Merge pull request #16 from eugenp/master

update

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/GreedyAlgorithm.java

@@ -15,7 +15,7 @@ public class GreedyAlgorithm {
         this.fp = new FollowersPath();
     }
     
-    public long findMostFollowersPath(String account) throws Exception {        
+    public long findMostFollowersPath(String account) {
         long max = 0;
         SocialUser toFollow = null;
         
@@ -31,12 +31,8 @@ public class GreedyAlgorithm {
         if (currentLevel < maxLevel - 1) {
             currentLevel++;
             max += findMostFollowersPath(toFollow.getUsername());
-            //fp.addFollower(toFollow.getUsername(), max);
-            //fp.addCount(max);
             return max;
         } else {
-            //fp.addFollower(toFollow.getUsername(), max);
-            //fp.addCount(max);
             return max;
         }            
     }

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/NonGreedyAlgorithm.java

@@ -13,9 +13,8 @@ public class NonGreedyAlgorithm {
         this.tc = tc;
         this.currentLevel = level;
     }
-    
-    
-    public long findMostFollowersPath(String account) throws Exception {        
+      
+    public long findMostFollowersPath(String account) {
         List<SocialUser> followers = tc.getFollowers(account);
         long total = currentLevel > 0 ? followers.size() : 0;
 

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/SocialConnector.java

@@ -20,9 +20,9 @@ public class SocialConnector {
         return this.isCounterEnabled;
     }
     
-    public List<SocialUser> getFollowers(String account) throws Exception {
+    public List<SocialUser> getFollowers(String account) {
         if (counter < 0)
-            throw new Exception ("API limit reached");
+            throw new IllegalStateException ("API limit reached");
         else {
             if(this.isCounterEnabled) counter--;
             for(SocialUser user : users) {

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/greedy/GreedyAlgorithmUnitTest.java

@@ -35,21 +35,21 @@ public class GreedyAlgorithmUnitTest {
     }
 
     @Test
-    public void greedyAlgorithmTest() throws Exception {
+    public void greedyAlgorithmTest() {
         GreedyAlgorithm ga = new GreedyAlgorithm(prepareNetwork());
         assertEquals(ga.findMostFollowersPath("root"), 5);
     }
 
     @Test
-    public void nongreedyAlgorithmTest() throws Exception {
+    public void nongreedyAlgorithmTest() {
         NonGreedyAlgorithm nga = new NonGreedyAlgorithm(prepareNetwork(), 0);
-        Assertions.assertThrows(Exception.class, () -> {
+        Assertions.assertThrows(IllegalStateException.class, () -> {
             nga.findMostFollowersPath("root");
           });
     }
 
     @Test
-    public void nongreedyAlgorithmUnboundedTest() throws Exception {
+    public void nongreedyAlgorithmUnboundedTest() {
         SocialConnector sc = prepareNetwork();
         sc.switchCounter();
         NonGreedyAlgorithm nga = new NonGreedyAlgorithm(sc, 0);

apache-poi/pom.xml

@@ -32,7 +32,7 @@
     </dependencies>
 
     <properties>
-        <poi.version>3.15</poi.version>
+        <poi.version>4.1.1</poi.version>
         <jexcel.version>1.0.6</jexcel.version>
     </properties>
 

apache-poi/src/main/java/com/baeldung/poi/excel/read/cellvalueandnotformula/CellValueAndNotFormulaHelper.java

@@ -0,0 +1,83 @@
+package com.baeldung.poi.excel.read.cellvalueandnotformula;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+
+import org.apache.poi.ss.usermodel.Cell;
+import org.apache.poi.ss.usermodel.CellType;
+import org.apache.poi.ss.usermodel.FormulaEvaluator;
+import org.apache.poi.ss.usermodel.Row;
+import org.apache.poi.ss.usermodel.Sheet;
+import org.apache.poi.ss.usermodel.Workbook;
+import org.apache.poi.ss.util.CellAddress;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+
+public class CellValueAndNotFormulaHelper {
+
+    public Object getCellValueByFetchingLastCachedValue(String fileLocation, String cellLocation) throws IOException {
+        Object cellValue = new Object();
+
+        FileInputStream inputStream = new FileInputStream(new File(fileLocation));
+        Workbook workbook = new XSSFWorkbook(inputStream);
+
+        Sheet sheet = workbook.getSheetAt(0);
+
+        CellAddress cellAddress = new CellAddress(cellLocation);
+        Row row = sheet.getRow(cellAddress.getRow());
+        Cell cell = row.getCell(cellAddress.getColumn());
+
+        if (cell.getCellType() == CellType.FORMULA) {
+            switch (cell.getCachedFormulaResultType()) {
+                case BOOLEAN:
+                    cellValue = cell.getBooleanCellValue();
+                    break;
+                case NUMERIC:
+                    cellValue = cell.getNumericCellValue();
+                    break;
+                case STRING:
+                    cellValue = cell.getStringCellValue();
+                    break;
+                default:
+                    cellValue = null;
+            }
+        }
+
+        workbook.close();
+        return cellValue;
+    }
+
+    public Object getCellValueByEvaluatingFormula(String fileLocation, String cellLocation) throws IOException {
+        Object cellValue = new Object();
+
+        FileInputStream inputStream = new FileInputStream(new File(fileLocation));
+        Workbook workbook = new XSSFWorkbook(inputStream);
+
+        Sheet sheet = workbook.getSheetAt(0);
+        FormulaEvaluator evaluator = workbook.getCreationHelper()
+            .createFormulaEvaluator();
+
+        CellAddress cellAddress = new CellAddress(cellLocation);
+        Row row = sheet.getRow(cellAddress.getRow());
+        Cell cell = row.getCell(cellAddress.getColumn());
+
+        if (cell.getCellType() == CellType.FORMULA) {
+            switch (evaluator.evaluateFormulaCell(cell)) {
+                case BOOLEAN:
+                    cellValue = cell.getBooleanCellValue();
+                    break;
+                case NUMERIC:
+                    cellValue = cell.getNumericCellValue();
+                    break;
+                case STRING:
+                    cellValue = cell.getStringCellValue();
+                    break;
+                default:
+                    cellValue = null;
+            }
+        }
+
+        workbook.close();
+        return cellValue;
+    }
+}

