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-java/pom.xml

@@ -1,492 +0,0 @@
-<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</artifactId>
-    <version>0.1.0-SNAPSHOT</version>
-    <name>core-java</name>
-    <packaging>jar</packaging>
-
-    <parent>
-        <groupId>com.baeldung</groupId>
-        <artifactId>parent-java</artifactId>
-        <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-java</relativePath>
-    </parent>
-
-
-    <dependencies>
-        <dependency>
-            <groupId>commons-io</groupId>
-            <artifactId>commons-io</artifactId>
-            <version>${commons-io.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${commons-lang3.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.unix4j</groupId>
-            <artifactId>unix4j-command</artifactId>
-            <version>${unix4j.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.googlecode.grep4j</groupId>
-            <artifactId>grep4j</artifactId>
-            <version>${grep4j.version}</version>
-        </dependency>
-        <!-- web -->
-        <!-- marshalling -->
-        <dependency>
-            <groupId>com.fasterxml.jackson.core</groupId>
-            <artifactId>jackson-databind</artifactId>
-            <version>${jackson.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.google.code.gson</groupId>
-            <artifactId>gson</artifactId>
-            <version>${gson.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>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
-        <!-- test scoped -->
-        <dependency>
-            <groupId>org.assertj</groupId>
-            <artifactId>assertj-core</artifactId>
-            <version>${assertj-core.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.javamoney</groupId>
-            <artifactId>moneta</artifactId>
-            <version>${javamoney.moneta.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.owasp.esapi</groupId>
-            <artifactId>esapi</artifactId>
-            <version>${esapi.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.sun.messaging.mq</groupId>
-            <artifactId>fscontext</artifactId>
-            <version>${fscontext.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.codepoetics</groupId>
-            <artifactId>protonpack</artifactId>
-            <version>${protonpack.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>one.util</groupId>
-            <artifactId>streamex</artifactId>
-            <version>${streamex.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>io.vavr</groupId>
-            <artifactId>vavr</artifactId>
-            <version>${vavr.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-core</artifactId>
-            <version>${jmh-core.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-annprocess</artifactId>
-            <version>${jmh-generator-annprocess.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.h2database</groupId>
-            <artifactId>h2</artifactId>
-            <version>${h2database.version}</version>
-        </dependency>
-        <!-- instrumentation -->
-        <dependency>
-            <groupId>org.javassist</groupId>
-            <artifactId>javassist</artifactId>
-            <version>${javaassist.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.sun</groupId>
-            <artifactId>tools</artifactId>
-            <version>${sun.tools.version}</version>
-            <scope>system</scope>
-            <systemPath>${java.home}/../lib/tools.jar</systemPath>
-        </dependency>
-    </dependencies>
-
-    <build>
-        <finalName>core-java</finalName>
-        <resources>
-            <resource>
-                <directory>src/main/resources</directory>
-                <filtering>true</filtering>
-            </resource>
-        </resources>
-
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-dependency-plugin</artifactId>
-                <executions>
-                    <execution>
-                        <id>copy-dependencies</id>
-                        <phase>prepare-package</phase>
-                        <goals>
-                            <goal>copy-dependencies</goal>
-                        </goals>
-                        <configuration>
-                            <outputDirectory>${project.build.directory}/libs</outputDirectory>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-jar-plugin</artifactId>
-                <version>${maven-jar-plugin.version}</version>
-                <configuration>
-                    <archive>
-                        <manifest>
-                            <addClasspath>true</addClasspath>
-                            <classpathPrefix>libs/</classpathPrefix>
-                            <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
-                        </manifest>
-                    </archive>
-                </configuration>
-            </plugin>
-
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-assembly-plugin</artifactId>
-                <executions>
-                    <execution>
-                        <phase>package</phase>
-                        <goals>
-                            <goal>single</goal>
-                        </goals>
-                        <configuration>
-                            <archiveBaseDirectory>${project.basedir}</archiveBaseDirectory>
-                            <archive>
-                                <manifest>
-                                    <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
-                                </manifest>
-                            </archive>
-                            <descriptorRefs>
-                                <descriptorRef>jar-with-dependencies</descriptorRef>
-                            </descriptorRefs>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-shade-plugin</artifactId>
-                <version>${maven-shade-plugin.version}</version>
-                <executions>
-                    <execution>
-                        <goals>
-                            <goal>shade</goal>
-                        </goals>
-                        <configuration>
-                            <shadedArtifactAttached>true</shadedArtifactAttached>
-                            <transformers>
-                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
-                                    <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
-                                </transformer>
-                            </transformers>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-
-            <plugin>
-                <groupId>com.jolira</groupId>
-                <artifactId>onejar-maven-plugin</artifactId>
-                <version>${onejar-maven-plugin.version}</version>
-                <executions>
-                    <execution>
-                        <configuration>
-                            <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
-                            <attachToBuild>true</attachToBuild>
-                            <filename>${project.build.finalName}-onejar.${project.packaging}</filename>
-                        </configuration>
-                        <goals>
-                            <goal>one-jar</goal>
-                        </goals>
-                    </execution>
-                </executions>
-            </plugin>
-
-            <plugin>
-                <groupId>org.springframework.boot</groupId>
-                <artifactId>spring-boot-maven-plugin</artifactId>
-                <version>${spring-boot-maven-plugin.version}</version>
-                <executions>
-                    <execution>
-                        <goals>
-                            <goal>repackage</goal>
-                        </goals>
-                        <configuration>
-                            <classifier>spring-boot</classifier>
-                            <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-
-            <plugin>
-                <groupId>org.codehaus.mojo</groupId>
-                <artifactId>exec-maven-plugin</artifactId>
-                <version>${exec-maven-plugin.version}</version>
-                <configuration>
-                    <executable>java</executable>
-                    <mainClass>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</mainClass>
-                    <arguments>
-                        <argument>-Xmx300m</argument>
-                        <argument>-XX:+UseParallelGC</argument>
-                        <argument>-classpath</argument>
-                        <classpath />
-                        <argument>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</argument>
-                    </arguments>
-                </configuration>
-            </plugin>
-            
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-javadoc-plugin</artifactId>
-                <version>${maven-javadoc-plugin.version}</version>
-                <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
-
-    <profiles>
-        <profile>
-            <id>integration</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-surefire-plugin</artifactId>
-                        <executions>
-                            <execution>
-                                <phase>integration-test</phase>
-                                <goals>
-                                    <goal>test</goal>
-                                </goals>
-                                <configuration>
-                                    <excludes>
-                                        <exclude>**/*ManualTest.java</exclude>
-                                    </excludes>
-                                    <includes>
-                                        <include>**/*IntegrationTest.java</include>
-                                        <include>**/*IntTest.java</include>
-                                    </includes>
-                                </configuration>
-                            </execution>
-                        </executions>
-                        <configuration>
-                            <systemPropertyVariables>
-                                <test.mime>json</test.mime>
-                            </systemPropertyVariables>
-                        </configuration>
-                    </plugin>
-                    <plugin>
-                        <groupId>org.codehaus.mojo</groupId>
-                        <artifactId>exec-maven-plugin</artifactId>
-                        <version>${exec-maven-plugin.version}</version>
-                        <executions>
-                            <execution>
-                                <id>run-benchmarks</id>
-                                <!-- <phase>integration-test</phase> -->
-                                <phase>none</phase>
-                                <goals>
-                                    <goal>exec</goal>
-                                </goals>
-                                <configuration>
-                                    <classpathScope>test</classpathScope>
-                                    <executable>java</executable>
-                                    <arguments>
-                                        <argument>-classpath</argument>
-                                        <classpath />
-                                        <argument>org.openjdk.jmh.Main</argument>
-                                        <argument>.*</argument>
-                                    </arguments>
-                                </configuration>
-                            </execution>
-                        </executions>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
-
-        <!-- java instrumentation profiles to build jars -->
-        <profile>
-            <id>buildAgentLoader</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-jar-plugin</artifactId>
-                        <executions>
-                            <execution>
-                                <phase>package</phase>
-                                <goals>
-                                    <goal>jar</goal>
-                                </goals>
-                                <configuration>
-                                    <classifier>agentLoader</classifier>
-                                    <classesDirectory>target/classes</classesDirectory>
-                                    <archive>
-                                        <manifest>
-                                            <addClasspath>true</addClasspath>
-                                        </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
-                                    </archive>
-
-                                    <includes>
-                                        <include>com/baeldung/instrumentation/application/AgentLoader.class</include>
-                                        <include>com/baeldung/instrumentation/application/Launcher.class</include>
-                                    </includes>
-                                </configuration>
-                            </execution>
-                        </executions>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
-        <profile>
-            <id>buildApplication</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-jar-plugin</artifactId>
-                        <executions>
-                            <execution>
-                                <phase>package</phase>
-                                <goals>
-                                    <goal>jar</goal>
-                                </goals>
-                                <configuration>
-                                    <classifier>application</classifier>
-                                    <classesDirectory>target/classes</classesDirectory>
-                                    <archive>
-                                        <manifest>
-                                            <addClasspath>true</addClasspath>
-                                        </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
-                                    </archive>
-
-                                    <includes>
-                                        <include>com/baeldung/instrumentation/application/MyAtm.class</include>
-                                        <include>com/baeldung/instrumentation/application/MyAtmApplication.class</include>
-                                        <include>com/baeldung/instrumentation/application/Launcher.class</include>
-                                    </includes>
-                                </configuration>
-                            </execution>
-                        </executions>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
-        <profile>
-            <id>buildAgent</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-jar-plugin</artifactId>
-                        <executions>
-                            <execution>
-                                <phase>package</phase>
-                                <goals>
-                                    <goal>jar</goal>
-                                </goals>
-                                <configuration>
-                                    <classifier>agent</classifier>
-                                    <classesDirectory>target/classes</classesDirectory>
-                                    <archive>
-                                        <manifest>
-                                            <addClasspath>true</addClasspath>
-                                        </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
-                                    </archive>
-
-                                    <includes>
-                                        <include>com/baeldung/instrumentation/agent/AtmTransformer.class</include>
-                                        <include>com/baeldung/instrumentation/agent/MyInstrumentationAgent.class</include>
-                                    </includes>
-                                </configuration>
-                            </execution>
-                        </executions>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
-    </profiles>
-
-    <properties>
-        
-        <!-- marshalling -->
-        <gson.version>2.8.2</gson.version>
-
-        <!-- util -->
-        <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>
-        <unix4j.version>0.4</unix4j.version>
-        <grep4j.version>1.8.7</grep4j.version>
-        <fscontext.version>4.6-b01</fscontext.version>
-        <protonpack.version>1.13</protonpack.version>
-        <streamex.version>0.6.5</streamex.version>
-        <vavr.version>0.9.0</vavr.version>
-
-        <!-- testing -->
-        <assertj-core.version>3.10.0</assertj-core.version>
-
-        <!-- maven plugins -->
-        <maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
-        
-        <javamoney.moneta.version>1.1</javamoney.moneta.version>
-        <h2database.version>1.4.197</h2database.version>
-        <esapi.version>2.1.0.1</esapi.version>
-        <jmh-core.version>1.19</jmh-core.version>
-       
-        <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>
-        <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
-        <maven-jar-plugin.version>3.0.2</maven-jar-plugin.version>
-        <onejar-maven-plugin.version>1.4.4</onejar-maven-plugin.version>
-        <maven-shade-plugin.version>3.1.1</maven-shade-plugin.version>
-        <spring-boot-maven-plugin.version>2.0.3.RELEASE</spring-boot-maven-plugin.version>
-        <exec-maven-plugin.version>1.6.0</exec-maven-plugin.version>
-        <icu4j.version>61.1</icu4j.version>
-        <!-- instrumentation -->
-        <javaassist.version>3.21.0-GA</javaassist.version>
-        
-        <sun.tools.version>1.8.0</sun.tools.version>
-    </properties>
-</project>

