.lastModified()));
+
+            if (opFile.isPresent()) {
+                return opFile.get();
+            }
+        }
+
+        return null;
+    }
+
+    public static Path findUsingNIOApi(String sdir) throws IOException {
+        Path dir = Paths.get(sdir);
+        if (Files.isDirectory(dir)) {
+            Optional<Path> opPath = Files.list(dir)
+              .filter(p -> !Files.isDirectory(p))
+              .sorted((p1, p2) -> Long.valueOf(p2.toFile().lastModified())
+                .compareTo(p1.toFile().lastModified()))
+              .findFirst();
+
+            if (opPath.isPresent()) {
+                return opPath.get();
+            }
+        }
+
+        return null;
+    }
+
+    public static File findUsingCommonsIO(String sdir) {
+        File dir = new File(sdir);
+        if (dir.isDirectory()) {
+            File[] dirFiles = dir.listFiles((FileFilter) FileFilterUtils.fileFileFilter());
+            if (dirFiles != null && dirFiles.length > 0) {
+                Arrays.sort(dirFiles, LastModifiedFileComparator.LASTMODIFIED_REVERSE);
+                return dirFiles[0];
+            }
+        }
+
+        return null;
+    }
+
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/createfile/CreateFileUnitTest.java

@@ -6,6 +6,7 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import java.io.File;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -37,6 +38,12 @@ public class CreateFileUnitTest {
         assertTrue(success);
     }
 
+    @Test
+    void givenUsingFileOutputStream_whenCreatingFile_thenCorrect() throws IOException {
+        try(FileOutputStream fileOutputStream = new FileOutputStream(FILE_NAME)){
+        }
+    }
+
     @Test
     public void givenUsingGuava_whenCreatingFile_thenCorrect() throws IOException {
         com.google.common.io.Files.touch(new File(FILE_NAME));

core-java-modules/core-java-io-3/src/test/java/com/baeldung/emptiness/DirectoryEmptinessUnitTest.java

@@ -4,6 +4,7 @@ import org.junit.Test;
 
 import java.io.File;
 import java.io.IOException;
+import java.net.URISyntaxException;
 import java.nio.file.DirectoryStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -20,8 +21,8 @@ public class DirectoryEmptinessUnitTest {
     }
 
     @Test
-    public void givenPath_whenNotDirectory_thenReturnsFalse() throws IOException {
-        Path aFile = Paths.get(getClass().getResource("/notDir.txt").getPath());
+    public void givenPath_whenNotDirectory_thenReturnsFalse() throws IOException, URISyntaxException {
+        Path aFile = Paths.get(getClass().getResource("/notDir.txt").toURI());
         assertThat(isEmpty(aFile)).isFalse();
     }
 

core-java-modules/core-java-io-3/src/test/java/com/baeldung/existence/ExistenceUnitTest.java

@@ -4,10 +4,7 @@ import org.junit.Test;
 
 import java.io.File;
 import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.LinkOption;
-import java.nio.file.Path;
-import java.nio.file.Paths;
+import java.nio.file.*;
 import java.util.concurrent.ThreadLocalRandom;
 
 import static org.junit.Assert.assertFalse;
@@ -47,8 +44,18 @@ public class ExistenceUnitTest {
     public void givenSymbolicLink_whenTargetDoesNotExists_thenFollowOrNotBasedOnTheOptions() throws IOException {
         Path target = Files.createTempFile("baeldung", "target");
         Path symbol = Paths.get("test-link-" + ThreadLocalRandom.current().nextInt());
+        Path symbolicLink = null;
+
+        try {
+            symbolicLink = Files.createSymbolicLink(symbol, target);
+        } catch (FileSystemException ex) {
+            System.out.println("Your OS security policy prevents the current user from creating symbolic links.\n" +
+                    "Most probably you're running Windows with UAC.\n" +
+                    "If this is the case, please see - https://docs.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/create-symbolic-links\n" +
+                    "You must change your security settings to run this test under Windows.");
+            return;
+        }
 
-        Path symbolicLink = Files.createSymbolicLink(symbol, target);
         assertTrue(Files.exists(symbolicLink));
         assertTrue(Files.isSymbolicLink(symbolicLink));
         assertFalse(Files.isSymbolicLink(target));

core-java-modules/core-java-io-3/src/test/java/com/baeldung/lastmodifiedfile/LastModifiedFileAppUnitTest.java

