Merge pull request #30 from panos-kakos/master

Update from master

.github/ISSUE_TEMPLATE/issue_report.md

@@ -0,0 +1,32 @@
+---
+name: Issue Report
+about: Report an issue to help us improve
+title: '[ISSUE] '
+---
+
+**Article and Module Links**
+A link to the affected article and the affected module. You can find the link to the module in the Conclusion section in the "on Github" standard phase.
+
+**Describe the Issue**
+A clear and concise description of what the issue is.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Go to '...'
+2. Click on '....'
+3. Scroll down to '....'
+4. See error
+
+**Expected Behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**Environment (please complete the following information):**
+- OS: [e.g. Windows]
+- Browser [e.g. chrome, safari]
+- Version [e.g. 22]
+
+**Additional Context**
+Add any other context about the issue here.

CONTRIBUTING.md

@@ -0,0 +1,11 @@
+# Contributing to Baeldung Tutorials
+First off, thank you for considering contributing to Baeldung Tutorials.
+
+## Reporting Issues
+Before you submit an issue, please review the guidelines below:
+
+1. **No Custom Modifications:** If your issue arises from any custom modifications you've made to the code in the repository, we won't be able to assist. We can only help if the issue is reproducible with the untouched codebase from this repo. If you're working with a modified version, consider asking for help on StackOverflow or other relevant forums.
+2. **Use a clear and descriptive title** for the issue to identify the problem.
+3. **Include a link to the article** you're having issues with.
+4. **Describe the exact steps which reproduce the problem** in as many details as possible.
+5. **Additional Details:** Offer any other context or descriptions that could be useful. Screenshots, error messages, copy/pasteable snippets, or logs can be immensely helpful.

apache-httpclient-2/src/test/java/com/baeldung/httpclient/cookies/HttpClientGettingCookieValueUnitTest.java

@@ -14,6 +14,7 @@ import org.apache.hc.client5.http.impl.classic.HttpClientBuilder;
 import org.apache.hc.client5.http.impl.cookie.BasicClientCookie;
 import org.apache.hc.client5.http.protocol.HttpClientContext;
 
+import org.apache.http.cookie.ClientCookie;
 import org.junit.jupiter.api.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -51,8 +52,8 @@ class HttpClientGettingCookieValueUnitTest {
     private BasicCookieStore createCustomCookieStore() {
         BasicCookieStore cookieStore = new BasicCookieStore();
         BasicClientCookie cookie = new BasicClientCookie("custom_cookie", "test_value");
-        cookie.setDomain("baeldung.com");
-        cookie.setAttribute("domain", "true");
+        cookie.setDomain("github.com");
+        cookie.setAttribute(ClientCookie.DOMAIN_ATTR, "github.com");
         cookie.setPath("/");
         cookieStore.addCookie(cookie);
         return cookieStore;

apache-httpclient-2/src/test/resources/logback.xml

@@ -4,6 +4,7 @@
             <pattern>%date [%level] %logger - %msg %n</pattern>
         </encoder>
     </appender>
+    <logger name="com.baeldung.httpclient.cookies" level="info"/>
 
     <logger name="com.baeldung.httpclient.readresponsebodystring" level="debug"/>
     <logger name="org.apache.http" level="debug"/>

apache-kafka-2/README.md

@@ -13,3 +13,4 @@ You can build the project from the command line using: *mvn clean install*, or i
 - [Read Data From the Beginning Using Kafka Consumer API](https://www.baeldung.com/java-kafka-consumer-api-read)
 - [Get Partition Count for a Topic in Kafka](https://www.baeldung.com/java-kafka-partition-count-topic)
 - [bootstrap-server in Kafka Configuration](https://www.baeldung.com/java-kafka-bootstrap-server)
+- [Introduction to Apache Kafka](https://www.baeldung.com/apache-kafka)

apache-kafka-2/src/test/java/com/baeldung/kafka/multipletopics/MultipleTopicsLiveTest.java