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)

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/AmountBasedDiscountPolicy.java

@@ -0,0 +1,15 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import org.joda.money.CurrencyUnit;
+import org.joda.money.Money;
+
+public class AmountBasedDiscountPolicy implements DiscountPolicy {
+    @Override
+    public double discount(Order order) {
+        if (order.totalCost()
+            .isGreaterThan(Money.of(CurrencyUnit.USD, 500.00))) {
+            return 0.10;
+        } else
+            return 0;
+    }
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/DiscountPolicy.java

@@ -0,0 +1,5 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+public interface DiscountPolicy {
+    double discount(Order order);
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/FlatDiscountPolicy.java

@@ -0,0 +1,8 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+public class FlatDiscountPolicy implements DiscountPolicy {
+    @Override
+    public double discount(Order order) {
+        return 0.01;
+    }
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/Order.java

@@ -0,0 +1,29 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import java.math.RoundingMode;
+import java.util.List;
+
+import org.joda.money.Money;
+
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.visitor.OrderVisitor;
+import com.baeldung.ddd.order.doubledispatch.visitor.Visitable;
+
+public class Order extends com.baeldung.ddd.order.Order implements Visitable<OrderVisitor> {
+    public Order(List<OrderLine> orderLines) {
+        super(orderLines);        
+    }
+
+    public Money totalCost(SpecialDiscountPolicy discountPolicy) {
+        return totalCost().multipliedBy(1 - applyDiscountPolicy(discountPolicy), RoundingMode.HALF_UP);
+    }
+
+    protected double applyDiscountPolicy(SpecialDiscountPolicy discountPolicy) {
+        return discountPolicy.discount(this);
+    }
+    
+    @Override
+    public void accept(OrderVisitor visitor) {
+        visitor.visit(this);        
+    }
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/SpecialDiscountPolicy.java

@@ -0,0 +1,5 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+public interface SpecialDiscountPolicy extends DiscountPolicy {
+    double discount(SpecialOrder order);
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/SpecialOrder.java

@@ -0,0 +1,36 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import java.util.List;
+
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.visitor.OrderVisitor;
+
+public class SpecialOrder extends Order {
+
+    private boolean eligibleForExtraDiscount;
+
+    public SpecialOrder(List<OrderLine> orderLines) {
+        super(orderLines);
+        this.eligibleForExtraDiscount = false;
+    }
+
+    public SpecialOrder(List<OrderLine> orderLines, boolean eligibleForSpecialDiscount) {
+        super(orderLines);
+        this.eligibleForExtraDiscount = eligibleForSpecialDiscount;
+    }
+
+    public boolean isEligibleForExtraDiscount() {
+        return eligibleForExtraDiscount;
+    }
+
+    @Override
+    protected double applyDiscountPolicy(SpecialDiscountPolicy discountPolicy) {
+        return discountPolicy.discount(this);
+    }
+
+    @Override
+    public void accept(OrderVisitor visitor) {
+        visitor.visit(this);
+    }
+
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/visitor/HtmlOrderViewCreator.java

@@ -0,0 +1,24 @@
+package com.baeldung.ddd.order.doubledispatch.visitor;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.doubledispatch.SpecialOrder;
+
+public class HtmlOrderViewCreator implements OrderVisitor {
+    
+    private String html;
+    
+    public String getHtml() {
+        return html;
+    }
+
+    @Override
+    public void visit(Order order) {
+        html = String.format("<p>Regular order total cost: %s</p>", order.totalCost());
+    }
+
+    @Override
+    public void visit(SpecialOrder order) {
+        html = String.format("<h1>Special Order</h1><p>total cost: %s</p>", order.totalCost());
+    }
+
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/visitor/OrderVisitor.java

@@ -0,0 +1,9 @@
+package com.baeldung.ddd.order.doubledispatch.visitor;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.doubledispatch.SpecialOrder;
+
+public interface OrderVisitor {
+    void visit(Order order);
+    void visit(SpecialOrder order);
+}

ddd/src/main/java/com/baeldung/ddd/order/doubledispatch/visitor/Visitable.java

@@ -0,0 +1,5 @@
+package com.baeldung.ddd.order.doubledispatch.visitor;
+
+public interface Visitable<V> {
+    void accept(V visitor);
+}

ddd/src/main/java/com/baeldung/ddd/order/jpa/JpaOrder.java

@@ -92,7 +92,7 @@ class JpaOrder {
     }
 
     void removeLineItem(int line) {
-        JpaOrderLine removedLine = orderLines.remove(line);
+        orderLines.remove(line);
     }
 
     void setCurrencyUnit(String currencyUnit) {

ddd/src/main/java/com/baeldung/ddd/order/jpa/JpaProduct.java

@@ -15,7 +15,7 @@ class JpaProduct {
     public JpaProduct(BigDecimal price, String currencyUnit) {
         super();
         this.price = price;
-        currencyUnit = currencyUnit;
+        this.currencyUnit = currencyUnit;
     }
 
     @Override

ddd/src/test/java/com/baeldung/ddd/order/OrderFixtureUtils.java

@@ -0,0 +1,17 @@
+package com.baeldung.ddd.order;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.joda.money.CurrencyUnit;
+import org.joda.money.Money;
+
+public class OrderFixtureUtils {
+    public static List<OrderLine> anyOrderLines() {
+        return Arrays.asList(new OrderLine(new Product(Money.of(CurrencyUnit.USD, 100)), 1));
+    }
+
+    public static List<OrderLine> orderLineItemsWorthNDollars(int totalCost) {
+        return Arrays.asList(new OrderLine(new Product(Money.of(CurrencyUnit.USD, totalCost)), 1));
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/DoubleDispatchDiscountPolicyUnitTest.java

@@ -0,0 +1,77 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.joda.money.CurrencyUnit;
+import org.joda.money.Money;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.OrderFixtureUtils;
+
+public class DoubleDispatchDiscountPolicyUnitTest {
+    // @formatter:off
+    @DisplayName(
+        "given regular order with items worth $100 total, " +
+        "when apply 10% discount policy, " +
+        "then cost after discount is $90"
+        )
+    // @formatter:on
+    @Test
+    void test() throws Exception {
+        // given
+        Order order = new Order(OrderFixtureUtils.orderLineItemsWorthNDollars(100));
+        SpecialDiscountPolicy discountPolicy = new SpecialDiscountPolicy() {
+
+            @Override
+            public double discount(Order order) {
+                return 0.10;
+            }
+
+            @Override
+            public double discount(SpecialOrder order) {
+                return 0;
+            }
+        };
+
+        // when
+        Money totalCostAfterDiscount = order.totalCost(discountPolicy);
+
+        // then
+        assertThat(totalCostAfterDiscount).isEqualTo(Money.of(CurrencyUnit.USD, 90));
+    }
+
+    // @formatter:off
+    @DisplayName(
+        "given special order eligible for extra discount with items worth $100 total, " +
+        "when apply 20% discount policy for extra discount orders, " +
+        "then cost after discount is $80"
+        )
+    // @formatter:on
+    @Test
+    void test1() throws Exception {
+        // given
+        boolean eligibleForExtraDiscount = true;
+        Order order = new SpecialOrder(OrderFixtureUtils.orderLineItemsWorthNDollars(100), eligibleForExtraDiscount);
+        SpecialDiscountPolicy discountPolicy = new SpecialDiscountPolicy() {
+
+            @Override
+            public double discount(Order order) {
+                return 0;
+            }
+
+            @Override
+            public double discount(SpecialOrder order) {
+                if (order.isEligibleForExtraDiscount())
+                    return 0.20;
+                return 0.10;
+            }
+        };
+
+        // when
+        Money totalCostAfterDiscount = order.totalCost(discountPolicy);
+
+        // then
+        assertThat(totalCostAfterDiscount).isEqualTo(Money.of(CurrencyUnit.USD, 80.00));
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/HtmlOrderViewCreatorUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.OrderFixtureUtils;
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.visitor.HtmlOrderViewCreator;
+
+public class HtmlOrderViewCreatorUnitTest {
+    // @formatter:off 
+    @DisplayName(
+            "given collection of regular and special orders, " +
+            "when create HTML view using visitor for each order, " +
+            "then the dedicated view is created for each order"   
+        )
+    // @formatter:on
+    @Test
+    void test() throws Exception {
+        // given
+        List<OrderLine> anyOrderLines = OrderFixtureUtils.anyOrderLines();
+        List<Order> orders = Arrays.asList(new Order(anyOrderLines), new SpecialOrder(anyOrderLines));
+        HtmlOrderViewCreator htmlOrderViewCreator = new HtmlOrderViewCreator();
+
+        // when
+        orders.get(0)
+            .accept(htmlOrderViewCreator);
+        String regularOrderHtml = htmlOrderViewCreator.getHtml();
+        orders.get(1)
+            .accept(htmlOrderViewCreator);
+        String specialOrderHtml = htmlOrderViewCreator.getHtml();
+
+        // then
+        assertThat(regularOrderHtml).containsPattern("<p>Regular order total cost: .*</p>");
+        assertThat(specialOrderHtml).containsPattern("<h1>Special Order</h1><p>total cost: .*</p>");
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/MethodOverloadExampleUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.doubledispatch.Order;
+import com.baeldung.ddd.order.OrderFixtureUtils;
+import com.baeldung.ddd.order.OrderLine;
+import com.baeldung.ddd.order.doubledispatch.SpecialDiscountPolicy;
+import com.baeldung.ddd.order.doubledispatch.SpecialOrder;
+
+public class MethodOverloadExampleUnitTest {
+// @formatter:off
+@DisplayName(
+    "given discount policy accepting special orders, " +
+    "when apply the policy on special order declared as regular order, " +
+    "then regular discount method is used"
+    )
+// @formatter:on    
+    @Test
+    void test() throws Exception {
+        // given
+        SpecialDiscountPolicy specialPolicy = new SpecialDiscountPolicy() {
+            @Override
+            public double discount(Order order) {
+                return 0.01;
+            }
+
+            @Override
+            public double discount(SpecialOrder order) {
+                return 0.10;
+            }
+        };
+        Order specialOrder = new SpecialOrder(anyOrderLines());
+
+        // when
+        double discount = specialPolicy.discount(specialOrder);
+
+        // then
+        assertThat(discount).isEqualTo(0.01);
+    }
+
+    private List<OrderLine> anyOrderLines() {
+        return OrderFixtureUtils.anyOrderLines();
+    }
+}

