Merge branch 'master' into JAVA-2399-Update_spring-security-rest_module_to_use_Swagger_3.0.0

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

@@ -7,3 +7,4 @@ This module contains articles about Java 11 core features
 - [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)
+- [Getting the Java Version at Runtime](https://www.baeldung.com/get-java-version-runtime)

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

@@ -34,4 +34,4 @@
         <maven.compiler.target>1.9</maven.compiler.target>
     </properties>
 
-</project>
+</project>

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

@@ -7,7 +7,7 @@
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-9-streams</name>
     <packaging>jar</packaging>
-    
+
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>
         <artifactId>core-java-modules</artifactId>
@@ -25,4 +25,4 @@
         </resources>
     </build>
 
-</project>
+</project>

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/illegalaccesserror/Class1.java

@@ -0,0 +1,8 @@
+package com.baeldung.exceptions.illegalaccesserror;
+
+public class Class1 {
+
+    public void bar() {
+        System.out.println("SUCCESS");
+    }
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/illegalaccesserror/Class2.java

@@ -0,0 +1,10 @@
+package com.baeldung.exceptions.illegalaccesserror;
+
+public class Class2 {
+
+    public void foo() {
+        Class1 c1 = new Class1();
+        c1.bar();
+    }
+}
+    

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/illegalaccesserror/IllegalAccessErrorExample.java

@@ -0,0 +1,20 @@
+package com.baeldung.exceptions.illegalaccesserror;
+
+public class IllegalAccessErrorExample {
+
+    interface Baeldung {
+        public default void foobar() {
+            System.out.println("This is a default method.");
+        }
+    }
+
+    class Super {
+        private void foobar() {
+            System.out.println("SuperClass method foobar");
+        }
+    }
+
+    class MySubClass extends Super implements Baeldung {
+
+    }
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/illegalaccesserror/IllegalAccessErrorSolved.java

@@ -0,0 +1,20 @@
+package com.baeldung.exceptions.illegalaccesserror;
+
+public class IllegalAccessErrorSolved {
+
+    interface BaeldungSolved {
+        public default void foobar() {
+            System.out.println("This is a default method.");
+        }
+    }
+
+    class SuperSolved {
+        public void foobar() {
+            System.out.println("SuperClass method foobar");
+        }
+    }
+
+    class MySubClassSolved extends SuperSolved implements BaeldungSolved {
+
+    }
+}

core-java-modules/core-java-exceptions-3/src/test/java/com/baeldung/exceptions/illegalaccesserror/IllegalAccessErrorExampleUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.exceptions.illegalaccesserror;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class IllegalAccessErrorExampleUnitTest {
+
+    @Test()
+    public void givenInterfaceDefaultMethOverriddenPrivateAccess_whenInvoked_thenIllegalAccessError() {
+        Assertions.assertThrows(IllegalAccessError.class, () -> {
+            new IllegalAccessErrorExample().new MySubClass().foobar();
+        });
+    }
+
+    @Test()
+    public void givenClass1Class2_whenSameClassDefintion_thenNoIllegalAccessError() {
+        Assertions.assertDoesNotThrow(() -> {
+            new Class2().foo();
+        });
+    }
+}

core-java-modules/core-java-exceptions-3/src/test/java/com/baeldung/exceptions/illegalaccesserror/IllegalAccessErrorSolvedUnitTest.java

@@ -0,0 +1,14 @@
+package com.baeldung.exceptions.illegalaccesserror;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class IllegalAccessErrorSolvedUnitTest {
+
+    @Test()
+    public void givenInterfaceDefaultMethOverriddenNonPrivateAccess_whenInvoked_thenNoIllegalAccessError() {
+        Assertions.assertDoesNotThrow(() -> {
+            new IllegalAccessErrorSolved().new MySubClassSolved().foobar();
+        });
+    }
+}

core-java-modules/core-java-io-4/src/main/java/com/baeldung/deserialization/vulnerabilities/BadThing.java

