Merge branch 'master' of https://github.com/eugenp/tutorials

algorithms-searching/README.md

@@ -3,6 +3,7 @@
 This module contains articles about searching algorithms.
 
 ### Relevant articles:
+
 - [Binary Search Algorithm in Java](https://www.baeldung.com/java-binary-search)
 - [Depth First Search in Java](https://www.baeldung.com/java-depth-first-search)
 - [Interpolation Search in Java](https://www.baeldung.com/java-interpolation-search)
@@ -11,4 +12,4 @@ This module contains articles about searching algorithms.
 - [Monte Carlo Tree Search for Tic-Tac-Toe Game](https://www.baeldung.com/java-monte-carlo-tree-search)
 - [Range Search Algorithm in Java](https://www.baeldung.com/java-range-search)
 - [Fast Pattern Matching of Strings Using Suffix Tree](https://www.baeldung.com/java-pattern-matching-suffix-tree)
-- [Topological Sort of Directed Acyclic Graph](https://www.baeldung.com/cs/dag-topological-sort)
+- [Find the Kth Smallest Element in Two Sorted Arrays](https://www.baeldung.com/java-kth-smallest-element-in-sorted-arrays)

algorithms-searching/src/main/java/com/baeldung/algorithms/kthsmallest/KthSmallest.java

@@ -0,0 +1,126 @@
+package com.baeldung.algorithms.kthsmallest;
+
+import java.util.Arrays;
+import java.util.NoSuchElementException;
+
+import static java.lang.Math.max;
+import static java.lang.Math.min;
+
+public class KthSmallest {
+
+    public static int findKthSmallestElement(int k, int[] list1, int[] list2)  throws NoSuchElementException, IllegalArgumentException {
+
+        checkInput(k, list1, list2);
+
+        // we are looking for the minimum value
+        if(k == 1) {
+            return min(list1[0], list2[0]);
+        }
+
+        // we are looking for the maximum value
+        if(list1.length + list2.length == k) {
+            return max(list1[list1.length-1], list2[list2.length-1]);
+        }
+
+        // swap lists if needed to make sure we take at least one element from list1
+        if(k <= list2.length && list2[k-1] < list1[0]) {
+            int[] list1_ = list1;
+            list1 = list2;
+            list2 = list1_;
+        }
+
+        // correct left boundary if k is bigger than the size of list2
+        int left = k < list2.length ? 0 : k - list2.length - 1;
+
+        // the inital right boundary cannot exceed the list1
+        int right = min(k-1, list1.length - 1);
+
+        int nElementsList1, nElementsList2;
+
+        // binary search
+        do {
+            nElementsList1 = ((left + right) / 2) + 1;
+            nElementsList2 = k - nElementsList1;
+
+            if(nElementsList2 > 0) {
+                if (list1[nElementsList1 - 1] > list2[nElementsList2 - 1]) {
+                    right = nElementsList1 - 2;
+                } else {
+                    left = nElementsList1;
+                }
+            }
+        } while(!kthSmallesElementFound(list1, list2, nElementsList1, nElementsList2));
+
+        return nElementsList2 == 0 ? list1[nElementsList1-1] : max(list1[nElementsList1-1], list2[nElementsList2-1]);
+    }
+
+    private static boolean kthSmallesElementFound(int[] list1, int[] list2, int nElementsList1, int nElementsList2) {
+
+        // we do not take any element from the second list
+        if(nElementsList2 < 1) {
+            return true;
+        }
+
+        if(list1[nElementsList1-1] == list2[nElementsList2-1]) {
+            return true;
+        }
+
+        if(nElementsList1 == list1.length) {
+            return list1[nElementsList1-1] <= list2[nElementsList2];
+        }
+
+        if(nElementsList2 == list2.length) {
+            return list2[nElementsList2-1] <= list1[nElementsList1];
+        }
+
+        return list1[nElementsList1-1] <= list2[nElementsList2] && list2[nElementsList2-1] <= list1[nElementsList1];
+    }
+
+
+    private static void checkInput(int k, int[] list1, int[] list2) throws NoSuchElementException, IllegalArgumentException {
+
+        if(list1 == null || list2 == null || k < 1) {
+            throw new IllegalArgumentException();
+        }
+
+        if(list1.length == 0 || list2.length == 0) {
+            throw new IllegalArgumentException();
+        }
+
+        if(k > list1.length + list2.length) {
+            throw new NoSuchElementException();
+        }
+    }
+
+    public static int getKthElementSorted(int[] list1, int[] list2, int k) {
+
+        int length1 = list1.length, length2 = list2.length;
+        int[] combinedArray = new int[length1 + length2];
+        System.arraycopy(list1, 0, combinedArray, 0, list1.length);
+        System.arraycopy(list2, 0, combinedArray, list1.length, list2.length);
+        Arrays.sort(combinedArray);
+
+        return combinedArray[k-1];
+    }
+
+    public static int getKthElementMerge(int[] list1, int[] list2, int k) {
+
+        int i1 = 0, i2 = 0;
+
+        while(i1 < list1.length && i2 < list2.length && (i1 + i2) < k) {
+            if(list1[i1] < list2[i2]) {
+                i1++;
+            } else {
+                i2++;
+            }
+        }
+
+        if((i1 + i2) < k) {
+            return i1 < list1.length ? list1[k - i2 - 1] : list2[k - i1 - 1];
+        } else if(i1 > 0 && i2 > 0) {
+            return Math.max(list1[i1-1], list2[i2-1]);
+        } else {
+            return i1 == 0 ? list2[i2-1] : list1[i1-1];
+        }
+    }
+}

