diff --git a/core-java-8/findItemsBasedOnValues/.gitignore b/core-java-8/findItemsBasedOnValues/.gitignore
deleted file mode 100644
index ae3c172604..0000000000
--- a/core-java-8/findItemsBasedOnValues/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/bin/
diff --git a/core-java-8/findItemsBasedOnValues/src/findItems/FindItemsBasedOnValues.java b/core-java-collections/src/test/java/com/baeldung/findItems/FindItemsBasedOnOtherStreamUnitTest.java
similarity index 63%
rename from core-java-8/findItemsBasedOnValues/src/findItems/FindItemsBasedOnValues.java
rename to core-java-collections/src/test/java/com/baeldung/findItems/FindItemsBasedOnOtherStreamUnitTest.java
index a0dcdddd85..326ea9fbe4 100644
--- a/core-java-8/findItemsBasedOnValues/src/findItems/FindItemsBasedOnValues.java
+++ b/core-java-collections/src/test/java/com/baeldung/findItems/FindItemsBasedOnOtherStreamUnitTest.java
@@ -1,93 +1,89 @@
-package findItems;
-
-import static org.junit.Assert.assertEquals;
-
-import java.text.ParseException;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.stream.Collectors;
-
-import org.junit.Test;
-
-public class FindItemsBasedOnValues {
-
-    List<Employee> EmplList = new ArrayList<Employee>();
-    List<Department> deptList = new ArrayList<Department>();
-
-    public static void main(String[] args) throws ParseException {
-        FindItemsBasedOnValues findItems = new FindItemsBasedOnValues();
-        findItems.givenDepartmentList_thenEmployeeListIsFilteredCorrectly();
-    }
-
-    @Test
-    public void givenDepartmentList_thenEmployeeListIsFilteredCorrectly() {
-        Integer expectedId = 1002;
-
-        populate(EmplList, deptList);
-
-        List<Employee> filteredList = EmplList.stream()
-            .filter(empl -> deptList.stream()
-                .anyMatch(dept -> dept.getDepartment()
-                    .equals("sales") && empl.getEmployeeId()
-                    .equals(dept.getEmployeeId())))
-            .collect(Collectors.toList());
-
-        assertEquals(expectedId, filteredList.get(0)
-            .getEmployeeId());
-    }
-
-    private void populate(List<Employee> EmplList, List<Department> deptList) {
-        Employee employee1 = new Employee(1001, "empl1");
-        Employee employee2 = new Employee(1002, "empl2");
-        Employee employee3 = new Employee(1003, "empl3");
-
-        Collections.addAll(EmplList, employee1, employee2, employee3);
-
-        Department department1 = new Department(1002, "sales");
-        Department department2 = new Department(1003, "marketing");
-        Department department3 = new Department(1004, "sales");
-
-        Collections.addAll(deptList, department1, department2, department3);
-    }
-}
-
-class Employee {
-    Integer employeeId;
-    String employeeName;
-
-    public Employee(Integer employeeId, String employeeName) {
-        super();
-        this.employeeId = employeeId;
-        this.employeeName = employeeName;
-    }
-
-    public Integer getEmployeeId() {
-        return employeeId;
-    }
-
-    public String getEmployeeName() {
-        return employeeName;
-    }
-
-}
-
-class Department {
-    Integer employeeId;
-    String department;
-
-    public Department(Integer employeeId, String department) {
-        super();
-        this.employeeId = employeeId;
-        this.department = department;
-    }
-
-    public Integer getEmployeeId() {
-        return employeeId;
-    }
-
-    public String getDepartment() {
-        return department;
-    }
-
+package com.baeldung.findItems;
+
+import static org.junit.Assert.assertEquals;
+
+import java.text.ParseException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+
+public class FindItemsBasedOnOtherStreamUnitTest {
+
+    private List<Employee> employeeList = new ArrayList<Employee>();
+
+    private List<Department> departmentList = new ArrayList<Department>();
+
+    @Test
+    public void givenDepartmentList_thenEmployeeListIsFilteredCorrectly() {
+        Integer expectedId = 1002;
+
+        populate(employeeList, departmentList);
+
+        List<Employee> filteredList = employeeList.stream()
+            .filter(empl -> departmentList.stream()
+                .anyMatch(dept -> dept.getDepartment()
+                    .equals("sales") && empl.getEmployeeId()
+                    .equals(dept.getEmployeeId())))
+            .collect(Collectors.toList());
+
+        assertEquals(expectedId, filteredList.get(0)
+            .getEmployeeId());
+    }
+
+    private void populate(List<Employee> EmplList, List<Department> deptList) {
+        Employee employee1 = new Employee(1001, "empl1");
+        Employee employee2 = new Employee(1002, "empl2");
+        Employee employee3 = new Employee(1003, "empl3");
+
+        Collections.addAll(EmplList, employee1, employee2, employee3);
+
+        Department department1 = new Department(1002, "sales");
+        Department department2 = new Department(1003, "marketing");
+        Department department3 = new Department(1004, "sales");
+
+        Collections.addAll(deptList, department1, department2, department3);
+    }
+}
+
+class Employee {
+    private Integer employeeId;
+    private String employeeName;
+
+    Employee(Integer employeeId, String employeeName) {
+        super();
+        this.employeeId = employeeId;
+        this.employeeName = employeeName;
+    }
+
+    Integer getEmployeeId() {
+        return employeeId;
+    }
+
+    public String getEmployeeName() {
+        return employeeName;
+    }
+
+}
+
+class Department {
+    private Integer employeeId;
+    private String department;
+
+    Department(Integer employeeId, String department) {
+        super();
+        this.employeeId = employeeId;
+        this.department = department;
+    }
+
+    Integer getEmployeeId() {
+        return employeeId;
+    }
+
+    String getDepartment() {
+        return department;
+    }
+
 }
\ No newline at end of file
diff --git a/core-java-concurrency/src/test/java/com/baeldung/completablefuture/CompletableFutureLongRunningUnitTest.java b/core-java-concurrency/src/test/java/com/baeldung/completablefuture/CompletableFutureLongRunningUnitTest.java
index 45d2ec68e4..d9cf8ae019 100644
--- a/core-java-concurrency/src/test/java/com/baeldung/completablefuture/CompletableFutureLongRunningUnitTest.java
+++ b/core-java-concurrency/src/test/java/com/baeldung/completablefuture/CompletableFutureLongRunningUnitTest.java
@@ -184,5 +184,25 @@ public class CompletableFutureLongRunningUnitTest {
 
         assertEquals("Hello World", future.get());
     }
+    
+    @Test
+    public void whenPassingTransformation_thenFunctionExecutionWithThenApply() throws InterruptedException, ExecutionException {
+        CompletableFuture<Integer> finalResult = compute().thenApply(s -> s + 1);
+        assertTrue(finalResult.get() == 11);
+    }
+    
+    @Test
+    public void whenPassingPreviousStage_thenFunctionExecutionWithThenCompose() throws InterruptedException, ExecutionException {
+        CompletableFuture<Integer> finalResult = compute().thenCompose(this::computeAnother);
+        assertTrue(finalResult.get() == 20);
+    }
+    
+    public CompletableFuture<Integer> compute(){
+        return CompletableFuture.supplyAsync(() -> 10);
+    }
+    
+    public CompletableFuture<Integer> computeAnother(Integer i){
+        return CompletableFuture.supplyAsync(() -> 10 + i);
+    }
 
 }
\ No newline at end of file