apache-poi/src/test/java/com/baeldung/poi/excel/read/cellvalueandnotformula/CellValueAndNotFormulaUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.poi.excel.read.cellvalueandnotformula;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Paths;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class CellValueAndNotFormulaUnitTest {
+
+    private CellValueAndNotFormulaHelper readCellValueAndNotFormulaHelper;
+    private String fileLocation;
+    private static final String FILE_NAME = "test.xlsx";
+
+    @Before
+    public void setup() throws URISyntaxException {
+        fileLocation = Paths.get(ClassLoader.getSystemResource(FILE_NAME).toURI()).toString();
+        readCellValueAndNotFormulaHelper = new CellValueAndNotFormulaHelper();
+    }
+
+    @Test
+    public void givenExcelCell_whenReadCellValueByLastCachedValue_thenProduceCorrectResult() throws IOException {
+        final double expectedResult = 7.0;
+        final Object cellValue = readCellValueAndNotFormulaHelper.getCellValueByFetchingLastCachedValue(fileLocation, "C2");
+
+        assertEquals(expectedResult, cellValue);
+    }
+
+    @Test
+    public void givenExcelCell_whenReadCellValueByEvaluatingFormula_thenProduceCorrectResult() throws IOException {
+        final double expectedResult = 7.0;
+        final Object cellValue = readCellValueAndNotFormulaHelper.getCellValueByEvaluatingFormula(fileLocation, "C2");
+
+        assertEquals(expectedResult, cellValue);
+    }
+}

apache-rocketmq/README.md

@@ -0,0 +1,5 @@
+## Apache RocketMQ
+
+This module contains articles about Apache RocketMQ
+
+### Relevant Articles: 

apache-rocketmq/pom.xml

@@ -0,0 +1,27 @@
+<?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>apache-rocketmq</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <name>apache-rocketmq</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.rocketmq</groupId>
+            <artifactId>rocketmq-spring-boot-starter</artifactId>
+            <version>2.0.4</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <geode.core>1.6.0</geode.core>
+    </properties>
+</project>

apache-rocketmq/src/main/java/com/baeldung/rocketmq/consumer/CartEventConsumer.java

@@ -0,0 +1,34 @@
+package com.baeldung.rocketmq.consumer;
+
+import com.baeldung.rocketmq.event.CartItemEvent;
+import org.apache.rocketmq.spring.annotation.RocketMQMessageListener;
+import org.apache.rocketmq.spring.core.RocketMQListener;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.stereotype.Service;
+
+@SpringBootApplication
+public class CartEventConsumer {
+
+    public static void main(String[] args) {
+        SpringApplication.run(CartEventConsumer.class, args);
+    }
+
+    @Service
+    @RocketMQMessageListener(topic = "cart-item-add-topic", consumerGroup = "cart-consumer_cart-item-add-topic")
+    public class CardItemAddConsumer implements RocketMQListener<CartItemEvent> {
+        public void onMessage(CartItemEvent addItemEvent) {
+            System.out.println("Adding item: " + addItemEvent);
+            // logic
+        }
+    }
+
+    @Service
+    @RocketMQMessageListener(topic = "cart-item-removed-topic", consumerGroup = "cart-consumer_cart-item-removed-topic")
+    public class CardItemRemoveConsumer implements RocketMQListener<CartItemEvent> {
+        public void onMessage(CartItemEvent removeItemEvent) {
+            System.out.println("Removing item: " + removeItemEvent);
+            // logic
+        }
+    }
+}

apache-rocketmq/src/main/java/com/baeldung/rocketmq/event/CartItemEvent.java

@@ -0,0 +1,32 @@
+package com.baeldung.rocketmq.event;
+
+public class CartItemEvent {
+    private String itemId;
+    private int quantity;
+
+    public CartItemEvent(String itemId, int quantity) {
+        this.itemId = itemId;
+        this.quantity = quantity;
+    }
+
+    public String getItemId() {
+        return itemId;
+    }
+
+    public void setItemId(String itemId) {
+        this.itemId = itemId;
+    }
+
+    public int getQuantity() {
+        return quantity;
+    }
+
+    public void setQuantity(int quantity) {
+        this.quantity = quantity;
+    }
+
+    @Override
+    public String toString() {
+        return "CartItemEvent{" + "itemId='" + itemId + '\'' + ", quantity=" + quantity + '}';
+    }
+}

apache-rocketmq/src/main/java/com/baeldung/rocketmq/producer/CartEventProducer.java

@@ -0,0 +1,26 @@
+package com.baeldung.rocketmq.producer;
+
+
+import com.baeldung.rocketmq.event.CartItemEvent;
+import org.apache.rocketmq.spring.core.RocketMQTemplate;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class CartEventProducer implements CommandLineRunner {
+
+    @Autowired
+    private RocketMQTemplate rocketMQTemplate;
+
+    public static void main(String[] args) {
+        SpringApplication.run(CartEventProducer.class, args);
+    }
+
+    public void run(String... args) throws Exception {
+        rocketMQTemplate.convertAndSend("cart-item-add-topic", new CartItemEvent("bike", 1));
+        rocketMQTemplate.convertAndSend("cart-item-add-topic", new CartItemEvent("computer", 2));
+        rocketMQTemplate.convertAndSend("cart-item-removed-topic", new CartItemEvent("bike", 1));
+    }
+}

apache-rocketmq/src/main/java/com/baeldung/rocketmq/transaction/TransactionListenerImpl.java