algorithms-searching/src/test/java/com/baeldung/algorithms/kthsmallest/KthSmallestUnitTest.java

@@ -0,0 +1,288 @@
+package com.baeldung.algorithms.kthsmallest;
+
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.Executable;
+
+import java.util.*;
+
+import static com.baeldung.algorithms.kthsmallest.KthSmallest.*;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class KthSmallestUnitTest {
+
+    @Nested
+    class Exceptions {
+
+        @Test
+        public void when_at_least_one_list_is_null_then_an_exception_is_thrown() {
+
+            Executable executable1 = () -> findKthSmallestElement(1, null, null);
+            Executable executable2 = () -> findKthSmallestElement(1, new int[]{2}, null);
+            Executable executable3 = () -> findKthSmallestElement(1, null, new int[]{2});
+
+            assertThrows(IllegalArgumentException.class, executable1);
+            assertThrows(IllegalArgumentException.class, executable2);
+            assertThrows(IllegalArgumentException.class, executable3);
+        }
+
+        @Test
+        public void when_at_least_one_list_is_empty_then_an_exception_is_thrown() {
+
+            Executable executable1 = () -> findKthSmallestElement(1, new int[]{}, new int[]{2});
+            Executable executable2 = () -> findKthSmallestElement(1, new int[]{2}, new int[]{});
+            Executable executable3 = () -> findKthSmallestElement(1, new int[]{}, new int[]{});
+
+            assertThrows(IllegalArgumentException.class, executable1);
+            assertThrows(IllegalArgumentException.class, executable2);
+            assertThrows(IllegalArgumentException.class, executable3);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_0_then_an_exception_is_thrown() {
+            Executable executable1 = () -> findKthSmallestElement(-1, new int[]{2}, new int[]{2});
+            assertThrows(IllegalArgumentException.class, executable1);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_1_then_an_exception_is_thrown() {
+            Executable executable1 = () -> findKthSmallestElement(0, new int[]{2}, new int[]{2});
+            assertThrows(IllegalArgumentException.class, executable1);
+        }
+
+        @Test
+        public void when_k_bigger_then_the_two_lists_then_an_exception_is_thrown() {
+            Executable executable1 = () -> findKthSmallestElement(6, new int[]{1, 5, 6}, new int[]{2, 5});
+            assertThrows(NoSuchElementException.class, executable1);
+        }
+
+    }
+
+    @Nested
+    class K_is_smaller_than_the_size_of_list1_and_the_size_of_list2 {
+
+        @Test
+        public void when_k_is_1_then_the_smallest_element_is_returned_from_list1() {
+            int result = findKthSmallestElement(1, new int[]{2, 7}, new int[]{3, 5});
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void when_k_is_1_then_the_smallest_element_is_returned_list2() {
+            int result = findKthSmallestElement(1, new int[]{3, 5}, new int[]{2, 7});
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void when_kth_element_is_smallest_element_and_occurs_in_both_lists() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(1, list1, list2);
+            assertEquals(1, result);
+        }
+
+        @Test
+        public void when_kth_element_is_smallest_element_and_occurs_in_both_lists2() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(2, list1, list2);
+            assertEquals(1, result);
+        }
+
+        @Test
+        public void when_kth_element_is_largest_element_and_occurs_in_both_lists_1() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_kth_element_is_largest_element_and_occurs_in_both_lists_2() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(6, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_kth_element_and_occurs_in_both_lists() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{0, 2, 3};
+            int result = findKthSmallestElement(3, list1, list2);
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void and_kth_element_is_in_first_list() {
+            int[] list1 = new int[]{1,2,3,4};
+            int[] list2 = new int[]{1,3,4,5};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void and_kth_is_in_second_list() {
+            int[] list1 = new int[]{1,3,4,4};
+            int[] list2 = new int[]{1,2,4,5};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void and_elements_in_first_list_are_all_smaller_than_second_list() {
+            int[] list1 = new int[]{1,3,7,9};
+            int[] list2 = new int[]{11,12,14,15};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(7, result);
+        }
+
+        @Test