diff --git a/core-java/src/main/java/com/baeldung/array/ArrayReferenceGuide.java b/core-java/src/main/java/com/baeldung/array/ArrayReferenceGuide.java
new file mode 100644
index 0000000000..7d7dec85b0
--- /dev/null
+++ b/core-java/src/main/java/com/baeldung/array/ArrayReferenceGuide.java
@@ -0,0 +1,159 @@
+package com.baeldung.array;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+public class ArrayReferenceGuide {
+
+    public static void main(String[] args) {
+        declaration();
+
+        initialization();
+
+        access();
+
+        iterating();
+
+        varargs();
+
+        transformIntoList();
+
+        transformIntoStream();
+
+        sort();
+
+        search();
+
+        merge();
+    }
+
+    private static void declaration() {
+        int[] anArray;
+        int anotherArray[];
+    }
+
+    private static void initialization() {
+        int[] anArray = new int[10];
+        anArray[0] = 10;
+        anArray[5] = 4;
+
+        int[] anotherArray = new int[] {1, 2, 3, 4, 5};
+    }
+
+    private static void access() {
+        int[] anArray = new int[10];
+        anArray[0] = 10;
+        anArray[5] = 4;
+
+        System.out.println(anArray[0]);
+    }
+
+    private static void iterating() {
+        int[] anArray = new int[] {1, 2, 3, 4, 5};
+        for (int i = 0; i < anArray.length; i++) {
+            System.out.println(anArray[i]);
+        }
+
+        for (int element : anArray) {
+            System.out.println(element);
+        }
+    }
+
+    private static void varargs() {
+        String[] groceries = new String[] {"Milk", "Tomato", "Chips"};
+        varargMethod(groceries);
+        varargMethod("Milk", "Tomato", "Chips");
+    }
+
+    private static void varargMethod(String... varargs) {
+        for (String element : varargs) {
+            System.out.println(element);
+        }
+    }
+
+    private static void transformIntoList() {
+        Integer[] anArray = new Integer[] {1, 2, 3, 4, 5};
+
+        // Naïve implementation
+        List<Integer> aList = new ArrayList<>(); // We create an empty list
+        for (int element : anArray) {
+            // We iterate over array's elements and add them to the list
+            aList.add(element);
+        }
+
+        // Pretty implementation
+        aList = Arrays.asList(anArray);
+
+        // Drawbacks
+        try {
+            aList.remove(0);
+        } catch (UnsupportedOperationException e) {
+            System.out.println(e.getMessage());
+        }
+
+        try {
+            aList.add(6);
+        } catch (UnsupportedOperationException e) {
+            System.out.println(e.getMessage());
+        }
+
+        int[] anotherArray = new int[] {1, 2, 3, 4, 5};
+//        List<Integer> anotherList = Arrays.asList(anotherArray);
+    }
+
+    private static void transformIntoStream() {
+        int[] anArray = new int[] {1, 2, 3, 4, 5};
+        IntStream aStream = Arrays.stream(anArray);
+
+        Integer[] anotherArray = new Integer[] {1, 2, 3, 4, 5};
+        Stream<Integer> anotherStream = Arrays.stream(anotherArray, 2, 4);
+    }
+
+    private static void sort() {
+        int[] anArray = new int[] {5, 2, 1, 4, 8};
+        Arrays.sort(anArray); // anArray is now {1, 2, 4, 5, 8}
+
+        Integer[] anotherArray = new Integer[] {5, 2, 1, 4, 8};
+        Arrays.sort(anotherArray); // anArray is now {1, 2, 4, 5, 8}
+
+        String[] yetAnotherArray = new String[] {"A", "E", "Z", "B", "C"};
+        Arrays.sort(yetAnotherArray, 1, 3, Comparator.comparing(String::toString).reversed()); // yetAnotherArray is now {"A", "Z", "E", "B", "C"}
+    }
+
+    private static void search() {
+        int[] anArray = new int[] {5, 2, 1, 4, 8};
+        for (int i = 0; i < anArray.length; i++) {
+            if (anArray[i] == 4) {
+                System.out.println("Found at index " + i);
+                break;
+            }
+        }
+
+        Arrays.sort(anArray);
+        int index = Arrays.binarySearch(anArray, 4);
+        System.out.println("Found at index " + index);
+    }
+
+    private static void merge() {
+        int[] anArray = new int[] {5, 2, 1, 4, 8};
+        int[] anotherArray = new int[] {10, 4, 9, 11, 2};
+
+        int[] resultArray = new int[anArray.length + anotherArray.length];
+        for (int i = 0; i < resultArray.length; i++) {
+            resultArray[i] = (i < anArray.length ? anArray[i] : anotherArray[i - anArray.length]);
+        }
+        for (int element : resultArray) {
+            System.out.println(element);
+        }
+
+        Arrays.setAll(resultArray, i -> (i < anArray.length ? anArray[i] : anotherArray[i - anArray.length]));
+        for (int element : resultArray) {
+            System.out.println(element);
+        }
+    }
+
+}
diff --git a/core-java/src/main/java/com/baeldung/heapsort/Heap.java b/core-java/src/main/java/com/baeldung/heapsort/Heap.java
new file mode 100644
index 0000000000..95e0e1d8cd
--- /dev/null
+++ b/core-java/src/main/java/com/baeldung/heapsort/Heap.java
@@ -0,0 +1,136 @@
+package com.baeldung.heapsort;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Heap<E extends Comparable<E>> {
+
+    private List<E> elements = new ArrayList<>();
+
+    public static <E extends Comparable<E>> List<E> sort(Iterable<E> elements) {
+        Heap<E> heap = of(elements);
+
+        List<E> result = new ArrayList<>();
+
+        while (!heap.isEmpty()) {
+            result.add(heap.pop());
+        }
+
+        return result;
+    }
+
+    public static <E extends Comparable<E>> Heap<E> of(E... elements) {
+        return of(Arrays.asList(elements));
+    }
+
+    public static <E extends Comparable<E>> Heap<E> of(Iterable<E> elements) {
+        Heap<E> result = new Heap<>();
+        for (E element : elements) {
+            result.add(element);
+        }
+        return result;
+    }
+
+    public void add(E e) {
+        elements.add(e);
+        int elementIndex = elements.size() - 1;
+        while (!isRoot(elementIndex) && !isCorrectChild(elementIndex)) {
+            int parentIndex = parentIndex(elementIndex);
+            swap(elementIndex, parentIndex);
+            elementIndex = parentIndex;
+        }
+    }
+
+    public E pop() {
+        if (isEmpty()) {
+            throw new IllegalStateException("You cannot pop from an empty heap");
+        }
+
+        E result = elementAt(0);
+
+        int lasElementIndex = elements.size() - 1;
+        swap(0, lasElementIndex);
+        elements.remove(lasElementIndex);
+
+        int elementIndex = 0;
+        while (!isLeaf(elementIndex) && !isCorrectParent(elementIndex)) {
+            int smallerChildIndex = smallerChildIndex(elementIndex);
+            swap(elementIndex, smallerChildIndex);
+            elementIndex = smallerChildIndex;
+        }
+
+        return result;
+    }
+
+    public boolean isEmpty() {
+        return elements.isEmpty();
+    }
+    
+    private boolean isRoot(int index) {
+        return index == 0;
+    }
+
+    private int smallerChildIndex(int index) {
+        int leftChildIndex = leftChildIndex(index);
+        int rightChildIndex = rightChildIndex(index);
+        
+        if (!isValidIndex(rightChildIndex)) {
+            return leftChildIndex;
+        }
+
+        if (elementAt(leftChildIndex).compareTo(elementAt(rightChildIndex)) < 0) {
+            return leftChildIndex;
+        }
+
+        return rightChildIndex;
+    }
+
+    private boolean isLeaf(int index) {