@@ -0,0 +1,21 @@
+package com.baeldung.rocketmq.transaction;
+
+import org.apache.rocketmq.spring.annotation.RocketMQTransactionListener;
+import org.apache.rocketmq.spring.core.RocketMQLocalTransactionListener;
+import org.apache.rocketmq.spring.core.RocketMQLocalTransactionState;
+import org.springframework.messaging.Message;
+
+@RocketMQTransactionListener(txProducerGroup = "test-transaction")
+class TransactionListenerImpl implements RocketMQLocalTransactionListener {
+    @Override
+    public RocketMQLocalTransactionState executeLocalTransaction(Message msg, Object arg) {
+        // ... local transaction process, return ROLLBACK, COMMIT or UNKNOWN
+        return RocketMQLocalTransactionState.UNKNOWN;
+    }
+
+    @Override
+    public RocketMQLocalTransactionState checkLocalTransaction(Message msg) {
+        // ... check transaction status and return ROLLBACK, COMMIT or UNKNOWN
+        return RocketMQLocalTransactionState.COMMIT;
+    }
+}

apache-rocketmq/src/main/resources/application.properties

@@ -0,0 +1,9 @@
+rocketmq.name-server=127.0.0.1:9876
+rocketmq.producer.group=my-group
+rocketmq.producer.send-message-timeout=300000
+rocketmq.producer.compress-message-body-threshold=4096
+rocketmq.producer.max-message-size=4194304
+rocketmq.producer.retry-times-when-send-async-failed=0
+rocketmq.producer.retry-next-server=true
+rocketmq.producer.retry-times-when-send-failed=2
+

core-groovy-2/src/main/groovy/com/baeldung/metaprogramming/extension/BasicExtensions.groovy

@@ -2,10 +2,13 @@ package com.baeldung.metaprogramming.extension
 
 import com.baeldung.metaprogramming.Employee
 
+import java.time.LocalDate
+import java.time.Year
+
 class BasicExtensions {
     
     static int getYearOfBirth(Employee self) {
-        return (new Date().getYear() + 1900) - self.age;
+        return Year.now().value - self.age
     }
     
     static String capitalize(String self) {

core-groovy-2/src/test/groovy/com/baeldung/metaprogramming/MetaprogrammingUnitTest.groovy

@@ -1,6 +1,9 @@
 package com.baeldung.metaprogramming
 
-import groovy.time.TimeCategory
+
+import java.time.LocalDate
+import java.time.Period
+import java.time.Year
 
 class MetaprogrammingUnitTest extends GroovyTestCase {
 
@@ -51,14 +54,16 @@ class MetaprogrammingUnitTest extends GroovyTestCase {
 
     void testJavaMetaClass() {
         String.metaClass.capitalize = { String str ->
-            str.substring(0, 1).toUpperCase() + str.substring(1);
+            str.substring(0, 1).toUpperCase() + str.substring(1)
         }
         assert "norman".capitalize() == "Norman"
     }
 
     void testEmployeeExtension() {
-        Employee emp = new Employee(age: 28)
-        assert emp.getYearOfBirth() == 1992
+        def age = 28
+        def expectedYearOfBirth = Year.now() - age
+        Employee emp = new Employee(age: age)
+        assert emp.getYearOfBirth() == expectedYearOfBirth.value
     }
 
     void testJavaClassesExtensions() {

core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/duplicatescounter/DuplicatesCounter.java

@@ -24,11 +24,21 @@ public class DuplicatesCounter {
         return resultMap;
     }
 
-    public static <T> Map<T, Long> countByClassicalLoopWithMapCompute(List<T> inputList) {
+    public static <T> Map<T, Long> countByForEachLoopWithGetOrDefault(List<T> inputList) {
         Map<T, Long> resultMap = new HashMap<>();
-        for (T element : inputList) {
-            resultMap.compute(element, (k, v) -> v == null ? 1 : v + 1);
-        }
+        inputList.forEach(e -> resultMap.put(e, resultMap.getOrDefault(e, 0L) + 1L));
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByForEachLoopWithMapCompute(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        inputList.forEach(e -> resultMap.compute(e, (k, v) -> v == null ? 1L : v + 1L));
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByForEachLoopWithMapMerge(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        inputList.forEach(e -> resultMap.merge(e, 1L, Long::sum));
         return resultMap;
     }
 

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/duplicatescounter/DuplicatesCounterUnitTest.java

@@ -11,7 +11,6 @@ import static org.assertj.core.data.MapEntry.entry;
 
 class DuplicatesCounterUnitTest {
 
-
     private static List<String> INPUT_LIST = Lists.list(
         "expect1",
         "expect2", "expect2",
@@ -24,10 +23,21 @@ class DuplicatesCounterUnitTest {
         verifyResult(result);
     }
 
+    @Test
+    void givenInput_whenCountByForEachLoopWithGetOrDefault_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByForEachLoopWithGetOrDefault(INPUT_LIST);
+        verifyResult(result);
+    }
 
     @Test
-    void givenInput_whenCountByClassicalLoopWithMapCompute_thenGetResultMap() {
-        Map<String, Long> result = DuplicatesCounter.countByClassicalLoopWithMapCompute(INPUT_LIST);
+    void givenInput_whenCountByForEachLoopWithMapCompute_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByForEachLoopWithMapCompute(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    @Test
+    void givenInput_whenCountByForEachLoopWithMapMerge_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByForEachLoopWithMapMerge(INPUT_LIST);
         verifyResult(result);
     }
 

core-java-modules/core-java-date-operations-1/README.md

@@ -1,6 +1,5 @@
-## Java Date/time computations Cookbooks and Examples
-
-This module contains articles about date and time computations in Java.
+## Core Date Operations (Part 1)
+This module contains articles about date operations in Java.
 