@@ -0,0 +1,103 @@
+package com.baeldung.kafka.multipletopics;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Properties;
+import java.util.concurrent.ExecutionException;
+
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.apache.kafka.clients.consumer.ConsumerRecord;
+import org.apache.kafka.clients.consumer.KafkaConsumer;
+import org.apache.kafka.clients.producer.KafkaProducer;
+import org.apache.kafka.clients.producer.ProducerConfig;
+import org.apache.kafka.clients.producer.ProducerRecord;
+import org.apache.kafka.common.serialization.StringDeserializer;
+import org.apache.kafka.common.serialization.StringSerializer;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.testcontainers.containers.KafkaContainer;
+import org.testcontainers.junit.jupiter.Container;
+import org.testcontainers.junit.jupiter.Testcontainers;
+import org.testcontainers.utility.DockerImageName;
+
+// This live test needs a Docker Daemon running so that a kafka container can be created
+
+@Testcontainers
+public class MultipleTopicsLiveTest {
+
+    private final Logger log = LoggerFactory.getLogger(MultipleTopicsLiveTest.class);
+
+    private static final String CARD_PAYMENTS_TOPIC = "card-payments";
+    private static final String BANK_TRANSFERS_TOPIC = "bank-transfers";
+    private static KafkaProducer<String, String> producer;
+    private static KafkaConsumer<String, String> consumer;
+
+    @Container
+    private static final KafkaContainer KAFKA_CONTAINER = new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:latest"));
+
+    @BeforeAll
+    static void setup() {
+        KAFKA_CONTAINER.addExposedPort(9092);
+        producer = new KafkaProducer<>(getProducerProperties());
+        consumer = new KafkaConsumer<>(getConsumerProperties());
+    }
+
+    @AfterAll
+    static void destroy() {
+        KAFKA_CONTAINER.stop();
+    }
+
+    private static Properties getProducerProperties() {
+        Properties producerProperties = new Properties();
+        producerProperties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, KAFKA_CONTAINER.getBootstrapServers());
+        producerProperties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
+        producerProperties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
+        return producerProperties;
+    }
+
+    private static Properties getConsumerProperties() {
+        Properties consumerProperties = new Properties();
+        consumerProperties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, KAFKA_CONTAINER.getBootstrapServers());
+        consumerProperties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        consumerProperties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
+        consumerProperties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
+        consumerProperties.put(ConsumerConfig.GROUP_ID_CONFIG, "payments");
+        return consumerProperties;
+    }
+
+    @Test
+    void whenSendingMessagesOnTwoTopics_thenConsumerReceivesMessages() throws Exception {
+        publishMessages();
+
+        consumer.subscribe(Arrays.asList(CARD_PAYMENTS_TOPIC, BANK_TRANSFERS_TOPIC));
+
+        int eventsProcessed = 0;
+        for (ConsumerRecord<String, String> record : consumer.poll(Duration.ofSeconds(10))) {
+            log.info("Event on topic={}, payload={}", record.topic(), record.value());
+            eventsProcessed++;
+        }
+
+        assertThat(eventsProcessed).isEqualTo(2);
+    }
+
+    private void publishMessages() throws ExecutionException, InterruptedException {
+        ProducerRecord<String, String> cardPayment = new ProducerRecord<>(CARD_PAYMENTS_TOPIC, createCardPayment());
+        producer.send(cardPayment).get();
+
+        ProducerRecord<String, String> bankTransfer = new ProducerRecord<>(BANK_TRANSFERS_TOPIC, createBankTransfer());
+        producer.send(bankTransfer).get();
+    }
+
+    private String createCardPayment() {
+        return "{\"paymentReference\":\"A184028KM0013790\", \"type\":\"card\", \"amount\":\"275\", \"currency\":\"GBP\"}";
+    }
+
+    private String createBankTransfer() {
+        return "{\"paymentReference\":\"19ae2-18mk73-009\", \"type\":\"bank\", \"amount\":\"150\", \"currency\":\"EUR\"}";
+    }
+}

apache-poi-3/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles
+- [How To Convert Excel Data Into List Of Java Objects](https://www.baeldung.com/java-convert-excel-data-into-list)
+- [Expand Columns with Apache POI](https://www.baeldung.com/java-apache-poi-expand-columns)

apache-poi-3/pom.xml

@@ -0,0 +1,97 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xmlns="http://maven.apache.org/POM/4.0.0"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>apache-poi-3</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>apache-poi-3</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.poi</groupId>
+            <artifactId>poi-ooxml</artifactId>
+            <version>${poi.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.poi</groupId>
+            <artifactId>poi-scratchpad</artifactId>
+            <version>${poi.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/com.github.ozlerhakan/poiji -->
+        <dependency>
+            <groupId>com.github.ozlerhakan</groupId>
+            <artifactId>poiji</artifactId>
+            <version>${poiji.version}</version>
+        </dependency>
+
+        <!-- https://mvnrepository.com/artifact/org.apache.poi/poi/5.2.3 -->
+        <dependency>
+            <groupId>org.apache.poi</groupId>
+            <artifactId>poi</artifactId>
+            <version>${poi.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml-schemas/4.1.2 -->
+        <dependency>
+            <groupId>org.apache.poi</groupId>
+            <artifactId>poi-ooxml-schemas</artifactId>
+            <version>4.1.2</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.apache.xmlbeans/xmlbeans/5.1.1 -->
+        <dependency>
+            <groupId>org.apache.xmlbeans</groupId>
+            <artifactId>xmlbeans</artifactId>
+            <version>5.1.1</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 -->
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>4.4</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.dhatim/fastexcel/0.15.7 -->
+        <dependency>
+            <groupId>org.dhatim</groupId>
+            <artifactId>fastexcel</artifactId>
+            <version>${fastexcel.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.dhatim/fastexcel-reader/0.15.7 -->
+        <dependency>
+            <groupId>org.dhatim</groupId>
+            <artifactId>fastexcel-reader</artifactId>
+            <version>${fastexcel.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/net.sourceforge.jexcelapi/jxl/2.6.12 -->
+        <dependency>
+            <groupId>net.sourceforge.jexcelapi</groupId>
+            <artifactId>jxl</artifactId>
+            <version>${jxl.version}</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-api -->
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-api</artifactId>
+            <version>2.17.1</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-core</artifactId>
+            <version>2.17.1</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <poi.version>5.2.3</poi.version>
+        <poiji.version>4.1.1</poiji.version>
+        <fastexcel.version>0.15.7</fastexcel.version>
+        <jxl.version>2.6.12</jxl.version>
+    </properties>
+
+</project>