+        return !isValidIndex(leftChildIndex(index));
+    }
+
+    private boolean isCorrectParent(int index) {
+        return isCorrect(index, leftChildIndex(index)) && isCorrect(index, rightChildIndex(index));
+    }
+
+    private boolean isCorrectChild(int index) {
+        return isCorrect(parentIndex(index), index);
+    }
+
+    private boolean isCorrect(int parentIndex, int childIndex) {
+        if (!isValidIndex(parentIndex) || !isValidIndex(childIndex)) {
+            return true;
+        }
+
+        return elementAt(parentIndex).compareTo(elementAt(childIndex)) < 0;
+    }
+
+    private boolean isValidIndex(int index) {
+        return index < elements.size();
+    }
+
+    private void swap(int index1, int index2) {
+        E element1 = elementAt(index1);
+        E element2 = elementAt(index2);
+        elements.set(index1, element2);
+        elements.set(index2, element1);
+    }
+
+    private E elementAt(int index) {
+        return elements.get(index);
+    }
+
+    private int parentIndex(int index) {
+        return (index - 1) / 2;
+    }
+
+    private int leftChildIndex(int index) {
+        return 2 * index + 1;
+    }
+
+    private int rightChildIndex(int index) {
+        return 2 * index + 2;
+    }
+
+}
diff --git a/core-java/src/test/java/com/baeldung/heapsort/HeapUnitTest.java b/core-java/src/test/java/com/baeldung/heapsort/HeapUnitTest.java
new file mode 100644
index 0000000000..cc3e49b6c9
--- /dev/null
+++ b/core-java/src/test/java/com/baeldung/heapsort/HeapUnitTest.java
@@ -0,0 +1,36 @@
+package com.baeldung.heapsort;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Test;
+
+public class HeapUnitTest {
+
+    @Test
+    public void givenNotEmptyHeap_whenPopCalled_thenItShouldReturnSmallestElement() {
+        // given
+        Heap<Integer> heap = Heap.of(3, 5, 1, 4, 2);
+
+        // when
+        int head = heap.pop();
+
+        // then
+        assertThat(head).isEqualTo(1);
+    }
+    
+    @Test
+    public void givenNotEmptyIterable_whenSortCalled_thenItShouldReturnElementsInSortedList() {
+        // given
+        List<Integer> elements = Arrays.asList(3, 5, 1, 4, 2);
+        
+        // when
+        List<Integer> sortedElements = Heap.sort(elements);
+        
+        // then
+        assertThat(sortedElements).isEqualTo(Arrays.asList(1, 2, 3, 4, 5));
+    }
+
+}
diff --git a/core-java/src/test/java/com/baeldung/modulo/ModuloUnitTest.java b/core-java/src/test/java/com/baeldung/modulo/ModuloUnitTest.java
new file mode 100644
index 0000000000..8b3685adf3
--- /dev/null
+++ b/core-java/src/test/java/com/baeldung/modulo/ModuloUnitTest.java
@@ -0,0 +1,54 @@
+package com.baeldung.modulo;
+
+import org.junit.Test;
+import static org.assertj.core.api.Java6Assertions.*;
+
+public class ModuloUnitTest {
+
+  @Test
+  public void whenIntegerDivision_thenLosesRemainder(){
+    assertThat(11 / 4).isEqualTo(2);
+  }
+
+  @Test
+  public void whenDoubleDivision_thenKeepsRemainder(){
+    assertThat(11 / 4.0).isEqualTo(2.75);
+  }
+
+  @Test
+  public void whenModulo_thenReturnsRemainder(){
+    assertThat(11 % 4).isEqualTo(3);
+  }
+
+  @Test(expected = ArithmeticException.class)
+  public void whenDivisionByZero_thenArithmeticException(){
+    double result = 1 / 0;
+  }
+
+  @Test(expected = ArithmeticException.class)
+  public void whenModuloByZero_thenArithmeticException(){
+    double result = 1 % 0;
+  }
+
+  @Test
+  public void whenDivisorIsOddAndModulusIs2_thenResultIs1(){
+    assertThat(3 % 2).isEqualTo(1);
+  }
+
+  @Test
+  public void whenDivisorIsEvenAndModulusIs2_thenResultIs0(){
+    assertThat(4 % 2).isEqualTo(0);
+  }
+
+  @Test
+  public void whenItemsIsAddedToCircularQueue_thenNoArrayIndexOutOfBounds(){
+    int QUEUE_CAPACITY= 10;
+    int[] circularQueue = new int[QUEUE_CAPACITY];
+    int itemsInserted = 0;
+    for (int value = 0; value < 1000; value++) {
+      int writeIndex = ++itemsInserted % QUEUE_CAPACITY;
+      circularQueue[writeIndex] = value;
+    }
+  }
+
+}
diff --git a/core-kotlin/src/main/kotlin/com/baeldung/interfaces/ConflictingInterfaces.kt b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/ConflictingInterfaces.kt
new file mode 100644
index 0000000000..630afbdae7
--- /dev/null
+++ b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/ConflictingInterfaces.kt
@@ -0,0 +1,23 @@
+package com.baeldung.interfaces
+
+interface BaseInterface {
+    fun someMethod(): String
+}
+
+interface FirstChildInterface : BaseInterface {
+    override fun someMethod(): String {
+        return("Hello, from someMethod in FirstChildInterface")
+    }
+}
+
+interface SecondChildInterface : BaseInterface {
+    override fun someMethod(): String {
+        return("Hello, from someMethod in SecondChildInterface")
+    }
+}
+
+class ChildClass : FirstChildInterface, SecondChildInterface {
+    override fun someMethod(): String {
+        return super<SecondChildInterface>.someMethod()
+    }
+}
\ No newline at end of file
diff --git a/core-kotlin/src/main/kotlin/com/baeldung/interfaces/InterfaceDelegation.kt b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/InterfaceDelegation.kt
new file mode 100644
index 0000000000..591fde0689
--- /dev/null
+++ b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/InterfaceDelegation.kt
@@ -0,0 +1,13 @@
+package com.baeldung.interfaces
+
+interface MyInterface {
+    fun someMethod(): String
+}
+
+class MyClass() : MyInterface {
+    override fun someMethod(): String {
+        return("Hello, World!")
+    }
+}
+
+class MyDerivedClass(myInterface: MyInterface) : MyInterface by myInterface
\ No newline at end of file
diff --git a/core-kotlin/src/main/kotlin/com/baeldung/interfaces/MultipleInterfaces.kt b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/MultipleInterfaces.kt
new file mode 100644
index 0000000000..105a85cbb3
--- /dev/null
+++ b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/MultipleInterfaces.kt
@@ -0,0 +1,29 @@
+package com.baeldung.interfaces
+
+interface FirstInterface {	
+    fun someMethod(): String
+	
+    fun anotherMethod(): String {
+        return("Hello, from anotherMethod in FirstInterface")
+    }
+}
+
+interface SecondInterface {
+    fun someMethod(): String {
+        return("Hello, from someMethod in SecondInterface")
+    }
+	
+    fun anotherMethod(): String {
+        return("Hello, from anotherMethod in SecondInterface")
+    }
+}
+
+class SomeClass: FirstInterface, SecondInterface {	
+    override fun someMethod(): String {
+        return("Hello, from someMethod in SomeClass")
+    }
+	
+    override fun anotherMethod(): String {
+        return("Hello, from anotherMethod in SomeClass")
+    }
+}
\ No newline at end of file
diff --git a/core-kotlin/src/main/kotlin/com/baeldung/interfaces/SimpleInterface.kt b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/SimpleInterface.kt
new file mode 100644
index 0000000000..0758549dde
--- /dev/null
+++ b/core-kotlin/src/main/kotlin/com/baeldung/interfaces/SimpleInterface.kt
@@ -0,0 +1,24 @@
+package com.baeldung.interfaces
+
+interface SimpleInterface {
+    val firstProp: String
+    val secondProp: String
+        get() = "Second Property"
+    fun firstMethod(): String
+    fun secondMethod(): String {
+        println("Hello, from: " + secondProp)
+        return ""
+    }
+}
+
+class SimpleClass: SimpleInterface {
+    override val firstProp: String = "First Property"
+    override val secondProp: String
+        get() = "Second Property, Overridden!"