+        public void and_elements_in_first_list_are_all_smaller_than_second_list2() {
+            int[] list1 = new int[]{1,3,7,9};
+            int[] list2 = new int[]{11,12,14,15};
+            int result = findKthSmallestElement(4,  list1, list2);
+            assertEquals(9, result);
+        }
+
+        @Test
+        public void and_only_elements_from_second_list_are_part_of_result() {
+            int[] list1 = new int[]{11,12,14,15};
+            int[] list2 = new int[]{1,3,7,9};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(7, result);
+        }
+
+        @Test
+        public void and_only_elements_from_second_list_are_part_of_result2() {
+            int[] list1 = new int[]{11,12,14,15};
+            int[] list2 = new int[]{1,3,7,9};
+            int result = findKthSmallestElement(4,  list1, list2);
+            assertEquals(9, result);
+        }
+    }
+
+    @Nested
+    class K_is_bigger_than_the_size_of_at_least_one_of_the_lists {
+
+        @Test
+        public void k_is_smaller_than_list1_and_bigger_than_list2() {
+            int[] list1 = new int[]{1, 2, 3, 4, 7, 9};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void k_is_bigger_than_list1_and_smaller_than_list2() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3, 4, 7, 9};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists_and_elements_in_second_list_are_all_smaller_than_first_list() {
+            int[] list1 = new int[]{9, 11, 13, 55};
+            int[] list2 = new int[]{1, 2, 3, 7};
+            int result = findKthSmallestElement(6, list1, list2);
+            assertEquals(11, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists_and_elements_in_second_list_are_all_bigger_than_first_list() {
+            int[] list1 = new int[]{1, 2, 3, 7};
+            int[] list2 = new int[]{9, 11, 13, 55};
+            int result = findKthSmallestElement(6, list1, list2);
+            assertEquals(11, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists() {
+            int[] list1 = new int[]{3, 7, 9, 11, 55};
+            int[] list2 = new int[]{1, 2, 3, 7, 13};
+            int result = findKthSmallestElement(7, list1, list2);
+            assertEquals(9, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists_and_list1_has_more_elements_than_list2() {
+            int[] list1 = new int[]{3, 7, 9, 11, 55, 77, 100, 200};
+            int[] list2 = new int[]{1, 2, 3, 7, 13};
+            int result = findKthSmallestElement(11, list1, list2);
+            assertEquals(77, result);
+        }
+
+        @Test
+        public void max_test() {
+            int[] list1 = new int[]{100, 200};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(4, list1, list2);
+            assertEquals(100, result);
+        }
+
+        @Test
+        public void max_test2() {
+            int[] list1 = new int[]{100, 200};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(200, result);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_in_list2() {
+            int[] list1 = new int[]{1, 2, 5};
+            int[] list2 = new int[]{1, 3, 4, 7};
+            int result = findKthSmallestElement(4, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_is_smallest_in_list2() {
+            int[] list1 = new int[]{1, 2, 5};
+            int[] list2 = new int[]{3, 4, 7};
+            int result = findKthSmallestElement(3, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_is_smallest_in_list23() {
+            int[] list1 = new int[]{3, 11, 27, 53, 90};
+            int[] list2 = new int[]{4, 20, 21, 100};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(21, result);
+        }
+    }
+
+//    @Test
+//    public void randomTests() {
+//        IntStream.range(1, 100000).forEach(i -> random());
+//    }
+
+    private void random() {
+
+        Random random = new Random();
+        int length1 = (Math.abs(random.nextInt())) % 1000 + 1;
+        int length2 = (Math.abs(random.nextInt())) % 1000 + 1;
+
+        int[] list1 = sortedRandomIntArrayOfLength(length1);
+        int[] list2 = sortedRandomIntArrayOfLength(length2);
+
+        int k = (Math.abs(random.nextInt()) % (length1 + length2)) + 1 ;
+
+        int result = findKthSmallestElement(k,  list1, list2);
+
+        int result2 = getKthElementSorted(list1, list2, k);
+
+        int result3 = getKthElementMerge(list1, list2, k);
+
+        assertEquals(result2, result);
+        assertEquals(result2, result3);
+    }
+
+    private int[] sortedRandomIntArrayOfLength(int length) {
+        int[] intArray = new Random().ints(length).toArray();
+        Arrays.sort(intArray);
+        return intArray;
+    }
+}

