Merge branch 'master' of https://github.com/eugenp/tutorials into BAEL-12800

algorithms-miscellaneous-2/README.md

@@ -15,3 +15,5 @@
 - [Calculate Percentage in Java](https://www.baeldung.com/java-calculate-percentage)
 - [Converting Between Byte Arrays and Hexadecimal Strings in Java](https://www.baeldung.com/java-byte-arrays-hex-strings)
 - [Convert Latitude and Longitude to a 2D Point in Java](https://www.baeldung.com/java-convert-latitude-longitude)
+- [Reversing a Binary Tree in Java](https://www.baeldung.com/java-reversing-a-binary-tree)
+- [Find If Two Numbers Are Relatively Prime in Java](https://www.baeldung.com/java-two-relatively-prime-numbers)

algorithms-miscellaneous-3/README.md

@@ -4,4 +4,3 @@
 - [Implementing Simple State Machines with Java Enums](https://www.baeldung.com/java-enum-simple-state-machine)
 - [Converting Between Roman and Arabic Numerals in Java](http://www.baeldung.com/java-convert-roman-arabic)
 - [Practical Java Examples of the Big O Notation](http://www.baeldung.com/java-algorithm-complexity)
-- [An Introduction to the Theory of Big-O Notation](http://www.baeldung.com/big-o-notation)

core-groovy-2/README.md

@@ -3,5 +3,5 @@
 ## Relevant articles:
 
 - [String Matching in Groovy](http://www.baeldung.com/)
-- [Groovy def Keyword]
-
+- [Groovy def Keyword](https://www.baeldung.com/groovy-def-keyword)
+- [Pattern Matching in Strings in Groovy](https://www.baeldung.com/groovy-pattern-matching)

core-groovy-2/src/main/resources/articleEmail.template

@@ -0,0 +1,5 @@
+Dear <% out << (user) %>,
+Please read the requested article below.
+<% out << (articleText) %>
+From,
+<% out << (signature) %>

core-groovy-2/src/main/resources/email.template

@@ -0,0 +1,3 @@
+Dear $user,
+Thanks for subscribing our services.
+${signature}

core-groovy-2/src/test/groovy/com/baeldung/templateengine/TemplateEnginesUnitTest.groovy

@@ -0,0 +1,96 @@
+package com.baeldung.templateengine
+
+import groovy.text.SimpleTemplateEngine
+import groovy.text.StreamingTemplateEngine
+import groovy.text.GStringTemplateEngine
+import groovy.text.XmlTemplateEngine
+import groovy.text.XmlTemplateEngine
+import groovy.text.markup.MarkupTemplateEngine
+import groovy.text.markup.TemplateConfiguration
+
+class TemplateEnginesUnitTest extends GroovyTestCase {
+    
+    def bindMap = [user: "Norman", signature: "Baeldung"]
+    
+    void testSimpleTemplateEngine() {
+        def smsTemplate = 'Dear <% print user %>, Thanks for reading our Article. ${signature}'
+        def smsText = new SimpleTemplateEngine().createTemplate(smsTemplate).make(bindMap)
+
+        assert smsText.toString() == "Dear Norman, Thanks for reading our Article. Baeldung"
+    }
+    
+    void testStreamingTemplateEngine() {
+        def articleEmailTemplate = new File('src/main/resources/articleEmail.template')
+        bindMap.articleText = """1. Overview
+This is a tutorial article on Template Engines""" //can be a string larger than 64k
+        
+        def articleEmailText = new StreamingTemplateEngine().createTemplate(articleEmailTemplate).make(bindMap)
+        
+        assert articleEmailText.toString() == """Dear Norman,
+Please read the requested article below.
+1. Overview
+This is a tutorial article on Template Engines
+From,
+Baeldung"""
+        
+    }
+    
+    void testGStringTemplateEngine() {
+        def emailTemplate = new File('src/main/resources/email.template')
+        def emailText = new GStringTemplateEngine().createTemplate(emailTemplate).make(bindMap)
+        
+        assert emailText.toString() == "Dear Norman,\nThanks for subscribing our services.\nBaeldung"
+    }
+    
+    void testXmlTemplateEngine() {
+        def emailXmlTemplate = '''<xs xmlns:gsp='groovy-server-pages'>
+                                      <gsp:scriptlet>def emailContent = "Thanks for subscribing our services."</gsp:scriptlet>
+                                      <email>
+                                          <greet>Dear ${user}</greet>
+                                          <content><gsp:expression>emailContent</gsp:expression></content>
+                                          <signature>${signature}</signature>
+                                      </email>
+                                  </xs>'''
+        def emailXml = new XmlTemplateEngine().createTemplate(emailXmlTemplate).make(bindMap)
+        println emailXml.toString()
+    }
+    
+    void testMarkupTemplateEngineHtml() {
+        def emailHtmlTemplate = """html {
+                                       head {
+                                           title('Service Subscription Email')
+                                       }
+                                       body {
+                                           p('Dear Norman')
+                                           p('Thanks for subscribing our services.')
+                                           p('Baeldung')
+                                       }
+                                   }"""
+        
+        
+        def emailHtml = new MarkupTemplateEngine().createTemplate(emailHtmlTemplate).make()
+        println emailHtml.toString()
+        
+    }
+    
+    void testMarkupTemplateEngineXml() {
+        def emailXmlTemplate = """xmlDeclaration()  
+                                      xs{
+                                          email {
+                                              greet('Dear Norman')
+                                              content('Thanks for subscribing our services.')
+                                              signature('Baeldung')
+                                          }  
+                                      }
+                               """
+        TemplateConfiguration config = new TemplateConfiguration()
+        config.autoIndent = true
+        config.autoEscape = true
+        config.autoNewLine = true
+
+        def emailXml = new MarkupTemplateEngine(config).createTemplate(emailXmlTemplate).make()
+        
+        println emailXml.toString()
+    }
+    
+}