+    override fun firstMethod(): String {
+        return("Hello, from: " + firstProp)
+    }
+    override fun secondMethod(): String {
+        return("Hello, from: " + secondProp + firstProp)
+    }
+}
\ No newline at end of file
diff --git a/core-kotlin/src/test/kotlin/com/baeldung/interfaces/InterfaceExamplesUnitTest.kt b/core-kotlin/src/test/kotlin/com/baeldung/interfaces/InterfaceExamplesUnitTest.kt
new file mode 100644
index 0000000000..96b99948b7
--- /dev/null
+++ b/core-kotlin/src/test/kotlin/com/baeldung/interfaces/InterfaceExamplesUnitTest.kt
@@ -0,0 +1,32 @@
+package com.baeldung.interfaces
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class InterfaceExamplesUnitTest {
+    @Test
+    fun givenAnInterface_whenImplemented_thenBehavesAsOverridden() {
+        val simpleClass = SimpleClass()
+        assertEquals("Hello, from: First Property", simpleClass.firstMethod())
+        assertEquals("Hello, from: Second Property, Overridden!First Property", simpleClass.secondMethod())
+    }
+
+    @Test
+    fun givenMultipleInterfaces_whenImplemented_thenBehavesAsOverridden() {
+        val someClass = SomeClass()
+        assertEquals("Hello, from someMethod in SomeClass", someClass.someMethod())
+        assertEquals("Hello, from anotherMethod in SomeClass", someClass.anotherMethod())
+    }
+
+    @Test
+    fun givenConflictingInterfaces_whenImplemented_thenBehavesAsOverridden() {
+        val childClass = ChildClass()
+        assertEquals("Hello, from someMethod in SecondChildInterface", childClass.someMethod())
+    }
+
+    @Test
+    fun givenAnInterface_whenImplemented_thenBehavesAsDelegated() {
+        val myClass = MyClass()
+        assertEquals("Hello, World!", MyDerivedClass(myClass).someMethod())
+    }
+}
\ No newline at end of file
diff --git a/guava-collections/.gitignore b/guava-collections/.gitignore
new file mode 100644
index 0000000000..83c05e60c8
--- /dev/null
+++ b/guava-collections/.gitignore
@@ -0,0 +1,13 @@
+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear
\ No newline at end of file
diff --git a/guava-collections/README.md b/guava-collections/README.md
new file mode 100644
index 0000000000..eb1eb1d35c
--- /dev/null
+++ b/guava-collections/README.md
@@ -0,0 +1,20 @@
+=========
+
+## Guava and Hamcrest Cookbooks and Examples
+
+
+### Relevant Articles: 
+- [Guava Collections Cookbook](http://www.baeldung.com/guava-collections)
+- [Guava Ordering Cookbook](http://www.baeldung.com/guava-order)
+- [Hamcrest Collections Cookbook](http://www.baeldung.com/hamcrest-collections-arrays)
+- [Partition a List in Java](http://www.baeldung.com/java-list-split)
+- [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)
\ No newline at end of file
diff --git a/guava-collections/pom.xml b/guava-collections/pom.xml
new file mode 100644
index 0000000000..a717023156
--- /dev/null
+++ b/guava-collections/pom.xml
@@ -0,0 +1,66 @@
+<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</groupId>
+    <artifactId>guava-collections</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>guava-collections</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <!-- utils -->
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <!-- https://mvnrepository.com/artifact/org.hamcrest/java-hamcrest -->
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>java-hamcrest</artifactId>
+            <version>${java-hamcrest.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>guava</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <!-- util -->
+        <guava.version>24.0-jre</guava.version>
+        <commons-lang3.version>3.5</commons-lang3.version>
+        <commons-collections4.version>4.1</commons-collections4.version>
+
+        <!-- testing -->
+        <assertj.version>3.6.1</assertj.version>
+        <java-hamcrest.version>2.0.0.0</java-hamcrest.version>
+    </properties>
+
+</project>
\ No newline at end of file
diff --git a/guava-collections/src/main/resources/logback.xml b/guava-collections/src/main/resources/logback.xml
new file mode 100644
index 0000000000..56af2d397e
--- /dev/null
+++ b/guava-collections/src/main/resources/logback.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <logger name="org.springframework" level="WARN" />
+    <logger name="org.springframework.transaction" level="WARN" />
+
+    <!-- in order to debug some marshalling issues, this needs to be TRACE -->
+    <logger name="org.springframework.web.servlet.mvc" level="WARN" />
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>
\ No newline at end of file
diff --git a/guava/src/test/java/org/baeldung/guava/EvictingQueueUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/EvictingQueueUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/EvictingQueueUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/EvictingQueueUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaCollectionTypesUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaCollectionTypesUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaCollectionTypesUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaCollectionTypesUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaCollectionsExamplesUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaCollectionsExamplesUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaCollectionsExamplesUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaCollectionsExamplesUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaFilterTransformCollectionsUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaFilterTransformCollectionsUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaFilterTransformCollectionsUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaFilterTransformCollectionsUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaMapFromSet.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaMapFromSet.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaMapFromSet.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaMapFromSet.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaMapFromSetUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaMapFromSetUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaMapFromSetUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaMapFromSetUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaMapInitializeUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaMapInitializeUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaMapInitializeUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaMapInitializeUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaMultiMapUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaMultiMapUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaMultiMapUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaMultiMapUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaOrderingExamplesUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaOrderingExamplesUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaOrderingExamplesUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaOrderingExamplesUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaOrderingUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaOrderingUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaOrderingUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaOrderingUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaRangeMapUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaRangeMapUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaRangeMapUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaRangeMapUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaRangeSetUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaRangeSetUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaRangeSetUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaRangeSetUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/GuavaStringUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/GuavaStringUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/GuavaStringUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/GuavaStringUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/guava/MinMaxPriorityQueueUnitTest.java b/guava-collections/src/test/java/org/baeldung/guava/MinMaxPriorityQueueUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/guava/MinMaxPriorityQueueUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/guava/MinMaxPriorityQueueUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/hamcrest/HamcrestExamplesUnitTest.java b/guava-collections/src/test/java/org/baeldung/hamcrest/HamcrestExamplesUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/hamcrest/HamcrestExamplesUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/hamcrest/HamcrestExamplesUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/java/CollectionApachePartitionUnitTest.java b/guava-collections/src/test/java/org/baeldung/java/CollectionApachePartitionUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/java/CollectionApachePartitionUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/java/CollectionApachePartitionUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/java/CollectionGuavaPartitionUnitTest.java b/guava-collections/src/test/java/org/baeldung/java/CollectionGuavaPartitionUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/java/CollectionGuavaPartitionUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/java/CollectionGuavaPartitionUnitTest.java
diff --git a/guava/src/test/java/org/baeldung/java/CollectionJavaPartitionUnitTest.java b/guava-collections/src/test/java/org/baeldung/java/CollectionJavaPartitionUnitTest.java
similarity index 100%
rename from guava/src/test/java/org/baeldung/java/CollectionJavaPartitionUnitTest.java
rename to guava-collections/src/test/java/org/baeldung/java/CollectionJavaPartitionUnitTest.java