apache-poi-3/src/main/java/com/baeldung/convert/exceldatatolist/FoodInfo.java

@@ -0,0 +1,54 @@
+package com.baeldung.convert.exceldatatolist;
+
+import com.poiji.annotation.ExcelCellName;
+
+public class FoodInfo {
+
+    @ExcelCellName("Category")
+    private String category; //food category
+    @ExcelCellName("Name")
+    private String name; // food name
+    @ExcelCellName("Measure")
+    private String measure;
+    @ExcelCellName("Calories")
+    private double calories; //amount of calories in kcal/measure
+
+    @Override
+    public String toString() {
+        return "FoodInfo{" + "category='" + category + '\'' + ", name='" + name + '\'' + ", measure='" + measure + '\'' + ", calories=" + calories + "} \n";
+    }
+
+
+    public String getCategory() {
+        return category;
+    }
+
+    public void setCategory(String category) {
+        this.category = category;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getMeasure() {
+        return measure;
+    }
+
+    public void setMeasure(String measure) {
+        this.measure = measure;
+    }
+
+    public double getCalories() {
+        return calories;
+    }
+
+    public void setCalories(double calories) {
+        this.calories = calories;
+    }
+
+}

apache-poi-3/src/main/java/com/baeldung/convert/exceldatatolist/fastexcel/ExcelDataToListOfObjectsFastExcel.java

@@ -0,0 +1,42 @@
+package com.baeldung.convert.exceldatatolist.fastexcel;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.stream.Stream;
+
+import org.dhatim.fastexcel.reader.ReadableWorkbook;
+import org.dhatim.fastexcel.reader.Row;
+import org.dhatim.fastexcel.reader.Sheet;
+
+import com.baeldung.convert.exceldatatolist.FoodInfo;
+
+public class ExcelDataToListOfObjectsFastExcel {
+    public static List<FoodInfo> excelDataToListOfObjets_withFastExcel(String fileLocation)throws IOException, NumberFormatException {
+        List<FoodInfo> foodData = new ArrayList<FoodInfo>();
+
+        try (FileInputStream file = new FileInputStream(fileLocation);
+            ReadableWorkbook wb = new ReadableWorkbook(file)) {
+            Sheet sheet = wb.getFirstSheet();
+            for (Row row:
+                sheet.read()
+            ) {
+                if(row.getRowNum() == 1) {
+                    continue;
+                }
+                FoodInfo food = new FoodInfo();
+                food.setCategory(row.getCellText(0));
+                food.setName(row.getCellText(1));
+                food.setMeasure(row.getCellText(2));
+                food.setCalories(Double.parseDouble(row.getCellText(3)));
+
+                foodData.add(food);
+
+            }
+        }
+
+        return foodData;
+    }
+}

apache-poi-3/src/main/java/com/baeldung/convert/exceldatatolist/jexcelapi/ExcelDataToListOfObjectsJxl.java

@@ -0,0 +1,37 @@
+package com.baeldung.convert.exceldatatolist.jexcelapi;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import com.baeldung.convert.exceldatatolist.FoodInfo;
+
+import jxl.Sheet;
+import jxl.Workbook;
+import jxl.read.biff.BiffException;
+
+public class ExcelDataToListOfObjectsJxl {
+    public static List<FoodInfo> excelDataToListOfObjets_withJxl(String fileLocation) throws IOException, BiffException {
+
+        List<FoodInfo> foodData = new ArrayList<FoodInfo>();
+
+        Workbook workbook = Workbook.getWorkbook(new File(fileLocation));
+        Sheet sheet = workbook.getSheet(0);
+
+        int rows = sheet.getRows();
+
+        for (int i = 1; i < rows; i++) {
+            FoodInfo foodInfo = new FoodInfo();
+
+            foodInfo.setCategory(sheet.getCell(0, i).getContents());
+            foodInfo.setName(sheet.getCell(1, i).getContents());
+            foodInfo.setMeasure(sheet.getCell(2, i).getContents());
+            foodInfo.setCalories(Double.parseDouble(sheet.getCell(3, i).getContents()));
+           
+            foodData.add(foodInfo);
+
+        }
+        return foodData;
+    }
+}

apache-poi-3/src/main/java/com/baeldung/convert/exceldatatolist/poi/ExcelDataToListApachePOI.java