 ### Relevant Articles: 
 - [Difference Between Two Dates in Java](http://www.baeldung.com/java-date-difference)
@@ -13,3 +12,4 @@ This module contains articles about date and time computations in Java.
 - [Increment Date in Java](http://www.baeldung.com/java-increment-date)
 - [Add Hours To a Date In Java](http://www.baeldung.com/java-add-hours-date)
 - [Introduction to Joda-Time](http://www.baeldung.com/joda-time)
+- [[Next -->]](/core-java-modules/core-java-date-operations-2)

core-java-modules/core-java-date-operations-1/pom.xml

@@ -2,9 +2,9 @@
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <artifactId>core-java-datetime-computations</artifactId>
+    <artifactId>core-java-date-operations-1</artifactId>
     <version>${project.parent.version}</version>
-    <name>core-java-datetime-computations</name>
+    <name>core-java-date-operations-1</name>
     <packaging>jar</packaging>
 
     <parent>
@@ -41,7 +41,7 @@
     </dependencies>
 
     <build>
-        <finalName>core-java-datetime-computations</finalName>
+        <finalName>core-java-date-operations-1</finalName>
         <resources>
             <resource>
                 <directory>src/main/resources</directory>

core-java-modules/core-java-date-operations-2/README.md

@@ -1,4 +1,4 @@
-## Core Date Operations
+## Core Date Operations (Part 2)
 This module contains articles about date operations in Java.
 
 ### Relevant Articles:
@@ -6,3 +6,4 @@ This module contains articles about date operations in Java.
 - [Skipping Weekends While Adding Days to LocalDate in Java 8](https://www.baeldung.com/java-localdate-add-days-skip-weekends)
 - [Checking If Two Java Dates Are on the Same Day](https://www.baeldung.com/java-check-two-dates-on-same-day)
 - [Converting Java Date to OffsetDateTime](https://www.baeldung.com/java-convert-date-to-offsetdatetime)
+- [[<-- Prev]](/core-java-modules/core-java-date-operations-1)

core-java-modules/core-java-date-operations-2/pom.xml

@@ -3,9 +3,9 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <artifactId>core-java-date-operations</artifactId>
+    <artifactId>core-java-date-operations-2</artifactId>
     <version>${project.parent.version}</version>
-    <name>core-java-date-operations</name>
+    <name>core-java-date-operations-2</name>
     <packaging>jar</packaging>
 
     <parent>

core-java-modules/core-java-date-operations-2/src/main/java/com/baeldung/date/comparison/DateComparisonUtils.java

@@ -1,65 +1,65 @@
-package com.baeldung.date.comparison;
-
-import java.text.SimpleDateFormat;
-import java.time.Instant;
-import java.time.LocalDate;
-import java.time.ZoneId;
-import java.time.temporal.ChronoUnit;
-import java.util.Calendar;
-import java.util.Date;
-import java.util.TimeZone;
-
-import org.apache.commons.lang3.time.DateUtils;
-
-import hirondelle.date4j.DateTime;
-
-public class DateComparisonUtils {
-
-    public static boolean isSameDayUsingLocalDate(Date date1, Date date2) {
-        LocalDate localDate1 = date1.toInstant()
-            .atZone(ZoneId.systemDefault())
-            .toLocalDate();
-        LocalDate localDate2 = date2.toInstant()
-            .atZone(ZoneId.systemDefault())
-            .toLocalDate();
-        return localDate1.isEqual(localDate2);
-    }
-
-    public static boolean isSameDayUsingInstant(Date date1, Date date2) {
-        Instant instant1 = date1.toInstant()
-            .truncatedTo(ChronoUnit.DAYS);
-        Instant instant2 = date2.toInstant()
-            .truncatedTo(ChronoUnit.DAYS);
-        return instant1.equals(instant2);
-    }
-
-    public static boolean isSameDayUsingSimpleDateFormat(Date date1, Date date2) {
-        SimpleDateFormat fmt = new SimpleDateFormat("yyyyMMdd");
-        return fmt.format(date1)
-            .equals(fmt.format(date2));
-    }
-
-    public static boolean isSameDayUsingCalendar(Date date1, Date date2) {
-        Calendar calendar1 = Calendar.getInstance();
-        calendar1.setTime(date1);
-        Calendar calendar2 = Calendar.getInstance();
-        calendar2.setTime(date2);
-        return calendar1.get(Calendar.YEAR) == calendar2.get(Calendar.YEAR) && calendar1.get(Calendar.MONTH) == calendar2.get(Calendar.MONTH) && calendar1.get(Calendar.DAY_OF_MONTH) == calendar2.get(Calendar.DAY_OF_MONTH);
-    }
-
-    public static boolean isSameDayUsingApacheCommons(Date date1, Date date2) {
-        return DateUtils.isSameDay(date1, date2);
-    }
-
-    public static boolean isSameDayUsingJoda(Date date1, Date date2) {
-        org.joda.time.LocalDate localDate1 = new org.joda.time.LocalDate(date1);
-        org.joda.time.LocalDate localDate2 = new org.joda.time.LocalDate(date2);
-        return localDate1.equals(localDate2);
-    }
-
-    public static boolean isSameDayUsingDate4j(Date date1, Date date2) {
-        DateTime dateObject1 = DateTime.forInstant(date1.getTime(), TimeZone.getDefault());
-        DateTime dateObject2 = DateTime.forInstant(date2.getTime(), TimeZone.getDefault());
-        return dateObject1.isSameDayAs(dateObject2);
-    }
-}
+package com.baeldung.date.comparison;
+
+import java.text.SimpleDateFormat;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.time.temporal.ChronoUnit;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.TimeZone;
+
+import org.apache.commons.lang3.time.DateUtils;
+
+import hirondelle.date4j.DateTime;
+
+public class DateComparisonUtils {
+
+    public static boolean isSameDayUsingLocalDate(Date date1, Date date2) {
+        LocalDate localDate1 = date1.toInstant()
+            .atZone(ZoneId.systemDefault())
+            .toLocalDate();
+        LocalDate localDate2 = date2.toInstant()
+            .atZone(ZoneId.systemDefault())
+            .toLocalDate();
+        return localDate1.isEqual(localDate2);
+    }
+
+    public static boolean isSameDayUsingInstant(Date date1, Date date2) {
+        Instant instant1 = date1.toInstant()
+            .truncatedTo(ChronoUnit.DAYS);
+        Instant instant2 = date2.toInstant()
+            .truncatedTo(ChronoUnit.DAYS);
+        return instant1.equals(instant2);
+    }
+
+    public static boolean isSameDayUsingSimpleDateFormat(Date date1, Date date2) {
+        SimpleDateFormat fmt = new SimpleDateFormat("yyyyMMdd");
+        return fmt.format(date1)
+            .equals(fmt.format(date2));
+    }
+
+    public static boolean isSameDayUsingCalendar(Date date1, Date date2) {
+        Calendar calendar1 = Calendar.getInstance();
+        calendar1.setTime(date1);
+        Calendar calendar2 = Calendar.getInstance();
+        calendar2.setTime(date2);
+        return calendar1.get(Calendar.YEAR) == calendar2.get(Calendar.YEAR) && calendar1.get(Calendar.MONTH) == calendar2.get(Calendar.MONTH) && calendar1.get(Calendar.DAY_OF_MONTH) == calendar2.get(Calendar.DAY_OF_MONTH);
+    }
+
+    public static boolean isSameDayUsingApacheCommons(Date date1, Date date2) {
+        return DateUtils.isSameDay(date1, date2);
+    }
+
+    public static boolean isSameDayUsingJoda(Date date1, Date date2) {
+        org.joda.time.LocalDate localDate1 = new org.joda.time.LocalDate(date1);
+        org.joda.time.LocalDate localDate2 = new org.joda.time.LocalDate(date2);
+        return localDate1.equals(localDate2);
+    }
+
+    public static boolean isSameDayUsingDate4j(Date date1, Date date2) {
+        DateTime dateObject1 = DateTime.forInstant(date1.getTime(), TimeZone.getDefault());
+        DateTime dateObject2 = DateTime.forInstant(date2.getTime(), TimeZone.getDefault());
+        return dateObject1.isSameDayAs(dateObject2);
+    }
+}