diff --git a/guava-collections/src/test/resources/.gitignore b/guava-collections/src/test/resources/.gitignore
new file mode 100644
index 0000000000..83c05e60c8
--- /dev/null
+++ b/guava-collections/src/test/resources/.gitignore
@@ -0,0 +1,13 @@
+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear
\ No newline at end of file
diff --git a/guava-collections/src/test/resources/test.out b/guava-collections/src/test/resources/test.out
new file mode 100644
index 0000000000..7a79da3803
--- /dev/null
+++ b/guava-collections/src/test/resources/test.out
@@ -0,0 +1 @@
+John Jane Adam Tom 
\ No newline at end of file
diff --git a/guava-collections/src/test/resources/test1.in b/guava-collections/src/test/resources/test1.in
new file mode 100644
index 0000000000..70c379b63f
--- /dev/null
+++ b/guava-collections/src/test/resources/test1.in
@@ -0,0 +1 @@
+Hello world
\ No newline at end of file
diff --git a/guava-collections/src/test/resources/test1_1.in b/guava-collections/src/test/resources/test1_1.in
new file mode 100644
index 0000000000..8318c86b35
--- /dev/null
+++ b/guava-collections/src/test/resources/test1_1.in
@@ -0,0 +1 @@
+Test
\ No newline at end of file
diff --git a/guava-collections/src/test/resources/test2.in b/guava-collections/src/test/resources/test2.in
new file mode 100644
index 0000000000..622efea9e6
--- /dev/null
+++ b/guava-collections/src/test/resources/test2.in
@@ -0,0 +1,4 @@
+John
+Jane
+Adam
+Tom
\ No newline at end of file
diff --git a/guava-collections/src/test/resources/test_copy.in b/guava-collections/src/test/resources/test_copy.in
new file mode 100644
index 0000000000..70c379b63f
--- /dev/null
+++ b/guava-collections/src/test/resources/test_copy.in
@@ -0,0 +1 @@
+Hello world
\ No newline at end of file
diff --git a/guava-collections/src/test/resources/test_le.txt b/guava-collections/src/test/resources/test_le.txt
new file mode 100644
index 0000000000..f7cc484bf4
Binary files /dev/null and b/guava-collections/src/test/resources/test_le.txt differ
diff --git a/guava/README.md b/guava/README.md
index fe1a347d72..7501bf08de 100644
--- a/guava/README.md
+++ b/guava/README.md
@@ -4,33 +4,19 @@
 
 
 ### Relevant Articles: 
-- [Guava Collections Cookbook](http://www.baeldung.com/guava-collections)
-- [Guava Ordering Cookbook](http://www.baeldung.com/guava-order)
 - [Guava Functional Cookbook](http://www.baeldung.com/guava-functions-predicates)
-- [Hamcrest Collections Cookbook](http://www.baeldung.com/hamcrest-collections-arrays)
-- [Partition a List in Java](http://www.baeldung.com/java-list-split)
-- [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 – Write to File, Read from File](http://www.baeldung.com/guava-write-to-file-read-from-file)
-- [Guava – Lists](http://www.baeldung.com/guava-lists)
-- [Guava – Sets](http://www.baeldung.com/guava-sets)
-- [Guava – Maps](http://www.baeldung.com/guava-maps)
 - [Guava Set + Function = Map](http://www.baeldung.com/guava-set-function-map-tutorial)
 - [Guide to Guava’s Ordering](http://www.baeldung.com/guava-ordering)
 - [Guide to Guava’s PreConditions](http://www.baeldung.com/guava-preconditions)
 - [Introduction to Guava CacheLoader](http://www.baeldung.com/guava-cacheloader)
 - [Introduction to Guava Memoizer](http://www.baeldung.com/guava-memoizer)
 - [Guide to Guava’s EventBus](http://www.baeldung.com/guava-eventbus)
-- [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 Table](http://www.baeldung.com/guava-table)
 - [Guide to Guava’s Reflection Utilities](http://www.baeldung.com/guava-reflection)
 - [Guide to Guava ClassToInstanceMap](http://www.baeldung.com/guava-class-to-instance-map)
-- [Guide to Guava MinMaxPriorityQueue and EvictingQueue](http://www.baeldung.com/guava-minmax-priority-queue-and-evicting-queue)
 - [Guide to Mathematical Utilities in Guava](http://www.baeldung.com/guava-math)
 - [Bloom Filter in Java using Guava](http://www.baeldung.com/guava-bloom-filter)
 - [Using Guava CountingOutputStream](http://www.baeldung.com/guava-counting-outputstream)
 - [Hamcrest Text Matchers](http://www.baeldung.com/hamcrest-text-matchers)
 - [Quick Guide to the Guava RateLimiter](http://www.baeldung.com/guava-rate-limiter)
-- [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
diff --git a/guava/pom.xml b/guava/pom.xml
index 60678608dd..1d37a79ab6 100644
--- a/guava/pom.xml
+++ b/guava/pom.xml
@@ -14,12 +14,6 @@
     </parent>
 
     <dependencies>
-        <!-- utils -->
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-collections4</artifactId>
-            <version>${commons-collections4.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
@@ -56,7 +50,6 @@
         <!-- util -->
         <guava.version>24.0-jre</guava.version>
         <commons-lang3.version>3.5</commons-lang3.version>
-        <commons-collections4.version>4.1</commons-collections4.version>
 
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
diff --git a/javaxval/README.md b/javaxval/README.md
index 3153546c7d..3a975022ad 100644
--- a/javaxval/README.md
+++ b/javaxval/README.md
@@ -9,3 +9,4 @@ The "REST With Spring" Classes: http://bit.ly/restwithspring
 - [Java Bean Validation Basics](http://www.baeldung.com/javax-validation)
 - [Validating Container Elements with Bean Validation 2.0](http://www.baeldung.com/bean-validation-container-elements)
 - [Method Constraints with Bean Validation 2.0](http://www.baeldung.com/javax-validation-method-constraints)
+- [Difference Between @NotNull, @NotEmpty, and @NotBlank Constraints in Bean Validation](https://www.baeldung.com/java-bean-validation-not-null-empty-blank)
diff --git a/libraries/pom.xml b/libraries/pom.xml
index 91c54b6113..6bbe8e6f1c 100644
--- a/libraries/pom.xml
+++ b/libraries/pom.xml
@@ -358,6 +358,7 @@
         <dependency>
             <groupId>org.codehaus.groovy</groupId>
             <artifactId>groovy-all</artifactId>
+            <type>pom</type>
             <version>${groovy.version}</version>
         </dependency>
         <dependency>
@@ -922,7 +923,7 @@
         <quartz.version>2.3.0</quartz.version>
         <jool.version>0.9.12</jool.version>
         <jmh.version>1.19</jmh.version>
-        <groovy.version>2.4.10</groovy.version>
+        <groovy.version>2.5.2</groovy.version>
         <noexception.version>1.1.0</noexception.version>
         <logging-interceptor.version>3.9.0</logging-interceptor.version>
         <yarg.version>2.0.4</yarg.version>
diff --git a/libraries/src/test/java/com/baeldung/commons/lang3/test/SystemsUtilsUnitTest.java b/libraries/src/test/java/com/baeldung/commons/lang3/test/SystemsUtilsManualTest.java
similarity index 86%
rename from libraries/src/test/java/com/baeldung/commons/lang3/test/SystemsUtilsUnitTest.java
rename to libraries/src/test/java/com/baeldung/commons/lang3/test/SystemsUtilsManualTest.java
index 0efe97f912..cb45ebc24d 100644
--- a/libraries/src/test/java/com/baeldung/commons/lang3/test/SystemsUtilsUnitTest.java
+++ b/libraries/src/test/java/com/baeldung/commons/lang3/test/SystemsUtilsManualTest.java
@@ -6,8 +6,10 @@ import org.apache.commons.lang3.SystemUtils;
 import static org.assertj.core.api.Assertions.assertThat;
 import org.junit.Test;
 
-public class SystemsUtilsUnitTest {
+public class SystemsUtilsManualTest {
 
+	// the paths depend on the OS and installed version of Java
+	
     @Test
     public void givenSystemUtilsClass_whenCalledgetJavaHome_thenCorrect() {
         assertThat(SystemUtils.getJavaHome()).isEqualTo(new File("/usr/lib/jvm/java-8-oracle/jre"));
diff --git a/logging-modules/log4j2/${sys:logging.folder.path} b/logging-modules/log4j2/${sys
old mode 100755
new mode 100644
similarity index 100%
rename from logging-modules/log4j2/${sys:logging.folder.path}
rename to logging-modules/log4j2/${sys
diff --git a/parent-boot-1/pom.xml b/parent-boot-1/pom.xml
index 7742841d07..d220b4a6b7 100644
--- a/parent-boot-1/pom.xml
+++ b/parent-boot-1/pom.xml
@@ -17,7 +17,7 @@
 			<dependency>
 				<groupId>org.springframework.boot</groupId>
 				<artifactId>spring-boot-dependencies</artifactId>
-				<version>1.5.15.RELEASE</version>
+				<version>1.5.16.RELEASE</version>
 				<type>pom</type>
 				<scope>import</scope>
 			</dependency>
diff --git a/pom.xml b/pom.xml
index b5fcc5f3ca..9fde092896 100644
--- a/pom.xml
+++ b/pom.xml
@@ -46,6 +46,12 @@
 			<version>${junit-jupiter.version}</version>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-params</artifactId>
+			<version>${junit-jupiter.version}</version>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>
@@ -373,6 +379,7 @@
 				<module>google-web-toolkit</module>
 				<module>gson</module>
 				<module>guava</module>
+				<module>guava-collections</module>
 				<module>guava-modules/guava-18</module>
 				<module>guava-modules/guava-19</module>
 				<module>guava-modules/guava-21</module>
@@ -1280,6 +1287,7 @@
 				<module>google-cloud</module>
 				<module>gson</module>
 				<module>guava</module>
+				<module>guava-collections</module>
 				<module>guava-modules/guava-18</module>
 				<module>guava-modules/guava-19</module>
 				<module>guava-modules/guava-21</module>
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/FunctionalValidationsApplication.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/FunctionalValidationsApplication.java
new file mode 100644
index 0000000000..e548e33c85
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/FunctionalValidationsApplication.java
@@ -0,0 +1,12 @@
+package com.baeldung.validations.functional;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class FunctionalValidationsApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(FunctionalValidationsApplication.class, args);
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/AbstractValidationHandler.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/AbstractValidationHandler.java
