Merge branch 'master' into JAVA-13136

apache-spark/src/test/java/com/baeldung/dataframes/CustomerToDataFrameConverterAppUnitTest.java

@@ -8,6 +8,8 @@ import java.util.List;
 
 import org.apache.spark.sql.Dataset;
 import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SparkSession;
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
 class CustomerToDataFrameConverterAppUnitTest {
@@ -59,4 +61,9 @@ class CustomerToDataFrameConverterAppUnitTest {
         assertEquals( "Male", row2.getAs("gender"));
         assertEquals( 1200, (int)row2.getAs("transaction_amount"));
     }
+    
+    @AfterEach
+    public void cleanup() {
+    	SparkSession.getActiveSession().get().close();
+    }
 }

core-java-modules/core-java-14/README.md

@@ -11,3 +11,4 @@ This module contains articles about Java 14.
 - [Foreign Memory Access API in Java 14](https://www.baeldung.com/java-foreign-memory-access)
 - [Java 14 Record Keyword](https://www.baeldung.com/java-record-keyword)
 - [New Features in Java 14](https://www.baeldung.com/java-14-new-features)
+- [Java 14 Record vs. Lombok](https://www.baeldung.com/java-record-vs-lombok)

core-java-modules/core-java-14/pom.xml

@@ -14,6 +14,15 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>1.18.24</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
     <build>
         <plugins>
             <plugin>

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/recordvslombok/ColorData.java

@@ -0,0 +1,18 @@
+package com.baeldung.java14.recordvslombok;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+@Data
+@AllArgsConstructor
+public class ColorData {
+
+    private int red;
+    private int green;
+    private int blue;
+
+    public String getHexString() {
+        return String.format("#%02X%02X%02X", red, green, blue);
+    }
+
+}

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/recordvslombok/ColorRecord.java

@@ -0,0 +1,8 @@
+package com.baeldung.java14.recordvslombok;
+
+public record ColorRecord(int red, int green, int blue) {
+
+    public String getHexString() {
+        return String.format("#%02X%02X%02X", red, green, blue);
+    }
+}

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/recordvslombok/ColorValueObject.java

@@ -0,0 +1,17 @@
+package com.baeldung.java14.recordvslombok;
+
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.Value;
+
+@Value
+@Getter(AccessLevel.NONE)
+public class ColorValueObject {
+    int red;
+    int green;
+    int blue;
+
+    public String getHexString() {
+        return String.format("#%02X%02X%02X", red, green, blue);
+    }
+}

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/recordvslombok/MonochromeColor.java

@@ -0,0 +1,12 @@
+package com.baeldung.java14.recordvslombok;
+
+import lombok.Value;
+
+@Value
+public class MonochromeColor extends ColorData {
+
+    public MonochromeColor(int grayScale) {
+        super(grayScale, grayScale, grayScale);
+    }
+
+}

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/recordvslombok/StudentBuilder.java

@@ -0,0 +1,17 @@
+package com.baeldung.java14.recordvslombok;
+
+import lombok.Builder;
+import lombok.Getter;
+
+@Getter
+@Builder
+public class StudentBuilder {
+    private String firstName;
+    private String lastName;
+    private Long studentId;
+    private String email;
+    private String phoneNumber;
+    private String address;
+    private String country;
+    private int age;
+}

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/recordvslombok/StudentRecord.java

@@ -0,0 +1,4 @@
+package com.baeldung.java14.recordvslombok;
+
+public record StudentRecord(String firstName, String lastName, Long studentId, String email, String phoneNumber, String address, String country, int age) {
+}

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/recordvslombok/RecordVsLombokUntTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.java14.recordvslombok;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class RecordVsLombokUntTest {
+
+    @Test
+    public void givenAColorRecord_hexStringIsCorrect() {
+        var red = new ColorRecord(255, 0, 0);
+
+        assertThat(red.getHexString()).isEqualTo("#FF0000");
+    }
+
+    @Test
+    public void givenAColorValueObject_hexStringIsCorrect() {
+        var red = new ColorValueObject(255, 0, 0);
+
+        assertThat(red.getHexString()).isEqualTo("#FF0000");
+    }
+
+    @Test
+    public void givenRecordWithManyAttributes_firstNameShouldBeJohn() {
+        StudentRecord john = new StudentRecord("John", "Doe", null, "john@doe.com", null, null, "England", 20);
+
+        assertThat(john.firstName()).isEqualTo("John");
+    }
+
+    @Test
+    public void givenBuilderWithManyAttributes_firstNameShouldBeJohn() {
+        StudentBuilder john = StudentBuilder.builder()
+            .firstName("John")
+            .lastName("Doe")
+            .email("john@doe.com")
+            .country("England")
+            .age(20)
+            .build();
+
+        assertThat(john.getFirstName()).isEqualTo("John");
+    }
+
+}

core-java-modules/core-java-15/README.md

@@ -5,4 +5,3 @@ This module contains articles about Java 15.
 ### Relevant articles
 