@@ -0,0 +1,39 @@
+package com.baeldung.convert.exceldatatolist.poi;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.poi.ss.usermodel.DataFormatter;
+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.xssf.usermodel.XSSFWorkbook;
+
+import com.baeldung.convert.exceldatatolist.FoodInfo;
+
+public class ExcelDataToListApachePOI {
+    public static List<FoodInfo> excelDataToListOfObjets_withApachePOI(String fileLocation) throws IOException {
+        FileInputStream file = new FileInputStream(new File(fileLocation));
+        Workbook workbook = new XSSFWorkbook(file);
+        Sheet sheet = workbook.getSheetAt(0);
+        List<FoodInfo> foodData = new ArrayList<FoodInfo>();
+        DataFormatter dataFormatter = new DataFormatter();
+        for (int n = 1; n < sheet.getPhysicalNumberOfRows(); n++) {
+            Row row = sheet.getRow(n);
+            FoodInfo foodInfo = new FoodInfo();
+            int i = row.getFirstCellNum();
+
+            foodInfo.setCategory(dataFormatter.formatCellValue(row.getCell(i)));
+            foodInfo.setName(dataFormatter.formatCellValue(row.getCell(++i)));
+            foodInfo.setMeasure(dataFormatter.formatCellValue(row.getCell(++i)));
+            foodInfo.setCalories(Double.parseDouble(dataFormatter.formatCellValue(row.getCell(++i))));
+
+            foodData.add(foodInfo);
+
+        }
+        return foodData;
+    }
+}

apache-poi-3/src/main/java/com/baeldung/convert/exceldatatolist/poiji/ExcelDataToListOfObjectsPOIJI.java

@@ -0,0 +1,13 @@
+package com.baeldung.convert.exceldatatolist.poiji;
+
+import java.io.File;
+import java.util.List;
+
+import com.baeldung.convert.exceldatatolist.FoodInfo;
+import com.poiji.bind.Poiji;
+
+public class ExcelDataToListOfObjectsPOIJI {
+    public static List<FoodInfo> excelDataToListOfObjets_withPOIJI(String fileLocation){
+        return Poiji.fromExcel(new File(fileLocation), FoodInfo.class);
+    }
+}

apache-poi-3/src/test/java/com/baeldung/convert/exceldatatolist/ExcelDataToListOfObjectsUnitTest.java

@@ -0,0 +1,53 @@
+package com.baeldung.convert.exceldatatolist;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.util.List;
+
+// import org.junit.jupiter.api.Test;
+// import static org.junit.jupiter.api.Assertions.*;
+import org.junit.Test;
+
+import com.baeldung.convert.exceldatatolist.fastexcel.ExcelDataToListOfObjectsFastExcel;
+import com.baeldung.convert.exceldatatolist.jexcelapi.ExcelDataToListOfObjectsJxl;
+import com.baeldung.convert.exceldatatolist.poi.ExcelDataToListApachePOI;
+import com.baeldung.convert.exceldatatolist.poiji.ExcelDataToListOfObjectsPOIJI;
+
+import jxl.read.biff.BiffException;
+
+public class ExcelDataToListOfObjectsUnitTest {
+
+    @Test
+    public void whenParsingExcelFileWithPOIJI_thenConvertsToList() throws IOException {
+        List<FoodInfo> foodInfoList = ExcelDataToListOfObjectsPOIJI.excelDataToListOfObjets_withPOIJI("src/main/resources/food_info.xlsx");
+
+        assertEquals("Beverages", foodInfoList.get(0).getCategory());
+        assertEquals("Dairy", foodInfoList.get(3).getCategory());
+    }
+
+    @Test
+    public void whenParsingExcelFileWithApachePOI_thenConvertsToList() throws IOException {
+        List<FoodInfo> foodInfoList = ExcelDataToListApachePOI.excelDataToListOfObjets_withApachePOI("src/main/resources/food_info.xlsx");
+
+        assertEquals("Beverages", foodInfoList.get(0).getCategory());
+        assertEquals("Dairy", foodInfoList.get(3).getCategory());
+    }
+
+    @Test
+    public void whenParsingExcelFileWithFastExcel_thenConvertsToList() throws IOException {
+        List<FoodInfo> foodInfoList = ExcelDataToListOfObjectsFastExcel.excelDataToListOfObjets_withFastExcel("src/main/resources/food_info.xlsx");
+
+        assertEquals("Beverages", foodInfoList.get(0).getCategory());
+        assertEquals("Dairy", foodInfoList.get(3).getCategory());
+    }
+
+    @Test
+    public void whenParsingExcelFileWithJxl_thenConvertsToList() throws IOException, BiffException {
+        List<FoodInfo> foodInfoList = ExcelDataToListOfObjectsJxl.excelDataToListOfObjets_withJxl("src/main/resources/food_info.xls");
+
+        assertEquals("Beverages", foodInfoList.get(0).getCategory());
+        assertEquals("Dairy", foodInfoList.get(3).getCategory());
+    }
+
+}

