Merge pull request #1 from eugenp/master

Updating local ref

atomikos/pom.xml

@@ -51,7 +51,7 @@
 		</dependency>
 		<dependency>
 			<groupId>org.hibernate</groupId>
-			<artifactId>hibernate-entitymanager</artifactId>
+			<artifactId>hibernate-core</artifactId>
 			<version>${hibernate.version}</version>
 			<scope>provided</scope>
 			<exclusions>

aws-lambda/lambda/pom.xml

@@ -89,7 +89,6 @@
 
     <properties>
         <json-simple.version>1.1.1</json-simple.version>
-        <commons-io.version>2.5</commons-io.version>
         <aws-lambda-java-events.version>1.3.0</aws-lambda-java-events.version>
         <aws-lambda-java-core.version>1.2.0</aws-lambda-java-core.version>
         <gson.version>2.8.2</gson.version>

blade/pom.xml

@@ -154,7 +154,6 @@
     <properties>
         <blade-mvc.version>2.0.14.RELEASE</blade-mvc.version>
         <bootstrap.version>4.2.1</bootstrap.version>
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <lombok.version>1.18.4</lombok.version>
         <httpclient.version>4.5.6</httpclient.version>
         <httpmime.version>4.5.6</httpmime.version>

core-java-modules/core-java-10/README.md

@@ -5,7 +5,7 @@ This module contains articles about Java 10 core features
 ### Relevant Articles: 
 
 - [Java 10 LocalVariable Type-Inference](http://www.baeldung.com/java-10-local-variable-type-inference)
-- [Guide to Java 10](http://www.baeldung.com/java-10-overview)
+- [New Features in Java 10](https://www.baeldung.com/java-10-overview)
 - [Copy a List to Another List in Java](http://www.baeldung.com/java-copy-list-to-another)
 - [Deep Dive Into the New Java JIT Compiler – Graal](https://www.baeldung.com/graal-java-jit-compiler)
 - [Copying Sets in Java](https://www.baeldung.com/java-copy-sets)

core-java-modules/core-java-11-2/README.md

@@ -6,3 +6,4 @@ This module contains articles about Java 11 core features
 - [Guide to Java 8 Optional](https://www.baeldung.com/java-optional)
 - [Guide to Java Reflection](http://www.baeldung.com/java-reflection)
 - [Guide to Java 8’s Collectors](https://www.baeldung.com/java-8-collectors)
+- [New Features in Java 11](https://www.baeldung.com/java-11-new-features)

core-java-modules/core-java-11-2/pom.xml

@@ -28,6 +28,29 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mock-server</groupId>
+            <artifactId>mockserver-junit-jupiter</artifactId>
+            <version>${mockserver.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>${junit.jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <version>${junit.jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>${junit.jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
@@ -48,7 +71,9 @@
         <maven.compiler.source.version>11</maven.compiler.source.version>
         <maven.compiler.target.version>11</maven.compiler.target.version>
         <guava.version>29.0-jre</guava.version>
+        <junit.jupiter.version>5.7.0</junit.jupiter.version>
         <assertj.version>3.17.2</assertj.version>
+        <mockserver.version>5.11.1</mockserver.version>
     </properties>
 
 </project>

core-java-modules/core-java-11-2/src/main/java/com/baeldung/features/MainClass.java

@@ -0,0 +1,17 @@
+package com.baeldung.features;
+
+public class MainClass {
+
+    private static boolean mainPrivateMethod() {
+        return true;
+    }
+
+    public static class NestedClass {
+
+        boolean nestedPublicMethod() {
+            return mainPrivateMethod();
+        }
+
+    }
+
+}

core-java-modules/core-java-11-2/src/test/java/com/baeldung/features/HttpClientIntegrationTest.java

@@ -0,0 +1,54 @@
+package com.baeldung.features;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.mockserver.integration.ClientAndServer;
+import org.mockserver.model.HttpStatusCode;
+import org.mockserver.socket.PortFactory;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockserver.integration.ClientAndServer.startClientAndServer;
+
+class HttpClientIntegrationTest {
+
+    private static ClientAndServer mockServer;
+    private static int port;
+
+    @BeforeAll
+    static void startServer() {
+        port = PortFactory.findFreePort();
+        mockServer = startClientAndServer(port);
+        mockServer.when(new org.mockserver.model.HttpRequest().withMethod("GET"))
+          .respond(new org.mockserver.model.HttpResponse()
+            .withStatusCode(HttpStatusCode.OK_200.code())
+            .withBody("Hello from the server!"));
+    }
+
+    @AfterAll
+    static void stopServer() {
+        mockServer.stop();
+    }
+
+    @Test
+    void givenSampleHttpRequest_whenRequestIsSent_thenServerResponseIsReceived() throws IOException, InterruptedException {
+        HttpClient httpClient = HttpClient.newBuilder()
+          .version(HttpClient.Version.HTTP_2)
+          .connectTimeout(Duration.ofSeconds(20))
+          .build();
+        HttpRequest httpRequest = HttpRequest.newBuilder()
+          .GET()
+          .uri(URI.create("http://localhost:" + port))
+          .build();
+        HttpResponse<String> httpResponse = httpClient.send(httpRequest, HttpResponse.BodyHandlers.ofString());
+        assertThat(httpResponse.body()).isEqualTo("Hello from the server!");
+    }
+
+}

core-java-modules/core-java-11-2/src/test/java/com/baeldung/features/JavaElevenFeaturesUnitTest.java

@@ -0,0 +1,61 @@
+package com.baeldung.features;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import javax.annotation.Nonnull;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class JavaElevenFeaturesUnitTest {
+
+    @Test
+    void givenMultilineString_whenExtractingNonBlankStrippedLines_thenLinesAreReturned() {
+        String multilineString = "Baeldung helps \n \n developers \n explore Java.";
+        List<String> lines = multilineString.lines()
+          .filter(line -> !line.isBlank())
+          .map(String::strip)
+          .collect(Collectors.toList());
+        assertThat(lines).containsExactly("Baeldung helps", "developers", "explore Java.");
+    }
+
+    @Test
+    void givenTemporaryFile_whenReadingStringContent_thenContentIsReturned(@TempDir Path tempDir) throws IOException {
+        Path filePath = Files.writeString(Files.createTempFile(tempDir, "demo", ".txt"), "Sample text");
+        String fileContent = Files.readString(filePath);
+        assertThat(fileContent).isEqualTo("Sample text");
+    }
+
+    @Test
+    void givenSampleList_whenConvertingToArray_thenItemsRemainUnchanged() {
+        List<String> sampleList = Arrays.asList("Java", "Kotlin");
+        String[] sampleArray = sampleList.toArray(String[]::new);
+        assertThat(sampleArray).containsExactly("Java", "Kotlin");
+    }
+
+    @Test
+    void givenSampleList_whenConvertingToUppercaseString_thenUppercaseIsReturned() {
+        List<String> sampleList = Arrays.asList("Java", "Kotlin");
+        String resultString = sampleList.stream()
+          .map((@Nonnull var x) -> x.toUpperCase())
+          .collect(Collectors.joining(", "));
+        assertThat(resultString).isEqualTo("JAVA, KOTLIN");
+    }
+
+    @Test
+    void givenSampleList_whenExtractingNonBlankValues_thenOnlyNonBlanksAreReturned() {
+        List<String> sampleList = Arrays.asList("Java", "\n \n", "Kotlin", " ");
+        List<String> withoutBlanks = sampleList.stream()
+          .filter(Predicate.not(String::isBlank))
+          .collect(Collectors.toList());
+        assertThat(withoutBlanks).containsExactly("Java", "Kotlin");
+    }
+
+}

core-java-modules/core-java-11-2/src/test/java/com/baeldung/features/NestedClassesUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.features;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class NestedClassesUnitTest {
+
+    @Test
+    public void giveNestedClass_whenCallingMainClassPrivateMethod_thenNoExceptionIsThrown() {
+        MainClass.NestedClass nestedInstance = new MainClass.NestedClass();
+        assertThat(nestedInstance.nestedPublicMethod()).isTrue();
+    }
+
+    @Test
+    public void giveNestedClass_whenCheckingNestmate_thenNestedClassIsReturned() {
+        assertThat(MainClass.class.isNestmateOf(MainClass.NestedClass.class)).isTrue();
+    }
+
+    @Test
+    public void giveNestedClass_whenCheckingNestHost_thenMainClassIsReturned() {
+        assertThat(MainClass.NestedClass.class.getNestHost()).isEqualTo(MainClass.class);
+    }
+
+    @Test
+    public void giveNestedClass_whenCheckingNestMembers_thenNestMembersAreReturned() {
+        Set<String> nestedMembers = Arrays.stream(MainClass.NestedClass.class.getNestMembers())
+          .map(Class::getName)
+          .collect(Collectors.toSet());
+        assertThat(nestedMembers).contains(MainClass.class.getName(), MainClass.NestedClass.class.getName());
+    }
+
+}

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpClientUnitTest.java

@@ -64,7 +64,7 @@ public class HttpClientUnitTest {
             .send(request, HttpResponse.BodyHandlers.ofString());
 
         assertThat(response.statusCode(), equalTo(HttpURLConnection.HTTP_MOVED_PERM));
-        assertThat(response.body(), containsString("https://stackoverflow.com/"));
+        assertTrue(response.headers().map().get("location").stream().anyMatch("https://stackoverflow.com/"::equals));
     }
 
     @Test

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpRequestUnitTest.java

@@ -18,6 +18,7 @@ import java.security.NoSuchAlgorithmException;
 import java.time.Duration;
 
 import org.junit.Test;
+import org.junit.jupiter.api.Disabled;
 
 public class HttpRequestUnitTest {
 
@@ -48,7 +49,12 @@ public class HttpRequestUnitTest {
         assertThat(response.version(), equalTo(HttpClient.Version.HTTP_2));
     }
 
-    @Test
+    /*
+    * This test will fail as soon as the given URL returns a HTTP 2 response.
+    * Therefore, let's leave it commented out.
+    * */
+   @Test
+   @Disabled
     public void shouldFallbackToHttp1_1WhenWebsiteDoesNotUseHttp2() throws IOException, InterruptedException, URISyntaxException, NoSuchAlgorithmException {
         HttpRequest request = HttpRequest.newBuilder()
             .uri(new URI("https://postman-echo.com/get"))

core-java-modules/core-java-12/README.md

@@ -1,4 +1,4 @@
 ## Relevant Articles:
 
-
 - [String API Updates in Java 12](https://www.baeldung.com/java12-string-api)
+- [New Features in Java 12](https://www.baeldung.com/java-12-new-features)

core-java-modules/core-java-12/src/test/java/com/baeldung/newfeatures/CompactNumbersUnitTest.java

@@ -0,0 +1,21 @@
+package java.com.baeldung.newfeatures;
+
+import org.junit.Test;
+
+import java.text.NumberFormat;
+import java.util.Locale;
+
+import static org.junit.Assert.assertEquals;
+
+public class CompactNumbersUnitTest {
+
+    @Test
+    public void givenNumber_thenCompactValues() {
+        NumberFormat likesShort = NumberFormat.getCompactNumberInstance(new Locale("en", "US"), NumberFormat.Style.SHORT);
+        likesShort.setMaximumFractionDigits(2);
+        assertEquals("2.59K", likesShort.format(2592));
+        NumberFormat likesLong = NumberFormat.getCompactNumberInstance(new Locale("en", "US"), NumberFormat.Style.LONG);
+        likesLong.setMaximumFractionDigits(2);
+        assertEquals("2.59 thousand", likesShort.format(2592));
+    }
+}

core-java-modules/core-java-12/src/test/java/com/baeldung/newfeatures/FileMismatchUnitTest.java

@@ -0,0 +1,32 @@
+package java.com.baeldung.newfeatures;
+
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.Assert.assertEquals;
+
+public class FileMismatchUnitTest {
+
+    @Test
+    public void givenIdenticalFiles_thenShouldNotFindMismatch() throws IOException {
+        Path filePath1 = Files.createTempFile("file1", ".txt");
+        Path filePath2 = Files.createTempFile("file2", ".txt");
+        Files.writeString(filePath1, "Java 12 Article");
+        Files.writeString(filePath2, "Java 12 Article");
+        long mismatch = Files.mismatch(filePath1, filePath2);
+        assertEquals(-1, mismatch);
+    }
+
+    @Test
+    public void givenDifferentFiles_thenShouldFindMismatch() throws IOException {
+        Path filePath3 = Files.createTempFile("file3", ".txt");
+        Path filePath4 = Files.createTempFile("file4", ".txt");
+        Files.writeString(filePath3, "Java 12 Article");
+        Files.writeString(filePath4, "Java 12 Tutorial");
+        long mismatch = Files.mismatch(filePath3, filePath4);
+        assertEquals(8, mismatch);
+    }
+}

core-java-modules/core-java-12/src/test/java/com/baeldung/newfeatures/StringUnitTest.java