@@ -0,0 +1,78 @@
+package com.baeldung.lastmodifiedfile;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import org.apache.commons.io.FileUtils;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+public class LastModifiedFileAppUnitTest {
+
+    private final static String SOURCEDIRECTORY = "src/test/resources/lastmodfiles";
+
+    @BeforeAll
+    public static void setUpFiles() throws IOException, InterruptedException {
+        File srcDir = new File(SOURCEDIRECTORY);
+        if (!srcDir.exists()) {
+            srcDir.mkdir();
+        }
+
+        FileUtils.cleanDirectory(srcDir);
+
+        File file01 = new File(SOURCEDIRECTORY + "/file01.txt");
+        file01.createNewFile();
+
+        Thread.sleep(2000);
+
+        File file02 = new File(SOURCEDIRECTORY + "/file02.txt");
+        file02.createNewFile();
+
+        Thread.sleep(2000);
+
+        File file03 = new File(SOURCEDIRECTORY + "/file03.txt");
+        file03.createNewFile();
+
+        Thread.sleep(2000);
+
+        Files.write(Paths.get(SOURCEDIRECTORY + "/file02.txt"), "Hello File02".getBytes());
+
+    }
+
+    @Test
+    public void givenDirectory_whenUsingIoApi_thenFindLastModfile() throws IOException {
+        File lastModFile = LastModifiedFileApp.findUsingIOApi(SOURCEDIRECTORY);
+
+        assertThat(lastModFile).isNotNull();
+        assertThat(lastModFile.getName()).isEqualTo("file02.txt");
+    }
+
+    @Test
+    public void givenDirectory_whenUsingNioApi_thenFindLastModfile() throws IOException {
+        Path lastModPath = LastModifiedFileApp.findUsingNIOApi(SOURCEDIRECTORY);
+
+        assertThat(lastModPath).isNotNull();
+        assertThat(lastModPath.toFile().getName()).isEqualTo("file02.txt");
+    }
+
+    @Test
+    public void givenDirectory_whenUsingApacheCommons_thenFindLastModfile() throws IOException {
+        File lastModFile = LastModifiedFileApp.findUsingCommonsIO(SOURCEDIRECTORY);
+
+        assertThat(lastModFile).isNotNull();
+        assertThat(lastModFile.getName()).isEqualTo("file02.txt");
+    }
+
+    @AfterAll
+    public static void cleanUp() throws IOException {
+        File srcDir = new File(SOURCEDIRECTORY);
+        FileUtils.deleteDirectory(srcDir);
+    }
+
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/tempdirectory/TemporaryDirectoriesUnitTest.java

@@ -4,6 +4,7 @@ import org.apache.commons.io.FileUtils;
 import org.junit.Test;
 
 import java.io.IOException;
+import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -66,10 +67,16 @@ public class TemporaryDirectoriesUnitTest {
 
     @Test
     public void givenTempDirWithPrefixWithFileAttrs_whenCreatePlainJava_thenAttributesAreSet() throws IOException {
-        final FileAttribute<Set<PosixFilePermission>> attrs = PosixFilePermissions.asFileAttribute(PosixFilePermissions.fromString("r--------"));
+        boolean isPosix = FileSystems.getDefault().supportedFileAttributeViews().contains("posix");
 
-        final Path tmpdir = Files.createTempDirectory(Paths.get("target"), "tmpDirPrefix", attrs);
-        assertThat(tmpdir.toFile().getPath()).startsWith("target");
-        assertThat(tmpdir.toFile().canWrite()).isFalse();
+        if(!isPosix){
+            System.out.println("You must be under a Posix Compliant Filesystem to run this test.");
+        } else {
+            final FileAttribute<Set<PosixFilePermission>> attrs = PosixFilePermissions.asFileAttribute(PosixFilePermissions.fromString("r--------"));
+
+            final Path tmpdir = Files.createTempDirectory(Paths.get("target"), "tmpDirPrefix", attrs);
+            assertThat(tmpdir.toFile().getPath()).startsWith("target");
+            assertThat(tmpdir.toFile().canWrite()).isFalse();
+        }
     }
 }

core-java-modules/core-java-jpms/decoupling-pattern1/consumermodule/pom.xml

@@ -17,7 +17,7 @@
     <dependencies>
         <dependency>
             <groupId>com.baeldung.servicemodule</groupId>
-            <artifactId>servicemodule</artifactId>
+            <artifactId>servicemodule1</artifactId>
             <version>${servicemodule.version}</version>
         </dependency>
     </dependencies>

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/pom.xml

@@ -4,7 +4,8 @@
     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>servicemodule</artifactId>
+    <groupId>com.baeldung.servicemodule</groupId>
+    <artifactId>servicemodule1</artifactId>
     <packaging>jar</packaging>
 
     <parent>

core-java-modules/core-java-jpms/decoupling-pattern2/providermodule/pom.xml

@@ -17,7 +17,7 @@
     <dependencies>
         <dependency>
             <groupId>com.baeldung.servicemodule</groupId>
-            <artifactId>servicemodule</artifactId>
+            <artifactId>servicemodule2</artifactId>
             <version>${servicemodule.version}</version>
         </dependency>
     </dependencies>

core-java-modules/core-java-jpms/decoupling-pattern2/servicemodule/pom.xml

@@ -4,7 +4,8 @@
     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>servicemodule</artifactId>
+    <groupId>com.baeldung.servicemodule</groupId>
+    <artifactId>servicemodule2</artifactId>
     <version>1.0</version>
 
     <parent>

core-java-modules/core-java-lang-3/README.md

@@ -5,4 +5,6 @@ This module contains articles about core features in the Java language
 - [Class.isInstance vs Class.isAssignableFrom](https://www.baeldung.com/java-isinstance-isassignablefrom)
 - [Converting a Java String Into a Boolean](https://www.baeldung.com/java-string-to-boolean)
 - [When are Static Variables Initialized in Java?](https://www.baeldung.com/java-static-variables-initialization)
+- [Checking if a Class Exists in Java](https://www.baeldung.com/java-check-class-exists)
+- [The Difference Between a.getClass() and A.class in Java](https://www.baeldung.com/java-getclass-vs-class)
 - [[<-- Prev]](/core-java-modules/core-java-lang-2)