new file mode 100644
index 0000000000..f34c1ee8d8
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/AbstractValidationHandler.java
@@ -0,0 +1,45 @@
+package com.baeldung.validations.functional.handlers;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.validation.BeanPropertyBindingResult;
+import org.springframework.validation.Errors;
+import org.springframework.validation.Validator;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.reactive.function.server.ServerResponse;
+import org.springframework.web.server.ResponseStatusException;
+
+import reactor.core.publisher.Mono;
+
+public abstract class AbstractValidationHandler<T, U extends Validator> {
+
+    private final Class<T> validationClass;
+
+    private final U validator;
+
+    protected AbstractValidationHandler(Class<T> clazz, U validator) {
+        this.validationClass = clazz;
+        this.validator = validator;
+    }
+
+    abstract protected Mono<ServerResponse> processBody(T validBody, final ServerRequest originalRequest);
+
+    public final Mono<ServerResponse> handleRequest(final ServerRequest request) {
+        return request.bodyToMono(this.validationClass)
+            .flatMap(body -> {
+                Errors errors = new BeanPropertyBindingResult(body, this.validationClass.getName());
+                this.validator.validate(body, errors);
+
+                if (errors == null || errors.getAllErrors()
+                    .isEmpty()) {
+                    return processBody(body, request);
+                } else {
+                    return onValidationErrors(errors, body, request);
+                }
+            });
+    }
+
+    protected Mono<ServerResponse> onValidationErrors(Errors errors, T invalidBody, final ServerRequest request) {
+        throw new ResponseStatusException(HttpStatus.BAD_REQUEST, errors.getAllErrors()
+            .toString());
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/FunctionalHandler.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/FunctionalHandler.java
new file mode 100644
index 0000000000..d7e3bd0bc0
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/FunctionalHandler.java
@@ -0,0 +1,43 @@
+package com.baeldung.validations.functional.handlers;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Component;
+import org.springframework.validation.BeanPropertyBindingResult;
+import org.springframework.validation.Errors;
+import org.springframework.validation.Validator;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.reactive.function.server.ServerResponse;
+import org.springframework.web.server.ResponseStatusException;
+
+import com.baeldung.validations.functional.model.CustomRequestEntity;
+import com.baeldung.validations.functional.validators.CustomRequestEntityValidator;
+
+import reactor.core.publisher.Mono;
+
+@Component
+public class FunctionalHandler {
+
+    public Mono<ServerResponse> handleRequest(final ServerRequest request) {
+        Validator validator = new CustomRequestEntityValidator();
+        Mono<String> responseBody = request.bodyToMono(CustomRequestEntity.class)
+            .map(body -> {
+                Errors errors = new BeanPropertyBindingResult(body, CustomRequestEntity.class.getName());
+                validator.validate(body, errors);
+
+                if (errors == null || errors.getAllErrors()
+                    .isEmpty()) {
+                    return String.format("Hi, %s [%s]!", body.getName(), body.getCode());
+
+                } else {
+                    throw new ResponseStatusException(HttpStatus.BAD_REQUEST, errors.getAllErrors()
+                        .toString());
+                }
+
+            });
+        return ServerResponse.ok()
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(responseBody, String.class);
+
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/AnnotatedRequestEntityValidationHandler.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/AnnotatedRequestEntityValidationHandler.java
new file mode 100644
index 0000000000..2011679741
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/AnnotatedRequestEntityValidationHandler.java
@@ -0,0 +1,30 @@
+package com.baeldung.validations.functional.handlers.impl;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Component;
+import org.springframework.validation.Validator;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.reactive.function.server.ServerResponse;
+
+import com.baeldung.validations.functional.handlers.AbstractValidationHandler;
+import com.baeldung.validations.functional.model.AnnotatedRequestEntity;
+
+import reactor.core.publisher.Mono;
+
+@Component
+public class AnnotatedRequestEntityValidationHandler extends AbstractValidationHandler<AnnotatedRequestEntity, Validator> {
+
+    private AnnotatedRequestEntityValidationHandler(@Autowired Validator validator) {
+        super(AnnotatedRequestEntity.class, validator);
+    }
+
+    @Override
+    protected Mono<ServerResponse> processBody(AnnotatedRequestEntity validBody, ServerRequest originalRequest) {
+        String responseBody = String.format("Hi, %s. Password: %s!", validBody.getUser(), validBody.getPassword());
+        return ServerResponse.ok()
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(Mono.just(responseBody), String.class);
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/CustomRequestEntityValidationHandler.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/CustomRequestEntityValidationHandler.java
new file mode 100644
index 0000000000..34630c60b2
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/CustomRequestEntityValidationHandler.java
@@ -0,0 +1,37 @@
+package com.baeldung.validations.functional.handlers.impl;
+
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Component;
+import org.springframework.validation.Errors;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.reactive.function.server.ServerResponse;
+
+import com.baeldung.validations.functional.handlers.AbstractValidationHandler;
+import com.baeldung.validations.functional.model.CustomRequestEntity;
+import com.baeldung.validations.functional.validators.CustomRequestEntityValidator;
+
+import reactor.core.publisher.Mono;
+
+@Component
+public class CustomRequestEntityValidationHandler extends AbstractValidationHandler<CustomRequestEntity, CustomRequestEntityValidator> {
+
+    private CustomRequestEntityValidationHandler() {
+        super(CustomRequestEntity.class, new CustomRequestEntityValidator());
+    }
+
+    @Override
+    protected Mono<ServerResponse> processBody(CustomRequestEntity validBody, ServerRequest originalRequest) {
+        String responseBody = String.format("Hi, %s [%s]!", validBody.getName(), validBody.getCode());
+        return ServerResponse.ok()
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(Mono.just(responseBody), String.class);
+    }
+
+    @Override
+    protected Mono<ServerResponse> onValidationErrors(Errors errors, CustomRequestEntity invalidBody, final ServerRequest request) {
+        return ServerResponse.badRequest()
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(Mono.just(String.format("Custom message showing the errors: %s", errors.getAllErrors()
+                .toString())), String.class);
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/OtherEntityValidationHandler.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/OtherEntityValidationHandler.java
new file mode 100644
index 0000000000..0196287d13
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/handlers/impl/OtherEntityValidationHandler.java
@@ -0,0 +1,28 @@
+package com.baeldung.validations.functional.handlers.impl;
+
+import org.springframework.http.MediaType;
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.reactive.function.server.ServerResponse;
+
+import com.baeldung.validations.functional.handlers.AbstractValidationHandler;
+import com.baeldung.validations.functional.model.OtherEntity;
+import com.baeldung.validations.functional.validators.OtherEntityValidator;
+
+import reactor.core.publisher.Mono;
+
+@Component
+public class OtherEntityValidationHandler extends AbstractValidationHandler<OtherEntity, OtherEntityValidator> {
+
+    private OtherEntityValidationHandler() {
+        super(OtherEntity.class, new OtherEntityValidator());
+    }
+
+    @Override
+    protected Mono<ServerResponse> processBody(OtherEntity validBody, ServerRequest originalRequest) {
+        String responseBody = String.format("Other object with item %s and quantity %s!", validBody.getItem(), validBody.getQuantity());
+        return ServerResponse.ok()
+            .contentType(MediaType.APPLICATION_JSON)
+            .body(Mono.just(responseBody), String.class);
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/AnnotatedRequestEntity.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/AnnotatedRequestEntity.java
new file mode 100644
index 0000000000..992f07481c
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/AnnotatedRequestEntity.java
@@ -0,0 +1,23 @@
+package com.baeldung.validations.functional.model;
+
+import javax.validation.constraints.NotNull;
+import javax.validation.constraints.Size;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@AllArgsConstructor
+@NoArgsConstructor
+@Getter
+@Setter
+public class AnnotatedRequestEntity {
+    @NotNull
+    private String user;
+
+    @NotNull
+    @Size(min = 4, max = 7)
+    private String password;
+
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/CustomRequestEntity.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/CustomRequestEntity.java
new file mode 100644
index 0000000000..ed459f121b
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/CustomRequestEntity.java
@@ -0,0 +1,17 @@