apache-poi/README.md

@@ -3,9 +3,11 @@
 This module contains articles about Apache POI
 
 ### Relevant Articles:
+
 - [Microsoft Word Processing in Java with Apache POI](https://www.baeldung.com/java-microsoft-word-with-apache-poi)
 - [Working with Microsoft Excel in Java](https://www.baeldung.com/java-microsoft-excel)
 - [Creating a MS PowerPoint Presentation in Java](https://www.baeldung.com/apache-poi-slideshow)
 - [Merge Cells in Excel Using Apache POI](https://www.baeldung.com/java-apache-poi-merge-cells)
 - [Get String Value of Excel Cell with Apache POI](https://www.baeldung.com/java-apache-poi-cell-string-value)
 - [Read Excel Cell Value Rather Than Formula With Apache POI](https://www.baeldung.com/apache-poi-read-cell-value-formula)
+- [Setting Formulas in Excel with Apache POI](https://www.baeldung.com/java-apache-poi-set-formulas)

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

@@ -9,3 +9,4 @@ This module contains articles about Java 10 core features
 - [Copy a List to Another List in Java](http://www.baeldung.com/java-copy-list-to-another)
 - [Deep Dive Into the New Java JIT Compiler – Graal](https://www.baeldung.com/graal-java-jit-compiler)
 - [Copying Sets in Java](https://www.baeldung.com/java-copy-sets)
+- [Converting between a List and a Set in Java](https://www.baeldung.com/convert-list-to-set-and-set-to-list)

core-java-modules/core-java-10/pom.xml

@@ -1,22 +1,29 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project
-    xmlns="http://maven.apache.org/POM/4.0.0"
+        xmlns="http://maven.apache.org/POM/4.0.0"
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        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">
+        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-10</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-10</name>
     <packaging>jar</packaging>
-    <url>http://maven.apache.org</url>
 
     <parent>
-        <groupId>com.baeldung</groupId>
+        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>parent-modules</artifactId>
+        <artifactId>core-java-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
+        <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../../</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+    </dependencies>
+
     <build>
         <plugins>
             <plugin>
@@ -34,6 +41,7 @@
     <properties>
         <maven.compiler.source.version>10</maven.compiler.source.version>
         <maven.compiler.target.version>10</maven.compiler.target.version>
+        <commons-collections4.version>4.1</commons-collections4.version>
     </properties>
 
 </project>

core-java-modules/core-java-10/src/test/java/com/baeldung/java10/collections/conversion/ListSetConversionUnitTest.java

@@ -0,0 +1,68 @@
+package com.baeldung.java10.collections.conversion;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+import org.apache.commons.collections4.CollectionUtils;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+public class ListSetConversionUnitTest {
+
+    // Set -> List; List -> Set
+
+    @Test
+    public final void givenUsingCoreJava_whenSetConvertedToList_thenCorrect() {
+        final Set<Integer> sourceSet = Sets.newHashSet(0, 1, 2, 3, 4, 5);
+        final List<Integer> targetList = new ArrayList<>(sourceSet);
+    }
+
+    @Test
+    public final void givenUsingCoreJava_whenListConvertedToSet_thenCorrect() {
+        final List<Integer> sourceList = Lists.newArrayList(0, 1, 2, 3, 4, 5);
+        final Set<Integer> targetSet = new HashSet<>(sourceList);
+    }
+
+    @Test
+    public void givenUsingJava10_whenSetConvertedToList_thenCorrect() {
+        final Set<Integer> sourceSet = Sets.newHashSet(0, 1, 2, 3, 4, 5);
+        final List<Integer> targetList = List.copyOf(sourceSet);
+    }
+
+    @Test
+    public void givenUsingJava10_whenListConvertedToSet_thenCorrect() {
+        final List<Integer> sourceList = Lists.newArrayList(0, 1, 2, 3, 4, 5);
+        final Set<Integer> targetSet = Set.copyOf(sourceList);
+    }
+
+    @Test
+    public final void givenUsingGuava_whenSetConvertedToList_thenCorrect() {
+        final Set<Integer> sourceSet = Sets.newHashSet(0, 1, 2, 3, 4, 5);
+        final List<Integer> targetList = Lists.newArrayList(sourceSet);
+    }
+
+    @Test
+    public final void givenUsingGuava_whenListConvertedToSet_thenCorrect() {
+        final List<Integer> sourceList = Lists.newArrayList(0, 1, 2, 3, 4, 5);
+        final Set<Integer> targetSet = Sets.newHashSet(sourceList);
+    }
+
+    @Test
+    public final void givenUsingCommonsCollections_whenListConvertedToSet_thenCorrect() {
+        final List<Integer> sourceList = Lists.newArrayList(0, 1, 2, 3, 4, 5);
+
+        final Set<Integer> targetSet = new HashSet<>(6);
+        CollectionUtils.addAll(targetSet, sourceList);
+    }
+
+    @Test
+    public final void givenUsingCommonsCollections_whenSetConvertedToList_thenCorrect() {
+        final Set<Integer> sourceSet = Sets.newHashSet(0, 1, 2, 3, 4, 5);
+
+        final List<Integer> targetList = new ArrayList<>(6);
+        CollectionUtils.addAll(targetList, sourceSet);
+    }
+}