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/Calculator.java

@@ -0,0 +1,37 @@
+package com.baeldung.constantspatterns;
+
+public class Calculator {
+    public static final double PI = 3.14159265359;
+    private static final double UPPER_LIMIT = 0x1.fffffffffffffP+1023;
+
+    public enum Operation {
+        ADD, SUBTRACT, DIVIDE, MULTIPLY
+    }
+
+    public double operateOnTwoNumbers(double numberOne, double numberTwo, Operation operation) {
+        if (numberOne > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberOne' is too large");
+        }
+        if (numberTwo > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberTwo' is too large");
+        }
+        double answer = 0;
+
+        switch (operation) {
+        case ADD:
+            answer = numberOne + numberTwo;
+            break;
+        case SUBTRACT:
+            answer = numberOne - numberTwo;
+            break;
+        case DIVIDE:
+            answer = numberOne / numberTwo;
+            break;
+        case MULTIPLY:
+            answer = numberOne * numberTwo;
+            break;
+        }
+
+        return answer;
+    }
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/CalculatorConstants.java

@@ -0,0 +1,10 @@
+package com.baeldung.constantspatterns;
+
+public interface CalculatorConstants {
+    double PI = 3.14159265359;
+    double UPPER_LIMIT = 0x1.fffffffffffffP+1023;
+
+    enum Operation {
+        ADD, SUBTRACT, MULTIPLY, DIVIDE
+    };
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/GeometryCalculator.java

@@ -0,0 +1,32 @@
+package com.baeldung.constantspatterns;
+
+public class GeometryCalculator implements CalculatorConstants {
+    public static final double UPPER_LIMIT = 100000000000000000000.0;
+
+    public double operateOnTwoNumbers(double numberOne, double numberTwo, Operation operation) {
+        if (numberOne > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberOne' is too large");
+        }
+        if (numberTwo > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberTwo' is too large");
+        }
+        double answer = 0;
+
+        switch (operation) {
+        case ADD:
+            answer = numberOne + numberTwo;
+            break;
+        case SUBTRACT:
+            answer = numberOne - numberTwo;
+            break;
+        case DIVIDE:
+            answer = numberOne / numberTwo;
+            break;
+        case MULTIPLY:
+            answer = numberOne * numberTwo;
+            break;
+        }
+
+        return answer;
+    }
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/calculations/MathConstants.java

@@ -0,0 +1,16 @@
+package com.baeldung.constantspatterns.calculations;
+
+public final class MathConstants {
+    public static final double PI = 3.14159265359;
+    static final double GOLDEN_RATIO = 1.6180;
+    static final double GRAVITATIONAL_ACCELERATION = 9.8;
+    static final double EULERS_NUMBER = 2.7182818284590452353602874713527;
+
+    public enum Operation {
+        ADD, SUBTRACT, DIVIDE, MULTIPLY
+    }
+
+    private MathConstants() {
+
+    }
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/getclassobject/Animal.java

@@ -0,0 +1,5 @@
+package com.baeldung.getclassobject;
+
+public class Animal {
+    protected int numberOfEyes;
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/getclassobject/Monkey.java

@@ -0,0 +1,4 @@
+package com.baeldung.getclassobject;
+
+public class Monkey extends Animal {
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/getclassobject/SomeAbstractClass.java

@@ -0,0 +1,4 @@
+package com.baeldung.getclassobject;
+
+public abstract class SomeAbstractClass {
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/getclassobject/SomeInterface.java

@@ -0,0 +1,4 @@
+package com.baeldung.getclassobject;
+
+interface SomeInterface {
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/getclassobject/SomeUtils.java

@@ -0,0 +1,9 @@
+package com.baeldung.getclassobject;
+
+public class SomeUtils {
+    private SomeUtils() {
+        throw new RuntimeException("This Util class is not allowed to be instantiated!");
+    }
+    //  public static utilMethods
+    //  ...
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/constantspatterns/ConstantPatternUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.constantspatterns;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.Test;
+
+public class ConstantPatternUnitTest {
+    @Test
+    public void givenTwoNumbersAndAdd_whenCallingCalculatorOperatOneTwoNumbers_thenCorrectAnswerReturned() {
+        Calculator calculator = new Calculator();
+        double expected = 4;
+        double answer = calculator.operateOnTwoNumbers(2, 2, Calculator.Operation.ADD);
+        assertEquals(expected, answer);
+    }
+    
+    @Test
+    public void givenTwoNumbersAndAdd_whenCallingGeometryCalculatorOperatOneTwoNumbers_thenCorrectAnswerReturned() {
+        GeometryCalculator calculator = new GeometryCalculator();
+        double expected = 4;
+        double answer = calculator.operateOnTwoNumbers(2, 2, GeometryCalculator.Operation.ADD);
+        assertEquals(expected, answer);
+    }
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/getclassobject/GetClassObjectUnitTest.java