@@ -0,0 +1,15 @@
+package java.com.baeldung.newfeatures;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class StringUnitTest {
+
+    @Test
+    public void givenString_thenRevertValue() {
+        String text = "Baeldung";
+        String transformed = text.transform(value -> new StringBuilder(value).reverse().toString());
+        assertEquals("gnudleaB", transformed);
+    }
+}

core-java-modules/core-java-12/src/test/java/com/baeldung/newfeatures/TeeingCollectorUnitTest.java

@@ -0,0 +1,18 @@
+package java.com.baeldung.newfeatures;
+
+import org.junit.Test;
+
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+
+public class TeeingCollectorUnitTest {
+
+    @Test
+    public void givenSetOfNumbers_thenCalculateAverage() {
+        double mean = Stream.of(1, 2, 3, 4, 5)
+          .collect(Collectors.teeing(Collectors.summingDouble(i -> i), Collectors.counting(), (sum, count) -> sum / count));
+        assertEquals(3.0, mean);
+    }
+}

core-java-modules/core-java-13/README.md

@@ -1,4 +1,4 @@
 ### Relevant articles:
 
 - [Java Switch Statement](https://www.baeldung.com/java-switch)
-- [New Java 13 Features](https://www.baeldung.com/java-13-new-features)
+- [New Features in Java 13](https://www.baeldung.com/java-13-new-features)

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

@@ -10,3 +10,4 @@ This module contains articles about Java 14.
 - [Helpful NullPointerExceptions in Java 14](https://www.baeldung.com/java-14-nullpointerexception)
 - [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)

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

@@ -44,6 +44,8 @@
                 <configuration>
                     <release>${maven.compiler.release}</release>
                     <compilerArgs>--enable-preview</compilerArgs>
+                    <source>14</source>
+                    <target>14</target>
                 </configuration>
             </plugin>
             <plugin>

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/newfeatues/MultilineUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.java14.newfeatues;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class MultilineUnitTest {
+    
+    @SuppressWarnings("preview")
+    String multiline = """ 
+            A quick brown fox jumps over a lazy dog; \
+         the lazy dog howls loudly.""";
+    
+    @SuppressWarnings("preview")
+    String anotherMultiline = """ 
+            A quick brown fox jumps over a lazy dog; 
+         the lazy dog howls loudly.""";
+    
+    @Test
+    public void givenMultilineString_whenSlashUsed_thenNoNewLine() {
+        assertFalse(multiline.contains("\n"));
+        assertTrue(anotherMultiline.contains("\n"));
+    }
+
+}

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/newfeatues/RecordUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.java14.newfeatues;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class RecordUnitTest {
+
+    @SuppressWarnings("preview") 
+    public record User(int id, String password) {
+    };
+
+    private User user1 = new User(0, "UserOne");
+
+    @Test
+    public void givenRecord_whenObjInitialized_thenValuesCanBeFetchedWithGetters() {
+
+        assertEquals(0, user1.id());
+        assertEquals("UserOne", user1.password());
+    }
+
+    @Test
+    public void whenRecord_thenEqualsImplemented() {
+
+        User user2 = user1;
+
+        assertEquals(user1, user2);
+    }
+
+    @Test
+    public void whenRecord_thenToStringImplemented() {
+
+        assertTrue(user1.toString()
+            .contains("UserOne"));
+    }
+
+}

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/newfeatues/SwitchExprUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.java14.newfeatues;
+
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class SwitchExprUnitTest {
+
+    @Test
+    public void givenDay_whenSunday_thenWeekend() {
+        assertTrue(isTodayHolidayInJava8("SUNDAY"));
+
+        assertTrue(isTodayHolidayInJava14("SUNDAY"));
+
+        assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> isTodayHolidayInJava8("SOMEDAY"));
+
+        assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> isTodayHolidayInJava14("SOMEDAY"));
+    }
+
+    private boolean isTodayHolidayInJava8(String day) {
+
+        boolean isTodayHoliday;
+        switch (day) {
+            case "MONDAY":
+            case "TUESDAY":
+            case "WEDNESDAY":
+            case "THURSDAY":
+            case "FRIDAY":
+                isTodayHoliday = false;
+                break;
+            case "SATURDAY":
+            case "SUNDAY":
+                isTodayHoliday = true;
+                break;
+            default:
+                throw new IllegalArgumentException("What's a " + day);
+        }
+        return isTodayHoliday;
+    }
+
+    private boolean isTodayHolidayInJava14(String day) {
+        return switch (day) {
+            case "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY" -> false;
+            case "SATURDAY", "SUNDAY" -> true;
+            default -> throw new IllegalArgumentException("What's a " + day);
+        };
+    }
+
+}

core-java-modules/core-java-15/pom.xml

@@ -20,7 +20,7 @@
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
-            <version>${apache-commons-lang3.version}</version>
+            <version>${commons-lang3.version}</version>
         </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
@@ -68,7 +68,6 @@
 
     <properties>
         <maven.compiler.release>15</maven.compiler.release>
-        <apache-commons-lang3.version>3.11</apache-commons-lang3.version>
         <assertj.version>3.17.2</assertj.version>
         <maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
         <surefire.plugin.version>3.0.0-M3</surefire.plugin.version>

core-java-modules/core-java-9-jigsaw/src/test/java/com/baeldung/java9/modules/ModuleAPIUnitTest.java

@@ -2,8 +2,7 @@ package com.baeldung.java9.modules;
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.nullValue;
-import static org.hamcrest.Matchers.contains;
-import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.hamcrest.Matchers.*;
 import static org.hamcrest.collection.IsEmptyCollection.empty;
 import static org.junit.Assert.*;
 
@@ -74,7 +73,6 @@ public class ModuleAPIUnitTest {
         ModuleLayer javaBaseModuleLayer = javaBaseModule.getLayer();
 
         assertTrue(javaBaseModuleLayer.configuration().findModule(JAVA_BASE_MODULE_NAME).isPresent());
-        assertThat(javaBaseModuleLayer.configuration().modules().size(), is(78));
         assertTrue(javaBaseModuleLayer.parents().get(0).configuration().parents().isEmpty());
     }
 
@@ -108,8 +106,7 @@ public class ModuleAPIUnitTest {
           .collect(Collectors.toSet());
 
         assertThat(javaBaseRequires, empty());
-        assertThat(javaSqlRequires.size(), is(3));
-        assertThat(javaSqlRequiresNames, containsInAnyOrder("java.base", "java.xml", "java.logging"));
+        assertThat(javaSqlRequiresNames, hasItems("java.base", "java.xml", "java.logging"));
     }
 
     @Test
@@ -127,16 +124,13 @@ public class ModuleAPIUnitTest {
 
     @Test
     public void givenModules_whenAccessingModuleDescriptorExports_thenExportsAreReturned() {
-        Set<Exports> javaBaseExports = javaBaseModule.getDescriptor().exports();
         Set<Exports> javaSqlExports = javaSqlModule.getDescriptor().exports();
 
         Set<String> javaSqlExportsSource = javaSqlExports.stream()
           .map(Exports::source)
           .collect(Collectors.toSet());
 
-        assertThat(javaBaseExports.size(), is(108));
-        assertThat(javaSqlExports.size(), is(3));
-        assertThat(javaSqlExportsSource, containsInAnyOrder("java.sql", "javax.transaction.xa", "javax.sql"));
+        assertThat(javaSqlExportsSource, hasItems("java.sql",  "javax.sql"));
     }
 
     @Test
@@ -144,7 +138,6 @@ public class ModuleAPIUnitTest {
         Set<String> javaBaseUses = javaBaseModule.getDescriptor().uses();
         Set<String> javaSqlUses = javaSqlModule.getDescriptor().uses();
 
-        assertThat(javaBaseUses.size(), is(34));
         assertThat(javaSqlUses, contains("java.sql.Driver"));
     }
 

core-java-modules/core-java-9-new-features/README.md

@@ -4,7 +4,7 @@ This module contains articles about core Java features that have been introduced
 
 ### Relevant Articles:
 
-- [Java 9 New Features](https://www.baeldung.com/new-java-9)
+- [New Features in Java 9](https://www.baeldung.com/new-java-9)
 - [Java 9 Variable Handles Demystified](http://www.baeldung.com/java-variable-handles)
 - [Exploring the New HTTP Client in Java 9 and 11](http://www.baeldung.com/java-9-http-client)
 - [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)

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

@@ -47,12 +47,12 @@
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
-            <version>3.11</version>
+            <version>${commons-lang3.version}</version>
         </dependency>
         <dependency>
             <groupId>commons-io</groupId>
             <artifactId>commons-io</artifactId>
-            <version>2.7</version>
+            <version>${commons-io.version}</version>
         </dependency>
     </dependencies>
 

core-java-modules/core-java-arrays-operations-advanced/pom.xml

@@ -29,8 +29,6 @@
     </dependencies>
 
     <properties>
-        <commons-lang3.version>3.9</commons-lang3.version>
-
         <assertj-core.version>3.10.0</assertj-core.version>
     </properties>
 </project>

core-java-modules/core-java-arrays-operations-basic/pom.xml

@@ -68,11 +68,7 @@
 
     <properties>
         <shade.plugin.version>3.2.0</shade.plugin.version>
-
-        <commons-lang3.version>3.9</commons-lang3.version>
-
         <jmh.version>1.19</jmh.version>
-
         <assertj-core.version>3.10.0</assertj-core.version>
     </properties>
 </project>

core-java-modules/core-java-arrays-sorting/pom.xml

@@ -76,12 +76,8 @@
 
     <properties>
         <shade.plugin.version>3.2.0</shade.plugin.version>
-
-        <commons-lang3.version>3.9</commons-lang3.version>
         <guava.version>28.2-jre</guava.version>
-
         <jmh.version>1.19</jmh.version>
-
         <assertj-core.version>3.10.0</assertj-core.version>
     </properties>
 </project>

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

@@ -3,4 +3,4 @@
 This module contains articles about Java Character Class
 
 ### Relevant Articles: 
-- Character#isAlphabetic vs Character#isLetter
+- [Character#isAlphabetic vs. Character#isLetter](https://www.baeldung.com/java-character-isletter-isalphabetic)

core-java-modules/core-java-char/src/test/java/com/baeldung/character/CharacterGeneralCategoryTypeUnitTest.java

@@ -3,35 +3,36 @@ package com.baeldung.character;
 import org.junit.Test;
 
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
 
 public class CharacterGeneralCategoryTypeUnitTest {
     @Test
     public void givenACharacter_whenUpperCaseLetter_thenAssertTrue() {
-        assertTrue(Character.getType('U') == Character.UPPERCASE_LETTER);
+        assertEquals(Character.UPPERCASE_LETTER, Character.getType('U'));
     }
 
     @Test
     public void givenACharacter_whenLowerCaseLetter_thenAssertTrue() {
-        assertTrue(Character.getType('u') == Character.LOWERCASE_LETTER);
+        assertEquals(Character.LOWERCASE_LETTER, Character.getType('u'));
     }
 
     @Test
     public void givenACharacter_whenTitleCaseLetter_thenAssertTrue() {
-        assertTrue(Character.getType('\u01f2') == Character.TITLECASE_LETTER);
+        assertEquals(Character.TITLECASE_LETTER, Character.getType('\u01f2'));
     }
 
     @Test
     public void givenACharacter_whenModifierLetter_thenAssertTrue() {
-        assertTrue(Character.getType('\u02b0') == Character.MODIFIER_LETTER);
+        assertEquals(Character.MODIFIER_LETTER, Character.getType('\u02b0'));
     }
 
     @Test
     public void givenACharacter_whenOtherLetter_thenAssertTrue() {
-        assertTrue(Character.getType('\u05d0') == Character.OTHER_LETTER);
+        assertEquals(Character.OTHER_LETTER, Character.getType('\u05d0'));
     }
 
     @Test
     public void givenACharacter_whenLetterNumber_thenAssertTrue() {
-        assertTrue(Character.getType('\u2164') == Character.LETTER_NUMBER);
+        assertEquals(Character.LETTER_NUMBER, Character.getType('\u2164'));
     }
 }

core-java-modules/core-java-char/src/test/java/com/baeldung/character/IsLetterOrAlphabetUnitTest.java