@@ -0,0 +1,28 @@
+package com.baeldung.deserialization.vulnerabilities;
+
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.lang.reflect.Method;
+
+public class BadThing implements Serializable {
+    private static final long serialVersionUID = 0L;
+
+    Object looselyDefinedThing;
+    String methodName;
+
+    private void readObject(ObjectInputStream ois) throws ClassNotFoundException, IOException {
+        ois.defaultReadObject();
+        try {
+            Method method = looselyDefinedThing.getClass().getMethod(methodName);
+            method.invoke(looselyDefinedThing);
+        } catch (Exception e) {
+            // handle error...
+        }
+    }
+
+    private void writeObject(ObjectOutputStream oos) throws IOException {
+        oos.defaultWriteObject();
+    }
+}

core-java-modules/core-java-io-4/src/main/java/com/baeldung/deserialization/vulnerabilities/MyCustomAttackObject.java

@@ -0,0 +1,14 @@
+package com.baeldung.deserialization.vulnerabilities;
+
+import java.io.IOException;
+import java.io.Serializable;
+
+public class MyCustomAttackObject implements Serializable {
+    public static void methodThatTriggersAttack() {
+        try {
+            Runtime.getRuntime().exec("echo \"Oh, no! I've been hacked\"");
+        } catch (IOException e) {
+            // handle error...
+        }
+    }
+}

core-java-modules/core-java-io-4/src/test/java/com/baeldung/deserialization/vulnerabilities/BadThingUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.deserialization.vulnerabilities;
+
+import org.junit.Test;
+import org.junit.jupiter.api.DisplayName;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+
+public class BadThingUnitTest {
+
+    @Test
+    @DisplayName("When a BadThing object is deserialized, then code execution in MyCustomAttackObject is run.")
+    public void givenABadThingObject_whenItsDeserialized_thenExecutionIsRun() throws Exception {
+        BadThing bt = new BadThing();
+
+        bt.looselyDefinedThing = new MyCustomAttackObject();
+        bt.methodName = "methodThatTriggersAttack";
+
+        byte[] serializedObject = serialize(bt);
+
+        try (InputStream bis = new ByteArrayInputStream(serializedObject);
+             ObjectInputStream ois = new ObjectInputStream(bis)) {
+
+            ois.readObject(); // malicious code is run
+        }
+    }
+
+    private static byte[] serialize(Object object) throws Exception {
+        try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
+             ObjectOutputStream oos = new ObjectOutputStream(bos)) {
+
+            oos.writeObject(object);
+            oos.flush();
+            return bos.toByteArray();
+        }
+    }
+}

core-java-modules/core-java-jpms/decoupling-pattern2/consumermodule2/pom.xml

@@ -45,4 +45,4 @@
         <providermodule.version>1.0</providermodule.version>
     </properties>
 
-</project>
+</project>

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

@@ -5,3 +5,4 @@ This module contains articles about core features in the Java language
 - [The Java final Keyword – Impact on Performance](https://www.baeldung.com/java-final-performance)
 - [The package-info.java File](https://www.baeldung.com/java-package-info)
 - [What are Compile-time Constants in Java?](https://www.baeldung.com/java-compile-time-constants)
+- [Java Objects.hash() vs Objects.hashCode()](https://www.baeldung.com/java-objects-hash-vs-objects-hashcode)

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

@@ -7,3 +7,4 @@ This module contains articles about Object-oriented programming (OOP) patterns i
 - [Inheritance and Composition (Is-a vs Has-a relationship) in Java](https://www.baeldung.com/java-inheritance-composition)
 - [Immutable Objects in Java](https://www.baeldung.com/java-immutable-object)
 - [How to Make a Deep Copy of an Object in Java](https://www.baeldung.com/java-deep-copy)
+- [Using an Interface vs. Abstract Class in Java](https://www.baeldung.com/java-interface-vs-abstract-class)

core-java-modules/core-java-regex/src/test/java/com/baeldung/ignore/pattern/metacharacters/IgnoringPatternMetacharactersUnitTest.java