+package com.baeldung.validations.functional.model;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@AllArgsConstructor
+@NoArgsConstructor
+@Getter
+@Setter
+public class CustomRequestEntity {
+    
+    private String name;
+    private String code;
+    
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/OtherEntity.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/OtherEntity.java
new file mode 100644
index 0000000000..78667cb13d
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/model/OtherEntity.java
@@ -0,0 +1,17 @@
+package com.baeldung.validations.functional.model;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@AllArgsConstructor
+@NoArgsConstructor
+@Getter
+@Setter
+public class OtherEntity {
+    
+    private String item;
+    private Integer quantity;
+    
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/routers/ValidationsRouters.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/routers/ValidationsRouters.java
new file mode 100644
index 0000000000..efbdbe3f99
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/routers/ValidationsRouters.java
@@ -0,0 +1,29 @@
+package com.baeldung.validations.functional.routers;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.reactive.function.server.RequestPredicates;
+import org.springframework.web.reactive.function.server.RouterFunction;
+import org.springframework.web.reactive.function.server.RouterFunctions;
+import org.springframework.web.reactive.function.server.ServerResponse;
+
+import com.baeldung.validations.functional.handlers.FunctionalHandler;
+import com.baeldung.validations.functional.handlers.impl.AnnotatedRequestEntityValidationHandler;
+import com.baeldung.validations.functional.handlers.impl.CustomRequestEntityValidationHandler;
+import com.baeldung.validations.functional.handlers.impl.OtherEntityValidationHandler;
+
+@Configuration
+public class ValidationsRouters {
+
+    @Bean
+    public RouterFunction<ServerResponse> responseHeaderRoute(@Autowired CustomRequestEntityValidationHandler dryHandler,
+        @Autowired FunctionalHandler complexHandler,
+        @Autowired OtherEntityValidationHandler otherHandler,
+        @Autowired AnnotatedRequestEntityValidationHandler annotatedEntityHandler) {
+        return RouterFunctions.route(RequestPredicates.POST("/complex-handler-functional-validation"), complexHandler::handleRequest)
+            .andRoute(RequestPredicates.POST("/dry-functional-validation"), dryHandler::handleRequest)
+            .andRoute(RequestPredicates.POST("/other-dry-functional-validation"), otherHandler::handleRequest)
+            .andRoute(RequestPredicates.POST("/annotated-functional-validation"), annotatedEntityHandler::handleRequest);
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/validators/CustomRequestEntityValidator.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/validators/CustomRequestEntityValidator.java
new file mode 100644
index 0000000000..085d477318
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/validators/CustomRequestEntityValidator.java
@@ -0,0 +1,29 @@
+package com.baeldung.validations.functional.validators;
+
+import org.springframework.validation.Errors;
+import org.springframework.validation.ValidationUtils;
+import org.springframework.validation.Validator;
+
+import com.baeldung.validations.functional.model.CustomRequestEntity;
+
+public class CustomRequestEntityValidator implements Validator {
+
+    private static final int MINIMUM_CODE_LENGTH = 6;
+    
+    @Override
+    public boolean supports(Class<?> clazz) {
+        return CustomRequestEntity.class.isAssignableFrom(clazz);
+    }
+
+    @Override
+    public void validate(Object target, Errors errors) {
+        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "name", "field.required");
+        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "code", "field.required");
+        CustomRequestEntity request = (CustomRequestEntity) target;
+        if (request.getCode() != null && request.getCode()
+            .trim()
+            .length() < MINIMUM_CODE_LENGTH) {
+            errors.rejectValue("code", "field.min.length", new Object[] { Integer.valueOf(MINIMUM_CODE_LENGTH) }, "The code must be at least [" + MINIMUM_CODE_LENGTH + "] characters in length.");
+        }
+    }
+}
diff --git a/spring-5-reactive/src/main/java/com/baeldung/validations/functional/validators/OtherEntityValidator.java b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/validators/OtherEntityValidator.java
new file mode 100644
index 0000000000..18c2c28cfe
--- /dev/null
+++ b/spring-5-reactive/src/main/java/com/baeldung/validations/functional/validators/OtherEntityValidator.java
@@ -0,0 +1,27 @@
+package com.baeldung.validations.functional.validators;
+
+import org.springframework.validation.Errors;
+import org.springframework.validation.ValidationUtils;
+import org.springframework.validation.Validator;
+
+import com.baeldung.validations.functional.model.OtherEntity;
+
+public class OtherEntityValidator implements Validator {
+
+    private static final int MIN_ITEM_QUANTITY = 1;
+
+    @Override
+    public boolean supports(Class<?> clazz) {
+        return OtherEntity.class.isAssignableFrom(clazz);
+    }
+
+    @Override
+    public void validate(Object target, Errors errors) {
+        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "item", "field.required");
+        ValidationUtils.rejectIfEmptyOrWhitespace(errors, "quantity", "field.required");
+        OtherEntity request = (OtherEntity) target;
+        if (request.getQuantity() != null && request.getQuantity() < MIN_ITEM_QUANTITY) {
+            errors.rejectValue("quantity", "field.min.length", new Object[] { Integer.valueOf(MIN_ITEM_QUANTITY) }, "There must be at least one item");
+        }
+    }
+}
diff --git a/spring-5-reactive/src/test/java/com/baeldung/validations/functional/FunctionalEndpointValidationsLiveTest.java b/spring-5-reactive/src/test/java/com/baeldung/validations/functional/FunctionalEndpointValidationsLiveTest.java
new file mode 100644
index 0000000000..5fe764bf8f
--- /dev/null
+++ b/spring-5-reactive/src/test/java/com/baeldung/validations/functional/FunctionalEndpointValidationsLiveTest.java
@@ -0,0 +1,111 @@
+package com.baeldung.validations.functional;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
+import org.springframework.test.web.reactive.server.WebTestClient.ResponseSpec;
+
+import com.baeldung.validations.functional.model.AnnotatedRequestEntity;
+import com.baeldung.validations.functional.model.CustomRequestEntity;
+
+import reactor.core.publisher.Mono;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+public class FunctionalEndpointValidationsLiveTest {
+
+    private static final String BASE_URL = "http://localhost:8080";
+    private static final String COMPLEX_EP_URL = BASE_URL + "/complex-handler-functional-validation";
+    private static final String DRY_EP_URL = BASE_URL + "/dry-functional-validation";
+    private static final String ANNOTATIONS_EP_URL = BASE_URL + "/annotated-functional-validation";
+
+    private static WebTestClient client;
+
+    @BeforeAll
+    public static void setup() {
+        client = WebTestClient.bindToServer()
+            .baseUrl(BASE_URL)
+            .build();
+    }
+
+    @Test
+    public void whenRequestingDryEPWithInvalidBody_thenObtainBadRequest() {
+        CustomRequestEntity body = new CustomRequestEntity("name", "123");
+
+        ResponseSpec response = client.post()
+            .uri(DRY_EP_URL)
+            .body(Mono.just(body), CustomRequestEntity.class)
+            .exchange();
+
+        response.expectStatus()
+            .isBadRequest();
+    }
+
+    @Test
+    public void whenRequestingComplexEPWithInvalidBody_thenObtainBadRequest() {
+        CustomRequestEntity body = new CustomRequestEntity("name", "123");
+
+        ResponseSpec response = client.post()
+            .uri(COMPLEX_EP_URL)
+            .body(Mono.just(body), CustomRequestEntity.class)
+            .exchange();
+
+        response.expectStatus()
+            .isBadRequest();
+    }
+
+    @Test
+    public void whenRequestingAnnotatedEPWithInvalidBody_thenObtainBadRequest() {
+        AnnotatedRequestEntity body = new AnnotatedRequestEntity("user", "passwordlongerthan7digits");
+
+        ResponseSpec response = client.post()
+            .uri(ANNOTATIONS_EP_URL)
+            .body(Mono.just(body), AnnotatedRequestEntity.class)
+            .exchange();
+
+        response.expectStatus()
+            .isBadRequest();
+    }
+
+    @Test
+    public void whenRequestingDryEPWithValidBody_thenObtainBadRequest() {
+        CustomRequestEntity body = new CustomRequestEntity("name", "1234567");
+
+        ResponseSpec response = client.post()
+            .uri(DRY_EP_URL)
+            .body(Mono.just(body), CustomRequestEntity.class)
+            .exchange();
+
+        response.expectStatus()
+            .isOk();
+    }
+
+    @Test
+    public void whenRequestingComplexEPWithValidBody_thenObtainBadRequest() {
+        CustomRequestEntity body = new CustomRequestEntity("name", "1234567");
+
+        ResponseSpec response = client.post()
+            .uri(COMPLEX_EP_URL)
+            .body(Mono.just(body), CustomRequestEntity.class)
+            .exchange();
+
+        response.expectStatus()
+            .isOk();
+    }
+
+    @Test
+    public void whenRequestingAnnotatedEPWithValidBody_thenObtainBadRequest() {
+        AnnotatedRequestEntity body = new AnnotatedRequestEntity("user", "12345");
+
+        ResponseSpec response = client.post()
+            .uri(ANNOTATIONS_EP_URL)
+            .body(Mono.just(body), AnnotatedRequestEntity.class)
+            .exchange();
+
+        response.expectStatus()
+            .isOk();