core-groovy-collections/README.md

@@ -2,5 +2,5 @@
 
 ## Relevant articles:
 
-- [Maps in Groovy](http://www.baeldung.com/)
+- [Maps in Groovy](https://www.baeldung.com/groovy-maps)
 

core-java-arrays/README.MD

@@ -0,0 +1,3 @@
+## Relevant Articles
+
+- [Extending an Array’s Length](https://www.baeldung.com/java-array-add-element-at-the-end)

core-java-arrays/src/main/java/com/baeldung/array/conversions/StreamArrayConversion.java

@@ -0,0 +1,52 @@
+package com.baeldung.array.conversions;
+
+import java.util.Arrays;
+import java.util.function.IntFunction;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+public class StreamArrayConversion {
+
+    public static String[] stringStreamToStringArrayUsingFunctionalInterface(Stream<String> stringStream) {
+        IntFunction<String[]> intFunction = new IntFunction<String[]>() {
+            @Override
+            public String[] apply(int value) {
+                return new String[value];
+            }
+        };
+
+        return stringStream.toArray(intFunction);
+    }
+
+    public static String[] stringStreamToStringArrayUsingMethodReference(Stream<String> stringStream) {
+        return stringStream.toArray(String[]::new);
+    }
+
+    public static String[] stringStreamToStringArrayUsingLambda(Stream<String> stringStream) {
+        return stringStream.toArray(value -> new String[value]);
+    }
+
+    public static Integer[] integerStreamToIntegerArray(Stream<Integer> integerStream) {
+        return integerStream.toArray(Integer[]::new);
+    }
+
+    public static int[] intStreamToPrimitiveIntArray(Stream<Integer> integerStream) {
+        return integerStream.mapToInt(i -> i).toArray();
+    }
+
+    public static Stream<String> stringArrayToStreamUsingArraysStream(String[] stringArray) {
+        return Arrays.stream(stringArray);
+    }
+
+    public static Stream<String> stringArrayToStreamUsingStreamOf(String[] stringArray) {
+        return Stream.of(stringArray);
+    }
+
+    public static IntStream primitiveIntArrayToStreamUsingArraysStream(int[] intArray) {
+        return Arrays.stream(intArray);
+    }
+
+    public static Stream<int[]> primitiveIntArrayToStreamUsingStreamOf(int[] intArray) {
+        return Stream.of(intArray);
+    }
+}

core-java-arrays/src/test/java/com/baeldung/array/conversions/StreamArrayConversionUnitTest.java