@@ -0,0 +1,54 @@
+package com.baeldung.ignore.pattern.metacharacters;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.junit.Test;
+
+public class IgnoringPatternMetacharactersUnitTest {
+    private static final String dollarAmounts = "$100.25, $100.50, $150.50, $100.50, $100.75";
+    private static final String patternStr = "$100.50";
+
+    @Test
+    public void givenPatternStringHasMetacharacters_whenPatternMatchedWithoutEscapingMetacharacters_thenNoMatchesFound() {
+        Pattern pattern = Pattern.compile(patternStr);
+        Matcher matcher = pattern.matcher(dollarAmounts);
+
+        int matches = 0;
+        while (matcher.find()) {
+            matches++;
+        }
+
+        assertEquals(0, matches);
+    }
+
+    @Test
+    public void givenPatternStringHasMetacharacters_whenPatternCompiledUsingManuallyMetaEscapedPattern_thenMatchingSuccessful() {
+        String metaEscapedPatternStr = "\\Q" + patternStr + "\\E";
+        Pattern pattern = Pattern.compile(metaEscapedPatternStr);
+        Matcher matcher = pattern.matcher(dollarAmounts);
+
+        int matches = 0;
+        while (matcher.find()) {
+            matches++;
+        }
+
+        assertEquals(2, matches);
+    }
+
+    @Test
+    public void givenPatternStringHasMetacharacters_whenPatternCompiledUsingLiteralPatternFromQuote_thenMatchingSuccessful() {
+        String literalPatternStr = Pattern.quote(patternStr);
+        Pattern pattern = Pattern.compile(literalPatternStr);
+        Matcher matcher = pattern.matcher(dollarAmounts);
+
+        int matches = 0;
+        while (matcher.find()) {
+            matches++;
+        }
+
+        assertEquals(2, matches);
+    }
+}

core-java-modules/core-java-security-2/src/main/java/com/baeldung/secretkeyandstringconversion/ConversionClassUtil.java

@@ -0,0 +1,53 @@
+package com.baeldung.secretkeyandstringconversion;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.KeySpec;
+import java.util.Base64;
+
+import javax.crypto.KeyGenerator;
+import javax.crypto.SecretKey;
+import javax.crypto.SecretKeyFactory;
+import javax.crypto.spec.PBEKeySpec;
+import javax.crypto.spec.SecretKeySpec;
+
+public class ConversionClassUtil {
+
+	/* Generating Secret key */
+
+	// Generating Secret Key using KeyGenerator class with 256
+	public static SecretKey generateKey(int n) throws NoSuchAlgorithmException {
+		KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
+		keyGenerator.init(n);
+		SecretKey originalKey = keyGenerator.generateKey();
+		return originalKey;
+	}
+
+	// Generating Secret Key using password and salt
+	public static SecretKey getKeyFromPassword(String password, String salt)
+			throws NoSuchAlgorithmException, InvalidKeySpecException {
+		SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
+		KeySpec spec = new PBEKeySpec(password.toCharArray(), salt.getBytes(), 65536, 256);
+		SecretKey originalKey = new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
+		return originalKey;
+	}
+
+	/* Converting Secret key into String */
+	public static String convertSecretKeyToString(SecretKey secretKey) throws NoSuchAlgorithmException {
+		// Converting the Secret Key into byte array
+		byte[] rawData = secretKey.getEncoded();
+		// Getting String - Base64 encoded version of the Secret Key
+		String encodedKey = Base64.getEncoder().encodeToString(rawData);
+		return encodedKey;
+	}
+
+	/* Converting String into Secret key into */
+	public static SecretKey convertStringToSecretKeyto(String encodedKey) {
+		// Decoding the Base64 encoded string into byte array
+		byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
+		// Rebuilding the Secret Key using SecretKeySpec Class
+		SecretKey originalKey = new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES");
+		return originalKey;
+	}
+
+}