core-java-modules/core-java-date-operations-2/src/test/java/com/baeldung/date/comparison/DateComparisonUtilsUnitTest.java

@@ -1,57 +1,57 @@
-package com.baeldung.date.comparison;
-
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-
-import java.time.LocalDateTime;
-import java.time.ZoneId;
-import java.util.Date;
-
-import org.junit.Test;
-
-public class DateComparisonUtilsUnitTest {
-
-    private Date day1Morning = toDate(LocalDateTime.of(2019, 10, 19, 6, 30, 40));
-    private Date day1Evening = toDate(LocalDateTime.of(2019, 10, 19, 18, 30, 50));
-    private Date day2Morning = toDate(LocalDateTime.of(2019, 10, 20, 6, 30, 50));
-
-    private Date toDate(LocalDateTime localDateTime) {
-        return Date.from(localDateTime.atZone(ZoneId.systemDefault())
-            .toInstant());
-    }
-
-    @Test
-    public void givenDatesWithDifferentTime_whenIsSameDay_thenReturnsTrue() {
-        assertTrue(DateComparisonUtils.isSameDayUsingLocalDate(day1Morning, day1Evening));
-        assertTrue(DateComparisonUtils.isSameDayUsingInstant(day1Morning, day1Evening));
-        assertTrue(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Morning, day1Evening));
-        assertTrue(DateComparisonUtils.isSameDayUsingCalendar(day1Morning, day1Evening));
-        assertTrue(DateComparisonUtils.isSameDayUsingApacheCommons(day1Morning, day1Evening));
-        assertTrue(DateComparisonUtils.isSameDayUsingJoda(day1Morning, day1Evening));
-        assertTrue(DateComparisonUtils.isSameDayUsingDate4j(day1Morning, day1Evening));
-    }
-
-    @Test
-    public void givenDates_whenIsDifferentDay_thenReturnsFalse() {
-        assertFalse(DateComparisonUtils.isSameDayUsingLocalDate(day1Morning, day2Morning));
-        assertFalse(DateComparisonUtils.isSameDayUsingLocalDate(day1Evening, day2Morning));
-
-        assertFalse(DateComparisonUtils.isSameDayUsingInstant(day1Morning, day2Morning));
-        assertFalse(DateComparisonUtils.isSameDayUsingInstant(day1Evening, day2Morning));
-
-        assertFalse(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Morning, day2Morning));
-        assertFalse(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Evening, day2Morning));
-
-        assertFalse(DateComparisonUtils.isSameDayUsingCalendar(day1Morning, day2Morning));
-        assertFalse(DateComparisonUtils.isSameDayUsingCalendar(day1Evening, day2Morning));
-
-        assertFalse(DateComparisonUtils.isSameDayUsingApacheCommons(day1Morning, day2Morning));
-        assertFalse(DateComparisonUtils.isSameDayUsingApacheCommons(day1Evening, day2Morning));
-
-        assertFalse(DateComparisonUtils.isSameDayUsingJoda(day1Morning, day2Morning));
-        assertFalse(DateComparisonUtils.isSameDayUsingJoda(day1Evening, day2Morning));
-
-        assertFalse(DateComparisonUtils.isSameDayUsingDate4j(day1Morning, day2Morning));
-        assertFalse(DateComparisonUtils.isSameDayUsingDate4j(day1Evening, day2Morning));
-    }
-}
+package com.baeldung.date.comparison;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.Date;
+
+import org.junit.Test;
+
+public class DateComparisonUtilsUnitTest {
+
+    private Date day1Morning = toDate(LocalDateTime.of(2019, 10, 19, 6, 30, 40));
+    private Date day1Evening = toDate(LocalDateTime.of(2019, 10, 19, 18, 30, 50));
+    private Date day2Morning = toDate(LocalDateTime.of(2019, 10, 20, 6, 30, 50));
+
+    private Date toDate(LocalDateTime localDateTime) {
+        return Date.from(localDateTime.atZone(ZoneId.systemDefault())
+            .toInstant());
+    }
+
+    @Test
+    public void givenDatesWithDifferentTime_whenIsSameDay_thenReturnsTrue() {
+        assertTrue(DateComparisonUtils.isSameDayUsingLocalDate(day1Morning, day1Evening));
+        assertTrue(DateComparisonUtils.isSameDayUsingInstant(day1Morning, day1Evening));
+        assertTrue(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Morning, day1Evening));
+        assertTrue(DateComparisonUtils.isSameDayUsingCalendar(day1Morning, day1Evening));
+        assertTrue(DateComparisonUtils.isSameDayUsingApacheCommons(day1Morning, day1Evening));