+    }
+}
diff --git a/spring-boot-h2/spring-boot-h2-database/src/main/java/com/baeldung/h2db/auto/configuration/AutoConfigurationDemo.java b/spring-boot-h2/spring-boot-h2-database/src/main/java/com/baeldung/h2db/auto/configuration/AutoConfigurationDemo.java
index 87a191554b..8d92e18754 100644
--- a/spring-boot-h2/spring-boot-h2-database/src/main/java/com/baeldung/h2db/auto/configuration/AutoConfigurationDemo.java
+++ b/spring-boot-h2/spring-boot-h2-database/src/main/java/com/baeldung/h2db/auto/configuration/AutoConfigurationDemo.java
@@ -4,7 +4,7 @@ import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.annotation.ComponentScan;
 
-@SpringBootApplication(scanBasePackages = "com.baeldung.h2db.auto-configuration")
+@SpringBootApplication
 public class AutoConfigurationDemo {
 
     public static void main(String[] args) {
diff --git a/core-java/src/main/java/com/baeldung/throwsexception/Calculator.java b/testing-modules/junit-5/src/main/java/com/baeldung/throwsexception/Calculator.java
similarity index 100%
rename from core-java/src/main/java/com/baeldung/throwsexception/Calculator.java
rename to testing-modules/junit-5/src/main/java/com/baeldung/throwsexception/Calculator.java
diff --git a/core-java/src/main/java/com/baeldung/throwsexception/DivideByZeroException.java b/testing-modules/junit-5/src/main/java/com/baeldung/throwsexception/DivideByZeroException.java
similarity index 100%
rename from core-java/src/main/java/com/baeldung/throwsexception/DivideByZeroException.java
rename to testing-modules/junit-5/src/main/java/com/baeldung/throwsexception/DivideByZeroException.java
diff --git a/core-java/src/test/java/com/baeldung/junit4vstestng/SortedUnitTest.java b/testing-modules/junit-5/src/test/java/com/baeldung/junit4vstestng/SortedUnitTest.java
similarity index 100%
rename from core-java/src/test/java/com/baeldung/junit4vstestng/SortedUnitTest.java
rename to testing-modules/junit-5/src/test/java/com/baeldung/junit4vstestng/SortedUnitTest.java
diff --git a/core-java/src/test/java/com/baeldung/junit4vstestng/SummationServiceIntegrationTest.java b/testing-modules/junit-5/src/test/java/com/baeldung/junit4vstestng/SummationServiceIntegrationTest.java
similarity index 100%
rename from core-java/src/test/java/com/baeldung/junit4vstestng/SummationServiceIntegrationTest.java
rename to testing-modules/junit-5/src/test/java/com/baeldung/junit4vstestng/SummationServiceIntegrationTest.java
diff --git a/testing-modules/junit-5/src/test/java/com/baeldung/junit5vstestng/SummationServiceIntegrationTest.java b/testing-modules/junit-5/src/test/java/com/baeldung/junit5vstestng/SummationServiceIntegrationTest.java
new file mode 100644
index 0000000000..92e7a6f5db
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/com/baeldung/junit5vstestng/SummationServiceIntegrationTest.java
@@ -0,0 +1,53 @@
+package com.baeldung.junit5vstestng;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class SummationServiceIntegrationTest {
+    private static List<Integer> numbers;
+
+    @BeforeAll
+    public static void initialize() {
+        numbers = new ArrayList<>();
+    }
+ 
+    @AfterAll
+    public static void tearDown() {
+        numbers = null;
+    }
+ 
+    @BeforeEach
+    public void runBeforeEachTest() {
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+    }
+ 
+    @AfterEach
+    public void runAfterEachTest() {
+        numbers.clear();
+    }
+ 
+    @Test
+    public void givenNumbers_sumEquals_thenCorrect() {
+        int sum = numbers.stream()
+            .reduce(0, Integer::sum);
+        Assert.assertEquals(6, sum);
+    }
+
+    @Ignore
+    @Test
+    public void givenEmptyList_sumEqualsZero_thenCorrect() {
+        int sum = numbers.stream()
+            .reduce(0, Integer::sum);
+        Assert.assertEquals(6, sum);
+    }
+}
diff --git a/core-java/src/test/java/com/baeldung/throwsexception/CalculatorUnitTest.java b/testing-modules/junit-5/src/test/java/com/baeldung/throwsexception/CalculatorUnitTest.java
similarity index 100%
rename from core-java/src/test/java/com/baeldung/throwsexception/CalculatorUnitTest.java
rename to testing-modules/junit-5/src/test/java/com/baeldung/throwsexception/CalculatorUnitTest.java
diff --git a/testing-modules/junit-5/src/test/java/org/baeldung/java/customtestname/CustomNameUnitTest.java b/testing-modules/junit-5/src/test/java/org/baeldung/java/customtestname/CustomNameUnitTest.java
new file mode 100644
index 0000000000..f04b825c89
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/org/baeldung/java/customtestname/CustomNameUnitTest.java
@@ -0,0 +1,17 @@
+package org.baeldung.java.customtestname;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class CustomNameUnitTest {
+
+    @ParameterizedTest
+    @ValueSource(strings = { "Hello", "World" })
+    @DisplayName("Test Method to check that the inputs are not nullable")
+    void givenString_TestNullOrNot(String word) {
+        assertNotNull(word);
+    }
+}
diff --git a/testing-modules/junit-5/src/test/java/org/baeldung/java/parameterisedsource/ParameterizedUnitTest.java b/testing-modules/junit-5/src/test/java/org/baeldung/java/parameterisedsource/ParameterizedUnitTest.java
new file mode 100644
index 0000000000..8d09161176
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/org/baeldung/java/parameterisedsource/ParameterizedUnitTest.java
@@ -0,0 +1,45 @@
+package org.baeldung.java.parameterisedsource;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.EnumSet;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.EnumSource;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class ParameterizedUnitTest {
+
+    @ParameterizedTest
+    @ValueSource(strings = { "Hello", "World" })
+    void givenString_TestNullOrNot(String word) {
+        assertNotNull(word);
+    }
+    
+    @ParameterizedTest
+    @EnumSource(value = PizzaDeliveryStrategy.class, names = {"EXPRESS", "NORMAL"})
+    void givenEnum_TestContainsOrNot(PizzaDeliveryStrategy timeUnit) {
+        assertTrue(EnumSet.of(PizzaDeliveryStrategy.EXPRESS, PizzaDeliveryStrategy.NORMAL).contains(timeUnit));
+    }
+    
+    @ParameterizedTest
+    @MethodSource("wordDataProvider")
+    void givenMethodSource_TestInputStream(String argument) {
+        assertNotNull(argument);
+    }
+
+    static Stream<String> wordDataProvider() {
+        return Stream.of("foo", "bar");
+    }
+    
+    @ParameterizedTest
+    @CsvSource({ "1, Car", "2, House", "3, Train" })
+    void givenCSVSource_TestContent(int id, String word) {
+        assertNotNull(id);
+        assertNotNull(word);
+    }
+}
diff --git a/testing-modules/junit-5/src/test/java/org/baeldung/java/parameterisedsource/PizzaDeliveryStrategy.java b/testing-modules/junit-5/src/test/java/org/baeldung/java/parameterisedsource/PizzaDeliveryStrategy.java
new file mode 100644
index 0000000000..ecfc7b4627
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/org/baeldung/java/parameterisedsource/PizzaDeliveryStrategy.java
@@ -0,0 +1,6 @@
+package org.baeldung.java.parameterisedsource;
+
+public enum PizzaDeliveryStrategy {
+    EXPRESS,
+    NORMAL;
+}
diff --git a/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/SelectClassesSuiteUnitTest.java b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/SelectClassesSuiteUnitTest.java
new file mode 100644
index 0000000000..220897eae7
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/SelectClassesSuiteUnitTest.java
@@ -0,0 +1,13 @@
+package org.baeldung.java.suite;
+
+import org.baeldung.java.suite.childpackage1.Class1UnitTest;
+import org.baeldung.java.suite.childpackage2.Class2UnitTest;
+import org.junit.platform.runner.JUnitPlatform;
+import org.junit.platform.suite.api.SelectClasses;
+import org.junit.runner.RunWith;
+
+@RunWith(JUnitPlatform.class)
+@SelectClasses({Class1UnitTest.class, Class2UnitTest.class})
+public class SelectClassesSuiteUnitTest {
+
+}
diff --git a/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/SelectPackagesSuiteUnitTest.java b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/SelectPackagesSuiteUnitTest.java
new file mode 100644
index 0000000000..ae887ae43b
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/SelectPackagesSuiteUnitTest.java
@@ -0,0 +1,11 @@
+package org.baeldung.java.suite;
+
+import org.junit.platform.runner.JUnitPlatform;
+import org.junit.platform.suite.api.SelectPackages;
+import org.junit.runner.RunWith;
+
+@RunWith(JUnitPlatform.class)
+@SelectPackages({ "org.baeldung.java.suite.childpackage1", "org.baeldung.java.suite.childpackage2" })
+public class SelectPackagesSuiteUnitTest {
+
+}
diff --git a/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/childpackage1/Class1UnitTest.java b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/childpackage1/Class1UnitTest.java
new file mode 100644
index 0000000000..78469cb971
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/childpackage1/Class1UnitTest.java
@@ -0,0 +1,15 @@
+package org.baeldung.java.suite.childpackage1;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.Test;
+
+
+public class Class1UnitTest {
+
+    @Test
+    public void testCase_InClass1UnitTest() {
+        assertTrue(true);
+    }
+    
+}
diff --git a/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/childpackage2/Class2UnitTest.java b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/childpackage2/Class2UnitTest.java
new file mode 100644
index 0000000000..4463ecfad9
--- /dev/null
+++ b/testing-modules/junit-5/src/test/java/org/baeldung/java/suite/childpackage2/Class2UnitTest.java
@@ -0,0 +1,14 @@
+package org.baeldung.java.suite.childpackage2;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.Test;
+
+public class Class2UnitTest {
+
+    @Test
+    public void testCase_InClass2UnitTest() {
+        assertTrue(true);
+    }
+    
+}