@@ -6,6 +6,27 @@ import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.assertFalse;
 
 public class IsLetterOrAlphabetUnitTest {
+
+    @Test
+    public void givenACharacter_whenUpperCaseLetter_thenAssertIsAlphabeticTrue() {
+        assertTrue(Character.isAlphabetic('A'));
+    }
+
+    @Test
+    public void givenACharacter_whenTitleCaseLetter_thenAssertIsAlphabeticTrue() {
+        assertTrue(Character.isAlphabetic('\u01f2'));
+    }
+
+    @Test
+    public void givenACharacter_whenLowerCaseLetter_thenAssertIsLetterTrue() {
+        assertTrue(Character.isAlphabetic('a'));
+    }
+
+    @Test
+    public void givenACharacter_whenModifierLetter_thenAssertIsLetterTrue() {
+        assertTrue(Character.isAlphabetic('\u02b0'));
+    }
+
     @Test
     public void givenACharacter_whenLetter_thenAssertIsLetterTrue() {
         assertTrue(Character.isLetter('a'));

core-java-modules/core-java-collections-3/pom.xml

@@ -35,7 +35,7 @@
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
-            <version>3.10</version>
+            <version>${commons-lang3.version}</version>
         </dependency>
     </dependencies>
 

core-java-modules/core-java-collections-4/README.md

@@ -0,0 +1,7 @@
+=========
+
+## Core Java Collections Cookbooks and Examples
+
+### Relevant Articles: 
+
+- [ArrayList vs. LinkedList vs. HashMap in Java](https://www.baeldung.com/java-arraylist-vs-linkedlist-vs-hashmap)

core-java-modules/core-java-collections-4/pom.xml

@@ -0,0 +1,31 @@
+<?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-collections-4</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-collections-4</name>
+    <packaging>jar</packaging>
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <assertj.version>3.18.0</assertj.version>
+    </properties>
+
+</project>

core-java-modules/core-java-collections-4/src/test/java/com/baeldung/collections/comparation/ArrayListUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.collections.comparation;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ArrayListUnitTest {
+
+    @Test
+    void givenArrayList_whenItemAddedToSpecificIndex_thenItCanBeRetrieved() {
+        List<String> list = new ArrayList<>();
+        list.add("Daniel");
+        list.add(0, "Marko");
+        assertThat(list).hasSize(2);
+        assertThat(list.get(0)).isEqualTo("Marko");
+    }
+
+    @Test
+    void givenArrayList_whenItemRemovedViaIndex_thenListSizeIsReduced() {
+        List<String> list = new ArrayList<>(Arrays.asList("Daniel", "Marko"));
+        list.remove(1);
+        assertThat(list).hasSize(1);
+        assertThat(list).doesNotContain("Marko");
+    }
+
+}

core-java-modules/core-java-collections-4/src/test/java/com/baeldung/collections/comparation/HashMapUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.collections.comparation;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class HashMapUnitTest {
+
+    @Test
+    void givenHashMap_whenItemAddedByKey_thenItCanBeRetrieved() {
+        Map<String, String> map = new HashMap<>();
+        map.put("123456", "Daniel");
+        map.put("654321", "Marko");
+        assertThat(map.get("654321")).isEqualTo("Marko");
+    }
+
+    @Test
+    void givenHashMap_whenItemRemovedByKey_thenMapSizeIsReduced() {
+        Map<String, String> map = new HashMap<>();
+        map.put("123456", "Daniel");
+        map.put("654321", "Marko");
+        map.remove("654321");
+        assertThat(map).hasSize(1);
+    }
+
+}

core-java-modules/core-java-collections-4/src/test/java/com/baeldung/collections/comparation/LinkedListUnitTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.collections.comparation;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class LinkedListUnitTest {
+
+    @Test
+    void givenLinkedList_whenItemIsAppended_thenItCanBeRetrieved() {
+        LinkedList<String> list = new LinkedList<>();
+        list.addLast("Daniel");
+        list.addFirst("Marko");
+        assertThat(list).hasSize(2);
+        assertThat(list.getLast()).isEqualTo("Daniel");
+    }
+
+    @Test
+    void givenLinkedList_whenItemIsRemoved_thenListSizeIsReduced() {
+        LinkedList<String> list = new LinkedList<>(Arrays.asList("Daniel", "Marko", "David"));
+        list.removeFirst();
+        list.removeLast();
+        assertThat(list).hasSize(1);
+        assertThat(list).containsExactly("Marko");
+    }
+
+    @Test
+    void givenLinkedList_whenItemInserted_thenItCanBeRetrievedAndDeleted() {
+        LinkedList<String> list = new LinkedList<>();
+        list.push("Daniel");
+        list.push("Marko");
+        assertThat(list.poll()).isEqualTo("Marko");
+        assertThat(list).hasSize(1);
+    }
+
+}

core-java-modules/core-java-collections-4/src/test/java/com/baeldung/collections/comparation/ListVsMapUnitTest.java

@@ -0,0 +1,32 @@
+package com.baeldung.collections.comparation;
+
+import static org.assertj.core.api.Assertions.*;
+import org.junit.jupiter.api.Test;
+
+import java.util.*;
+
+class ListVsMapUnitTest {
+
+    @Test
+    void givenList_whenIteratingTroughValues_thenEachValueIsPresent() {
+        List<String> list = new ArrayList<>();
+        list.add("Daniel");
+        list.add("Marko");
+        for (String name : list) {
+            assertThat(name).isIn(list);
+        }
+        assertThat(list).containsExactly("Daniel", "Marko");
+    }
+
+    @Test
+    void givenMap_whenIteratingTroughValues_thenEachValueIsPresent() {
+        Map<Integer, String> map = new HashMap<>();
+        map.put(1, "Daniel");
+        map.put(2, "Marko");
+        for (String name : map.values()) {
+            assertThat(name).isIn(map.values());
+        }
+        assertThat(map.values()).containsExactlyInAnyOrder("Daniel", "Marko");
+    }
+
+}

core-java-modules/core-java-collections-list/pom.xml

@@ -36,7 +36,6 @@
 
     <properties>
         <commons-collections4.version>4.1</commons-collections4.version>
-        <commons-lang3.version>3.8.1</commons-lang3.version>
         <assertj.version>3.11.1</assertj.version>
     </properties>
 

core-java-modules/core-java-collections-maps-2/src/main/java/com/baeldung/map/Product.java

@@ -26,7 +26,7 @@ public class Product {
         return tags;
     }
 
-    public Product addTagsOfOtherProdcut(Product product) {
+    public Product addTagsOfOtherProduct(Product product) {
         this.tags.addAll(product.getTags());
         return this;
     }
@@ -100,11 +100,11 @@ public class Product {
         HashMap<String, Product> productsByName = new HashMap<>();
         Product eBike2 = new Product("E-Bike", "A bike with a battery");
         eBike2.getTags().add("sport");
-        productsByName.merge("E-Bike", eBike2, Product::addTagsOfOtherProdcut);
+        productsByName.merge("E-Bike", eBike2, Product::addTagsOfOtherProduct);
 
         //Prior to Java 8:
         if(productsByName.containsKey("E-Bike")) {
-            productsByName.get("E-Bike").addTagsOfOtherProdcut(eBike2);
+            productsByName.get("E-Bike").addTagsOfOtherProduct(eBike2);
         } else {
             productsByName.put("E-Bike", eBike2);
         }
@@ -117,7 +117,7 @@ public class Product {
 
         productsByName.compute("E-Bike", (k,v) -> {
             if(v != null) {
-                return v.addTagsOfOtherProdcut(eBike2);
+                return v.addTagsOfOtherProduct(eBike2);
             } else {
                 return eBike2;
             }
@@ -125,7 +125,7 @@ public class Product {
 
         //Prior to Java 8:
         if(productsByName.containsKey("E-Bike")) {
-            productsByName.get("E-Bike").addTagsOfOtherProdcut(eBike2);
+            productsByName.get("E-Bike").addTagsOfOtherProduct(eBike2);
         } else {
             productsByName.put("E-Bike", eBike2);
         }

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

@@ -6,4 +6,5 @@ This module contains articles about Map data structures in Java.
 - [Java TreeMap vs HashMap](https://www.baeldung.com/java-treemap-vs-hashmap)
 - [Comparing Two HashMaps in Java](https://www.baeldung.com/java-compare-hashmaps)
 - [The Map.computeIfAbsent() Method](https://www.baeldung.com/java-map-computeifabsent)
+- [Collections.synchronizedMap vs. ConcurrentHashMap](https://www.baeldung.com/java-synchronizedmap-vs-concurrenthashmap)
 - More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-2)

core-java-modules/core-java-collections-maps-3/pom.xml

@@ -15,7 +15,16 @@
     </parent>
 
     <dependencies>
-        
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>

core-java-modules/core-java-collections-maps-3/src/main/java/com/baeldung/map/concurrenthashmap/MapPerformanceComparison.java

@@ -0,0 +1,96 @@
+package com.baeldung.map.concurrenthashmap;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Threads;
+import org.openjdk.jmh.annotations.Warmup;
+
+@Fork(5)
+@Threads(10)
+@Warmup(iterations = 5)
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+public class MapPerformanceComparison {
+    
+    private int TEST_NO_ITEMS;
+    
+    public static void main(String[] args) throws Exception {
+        org.openjdk.jmh.Main.main(args);
+    }
+    
+    @Setup
+    public void setup() {
+        TEST_NO_ITEMS = 1000;
+    }
+    
+    @Benchmark
+    public void randomReadAndWriteSynchronizedMap() {
+        Map<String, Integer> map = Collections.synchronizedMap(new HashMap<String, Integer>());
+        performReadAndWriteTest(map);
+    }
+    
+    @Benchmark
+    public void randomReadAndWriteConcurrentHashMap() {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+        performReadAndWriteTest(map);
+    }
+    
+    private void performReadAndWriteTest(final Map<String, Integer> map) {
+        for (int i = 0; i < TEST_NO_ITEMS; i++) {
+            Integer randNumber = (int) Math.ceil(Math.random() * TEST_NO_ITEMS);
+            map.get(String.valueOf(randNumber));
+            map.put(String.valueOf(randNumber), randNumber);
+        }
+    }
+    
+    @Benchmark
+    public void randomWriteSynchronizedMap() {
+        Map<String, Integer> map = Collections.synchronizedMap(new HashMap<String, Integer>());
+        performWriteTest(map);
+    }
+    
+    @Benchmark
+    public void randomWriteConcurrentHashMap() {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+        performWriteTest(map);
+    }
+    
+    private void performWriteTest(final Map<String, Integer> map) {
+        for (int i = 0; i < TEST_NO_ITEMS; i++) {
+            Integer randNumber = (int) Math.ceil(Math.random() * TEST_NO_ITEMS);
+            map.put(String.valueOf(randNumber), randNumber);
+        }
+    }
+    
+    @Benchmark
+    public void randomReadSynchronizedMap() {
+        Map<String, Integer> map = Collections.synchronizedMap(new HashMap<String, Integer>());
+        performReadTest(map);
+    }
+    
+    @Benchmark
+    public void randomReadConcurrentHashMap() {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+        performReadTest(map);
+    }
+    
+    private void performReadTest(final Map<String, Integer> map) {
+        for (int i = 0; i < TEST_NO_ITEMS; i++) {
+            Integer randNumber = (int) Math.ceil(Math.random() * TEST_NO_ITEMS);
+            map.get(String.valueOf(randNumber));
+        }
+    }
+}

core-java-modules/core-java-collections-maps-3/src/main/java/com/baeldung/map/propertieshashmap/PropertiesToHashMapConverter.java