+        assertTrue(DateComparisonUtils.isSameDayUsingJoda(day1Morning, day1Evening));
+        assertTrue(DateComparisonUtils.isSameDayUsingDate4j(day1Morning, day1Evening));
+    }
+
+    @Test
+    public void givenDates_whenIsDifferentDay_thenReturnsFalse() {
+        assertFalse(DateComparisonUtils.isSameDayUsingLocalDate(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingLocalDate(day1Evening, day2Morning));
+
+        assertFalse(DateComparisonUtils.isSameDayUsingInstant(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingInstant(day1Evening, day2Morning));
+
+        assertFalse(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Evening, day2Morning));
+
+        assertFalse(DateComparisonUtils.isSameDayUsingCalendar(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingCalendar(day1Evening, day2Morning));
+
+        assertFalse(DateComparisonUtils.isSameDayUsingApacheCommons(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingApacheCommons(day1Evening, day2Morning));
+
+        assertFalse(DateComparisonUtils.isSameDayUsingJoda(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingJoda(day1Evening, day2Morning));
+
+        assertFalse(DateComparisonUtils.isSameDayUsingDate4j(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingDate4j(day1Evening, day2Morning));
+    }
+}

core-java-modules/core-java-lang-math/src/main/java/com/baeldung/powerset/PowerSetUtility.java

@@ -1,7 +1,5 @@
 package com.baeldung.powerset;
 
-import com.google.common.collect.Sets;
-
 import javax.annotation.Nullable;
 import java.util.AbstractSet;
 import java.util.ArrayList;
@@ -163,7 +161,7 @@ public class PowerSetUtility<T> {
         return unMapIndex(powerSetIndices);
     }
 
-    private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithReverseLexicographicalOrder(int n) {
+    private List<List<Boolean>> iterativePowerSetByLoopOverNumbers(int n) {
         List<List<Boolean>> powerSet = new ArrayList<>();
         for (int i = 0; i < (1 << n); i++) {
             List<Boolean> subset = new ArrayList<>(n);
@@ -174,7 +172,7 @@ public class PowerSetUtility<T> {
         return powerSet;
     }
 
-    private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithGrayCodeOrder(int n) {
+    private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithMinimalChange(int n) {
         List<List<Boolean>> powerSet = new ArrayList<>();
         for (int i = 0; i < (1 << n); i++) {
             List<Boolean> subset = new ArrayList<>(n);
@@ -195,32 +193,16 @@ public class PowerSetUtility<T> {
 
     public List<List<T>> iterativePowerSetByLoopOverNumbers(Set<T> set) {
         initializeMap(set);
-                List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithReverseLexicographicalOrder(set.size());
+        List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbers(set.size());
         return unMapListBinary(sets);
     }
 
     public List<List<T>> iterativePowerSetByLoopOverNumbersMinimalChange(Set<T> set) {
         initializeMap(set);
-        List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithGrayCodeOrder(set.size());
+        List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithMinimalChange(set.size());
         return unMapListBinary(sets);
     }
 
-    public static int getRankInLexicographicalOrder(List<Boolean> subset) {
-        int rank = 0;
-        for (int i = 0; i < subset.size(); i++)
-            if (subset.get(i))
-                rank += (1 << (subset.size() - i - 1));
-        return rank;
-    }
-
-    public static List<Boolean> getSubsetForRankInLexicographicalOrder(int rank, int sizeOfSet) {
-        Boolean[] subset = new Boolean[sizeOfSet];
-        for(int j = 0; j < sizeOfSet; j++) {
-            subset[sizeOfSet - j - 1] = ((rank & (1 << j)) > 0);
-        }
-        return Arrays.asList(subset);
-    }
-
     private Set<Set<Integer>> recursivePowerSetIndexRepresentation(int idx, int n) {
         if (idx == n) {
             Set<Set<Integer>> empty = new HashSet<>();

core-java-modules/core-java-lang-math/src/test/java/com/baeldung/powerset/PowerSetUtilityUnitTest.java