@@ -0,0 +1,55 @@
+package com.baeldung.getclassobject;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class GetClassObjectUnitTest {
+    @Test
+    public void givenObjectAndType_whenGettingClassObject_thenTwoMethodsHaveTheSameResult() {
+        String str = "I am an object of the String class";
+        Class fromStrObject = str.getClass();
+        Class clazz = String.class;
+        assertSame(fromStrObject, clazz);
+    }
+
+    @Test
+    public void givenClassInheritance_whenGettingRuntimeTypeAndStaticType_thenGetDifferentResult() {
+        Animal animal = new Monkey();
+        Class runtimeType = animal.getClass();
+        Class staticType = Animal.class;
+        //Not equals
+        assertNotEquals(staticType, runtimeType);
+
+        Class monkeyClass = Monkey.class;
+        assertSame(runtimeType, monkeyClass);
+    }
+
+    @Test
+    public void givenPrimitiveType_whenGettingClassObject_thenOnlyStaticTypeWorks() {
+        int number = 7;
+        // Class numberClass = number.getClass();   <-- compilation error
+        Class intType = int.class;
+
+        assertNotNull(intType);
+        assertEquals("int", intType.getName());
+        assertTrue(intType.isPrimitive());
+    }
+
+    @Test
+    public void givenTypeCannotInstantiate_whenGetTypeStatically_thenGetTypesSuccefully() {
+        Class interfaceType = SomeInterface.class;
+        Class abstractClassType = SomeAbstractClass.class;
+        Class utilClassType = SomeUtils.class;
+
+        assertNotNull(interfaceType);
+        assertTrue(interfaceType.isInterface());
+        assertEquals("SomeInterface", interfaceType.getSimpleName());
+
+        assertNotNull(abstractClassType);
+        assertEquals("SomeAbstractClass", abstractClassType.getSimpleName());
+
+        assertNotNull(utilClassType);
+        assertEquals("SomeUtils", utilClassType.getSimpleName());
+    }
+}

core-java-modules/core-java-lang-math-2/README.md

@@ -13,4 +13,5 @@
 - [Convert Latitude and Longitude to a 2D Point in Java](https://www.baeldung.com/java-convert-latitude-longitude)
 - [Debugging with Eclipse](https://www.baeldung.com/eclipse-debugging)
 - [Matrix Multiplication in Java](https://www.baeldung.com/java-matrix-multiplication)
+- [Largest Power of 2 That Is Less Than the Given Number](https://www.baeldung.com/java-largest-power-of-2-less-than-number)
 - More articles: [[<-- Prev]](/core-java-modules/core-java-lang-math)

core-java-modules/core-java-lang-oop-methods/README.md

@@ -9,3 +9,4 @@ This module contains articles about methods in Java
 - [Java equals() and hashCode() Contracts](https://www.baeldung.com/java-equals-hashcode-contracts)
 - [Guide to hashCode() in Java](https://www.baeldung.com/java-hashcode)
 - [The Covariant Return Type in Java](https://www.baeldung.com/java-covariant-return-type)
+- [Does a Method’s Signature Include the Return Type in Java?](https://www.baeldung.com/java-method-signature-return-type)

core-java-modules/core-java-lang-oop-methods/src/main/java/com/baeldung/signature/OverloadingErrors.java

@@ -0,0 +1,72 @@
+package com.baeldung.signature;
+
+import java.io.Serializable;
+
+public class OverloadingErrors<T extends Serializable> {
+
+    public void print() {
+        System.out.println("Signature is: print()");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from return type
+    public int print() {
+        System.out.println("Signature is: print()");
+        return 0;
+    }
+    */
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from modifiers
+    private final void print() {
+        System.out.println("Signature is: print()");
+    }
+    */
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from thrown exception declaration
+    public void print() throws IllegalStateException {
+        System.out.println("Signature is: print()");
+        throw new IllegalStateException();
+    }
+    */
+
+    public void print(int parameter) {
+        System.out.println("Signature is: print(int)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print(int) is already defined in class
+    // The method signature is independent from parameter names
+    public void print(int anotherParameter) {
+        System.out.println("Signature is: print(int)");
+    }
+    */
+
+    public void printElement(T t) {
+        System.out.println("Signature is: printElement(T)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: name clash: printElement(java.io.Serializable) and printElement(T) have the same erasure
+    // Even though the signatures appear different, the compiler cannot statically bind the correct method after type erasure
+    public void printElement(Serializable o) {
+        System.out.println("Signature is: printElement(Serializable)");
+    }
+    */
+
+    public void print(Object... parameter) {
+        System.out.println("Signature is: print(Object...)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java cannot declare both sum(Object...) and sum(Object[])
+    // Even though the signatures appear different, after compilation they both resolve to sum(Object[])
+    public void print(Object[] parameter) {
+        System.out.println("Signature is: print(Object[])");
+    }
+    */
+}

core-java-modules/core-java-lang-oop-methods/src/main/java/com/baeldung/signature/StaticBinding.java