@@ -0,0 +1,39 @@
+package com.baeldung.map.propertieshashmap;
+
+import com.google.common.collect.Maps;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import java.util.stream.Collectors;
+
+public class PropertiesToHashMapConverter {
+
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public static HashMap<String, String> typeCastConvert(Properties prop) {
+        Map step1 = prop;
+        Map<String, String> step2 = (Map<String, String>) step1;
+        return new HashMap<>(step2);
+    }
+
+    public static HashMap<String, String> loopConvert(Properties prop) {
+        HashMap<String, String> retMap = new HashMap<>();
+        for (Map.Entry<Object, Object> entry : prop.entrySet()) {
+            retMap.put(String.valueOf(entry.getKey()), String.valueOf(entry.getValue()));
+        }
+        return retMap;
+    }
+
+    public static HashMap<String, String> streamConvert(Properties prop) {
+        return prop.entrySet().stream().collect(
+                Collectors.toMap(
+                  e -> String.valueOf(e.getKey()),
+                  e -> String.valueOf(e.getValue()),
+                  (prev, next) -> next, HashMap::new
+                ));
+    }
+
+    public static HashMap<String, String> guavaConvert(Properties prop) {
+        return Maps.newHashMap(Maps.fromProperties(prop));
+    }
+}

core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/ConcurrentModificationErrorUnitTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.map.concurrenthashmap;
+
+import java.util.Collections;
+import java.util.ConcurrentModificationException;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.TreeMap;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ConcurrentModificationErrorUnitTest {
+
+    @Test(expected = ConcurrentModificationException.class)
+    public void whenRemoveAndAddOnHashMap_thenConcurrentModificationError() {
+        Map<Integer, String> map = new HashMap<>();
+        map.put(1, "baeldung");
+        map.put(2, "HashMap");
+        Map<Integer, String> synchronizedMap = Collections.synchronizedMap(map);
+        Iterator<Entry<Integer, String>> iterator = synchronizedMap.entrySet().iterator();
+        while (iterator.hasNext()) {
+            synchronizedMap.put(3, "Modification");
+            iterator.next();
+        }
+    }
+    
+    @Test(expected = ConcurrentModificationException.class)
+    public void whenRemoveAndAddOnTreeMap_thenConcurrentModificationError() {
+        Map<Integer, String> map = new TreeMap<>();
+        map.put(1, "baeldung");
+        map.put(2, "HashMap");
+        Map<Integer, String> synchronizedMap = Collections.synchronizedMap(map);
+        Iterator<Entry<Integer, String>> iterator = synchronizedMap.entrySet().iterator();
+        while (iterator.hasNext()) {
+            synchronizedMap.put(3, "Modification");
+            iterator.next();
+        }
+    }
+    
+    @Test(expected = ConcurrentModificationException.class)
+    public void whenRemoveAndAddOnLinkedHashMap_thenConcurrentModificationError() {
+        Map<Integer, String> map = new LinkedHashMap<>();
+        map.put(1, "baeldung");
+        map.put(2, "HashMap");
+        Map<Integer, String> synchronizedMap = Collections.synchronizedMap(map);
+        Iterator<Entry<Integer, String>> iterator = synchronizedMap.entrySet().iterator();
+        while (iterator.hasNext()) {
+            synchronizedMap.put(3, "Modification");
+            iterator.next();
+        }
+    }
+
+    @Test
+    public void whenRemoveAndAddOnConcurrentHashMap_thenNoError() {
+        Map<Integer, String> map = new ConcurrentHashMap<>();
+        map.put(1, "baeldung");
+        map.put(2, "HashMap");
+        Iterator<Entry<Integer, String>> iterator = map.entrySet().iterator();
+        while (iterator.hasNext()) {
+            map.put(3, "Modification");
+            iterator.next();
+        }
+
+        Assert.assertEquals(3, map.size());
+    }
+}

core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/NullAllowInMapUnitTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.map.concurrenthashmap;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class NullAllowInMapUnitTest {
+
+    @Test
+    public void givenHashMapBackedSynchronizedMap_whenNullAsKey_thenNoError() {
+        Map<String, Integer> map = Collections
+                .synchronizedMap(new HashMap<String, Integer>());
+        map.put(null, 1);
+        Assert.assertTrue(map.get(null).equals(1));
+    }
+
+
+    @Test(expected = NullPointerException.class)
+    public void givenTreeMapBackedSynchronizedMap_whenNullAsKey_thenException() {
+        Map<String, Integer> map = Collections.synchronizedMap(new TreeMap<String, Integer>());
+        map.put(null, 1);
+        Assert.assertTrue(map.get(null).equals(1));
+    }
+    
+    @Test
+    public void givenLinkedHashMapBackedSynchronizedMap_whenNullAsKey_thenNoError() {
+        Map<String, Integer> map = Collections
+                .synchronizedMap(new LinkedHashMap<String, Integer>());
+        map.put(null, 1);
+        Assert.assertTrue(map.get(null).equals(1));
+    }
+    
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHasMap_whenNullAsKey_thenException() {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+        map.put(null, 1);
+    }
+    
+    @Test
+    public void givenHashMapBackedSynchronizedMap_whenNullAsValue_thenNoError() {
+        Map<String, Integer> map = Collections.synchronizedMap(new HashMap<String, Integer>());
+        map.put("1", null);
+        Assert.assertNull(map.get("1"));
+    }
+    
+    @Test
+    public void givenTreeMapBackedSynchronizedMap_whenNullAsValue_thenNoError() {
+        Map<String, Integer> map = Collections.synchronizedMap(new TreeMap<String, Integer>());
+        map.put("1", null);
+        Assert.assertNull(map.get("1"));
+    }
+    
+    @Test
+    public void givenLinkedHashMapBackedSynchronizedMap_whenNullAsValue_thenNoError() {
+        Map<String, Integer> map = Collections
+                .synchronizedMap(new LinkedHashMap<String, Integer>());
+        map.put("1", null);
+        Assert.assertNull(map.get("1"));
+    }
+    
+    @Test(expected = NullPointerException.class)
+    public void givenConcurrentHasMap_whenNullAsValue_thenException() {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+        map.put("1", null);
+    }
+
+}

core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/hashmap/loadfactor/HashMapLoadFactorUnitTest.java

@@ -0,0 +1,49 @@
+package com.baeldung.map.hashmap.loadfactor;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Assert;
+import org.junit.jupiter.api.Test;
+
+public class HashMapLoadFactorUnitTest {
+
+    @Test
+    public void whenCreateMapWithDefaultParam_thenSucces() {
+        Map<String, String> mapWithDefaultParams = new HashMap<>();
+        mapWithDefaultParams.put("1", "one");
+        mapWithDefaultParams.put("2", "two");
+        mapWithDefaultParams.put("3", "three");
+        mapWithDefaultParams.put("4", "four");
+        mapWithDefaultParams.put("5", "five");
+        
+        Assert.assertEquals(5, mapWithDefaultParams.size());
+    }
+
+    @Test
+    public void whenCreateMapWithInitialCapacity_thenSucces() {
+        Map<String, String> mapWithInitialCapacity = new HashMap<>(5);
+        mapWithInitialCapacity.put("1", "one");
+        mapWithInitialCapacity.put("2", "two");
+        mapWithInitialCapacity.put("3", "three");
+        
+        Assert.assertEquals(3, mapWithInitialCapacity.size());
+    }
+
+    @Test
+    public void whenCreateMapWithInitialCapacityAndLF_thenSucces() {
+        Map<String, String> mapWithInitialCapacityAndLF = new HashMap<>(5, 0.5f);
+        mapWithInitialCapacityAndLF.put("1", "one");
+        mapWithInitialCapacityAndLF.put("2", "two");
+        mapWithInitialCapacityAndLF.put("3", "three");
+        mapWithInitialCapacityAndLF.put("4", "four");
+        mapWithInitialCapacityAndLF.put("5", "five");
+        mapWithInitialCapacityAndLF.put("6", "six");
+        mapWithInitialCapacityAndLF.put("7", "seven");
+        mapWithInitialCapacityAndLF.put("8", "eight");
+        mapWithInitialCapacityAndLF.put("9", "nine");
+        mapWithInitialCapacityAndLF.put("10", "ten");
+     
+        Assert.assertEquals(10, mapWithInitialCapacityAndLF.size());
+    }
+}

core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/propertieshashmap/PropertiesToHashMapConverterUnitTest.java

@@ -0,0 +1,192 @@
+package com.baeldung.map.propertieshashmap;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.HashMap;
+import java.util.Properties;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PropertiesToHashMapConverterUnitTest {
+
+    private Properties properties;
+
+    private final static String propertyFileName = "toHashMap.properties";
+
+    @BeforeEach
+    public void setup() throws IOException {
+        properties = new Properties();
+        try (InputStream is = getClass().getClassLoader().getResourceAsStream(propertyFileName)) {
+            if (is != null) {
+                properties.load(is);
+            }
+        }
+    }
+
+    @Test
+    public void havingPropertiesLoaded_whenCheck_thenEquals() {
+        assertEquals(3, properties.size());
+        assertEquals("str_value", properties.get("property1"));
+        assertEquals("123", properties.get("property2"));
+        assertEquals("", properties.get("property3"));
+    }
+
+    @Test
+    public void whenPropertiesModified_thenTypeSafeIssues() {
+        compromiseProperties(properties);
+
+        assertEquals(5, properties.size());
+
+        assertNull(properties.getProperty("property4"));
+        assertNotEquals(String.class, properties.get("property4").getClass());
+        assertEquals(456, properties.get("property4"));
+
+
+        assertNull(properties.getProperty("5"));
+        assertNotEquals(String.class, properties.get(5).getClass());
+        assertEquals(10.11, properties.get(5));
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenTypeCastConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.typeCastConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenTypeCastConvert_thenClassCastException() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.typeCastConvert(properties);
+        assertEquals(5, hMap.size());
+
+        assertThrows(ClassCastException.class, () -> {
+            String s = hMap.get("property4");
+        });
+        assertEquals(Integer.class, ((Object) hMap.get("property4")).getClass());
+
+        assertNull(hMap.get("5"));
+        assertNotNull(hMap.get(5));
+        assertThrows(ClassCastException.class, () -> {
+            String s = hMap.get(5);
+        });
+        assertEquals(Double.class, ((Object) hMap.get(5)).getClass());
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenLoopConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.loopConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenLoopConvert_thenNoClassCastException() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.loopConvert(properties);
+        assertEquals(5, hMap.size());
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("property4");
+        });
+        assertEquals(String.class, hMap.get("property4").getClass());
+        assertEquals("456", hMap.get("property4"));
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("5");
+        });
+        assertEquals("10.11", hMap.get("5"));
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenStreamConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.streamConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenStreamConvert_thenNoClassCastException() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.streamConvert(properties);
+        assertEquals(5, hMap.size());
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("property4");
+        });
+        assertEquals(String.class, hMap.get("property4").getClass());
+        assertEquals("456", hMap.get("property4"));
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("5");
+        });
+        assertEquals("10.11", hMap.get("5"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenLoopConvertAndStreamConvert_thenHashMapsSame() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap1 = PropertiesToHashMapConverter.loopConvert(properties);
+        HashMap<String, String> hMap2 = PropertiesToHashMapConverter.streamConvert(properties);
+
+        assertEquals(hMap2, hMap1);
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenGuavaConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.guavaConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenGuavaConvert_thenUnableToConvertAndThrowException() {
+        compromiseProperties(properties);
+        assertThrows(Exception.class, () -> PropertiesToHashMapConverter.guavaConvert(properties));
+    }
+
+    @Test
+    public void havingModifiedPropertiesWithNoIntegerValue_whenGuavaConvert_thenNullPointerException() {
+        properties.put("property4", 456);
+        assertThrows(NullPointerException.class, () -> PropertiesToHashMapConverter.guavaConvert(properties));
+    }
+
+    @Test
+    public void havingModifiedPropertiesWithNoIntegerKey_whenGuavaConvert_thenClassCastException() {
+        properties.put(5, 10.11);
+        assertThrows(ClassCastException.class, () -> PropertiesToHashMapConverter.guavaConvert(properties));
+    }
+
+
+    private void compromiseProperties(Properties prop) {
+        prop.put("property4", 456);
+        prop.put(5, 10.11);
+    }
+}

core-java-modules/core-java-collections-maps-3/src/test/resources/toHashMap.properties

@@ -0,0 +1,3 @@
+property1=str_value
+property2=123
+property3=

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterJCStressManualTest.java

@@ -10,11 +10,17 @@ import org.openjdk.jcstress.annotations.Outcome;
 import org.openjdk.jcstress.annotations.State;
 import org.openjdk.jcstress.infra.results.I_Result;
 
+/**
+ * This is defined as a manual test because it tries to simulate the race conditions
+ * in a concurrent program that is poorly designed and hence may fail nondeterministically.
+ * This will help the CI jobs to ignore these tests and a developer to run them manually.
+ *
+ */
 @JCStressTest
 @Outcome(id = "1", expect = ACCEPTABLE_INTERESTING, desc = "One update lost.")
 @Outcome(id = "2", expect = ACCEPTABLE, desc = "Both updates.")
 @State
-public class MyCounterJCStressUnitTest {
+public class MyCounterJCStressManualTest {
 
     private MyCounter counter;
 

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterMultithreadedTCManualTest.java

@@ -1,12 +1,17 @@
 package com.baeldung.concurrent;
 
-import org.junit.Ignore;
 import org.junit.Test;
 
 import edu.umd.cs.mtc.MultithreadedTestCase;
 import edu.umd.cs.mtc.TestFramework;
 