core-java-modules/core-java-security-2/src/test/java/com/baeldung/secretkeyandstringconversion/ConversionClassUtilUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.secretkeyandstringconversion;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.spec.InvalidKeySpecException;
+
+import javax.crypto.SecretKey;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ConversionClassUtilUnitTest {
+
+	@Test
+	void givenPasswordAndSalt_whenCreateSecreKeyCheckConversion_thenSuccess()
+			throws NoSuchAlgorithmException, InvalidKeySpecException {
+		// given
+		String password = "Baeldung@2021";
+		String salt = "@$#baelDunG@#^$*";
+
+		// when
+		SecretKey encodedKey = ConversionClassUtil.getKeyFromPassword(password, salt);
+		String encodedString = ConversionClassUtil.convertSecretKeyToString(encodedKey);
+		SecretKey decodeKey = ConversionClassUtil.convertStringToSecretKeyto(encodedString);
+
+		// then
+		Assertions.assertEquals(encodedKey, decodeKey);
+	}
+
+	@Test
+	void givenSize_whenCreateSecreKeyCheckConversion_thenSuccess()
+			throws NoSuchAlgorithmException, InvalidKeySpecException {
+		// given
+		int size = 256;
+
+		// when
+		SecretKey encodedKey = ConversionClassUtil.generateKey(size);
+		String encodedString = ConversionClassUtil.convertSecretKeyToString(encodedKey);
+		SecretKey decodeKey = ConversionClassUtil.convertStringToSecretKeyto(encodedString);
+
+		// then
+		Assertions.assertEquals(encodedKey, decodeKey);
+	}
+
+}

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

@@ -12,4 +12,5 @@ This module contains articles about the Stream API in Java.
 - [Should We Close a Java Stream?](https://www.baeldung.com/java-stream-close)
 - [Returning Stream vs. Collection](https://www.baeldung.com/java-return-stream-collection)
 - [Convert a Java Enumeration Into a Stream](https://www.baeldung.com/java-enumeration-to-stream)
+- [When to Use a Parallel Stream in Java](https://www.baeldung.com/java-when-to-use-parallel-stream)
 - More articles: [[<-- prev>]](/../core-java-streams-2)

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

@@ -27,6 +27,17 @@
             <version>${lombok.version}</version>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+            <scope>test</scope>
+        </dependency>
         <!-- test scoped -->
         <dependency>
             <groupId>org.assertj</groupId>
@@ -44,11 +55,30 @@
                 <filtering>true</filtering>
             </resource>
         </resources>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                    <annotationProcessorPaths>
+                        <path>
+                            <groupId>org.openjdk.jmh</groupId>
+                            <artifactId>jmh-generator-annprocess</artifactId>
+                            <version>${jmh.version}</version>
+                        </path>
+                    </annotationProcessorPaths>
+                </configuration>
+            </plugin>
+        </plugins>
     </build>
 
     <properties>
+        <lombok.version>1.18.20</lombok.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
+        <jmh.version>1.29</jmh.version>
     </properties>
 
 </project>

core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/BenchmarkRunner.java

@@ -0,0 +1,9 @@
+package com.baeldung.streams.parallel;
+
+public class BenchmarkRunner {
+
+    public static void main(String[] args) throws Exception {
+        org.openjdk.jmh.Main.main(args);
+    }
+
+}

core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/DifferentSourceSplitting.java

@@ -0,0 +1,54 @@
+package com.baeldung.streams.parallel;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+public class DifferentSourceSplitting {
+
+    private static final List<Integer> arrayListOfNumbers = new ArrayList<>();
+    private static final List<Integer> linkedListOfNumbers = new LinkedList<>();
+
+    static {
+        IntStream.rangeClosed(1, 1_000_000).forEach(i -> {
+            arrayListOfNumbers.add(i);
+            linkedListOfNumbers.add(i);
+        });
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void differentSourceArrayListSequential() {
+        arrayListOfNumbers.stream().reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void differentSourceArrayListParallel() {
+        arrayListOfNumbers.parallelStream().reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void differentSourceLinkedListSequential() {
+        linkedListOfNumbers.stream().reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void differentSourceLinkedListParallel() {
+        linkedListOfNumbers.parallelStream().reduce(0, Integer::sum);
+    }
+
+}

core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/MemoryLocalityCosts.java