@@ -0,0 +1,46 @@
+package com.baeldung.signature;
+
+public class StaticBinding {
+
+    public Number sum(Integer term1, Integer term2) {
+        System.out.println("Adding integers");
+        return term1 + term2;
+    }
+
+    public Number sum(Number term1, Number term2) {
+        System.out.println("Adding numbers");
+        return term1.doubleValue() + term2.doubleValue();
+    }
+
+    public Number sum(Object term1, Object term2) {
+        System.out.println("Adding objects");
+        return term1.hashCode() + term2.hashCode();
+    }
+
+    public Number sum(Object term1, Object... term2) {
+        System.out.println("Adding variable arguments: " + term2.length);
+        int result = term1.hashCode();
+        for (Object o : term2) {
+            result += o.hashCode();
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        StaticBinding obj = new StaticBinding();
+
+        obj.sum(2, 3); // "Adding integers" due to auto-boxing from int to Integer
+        obj.sum(Integer.valueOf(2), Integer.valueOf(3)); // "Adding integers" due to exact parameter types
+        obj.sum(2, 0x1); // "Adding integers" due to type promotion from byte to int
+
+        obj.sum((Number) 2, (Number) 3); // "Adding numbers" due to explicit cast to Number
+        obj.sum(2.0d, 3.0d); // "Adding numbers" due to auto-boxing from double to Double
+        obj.sum(Float.valueOf(2), Float.valueOf(3)); // "Adding numbers" due to polimorphism
+
+        obj.sum((Object) 2, (Object) 3); // "Adding objects" due to explicit cast to Object
+        obj.sum(2, "John"); // "Adding objects" due to polimorphism
+
+        obj.sum(new Object(), new Object(), new Object()); // "Adding variable arguments 2"
+        obj.sum(new Object(), new Object[]{new Object()}); // "Adding variable arguments 1"
+    }
+}

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

@@ -13,4 +13,5 @@ This module contains articles about networking in Java
 - [Download a File from an URL in Java](https://www.baeldung.com/java-download-file)
 - [Handling java.net.ConnectException](https://www.baeldung.com/java-net-connectexception)
 - [Getting MAC addresses in Java](https://www.baeldung.com/java-mac-address)
+- [Sending Emails with Attachments in Java](https://www.baeldung.com/java-send-emails-attachments)
 - [[<-- Prev]](/core-java-modules/core-java-networking)

core-java-modules/core-java-os/src/test/java/com/baeldung/core/pwd/CurrentDirectoryFetcherUnitTest.java

@@ -4,7 +4,7 @@ import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
 
-public class CurrentDirectoryFetcherTest {
+public class CurrentDirectoryFetcherUnitTest {
 
     private static final String CURRENT_DIR = "core-java-os";
 

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

@@ -2,3 +2,5 @@
 
 - [Reading the Value of ‘private’ Fields from a Different Class in Java](https://www.baeldung.com/java-reflection-read-private-field-value)
 - [Set Field Value With Reflection](https://www.baeldung.com/java-set-private-field-value)
+- [Checking If a Method is Static Using Reflection in Java](https://www.baeldung.com/java-check-method-is-static)
+- [Checking if a Java Class is ‘abstract’ Using Reflection](https://www.baeldung.com/java-reflection-is-class-abstract)

core-java-modules/core-java-reflection-2/src/main/java/com/baeldung/reflection/check/abstractclass/AbstractExample.java

@@ -0,0 +1,15 @@
+package com.baeldung.reflection.check.abstractclass;
+
+import java.time.LocalDate;
+import java.time.LocalTime;
+
+public abstract class AbstractExample {
+
+    public static String getAuthorName() {
+        return "Umang Budhwar";
+    }
+
+    public abstract LocalDate getLocalDate();
+
+    public abstract LocalTime getLocalTime();
+}

core-java-modules/core-java-reflection-2/src/main/java/com/baeldung/reflection/check/staticmethods/StaticUtility.java

@@ -0,0 +1,19 @@
+package com.baeldung.reflection.check.staticmethods;
+
+import java.time.LocalDate;
+import java.time.LocalTime;
+
+public class StaticUtility {
+
+    public static String getAuthorName() {
+        return "Umang Budhwar";
+    }
+
+    public static LocalDate getLocalDate() {
+        return LocalDate.now();
+    }
+
+    public static LocalTime getLocalTime() {
+        return LocalTime.now();
+    }
+}

core-java-modules/core-java-reflection-2/src/test/java/com/baeldung/reflection/check/abstractclass/AbstractExampleUnitTest.java

@@ -0,0 +1,16 @@
+package com.baeldung.reflection.check.abstractclass;
+
+import java.lang.reflect.Modifier;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class AbstractExampleUnitTest {
+
+    @Test
+    void givenAbstractClass_whenCheckModifierIsAbstract_thenTrue() throws Exception {
+        Class<AbstractExample> clazz = AbstractExample.class;
+        Assertions.assertTrue(Modifier.isAbstract(clazz.getModifiers()));
+    }
+
+}

core-java-modules/core-java-reflection-2/src/test/java/com/baeldung/reflection/check/staticmethods/StaticUtilityUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.reflection.check.staticmethods;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class StaticUtilityUnitTest {
+
+    @Test
+    void whenCheckStaticMethod_ThenSuccess() throws Exception {
+        Method method = StaticUtility.class.getMethod("getAuthorName", null);
+        Assertions.assertTrue(Modifier.isStatic(method.getModifiers()));
+    }
+
+    @Test
+    void whenCheckAllStaticMethods_thenSuccess() {
+        List<Method> methodList = Arrays.asList(StaticUtility.class.getMethods())
+          .stream()
+          .filter(method -> Modifier.isStatic(method.getModifiers()))
+          .collect(Collectors.toList());
+        Assertions.assertEquals(3, methodList.size());
+    }
+
+}