core-java-modules/core-java-8-datetime/src/test/java/com/baeldung/datetime/UseDateTimeFormatterUnitTest.java

@@ -31,6 +31,6 @@ public class UseDateTimeFormatterUnitTest {
     public void givenALocalDate_whenFormattingWithStyleAndLocale_thenPass() {
         String result = subject.formatWithStyleAndLocale(localDateTime, FormatStyle.MEDIUM, Locale.UK);
 
-        assertThat(result).isEqualTo("25 Jan 2015, 06:30:00");
+        assertThat(result).isEqualTo("25-Jan-2015 06:30:00");
     }
 }

core-java-modules/core-java-8-datetime/src/test/java/com/baeldung/datetime/UseToInstantUnitTest.java

@@ -3,6 +3,7 @@ package com.baeldung.datetime;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import java.time.LocalDateTime;
+import java.time.ZoneId;
 import java.util.Calendar;
 import java.util.Date;
 import java.util.GregorianCalendar;
@@ -24,10 +25,11 @@ public class UseToInstantUnitTest {
 
     @Test
     public void givenADate_whenConvertingToLocalDate_thenAsExpected() {
-        Date givenDate = new Date(1465817690000L);
+        LocalDateTime currentDateTime = LocalDateTime.now();
+        Date givenDate = Date.from(currentDateTime.atZone(ZoneId.systemDefault()).toInstant());
 
         LocalDateTime localDateTime = subject.convertDateToLocalDate(givenDate);
 
-        assertThat(localDateTime).isEqualTo("2016-06-13T13:34:50");
+        assertThat(localDateTime).isEqualTo(currentDateTime);
     }
 }

core-java-modules/core-java-8-datetime/src/test/java/com/baeldung/datetime/UseZonedDateTimeUnitTest.java

@@ -54,7 +54,7 @@ public class UseZonedDateTimeUnitTest {
     @Test
     public void givenAStringWithTimeZone_whenParsing_thenEqualsExpected() {
         ZonedDateTime resultFromString = zonedDateTime.getZonedDateTimeUsingParseMethod("2015-05-03T10:15:30+01:00[Europe/Paris]");
-        ZonedDateTime resultFromLocalDateTime = ZonedDateTime.of(2015, 5, 3, 11, 15, 30, 0, ZoneId.of("Europe/Paris"));
+        ZonedDateTime resultFromLocalDateTime = ZonedDateTime.of(2015, 5, 3, 10, 15, 30, 0, ZoneId.of("Europe/Paris"));
 
         assertThat(resultFromString.getZone()).isEqualTo(ZoneId.of("Europe/Paris"));
         assertThat(resultFromLocalDateTime.getZone()).isEqualTo(ZoneId.of("Europe/Paris"));

core-java-modules/core-java-arrays-operations-advanced/README.md

@@ -3,7 +3,9 @@
 This module contains articles about advanced operations on arrays in Java. They assume some background knowledge with arrays in Java.
 
 ### Relevant Articles: 
+
 - [How to Copy an Array in Java](https://www.baeldung.com/java-array-copy)
 - [Arrays.deepEquals](https://www.baeldung.com/java-arrays-deepequals)
 - [Find Sum and Average in a Java Array](https://www.baeldung.com/java-array-sum-average)
 - [Intersection Between two Integer Arrays](https://www.baeldung.com/java-array-intersection)
+- [Comparing Arrays in Java](https://www.baeldung.com/java-comparing-arrays)

core-java-modules/core-java-collections-2/src/test/java/com/baeldung/collections/sorting/JavaSortingUnitTest.java