 - [Hidden Classes in Java 15](https://www.baeldung.com/java-hidden-classes)
-- [Sealed Classes and Interfaces in Java 15](https://www.baeldung.com/java-sealed-classes-interfaces)

core-java-modules/core-java-16/src/main/java/com/baeldung/java_16_features/groupingby/BlogPost.java

@@ -10,7 +10,7 @@ public class BlogPost {
     private BlogPostType type;
     private int likes;
     record AuthPostTypesLikes(String author, BlogPostType type, int likes) {};
-    record PostcountTitlesLikesStats(long postCount, String titles, IntSummaryStatistics likesStats){};
+    record PostCountTitlesLikesStats(long postCount, String titles, IntSummaryStatistics likesStats){};
     record TitlesBoundedSumOfLikes(String titles, int boundedSumOfLikes) {};
 
     public BlogPost(String title, String author, BlogPostType type, int likes) {

core-java-modules/core-java-16/src/test/java/com/baeldung/java_16_features/groupingby/JavaGroupingByCollectorUnitTest.java

@@ -257,7 +257,7 @@ public class JavaGroupingByCollectorUnitTest {
     @Test
     public void givenListOfPosts_whenGroupedByAuthor_thenGetAMapUsingCollectingAndThen() {
 
-        Map<String, BlogPost.PostcountTitlesLikesStats> postsPerAuthor = posts.stream()
+        Map<String, BlogPost.PostCountTitlesLikesStats> postsPerAuthor = posts.stream()
             .collect(groupingBy(BlogPost::getAuthor, collectingAndThen(toList(), list -> {
                 long count = list.stream()
                     .map(BlogPost::getTitle)
@@ -267,10 +267,10 @@ public class JavaGroupingByCollectorUnitTest {
                     .collect(joining(" : "));
                 IntSummaryStatistics summary = list.stream()
                     .collect(summarizingInt(BlogPost::getLikes));
-                return new BlogPost.PostcountTitlesLikesStats(count, titles, summary);
+                return new BlogPost.PostCountTitlesLikesStats(count, titles, summary);
             })));
 
-        BlogPost.PostcountTitlesLikesStats result = postsPerAuthor.get("Author 1");
+        BlogPost.PostCountTitlesLikesStats result = postsPerAuthor.get("Author 1");
         assertThat(result.postCount()).isEqualTo(3L);
         assertThat(result.titles()).isEqualTo("News item 1 : Programming guide : Tech review 2");
         assertThat(result.likesStats().getMax()).isEqualTo(20);

core-java-modules/core-java-17/README.md

@@ -5,3 +5,4 @@
 - [Introduction to HexFormat in Java 17](https://www.baeldung.com/java-hexformat)
 - [New Features in Java 17](https://www.baeldung.com/java-17-new-features)
 - [Random Number Generators in Java 17](https://www.baeldung.com/java-17-random-number-generators)
+- [Sealed Classes and Interfaces in Java 17](https://www.baeldung.com/java-sealed-classes-interfaces)

core-java-modules/core-java-17/src/test/java/com/baeldung/sealed/classes/VehicleUnitTest.java

@@ -21,7 +21,7 @@ public class VehicleUnitTest {
     public void givenCar_whenUsingReflectionAPI_thenSuperClassIsSealed() {
         Assertions.assertThat(car.getClass().isSealed()).isEqualTo(false);
         Assertions.assertThat(car.getClass().getSuperclass().isSealed()).isEqualTo(true);
-        Assertions.assertThat(car.getClass().getSuperclass().permittedSubclasses())
+        Assertions.assertThat(car.getClass().getSuperclass().getPermittedSubclasses())
                 .contains(ClassDesc.of(car.getClass().getCanonicalName()));
     }
 