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

@@ -10,4 +10,6 @@ This module contains articles about core Java Security
 - [SHA-256 and SHA3-256 Hashing in Java](https://www.baeldung.com/sha-256-hashing-java)
 - [Checksums in Java](https://www.baeldung.com/java-checksums)
 - [How to Read PEM File to Get Public and Private Keys](https://www.baeldung.com/java-read-pem-file-keys)
+- [Listing the Available Cipher Algorithms](https://www.baeldung.com/java-list-cipher-algorithms)
+- [Get a List of Trusted Certificates in Java](https://www.baeldung.com/java-list-trusted-certificates)
 - More articles: [[<-- prev]](/core-java-modules/core-java-security)

core-java-modules/core-java-security-2/src/main/java/com/baeldung/hashing/SHACommonUtils.java

@@ -3,7 +3,7 @@ package com.baeldung.hashing;
 class SHACommonUtils {
 
     public static String bytesToHex(byte[] hash) {
-        StringBuffer hexString = new StringBuffer();
+        StringBuilder hexString = new StringBuilder(2 * hash.length);
         for (byte h : hash) {
             String hex = Integer.toHexString(0xff & h);
             if (hex.length() == 1)

core-java-modules/core-java-security-2/src/test/java/com/baeldung/cipher/AvailableCiphersUnitTest.java

@@ -0,0 +1,35 @@
+package com.baeldung.cipher;
+
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.security.Provider;
+import java.security.Security;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class AvailableCiphersUnitTest {
+    private final Logger logger = LoggerFactory.getLogger(AvailableCiphersUnitTest.class);
+
+    @Test
+    public void whenGetServices_thenGetAllCipherAlgorithms() {
+        for (Provider provider : Security.getProviders()) {
+            for (Provider.Service service : provider.getServices()) {
+                logger.info(service.getAlgorithm());
+            }
+        }
+    }
+
+    @Test
+    public void whenGetServicesWithFilter_thenGetAllCompatibleCipherAlgorithms() {
+        List<String> algorithms = Arrays.stream(Security.getProviders())
+          .flatMap(provider -> provider.getServices().stream())
+          .filter(service -> "Cipher".equals(service.getType()))
+          .map(Provider.Service::getAlgorithm)
+          .collect(Collectors.toList());
+
+        algorithms.forEach(logger::info);
+    }
+}

core-java-modules/core-java-security-2/src/test/java/com/baeldung/trustedcert/CertificatesUnitTest.java

@@ -0,0 +1,94 @@
+package com.baeldung.trustedcert;
+
+import org.junit.jupiter.api.Test;
+
+import javax.net.ssl.TrustManager;
+import javax.net.ssl.TrustManagerFactory;
+import javax.net.ssl.X509TrustManager;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.security.KeyStore;
+import java.security.KeyStoreException;
+import java.security.NoSuchAlgorithmException;
+import java.security.cert.Certificate;
+import java.security.cert.CertificateException;
+import java.security.cert.PKIXParameters;
+import java.security.cert.TrustAnchor;
+import java.security.cert.X509Certificate;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+public class CertificatesUnitTest {
+
+    private static final String GODADDY_CA_ALIAS = "godaddyrootg2ca [jdk]";
+
+    @Test
+    public void whenLoadingCacertsKeyStore_thenCertificatesArePresent() throws Exception {
+        KeyStore keyStore = loadKeyStore();
+        PKIXParameters params = new PKIXParameters(keyStore);
+
+        Set<TrustAnchor> trustAnchors = params.getTrustAnchors();
+        List<Certificate> certificates = trustAnchors.stream()
+          .map(TrustAnchor::getTrustedCert)
+          .collect(Collectors.toList());
+
+        assertFalse(certificates.isEmpty());
+    }
+
+    @Test
+    public void whenLoadingDefaultKeyStore_thenCertificatesArePresent() throws Exception {
+        TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
+        trustManagerFactory.init((KeyStore)null);
+
+        List<TrustManager> trustManagers = Arrays.asList(trustManagerFactory.getTrustManagers());
+        List<X509Certificate> certificates = trustManagers.stream()
+          .filter(X509TrustManager.class::isInstance)
+          .map(X509TrustManager.class::cast)
+          .map(trustManager -> Arrays.asList(trustManager.getAcceptedIssuers()))
+          .flatMap(Collection::stream)
+          .collect(Collectors.toList());
+
+        assertFalse(certificates.isEmpty());
+    }
+
+    @Test
+    public void whenLoadingKeyStore_thenGoDaddyCALabelIsPresent() throws Exception {
+        KeyStore keyStore = loadKeyStore();
+
+        Enumeration<String> aliasEnumeration = keyStore.aliases();
+        List<String> aliases = Collections.list(aliasEnumeration);
+
+        assertTrue(aliases.contains(GODADDY_CA_ALIAS));
+    }
+
+    @Test
+    public void whenLoadingKeyStore_thenGoDaddyCertificateIsPresent() throws Exception {
+        KeyStore keyStore = loadKeyStore();
+
+        Certificate goDaddyCertificate = keyStore.getCertificate(GODADDY_CA_ALIAS);
+
+        assertNotNull(goDaddyCertificate);
+    }
+
+    private KeyStore loadKeyStore() throws CertificateException, NoSuchAlgorithmException, IOException, KeyStoreException {
+        String relativeCacertsPath = "/lib/security/cacerts".replace("/", File.separator);
+        String filename = System.getProperty("java.home") + relativeCacertsPath;
+        FileInputStream is = new FileInputStream(filename);
+
+        KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
+        String password = "changeit";
+        keystore.load(is, password.toCharArray());
+
+        return keystore;
+    }
+}

core-java-modules/multimodulemavenproject/daomodule/pom.xml

@@ -20,6 +20,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/multimodulemavenproject/entitymodule/pom.xml