@@ -0,0 +1,70 @@
+package com.baeldung.array.conversions;
+
+import static com.baeldung.array.conversions.StreamArrayConversion.intStreamToPrimitiveIntArray;
+import static com.baeldung.array.conversions.StreamArrayConversion.integerStreamToIntegerArray;
+import static com.baeldung.array.conversions.StreamArrayConversion.stringStreamToStringArrayUsingFunctionalInterface;
+import static com.baeldung.array.conversions.StreamArrayConversion.stringStreamToStringArrayUsingLambda;
+import static com.baeldung.array.conversions.StreamArrayConversion.stringStreamToStringArrayUsingMethodReference;
+import static com.baeldung.array.conversions.StreamArrayConversion.stringArrayToStreamUsingArraysStream;
+import static com.baeldung.array.conversions.StreamArrayConversion.stringArrayToStreamUsingStreamOf;
+import static com.baeldung.array.conversions.StreamArrayConversion.primitiveIntArrayToStreamUsingArraysStream;
+import static com.baeldung.array.conversions.StreamArrayConversion.primitiveIntArrayToStreamUsingStreamOf;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import com.google.common.collect.Iterators;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+import org.junit.Test;
+
+public class StreamArrayConversionUnitTest {
+
+    private String[] stringArray = new String[]{"baeldung", "convert", "to", "string", "array"};
+    private Integer[] integerArray = new Integer[]{1, 2, 3, 4, 5, 6, 7};
+    private int[] intPrimitiveArray = new int[]{1, 2, 3, 4, 5, 6, 7};
+
+    @Test
+    public void givenStringStream_thenConvertToStringArrayUsingFunctionalInterface() {
+        Stream<String> stringStream = Stream.of("baeldung", "convert", "to", "string", "array");
+        assertArrayEquals(stringArray, stringStreamToStringArrayUsingFunctionalInterface(stringStream));
+    }
+
+    @Test
+    public void givenStringStream_thenConvertToStringArrayUsingMethodReference() {
+        Stream<String> stringStream = Stream.of("baeldung", "convert", "to", "string", "array");
+        assertArrayEquals(stringArray, stringStreamToStringArrayUsingMethodReference(stringStream));
+    }
+
+    @Test
+    public void givenStringStream_thenConvertToStringArrayUsingLambda() {
+        Stream<String> stringStream = Stream.of("baeldung", "convert", "to", "string", "array");
+        assertArrayEquals(stringArray, stringStreamToStringArrayUsingLambda(stringStream));
+    }
+
+    @Test
+    public void givenIntegerStream_thenConvertToIntegerArray() {
+        Stream<Integer> integerStream = Stream.of(1, 2, 3, 4, 5, 6, 7);
+        assertArrayEquals(integerArray, integerStreamToIntegerArray(integerStream));
+    }
+
+    @Test
+    public void givenIntStream_thenConvertToIntegerArray() {
+        Stream<Integer> integerStream = IntStream.rangeClosed(1, 7).boxed();
+        assertArrayEquals(intPrimitiveArray, intStreamToPrimitiveIntArray(integerStream));
+    }
+
+    @Test
+    public void givenStringArray_whenConvertedTwoWays_thenConvertedStreamsAreEqual() {
+        assertTrue(Iterators
+            .elementsEqual(stringArrayToStreamUsingArraysStream(stringArray).iterator(),
+                stringArrayToStreamUsingStreamOf(stringArray).iterator()));
+    }
+
+    @Test
+    public void givenPrimitiveArray_whenConvertedTwoWays_thenConvertedStreamsAreNotEqual() {
+        assertFalse(Iterators.elementsEqual(
+            primitiveIntArrayToStreamUsingArraysStream(intPrimitiveArray).iterator(),
+            primitiveIntArrayToStreamUsingStreamOf(intPrimitiveArray).iterator()));
+    }
+}

core-java-lambdas/README.md

@@ -0,0 +1,2 @@
+### Relevant Articles:
+- [Java 9 java.lang.Module API](https://www.baeldung.com/java-lambda-effectively-final-local-variables)

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

@@ -7,3 +7,4 @@
 - [Exploring the New HTTP Client in Java 9 and 11](https://www.baeldung.com/java-9-http-client)
 - [An Introduction to Epsilon GC: A No-Op Experimental Garbage Collector](https://www.baeldung.com/jvm-epsilon-gc-garbage-collector)
 - [Guide to jlink](https://www.baeldung.com/jlink)
+- [Transforming an Empty String into an Empty Optional](https://www.baeldung.com/java-empty-string-to-empty-optional)

core-java-modules/core-java-12/src/test/java/com/baeldung/string/StringAPITest.java