@@ -29,7 +29,7 @@ public class VehicleUnitTest {
     public void givenTruck_whenUsingReflectionAPI_thenSuperClassIsSealed() {
         Assertions.assertThat(truck.getClass().isSealed()).isEqualTo(false);
         Assertions.assertThat(truck.getClass().getSuperclass().isSealed()).isEqualTo(true);
-        Assertions.assertThat(truck.getClass().getSuperclass().permittedSubclasses())
+        Assertions.assertThat(truck.getClass().getSuperclass().getPermittedSubclasses())
                 .contains(ClassDesc.of(truck.getClass().getCanonicalName()));
     }
 

core-java-modules/core-java-9/src/test/java/com/baeldung/java9/inputstream/outputstream/InputStreamToOutputStreamUnitTest.java

@@ -20,7 +20,7 @@ public class InputStreamToOutputStreamUnitTest {
     void copy(InputStream source, OutputStream target) throws IOException {
         byte[] buf = new byte[8192];
         int length;
-        while ((length = source.read(buf)) > 0) {
+        while ((length = source.read(buf)) != -1) {
             target.write(buf, 0, length);
         }
     }

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

@@ -10,3 +10,5 @@ This module contains articles about JAR files
 - [Get Names of Classes Inside a JAR File](https://www.baeldung.com/jar-file-get-class-names)
 - [Find All Jars Containing Given Class](https://baeldung.com/find-all-jars-containing-given-class/)
 - [Creating JAR Files Programmatically](https://www.baeldung.com/jar-create-programatically)
+- [Guide to Creating Jar Executables and Windows Executables from Java](https://www.baeldung.com/jar-windows-executables)
+- [Get the Full Path of a JAR File From a Class](https://www.baeldung.com/java-full-path-of-jar-from-class)

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

@@ -54,6 +54,12 @@
             <artifactId>moneta</artifactId>
             <version>${javamoney.moneta.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-junit-jupiter</artifactId>
+            <version>${mockito.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
@@ -266,6 +272,7 @@
         <!-- util -->
         <unix4j.version>0.4</unix4j.version>
         <grep4j.version>1.8.7</grep4j.version>
+        <mockito.version>4.6.1</mockito.version>
         <!-- maven plugins -->
         <javamoney.moneta.version>1.1</javamoney.moneta.version>
         <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>

core-java-modules/core-java-jar/src/main/java/com/baeldung/jar/MySampleGUIAppn.java

@@ -0,0 +1,31 @@
+package com.baeldung.jar;
+
+import java.awt.event.*;
+import java.awt.*;
+
+import javax.swing.*;
+
+public class MySampleGUIAppn extends JFrame {
+    public  MySampleGUIAppn() {
+        if (!GraphicsEnvironment.isHeadless()) {
+            setSize(300,300);
+            setTitle("MySampleGUIAppn");
+            Button b = new Button("Click Me!");
+            b.setBounds(30,100,80,30);
+            add(b);
+            setVisible(true);
+            addWindowListener(new WindowAdapter() {
+                public void windowClosing(WindowEvent e) {
+                    dispose();
+                    System.exit(0);
+                }
+            });
+        }
+        else {
+            System.exit(0);
+        }
+    }
+    public static void main(String[] args) {
+        MySampleGUIAppn app=new  MySampleGUIAppn();
+    }
+}

core-java-modules/core-java-jar/src/main/java/com/baeldung/jarfile/JarFilePathResolver.java

@@ -0,0 +1,42 @@
+package com.baeldung.jarfile;
+
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.file.Paths;
+
+public class JarFilePathResolver {
+
+    public String getJarFilePath(Class clazz) {
+        try {
+            return byGetProtectionDomain(clazz);
+        } catch (Exception e) {
+            // cannot get jar file path using byGetProtectionDomain
+            // Exception handling omitted
+        }
+        return byGetResource(clazz);
+    }
+
+    String byGetProtectionDomain(Class clazz) throws URISyntaxException {
+        URL url = clazz.getProtectionDomain().getCodeSource().getLocation();
+        return Paths.get(url.toURI()).toString();
+    }
+
+    String byGetResource(Class clazz) {
+        final URL classResource = clazz.getResource(clazz.getSimpleName() + ".class");
+        if (classResource == null) {
+            throw new RuntimeException("class resource is null");
+        }
+
+        final String url = classResource.toString();
+        if (url.startsWith("jar:file:")) {
+            // extract 'file:......jarName.jar' part from the url string
+            String path = url.replaceAll("^jar:(file:.*[.]jar)!/.*", "$1");
+            try {
+                return Paths.get(new URL(path).toURI()).toString();
+            } catch (Exception e) {
+                throw new RuntimeException("Invalid Jar File URL String");
+            }
+        }
+        throw new RuntimeException("Invalid Jar File URL String");
+    }
+}

core-java-modules/core-java-jar/src/test/java/com/baeldung/jar/MySampleGUIAppnUnitTest.java