@@ -20,6 +20,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/multimodulemavenproject/mainappmodule/pom.xml

@@ -38,6 +38,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/multimodulemavenproject/userdaomodule/pom.xml

@@ -33,6 +33,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/pom.xml

@@ -18,20 +18,9 @@
 
     <modules>
         <module>core-java</module>
-        <!-- <module>core-java-10</module> --> <!-- We haven't upgraded to java 10. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-11</module> --> <!-- We haven't upgraded to java 11. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-12</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-13</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-14</module> --> <!-- We haven't upgraded to java 14.-->
         <module>core-java-8</module>
         <module>core-java-8-2</module>
 
-        <!-- <module>core-java-9</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-improvements</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-jigsaw</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-new-features</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-streams</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-
         <module>core-java-annotations</module>
 
         <module>core-java-arrays-sorting</module>
@@ -51,7 +40,6 @@
         <module>core-java-collections-maps</module>
         <module>core-java-collections-maps-2</module>
         <module>core-java-collections-maps-3</module>
-        <!-- <module>core-java-collections-set</module> --> <!-- We haven't upgraded to java 11. Fixing in BAEL-10841 -->
 
         <module>core-java-concurrency-2</module>
         <module>core-java-concurrency-advanced</module>
@@ -65,10 +53,7 @@
 
         <!--<module>core-java-8-datetime</module>--> <!-- unit test case failure -->
         <module>core-java-8-datetime-2</module>
-        <!-- <module>core-java-date-operations-1</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
         <module>core-java-date-operations-2</module>
-        <!-- We haven't upgraded to java 9. -->
-        <!-- <module>core-java-datetime-computations</module> <module>core-java-datetime-conversion</module> <module>core-java-datetime-java8</module> <module>core-java-datetime-string</module> -->
         <module>core-java-8-datetime</module>
 
         <module>core-java-exceptions</module>
@@ -85,7 +70,6 @@
 
         <module>core-java-jar</module>
         <module>core-java-jndi</module>
-        <!-- <module>core-java-jpms</module> --> <!-- We haven't upgraded to java 10. Fixing in BAEL-10841 -->
         <module>core-java-jvm</module>
         <module>core-java-jvm-2</module>
 
@@ -113,7 +97,6 @@
         <module>core-java-nio-2</module>
 
         <module>core-java-optional</module>
-        <!--<module>core-java-os</module> --> <!-- We haven't upgraded to java 9. -->
 
         <module>core-java-perf</module>
 
@@ -138,9 +121,6 @@
         <module>core-java-sun</module>
 
         <module>core-java-regex</module>
-        <!-- <module>core-java-time-measurements</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-
-        <!-- <module>multimodulemavenproject</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
         <module>pre-jpms</module>
     </modules>
 

core-kotlin-modules/core-kotlin-collections-2/README.md

@@ -2,6 +2,6 @@
 
 This module contains articles about core Kotlin collections.
 
-### Relevant articles:
-
+## Relevant articles:
 
+- [Aggregate Operations in Kotlin](https://www.baeldung.com/kotlin/aggregate-operations)

core-kotlin-modules/core-kotlin-lang/src/main/kotlin/com/baeldung/inline/Inline.kt

@@ -22,30 +22,6 @@ fun main() {
     numbers.each { println(random * it) } // capturing the random variable
 }
 
-fun namedFunction(): Int {
-    return 42
-}
-
-fun anonymous(): () -> Int {
-    return fun(): Int {
-        return 42
-    }
-}
-
-inline fun <T> List<T>.eachIndexed(f: (Int, T) -> Unit) {
-    for (i in indices) {
-        f(i, this[i])
-    }
-}
-
-fun <T> List<T>.indexOf(x: T): Int {
-    eachIndexed { index, value ->
-        if (value == x) return index
-    }
-
-    return -1
-}
-
 /**
  * Generates a random number.
  */

core-kotlin-modules/core-kotlin/README.md

@@ -12,3 +12,4 @@ This module contains articles about Kotlin core features.
 - [Sequences in Kotlin](https://www.baeldung.com/kotlin/sequences)
 - [Converting Kotlin Data Class from JSON using GSON](https://www.baeldung.com/kotlin-json-convert-data-class)
 - [Exception Handling in Kotlin](https://www.baeldung.com/kotlin/exception-handling)
+- [Quick Guide to Kotlin Default and Named Arguments](https://www.baeldung.com/kotlin/default-named-arguments)

core-kotlin-modules/core-kotlin/src/main/kotlin/com/baeldung/arguments/DefaultArguments.kt