@@ -5,7 +5,16 @@ import org.apache.commons.lang3.ArrayUtils;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 
 import static org.junit.Assert.assertTrue;
@@ -138,7 +147,7 @@ public class JavaSortingUnitTest {
         HashSet<Integer> descSortedIntegersSet = new LinkedHashSet<>(Arrays.asList(255, 200, 123, 89, 88, 66, 7, 5, 1));
 
         ArrayList<Integer> list = new ArrayList<>(integersSet);
-        list.sort((i1, i2) -> i2 - i1);
+        list.sort(Comparator.reverseOrder());
         integersSet = new LinkedHashSet<>(list);
 
         assertTrue(Arrays.equals(integersSet.toArray(), descSortedIntegersSet.toArray()));

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

@@ -12,3 +12,4 @@
 - [Fail-Safe Iterator vs Fail-Fast Iterator](https://www.baeldung.com/java-fail-safe-vs-fail-fast-iterator)
 - [Quick Guide to the Java Stack](https://www.baeldung.com/java-stack)
 - [Convert an Array of Primitives to a List](https://www.baeldung.com/java-primitive-array-to-list)
+- [A Guide to BitSet in Java](https://www.baeldung.com/java-bitset)

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

@@ -10,4 +10,5 @@ This module contains articles about the Java List collection
 - [Performance Comparison of Primitive Lists in Java](https://www.baeldung.com/java-list-primitive-performance)
 - [Filtering a Java Collection by a List](https://www.baeldung.com/java-filter-collection-by-list)
 - [How to Count Duplicate Elements in Arraylist](https://www.baeldung.com/java-count-duplicate-elements-arraylist)
+- [Finding the Differences Between Two Lists in Java](https://www.baeldung.com/java-lists-difference)
 - [[<-- Prev]](/core-java-modules/core-java-collections-list-2)

core-java-modules/core-java-collections-maps-2/pom.xml

@@ -21,20 +21,15 @@
             <version>${eclipse-collections.version}</version>
         </dependency>
         <dependency>
-            <groupId>net.sf.trove4j</groupId>
+            <groupId>com.carrotsearch</groupId>
-            <artifactId>trove4j</artifactId>
+            <artifactId>hppc</artifactId>
-            <version>${trove4j.version}</version>
+            <version>${hppc.version}</version>
         </dependency>
         <dependency>
             <groupId>it.unimi.dsi</groupId>
             <artifactId>fastutil</artifactId>
             <version>${fastutil.version}</version>
         </dependency>
-        <dependency>
-            <groupId>colt</groupId>
-            <artifactId>colt</artifactId>
-            <version>${colt.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
@@ -69,9 +64,8 @@
         <commons-collections4.version>4.1</commons-collections4.version>
         <avaitility.version>1.7.0</avaitility.version>
         <eclipse-collections.version>8.2.0</eclipse-collections.version>
-        <trove4j.version>3.0.2</trove4j.version>
+        <hppc.version>0.7.2</hppc.version>
         <fastutil.version>8.1.0</fastutil.version>
-        <colt.version>1.2.0</colt.version>
         <assertj.version>3.11.1</assertj.version>
     </properties>
 

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

@@ -1,29 +1,68 @@
 package com.baeldung.map.primitives;
 
-import cern.colt.map.AbstractIntDoubleMap;
+import com.carrotsearch.hppc.IntLongHashMap;
-import cern.colt.map.OpenIntDoubleHashMap;
+import com.carrotsearch.hppc.IntLongScatterMap;
-import gnu.trove.map.TDoubleIntMap;
+import com.carrotsearch.hppc.IntObjectHashMap;
-import gnu.trove.map.hash.TDoubleIntHashMap;
+import com.carrotsearch.hppc.IntObjectMap;
+import com.carrotsearch.hppc.IntObjectScatterMap;
+
 import it.unimi.dsi.fastutil.ints.Int2BooleanMap;
+import it.unimi.dsi.fastutil.ints.Int2BooleanMaps;
 import it.unimi.dsi.fastutil.ints.Int2BooleanOpenHashMap;
 import it.unimi.dsi.fastutil.ints.Int2BooleanSortedMap;
 import it.unimi.dsi.fastutil.ints.Int2BooleanSortedMaps;
+import it.unimi.dsi.fastutil.objects.ObjectIterator;
+
 import org.eclipse.collections.api.map.primitive.ImmutableIntIntMap;
 import org.eclipse.collections.api.map.primitive.MutableIntIntMap;
 import org.eclipse.collections.api.map.primitive.MutableObjectDoubleMap;
 import org.eclipse.collections.impl.factory.primitive.IntIntMaps;
 import org.eclipse.collections.impl.factory.primitive.ObjectDoubleMaps;
 