@@ -0,0 +1,52 @@
+package com.baeldung.streams.parallel;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+
+import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+public class MemoryLocalityCosts {
+
+    private static final int[] intArray = new int[1_000_000];
+    private static final Integer[] integerArray = new Integer[1_000_000];
+
+    static {
+        IntStream.rangeClosed(1, 1_000_000).forEach(i -> {
+            intArray[i-1] = i;
+            integerArray[i-1] = i;
+        });
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void localityIntArraySequential() {
+        Arrays.stream(intArray).reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void localityIntArrayParallel() {
+        Arrays.stream(intArray).parallel().reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void localityIntegerArraySequential() {
+        Arrays.stream(integerArray).reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void localityIntegerArrayParallel() {
+        Arrays.stream(integerArray).parallel().reduce(0, Integer::sum);
+    }
+
+}

core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/MergingCosts.java

@@ -0,0 +1,52 @@
+package com.baeldung.streams.parallel;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class MergingCosts {
+
+    private static final List<Integer> arrayListOfNumbers = new ArrayList<>();
+
+    static {
+        IntStream.rangeClosed(1, 1_000_000).forEach(i -> {
+            arrayListOfNumbers.add(i);
+        });
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void mergingCostsSumSequential() {
+        arrayListOfNumbers.stream().reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void mergingCostsSumParallel() {
+        arrayListOfNumbers.stream().parallel().reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void mergingCostsGroupingSequential() {
+        arrayListOfNumbers.stream().collect(Collectors.toSet());
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void mergingCostsGroupingParallel() {
+        arrayListOfNumbers.stream().parallel().collect(Collectors.toSet());
+    }
+
+}

core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/ParallelStream.java

@@ -0,0 +1,15 @@
+package com.baeldung.streams.parallel;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class ParallelStream {
+
+    public static void main(String[] args) {
+        List<Integer> listOfNumbers = Arrays.asList(1, 2, 3, 4);
+        listOfNumbers.parallelStream().forEach(number ->
+          System.out.println(number + " " + Thread.currentThread().getName())
+        );
+    }
+
+}

core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/SequentialStream.java

@@ -0,0 +1,15 @@
+package com.baeldung.streams.parallel;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class SequentialStream {
+
+    public static void main(String[] args) {
+        List<Integer> listOfNumbers = Arrays.asList(1, 2, 3, 4);
+        listOfNumbers.stream().forEach(number ->
+          System.out.println(number + " " + Thread.currentThread().getName())
+        );
+    }
+
+}

core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/SplittingCosts.java

@@ -0,0 +1,27 @@
+package com.baeldung.streams.parallel;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+public class SplittingCosts {
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void sourceSplittingIntStreamSequential() {
+        IntStream.rangeClosed(1, 100).reduce(0, Integer::sum);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public static void sourceSplittingIntStreamParallel() {
+        IntStream.rangeClosed(1, 100).parallel().reduce(0, Integer::sum);
+    }
+
+}

core-java-modules/core-java-streams-3/src/test/java/com/baeldung/streams/parallel/ForkJoinUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung.streams.parallel;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ForkJoinPool;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ForkJoinUnitTest {
+
+    @Test
+    void givenSequentialStreamOfNumbers_whenReducingSumWithIdentityFive_thenResultIsCorrect() {
+        List<Integer> listOfNumbers = Arrays.asList(1, 2, 3, 4);
+        int sum = listOfNumbers.stream().reduce(5, Integer::sum);
+        assertThat(sum).isEqualTo(15);
+    }
+
+    @Test
+    void givenParallelStreamOfNumbers_whenReducingSumWithIdentityFive_thenResultIsNotCorrect() {
+        List<Integer> listOfNumbers = Arrays.asList(1, 2, 3, 4);
+        int sum = listOfNumbers.parallelStream().reduce(5, Integer::sum);
+        assertThat(sum).isNotEqualTo(15);
+    }
+
+    @Test
+    void givenParallelStreamOfNumbers_whenReducingSumWithIdentityZero_thenResultIsCorrect() {
+        List<Integer> listOfNumbers = Arrays.asList(1, 2, 3, 4);
+        int sum = listOfNumbers.parallelStream().reduce(0, Integer::sum) + 5;
+        assertThat(sum).isEqualTo(15);
+    }
+
+    @Test
+    public void givenParallelStreamOfNumbers_whenUsingCustomThreadPool_thenResultIsCorrect()
+      throws InterruptedException, ExecutionException {
+        List<Integer> listOfNumbers = Arrays.asList(1, 2, 3, 4);
+        ForkJoinPool customThreadPool = new ForkJoinPool(4);
+        int sum = customThreadPool.submit(
+          () -> listOfNumbers.parallelStream().reduce(0, Integer::sum)).get();
+        customThreadPool.shutdown();
+        assertThat(sum).isEqualTo(10);
+    }
+
+}