apache-poi-3/src/test/java/com/baeldung/poi/excel/expandcolumn/ExpandColumnUnitTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.poi.excel.expandcolumn;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.io.IOException;
+
+import org.apache.poi.ss.usermodel.*;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class ExpandColumnUnitTest {
+
+    private Workbook workbook;
+    private Sheet sheet;
+
+    @BeforeEach
+    void prepareSpreadsheet() {
+        workbook = new XSSFWorkbook();
+        sheet = workbook.createSheet();
+
+        Row headerRow = sheet.createRow(0);
+        Cell headerCell1 = headerRow.createCell(0);
+        headerCell1.setCellValue("Full Name");
+        Cell headerCell2 = headerRow.createCell(1);
+        headerCell2.setCellValue("Abbreviation");
+
+        Row dataRow = sheet.createRow(1);
+        Cell dataCell1 = dataRow.createCell(0);
+        dataCell1.setCellValue("Java Virtual Machine");
+        Cell dataCell2 = dataRow.createCell(1);
+        dataCell2.setCellValue("JVM");
+
+        dataRow = sheet.createRow(2);
+        dataCell1 = dataRow.createCell(0);
+        dataCell1.setCellValue("Java Runtime Environment");
+        dataCell2 = dataRow.createCell(1);
+        dataCell2.setCellValue("JRE");
+    }
+
+    @Test
+    void whenSetColumnWidth_thenColumnSetToTheSpecifiedWidth() {
+
+        Row row = sheet.getRow(2);
+        String cellValue = row.getCell(0).getStringCellValue();
+        int targetWidth = cellValue.length() * 256;
+
+        sheet.setColumnWidth(0, targetWidth);
+
+        assertEquals(targetWidth, sheet.getColumnWidth(0));
+    }
+
+    @Test
+    void whenAutoSizeColumn_thenColumnExpands() {
+
+        int originalWidth = sheet.getColumnWidth(0);
+
+        sheet.autoSizeColumn(0);
+
+        assertThat(sheet.getColumnWidth(0)).isGreaterThan(originalWidth);
+    }
+
+    @AfterEach
+    void cleanup() throws IOException {
+        workbook.close();
+    }
+
+}

aws-modules/aws-s3/README.md

@@ -4,7 +4,7 @@ This module contains articles about Simple Storage Service (S3) on AWS
 
 ### Relevant articles
 
-- [AWS S3 with Java](https://www.baeldung.com/aws-s3-java)
+- [AWS S3 with Java](https://www.baeldung.com/java-aws-s3)
 - [Multipart Uploads in Amazon S3 with Java](https://www.baeldung.com/aws-s3-multipart-upload)
 - [Using the JetS3t Java Client With Amazon S3](https://www.baeldung.com/jets3t-amazon-s3)
 - [Check if a Specified Key Exists in a Given S3 Bucket Using Java](https://www.baeldung.com/java-aws-s3-check-specified-key-exists)

core-java-modules/core-java-16/README.md

@@ -5,3 +5,4 @@
 - [Collecting Stream Elements into a List in Java](https://www.baeldung.com/java-stream-to-list-collecting)
 - [New Features in Java 16](https://www.baeldung.com/java-16-new-features)
 - [Guide to Java 8 groupingBy Collector](https://www.baeldung.com/java-groupingby-collector)
+- [Value-Based Classes in Java](https://www.baeldung.com/java-value-based-classes)

core-java-modules/core-java-16/src/main/java/com/baeldung/value_based_class/Point.java