+import static java.lang.String.format;
+
+import java.math.BigDecimal;
+
 public class PrimitiveMaps {
 
     public static void main(String[] args) {
 
+        hppcMap();
         eclipseCollectionsMap();
-        troveMap();
-        coltMap();
         fastutilMap();
     }
 
+    private static void hppcMap() {
+        //Regular maps
+        IntLongHashMap intLongHashMap = new IntLongHashMap();
+        intLongHashMap.put(25,1L);
+        intLongHashMap.put(150,Long.MAX_VALUE);
+        intLongHashMap.put(1,0L);
+        
+        intLongHashMap.get(150);
+
+        IntObjectMap<BigDecimal> intObjectMap = new IntObjectHashMap<BigDecimal>();
+        intObjectMap.put(1, BigDecimal.valueOf(1));
+        intObjectMap.put(2, BigDecimal.valueOf(2500));
+
+        BigDecimal value = intObjectMap.get(2);
+
+        //Scatter maps
+        IntLongScatterMap intLongScatterMap = new IntLongScatterMap();
+        intLongScatterMap.put(1, 1L);
+        intLongScatterMap.put(2, -2L);
+        intLongScatterMap.put(1000,0L);    
+
+        intLongScatterMap.get(1000);
+
+        IntObjectScatterMap<BigDecimal> intObjectScatterMap = new IntObjectScatterMap<BigDecimal>();
+        intObjectScatterMap.put(1, BigDecimal.valueOf(1));
+        intObjectScatterMap.put(2, BigDecimal.valueOf(2500));
+
+        value = intObjectScatterMap.get(2);
+    }
+
+
     private static void fastutilMap() {
         Int2BooleanMap int2BooleanMap = new Int2BooleanOpenHashMap();
         int2BooleanMap.put(1, true);
@@ -32,13 +71,19 @@ public class PrimitiveMaps {
 
         boolean value = int2BooleanMap.get(1);
 
-        Int2BooleanSortedMap int2BooleanSorted = Int2BooleanSortedMaps.EMPTY_MAP;
+        //Lambda style iteration
-    }
+        Int2BooleanMaps.fastForEach(int2BooleanMap, entry -> {
+            System.out.println(String.format("Key: %d, Value: %b",entry.getIntKey(),entry.getBooleanValue()));
+        });
+
+        //Iterator based loop
+        ObjectIterator<Int2BooleanMap.Entry> iterator = Int2BooleanMaps.fastIterator(int2BooleanMap);
+        while(iterator.hasNext()) {
+            Int2BooleanMap.Entry entry = iterator.next();
+            System.out.println(String.format("Key: %d, Value: %b",entry.getIntKey(),entry.getBooleanValue()));
+
+        }
 
-    private static void coltMap() {
-        AbstractIntDoubleMap map = new OpenIntDoubleHashMap();
-        map.put(1, 4.5);
-        double value = map.get(1);
     }
 
     private static void eclipseCollectionsMap() {
@@ -53,17 +98,5 @@ public class PrimitiveMaps {
         dObject.addToValue("stability", 0.8);
     }
 
-    private static void troveMap() {
-        double[] doubles = new double[] {1.2, 4.5, 0.3};
-        int[] ints = new int[] {1, 4, 0};
 
-        TDoubleIntMap doubleIntMap = new TDoubleIntHashMap(doubles, ints);
-
-        doubleIntMap.put(1.2, 22);
-        doubleIntMap.put(4.5, 16);
-
-        doubleIntMap.adjustValue(1.2, 1);
-        doubleIntMap.adjustValue(4.5, 4);
-        doubleIntMap.adjustValue(0.3, 7);
-    }
 }

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

@@ -1,5 +1,8 @@
 #Core Java Console
 
-[Read and Write User Input in Java](http://www.baeldung.com/java-console-input-output)
+### Relevant Articles:
-[Formatting with printf() in Java](https://www.baeldung.com/java-printstream-printf)
+
-[ASCII Art in Java](http://www.baeldung.com/ascii-art-in-java)
+- [Read and Write User Input in Java](http://www.baeldung.com/java-console-input-output)
+- [Formatting with printf() in Java](https://www.baeldung.com/java-printstream-printf)
+- [ASCII Art in Java](http://www.baeldung.com/ascii-art-in-java)
+- [System.console() vs. System.out](https://www.baeldung.com/java-system-console-vs-system-out)

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

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [NoSuchMethodError in Java](https://www.baeldung.com/java-nosuchmethod-error)