-public class MyCounterMultithreadedTCUnitTest extends MultithreadedTestCase {
+/**
+ * This is defined as a manual test because it tries to simulate the race conditions
+ * in a concurrent program that is poorly designed and hence may fail nondeterministically.
+ * This will help the CI jobs to ignore these tests and a developer to run them manually.
+ *
+ */
+public class MyCounterMultithreadedTCManualTest extends MultithreadedTestCase {
 
     private MyCounter counter;
 
@@ -29,9 +34,8 @@ public class MyCounterMultithreadedTCUnitTest extends MultithreadedTestCase {
     	assertEquals(2, counter.getCount());
     }
 
-    @Ignore
     @Test
     public void testCounter() throws Throwable {
-        TestFramework.runManyTimes(new MyCounterMultithreadedTCUnitTest(), 1000);
+        TestFramework.runManyTimes(new MyCounterMultithreadedTCManualTest(), 1000);
     }
 }

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterSimpleManualTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.concurrent;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import org.junit.Test;
+
+/**
+ * This is defined as a manual test because it tries to simulate the race conditions
+ * in a concurrent program that is poorly designed and hence may fail nondeterministically.
+ * This will help the CI jobs to ignore these tests and a developer to run them manually.
+ *
+ */
+public class MyCounterSimpleManualTest {
+
+	@Test
+	public void testCounter() {
+		MyCounter counter = new MyCounter();
+		for (int i = 0; i < 500; i++)
+			counter.increment();
+		assertEquals(500, counter.getCount());
+	}
+
+	@Test
+	public void testCounterWithConcurrency() throws InterruptedException {
+		int numberOfThreads = 100;
+		ExecutorService service = Executors.newFixedThreadPool(10);
+		CountDownLatch latch = new CountDownLatch(numberOfThreads);
+		MyCounter counter = new MyCounter();
+		for (int i = 0; i < numberOfThreads; i++) {
+			service.execute(() -> {
+				counter.increment();
+				latch.countDown();
+			});
+		}
+		latch.await();
+		assertEquals(numberOfThreads, counter.getCount());
+	}
+
+	@Test
+	public void testSummationWithConcurrencyAndWait() throws InterruptedException {
+		int numberOfThreads = 2;
+		ExecutorService service = Executors.newFixedThreadPool(10);
+		CountDownLatch latch = new CountDownLatch(numberOfThreads);
+		MyCounter counter = new MyCounter();
+		for (int i = 0; i < numberOfThreads; i++) {
+			service.submit(() -> {
+				try {
+					counter.incrementWithWait();
+				} catch (InterruptedException e) {
+					e.printStackTrace();
+				}
+				latch.countDown();
+			});
+		}
+		latch.await();
+		assertEquals(numberOfThreads, counter.getCount());
+	}
+
+}

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterSimpleUnitTest.java

@@ -1,60 +0,0 @@
-package com.baeldung.concurrent;
-
-import static org.junit.Assert.assertEquals;
-
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-
-import org.junit.Ignore;
-import org.junit.Test;
-
-public class MyCounterSimpleUnitTest {
-
-    @Test
-    public void testCounter() {
-        MyCounter counter = new MyCounter();
-        for (int i = 0; i < 500; i++)
-            counter.increment();
-        assertEquals(500, counter.getCount());
-    }
-
-    @Ignore
-    @Test
-    public void testCounterWithConcurrency() throws InterruptedException {
-        int numberOfThreads = 100;
-        ExecutorService service = Executors.newFixedThreadPool(10);
-        CountDownLatch latch = new CountDownLatch(numberOfThreads);
-        MyCounter counter = new MyCounter();
-        for (int i = 0; i < numberOfThreads; i++) {
-            service.execute(() -> {
-                counter.increment();
-                latch.countDown();
-            });
-        }
-        latch.await();
-        assertEquals(numberOfThreads, counter.getCount());
-    }
-
-    @Ignore
-    @Test
-    public void testSummationWithConcurrencyAndWait() throws InterruptedException {
-        int numberOfThreads = 2;
-        ExecutorService service = Executors.newFixedThreadPool(10);
-        CountDownLatch latch = new CountDownLatch(numberOfThreads);
-        MyCounter counter = new MyCounter();
-        for (int i = 0; i < numberOfThreads; i++) {
-            service.submit(() -> {
-                try {
-                    counter.incrementWithWait();
-                } catch (InterruptedException e) {
-                    e.printStackTrace();
-                }
-                latch.countDown();
-            });
-        }
-        latch.await();
-        assertEquals(numberOfThreads, counter.getCount());
-    }
-
-}

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterTempusFugitManualTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.concurrent;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.AfterClass;
+import org.junit.Rule;
+import org.junit.Test;
+
+import com.google.code.tempusfugit.concurrency.ConcurrentRule;
+import com.google.code.tempusfugit.concurrency.RepeatingRule;
+import com.google.code.tempusfugit.concurrency.annotations.Concurrent;
+import com.google.code.tempusfugit.concurrency.annotations.Repeating;
+
+/**
+ * This is defined as a manual test because it tries to simulate the race conditions
+ * in a concurrent program that is poorly designed and hence may fail nondeterministically.
+ * This will help the CI jobs to ignore these tests and a developer to run them manually.
+ *
+ */
+public class MyCounterTempusFugitManualTest {
+
+	@Rule
+	public ConcurrentRule concurrently = new ConcurrentRule();
+	@Rule
+	public RepeatingRule rule = new RepeatingRule();
+
+	private static MyCounter counter = new MyCounter();
+
+	@Test
+	@Concurrent(count = 2)
+	@Repeating(repetition = 10)
+	public void runsMultipleTimes() {
+		counter.increment();
+	}
+
+	@AfterClass
+	public static void annotatedTestRunsMultipleTimes() throws InterruptedException {
+		assertEquals(counter.getCount(), 20);
+	}
+
+}

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterTempusFugitUnitTest.java

@@ -1,37 +0,0 @@
-package com.baeldung.concurrent;
-
-import static org.junit.Assert.assertEquals;
-
-import org.junit.AfterClass;
-import org.junit.Ignore;
-import org.junit.Rule;
-import org.junit.Test;
-
-import com.google.code.tempusfugit.concurrency.ConcurrentRule;
-import com.google.code.tempusfugit.concurrency.RepeatingRule;
-import com.google.code.tempusfugit.concurrency.annotations.Concurrent;
-import com.google.code.tempusfugit.concurrency.annotations.Repeating;
-
-public class MyCounterTempusFugitUnitTest {
-
-    @Rule
-    public ConcurrentRule concurrently = new ConcurrentRule();
-    @Rule
-    public RepeatingRule rule = new RepeatingRule();
-
-    private static MyCounter counter = new MyCounter();
-
-    @Ignore
-    @Test
-    @Concurrent(count = 2)
-    @Repeating(repetition = 10)
-    public void runsMultipleTimes() {
-        counter.increment();
-    }
-
-    @AfterClass
-    public static void annotatedTestRunsMultipleTimes() throws InterruptedException {
-        assertEquals(counter.getCount(), 20);
-    }
-
-}

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterThreadWeaverManualTest.java

@@ -0,0 +1,48 @@
+package com.baeldung.concurrent;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import com.google.testing.threadtester.AnnotatedTestRunner;
+import com.google.testing.threadtester.ThreadedAfter;
+import com.google.testing.threadtester.ThreadedBefore;
+import com.google.testing.threadtester.ThreadedMain;
+import com.google.testing.threadtester.ThreadedSecondary;
+
+/**
+ * This is defined as a manual test because it tries to simulate the race conditions
+ * in a concurrent program that is poorly designed and hence may fail nondeterministically.
+ * This will help the CI jobs to ignore these tests and a developer to run them manually.
+ *
+ */
+public class MyCounterThreadWeaverManualTest {
+
+	private MyCounter counter;
+
+	@ThreadedBefore
+	public void before() {
+		counter = new MyCounter();
+	}
+
+	@ThreadedMain
+	public void mainThread() {
+		counter.increment();
+	}
+
+	@ThreadedSecondary
+	public void secondThread() {
+		counter.increment();
+	}
+
+	@ThreadedAfter
+	public void after() {
+		assertEquals(2, counter.getCount());
+	}
+
+	@Test
+	public void testCounter() {
+		new AnnotatedTestRunner().runTests(this.getClass(), MyCounter.class);
+	}
+
+}

core-java-modules/core-java-concurrency-2/src/test/java/com/baeldung/concurrent/MyCounterThreadWeaverUnitTest.java

@@ -1,44 +0,0 @@
-package com.baeldung.concurrent;
-
-import static org.junit.Assert.assertEquals;
-
-import org.junit.Ignore;
-import org.junit.Test;
-
-import com.google.testing.threadtester.AnnotatedTestRunner;
-import com.google.testing.threadtester.ThreadedAfter;
-import com.google.testing.threadtester.ThreadedBefore;
-import com.google.testing.threadtester.ThreadedMain;
-import com.google.testing.threadtester.ThreadedSecondary;
-
-public class MyCounterThreadWeaverUnitTest {
-
-    private MyCounter counter;
-
-    @ThreadedBefore
-    public void before() {
-        counter = new MyCounter();
-    }
-
-    @ThreadedMain
-    public void mainThread() {
-        counter.increment();
-    }
-
-    @ThreadedSecondary
-    public void secondThread() {
-        counter.increment();
-    }
-
-    @ThreadedAfter
-    public void after() {
-        assertEquals(2, counter.getCount());
-    }
-
-    @Ignore
-    @Test
-    public void testCounter() {
-        new AnnotatedTestRunner().runTests(this.getClass(), MyCounter.class);
-    }
-
-}

core-java-modules/core-java-concurrency-advanced-4/README.md

@@ -0,0 +1,4 @@
+### Relevant Articles:
+
+- [Binary Semaphore vs Reentrant Lock](https://www.baeldung.com/java-binary-semaphore-vs-reentrant-lock)
+- [Bad Practices With Synchronization](https://www.baeldung.com/java-synchronization-bad-practices)

core-java-modules/core-java-concurrency-advanced-4/pom.xml

@@ -0,0 +1,47 @@
+<?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-concurrency-advanced-4</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-concurrency-advanced-4</name>
+    <packaging>jar</packaging>
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <dependencies>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-concurrency-advanced-4</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+
+</project>

core-java-modules/core-java-concurrency-advanced-4/src/main/java/com/baeldung/synchronizationbadpractices/AnimalBadPractice.java

@@ -0,0 +1,35 @@
+package com.baeldung.synchronizationbadpractices;
+
+public class AnimalBadPractice {
+    
+    private String name;
+    private String owner;
+    
+    public String getName() {
+        return name;
+    }
+
+    public String getOwner() {
+        return owner;
+    }
+
+    public synchronized void setName(String name) {
+        this.name = name;
+    }
+    
+    public void setOwner(String owner) {
+        synchronized(this) {
+            this.owner = owner;
+        }
+    }
+    
+    public AnimalBadPractice() {
+        
+    }
+    
+    public AnimalBadPractice(String name, String owner) {
+        this.name = name;
+        this.owner = owner;
+    }
+    
+}

core-java-modules/core-java-concurrency-advanced-4/src/main/java/com/baeldung/synchronizationbadpractices/AnimalSolution.java

@@ -0,0 +1,42 @@
+package com.baeldung.synchronizationbadpractices;
+
+public class AnimalSolution { 
+    
+    private final Object objLock1 = new Object();
+    private final Object objLock2 = new Object();
+    
+    private String name;
+    private String owner;
+    
+    public String getName() {
+        return name;
+    }
+
+    public String getOwner() {
+        return owner;
+    }
+    
+    
+    public void setName(String name) {
+        synchronized(objLock1) {
+            this.name = name;
+        }
+    }
+     
+    public void setOwner(String owner) {
+        synchronized(objLock2) {
+            this.owner = owner;
+        }
+    }
+    
+    public AnimalSolution() {
+        
+    }
+    
+    public AnimalSolution(String name, String owner) {
+        this.name = name;
+        this.owner = owner;
+    }
+    
+
+}

core-java-modules/core-java-concurrency-advanced-4/src/main/java/com/baeldung/synchronizationbadpractices/SynchronizationBadPracticeExample.java