@@ -0,0 +1,43 @@
+package com.baeldung.string;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class StringAPITest {
+
+    @Test
+    public void whenPositiveArgument_thenReturnIndentedString() {
+        String multilineStr = "This is\na multiline\nstring.";
+        String outputStr = "   This is\n   a multiline\n   string.\n";
+
+        String postIndent = multilineStr.indent(3);
+
+        assertThat(postIndent, equalTo(outputStr));
+    }
+
+    @Test
+    public void whenNegativeArgument_thenReturnReducedIndentedString() {
+        String multilineStr = "   This is\n   a multiline\n   string.";
+        String outputStr = " This is\n a multiline\n string.\n";
+
+        String postIndent = multilineStr.indent(-2);
+
+        assertThat(postIndent, equalTo(outputStr));
+    }
+
+    @Test
+    public void whenTransformUsingLamda_thenReturnTransformedString() {
+        String result = "hello".transform(input -> input + " world!");
+
+        assertThat(result, equalTo("hello world!"));
+    }
+
+    @Test
+    public void whenTransformUsingParseInt_thenReturnInt() {
+        int result = "42".transform(Integer::parseInt);
+
+        assertThat(result, equalTo(42));
+    }
+}

core-java-modules/core-java-8-2/README.md

@@ -3,4 +3,5 @@
 ## Core Java 8 Cookbooks and Examples (part 2)
 
 ### Relevant Articles: 
-- [Anonymous Classes in Java](http://www.baeldung.com/)
+- [Anonymous Classes in Java](https://www.baeldung.com/java-anonymous-classes)
+- [Run JAR Application With Command Line Arguments](https://www.baeldung.com/java-run-jar-with-arguments)

core-java-modules/core-java-8/src/test/java/com/baeldung/java8/optional/OptionalChainingUnitTest.java

@@ -101,7 +101,7 @@ public class OptionalChainingUnitTest {
     }
 
     private Optional<String> createOptional(String input) {
-        if (input == null || input == "" || input == "empty") {
+        if (input == null || "".equals(input) || "empty".equals(input)) {
             return Optional.empty();
         }
 

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

@@ -20,6 +20,14 @@
 - [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)
 - [Ahead of Time Compilation (AoT)](https://www.baeldung.com/ahead-of-time-compilation)
 - [Java 9 Process API Improvements](https://www.baeldung.com/java-9-process-api)
-- [Guide to java.lang.Process API](https://www.baeldung.com/java-process-api)
-
-
+- [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
+- [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)
+- [Java 9 Optional API Additions](https://www.baeldung.com/java-9-optional)
+- [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)
+- [Introduction to Java 9 StackWalking API](https://www.baeldung.com/java-9-stackwalking-api)
+- [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
+- [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
+- [A Guide to Java 9 Modularity](https://www.baeldung.com/java-9-modularity)
+- [Java 9 Platform Module API](https://www.baeldung.com/java-9-module-api)
+- [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
+- [Filtering a Stream of Optionals in Java](https://www.baeldung.com/java-filter-stream-of-optional)

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

@@ -8,4 +8,5 @@
 - [A Guide to HashSet in Java](http://www.baeldung.com/java-hashset)
 - [A Guide to TreeSet in Java](http://www.baeldung.com/java-tree-set)
 - [Initializing HashSet at the Time of Construction](http://www.baeldung.com/java-initialize-hashset)
-- [Guide to EnumSet](https://www.baeldung.com/java-enumset)
+- [Guide to EnumSet](https://www.baeldung.com/java-enumset)
+- [Set Operations in Java](https://www.baeldung.com/java-set-operations)

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

@@ -0,0 +1,26 @@
+<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>
+    <groupId>com.baeldung.exception.numberformat</groupId>
+    <artifactId>core-java-exceptions</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>core-java-exceptions</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>

core-java-modules/core-java-exceptions/src/test/java/com/baeldung/exception/numberformat/NumberFormatExceptionUnitTest.java