ddd/src/test/java/com/baeldung/ddd/order/doubledispatch/SingleDispatchDiscountPolicyUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.ddd.order.doubledispatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.ddd.order.OrderFixtureUtils;
+
+public class SingleDispatchDiscountPolicyUnitTest {
+    // @formatter:off
+    @DisplayName(
+        "given two discount policies, " +
+        "when use these policies, " +
+        "then single dispatch chooses the implementation based on runtime type"
+        )
+    // @formatter:on    
+    @Test
+    void test() throws Exception {
+        // given
+        DiscountPolicy flatPolicy = new FlatDiscountPolicy();
+        DiscountPolicy amountPolicy = new AmountBasedDiscountPolicy();
+        Order orderWorth501Dollars = orderWorthNDollars(501);
+
+        // when
+        double flatDiscount = flatPolicy.discount(orderWorth501Dollars);
+        double amountDiscount = amountPolicy.discount(orderWorth501Dollars);
+
+        // then
+        assertThat(flatDiscount).isEqualTo(0.01);
+        assertThat(amountDiscount).isEqualTo(0.1);
+    }
+
+    private Order orderWorthNDollars(int totalCost) {
+        return new Order(OrderFixtureUtils.orderLineItemsWorthNDollars(totalCost));
+    }
+}

guava-collections-set/README.md

@@ -0,0 +1,8 @@
+# Guava
+
+## Relevant Articles:
+
+- [Guava – Sets](http://www.baeldung.com/guava-sets)
+- [Guide to Guava RangeSet](http://www.baeldung.com/guava-rangeset)
+- [Guava Set + Function = Map](http://www.baeldung.com/guava-set-function-map-tutorial)
+- [Guide to Guava Multiset](https://www.baeldung.com/guava-multiset)

guava-collections-set/src/test/java/org/baeldung/guava/GuavaMapFromSet.java

@@ -1,14 +1,9 @@
 package org.baeldung.guava;
 
-import java.util.AbstractMap;
-import java.util.AbstractSet;
-import java.util.Iterator;
-import java.util.Map;
-import java.util.Set;
-import java.util.WeakHashMap;
-
 import com.google.common.base.Function;
 
+import java.util.*;
+
 public class GuavaMapFromSet<K, V> extends AbstractMap<K, V> {
 
     private class SingleEntry implements Entry<K, V> {

guava-collections-set/src/test/java/org/baeldung/guava/GuavaMapFromSetUnitTest.java

@@ -1,15 +1,14 @@
 package org.baeldung.guava;
 
-import static org.junit.Assert.assertTrue;
+import com.google.common.base.Function;
+import org.junit.Test;
 
 import java.util.Arrays;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
 
-import org.junit.Test;
+import static org.junit.Assert.assertTrue;
-
-import com.google.common.base.Function;
 
 public class GuavaMapFromSetUnitTest {
 

guava-collections-set/src/test/java/org/baeldung/guava/GuavaRangeSetUnitTest.java

@@ -1,13 +1,12 @@
 package org.baeldung.guava;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.assertFalse;
-import org.junit.Test;
 import com.google.common.collect.ImmutableRangeSet;
 import com.google.common.collect.Range;
 import com.google.common.collect.RangeSet;
 import com.google.common.collect.TreeRangeSet;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
 
 public class GuavaRangeSetUnitTest {
 
@@ -122,6 +121,5 @@ public class GuavaRangeSetUnitTest {
 	    .add(Range.closed(0, 2))
 	    .add(Range.closed(3, 5))
 	    .add(Range.closed(5, 8)).build();
-
     }
 }

guava-collections-set/src/test/java/org/baeldung/guava/GuavaSetOperationsUnitTest.java

@@ -0,0 +1,131 @@
+package org.baeldung.guava;
+
+import com.google.common.base.Function;
+import com.google.common.base.Joiner;
+import com.google.common.collect.*;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Set;
+
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+public class GuavaSetOperationsUnitTest {
+
+    @Test
+    public void whenCalculatingUnionOfSets_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
+        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
+
+        final Set<Character> union = Sets.union(first, second);
+        assertThat(union, containsInAnyOrder('a', 'b', 'c', 'd'));
+    }
+
+    @Test
+    public void whenCalculatingCartesianProductOfSets_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b');
+        final Set<Character> second = ImmutableSet.of('c', 'd');
+        final Set<List<Character>> result = Sets.cartesianProduct(ImmutableList.of(first, second));
+
+        final Function<List<Character>, String> func = new Function<List<Character>, String>() {
+            @Override
+            public final String apply(final List<Character> input) {
+                return Joiner
+                  .on(" ").join(input);
+            }
+        };
+
+        final Iterable<String> joined = Iterables.transform(result, func);
+        assertThat(joined, containsInAnyOrder("a c", "a d", "b c", "b d"));
+    }
+
+    @Test
+    public void whenCalculatingSetIntersection_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
+        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
+
+        final Set<Character> intersection = Sets.intersection(first, second);
+        assertThat(intersection, containsInAnyOrder('b', 'c'));
+    }
+
+    @Test
+    public void whenCalculatingSetSymmetricDifference_thenCorrect() {
+        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
+        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
+
+        final Set<Character> intersection = Sets.symmetricDifference(first, second);
+        assertThat(intersection, containsInAnyOrder('a', 'd'));
+    }
+
+    @Test
+    public void whenCalculatingPowerSet_thenCorrect() {
+        final Set<Character> chars = ImmutableSet.of('a', 'b');
+        final Set<Set<Character>> result = Sets.powerSet(chars);
+
+        final Set<Character> empty = ImmutableSet.<Character> builder().build();
+        final Set<Character> a = ImmutableSet.of('a');
+        final Set<Character> b = ImmutableSet.of('b');
+        final Set<Character> aB = ImmutableSet.of('a', 'b');
+
+        assertThat(result, contains(empty, a, b, aB));
+    }
+
+    @Test
+    public void whenCreatingRangeOfIntegersSet_thenCreated() {
+        final int start = 10;
+        final int end = 30;
+        final ContiguousSet<Integer> set = ContiguousSet.create(Range.closed(start, end), DiscreteDomain.integers());
+
+        assertEquals(21, set.size());
+        assertEquals(10, set.first().intValue());
+        assertEquals(30, set.last().intValue());
+    }
+
+    @Test
+    public void whenUsingRangeSet_thenCorrect() {
+        final RangeSet<Integer> rangeSet = TreeRangeSet.create();
+        rangeSet.add(Range.closed(1, 10));
+        rangeSet.add(Range.closed(12, 15));
+
+        assertEquals(2, rangeSet.asRanges().size());
+
+        rangeSet.add(Range.closed(10, 12));
+        assertTrue(rangeSet.encloses(Range.closed(1, 15)));
+        assertEquals(1, rangeSet.asRanges().size());
+    }
+
+    @Test
+    public void whenInsertDuplicatesInMultiSet_thenInserted() {
+        final Multiset<String> names = HashMultiset.create();
+        names.add("John");
+        names.add("Adam", 3);
+        names.add("John");
+
+        assertEquals(2, names.count("John"));
+        names.remove("John");
+        assertEquals(1, names.count("John"));
+
+        assertEquals(3, names.count("Adam"));
+        names.remove("Adam", 2);
+        assertEquals(1, names.count("Adam"));
+    }
+
+    @Test
+    public void whenGetTopOcurringElementsWithMultiSet_thenCorrect() {
+        final Multiset<String> names = HashMultiset.create();
+        names.add("John");
+        names.add("Adam", 5);
+        names.add("Jane");
+        names.add("Tom", 2);
+
+        final Set<String> sorted = Multisets.copyHighestCountFirst(names).elementSet();
+        final List<String> topTwo = Lists.newArrayList(sorted).subList(0, 2);
+        assertEquals(2, topTwo.size());
+        assertEquals("Adam", topTwo.get(0));
+        assertEquals("Tom", topTwo.get(1));
+    }
+}

guava-collections/README.md

@@ -11,13 +11,10 @@
 - [Filtering and Transforming Collections in Guava](http://www.baeldung.com/guava-filter-and-transform-a-collection)
 - [Guava – Join and Split Collections](http://www.baeldung.com/guava-joiner-and-splitter-tutorial)
 - [Guava – Lists](http://www.baeldung.com/guava-lists)
-- [Guava – Sets](http://www.baeldung.com/guava-sets)
 - [Guava – Maps](http://www.baeldung.com/guava-maps)
 - [Guide to Guava Multimap](http://www.baeldung.com/guava-multimap)
-- [Guide to Guava RangeSet](http://www.baeldung.com/guava-rangeset)
 - [Guide to Guava RangeMap](http://www.baeldung.com/guava-rangemap)
 - [Guide to Guava MinMaxPriorityQueue and EvictingQueue](http://www.baeldung.com/guava-minmax-priority-queue-and-evicting-queue)
 - [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
-- [Guava Set + Function = Map](http://www.baeldung.com/guava-set-function-map-tutorial)
 - [Guide to Guava Table](http://www.baeldung.com/guava-table)
 - [Guide to Guava ClassToInstanceMap](http://www.baeldung.com/guava-class-to-instance-map)

guava-collections/src/test/java/org/baeldung/guava/GuavaCollectionTypesUnitTest.java

@@ -111,120 +111,6 @@ public class GuavaCollectionTypesUnitTest {
         assertThat(immutable, contains("John", "Adam", "Jane", "Tom"));
     }
 