core-java-modules/core-java-string-conversions-2/README.md

@@ -6,4 +6,5 @@ This module contains articles about string conversions from/to another type.
 - [Java String Conversions](https://www.baeldung.com/java-string-conversions)
 - [Convert String to Byte Array and Reverse in Java](https://www.baeldung.com/java-string-to-byte-array)
 - [Convert Character Array to String in Java](https://www.baeldung.com/java-char-array-to-string)
+- [Converting String to BigDecimal in Java](https://www.baeldung.com/java-string-to-bigdecimal)
 - More articles: [[<-- prev]](/core-java-string-conversions)

core-java-modules/core-java-string-conversions-2/src/test/java/com/baeldung/stringtobigdecimal/StringToBigDecimalConversionUnitTest.java

@@ -0,0 +1,74 @@
+package com.baeldung.stringtobigdecimal;
+
+import static org.junit.Assert.assertEquals;
+
+import java.math.BigDecimal;
+import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
+import java.text.ParseException;
+
+import org.junit.Test;
+
+public class StringToBigDecimalConversionUnitTest {
+
+	@Test
+	public void givenValidString_WhenBigDecimalObjectWithStringParameter_ThenResultIsDecimalObject() {
+		BigDecimal bigDecimal = new BigDecimal("123");
+		assertEquals(new BigDecimal(123), bigDecimal);
+	}
+
+	@Test(expected = NullPointerException.class)
+	public void givenNullString_WhenBigDecimalObjectWithStringParameter_ThenNullPointerExceptionIsThrown() {
+		String bigDecimal = null;
+		new BigDecimal(bigDecimal);
+	}
+
+	@Test(expected = NumberFormatException.class)
+	public void givenInalidString_WhenBigDecimalObjectWithStringParameter_ThenNumberFormatExceptionIsThrown() {
+		new BigDecimal("&");
+	}
+
+	@Test
+	public void givenValidString_WhenValueOfDoubleFromString_ThenResultIsDecimalObject() {
+		BigDecimal bigDecimal = BigDecimal.valueOf(Double.valueOf("123.42"));
+		assertEquals(new BigDecimal(123.42).setScale(2, BigDecimal.ROUND_HALF_UP), bigDecimal);
+	}
+
+	@Test(expected = NullPointerException.class)
+	public void givenNullString_WhenValueOfDoubleFromString_ThenNullPointerExceptionIsThrown() {
+		BigDecimal.valueOf(Double.valueOf(null));
+	}
+
+	@Test(expected = NumberFormatException.class)
+	public void givenInalidString_WhenValueOfDoubleFromString_ThenNumberFormatExceptionIsThrown() {
+		BigDecimal.valueOf(Double.valueOf("&"));
+	}
+
+	@Test
+	public void givenValidString_WhenDecimalFormatOfString_ThenResultIsDecimalObject() throws ParseException {
+		BigDecimal bigDecimal = new BigDecimal(10692467440017.111).setScale(3, BigDecimal.ROUND_HALF_UP);
+
+		DecimalFormatSymbols symbols = new DecimalFormatSymbols();
+		symbols.setGroupingSeparator(',');
+		symbols.setDecimalSeparator('.');
+		String pattern = "#,##0.0#";
+		DecimalFormat decimalFormat = new DecimalFormat(pattern, symbols);
+		decimalFormat.setParseBigDecimal(true);
+
+		// parse the string value
+		BigDecimal parsedStringValue = (BigDecimal) decimalFormat.parse("10,692,467,440,017.111");
+
+		assertEquals(bigDecimal, parsedStringValue);
+	}
+
+	@Test(expected = NullPointerException.class)
+	public void givenNullString_WhenDecimalFormatOfString_ThenNullPointerExceptionIsThrown() throws ParseException {
+		new DecimalFormat("#").parse(null);
+	}
+
+	@Test(expected = ParseException.class)
+	public void givenInalidString_WhenDecimalFormatOfString_ThenNumberFormatExceptionIsThrown() throws ParseException {
+		new DecimalFormat("#").parse("&");
+	}
+
+}