@@ -0,0 +1,37 @@
+package com.baeldung.arguments
+
+fun main() {
+
+    // Skip both the connectTimeout and enableRetry arguments
+    connect("http://www.baeldung.com")
+
+    // Skip only the enableRetry argument:
+    connect("http://www.baeldung.com", 5000)
+
+    // Skip only the middle argument connectTimeout
+    // connect("http://www.baeldung.com", false) // This results in a compiler error
+
+    // Because we skipped the connectTimeout argument, we must pass the enableRetry as a named argument
+    connect("http://www.baeldung.com", enableRetry = false)
+
+    // Overriding Functions and Default Arguments
+    val realConnector = RealConnector()
+    realConnector.connect("www.baeldung.com")
+    realConnector.connect()
+}
+
+fun connect(url: String, connectTimeout: Int = 1000, enableRetry: Boolean = true) {
+    println("The parameters are url = $url, connectTimeout = $connectTimeout, enableRetry = $enableRetry")
+}
+
+open class AbstractConnector {
+    open fun connect(url: String = "localhost") {
+        // function implementation
+    }
+}
+
+class RealConnector : AbstractConnector() {
+    override fun connect(url: String) {
+        println("The parameter is url = $url")
+    }
+}

core-kotlin-modules/core-kotlin/src/main/kotlin/com/baeldung/arguments/NamedArguments.kt

@@ -0,0 +1,28 @@
+package com.baeldung.arguments
+
+fun main() {
+    resizePane(newSize = 10, forceResize = true, noAnimation = false)
+
+    // Swap the order of last two named arguments
+    resizePane(newSize = 11, noAnimation = false, forceResize = true)
+
+    // Named arguments can be passed in any order
+    resizePane(forceResize = true, newSize = 12, noAnimation = false)
+
+    // Mixing Named and Positional Arguments
+    // Kotlin 1.3 would allow us to name only the arguments after the positional ones
+    resizePane(20, true, noAnimation = false)
+
+    // Using a positional argument in the middle of named arguments (supported from Kotlin 1.4.0)
+    // resizePane(newSize = 20, true, noAnimation = false)
+
+    // Only the last argument as a positional argument (supported from Kotlin 1.4.0)
+    // resizePane(newSize = 30, forceResize = true, false)
+
+    // Use a named argument in the middle of positional arguments (supported from Kotlin 1.4.0)
+    // resizePane(40, forceResize = true, false)
+}
+
+fun resizePane(newSize: Int, forceResize: Boolean, noAnimation: Boolean) {
+    println("The parameters are newSize = $newSize, forceResize = $forceResize, noAnimation = $noAnimation")
+}

ddd/pom.xml

@@ -104,16 +104,12 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
-                <version>${maven-surefire-plugin.version}</version>
             </plugin>
         </plugins>
     </build>
 
     <properties>
-        <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
-
         <joda-money.version>1.0.1</joda-money.version>
 
-        <junit-jupiter.version>5.6.2</junit-jupiter.version>
     </properties>
 </project>

docker/README.md

@@ -1,4 +1,3 @@
 ## Relevant Articles:
 
 - [Introduction to Docker Compose](https://www.baeldung.com/docker-compose)
-- [Creating Docker Images with Spring Boot](https://www.baeldung.com/spring-boot-docker-images)

docker/docker-spring-boot/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Creating Docker Images with Spring Boot](https://www.baeldung.com/spring-boot-docker-images)

feign/pom.xml

@@ -16,11 +16,6 @@
     </parent>
 
     <dependencies>
-        <dependency>
-            <groupId>io.github.openfeign</groupId>
-            <artifactId>feign-core</artifactId>
-            <version>${feign.version}</version>
-        </dependency>
         <dependency>
             <groupId>io.github.openfeign</groupId>
             <artifactId>feign-okhttp</artifactId>
@@ -44,21 +39,8 @@
         </dependency>
     </dependencies>
 
-    <build>
-        <pluginManagement>
-            <plugins>
-                <plugin>
-                    <groupId>org.springframework.boot</groupId>
-                    <artifactId>spring-boot-maven-plugin</artifactId>
-                    <version>${spring-boot-maven-plugin.version}</version>
-                </plugin>
-            </plugins>
-        </pluginManagement>
-    </build>
-
     <properties>
-        <feign.version>9.4.0</feign.version>
-        <spring-boot-maven-plugin.version>1.4.2.RELEASE</spring-boot-maven-plugin.version>
+        <feign.version>10.11</feign.version>
     </properties>
 
 </project>

feign/src/test/java/com/baeldung/feign/clients/BookClientLiveTest.java

@@ -6,8 +6,6 @@ import com.baeldung.feign.models.BookResource;
 import lombok.extern.slf4j.Slf4j;
 import org.junit.Before;
 import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
 
 import java.util.List;
 import java.util.UUID;
@@ -22,7 +20,6 @@ import static org.junit.Assert.assertTrue;
  * Consumes https://github.com/Baeldung/spring-hypermedia-api
  */
 @Slf4j
-@RunWith(JUnit4.class)
 public class BookClientLiveTest {
     private BookClient bookClient;
 

gradle-5/cmd-line-args/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles:
+
+- [Passing Command Line Arguments in Gradle](https://www.baeldung.com/gradle-command-line-arguments)

gradle-5/source-sets/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Gradle Source Sets](https://www.baeldung.com/gradle-source-sets)