@@ -137,7 +137,7 @@ public class PowerSetUtilityUnitTest {
     }
 
     @Test
-    public void givenSet_WhenPowerSetIsCalculatedIterativePowerSetByLoopOverNumbersMinimalChange_ThenItContainsAllSubsetsInGrayOrder() {
+    public void givenSet_WhenPowerSetIsCalculatedIterativePowerSetByLoopOverNumbersWithMinimalChange_ThenItContainsAllSubsets() {
 
         Set<String> set = RandomSetOfStringGenerator.generateRandomSet();
         List<List<String>> powerSet = new PowerSetUtility<String>().iterativePowerSetByLoopOverNumbersMinimalChange(set);
@@ -172,42 +172,6 @@ public class PowerSetUtilityUnitTest {
         }
     }
 
-    @Test
-    public void givenSubset_WhenPowerSetIsInLexicographicalOrder_ReturnCorrectRank() {
-        int n = new Random().nextInt(5) + 5; //a number in [5, 10)
-        for(int i = 0; i < ( 1 << n); i++) {
-            Boolean[] subset = new Boolean[n];
-            for(int j=0; j < n; j++) {
-                subset[n - j - 1] = ((i & (1 << j)) > 0);
-            }
-            Assertions.assertEquals(i, PowerSetUtility.getRankInLexicographicalOrder(Arrays.asList(subset)));
-        }
-    }
-
-    @Test
-    public void givenRanking_WhenPowerSetIsInLexicographicalOrder_ReturnTheSubset() {
-        int n = new Random().nextInt(5) + 5; //a number in [5, 10)
-        List<List<Boolean>> powerSet = new ArrayList<>();
-        for(int i = 0; i < (1 << n); i++) {
-            powerSet.add(PowerSetUtility.getSubsetForRankInLexicographicalOrder(i, n));
-        }
-        //To make sure that the size of power set is (2 power n)
-        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << n)));
-        //To make sure that number of occurrence of each index is (2 power n-1)
-        Map<Integer, Integer> counter = new HashMap<>();
-        for (List<Boolean> subset : powerSet) {
-            for (int i = 0; i < subset.size(); i++) {
-                if(subset.get(i)) {
-                    int num = counter.getOrDefault(i, 0);
-                    counter.put(i, num + 1);
-                }
-            }
-        }
-        counter.forEach((k, v) -> Assertions.assertEquals((1 << (n - 1)), v.intValue()));
-        //To make sure that one subset is not generated twice
-        Assertions.assertEquals(powerSet.size(), new HashSet<>(powerSet).size());
-    }
-
     static class RandomSetOfStringGenerator {
         private static List<String> fruits = Arrays.asList("Apples", "Avocados", "Banana", "Blueberry", "Cherry", "Clementine", "Cucumber", "Date", "Fig",
           "Grapefruit"/*, "Grape", "Kiwi", "Lemon", "Mango", "Mulberry", "Melon", "Nectarine", "Olive", "Orange"*/);

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

@@ -1,3 +0,0 @@
-### Relevant Articles:
-
-- [Intro to the Java SecurityManager](https://www.baeldung.com/java-security-manager)

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

@@ -1,16 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
-    <artifactId>core-java-security-manager</artifactId>
-    <version>0.1.0-SNAPSHOT</version>
-    <name>core-java-security-manager</name>
-    <packaging>jar</packaging>
-
-    <parent>
-        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>core-java-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-    </parent>
-
-</project>

core-java-modules/core-java-security-manager/src/test/java/com/baeldung/security/manager/SecurityManagerUnitTest.java

@@ -1,35 +0,0 @@
-package com.baeldung.security.manager;
-
-import org.junit.Test;
-
-import java.net.URL;
-import java.security.AccessControlException;
-import java.util.concurrent.Callable;
-
-public class SecurityManagerUnitTest {
-
-    @Test(expected = AccessControlException.class)
-    public void whenSecurityManagerIsActive_thenNetworkIsNotAccessibleByDefault() throws Exception {
-        doTest(() -> {
-            new URL("http://www.google.com").openConnection().connect();
-            return null;
-        });
-    }
-
-    @Test(expected = AccessControlException.class)
-    public void whenUnauthorizedClassTriesToAccessProtectedOperation_thenAnExceptionIsThrown() throws Exception {
-        doTest(() -> {
-            new Service().operation();
-            return null;
-        });
-    }
-
-    private void doTest(Callable<Void> action) throws Exception {
-        System.setSecurityManager(new SecurityManager());
-        try {
-            action.call();
-        } finally {
-            System.setSecurityManager(null);
-        }
-    }
-}

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

@@ -15,4 +15,5 @@ This module contains articles about core Java Security
 - [The Java SecureRandom Class](https://www.baeldung.com/java-secure-random)
 - [An Introduction to Java SASL](https://www.baeldung.com/java-sasl)
 - [A Guide to Java GSS API](https://www.baeldung.com/java-gss)
+- [Intro to the Java SecurityManager](https://www.baeldung.com/java-security-manager)
 

core-java-modules/core-java-security/src/main/java/com/baeldung/securitymanager/CustomPermission.java

@@ -1,4 +1,4 @@
-package com.baeldung.security.manager;
+package com.baeldung.securitymanager;
 
 import java.security.BasicPermission;
 

core-java-modules/core-java-security/src/main/java/com/baeldung/securitymanager/Service.java

@@ -1,4 +1,4 @@
-package com.baeldung.security.manager;
+package com.baeldung.securitymanager;
 
 public class Service {
 

core-java-modules/core-java-security/src/test/java/com/baeldung/java/md5/JavaMD5UnitTest.java