-    // sets
-
-    @Test
-    public void whenCalculateUnionOfSets_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
-        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
-
-        final Set<Character> union = Sets.union(first, second);
-        assertThat(union, containsInAnyOrder('a', 'b', 'c', 'd'));
-    }
-
-    @Test
-    public void whenCalculateSetsProduct_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b');
-        final Set<Character> second = ImmutableSet.of('c', 'd');
-        final Set<List<Character>> result = Sets.cartesianProduct(ImmutableList.of(first, second));
-
-        final Function<List<Character>, String> func = new Function<List<Character>, String>() {
-            @Override
-            public final String apply(final List<Character> input) {
-                return Joiner.on(" ").join(input);
-            }
-        };
-
-        final Iterable<String> joined = Iterables.transform(result, func);
-        assertThat(joined, containsInAnyOrder("a c", "a d", "b c", "b d"));
-    }
-
-    @Test
-    public void whenCalculatingSetIntersection_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
-        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
-
-        final Set<Character> intersection = Sets.intersection(first, second);
-        assertThat(intersection, containsInAnyOrder('b', 'c'));
-    }
-
-    @Test
-    public void whenCalculatingSetSymmetricDifference_thenCorrect() {
-        final Set<Character> first = ImmutableSet.of('a', 'b', 'c');
-        final Set<Character> second = ImmutableSet.of('b', 'c', 'd');
-
-        final Set<Character> intersection = Sets.symmetricDifference(first, second);
-        assertThat(intersection, containsInAnyOrder('a', 'd'));
-    }
-
-    @Test
-    public void whenCalculatingPowerSet_thenCorrect() {
-        final Set<Character> chars = ImmutableSet.of('a', 'b');
-        final Set<Set<Character>> result = Sets.powerSet(chars);
-
-        final Set<Character> empty = ImmutableSet.<Character> builder().build();
-        final Set<Character> a = ImmutableSet.of('a');
-        final Set<Character> b = ImmutableSet.of('b');
-        final Set<Character> aB = ImmutableSet.of('a', 'b');
-
-        assertThat(result, contains(empty, a, b, aB));
-    }
-
-    @Test
-    public void whenCreateRangeOfIntegersSet_thenCreated() {
-        final int start = 10;
-        final int end = 30;
-        final ContiguousSet<Integer> set = ContiguousSet.create(Range.closed(start, end), DiscreteDomain.integers());
-
-        assertEquals(21, set.size());
-        assertEquals(10, set.first().intValue());
-        assertEquals(30, set.last().intValue());
-    }
-
-    @Test
-    public void whenCreateRangeSet_thenCreated() {
-        final RangeSet<Integer> rangeSet = TreeRangeSet.create();
-        rangeSet.add(Range.closed(1, 10));
-        rangeSet.add(Range.closed(12, 15));
-
-        assertEquals(2, rangeSet.asRanges().size());
-
-        rangeSet.add(Range.closed(10, 12));
-        assertTrue(rangeSet.encloses(Range.closed(1, 15)));
-        assertEquals(1, rangeSet.asRanges().size());
-    }
-
-    @Test
-    public void whenInsertDuplicatesInMultiSet_thenInserted() {
-        final Multiset<String> names = HashMultiset.create();
-        names.add("John");
-        names.add("Adam", 3);
-        names.add("John");
-
-        assertEquals(2, names.count("John"));
-        names.remove("John");
-        assertEquals(1, names.count("John"));
-
-        assertEquals(3, names.count("Adam"));
-        names.remove("Adam", 2);
-        assertEquals(1, names.count("Adam"));
-    }
-
-    @Test
-    public void whenGetTopUsingMultiSet_thenCorrect() {
-        final Multiset<String> names = HashMultiset.create();
-        names.add("John");
-        names.add("Adam", 5);
-        names.add("Jane");
-        names.add("Tom", 2);
-
-        final Set<String> sorted = Multisets.copyHighestCountFirst(names).elementSet();
-        final List<String> topTwo = Lists.newArrayList(sorted).subList(0, 2);
-        assertEquals(2, topTwo.size());
-        assertEquals("Adam", topTwo.get(0));
-        assertEquals("Tom", topTwo.get(1));
-    }
-
     @Test
     public void whenCreateImmutableMap_thenCreated() {
         final Map<String, Integer> salary = ImmutableMap.<String, Integer> builder().put("John", 1000).put("Jane", 1500).put("Adam", 2000).put("Tom", 2000).build();

jackson-2/README.md

@@ -7,4 +7,6 @@ The "REST With Spring" Classes: http://bit.ly/restwithspring
 
 ### Relevant Articles: 
 - [Mapping Multiple JSON Fields to a Single Java Field](https://www.baeldung.com/json-multiple-fields-single-java-field)
+- [How to Process YAML with Jackson](https://www.baeldung.com/jackson-yaml)
 - [Working with Tree Model Nodes in Jackson](https://www.baeldung.com/jackson-json-node-tree-model)
+

java-collections-maps-2/README.md

@@ -1,2 +1,3 @@
 ## Relevant Articles:
 - [Map of Primitives in Java](https://www.baeldung.com/java-map-primitives)
+- [Copying a HashMap in Java](https://www.baeldung.com/java-copy-hashmap)

java-dates-2/README.md

@@ -1,2 +1,3 @@
 ## Relevant Articles:
 - [Converting Between LocalDate and XMLGregorianCalendar](https://www.baeldung.com/java-localdate-to-xmlgregoriancalendar)
+- [Convert Time to Milliseconds in Java](https://www.baeldung.com/java-time-milliseconds)

java-strings-2/README.MD

@@ -0,0 +1,4 @@
+## Relevant Articles
+
+- [Java Localization – Formatting Messages](https://www.baeldung.com/java-localization-messages-formatting)
+- [Check If a String Contains a Substring](https://www.baeldung.com/java-string-contains-substring)

java-strings-2/pom.xml

@@ -15,28 +15,6 @@
     </parent>
 
     <dependencies>
-        <dependency>
-            <groupId>commons-io</groupId>
-            <artifactId>commons-io</artifactId>
-            <version>${commons-io.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>log4j</groupId>
-            <artifactId>log4j</artifactId>
-            <version>${log4j.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>commons-codec</groupId>
-            <artifactId>commons-codec</artifactId>
-            <version>${commons-codec.version}</version>
-        </dependency>
-        <!-- test scoped -->
-        <dependency>
-            <groupId>org.assertj</groupId>
-            <artifactId>assertj-core</artifactId>
-            <version>${assertj.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.openjdk.jmh</groupId>
             <artifactId>jmh-core</artifactId>
@@ -57,11 +35,6 @@
             <artifactId>guava</artifactId>
             <version>${guava.version}</version>
         </dependency>
-        <dependency>
-            <groupId>com.vdurmont</groupId>
-            <artifactId>emoji-java</artifactId>
-            <version>${emoji-java.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
@@ -73,38 +46,18 @@
             <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.junit.jupiter</groupId>
-            <artifactId>junit-jupiter-api</artifactId>
-            <version>${junit-jupiter-api.version}</version>
-            <scope>test</scope>
-        </dependency>
-
         <dependency>
             <groupId>org.hamcrest</groupId>
             <artifactId>hamcrest-library</artifactId>
             <version>${org.hamcrest.version}</version>
             <scope>test</scope>
         </dependency>
-
-        <!-- Added for password generation -->
-        <dependency>
-            <groupId>org.passay</groupId>
-            <artifactId>passay</artifactId>
-            <version>${passay.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-text</artifactId>
             <version>${commons-text.version}</version>
         </dependency>
 
-        <dependency>
-            <groupId>org.ahocorasick</groupId>
-            <artifactId>ahocorasick</artifactId>
-            <version>${ahocorasick.version}</version>
-        </dependency>
-
     </dependencies>
 
     <build>
@@ -131,18 +84,10 @@
     </build>
 
     <properties>
-        <!-- util -->
         <commons-lang3.version>3.8.1</commons-lang3.version>
-        <commons-codec.version>1.10</commons-codec.version>
-        <!-- testing -->
-        <assertj.version>3.6.1</assertj.version>
         <icu4j.version>61.1</icu4j.version>
         <guava.version>27.0.1-jre</guava.version>
-        <emoji-java.version>4.0.0</emoji-java.version>
-        <junit-jupiter-api.version>5.3.1</junit-jupiter-api.version>
-        <passay.version>1.3.1</passay.version>
         <commons-text.version>1.4</commons-text.version>
-        <ahocorasick.version>0.4.0</ahocorasick.version>
     </properties>
 
 </project>

java-strings-2/src/main/java/com/baeldung/string/performance/RemovingStopwordsPerformanceComparison.java

@@ -0,0 +1,73 @@
+package com.baeldung.string.performance;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+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;
+
+
+@Fork(value = 3, warmups = 1)
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+public class RemovingStopwordsPerformanceComparison {
+
+    private String data;
+    
+    private List<String> stopwords;
+
+    private String stopwordsRegex;
+    
+    
+    public static void main(String[] args) throws Exception {
+        org.openjdk.jmh.Main.main(args);
+    }
+
+    @Setup
+    public void setup() throws IOException {
+        data = new String(Files.readAllBytes(Paths.get("src/main/resources/shakespeare-hamlet.txt")));
+        data = data.toLowerCase();
+        stopwords = Files.readAllLines(Paths.get("src/main/resources/english_stopwords.txt"));
+        stopwordsRegex = stopwords.stream().collect(Collectors.joining("|", "\\b(", ")\\b\\s?"));
+    }
+
+    @Benchmark
+    public String removeManually() {
+        String[] allWords = data.split(" ");
+        StringBuilder builder = new StringBuilder();
+        for(String word:allWords) {
+            if(! stopwords.contains(word)) {
+                builder.append(word);
+                builder.append(' ');
+            }
+        }
+        return builder.toString().trim();
+    }
+
+    @Benchmark
+    public String removeAll() {
+        ArrayList<String> allWords = Stream.of(data.split(" "))
+            .collect(Collectors.toCollection(ArrayList<String>::new));
+        allWords.removeAll(stopwords);
+        return allWords.stream().collect(Collectors.joining(" "));
+    }
+
+    @Benchmark
+    public String replaceRegex() {
+        return data.replaceAll(stopwordsRegex, "");
+    }
+
+}

java-strings-2/src/main/resources/english_stopwords.txt

@@ -0,0 +1,127 @@
+i
+me
+my
+myself
+we
+our
+ours
+ourselves
+you
+your
+yours
+yourself
+yourselves
+he
+him
+his
+himself
+she
+her
+hers
+herself
+it
+its
+itself
+they
+them
+their
+theirs
+themselves
+what
+which
+who
+whom
+this
+that
+these
+those
+am
+is
+are
+was
+were
+be
+been
+being
+have
+has
+had
+having
+do
+does
+did
+doing
+a
+an
+the
+and
+but
+if
+or
+because
+as
+until
+while
+of
+at
+by
+for
+with
+about
+against
+between
+into
+through
+during
+before
+after
+above
+below
+to
+from
+up
+down
+in
+out
+on
+off
+over
+under
+again
+further
+then
+once
+here
+there
+when
+where
+why
+how
+all
+any
+both
+each
+few
+more
+most
+other
+some
+such
+no
+nor
+not
+only
+own
+same
+so
+than
+too
+very
+s
+t
+can
+will
+just
+don
+should
+now

java-strings-2/src/test/java/com/baeldung/initialization/StringInitializationUnitTest.java