@@ -0,0 +1,154 @@
+package com.baeldung.exception.numberformat;
+
+import static org.junit.Assert.assertEquals;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.text.NumberFormat;
+import java.text.ParseException;
+import java.util.Locale;
+import java.util.logging.Logger;
+
+import org.junit.Test;
+
+/**
+ * A set of examples tested to show cases where NumberFormatException is thrown and not thrown.
+ */
+public class NumberFormatExceptionUnitTest {
+
+    Logger LOG = Logger.getLogger(NumberFormatExceptionUnitTest.class.getName());
+
+    /* ---INTEGER FAIL CASES--- */
+    @Test(expected = NumberFormatException.class)
+    public void givenByteConstructor_whenAlphabetAsInput_thenFail() {
+        Byte byteInt = new Byte("one");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenShortConstructor_whenSpaceInInput_thenFail() {
+        Short shortInt = new Short("2 ");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenParseIntMethod_whenSpaceInInput_thenFail() {
+        Integer aIntPrim = Integer.parseInt("6000 ");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenParseIntMethod_whenUnderscoreInInput_thenFail() {
+        int bIntPrim = Integer.parseInt("6_000");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenIntegerValueOfMethod_whenCommaInInput_thenFail() {
+        Integer cIntPrim = Integer.valueOf("6,000");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenBigIntegerConstructor_whenDecimalInInput_thenFail() {
+        BigInteger bigInteger = new BigInteger("4.0");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenDecodeMethod_whenAlphabetInInput_thenFail() {
+        Long decodeInteger = Long.decode("64403L");
+    }
+
+    /* ---INTEGER PASS CASES--- */
+    @Test
+    public void givenInvalidNumberInputs_whenOptimized_thenPass() {
+        Byte byteInt = new Byte("1");
+        assertEquals(1, byteInt.intValue());
+
+        Short shortInt = new Short("2 ".trim());
+        assertEquals(2, shortInt.intValue());
+
+        Integer aIntObj = Integer.valueOf("6");
+        assertEquals(6, aIntObj.intValue());
+
+        BigInteger bigInteger = new BigInteger("4");
+        assertEquals(4, bigInteger.intValue());
+
+        int aIntPrim = Integer.parseInt("6000 ".trim());
+        assertEquals(6000, aIntPrim);
+
+        int bIntPrim = Integer.parseInt("6_000".replaceAll("_", ""));
+        assertEquals(6000, bIntPrim);
+
+        int cIntPrim = Integer.parseInt("-6000");
+        assertEquals(-6000, cIntPrim);
+
+        Long decodeInteger = Long.decode("644032334");
+        assertEquals(644032334L, decodeInteger.longValue());
+    }
+
+    /* ---DOUBLE FAIL CASES--- */
+    @Test(expected = NumberFormatException.class)
+    public void givenFloatConstructor_whenAlphabetInInput_thenFail() {
+        Float floatDecimalObj = new Float("one.1");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenDoubleConstructor_whenAlphabetInInput_thenFail() {
+        Double doubleDecimalObj = new Double("two.2");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenBigDecimalConstructor_whenSpecialCharsInInput_thenFail() {
+        BigDecimal bigDecimalObj = new BigDecimal("3_0.3");
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenParseDoubleMethod_whenCommaInInput_thenFail() {
+        double aDoublePrim = Double.parseDouble("4000,1");
+    }
+
+    /* ---DOUBLE PASS CASES--- */
+    @Test
+    public void givenDoubleConstructor_whenDecimalInInput_thenPass() {
+        Double doubleDecimalObj = new Double("2.2");
+        assertEquals(2.2, doubleDecimalObj.doubleValue(), 0);
+    }
+
+    @Test
+    public void givenDoubleValueOfMethod_whenMinusInInput_thenPass() {
+        Double aDoubleObj = Double.valueOf("-6000");
+        assertEquals(-6000, aDoubleObj.doubleValue(), 0);
+    }
+
+    @Test
+    public void givenUsDecimalNumber_whenParsedWithNumberFormat_thenPass() throws ParseException {
+        Number parsedNumber = parseNumberWithLocale("4000.1", Locale.US);
+        assertEquals(4000.1, parsedNumber);
+        assertEquals(4000.1, parsedNumber.doubleValue(), 0);
+        assertEquals(4000, parsedNumber.intValue());
+    }
+
+    /**
+     * In most European countries (for example, France), comma is used as decimal in place of period.
+     * @throws ParseException if the input string contains special characters other than comma or decimal. 
+     * In this test case, anything after decimal (period) is dropped when a European locale is set.
+     */
+    @Test
+    public void givenEuDecimalNumberHasComma_whenParsedWithNumberFormat_thenPass() throws ParseException {
+        Number parsedNumber = parseNumberWithLocale("4000,1", Locale.FRANCE);
+        LOG.info("Number parsed is: " + parsedNumber);
+        assertEquals(4000.1, parsedNumber);
+        assertEquals(4000.1, parsedNumber.doubleValue(), 0);
+        assertEquals(4000, parsedNumber.intValue());
+    }
+
+    /**
+     * Converts a string into a number retaining all decimals, and symbols valid in a locale.
+     * @param number the input string for a number.
+     * @param locale the locale to consider while parsing a number.
+     * @return the generic number object which can represent multiple number types.
+     * @throws ParseException when input contains invalid characters.
+     */
+    private Number parseNumberWithLocale(String number, Locale locale) throws ParseException {
+        locale = locale == null ? Locale.getDefault() : locale;
+        NumberFormat numberFormat = NumberFormat.getInstance(locale);
+        return numberFormat.parse(number);
+    }
+
+}