@@ -0,0 +1,51 @@
+package com.baeldung.synchronizationbadpractices;
+
+public class SynchronizationBadPracticeExample {
+
+    public void stringBadPractice1() { 
+        String stringLock = "LOCK_STRING"; 
+        synchronized (stringLock) { 
+            // ... 
+        }
+    }
+
+    private final String stringLock = "LOCK_STRING"; 
+    public void stringBadPractice2() { 
+        synchronized (stringLock) { 
+            // ... 
+        }
+    }
+
+    private final String internedStringLock = new String("LOCK_STRING").intern(); 
+    public void stringBadPractice3() { 
+        synchronized (internedStringLock) { 
+            // ... 
+        }
+    }
+
+    private final Boolean booleanLock = Boolean.FALSE; 
+    public void booleanBadPractice() { 
+        synchronized (booleanLock) { 
+            // ...
+        }
+    }
+
+    private int count = 0; 
+    private final Integer intLock = count; 
+    public void boxedPrimitiveBadPractice() { 
+        synchronized (intLock) { 
+            count++; 
+            // ...
+        }
+    }
+
+    public void classBadPractice() throws InterruptedException {
+        AnimalBadPractice animalObj = new AnimalBadPractice("Tommy", "John");
+        synchronized(animalObj) {
+            while (true) {
+                Thread.sleep(Integer.MAX_VALUE);
+            }
+        } 
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-4/src/main/java/com/baeldung/synchronizationbadpractices/SynchronizationSolutionExample.java

@@ -0,0 +1,30 @@
+package com.baeldung.synchronizationbadpractices;
+
+public class SynchronizationSolutionExample {
+
+    private final String stringLock = new String("LOCK_STRING"); 
+    public void stringSolution() { 
+        synchronized (stringLock) { 
+            // ... 
+        }
+    }
+
+    private int count = 0;
+    private final Integer intLock = new Integer(count);
+    public void boxedPrimitiveSolution() {
+        synchronized(intLock) {
+            count++; 
+            // ... 
+        } 
+    }
+
+    private static int staticCount = 0;
+    private static final Object staticObjLock = new Object();
+    public void staticVariableSolution() {
+        synchronized(staticObjLock) {
+            staticCount++; 
+            // ... 
+        } 
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-4/src/test/java/com/baeldung/binarysemaphorereentrantlock/BinarySemaphoreVsReentrantLockUnitTest.java

@@ -0,0 +1,58 @@
+package com.baeldung.binarysemaphorereentrantlock;
+
+import static org.junit.Assert.assertEquals;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.locks.ReentrantLock;
+
+import org.junit.Test;
+
+public class BinarySemaphoreVsReentrantLockUnitTest {
+
+    @Test
+    public void givenBinarySemaphore_whenAcquireAndRelease_thenCheckAvailablePermits() throws InterruptedException {
+        Semaphore binarySemaphore = new Semaphore(1); 
+        try { 
+            binarySemaphore.acquire(); 
+            assertEquals(0, binarySemaphore.availablePermits());
+        } catch (InterruptedException e) { 
+            e.printStackTrace(); 
+        } finally { 
+            binarySemaphore.release(); 
+            assertEquals(1, binarySemaphore.availablePermits()); 
+        }
+    }
+
+    @Test
+    public void givenReentrantLock_whenLockAndUnlock_thenCheckHoldCountAndIsLocked() throws InterruptedException {
+        ReentrantLock reentrantLock = new ReentrantLock(); 
+        try { 
+            reentrantLock.lock(); 
+            assertEquals(1, reentrantLock.getHoldCount()); 
+            assertEquals(true, reentrantLock.isLocked()); 
+        } finally { 
+            reentrantLock.unlock(); 
+            assertEquals(0, reentrantLock.getHoldCount()); 
+            assertEquals(false, reentrantLock.isLocked());
+        }
+    }
+    
+    @Test
+    public void givenReentrantLock_whenLockMultipleTimes_thenUnlockMultipleTimesToRelease() throws InterruptedException {
+        ReentrantLock reentrantLock = new ReentrantLock(); 
+        try { 
+            reentrantLock.lock(); 
+            reentrantLock.lock();
+            assertEquals(2, reentrantLock.getHoldCount()); 
+            assertEquals(true, reentrantLock.isLocked()); 
+        } finally { 
+            reentrantLock.unlock(); 
+            assertEquals(1, reentrantLock.getHoldCount()); 
+            assertEquals(true, reentrantLock.isLocked());
+            
+            reentrantLock.unlock(); 
+            assertEquals(0, reentrantLock.getHoldCount()); 
+            assertEquals(false, reentrantLock.isLocked());
+        }
+    }
+    
+}

core-java-modules/core-java-datetime-conversion/src/test/java/com/baeldung/datetime/ConvertInstantToTimestampUnitTest.java

@@ -6,6 +6,7 @@ import java.sql.Timestamp;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.time.Instant;
+import java.time.format.DateTimeFormatter;
 import java.util.TimeZone;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -21,9 +22,12 @@ public class ConvertInstantToTimestampUnitTest {
         instant = timestamp.toInstant();
         assertThat(instant.toEpochMilli()).isEqualTo(timestamp.getTime());
 
-        DateFormat df = DateFormat.getDateTimeInstance();
-        df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SS'Z'");
+        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
+        formatter = formatter.withZone(TimeZone.getTimeZone("UTC").toZoneId());
+
+        DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
         df.setTimeZone(TimeZone.getTimeZone("UTC"));
-        assertThat(instant.toString()).isEqualTo(df.format(timestamp).toString());
+
+        assertThat(formatter.format(instant)).isEqualTo(df.format(timestamp));
     }
 }

core-java-modules/core-java-datetime-string/src/test/java/com/baeldung/date/StringToDateUnitTest.java

@@ -58,7 +58,8 @@ public class StringToDateUnitTest {
         LocalDateTime localDateTime = LocalDateTime.of(2015, 05, 05, 10, 15, 30);
         ZonedDateTime expectedZonedDateTime = ZonedDateTime.of(localDateTime, ZoneId.of("Europe/Paris"));
 
-        ZonedDateTime zonedDateTime = ZonedDateTime.parse("2015-05-05T10:15:30+01:00[Europe/Paris]");
+        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss z");
+        ZonedDateTime zonedDateTime = ZonedDateTime.parse("2015-05-05 10:15:30 Europe/Paris", formatter);
 
         assertThat(zonedDateTime).isEqualTo(expectedZonedDateTime);
     }

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

@@ -38,14 +38,16 @@ public class DateTimeFormatterUnitTest {
         LocalDateTime localDateTime = LocalDateTime.of(2018, 1, 1, 10, 15, 50, 500);
         ZoneId losAngelesTimeZone = TimeZone.getTimeZone("America/Los_Angeles").toZoneId();
 
-        DateTimeFormatter localizedFormatter = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL);
-        DateTimeFormatter frLocalizedFormatter =
-                DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).withLocale(Locale.FRANCE);
+        DateTimeFormatter localizedFormatter = DateTimeFormatter.ofPattern("EEEE, MMMM dd, yyyy z", Locale.US);
+        DateTimeFormatter frLocalizedFormatter = DateTimeFormatter.ofPattern("EEEE, MMMM dd, yyyy z", Locale.FRANCE);
         String formattedDateTime = localizedFormatter.format(ZonedDateTime.of(localDateTime, losAngelesTimeZone));
         String frFormattedDateTime = frLocalizedFormatter.format(ZonedDateTime.of(localDateTime, losAngelesTimeZone));
 
-        Assert.assertEquals("Monday, January 1, 2018 10:15:50 AM PST", formattedDateTime);
-        Assert.assertEquals("lundi 1 janvier 2018 10 h 15 PST", frFormattedDateTime);
+        System.out.println(formattedDateTime);
+        System.out.println(frFormattedDateTime);
+
+        Assert.assertEquals("Monday, January 01, 2018 PST", formattedDateTime);
+        Assert.assertEquals("lundi, janvier 01, 2018 PST", frFormattedDateTime);
     }
 
     @Test
@@ -105,14 +107,15 @@ public class DateTimeFormatterUnitTest {
         Assert.assertEquals("8/23/16", DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT).format(anotherSummerDay));
     }
 
-    @Test
-    public void shouldPrintStyledDateTime() {
-        LocalDateTime anotherSummerDay = LocalDateTime.of(2016, 8, 23, 13, 12, 45);
-        Assert.assertEquals("Tuesday, August 23, 2016 1:12:45 PM EET", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
-        Assert.assertEquals("August 23, 2016 1:12:45 PM EET", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
-        Assert.assertEquals("Aug 23, 2016 1:12:45 PM", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.MEDIUM).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
-        Assert.assertEquals("8/23/16 1:12 PM", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
-    }
+    // Note: The exact output format using the different FormatStyle constants differs by JVM/Java version
+    //    @Test
+    //    public void shouldPrintStyledDateTime() {
+    //        LocalDateTime anotherSummerDay = LocalDateTime.of(2016, 8, 23, 13, 12, 45);
+    //        Assert.assertEquals("Tuesday, August 23, 2016 1:12:45 PM EET", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
+    //        Assert.assertEquals("August 23, 2016 1:12:45 PM EET", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
+    //        Assert.assertEquals("Aug 23, 2016 1:12:45 PM", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.MEDIUM).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
+    //        Assert.assertEquals("8/23/16 1:12 PM", DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT).withZone(ZoneId.of("Europe/Helsinki")).format(anotherSummerDay));
+    //    }
 
     @Test
     public void shouldPrintFormattedDateTimeWithPredefined() {
@@ -126,11 +129,12 @@ public class DateTimeFormatterUnitTest {
         Assert.assertEquals(LocalDate.of(2018, 3, 12), LocalDate.from(DateTimeFormatter.ISO_LOCAL_DATE.parse("2018-03-09")).plusDays(3));
     }
 
-    @Test
-    public void shouldParseFormatStyleFull() {
-        ZonedDateTime dateTime = ZonedDateTime.from(DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).parse("Tuesday, August 23, 2016 1:12:45 PM EET"));
-        Assert.assertEquals(ZonedDateTime.of(LocalDateTime.of(2016, 8, 23, 22, 12, 45), ZoneId.of("Europe/Bucharest")), dateTime.plusHours(9));
-    }
+    // Note: The exact output format using the different FormatStyle constants differs by JVM/Java version
+    //    @Test
+    //    public void shouldParseFormatStyleFull() {
+    //        ZonedDateTime dateTime = ZonedDateTime.from(DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).parse("Tuesday, August 23, 2016 1:12:45 PM EET"));
+    //        Assert.assertEquals(ZonedDateTime.of(LocalDateTime.of(2016, 8, 23, 22, 12, 45), ZoneId.of("Europe/Bucharest")), dateTime.plusHours(9));
+    //    }
 
     @Test
     public void shouldParseDateWithCustomFormatter() {

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

@@ -7,3 +7,4 @@
 - [Java IndexOutOfBoundsException “Source Does Not Fit in Dest”](https://www.baeldung.com/java-indexoutofboundsexception)
 - [Localizing Exception Messages in Java](https://www.baeldung.com/java-localize-exception-messages)
 - [Explanation of ClassCastException in Java](https://www.baeldung.com/java-classcastexception)
+- [NoSuchFieldError in Java](https://www.baeldung.com/java-nosuchfielderror)

core-java-modules/core-java-exceptions-3/src/test/java/com/baeldung/exceptions/illegalmonitorstate/IllegalMonitorStateExceptionUnitTest.java

@@ -20,6 +20,8 @@ public class IllegalMonitorStateExceptionUnitTest {
 
         senderThread.join(1000);
         receiverThread.join(1000);
+        
+        Thread.sleep(2000);
 
         assertEquals("test", receiver.getMessage());
         assertFalse(sender.hasIllegalMonitorStateExceptionOccurred());

core-java-modules/core-java-io-2/src/main/java/com/baeldung/listfiles/ListFiles.java

@@ -24,9 +24,20 @@ public class ListFiles {
             .collect(Collectors.toSet());
     }
 
+    public Set<String> listFilesUsingFilesList(String dir) throws IOException {
+        try (Stream<Path> stream = Files.list(Paths.get(dir))) {
+            return stream
+                .filter(file -> !Files.isDirectory(file))
+                .map(Path::getFileName)
+                .map(Path::toString)
+                .collect(Collectors.toSet());
+        }
+    }
+
     public Set<String> listFilesUsingFileWalk(String dir, int depth) throws IOException {
         try (Stream<Path> stream = Files.walk(Paths.get(dir), depth)) {
-            return stream.filter(file -> !Files.isDirectory(file))
+            return stream
+                .filter(file -> !Files.isDirectory(file))
                 .map(Path::getFileName)
                 .map(Path::toString)
                 .collect(Collectors.toSet());

core-java-modules/core-java-io-2/src/test/java/com/baeldung/listfiles/ListFilesUnitTest.java

@@ -25,10 +25,15 @@ public class ListFilesUnitTest {
     };
 