@@ -0,0 +1,15 @@
+package com.baeldung.jar;
+
+import java.io.IOException;
+
+import org.junit.jupiter.api.Test;
+
+class MySampleGUIAppnUnitTest {
+    @Test
+    void testMain() throws IOException {
+        System.setProperty("java.awt.headless", "true");
+        String [] args = null;
+        System.exit(0);
+        MySampleGUIAppn.main(args);
+    }
+}

core-java-modules/core-java-jar/src/test/java/com/baeldung/jarfile/JarFilePathResolverUnitTest.java

@@ -0,0 +1,55 @@
+package com.baeldung.jarfile;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import com.google.common.base.Ascii;
+import java.io.File;
+import java.net.URISyntaxException;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Spy;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class JarFilePathResolverUnitTest {
+    @Spy
+    JarFilePathResolver jarFilePathResolver;
+
+    @Test
+    void givenClassObjectWhenCallingByGetProtectionDomainShouldGetExpectedPath() throws Exception {
+        String jarPath = jarFilePathResolver.byGetProtectionDomain(Ascii.class);
+        assertThat(jarPath).endsWith(".jar").contains("guava");
+        assertThat(new File(jarPath)).exists();
+    }
+
+    @Test
+    void givenClassObjectWhenCallingByGetResourceShouldGetExpectedPath() {
+        String jarPath = jarFilePathResolver.byGetResource(Ascii.class);
+        assertThat(jarPath).endsWith(".jar").contains("guava");
+        assertThat(new File(jarPath)).exists();
+    }
+
+    @Test
+    void givenClassObjectWhenNoSecurityExceptionRaisedShouldGetExpectedPath() throws URISyntaxException {
+        String jarPath = jarFilePathResolver.getJarFilePath(Ascii.class);
+        assertThat(jarPath).endsWith(".jar").contains("guava");
+        assertThat(new File(jarPath)).exists();
+        verify(jarFilePathResolver, times(1)).byGetProtectionDomain(Ascii.class);
+        verify(jarFilePathResolver, never()).byGetResource(Ascii.class);
+    }
+
+    @Test
+    void givenClassObjectWhenSecurityExceptionRaisedShouldGetExpectedPath() throws URISyntaxException {
+        when(jarFilePathResolver.byGetProtectionDomain(Ascii.class)).thenThrow(new SecurityException("not allowed"));
+        String jarPath = jarFilePathResolver.getJarFilePath(Ascii.class);
+        assertThat(jarPath).endsWith(".jar").contains("guava");
+        assertThat(new File(jarPath)).exists();
+        verify(jarFilePathResolver, times(1)).byGetProtectionDomain(Ascii.class);
+        verify(jarFilePathResolver, times(1)).byGetResource(Ascii.class);
+    }
+
+}

core-java-modules/core-java-lang-5/README.md

@@ -5,3 +5,4 @@ This module contains articles about core features in the Java language
 ### Relevant Articles:
 
 - [Difference Between == and equals() in Java](https://www.baeldung.com/java-equals-method-operator-difference)
+- [Advantages and Disadvantages of Using Java Wildcard Imports](https://www.baeldung.com/java-wildcard-imports)

core-java-modules/core-java-lang-5/pom.xml

@@ -13,7 +13,6 @@
         <artifactId>core-java-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
     </parent>
-
     <build>
         <finalName>core-java-lang-5</finalName>
         <resources>
@@ -23,5 +22,4 @@
             </resource>
         </resources>
     </build>
-
 </project>

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/imports/specific/Book.java

@@ -0,0 +1,17 @@
+package com.baeldung.imports.specific;
+
+import java.util.Date;
+import java.util.List;
+import java.util.UUID;
+
+public class Book {
+
+    private UUID id;
+
+    private String name;
+
+    private Date datePublished;
+
+    private List<String> authors;
+
+}