@@ -0,0 +1,49 @@
+package com.baeldung.value_based_class;
+
+import java.util.Objects;
+
+import jdk.internal.ValueBased;
+
+/**
+ * This class is written with the intention that it can serve as an example of
+ * what a Value-based class could be.
+ */
+
+@ValueBased
+public final class Point {
+    private final int x;
+    private final int y;
+    private final int z;
+
+    private static Point ORIGIN = new Point(0, 0, 0);
+
+    private Point(int x, int y, int z) {
+        this.x = x;
+        this.y = y;
+        this.z = z;
+    }
+
+    public static Point valueOfPoint(int x, int y, int z) {
+        // returns a cached instance if it is origin, or a new instance
+        if (isOrigin(x, y, z))
+            return ORIGIN;
+        return new Point(x, y, z);
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == null || getClass() != other.getClass())
+            return false;
+        Point point = (Point) other;
+        return x == point.x && y == point.y && z == point.z;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(x, y, z);
+    }
+
+    private static boolean isOrigin(int x, int y, int z) {
+        return x == 0 && y == 0 && z == 0;
+    }
+}

core-java-modules/core-java-16/src/test/java/com/baeldung/value_based_class/ValueBasedClassUnitTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.value_based_class;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ValueBasedClassUnitTest {
+    @Test
+    public void givenAutoboxedAndPrimitive_whenCompared_thenReturnEquals() {
+        int primitive_a = 125;
+        Integer obj_a = 125; // this is autoboxed
+        Assert.assertSame(primitive_a, obj_a);
+    }
+
+    @Test
+    public void givenValueBasedPoint_whenCreated_thenReturnsObjects() {
+        Point p1 = Point.valueOfPoint(1, 2, 3);
+        Point p2 = Point.valueOfPoint(2, 3, 4);
+
+        Assert.assertNotEquals(p1, p2);
+    }
+
+    @Test
+    public void givenValueBasedPoint_whenCompared_thenReturnEquals() {
+        Point p1 = Point.valueOfPoint(1, 2, 3);
+        Point p2 = Point.valueOfPoint(1, 2, 3);
+
+        Assert.assertEquals(p1, p2);
+    }
+
+    @Test
+    public void givenValueBasedPoint_whenOrigin_thenReturnCachedInstance() {
+        Point p1 = Point.valueOfPoint(0, 0, 0);
+        Point p2 = Point.valueOfPoint(0, 0, 0);
+        Point p3 = Point.valueOfPoint(1, 2, 3);
+
+        // the following should not be assumed for value-based classes
+
+        Assert.assertTrue(p1 == p2);
+        Assert.assertFalse(p1 == p3);
+    }
+}

core-java-modules/core-java-21/README.md

@@ -1 +1,5 @@
-## Relevant Articles
+## Relevant Articles
+- [Sequenced Collections in Java 21](https://www.baeldung.com/java-21-sequenced-collections)
+- [String Templates in Java 21](https://www.baeldung.com/java-21-string-templates)
+- [Unnamed Classes and Instance Main Methods in Java 21](https://www.baeldung.com/java-21-unnamed-class-instance-main)
+- [Unnamed Patterns and Variables in Java 21](https://www.baeldung.com/java-unnamed-patterns-variables)

core-java-modules/core-java-21/pom.xml

@@ -12,23 +12,36 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
-<!--    <build>-->
-<!--        <plugins>-->
-<!--            <plugin>-->
-<!--                <groupId>org.apache.maven.plugins</groupId>-->
-<!--                <artifactId>maven-compiler-plugin</artifactId>-->
-<!--                <configuration>-->
-<!--                    <source>{maven.compiler.source.version}</source>-->
-<!--                    <target>{maven.compiler.target.version}</target>-->
-<!--                </configuration>-->
-<!--            </plugin>-->
-<!--        </plugins>-->
-<!--    </build>-->
+    <properties>
+        <maven.compiler.source.version>21</maven.compiler.source.version>
+        <maven.compiler.target.version>21</maven.compiler.target.version>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
 
-<!--    <properties>-->
-<!--        <maven.compiler.source.version>21</maven.compiler.source.version>-->
-<!--        <maven.compiler.target.version>21</maven.compiler.target.version>-->
-<!--        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>-->
-<!--    </properties>-->
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>21</source>
+                    <target>21</target>
+                    <!-- Needed due to a bug with JDK 21, described here: https://issues.apache.org/jira/browse/MCOMPILER-546?page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel&focusedCommentId=17767513 -->
+                    <debug>false</debug>
+                    <compilerArgs>
+                        <arg>--enable-preview</arg>
+                    </compilerArgs>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <argLine>--enable-preview</argLine>
+                </configuration>
+            </plugin>
+
+        </plugins>
+    </build>
 
 </project>

core-java-modules/core-java-21/src/main/java/com/baeldung/stringtemplates/StringCompositionTechniques.java