@@ -0,0 +1,58 @@
+package com.baeldung.initialization;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+
+import org.junit.Test;
+
+public class StringInitializationUnitTest {
+
+    private String fieldString;
+
+    void printDeclaredOnlyString() {
+        String localVarString = null;
+
+        System.out.println(localVarString); // compilation error
+        System.out.println(fieldString);
+    }
+
+    @Test
+    public void givenDeclaredFeldStringAndNullString_thenCompareEquals() {
+        String localVarString = null;
+
+        assertEquals(fieldString, localVarString);
+    }
+
+    @Test
+    public void givenTwoStringsWithSameLiteral_thenCompareReferencesEquals() {
+        String literalOne = "Baeldung";
+        String literalTwo = "Baeldung";
+
+        assertTrue(literalOne == literalTwo);
+    }
+
+    @Test
+    public void givenTwoStringsUsingNew_thenCompareReferencesNotEquals() {
+        String newStringOne = new String("Baeldung");
+        String newStringTwo = new String("Baeldung");
+
+        assertFalse(newStringOne == newStringTwo);
+    }
+
+    @Test
+    public void givenEmptyLiteralStringsAndNewObject_thenCompareEquals() {
+        String emptyLiteral = "";
+        String emptyNewString = new String("");
+
+        assertEquals(emptyLiteral, emptyNewString);
+    }
+
+    @Test
+    public void givenEmptyStringObjects_thenCompareEquals() {
+        String emptyNewString = new String("");
+        String emptyNewStringTwo = new String();
+
+        assertEquals(emptyNewString, emptyNewStringTwo);
+    }
+}

java-strings-2/src/test/java/com/baeldung/string/RemoveStopwordsUnitTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.string;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class RemoveStopwordsUnitTest {
+    final String original = "The quick brown fox jumps over the lazy dog";
+    final String target = "quick brown fox jumps lazy dog";
+    static List<String> stopwords;
+
+    @BeforeClass
+    public static void loadStopwords() throws IOException {
+        stopwords = Files.readAllLines(Paths.get("src/main/resources/english_stopwords.txt"));
+    }
+
+    @Test
+    public void whenRemoveStopwordsManually_thenSuccess() {
+        String[] allWords = original.toLowerCase()
+            .split(" ");
+        StringBuilder builder = new StringBuilder();
+        for (String word : allWords) {
+            if (!stopwords.contains(word)) {
+                builder.append(word);
+                builder.append(' ');
+            }
+        }
+
+        String result = builder.toString().trim();
+        assertEquals(result, target);
+    }
+
+    @Test
+    public void whenRemoveStopwordsUsingRemoveAll_thenSuccess() {
+        ArrayList<String> allWords = Stream.of(original.toLowerCase()
+            .split(" "))
+            .collect(Collectors.toCollection(ArrayList<String>::new));
+        allWords.removeAll(stopwords);
+        String result = allWords.stream().collect(Collectors.joining(" "));
+        assertEquals(result, target);
+    }
+
+    @Test
+    public void whenRemoveStopwordsUsingRegex_thenSuccess() {
+        String stopwordsRegex = stopwords.stream()
+            .collect(Collectors.joining("|", "\\b(", ")\\b\\s?"));
+        String result = original.toLowerCase().replaceAll(stopwordsRegex, "");
+        assertEquals(result, target);
+    }
+
+}

jhipster-5/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Creating New APIs and Views in JHipster](https://www.baeldung.com/jhipster-new-apis-and-views)

kotlin-libraries-2/pom.xml

@@ -18,14 +18,16 @@
             <groupId>com.fasterxml.jackson.module</groupId>
             <artifactId>jackson-module-kotlin</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.reactivex.rxjava2</groupId>
+            <artifactId>rxkotlin</artifactId>
+            <version>2.3.0</version>
+        </dependency>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <scope>test</scope>
         </dependency>
-
-
-        
     </dependencies>
 
     <properties>

kotlin-libraries-2/src/test/kotlin/com/baeldung/kotlin/rxkotlin/RxKotlinTest.kt

@@ -0,0 +1,157 @@
+package com.baeldung.kotlin.rxkotlin
+
+import io.reactivex.Maybe
+import io.reactivex.Observable
+import io.reactivex.functions.BiFunction
+import io.reactivex.rxkotlin.*
+import io.reactivex.subjects.PublishSubject
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+
+class RxKotlinTest {
+
+    @Test
+    fun whenBooleanArrayToObserver_thenBooleanObserver() {
+        val observable = listOf(true, false, false).toObservable()
+        observable.test().assertValues(true, false, false)
+    }
+
+    @Test
+    fun whenBooleanArrayToFlowable_thenBooleanFlowable() {
+        val flowable = listOf(true, false, false).toFlowable()
+        flowable.buffer(2).test().assertValues(listOf(true, false), listOf(false))
+    }
+
+    @Test
+    fun whenIntArrayToObserver_thenIntObserver() {
+        val observable = listOf(1, 1, 2, 3).toObservable()
+        observable.test().assertValues(1, 1, 2, 3)
+    }
+
+    @Test
+    fun whenIntArrayToFlowable_thenIntFlowable() {
+        val flowable = listOf(1, 1, 2, 3).toFlowable()
+        flowable.buffer(2).test().assertValues(listOf(1, 1), listOf(2, 3))
+    }
+
+    @Test
+    fun whenObservablePairToMap_thenSingleNoDuplicates() {
+        val list = listOf(Pair("a", 1), Pair("b", 2), Pair("c", 3), Pair("a", 4))
+        val observable = list.toObservable()
+        val map = observable.toMap()
+        assertEquals(mapOf(Pair("a", 4), Pair("b", 2), Pair("c", 3)), map.blockingGet())
+    }
+
+    @Test
+    fun whenObservablePairToMap_thenSingleWithDuplicates() {
+        val list = listOf(Pair("a", 1), Pair("b", 2), Pair("c", 3), Pair("a", 4))
+        val observable = list.toObservable()
+        val map = observable.toMultimap()
+        assertEquals(
+                mapOf(Pair("a", listOf(1, 4)), Pair("b", listOf(2)), Pair("c", listOf(3))),
+                map.blockingGet())
+    }
+
+    @Test
+    fun whenMergeAll_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.mergeAll()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenConcatAll_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.concatAll()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenSwitchLatest_thenStream() {
+        val subject = PublishSubject.create<Observable<String>>()
+        val observable = subject.switchLatest()
+        val testObserver = observable.test()
+        subject.onNext(Observable.just("first", "second"))
+        testObserver.assertValues("first", "second")
+        subject.onNext(Observable.just("third", "fourth"))
+        subject.onNext(Observable.just("fifth"))
+        testObserver.assertValues("first", "second", "third", "fourth", "fifth")
+    }
+
+    @Test
+    fun whenMergeAllMaybes_thenObservable() {
+        val subject = PublishSubject.create<Maybe<Int>>()
+        val observable = subject.mergeAllMaybes()
+        val testObserver = observable.test()
+        subject.onNext(Maybe.just(1))
+        subject.onNext(Maybe.just(2))
+        subject.onNext(Maybe.empty())
+        testObserver.assertValues(1, 2)
+        subject.onNext(Maybe.error(Exception("")))
+        subject.onNext(Maybe.just(3))
+        testObserver.assertValues(1, 2).assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenMerge_thenStream() {
+        val observables = mutableListOf(Observable.just("first", "second"))
+        val observable = observables.merge()
+        observables.add(Observable.just("third", "fourth"))
+        observables.add(Observable.error(Exception("e")))
+        observables.add(Observable.just("fifth"))
+
+        observable.test().assertValues("first", "second", "third", "fourth").assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenMergeDelayError_thenStream() {
+        val observables = mutableListOf<Observable<String>>(Observable.error(Exception("e1")))
+        val observable = observables.mergeDelayError()
+        observables.add(Observable.just("1", "2"))
+        observables.add(Observable.error(Exception("e2")))
+        observables.add(Observable.just("3"))
+
+        observable.test().assertValues("1", "2", "3").assertError(Exception::class.java)
+    }
+
+    @Test
+    fun whenCast_thenUniformType() {
+        val observable = Observable.just<Number>(1, 1, 2, 3)
+        observable.cast<Int>().test().assertValues(1, 1, 2, 3)
+    }
+
+    @Test
+    fun whenOfType_thenFilter() {
+        val observable = Observable.just(1, "and", 2, "and")
+        observable.ofType<Int>().test().assertValues(1, 2)
+    }
+
+    @Test
+    fun whenFunction_thenCompletable() {
+        var value = 0
+        val completable = { value = 3 }.toCompletable()
+        assertFalse(completable.test().isCancelled)
+        assertEquals(3, value)
+    }
+
+    @Test
+    fun whenHelper_thenMoreIdiomaticKotlin() {
+        val zipWith = Observable.just(1).zipWith(Observable.just(2)) { a, b -> a + b }
+        zipWith.subscribeBy(onNext = { println(it) })
+        val zip = Observables.zip(Observable.just(1), Observable.just(2)) { a, b -> a + b }
+        zip.subscribeBy(onNext = { println(it) })
+        val zipOrig = Observable.zip(Observable.just(1), Observable.just(2), BiFunction<Int, Int, Int> { a, b -> a + b })
+        zipOrig.subscribeBy(onNext = { println(it) })
+    }
+}

kotlin-libraries/build.gradle

@@ -54,9 +54,8 @@ dependencies {
     testCompile group: 'org.jetbrains.spek', name: 'spek-subject-extension', version: '1.1.5'
     testCompile group: 'org.jetbrains.spek', name: 'spek-junit-platform-engine', version: '1.1.5'
     implementation 'com.beust:klaxon:3.0.1'
-    implementation 'io.reactivex.rxjava2:rxkotlin:2.3.0'
-
 }
+
 task runServer(type: JavaExec) {
     main = 'APIServer'
    classpath = sourceSets.main.runtimeClasspath

libraries-2/README.md

@@ -1,3 +1,7 @@
-## Relevant Articles
 
+### Relevant Articles: 
+
+- [A Guide to jBPM with Java](https://www.baeldung.com/jbpm-java)
 - [Guide to Classgraph Library](https://www.baeldung.com/classgraph)
+- [Create a Java Command Line Program with Picocli](https://www.baeldung.com/java-picocli-create-command-line-program)
+

logging-modules/logback/README.md

@@ -1,3 +1,4 @@
 ### Relevant Articles:
 
 - [Get Log Output in JSON](https://www.baeldung.com/java-log-json-output)
+- [SLF4J Warning: Class Path Contains Multiple SLF4J Bindings](https://www.baeldung.com/slf4j-classpath-multiple-bindings)

persistence-modules/README.md

@@ -5,7 +5,6 @@
 ### Relevant Articles:
 
 - [Introduction to Hibernate Search](http://www.baeldung.com/hibernate-search)
-- [Bootstrapping Hibernate 5 with Spring](http://www.baeldung.com/hibernate-5-spring)
 - [Introduction to Lettuce – the Java Redis Client](http://www.baeldung.com/java-redis-lettuce)
 - [A Guide to Jdbi](http://www.baeldung.com/jdbi)
 - [Pessimistic Locking in JPA](http://www.baeldung.com/jpa-pessimistic-locking)
@@ -13,3 +12,6 @@
 - [Spring Data with Reactive Cassandra](https://www.baeldung.com/spring-data-cassandra-reactive)
 - [Spring Data JPA – Derived Delete Methods](https://www.baeldung.com/spring-data-jpa-deleteby)
 - [Difference Between save() and saveAndFlush() in Spring Data JPA](https://www.baeldung.com/spring-data-jpa-save-saveandflush)
+- [Spring Boot with Hibernate](https://www.baeldung.com/spring-boot-hibernate)
+- [Persisting Maps with Hibernate](https://www.baeldung.com/hibernate-persisting-maps)
+- [Difference Between @Size, @Length, and @Column(length=value)](https://www.baeldung.com/jpa-size-length-column-differences)