@@ -1,4 +1,4 @@
-package org.baeldung.java.md5;
+package com.baeldung.java.md5;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

core-java-modules/core-java-security/src/test/java/com/baeldung/securitymanager/SecurityManagerUnitTest.java

@@ -0,0 +1,35 @@
+package com.baeldung.securitymanager;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.net.URL;
+import java.security.AccessControlException;
+
+public class SecurityManagerUnitTest {
+
+    private static final String TESTING_SECURITY_POLICY = "file:src/test/resources/testing.policy";
+
+    @Before
+    public void setUp() {
+        System.setProperty("java.security.policy", TESTING_SECURITY_POLICY);
+        System.setSecurityManager(new SecurityManager());
+    }
+
+    @After
+    public void tearDown() {
+        System.setSecurityManager(null);
+    }
+
+    @Test(expected = AccessControlException.class)
+    public void whenSecurityManagerIsActive_thenNetworkIsNotAccessibleByDefault() throws IOException {
+        new URL("http://www.google.com").openConnection().connect();
+    }
+
+    @Test(expected = AccessControlException.class)
+    public void whenUnauthorizedClassTriesToAccessProtectedOperation_thenAnExceptionIsThrown() {
+        new Service().operation();
+    }
+}

core-java-modules/core-java-security/src/test/resources/testing.policy

@@ -0,0 +1,5 @@
+grant {
+        // This is for testing purposes only.
+        // It allows us to properly reset the security manager after the unit test completes.
+        permission java.lang.RuntimePermission "setSecurityManager";
+};

core-java-modules/pom.xml

@@ -18,8 +18,7 @@
         <module>core-java-optional</module>
         <module>core-java-lang-operators</module>
         <module>core-java-networking-2</module>
-        <module>core-java-security-manager</module>
-        <module>core-java-date-operations</module>
+        <module>core-java-date-operations-2</module>
     </modules>
 
 </project>

core-kotlin-2/README.md

@@ -5,4 +5,10 @@ This module contains articles about core Kotlin.
 ### Relevant articles:
 
 - [Kotlin Scope Functions](https://www.baeldung.com/kotlin-scope-functions)
+- [Kotlin Annotations](https://www.baeldung.com/kotlin-annotations)
+- [Split a List into Parts in Kotlin](https://www.baeldung.com/kotlin-split-list-into-parts)
+- [String Comparison in Kotlin](https://www.baeldung.com/kotlin-string-comparison)
+- [Guide to JVM Platform Annotations in Kotlin](https://www.baeldung.com/kotlin-jvm-annotations)
+- [Finding an Element in a List Using Kotlin](https://www.baeldung.com/kotlin-finding-element-in-list)
+- [Kotlin Ternary Conditional Operator](https://www.baeldung.com/kotlin-ternary-conditional-operator)
 - More articles: [[<-- prev]](/core-kotlin)

core-kotlin-2/src/test/kotlin/com/baeldung/ternary/TernaryOperatorTest.kt

@@ -0,0 +1,24 @@
+package com.baeldung.ternary
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class TernaryOperatorTest {
+
+    @Test
+    fun `using If`() {
+        val a = true
+        val result = if (a) "yes" else "no"
+        assertEquals("yes", result)
+    }
+
+    @Test
+    fun `using When`() {
+        val a = true
+        val result = when(a) {
+            true -> "yes"
+            false -> "no"
+        }
+        assertEquals("yes", result)
+    }
+}

core-kotlin-modules/core-kotlin-lang-oop-2/README.md

@@ -0,0 +1,10 @@
+## Core Kotlin
+
+This module contains articles about Object-Oriented Programming in Kotlin
+
+### Relevant articles:
+
+- [Generics in Kotlin](https://www.baeldung.com/kotlin-generics)
+- [Delegated Properties in Kotlin](https://www.baeldung.com/kotlin-delegated-properties)
+- [Delegation Pattern in Kotlin](https://www.baeldung.com/kotlin-delegation-pattern)
+- [[<-- Prev]](/core-kotlin-lang-oop)

core-kotlin-modules/core-kotlin-lang-oop-2/pom.xml

@@ -0,0 +1,25 @@
+<?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-kotlin-lang-oop-2</artifactId>
+    <name>core-kotlin-lang-oop-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-kotlin-modules</groupId>
+        <artifactId>core-kotlin-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

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

@@ -0,0 +1,17 @@
+## Core Kotlin Lang OOP
+
+This module contains articles about Object-Oriented Programming in Kotlin
+
+### Relevant articles:
+
+- [Data Classes in Kotlin](https://www.baeldung.com/kotlin-data-classes)
+- [Sealed Classes in Kotlin](https://www.baeldung.com/kotlin-sealed-classes)
+- [Extension Methods in Kotlin](https://www.baeldung.com/kotlin-extension-methods)
+- [Objects in Kotlin](https://www.baeldung.com/kotlin-objects)
+- [Working with Enums in Kotlin](https://www.baeldung.com/kotlin-enum)
+- [Kotlin Constructors](https://www.baeldung.com/kotlin-constructors)
+- [Kotlin Nested and Inner Classes](https://www.baeldung.com/kotlin-inner-classes)
+- [Guide to Kotlin Interfaces](https://www.baeldung.com/kotlin-interfaces)
+- [Inline Classes in Kotlin](https://www.baeldung.com/kotlin-inline-classes)
+- [Static Methods Behavior in Kotlin](https://www.baeldung.com/kotlin-static-methods)
+- More articles: [[next -->]](/core-kotlin-lang-oop-2)

core-kotlin-modules/core-kotlin-lang-oop/pom.xml

@@ -0,0 +1,25 @@
+<?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-kotlin-lang-oop</artifactId>
+    <name>core-kotlin-lang-oop</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-kotlin-modules</groupId>
+        <artifactId>core-kotlin-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>