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

@@ -40,3 +40,4 @@
 - [How to Write to a CSV File in Java](https://www.baeldung.com/java-csv)
 - [List Files in a Directory in Java](https://www.baeldung.com/java-list-directory-files)
 - [Java InputStream to Byte Array and ByteBuffer](https://www.baeldung.com/convert-input-stream-to-array-of-bytes)
+- [Introduction to the Java NIO Selector](https://www.baeldung.com/java-nio-selector)

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

@@ -4,3 +4,5 @@
 
 ### Relevant Articles: 
 - [Generic Constructors in Java](https://www.baeldung.com/java-generic-constructors)
+- [Cannot Reference “X” Before Supertype Constructor Has Been Called](https://www.baeldung.com/java-cannot-reference-x-before-supertype-constructor-error)
+- [Anonymous Classes in Java](https://www.baeldung.com/java-anonymous-classes)

core-java-modules/core-java-reflection/README.MD

@@ -0,0 +1,3 @@
+## Relevant Articles
+
+- [Void Type in Java](https://www.baeldung.com/java-void-type)

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

@@ -51,3 +51,4 @@
 - [Java Bitwise Operators](https://www.baeldung.com/java-bitwise-operators)
 - [Guide to Creating and Running a Jar File in Java](https://www.baeldung.com/java-create-jar)
 - [Making a JSON POST Request With HttpURLConnection](https://www.baeldung.com/httpurlconnection-post)
+- [Convert Hex to ASCII in Java](https://www.baeldung.com/java-convert-hex-to-ascii)

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

@@ -454,7 +454,7 @@
         <gson.version>2.8.2</gson.version>
 
         <!-- util -->
-        <commons-lang3.version>3.5</commons-lang3.version>
+        <commons-lang3.version>3.9</commons-lang3.version>
         <commons-io.version>2.5</commons-io.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <decimal4j.version>1.0.3</decimal4j.version>

core-java-modules/core-java/src/main/java/com/baeldung/exceptions/RootCauseFinder.java

@@ -30,7 +30,7 @@ public class RootCauseFinder {
         private AgeCalculator() {
         }
 
-        public static int calculateAge(String birthDate) throws CalculationException {
+        public static int calculateAge(String birthDate) {
             if (birthDate == null || birthDate.isEmpty()) {
                 throw new IllegalArgumentException();
             }
@@ -44,7 +44,7 @@ public class RootCauseFinder {
             }
         }
 
-        private static LocalDate parseDate(String birthDateAsString) throws DateParseException {
+        private static LocalDate parseDate(String birthDateAsString) {
 
             LocalDate birthDate;
             try {
@@ -62,14 +62,14 @@ public class RootCauseFinder {
 
     }
 
-    static class CalculationException extends Exception {
+    static class CalculationException extends RuntimeException {
 
         CalculationException(DateParseException ex) {
             super(ex);
         }
     }
 
-    static class DateParseException extends Exception {
+    static class DateParseException extends RuntimeException {
 
         DateParseException(String input) {
             super(input);

core-java-modules/pom.xml

@@ -15,6 +15,7 @@
 
     <modules>
         <module>pre-jpms</module>
+        <module>core-java-exceptions</module>
     </modules>
     
 </project>

core-java-modules/pre-jpms/README.MD

@@ -0,0 +1,3 @@
+## Relevant Articles
+
+- [Java 9 Migration Issues and Resolutions](https://www.baeldung.com/java-9-migration-issue)

core-kotlin-2/README.md

@@ -6,4 +6,5 @@
 - [Kotlin Scope Functions](https://www.baeldung.com/kotlin-scope-functions)
 - [Kotlin Annotations](https://www.baeldung.com/kotlin-annotations)
 - [Split a List into Parts in Kotlin](https://www.baeldung.com/kotlin-split-list-into-parts)
-- [String Comparison in Kotlin](https://www.baeldung.com/kotlin-string-comparison)
+- [String Comparison in Kotlin](https://www.baeldung.com/kotlin-string-comparison)
+- [Guide to JVM Platform Annotations in Kotlin](https://www.baeldung.com/kotlin-jvm-annotations)