@@ -0,0 +1,37 @@
+package com.baeldung.stringtemplates;
+
+import java.text.MessageFormat;
+
+public class StringCompositionTechniques {
+    String composeUsingPlus(String feelsLike, String temperature, String unit) {
+        return "Today's weather is " + feelsLike + ", with a temperature of " + temperature + " degrees " + unit;
+    }
+
+    String composeUsingStringBuffer(String feelsLike, String temperature, String unit) {
+        return new StringBuffer().append("Today's weather is ")
+          .append(feelsLike)
+          .append(", with a temperature of ")
+          .append(temperature)
+          .append(" degrees ")
+          .append(unit)
+          .toString();
+    }
+
+    String composeUsingStringBuilder(String feelsLike, String temperature, String unit) {
+        return new StringBuilder().append("Today's weather is ")
+          .append(feelsLike)
+          .append(", with a temperature of ")
+          .append(temperature)
+          .append(" degrees ")
+          .append(unit)
+          .toString();
+    }
+
+    String composeUsingFormatters(String feelsLike, String temperature, String unit) {
+        return String.format("Today's weather is %s, with a temperature of %s degrees %s", feelsLike, temperature, unit);
+    }
+
+    String composeUsingMessageFormatter(String feelsLike, String temperature, String unit) {
+        return MessageFormat.format("Today''s weather is {0}, with a temperature of {1} degrees {2}", feelsLike, temperature, unit);
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/stringtemplates/StringTemplateExamples.java

@@ -0,0 +1,56 @@
+package com.baeldung.stringtemplates;
+
+import static java.lang.StringTemplate.RAW;
+import static java.util.FormatProcessor.FMT;
+
+public class StringTemplateExamples {
+    String interpolationUsingSTRProcessor(String feelsLike, String temperature, String unit) {
+        return STR
+          . "Today's weather is \{ feelsLike }, with a temperature of \{ temperature } degrees \{ unit }" ;
+    }
+
+    String interpolationOfJSONBlock(String feelsLike, String temperature, String unit) {
+        return STR
+          . """
+          {
+            "feelsLike": "\{ feelsLike }",
+            "temperature": "\{ temperature }",
+            "unit": "\{ unit }"
+          }
+          """ ;
+    }
+
+    String interpolationWithExpressions() {
+        return STR
+          . "Today's weather is \{ getFeelsLike() }, with a temperature of \{ getTemperature() } degrees \{ getUnit() }" ;
+    }
+
+    String interpolationWithTemplates() {
+        StringTemplate str = RAW
+          . "Today's weather is \{ getFeelsLike() }, with a temperature of \{ getTemperature() } degrees \{ getUnit() }" ;
+        return STR.process(str);
+    }
+
+    String interpolationOfJSONBlockWithFMT(String feelsLike, float temperature, String unit) {
+        return FMT
+          . """
+      {
+        "feelsLike": "%1s\{ feelsLike }",
+        "temperature": "%2.2f\{ temperature }",
+        "unit": "%1s\{ unit }"
+      }
+      """ ;
+    }
+
+    private String getFeelsLike() {
+        return "pleasant";
+    }
+
+    private String getTemperature() {
+        return "25";
+    }
+
+    private String getUnit() {
+        return "Celsius";
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamed/variables/Car.java

@@ -0,0 +1,11 @@
+package com.baeldung.unnamed.variables;
+
+public record Car<T extends Engine>(String name, String color, T engine) { }
+
+abstract class Engine { }
+
+class GasEngine extends Engine { }
+
+class ElectricEngine extends Engine { }
+
+class HybridEngine extends Engine { }

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamed/variables/UnnamedPatterns.java

@@ -0,0 +1,50 @@
+package com.baeldung.unnamed.variables;
+
+public class UnnamedPatterns {
+
+    static String getObjectsColorWithNamedPattern(Object object) {
+        if (object instanceof Car(String name, String color, Engine engine)) {
+            return color;
+        }
+        return "No color!";
+    }
+
+    static String getObjectsColorWithUnnamedPattern(Object object) {
+        if (object instanceof Car(_, String color, _)) {
+            return color;
+        }
+        return "No color!";
+    }
+
+    static String getObjectsColorWithSwitchAndNamedPattern(Object object) {
+        return switch (object) {
+            case Car(String name, String color, Engine engine) -> color;
+            default -> "No color!";
+        };
+    }
+
+    static String getObjectsColorWithSwitchAndUnnamedPattern(Object object) {
+        return switch (object) {
+            case Car(_, String color, _) -> color;
+            default -> "No color!";
+        };
+    }
+
+    static String getEngineTypeWithNamedPattern(Car<?> car) {
+        return switch (car) {
+            case Car(String name, String color, GasEngine engine) -> "gas";
+            case Car(String name, String color, ElectricEngine engine) -> "electric";
+            case Car(String name, String color, HybridEngine engine) -> "hybrid";
+            default -> "none";
+        };
+    }
+
+    static String getEngineTypeWithUnnamedPattern(Car<?> car) {
+        return switch (car) {
+            case Car(_, _, GasEngine _) -> "gas";
+            case Car(_, _, ElectricEngine _) -> "electric";
+            case Car(_, _, HybridEngine _) -> "hybrid";
+            default -> "none";
+        };
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamed/variables/UnnamedVariables.java