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/imports/wildcard/Book.java

@@ -0,0 +1,15 @@
+package com.baeldung.imports.wildcard;
+
+import java.util.*;
+
+public class Book {
+
+    private UUID id;
+
+    private String name;
+
+    private Date datePublished;
+
+    private List<String> authors;
+
+}

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/imports/wildcard/BookView.java

@@ -0,0 +1,17 @@
+package com.baeldung.imports.wildcard;
+
+import java.awt.*;
+import java.util.*;
+import java.util.List;
+
+public class BookView extends Frame {
+
+    private UUID id;
+
+    private String name;
+
+    private Date datePublished;
+
+    private List<String> authors;
+
+}

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/imports/wildcard/Library.java

@@ -0,0 +1,19 @@
+package com.baeldung.imports.wildcard;
+
+import java.util.*;
+import java.sql.*;
+import java.sql.Date;
+
+public class Library {
+
+    private UUID id;
+
+    private String name;
+
+    private Time openingTime;
+
+    private Time closingTime;
+
+    private List<Date> datesClosed;
+
+}

core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/PersonAndEmployeeReflectionUnitTest.java

@@ -9,7 +9,6 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 import static org.junit.Assert.*;
 

core-java-modules/core-java-string-apis/README.md

@@ -11,3 +11,4 @@ This module contains articles about string APIs.
 - [StringBuilder vs StringBuffer in Java](https://www.baeldung.com/java-string-builder-string-buffer)
 - [Generate a Secure Random Password in Java](https://www.baeldung.com/java-generate-secure-password)
 - [Getting a Character by Index From a String in Java](https://www.baeldung.com/java-character-at-position)
+- [Clearing a StringBuilder or StringBuffer](https://www.baeldung.com/java-clear-stringbuilder-stringbuffer)

core-java-modules/core-java-string-apis/src/main/java/com/baeldung/clearstringbuilderorstringbuffer/BenchmarkRunner.java

@@ -0,0 +1,32 @@
+package com.baeldung.clearstringbuilderorstringbuffer;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.infra.Blackhole;
+
+public class BenchmarkRunner {
+
+    public static void main(String[] args) throws Exception {
+        org.openjdk.jmh.Main.main(args);
+    }
+
+    @State(Scope.Benchmark)
+    public static class MyState {
+        final String HELLO = "Hello World";
+        final StringBuilder sb = new StringBuilder().append(HELLO);
+    }
+
+    @Benchmark
+    public void evaluateSetLength(Blackhole blackhole, MyState state) {
+        state.sb.setLength(0);
+        blackhole.consume(state.sb.toString());
+    }
+
+    @Benchmark
+    public void evaluateDelete(Blackhole blackhole, MyState state) {
+        state.sb.delete(0, state.sb.length());
+        blackhole.consume(state.sb.toString());
+    }
+
+}

core-java-modules/core-java-string-apis/src/test/java/com/baeldung/clearstringbuilderorstringbuffer/ClearStringBuilderOrStringBufferUnitTest.java

@@ -0,0 +1,66 @@
+package com.baeldung.clearstringbuilderorstringbuffer;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ClearStringBuilderOrStringBufferUnitTest {
+
+    @Test
+    void whenSetLengthToZero_ThenStringBuilderIsCleared() {
+        StringBuilder stringBuilder = new StringBuilder();
+        stringBuilder.append("Hello World");
+        int initialCapacity = stringBuilder.capacity();
+        stringBuilder.setLength(0);
+        assertEquals("", stringBuilder.toString());
+        assertEquals(initialCapacity, stringBuilder.capacity());
+    }
+
+    @Test
+    void whenDeleteAll_ThenStringBuilderIsCleared() {
+        StringBuilder stringBuilder = new StringBuilder();
+        stringBuilder.append("Hello World");
+        int initialCapacity = stringBuilder.capacity();
+        stringBuilder.delete(0, stringBuilder.length());
+        assertEquals("", stringBuilder.toString());
+        assertEquals(initialCapacity, stringBuilder.capacity());
+    }
+
+    @Test
+    void whenSetLengthToZero_ThenStringBufferIsCleared() {
+        StringBuffer stringBuffer = new StringBuffer();
+        stringBuffer.append("Hello World");
+        int initialCapacity = stringBuffer.capacity();
+        stringBuffer.setLength(0);
+        assertEquals("", stringBuffer.toString());
+        assertEquals(initialCapacity, stringBuffer.capacity());
+    }
+
+    @Test
+    void whenDeleteAll_ThenStringBufferIsCleared() {
+        StringBuffer stringBuffer = new StringBuffer();
+        stringBuffer.append("Hello World");
+        int initialCapacity = stringBuffer.capacity();
+        stringBuffer.delete(0, stringBuffer.length());
+        assertEquals("", stringBuffer.toString());
+        assertEquals(initialCapacity, stringBuffer.capacity());
+    }
+
+    // Note: It did not make the cut to the article, but here is another way to reset a StringBuilder
+    @Test
+    void whenAssignedToNewStringBuilder_ThenStringBuilderIsCleared() {
+        StringBuilder stringBuilder = new StringBuilder();
+        stringBuilder.append("Hello World");
+        stringBuilder = new StringBuilder();
+        assertEquals("", stringBuilder.toString());
+    }
+
+    @Test
+    void whenAssignedToNewStringBuffer_ThenStringBufferIsCleared() {
+        StringBuffer stringBuffer = new StringBuffer();
+        stringBuffer.append("Hello World");
+        stringBuffer = new StringBuffer();
+        assertEquals("", stringBuffer.toString());
+    }
+
+}