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

@@ -8,3 +8,4 @@
 - [Introduction to the JDBC RowSet Interface in Java](http://www.baeldung.com/java-jdbc-rowset)
 - [A Simple Guide to Connection Pooling in Java](https://www.baeldung.com/java-connection-pooling)
 - [Guide to the JDBC ResultSet Interface](https://www.baeldung.com/jdbc-resultset)
+- [Types of SQL Joins](https://www.baeldung.com/sql-joins)

persistence-modules/hibernate-mapping/README.md

@@ -0,0 +1,4 @@
+
+### Relevant Articles: 
+
+- [Persisting Maps with Hibernate](https://www.baeldung.com/hibernate-persisting-maps)

persistence-modules/java-jpa/README.md

@@ -2,8 +2,9 @@
 
 - [A Guide to SqlResultSetMapping](http://www.baeldung.com/jpa-sql-resultset-mapping)
 - [A Guide to Stored Procedures with JPA](http://www.baeldung.com/jpa-stored-procedures)
-- [Fixing the JPA error “java.lang.String cannot be cast to [Ljava.lang.String;”]](https://www.baeldung.com/jpa-error-java-lang-string-cannot-be-cast) 
+- [Fixing the JPA error “java.lang.String cannot be cast to Ljava.lang.String;”](https://www.baeldung.com/jpa-error-java-lang-string-cannot-be-cast)
 - [JPA Entity Graph](https://www.baeldung.com/jpa-entity-graph)
 - [JPA 2.2 Support for Java 8 Date/Time Types](https://www.baeldung.com/jpa-java-time)
 - [Converting Between LocalDate and SQL Date](https://www.baeldung.com/java-convert-localdate-sql-date)
 - [Combining JPA And/Or Criteria Predicates](https://www.baeldung.com/jpa-and-or-criteria-predicates)
+- [Types of JPA Queries](https://www.baeldung.com/jpa-queries)

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/basicannotation/Course.java

@@ -0,0 +1,33 @@
+package com.baeldung.jpa.basicannotation;
+
+import javax.persistence.Basic;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.Id;
+
+@Entity
+public class Course {
+
+    @Id
+    private int id;
+
+    @Basic(optional = false, fetch = FetchType.LAZY)
+    private String name;
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}
+

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/entity/Student.java

@@ -0,0 +1,75 @@
+package com.baeldung.jpa.entity;
+
+import java.util.Date;
+
+import javax.persistence.Column;
+import javax.persistence.Entity;
+import javax.persistence.EnumType;
+import javax.persistence.Enumerated;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Table;
+import javax.persistence.Temporal;
+import javax.persistence.TemporalType;
+import javax.persistence.Transient;
+
+import com.baeldung.util.Gender;
+
+@Entity
+@Table(name="STUDENT")
+public class Student {
+
+	@Id
+	@GeneratedValue(strategy = GenerationType.AUTO)
+	private Long id;
+	@Column(name = "STUDENT_NAME", length = 50, nullable = false, unique = false)
+	private String name;
+	@Transient
+	private Integer age;
+	@Temporal(TemporalType.DATE)
+	private Date birthDate;
+	@Enumerated(EnumType.STRING)
+	private Gender gender;
+
+	public Long getId() {
+		return id;
+	}
+
+	public void setId(Long id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public Integer getAge() {
+		return age;
+	}
+
+	public void setAge(Integer age) {
+		this.age = age;
+	}
+
+	public Date getBirthDate() {
+		return birthDate;
+	}
+
+	public void setBirthDate(Date birthDate) {
+		this.birthDate = birthDate;
+	}
+
+	public Gender getGender() {
+		return gender;
+	}
+
+	public void setGender(Gender gender) {
+		this.gender = gender;
+	}
+
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Article.java

@@ -0,0 +1,91 @@
+package com.baeldung.jpa.enums;
+
+import javax.persistence.*;
+
+@Entity
+public class Article {
+
+    @Id
+    private int id;
+
+    private String title;
+
+    @Enumerated(EnumType.ORDINAL)
+    private Status status;
+
+    @Enumerated(EnumType.STRING)
+    private Type type;
+
+    @Basic
+    private int priorityValue;
+
+    @Transient
+    private Priority priority;
+
+    private Category category;
+
+    public Article() {
+    }
+
+    @PostLoad
+    void fillTransient() {
+        if (priorityValue > 0) {
+            this.priority = Priority.of(priorityValue);
+        }
+    }
+
+    @PrePersist
+    void fillPersistent() {
+        if (priority != null) {
+            this.priorityValue = priority.getPriority();
+        }
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Status getStatus() {
+        return status;
+    }
+
+    public void setStatus(Status status) {
+        this.status = status;
+    }
+
+    public Type getType() {
+        return type;
+    }
+
+    public void setType(Type type) {
+        this.type = type;
+    }
+
+    public Priority getPriority() {
+        return priority;
+    }
+
+    public void setPriority(Priority priority) {
+        this.priority = priority;
+    }
+
+    public Category getCategory() {
+        return category;
+    }
+
+    public void setCategory(Category category) {
+        this.category = category;
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Category.java

@@ -0,0 +1,17 @@
+package com.baeldung.jpa.enums;
+
+import java.util.stream.Stream;
+
+public enum Category {
+    SPORT("S"), MUSIC("M"), TECHNOLOGY("T");
+
+    private String code;
+
+    Category(String code) {
+        this.code = code;
+    }
+
+    public String getCode() {
+        return code;
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/CategoryConverter.java

@@ -0,0 +1,28 @@
+package com.baeldung.jpa.enums;
+
+import javax.persistence.AttributeConverter;
+import javax.persistence.Converter;
+import java.util.stream.Stream;
+
+@Converter(autoApply = true)
+public class CategoryConverter implements AttributeConverter<Category, String> {
+    @Override
+    public String convertToDatabaseColumn(Category category) {
+        if (category == null) {
+            return null;
+        }
+        return category.getCode();
+    }
+
+    @Override
+    public Category convertToEntityAttribute(final String code) {
+        if (code == null) {
+            return null;
+        }
+
+        return Stream.of(Category.values())
+                .filter(c -> c.getCode().equals(code))
+                .findFirst()
+                .orElseThrow(IllegalArgumentException::new);
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Priority.java

@@ -0,0 +1,24 @@
+package com.baeldung.jpa.enums;
+
+import java.util.stream.Stream;
+
+public enum Priority {
+    LOW(100), MEDIUM(200), HIGH(300);
+
+    private int priority;
+
+    private Priority(int priority) {
+        this.priority = priority;
+    }
+
+    public int getPriority() {
+        return priority;
+    }
+
+    public static Priority of(int priority) {
+        return Stream.of(Priority.values())
+                .filter(p -> p.getPriority() == priority)
+                .findFirst()
+                .orElseThrow(IllegalArgumentException::new);
+    }
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Status.java

@@ -0,0 +1,5 @@
+package com.baeldung.jpa.enums;
+
+public enum Status {
+    OPEN, REVIEW, APPROVED, REJECTED;
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/jpa/enums/Type.java

@@ -0,0 +1,5 @@
+package com.baeldung.jpa.enums;
+
+enum Type {
+    INTERNAL, EXTERNAL;
+}

persistence-modules/java-jpa/src/main/java/com/baeldung/util/Gender.java

@@ -0,0 +1,6 @@
+package com.baeldung.util;
+
+public enum Gender {
+	MALE,
+	FEMALE
+}

persistence-modules/java-jpa/src/main/resources/META-INF/persistence.xml

@@ -26,6 +26,8 @@
     <persistence-unit name="jpa-h2">
         <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
         <class>com.baeldung.jpa.stringcast.Message</class>
+        <class>com.baeldung.jpa.enums.Article</class>
+        <class>com.baeldung.jpa.enums.CategoryConverter</class>
         <exclude-unlisted-classes>true</exclude-unlisted-classes>
         <properties>
             <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
@@ -145,5 +147,20 @@
             <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false" />
         </properties>
     </persistence-unit>
-
+    
-</persistence>
+    <persistence-unit name="jpa-entity-definition">
+        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
+        <class>com.baeldung.jpa.entity.Student</class>
+        <exclude-unlisted-classes>true</exclude-unlisted-classes>
+        <properties>
+            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver" />
+            <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test" />
+            <property name="javax.persistence.jdbc.user" value="sa" />
+            <property name="javax.persistence.jdbc.password" value="" />
+            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect" />
+            <property name="hibernate.hbm2ddl.auto" value="create-drop" />
+            <property name="show_sql" value="true" />
+            <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false" />
+        </properties>
+    </persistence-unit>
+</persistence>

persistence-modules/java-jpa/src/test/java/com/baeldung/jpa/basicannotation/BasicAnnotationIntegrationTest.java

@@ -0,0 +1,56 @@
+package com.baeldung.jpa.basicannotation;
+
+import org.hibernate.PropertyValueException;
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Persistence;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.AfterClass;
+import org.junit.Test;
+
+import java.io.IOException;
+
+public class BasicAnnotationIntegrationTest {
+
+    private static EntityManager entityManager;
+    private static EntityManagerFactory entityManagerFactory;
+
+    @BeforeClass
+    public void setup() {
+        entityManagerFactory = Persistence.createEntityManagerFactory("java-jpa-scheduled-day");
+        entityManager = entityManagerFactory.createEntityManager();
+    }
+
+    @Test
+    public void givenACourse_whenCourseNamePresent_shouldPersist() {
+        Course course = new Course();
+        course.setName("Computers");
+
+        entityManager.persist(course);
+        entityManager.flush();
+        entityManager.clear();
+
+    }
+
+    @Test(expected = PropertyValueException.class)
+    public void givenACourse_whenCourseNameAbsent_shouldFail() {
+        Course course = new Course();
+
+        entityManager.persist(course);
+        entityManager.flush();
+        entityManager.clear();
+    }
+
+    @AfterClass
+    public void destroy() {
+
+        if (entityManager != null) {
+            entityManager.close();
+        }
+        if (entityManagerFactory != null) {
+            entityManagerFactory.close();
+        }
+    }
+}

persistence-modules/java-jpa/src/test/java/com/baeldung/jpa/entity/StudentEntityIntegrationTest.java

@@ -0,0 +1,91 @@
+package com.baeldung.jpa.entity;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Date;
+import java.util.List;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Persistence;
+import javax.persistence.TypedQuery;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.baeldung.util.Gender;
+
+public class StudentEntityIntegrationTest {
+
+	private EntityManagerFactory emf;
+	private EntityManager em;
+
+	@Before
+	public void setup() {
+		emf = Persistence.createEntityManagerFactory("jpa-entity-definition");
+		em = emf.createEntityManager();
+	}
+
+	@Test
+	public void persistStudentThenRetrieveTheDetails() {
+		Student student = createStudentWithRelevantDetails();
+		persist(student);
+		clearThePersistenceContext();
+		List<Student> students = getStudentsFromTable();
+		checkAssertionsWith(students);
+	}
+
+	@After
+	public void destroy() {
+		if (em != null) {
+			em.close();
+		}
+		if (emf != null) {
+			emf.close();
+		}
+	}
+
+	private void clearThePersistenceContext() {
+		em.clear();
+	}
+
+	private void checkAssertionsWith(List<Student> students) {
+		assertEquals(1, students.size());
+		Student john = students.get(0);
+		assertEquals(1L, john.getId().longValue());
+		assertEquals(null, john.getAge());
+		assertEquals("John", john.getName());
+	}
+
+	private List<Student> getStudentsFromTable() {
+		String selectQuery = "SELECT student FROM Student student";
+		TypedQuery<Student> selectFromStudentTypedQuery = em.createQuery(selectQuery, Student.class);
+		List<Student> students = selectFromStudentTypedQuery.getResultList();
+		return students;
+	}
+
+	private void persist(Student student) {
+		em.getTransaction().begin();
+		em.persist(student);
+		em.getTransaction().commit();
+	}
+
+	private Student createStudentWithRelevantDetails() {
+		Student student = new Student();
+		student.setAge(20); // the 'age' field has been annotated with @Transient
+		student.setName("John");
+		Date date = getDate();
+		student.setBirthDate(date);
+		student.setGender(Gender.MALE);
+		return student;
+	}
+
+	private Date getDate() {
+		LocalDate localDate = LocalDate.of(2008, 7, 20);
+		return Date.from(localDate.atStartOfDay(ZoneId.systemDefault()).toInstant());
+	}
+
+}

persistence-modules/java-jpa/src/test/java/com/baeldung/jpa/enums/ArticleUnitTest.java