     @Test
-    public void givenDir_whenUsingJAVAIO_thenListAllFiles() throws IOException {
+    public void givenDir_whenUsingJAVAIO_thenListAllFiles() {
         assertEquals(EXPECTED_FILE_LIST, listFiles.listFilesUsingJavaIO(DIRECTORY));
     }
 
+    @Test
+    public void givenDir_whenUsingFilesList_thenListAllFiles() throws IOException {
+        assertEquals(EXPECTED_FILE_LIST, listFiles.listFilesUsingFilesList(DIRECTORY));
+    }
+
     @Test
     public void givenDir_whenWalkingTree_thenListAllFiles() throws IOException {
         assertEquals(EXPECTED_FILE_LIST, listFiles.listFilesUsingFileWalk(DIRECTORY,DEPTH));

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

@@ -12,4 +12,6 @@ This module contains articles about core Java input and output (IO)
 - [Creating Temporary Directories in Java](https://www.baeldung.com/java-temp-directories)
 - [Reading a Line at a Given Line Number From a File in Java](https://www.baeldung.com/java-read-line-at-number)
 - [Find the Last Modified File in a Directory with Java](https://www.baeldung.com/java-last-modified-file)
+- [Get a Filename Without the Extension in Java](https://www.baeldung.com/java-filename-without-extension)
+- [Writing byte[] to a File in Java](https://www.baeldung.com/java-write-byte-array-file)
 - [[<-- Prev]](/core-java-modules/core-java-io-2)

core-java-modules/core-java-io-3/src/main/java/com/baeldung/filenamewithoutextension/MyFilenameUtil.java

@@ -0,0 +1,14 @@
+package com.baeldung.filenamewithoutextension;
+
+public class MyFilenameUtil {
+    private MyFilenameUtil() {}
+
+    public static String removeFileExtension(String filename, boolean removeAllExtensions) {
+        if (filename == null || filename.isEmpty()) {
+            return filename;
+        }
+
+        String extPattern = "(?<!^)[.]" + (removeAllExtensions ? ".*" : "[^.]*$");
+        return filename.replaceAll(extPattern, "");
+    }
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/filenamewithoutextension/FileNameDelExtensionUnitTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.filenamewithoutextension;
+
+import com.google.common.io.Files;
+import org.apache.commons.io.FilenameUtils;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class FileNameDelExtensionUnitTest {
+
+    @Test
+    public void givenDotFileWithoutExt_whenCallGuavaMethod_thenCannotGetDesiredResult() {
+        //negative assertion
+        assertNotEquals(".baeldung", Files.getNameWithoutExtension(".baeldung"));
+    }
+
+    @Test
+    public void givenFileWithoutMultipleExt_whenCallGuavaMethod_thenCannotRemoveAllExtensions() {
+        //negative assertion
+        assertNotEquals("baeldung", Files.getNameWithoutExtension("baeldung.tar.gz"));
+    }
+
+    @Test
+    public void givenDotFileWithoutExt_whenCallApacheCommonsMethod_thenCannotGetDesiredResult() {
+        //negative assertion
+        assertNotEquals(".baeldung", FilenameUtils.removeExtension(".baeldung"));
+    }
+
+    @Test
+    public void givenFileWithoutMultipleExt_whenCallApacheCommonsMethod_thenCannotRemoveAllExtensions() {
+        //negative assertion
+        assertNotEquals("baeldung", FilenameUtils.removeExtension("baeldung.tar.gz"));
+    }
+
+    @Test
+    public void givenFilenameNoExt_whenCallFilenameUtilMethod_thenGetExpectedFilename() {
+        assertEquals("baeldung", MyFilenameUtil.removeFileExtension("baeldung", true));
+        assertEquals("baeldung", MyFilenameUtil.removeFileExtension("baeldung", false));
+    }
+
+    @Test
+    public void givenSingleExt_whenCallFilenameUtilMethod_thenGetExpectedFilename() {
+        assertEquals("baeldung", MyFilenameUtil.removeFileExtension("baeldung.txt", true));
+        assertEquals("baeldung", MyFilenameUtil.removeFileExtension("baeldung.txt", false));
+    }
+
+
+    @Test
+    public void givenDotFile_whenCallFilenameUtilMethod_thenGetExpectedFilename() {
+        assertEquals(".baeldung", MyFilenameUtil.removeFileExtension(".baeldung", true));
+        assertEquals(".baeldung", MyFilenameUtil.removeFileExtension(".baeldung", false));
+    }
+
+    @Test
+    public void givenDotFileWithExt_whenCallFilenameUtilMethod_thenGetExpectedFilename() {
+        assertEquals(".baeldung", MyFilenameUtil.removeFileExtension(".baeldung.conf", true));
+        assertEquals(".baeldung", MyFilenameUtil.removeFileExtension(".baeldung.conf", false));
+    }
+
+    @Test
+    public void givenDoubleExt_whenCallFilenameUtilMethod_thenGetExpectedFilename() {
+        assertEquals("baeldung", MyFilenameUtil.removeFileExtension("baeldung.tar.gz", true));
+        assertEquals("baeldung.tar", MyFilenameUtil.removeFileExtension("baeldung.tar.gz", false));
+    }
+
+    @Test
+    public void givenDotFileWithDoubleExt_whenCallFilenameUtilMethod_thenGetExpectedFilename() {
+        assertEquals(".baeldung", MyFilenameUtil.removeFileExtension(".baeldung.conf.bak", true));
+        assertEquals(".baeldung.conf", MyFilenameUtil.removeFileExtension(".baeldung.conf.bak", false));
+    }
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/writebytearray/WriteByteArrayUnitTest.java

@@ -0,0 +1,77 @@
+package com.baeldung.writebytearray;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+
+import org.apache.commons.io.FileUtils;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import com.google.common.io.ByteSink;
+import com.google.common.io.MoreFiles;
+
+public class WriteByteArrayUnitTest {
+    private static byte[] dataForWriting;
+
+    @Rule
+    public TemporaryFolder tempFolder = new TemporaryFolder();
+
+    @BeforeClass
+    public static void setup() throws IOException {
+        dataForWriting = Files.readAllBytes(Paths.get("src/test/resources/example-image.jpg"));
+    }
+
+    @Test
+    public void whenUsingFileOutputStream_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-fos.jpg");
+        try (FileOutputStream outputStream = new FileOutputStream(outputFile)) {
+            outputStream.write(dataForWriting);
+            assertThat(outputFile).hasBinaryContent(dataForWriting);
+        }
+    }
+
+    @Test
+    public void whenUsingNioFiles_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-nio-files.jpg");
+        Files.write(outputFile.toPath(), dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingGuavaFiles_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-guava-files.jpg");
+        com.google.common.io.Files.write(dataForWriting, outputFile);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingGuavaByteSink_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-guava-bs.jpg");
+        ByteSink byteSink = com.google.common.io.Files.asByteSink(outputFile);
+        byteSink.write(dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingGuavaByteSinkMoreFiles_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-guava-bs.jpg");
+        ByteSink byteSink = MoreFiles.asByteSink(outputFile.toPath(), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
+        byteSink.write(dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+
+    @Test
+    public void whenUsingCommonsIo_thenByteArrayIsWritten() throws IOException {
+        File outputFile = tempFolder.newFile("example-file-utils.jpg");
+        FileUtils.writeByteArrayToFile(outputFile, dataForWriting);
+        assertThat(outputFile).hasBinaryContent(dataForWriting);
+    }
+}

core-java-modules/core-java-io-4/.gitignore

@@ -0,0 +1,2 @@
+test-link*
+0.*

core-java-modules/core-java-io-4/README.md

@@ -0,0 +1,8 @@
+## Core Java IO
+
+This module contains articles about core Java input and output (IO)
+
+### Relevant Articles: 
+
+- [Java File Separator vs File Path Separator](https://www.baeldung.com/java-file-vs-file-path-separator)
+- [[<-- Prev]](/core-java-modules/core-java-io-3)

core-java-modules/core-java-io-4/pom.xml

@@ -0,0 +1,52 @@
+<?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-io-4</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-io-4</name>
+    <packaging>jar</packaging>
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <dependencies>
+        <!-- utils -->
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>${commons-io.version}</version>
+        </dependency>
+        <!-- logging -->
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>${log4j.version}</version>
+        </dependency>
+        <dependency> <!-- needed to bridge to slf4j for projects that use the log4j APIs directly -->
+            <groupId>org.slf4j</groupId>
+            <artifactId>log4j-over-slf4j</artifactId>
+            <version>${org.slf4j.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+    </build>
+
+    <properties>
+        <assertj.version>3.6.1</assertj.version>
+    </properties>
+
+</project>

core-java-modules/core-java-io-4/src/test/java/com/baeldung/fileseparator/FilePathSeparatorUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.fileseparator;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.StringJoiner;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+
+public class FilePathSeparatorUnitTest {
+
+    @Test
+    @EnabledOnOs(OS.WINDOWS)
+    public void whenCheckPathSeparator_thenResultIsAsExpectedOnWindows() throws IOException {
+        assertEquals(";", File.pathSeparator);
+        assertEquals(';', File.pathSeparatorChar);
+    }
+    
+    @Test
+    @EnabledOnOs({ OS.LINUX, OS.MAC })
+    public void whenCheckPathSeparator_thenResultIsAsExpected() throws IOException {
+        assertEquals(":", File.pathSeparator);
+        assertEquals(':', File.pathSeparatorChar);
+    }
+    
+    @Test
+    @EnabledOnOs(OS.WINDOWS)
+    public void whenBuildPathUsingString_thenResultIsAsExpectedOnWindows() throws IOException {
+        String[] pathNames = { "path1", "path2", "path3" };
+        String path = String.join(File.pathSeparator, pathNames);
+        assertEquals("path1;path2;path3",path);
+    }
+
+    @Test
+    @EnabledOnOs({ OS.LINUX, OS.MAC })
+    public void whenBuildPathUsingString_thenResultIsAsExpected() throws IOException {
+        String[] pathNames = { "path1", "path2", "path3" };
+        String path = String.join(File.pathSeparator, pathNames);
+        assertEquals("path1:path2:path3", path);
+    }
+
+    @Test
+    @EnabledOnOs(OS.WINDOWS)
+    public void whenbuildPathUsingStringJoiner_thenResultIsAsExpectedOnWindows() throws IOException {
+        assertEquals("path1;path2", buildPathUsingStringJoiner("path1", "path2"));
+    }
+
+    @Test
+    @EnabledOnOs({ OS.LINUX, OS.MAC })
+    public void whenbuildPathUsingStringJoiner_thenResultIsAsExpected() throws IOException {
+        assertEquals("path1:path2", buildPathUsingStringJoiner("path1", "path2"));
+    }
+    
+    private String buildPathUsingStringJoiner(String path1, String path2) {
+        StringJoiner joiner = new StringJoiner(File.pathSeparator);
+        joiner.add(path1);
+        joiner.add(path2);
+        return joiner.toString();
+    }
+}

core-java-modules/core-java-io-4/src/test/java/com/baeldung/fileseparator/FileSeparatorUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.fileseparator;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.File;
+import java.nio.file.FileSystems;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+
+public class FileSeparatorUnitTest {
+
+    @Test
+    @EnabledOnOs(OS.WINDOWS)
+    public void whenCheckFileSeparator_thenCorrectOnWindows() {
+        assertEquals("\\", File.separator);
+        assertEquals('\\', File.separatorChar);
+        
+        String fileSeparator = FileSystems.getDefault().getSeparator();
+        assertEquals("\\",fileSeparator);
+    }
+    
+    @Test
+    @EnabledOnOs({ OS.LINUX, OS.MAC })
+    public void whenCheckFileSeparator_thenCorrect() {
+        assertEquals("/", File.separator);
+        assertEquals('/', File.separatorChar);
+        
+        String fileSeparator = FileSystems.getDefault().getSeparator();
+        assertEquals("/",fileSeparator);
+    }
+    
+    @Test
+    @EnabledOnOs(OS.WINDOWS)
+    public void whenBuildFilePathUsingPathsClass_thenCorrectOnWindows() {
+        Path path = Paths.get("dir1", "dir2");
+        assertEquals("dir1\\dir2", path.toString());
+    }
+
+    @Test
+    @EnabledOnOs({ OS.LINUX, OS.MAC })
+    public void whenBuildFilePathUsingPathsClass_thenCorrect() {
+        Path path = Paths.get("dir1", "dir2");
+        assertEquals("dir1/dir2", path.toString());
+    }
+
+    @Test
+    @EnabledOnOs(OS.WINDOWS)
+    public void whenBuildFilePathUsingFileClass_thenOutputIsAsExpectedOnWindows() {
+        File file = new File("file1", "file2");
+        assertEquals("file1\\file2", file.toString());
+    }
+
+    @Test
+    @EnabledOnOs({ OS.LINUX, OS.MAC })
+    public void whenBuildFilePathUsingFileClass_thenOutputIsAsExpected() {
+        File file = new File("file1", "file2");
+        assertEquals("file1/file2", file.toString());
+    }
+}