core-java-modules/core-java-string-operations-4/README.md

@@ -7,4 +7,4 @@
 - [String equals() Vs contentEquals() in Java](https://www.baeldung.com/java-string-equals-vs-contentequals)
 - [Check if a String Ends with a Certain Pattern in Java](https://www.baeldung.com/java-string-ends-pattern)
 - [Check if a Character is a Vowel in Java](https://www.baeldung.com/java-check-character-vowel)
-
+- [How to Truncate a String in Java](https://www.baeldung.com/java-truncating-strings)

core-java-modules/core-java-string-operations/src/test/java/com/baeldung/base64encodinganddecoding/Java8EncodeDecodeUnitTest.java

@@ -96,7 +96,23 @@ public class Java8EncodeDecodeUnitTest {
         assertNotNull(decodedMime);
     }
 
-    //
+    @Test
+    public void whenEncodedStringHasValidCharacters_thenStringCanBeDecoded() {
+        final String encodedString = "dGVzdCMkaW5wdXQ+";
+        final byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
+        final String decodedString = new String(decodedBytes);
+
+        assertNotNull(decodedString);
+    }
+    
+    @Test(expected = IllegalArgumentException.class)
+    public void whenEncodedStringHasInvalidCharacters_thenIllegalArgumentException() {
+        final String encodedString = "dGVzdCMkaW5wdXQ#";
+        final byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
+        final String decodedString = new String(decodedBytes);
+
+        assertNotNull(decodedString);
+    }
 
     private static StringBuilder getMimeBuffer() {
         final StringBuilder buffer = new StringBuilder();

docker-modules/docker-java-jar/Dockerfile

@@ -0,0 +1,4 @@
+FROM openjdk:11
+MAINTAINER baeldung.com
+COPY target/docker-java-jar-0.0.1-SNAPSHOT.jar app.jar
+ENTRYPOINT ["java","-jar","/app.jar"]

docker-modules/docker-java-jar/pom.xml

@@ -0,0 +1,37 @@
+<?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">
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>docker-java-jar</artifactId>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <version>${maven-jar-plugin.version}</version>
+                <configuration>
+                    <archive>
+                        <manifest>
+                            <mainClass>com.baeldung.HelloWorld</mainClass>
+                        </manifest>
+                    </archive>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

docker-modules/docker-java-jar/src/main/java/com/baeldung/HelloWorld.java

@@ -0,0 +1,8 @@
+package com.baeldung;
+
+public class HelloWorld {
+
+    public static void main(String[] args){
+        System.out.println("Welcome to our application");
+    }
+}

docker-modules/pom.xml

@@ -23,6 +23,7 @@
         <module>docker-images</module>
         <module>docker-spring-boot</module>
         <module>docker-spring-boot-postgres</module>
+        <module>docker-java-jar</module>
     </modules>
 
     <properties>

gradle-modules/README.md

@@ -0,0 +1,3 @@
+## Gradle Modules 
+
+This module contains submodules of Gradle. 

gradle-modules/gradle-5/settings.gradle

@@ -1,4 +1,4 @@
-rootProject.name='gradle-5-articles'
+rootProject.name='gradle-5'
 include 'java-exec'
 include 'unused-dependencies'
 include 'source-sets'