@@ -0,0 +1,118 @@
+package com.baeldung.jpa.enums;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.EntityTransaction;
+import javax.persistence.Persistence;
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ArticleUnitTest {
+
+    private static EntityManager em;
+    private static EntityManagerFactory emFactory;
+
+    @BeforeClass
+    public static void setup() {
+        Map properties = new HashMap();
+        properties.put("hibernate.show_sql", "true");
+        properties.put("hibernate.format_sql", "true");
+        emFactory = Persistence.createEntityManagerFactory("jpa-h2", properties);
+        em = emFactory.createEntityManager();
+    }
+
+    @Test
+    public void shouldPersistStatusEnumOrdinalValue() {
+        // given
+        Article article = new Article();
+        article.setId(1);
+        article.setTitle("ordinal title");
+        article.setStatus(Status.OPEN);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 1);
+
+        assertEquals(1, persistedArticle.getId());
+        assertEquals("ordinal title", persistedArticle.getTitle());
+        assertEquals(Status.OPEN, persistedArticle.getStatus());
+    }
+
+    @Test
+    public void shouldPersistTypeEnumStringValue() {
+        // given
+        Article article = new Article();
+        article.setId(2);
+        article.setTitle("string title");
+        article.setType(Type.EXTERNAL);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 2);
+
+        assertEquals(2, persistedArticle.getId());
+        assertEquals("string title", persistedArticle.getTitle());
+        assertEquals(Type.EXTERNAL, persistedArticle.getType());
+    }
+
+    @Test
+    public void shouldPersistPriorityIntValue() {
+        // given
+        Article article = new Article();
+        article.setId(3);
+        article.setTitle("callback title");
+        article.setPriority(Priority.HIGH);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 3);
+
+        assertEquals(3, persistedArticle.getId());
+        assertEquals("callback title", persistedArticle.getTitle());
+        assertEquals(Priority.HIGH, persistedArticle.getPriority());
+
+    }
+
+    @Test
+    public void shouldPersistCategoryEnumConvertedValue() {
+        // given
+        Article article = new Article();
+        article.setId(4);
+        article.setTitle("converted title");
+        article.setCategory(Category.MUSIC);
+
+        // when
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        // then
+        Article persistedArticle = em.find(Article.class, 4);
+
+        assertEquals(4, persistedArticle.getId());
+        assertEquals("converted title", persistedArticle.getTitle());
+        assertEquals(Category.MUSIC, persistedArticle.getCategory());
+    }
+
+}

persistence-modules/java-mongodb/README.md

@@ -2,3 +2,4 @@
 
 - [A Guide to MongoDB with Java](http://www.baeldung.com/java-mongodb)
 - [A Simple Tagging Implementation with MongoDB](http://www.baeldung.com/mongodb-tagging)
+- [MongoDB BSON Guide](https://www.baeldung.com/mongodb-bson)

persistence-modules/pom.xml

@@ -55,5 +55,6 @@
         <module>spring-hibernate-5</module>
         <module>spring-hibernate4</module>
         <module>spring-jpa</module>
+        <module>spring-persistence-simple</module>
     </modules>
 </project>

persistence-modules/spring-data-jpa-2/README.md

@@ -1,6 +1,14 @@
-=========
+=========
-
+
-## Spring Data JPA Example Project
+## Spring Data JPA Example Project
-
+
-### Relevant Articles: 
+### Relevant Articles: 
-- [Spring Data JPA – Derived Delete Methods](https://www.baeldung.com/spring-data-jpa-deleteby)
+- [Spring Data JPA – Derived Delete Methods](https://www.baeldung.com/spring-data-jpa-deleteby)
+- [JPA Join Types](https://www.baeldung.com/jpa-join-types)
+- [Case Insensitive Queries with Spring Data Repository](https://www.baeldung.com/spring-data-case-insensitive-queries)
+- [The Exists Query in Spring Data](https://www.baeldung.com/spring-data-exists-query)
+- [Spring Data JPA Repository Populators](https://www.baeldung.com/spring-data-jpa-repository-populators)
+- [Spring Data JPA and Null Parameters](https://www.baeldung.com/spring-data-jpa-null-parameters)
+- [Spring Data JPA Projections](https://www.baeldung.com/spring-data-jpa-projections)
+- [JPA @Embedded And @Embeddable](https://www.baeldung.com/jpa-embedded-embeddable)
+- [Spring Data JPA Delete and Relationships](https://www.baeldung.com/spring-data-jpa-delete)

persistence-modules/spring-data-jpa-2/src/main/java/com/baeldung/derivedquery/entity/User.java

@@ -0,0 +1,70 @@
+package com.baeldung.derivedquery.entity;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+import javax.persistence.Table;
+import java.time.ZonedDateTime;
+
+@Table(name = "users")
+@Entity
+public class User {
+
+    @Id
+    @GeneratedValue
+    private Integer id;
+    private String name;
+    private Integer age;
+    private ZonedDateTime birthDate;
+    private Boolean active;
+
+    public User() {
+    }
+
+    public User(String name, Integer age, ZonedDateTime birthDate, Boolean active) {
+        this.name = name;
+        this.age = age;
+        this.birthDate = birthDate;
+        this.active = active;
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public void setAge(Integer age) {
+        this.age = age;
+    }
+
+    public ZonedDateTime getBirthDate() {
+        return birthDate;
+    }
+
+    public void setBirthDate(ZonedDateTime birthDate) {
+        this.birthDate = birthDate;
+    }
+
+    public Boolean getActive() {
+        return active;
+    }
+
+    public void setActive(Boolean active) {
+        this.active = active;
+    }
+}

persistence-modules/spring-data-jpa-2/src/main/java/com/baeldung/derivedquery/repository/UserRepository.java

@@ -0,0 +1,60 @@
+package com.baeldung.derivedquery.repository;
+
+import com.baeldung.derivedquery.entity.User;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.time.ZonedDateTime;
+import java.util.Collection;
+import java.util.List;
+
+public interface UserRepository extends JpaRepository<User, Integer> {
+
+    List<User> findByName(String name);
+
+    List<User> findByNameIs(String name);
+
+    List<User> findByNameEquals(String name);
+
+    List<User> findByNameIsNull();
+
+    List<User> findByNameNot(String name);
+
+    List<User> findByNameIsNot(String name);
+
+    List<User> findByNameStartingWith(String name);
+
+    List<User> findByNameEndingWith(String name);
+
+    List<User> findByNameContaining(String name);
+
+    List<User> findByNameLike(String name);
+
+    List<User> findByAgeLessThan(Integer age);
+
+    List<User> findByAgeLessThanEqual(Integer age);
+
+    List<User> findByAgeGreaterThan(Integer age);
+
+    List<User> findByAgeGreaterThanEqual(Integer age);
+
+    List<User> findByAgeBetween(Integer startAge, Integer endAge);
+
+    List<User> findByBirthDateAfter(ZonedDateTime birthDate);
+
+    List<User> findByBirthDateBefore(ZonedDateTime birthDate);
+
+    List<User> findByActiveTrue();
+
+    List<User> findByActiveFalse();
+
+    List<User> findByAgeIn(Collection<Integer> ages);
+
+    List<User> findByNameOrBirthDate(String name, ZonedDateTime birthDate);
+
+    List<User> findByNameOrBirthDateAndActive(String name, ZonedDateTime birthDate, Boolean active);
+
+    List<User> findByNameOrderByName(String name);
+
+    List<User> findByNameOrderByNameDesc(String name);
+
+}

persistence-modules/spring-data-jpa-2/src/main/java/com/baeldung/like/model/Movie.java

@@ -0,0 +1,58 @@
+package com.baeldung.like.model;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity
+public class Movie {
+    @Id
+    @GeneratedValue(strategy = GenerationType.SEQUENCE)
+    private Long id;
+    private String title;
+    private String director;
+    private String rating;
+    private int duration;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public String getDirector() {
+        return director;
+    }
+
+    public void setDirector(String director) {
+        this.director = director;
+    }
+
+    public String getRating() {
+        return rating;
+    }
+
+    public void setRating(String rating) {
+        this.rating = rating;
+    }
+
+    public int getDuration() {
+        return duration;
+    }
+
+    public void setDuration(int duration) {
+        this.duration = duration;
+    }
+
+}

persistence-modules/spring-data-jpa-2/src/main/java/com/baeldung/like/repository/MovieRepository.java

@@ -0,0 +1,41 @@
+package com.baeldung.like.repository;
+
+import java.util.List;
+
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.CrudRepository;
+import org.springframework.data.repository.query.Param;
+
+import com.baeldung.like.model.Movie;
+
+public interface MovieRepository extends CrudRepository<Movie, Long> {
+
+    List<Movie> findByTitleContaining(String title);
+    
+    List<Movie> findByTitleLike(String title);
+
+    List<Movie> findByTitleContains(String title);
+
+    List<Movie> findByTitleIsContaining(String title);
+
+    List<Movie> findByRatingStartsWith(String rating);
+
+    List<Movie> findByDirectorEndsWith(String director);
+
+    List<Movie> findByTitleContainingIgnoreCase(String title);
+    
+    List<Movie> findByRatingNotContaining(String rating);
+    
+    List<Movie> findByDirectorNotLike(String director);
+    
+    @Query("SELECT m FROM Movie m WHERE m.title LIKE %:title%")
+    List<Movie> searchByTitleLike(@Param("title") String title);
+    
+    @Query("SELECT m FROM Movie m WHERE m.rating LIKE ?1%")
+    List<Movie> searchByRatingStartsWith(String rating);
+    
+    //Escaping works in SpringBoot >= 2.4.1
+    //@Query("SELECT m FROM Movie m WHERE m.director LIKE %?#{escape([0])} escape ?#{escapeCharacter()}")
+    @Query("SELECT m FROM Movie m WHERE m.director LIKE %:#{[0]}")
+    List<Movie> searchByDirectorEndsWith(String director);
+}

persistence-modules/spring-data-jpa-2/src/test/java/com/baeldung/derivedquery/repository/UserRepositoryTest.java