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

@@ -11,4 +11,5 @@ This module contains articles about working with the Java Virtual Machine (JVM).
 - [Where Is the Array Length Stored in JVM?](https://www.baeldung.com/java-jvm-array-length)
 - [Memory Address of Objects in Java](https://www.baeldung.com/java-object-memory-address)
 - [List All Classes Loaded in a Specific Class Loader](https://www.baeldung.com/java-list-classes-class-loader)
+- [An Introduction to the Constant Pool in the JVM](https://www.baeldung.com/jvm-constant-pool)
 - More articles: [[<-- prev]](/core-java-modules/core-java-jvm)

core-java-modules/core-java-jvm-2/src/main/java/com/baeldung/constantpool/ConstantPool.java

@@ -0,0 +1,8 @@
+package com.baeldung.constantpool;
+
+public class ConstantPool {
+    
+    public void sayHello() {
+        System.out.println("Hello World");
+    }
+}

core-java-modules/core-java-lang-2/pom.xml

@@ -69,7 +69,6 @@
         <jmh-generator.version>1.19</jmh-generator.version>
         <assertj.version>3.12.2</assertj.version>
         <commons.beanutils.version>1.9.4</commons.beanutils.version>
-        <commons-lang3.version>3.10</commons-lang3.version>
         <guava.version>29.0-jre</guava.version>
     </properties>
 

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

@@ -9,4 +9,7 @@ This module contains articles about core features in the Java language
 - [The Difference Between a.getClass() and A.class in Java](https://www.baeldung.com/java-getclass-vs-class)
 - [Constants in Java: Patterns and Anti-Patterns](https://www.baeldung.com/java-constants-good-practices)
 - [The transient Keyword in Java](https://www.baeldung.com/java-transient-keyword)
+- [How to Access an Iteration Counter in a For Each Loop](https://www.baeldung.com/java-foreach-counter)
+- [Comparing Doubles in Java](https://www.baeldung.com/java-comparing-doubles)
+- [Guide to Implementing the compareTo Method](https://www.baeldung.com/java-compareto)
 - [[<-- Prev]](/core-java-modules/core-java-lang-2)

core-java-modules/core-java-lang-3/pom.xml

@@ -23,6 +23,18 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>3.6.1</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/BankAccount.java

@@ -0,0 +1,16 @@
+package com.baeldung.compareto;
+
+public class BankAccount implements Comparable<BankAccount> {
+
+    private final int balance;
+
+    public BankAccount(int balance) {
+        this.balance = balance;
+    }
+
+    @Override
+    public int compareTo(BankAccount anotherAccount) {
+        return this.balance - anotherAccount.balance;
+    }
+
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/BankAccountFix.java

@@ -0,0 +1,16 @@
+package com.baeldung.compareto;
+
+public class BankAccountFix implements Comparable<BankAccountFix> {
+
+    private final int balance;
+
+    public BankAccountFix(int balance) {
+        this.balance = balance;
+    }
+
+    @Override
+    public int compareTo(BankAccountFix anotherAccount) {
+        return Integer.compare(this.balance, anotherAccount.balance);
+    }
+
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/FootballPlayer.java

@@ -0,0 +1,32 @@
+package com.baeldung.compareto;
+
+public class FootballPlayer implements Comparable<FootballPlayer> {
+
+    private final String name;
+    private final int goalsScored;
+
+    public FootballPlayer(String name, int goalsScored) {
+        this.name = name;
+        this.goalsScored = goalsScored;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public int compareTo(FootballPlayer anotherPlayer) {
+        return Integer.compare(this.goalsScored, anotherPlayer.goalsScored);
+    }
+
+    @Override
+    public boolean equals(Object object) {
+        if (this == object)
+            return true;
+        if (object == null || getClass() != object.getClass())
+            return false;
+        FootballPlayer player = (FootballPlayer) object;
+        return name.equals(player.name);
+    }
+
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/HandballPlayer.java

@@ -0,0 +1,12 @@
+package com.baeldung.compareto;
+
+public class HandballPlayer {
+
+    private final String name;
+    private final int height;
+
+    public HandballPlayer(String name, int height) {
+        this.name = name;
+        this.height = height;
+    }
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/comparedouble/CompareDoubleUnitTest.java

@@ -0,0 +1,71 @@
+package com.baeldung.comparedouble;
+
+import com.google.common.math.DoubleMath;
+import org.apache.commons.math3.util.Precision;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+
+public class CompareDoubleUnitTest {
+
+    @Test
+    public void givenDoubleValuesThatShouldHaveSameValue_whenUsingSimpleComparison_thenFails() {
+        double d1 = getFirstDouble(0);
+
+        double d2 = .1 * 8;
+
+        assertThat(d1 == d2).isFalse();
+    }
+
+    @Test
+    public void givenDoubleValuesThatShouldHaveSameValue_whenUsingThresholdComparison_thenSuccess() {
+        double d1 = getFirstDouble(0);
+
+        double d2 = .1 * 8;
+
+        double epsilon = 0.000001d;
+
+        assertThat(Math.abs(d1 - d2) < epsilon).isTrue();
+    }
+
+    @Test
+    public void givenDoubleValuesThatShouldHaveSameValue_whenUsingGuavaFuzzyComparison_thenSuccess() {
+        double d1 = getFirstDouble(0);
+        double d2 = .1 * 8;
+
+        double epsilon = 0.000001d;
+
+
+        assertThat(DoubleMath.fuzzyEquals(d1, d2, epsilon)).isTrue();
+    }
+
+    @Test
+    public void givenDoubleValuesThatShouldHaveSameValue_whenUsingCommonsMathComparison_thenSuccess() {
+        double d1 = getFirstDouble(0);
+        double d2 = .1 * 8;
+
+        double epsilon = 0.000001d;
+
+
+        assertThat(Precision.equals(d1, d2, epsilon)).isTrue();
+        assertThat(Precision.equals(d1, d2)).isTrue();
+    }
+
+    @Test
+    public void givenDoubleValuesThatShouldHaveSameValue_whenUsingJunitComparison_thenSuccess() {
+        double d1 = getFirstDouble(0);
+        double d2 = .1 * 8;
+
+        double epsilon = 0.000001d;
+
+        assertEquals(d1, d2, epsilon);
+    }
+
+    private double getFirstDouble(double d1) {
+        for (int i = 1; i <= 8; i++) {
+            d1 += .1;
+        }
+        return d1;
+    }
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/ArraysSortingUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.compareto;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ArraysSortingUnitTest {
+
+    @Test
+    public void givenArrayOfNumbers_whenSortingArray_thenNumbersAreSortedAscending() {
+        int[] numbers = new int[] {5, 3, 9, 11, 1, 7};
+        Arrays.sort(numbers);
+        assertThat(numbers).containsExactly(1, 3, 5, 7, 9, 11);
+    }
+
+    @Test
+    public void givenArrayOfStrings_whenSortingArray_thenStringsAreSortedAlphabetically() {
+        String[] players = new String[] {"ronaldo",  "modric", "ramos", "messi"};
+        Arrays.sort(players);
+        assertThat(players).containsExactly("messi", "modric", "ramos", "ronaldo");
+    }
+
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/BankAccountFixUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.compareto;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BankAccountFixUnitTest {
+
+    @Test
+    public void givenComparisonBasedImpl_whenUsingSmallIntegers_thenComparisonWorks() {
+        BankAccountFix accountOne = new BankAccountFix(5000);
+        BankAccountFix accountTwo = new BankAccountFix(1000);
+        int comparison = accountOne.compareTo(accountTwo);
+        assertThat(comparison).isPositive();
+    }
+
+    @Test
+    public void givenComparisonBasedImpl_whenUsingLargeIntegers_thenComparisonWorks() {
+        BankAccountFix accountOne = new BankAccountFix(1900000000);
+        BankAccountFix accountTwo = new BankAccountFix(-2000000000);
+        int comparison = accountOne.compareTo(accountTwo);
+        assertThat(comparison).isPositive();
+    }
+
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/BankAccountUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.compareto;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.*;
+
+public class BankAccountUnitTest {
+
+    @Test
+    public void givenSubtractionBasedImpl_whenUsingSmallIntegers_thenComparisonWorks() {
+        BankAccount accountOne = new BankAccount(5000);
+        BankAccount accountTwo = new BankAccount(1000);
+        int comparison = accountOne.compareTo(accountTwo);
+        assertThat(comparison).isPositive();
+    }
+
+    @Test
+    public void givenSubtractionBasedImpl_whenUsingLargeIntegers_thenComparisonBreaks() {
+        BankAccount accountOne = new BankAccount(1900000000);
+        BankAccount accountTwo = new BankAccount(-2000000000);
+        int comparison = accountOne.compareTo(accountTwo);
+        assertThat(comparison).isNegative();
+    }
+
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/FootballPlayerUnitTest.java

@@ -0,0 +1,57 @@
+package com.baeldung.compareto;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.TreeSet;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class FootballPlayerUnitTest {
+
+    @Test
+    public void givenInconsistentCompareToAndEqualsImpl_whenUsingSortedSet_thenSomeElementsAreNotAdded() {
+        FootballPlayer messi = new FootballPlayer("Messi", 800);
+        FootballPlayer ronaldo = new FootballPlayer("Ronaldo", 800);
+
+        TreeSet<FootballPlayer> set = new TreeSet<>();
+        set.add(messi);
+        set.add(ronaldo);
+
+        assertThat(set).hasSize(1);
+        assertThat(set).doesNotContain(ronaldo);
+    }
+
+    @Test
+    public void givenCompareToImpl_whenUsingCustomComparator_thenComparatorLogicIsApplied() {
+        FootballPlayer ronaldo = new FootballPlayer("Ronaldo", 900);
+        FootballPlayer messi = new FootballPlayer("Messi", 800);
+        FootballPlayer modric = new FootballPlayer("Modric", 100);
+
+        List<FootballPlayer> players = Arrays.asList(ronaldo, messi, modric);
+        Comparator<FootballPlayer> nameComparator = Comparator.comparing(FootballPlayer::getName);
+        Collections.sort(players, nameComparator);
+
+        assertThat(players).containsExactly(messi, modric, ronaldo);
+    }
+
+    @Test
+    public void givenCompareToImpl_whenSavingElementsInTreeMap_thenKeysAreSortedUsingCompareTo() {
+        FootballPlayer ronaldo = new FootballPlayer("Ronaldo", 900);
+        FootballPlayer messi = new FootballPlayer("Messi", 800);
+        FootballPlayer modric = new FootballPlayer("Modric", 100);
+
+        Map<FootballPlayer, String> players = new TreeMap<>();
+        players.put(ronaldo, "forward");
+        players.put(messi, "forward");
+        players.put(modric, "midfielder");
+
+        assertThat(players.keySet()).containsExactly(modric, messi, ronaldo);
+    }
+
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/HandballPlayerUnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.compareto;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+public class HandballPlayerUnitTest {
+
+    @Test
+    public void givenComparableIsNotImplemented_whenSortingArray_thenExceptionIsThrown() {
+        HandballPlayer duvnjak = new HandballPlayer("Duvnjak", 197);
+        HandballPlayer hansen = new HandballPlayer("Hansen", 196);
+
+        HandballPlayer[] players = new HandballPlayer[] {duvnjak, hansen};
+
+        assertThatExceptionOfType(ClassCastException.class).isThrownBy(() -> Arrays.sort(players));
+    }
+
+}

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

@@ -14,4 +14,4 @@
 - [Debugging with Eclipse](https://www.baeldung.com/eclipse-debugging)
 - [Matrix Multiplication in Java](https://www.baeldung.com/java-matrix-multiplication)
 - [Largest Power of 2 That Is Less Than the Given Number with Java](https://www.baeldung.com/java-largest-power-of-2-less-than-number)
-- More articles: [[<-- Prev]](/core-java-modules/core-java-lang-math)
+- More articles: [[<-- Prev]](/core-java-modules/core-java-lang-math)[[Next -->]](/core-java-modules/core-java-lang-math-3)

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

@@ -0,0 +1,8 @@
+=========
+
+## Core Java 8 Cookbooks and Examples - Part 3
+
+### Relevant articles:
+
+- [Evaluating a Math Expression in Java](https://www.baeldung.com/java-evaluate-math-expression-string)
+- More articles: [[<-- Prev]](/core-java-modules/core-java-lang-math-2)