@@ -0,0 +1,134 @@
+package com.baeldung.unnamed.variables;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+
+class Transaction implements AutoCloseable {
+
+    @Override
+    public void close() {
+        System.out.println("Closed!");
+    }
+}
+
+public class UnnamedVariables {
+
+    static int countCarsOverLimitWithNamedVariable(Collection<Car<?>> cars, int limit) {
+        var total = 0;
+        var totalOverLimit = 0;
+        for (var car : cars) {
+            total++;
+            if (total > limit) {
+                totalOverLimit++;
+                // side effect
+            }
+        }
+        return totalOverLimit;
+    }
+
+    static int countCarsOverLimitWithUnnamedVariable(Collection<Car<?>> cars, int limit) {
+        var total = 0;
+        var totalOverLimit = 0;
+        for (var _ : cars) {
+            total++;
+            if (total > limit) {
+                totalOverLimit++;
+                // side effect
+            }
+        }
+        return totalOverLimit;
+    }
+
+    static void sendNotificationToCarsWithNamedVariable(Collection<Car<?>> cars) {
+        sendOneTimeNotification();
+        for (int i = 0; i < cars.size(); i++) {
+            // Notify car
+        }
+    }
+
+    static void sendNotificationToCarsWithUnnamedVariable(Collection<Car<?>> cars) {
+        for (int i = 0, _ = sendOneTimeNotification(); i < cars.size(); i++) {
+            // Notify car
+        }
+    }
+
+    private static int sendOneTimeNotification() {
+        System.out.println("Sending one time notification!");
+        return 1;
+    }
+
+    static Car<?> removeThreeCarsAndReturnFirstRemovedWithNamedVariables(Queue<Car<?>> cars) {
+        var x = cars.poll();
+        var y = cars.poll();
+        var z = cars.poll();
+        return x;
+    }
+
+    static Car<?> removeThreeCarsAndReturnFirstRemovedWithUnnamedVariables(Queue<Car<?>> cars) {
+        var car = cars.poll();
+        var _ = cars.poll();
+        var _ = cars.poll();
+        return car;
+    }
+
+    static void handleCarExceptionWithNamedVariables(Car<?> car) {
+        try {
+            someOperationThatFails(car);
+        } catch (IllegalStateException ex) {
+            System.out.println("Got an illegal state exception for: " + car.name());
+        } catch (RuntimeException ex) {
+            System.out.println("Got a runtime exception!");
+        }
+    }
+
+    static void handleCarExceptionWithUnnamedVariables(Car<?> car) {
+        try {
+            someOperationThatFails(car);
+        } catch (IllegalStateException | NumberFormatException _) {
+            System.out.println("Got an illegal state exception for: " + car.name());
+        } catch (RuntimeException _) {
+            System.out.println("Got a runtime exception!");
+        }
+    }
+
+    static void obtainTransactionAndUpdateCarWithNamedVariables(Car<?> car) {
+        try (var transaction = new Transaction()) {
+            updateCar(car);
+        }
+    }
+
+    static void obtainTransactionAndUpdateCarWithUnnamedVariables(Car<?> car) {
+        try (var _ = new Transaction()) {
+            updateCar(car);
+        }
+    }
+
+    static void updateCar(Car<?> car) {
+        // Some update logic
+        System.out.println("Car updated!");
+    }
+
+    static Map<String, List<Car<?>>> getCarsByFirstLetterWithNamedVariables(List<Car<?>> cars) {
+        Map<String, List<Car<?>>> carMap = new HashMap<>();
+        cars.forEach(car ->
+            carMap.computeIfAbsent(car.name().substring(0, 1), firstLetter -> new ArrayList<>()).add(car)
+        );
+        return carMap;
+    }
+
+    static Map<String, List<Car<?>>> getCarsByFirstLetterWithUnnamedVariables(List<Car<?>> cars) {
+        Map<String, List<Car<?>>> carMap = new HashMap<>();
+        cars.forEach(car ->
+            carMap.computeIfAbsent(car.name().substring(0, 1), _ -> new ArrayList<>()).add(car)
+        );
+        return carMap;
+    }
+
+    private static void someOperationThatFails(Car<?> car) {
+        throw new IllegalStateException("Triggered exception for: " + car.name());
+    }
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamedclasses/HelloWorld.java

@@ -0,0 +1,3 @@
+void main() {
+    System.out.println("Hello, World!");
+}

core-java-modules/core-java-21/src/main/java/com/baeldung/unnamedclasses/HelloWorldChild.java

@@ -0,0 +1,7 @@
+package com.baeldung.unnamedclasses;
+
+public class HelloWorldChild extends HelloWorldSuper {
+    void main() {
+        System.out.println("Hello, World!");
+    }
+}