@@ -0,0 +1,172 @@
+package com.baeldung.derivedquery.repository;
+
+import com.baeldung.Application;
+import com.baeldung.derivedquery.entity.User;
+import com.baeldung.derivedquery.repository.UserRepository;
+import java.time.ZonedDateTime;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = Application.class)
+public class UserRepositoryTest {
+
+    private static final String USER_NAME_ADAM = "Adam";
+    private static final String USER_NAME_EVE = "Eve";
+    private static final ZonedDateTime BIRTHDATE = ZonedDateTime.now();
+
+    @Autowired
+    private UserRepository userRepository;
+
+    @Before
+    public void setUp() {
+
+        User user1 = new User(USER_NAME_ADAM, 25, BIRTHDATE, true);
+        User user2 = new User(USER_NAME_ADAM, 20, BIRTHDATE, false);
+        User user3 = new User(USER_NAME_EVE, 20, BIRTHDATE, true);
+        User user4 = new User(null, 30, BIRTHDATE, false);
+
+        userRepository.saveAll(Arrays.asList(user1, user2, user3, user4));
+    }
+
+    @After
+    public void tearDown() {
+
+        userRepository.deleteAll();
+    }
+
+    @Test
+    public void whenFindByName_thenReturnsCorrectResult() {
+
+        assertEquals(2, userRepository.findByName(USER_NAME_ADAM).size());
+    }
+
+    @Test
+    public void whenFindByNameIsNull_thenReturnsCorrectResult() {
+
+        assertEquals(1, userRepository.findByNameIsNull().size());
+    }
+
+    @Test
+    public void whenFindByNameNot_thenReturnsCorrectResult() {
+
+        assertEquals(USER_NAME_EVE, userRepository.findByNameNot(USER_NAME_ADAM).get(0).getName());
+    }
+
+    @Test
+    public void whenFindByNameStartingWith_thenReturnsCorrectResult() {
+
+        assertEquals(2, userRepository.findByNameStartingWith("A").size());
+    }
+
+    @Test
+    public void whenFindByNameEndingWith_thenReturnsCorrectResult() {
+
+        assertEquals(1, userRepository.findByNameEndingWith("e").size());
+    }
+
+    @Test
+    public void whenByNameContaining_thenReturnsCorrectResult() {
+
+        assertEquals(1, userRepository.findByNameContaining("v").size());
+    }
+
+
+    @Test
+    public void whenByNameLike_thenReturnsCorrectResult() {
+
+        assertEquals(2, userRepository.findByNameEndingWith("%d%m").size());
+    }
+
+    @Test
+    public void whenByAgeLessThan_thenReturnsCorrectResult() {
+
+        assertEquals(2, userRepository.findByAgeLessThan(25).size());
+    }
+
+
+    @Test
+    public void whenByAgeLessThanEqual_thenReturnsCorrectResult() {
+
+        assertEquals(3, userRepository.findByAgeLessThanEqual(25).size());
+    }
+
+    @Test
+    public void whenByAgeGreaterThan_thenReturnsCorrectResult() {
+
+        assertEquals(1, userRepository.findByAgeGreaterThan(25).size());
+    }
+
+    @Test
+    public void whenByAgeGreaterThanEqual_thenReturnsCorrectResult() {
+
+        assertEquals(2, userRepository.findByAgeGreaterThanEqual(25).size());
+    }
+
+    @Test
+    public void whenByAgeBetween_thenReturnsCorrectResult() {
+
+        assertEquals(4, userRepository.findByAgeBetween(20, 30).size());
+    }
+
+    @Test
+    public void whenByBirthDateAfter_thenReturnsCorrectResult() {
+
+        final ZonedDateTime yesterday = BIRTHDATE.minusDays(1);
+        assertEquals(4, userRepository.findByBirthDateAfter(yesterday).size());
+    }
+
+    @Test
+    public void whenByBirthDateBefore_thenReturnsCorrectResult() {
+
+        final ZonedDateTime yesterday = BIRTHDATE.minusDays(1);
+        assertEquals(0, userRepository.findByBirthDateBefore(yesterday).size());
+    }
+
+    @Test
+    public void whenByActiveTrue_thenReturnsCorrectResult() {
+
+        assertEquals(2, userRepository.findByActiveTrue().size());
+    }
+
+    @Test
+    public void whenByActiveFalse_thenReturnsCorrectResult() {
+
+        assertEquals(2, userRepository.findByActiveFalse().size());
+    }
+
+
+    @Test
+    public void whenByAgeIn_thenReturnsCorrectResult() {
+
+        final List<Integer> ages = Arrays.asList(20, 25);
+        assertEquals(3, userRepository.findByAgeIn(ages).size());
+    }
+
+    @Test
+    public void whenByNameOrBirthDate() {
+
+        assertEquals(4, userRepository.findByNameOrBirthDate(USER_NAME_ADAM, BIRTHDATE).size());
+    }
+
+    @Test
+    public void whenByNameOrBirthDateAndActive() {
+
+        assertEquals(3, userRepository.findByNameOrBirthDateAndActive(USER_NAME_ADAM, BIRTHDATE, false).size());
+    }
+
+    @Test
+    public void whenByNameOrderByName() {
+
+        assertEquals(2, userRepository.findByNameOrderByName(USER_NAME_ADAM).size());
+    }
+}

persistence-modules/spring-data-jpa-2/src/test/java/com/baeldung/like/MovieRepositoryIntegrationTest.java

@@ -0,0 +1,88 @@
+package com.baeldung.like;
+
+import static org.junit.Assert.assertEquals;
+import static org.springframework.test.context.jdbc.Sql.ExecutionPhase.AFTER_TEST_METHOD;
+
+import java.util.List;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.jdbc.Sql;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import com.baeldung.like.model.Movie;
+import com.baeldung.like.repository.MovieRepository;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+@Sql(scripts = { "/test-movie-data.sql" })
+@Sql(scripts = "/test-movie-cleanup.sql", executionPhase = AFTER_TEST_METHOD)
+public class MovieRepositoryIntegrationTest {
+    @Autowired
+    private MovieRepository movieRepository;
+
+    @Test
+    public void givenPartialTitle_WhenFindByTitleContaining_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.findByTitleContaining("in");
+        assertEquals(3, results.size());
+        
+        results = movieRepository.findByTitleLike("%in%");
+        assertEquals(3, results.size());
+
+        results = movieRepository.findByTitleIsContaining("in");
+        assertEquals(3, results.size());
+
+        results = movieRepository.findByTitleContains("in");
+        assertEquals(3, results.size());
+    }
+
+    @Test
+    public void givenStartOfRating_WhenFindByRatingStartsWith_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.findByRatingStartsWith("PG");
+        assertEquals(6, results.size());
+    }
+
+    @Test
+    public void givenLastName_WhenFindByDirectorEndsWith_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.findByDirectorEndsWith("Burton");
+        assertEquals(1, results.size());
+    }
+
+    @Test
+    public void givenPartialTitle_WhenFindByTitleContainingIgnoreCase_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.findByTitleContainingIgnoreCase("the");
+        assertEquals(2, results.size());
+    }
+
+    @Test
+    public void givenPartialTitle_WhenSearchByTitleLike_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.searchByTitleLike("in");
+        assertEquals(3, results.size());
+    }
+    
+    @Test
+    public void givenStartOfRating_SearchFindByRatingStartsWith_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.searchByRatingStartsWith("PG");
+        assertEquals(6, results.size());
+    }
+    
+    @Test
+    public void givenLastName_WhenSearchByDirectorEndsWith_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.searchByDirectorEndsWith("Burton");
+        assertEquals(1, results.size());
+    }
+    
+    @Test
+    public void givenPartialRating_findByRatingNotContaining_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.findByRatingNotContaining("PG");
+        assertEquals(1, results.size());
+    }
+    
+    @Test
+    public void givenPartialDirector_WhenFindByDirectorNotLike_ThenMoviesShouldReturn() {
+        List<Movie> results = movieRepository.findByDirectorNotLike("An%");
+        assertEquals(5, results.size());
+    }
+}

persistence-modules/spring-data-jpa-2/src/test/resources/test-movie-cleanup.sql

@@ -0,0 +1 @@
+DELETE FROM Movie;

persistence-modules/spring-data-jpa-2/src/test/resources/test-movie-data.sql

@@ -0,0 +1,7 @@
+INSERT INTO movie(id, title, director, rating, duration) VALUES(1, 'Godzilla: King of the Monsters', ' Michael Dougherty', 'PG-13', 132);
+INSERT INTO movie(id, title, director, rating, duration) VALUES(2, 'Avengers: Endgame', 'Anthony Russo', 'PG-13', 181);
+INSERT INTO movie(id, title, director, rating, duration) VALUES(3, 'Captain Marvel', 'Anna Boden', 'PG-13', 123);
+INSERT INTO movie(id, title, director, rating, duration) VALUES(4, 'Dumbo', 'Tim Burton', 'PG', 112);
+INSERT INTO movie(id, title, director, rating, duration) VALUES(5, 'Booksmart', 'Olivia Wilde', 'R', 102);
+INSERT INTO movie(id, title, director, rating, duration) VALUES(6, 'Aladdin', 'Guy Ritchie', 'PG', 128);
+INSERT INTO movie(id, title, director, rating, duration) VALUES(7, 'The Sun Is Also a Star', 'Ry Russo-Young', 'PG-13', 100);

persistence-modules/spring-data-jpa/README.md

@@ -6,7 +6,6 @@
 - [Spring JPA – Multiple Databases](http://www.baeldung.com/spring-data-jpa-multiple-databases)
 - [Spring Data JPA – Adding a Method in All Repositories](http://www.baeldung.com/spring-data-jpa-method-in-all-repositories)
 - [An Advanced Tagging Implementation with JPA](http://www.baeldung.com/jpa-tagging-advanced)
-- [Spring Data JPA @Query](http://www.baeldung.com/spring-data-jpa-query)
 - [Spring Data Annotations](http://www.baeldung.com/spring-data-annotations)
 - [Spring Data Java 8 Support](http://www.baeldung.com/spring-data-java-8)
 - [A Simple Tagging Implementation with JPA](http://www.baeldung.com/jpa-tagging)

persistence-modules/spring-hibernate4/README.md

@@ -4,7 +4,6 @@
 
 ### Relevant Articles: 
 - [Guide to Hibernate 4 with Spring](http://www.baeldung.com/hibernate-4-spring)
-- [The DAO with Spring and Hibernate](http://www.baeldung.com/persistence-layer-with-spring-and-hibernate)
 - [Hibernate Pagination](http://www.baeldung.com/hibernate-pagination)
 - [Sorting with Hibernate](http://www.baeldung.com/hibernate-sort)
 - [Stored Procedures with Hibernate](http://www.baeldung.com/stored-procedures-with-hibernate-tutorial)

persistence-modules/spring-jpa/README.md

@@ -4,8 +4,6 @@
 
 
 ### Relevant Articles: 
-- [A Guide to JPA with Spring](https://www.baeldung.com/the-persistence-layer-with-spring-and-jpa)
-- [Transactions with Spring and JPA](https://www.baeldung.com/transaction-configuration-with-jpa-and-spring)
 - [The DAO with JPA and Spring](http://www.baeldung.com/spring-dao-jpa)
 - [JPA Pagination](http://www.baeldung.com/jpa-pagination)
 - [Sorting with JPA](http://www.baeldung.com/jpa-sort)