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

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project
+    xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung.exceptions</groupId>
+    <artifactId>core-java-exceptions-3</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-exceptions-3</name>
+    <packaging>jar</packaging>
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <dependencies>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <!-- testing -->
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+
+</project>

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/nosuchmethoderror/MainMenu.java

@@ -0,0 +1,11 @@
+package com.baeldung.exceptions.nosuchmethoderror;
+
+public class MainMenu {
+    public static void main(String[] args) {
+        System.out.println("Today's Specials: " + getSpecials());
+    }
+
+    public static String getSpecials() {
+        return SpecialToday.getDesert();
+    }
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/exceptions/nosuchmethoderror/SpecialToday.java

@@ -0,0 +1,8 @@
+package com.baeldung.exceptions.nosuchmethoderror;
+public class SpecialToday {
+    private static String desert = "Chocolate Cake";
+
+    public static String getDesert() {
+        return desert;
+    }
+}

core-java-modules/core-java-exceptions-3/src/test/java/com/baeldung/exceptions/nosuchmethoderror/MainMenuUnitTest.java

@@ -0,0 +1,13 @@
+package com.baeldung.exceptions.nosuchmethoderror;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.jupiter.api.Test;
+
+class MainMenuUnitTest {
+
+    @Test
+    void whenGetSpecials_thenNotNull() {
+        assertNotNull(MainMenu.getSpecials());
+    }
+}

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

@@ -6,4 +6,7 @@ This module contains articles about core Java input and output (IO)
 
 - [Java – Create a File](https://www.baeldung.com/java-how-to-create-a-file)
 - [Check If a Directory Is Empty in Java](https://www.baeldung.com/java-check-empty-directory)
+- [Check If a File or Directory Exists in Java](https://www.baeldung.com/java-file-directory-exists)
+- [Copy a Directory in Java](https://www.baeldung.com/java-copy-directory)
+- [Java Files Open Options](https://www.baeldung.com/java-file-options)
 - [[<-- Prev]](/core-java-modules/core-java-io-2)

core-java-modules/core-java-io-3/src/test/java/com/baeldung/linenumber/LineAtGivenNumberUnitTest.java

@@ -0,0 +1,82 @@
+package com.baeldung.linenumber;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.IOUtils;
+import org.junit.Test;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.Scanner;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+
+public class LineAtGivenNumberUnitTest {
+
+    private static final String FILE_PATH = "src/test/resources/linesInput.txt";
+
+    @Test
+    public void givenFile_whenUsingBufferedReader_thenExtractedLineIsCorrect() throws IOException {
+        try (BufferedReader br = Files.newBufferedReader(Paths.get(FILE_PATH))) {
+            for (int i = 0; i < 3; i++) {
+                br.readLine();
+            }
+
+            String extractedLine = br.readLine();
+            assertEquals("Line 4", extractedLine);
+        }
+    }
+
+    @Test
+    public void givenFile_whenUsingScanner_thenExtractedLineIsCorrect() throws IOException {
+        try (Scanner scanner = new Scanner(new File(FILE_PATH))) {
+            for (int i = 0; i < 3; i++) {
+                scanner.nextLine();
+            }
+
+            String extractedLine = scanner.nextLine();
+            assertEquals("Line 4", extractedLine);
+        }
+    }
+
+    @Test
+    public void givenSmallFile_whenUsingFilesAPI_thenExtractedLineIsCorrect() throws IOException {
+        String extractedLine = Files.readAllLines(Paths.get(FILE_PATH)).get(4);
+
+        assertEquals("Line 5", extractedLine);
+    }
+
+    @Test
+    public void givenLargeFile_whenUsingFilesAPI_thenExtractedLineIsCorrect() throws IOException {
+        try (Stream<String> lines = Files.lines(Paths.get(FILE_PATH))) {
+            String extractedLine = lines.skip(4).findFirst().get();
+
+            assertEquals("Line 5", extractedLine);
+        }
+    }
+
+    @Test
+    public void givenFile_whenUsingFileUtils_thenExtractedLineIsCorrect() throws IOException {
+        ClassLoader classLoader = getClass().getClassLoader();
+        File file = new File(classLoader.getResource("linesInput.txt").getFile());
+
+        List<String> lines = FileUtils.readLines(file, "UTF-8");
+
+        String extractedLine = lines.get(0);
+        assertEquals("Line 1", extractedLine);
+    }
+
+    @Test
+    public void givenFile_whenUsingIOUtils_thenExtractedLineIsCorrect() throws IOException {
+        String fileContent = IOUtils.toString(new FileInputStream(FILE_PATH), StandardCharsets.UTF_8);
+
+        String extractedLine = fileContent.split(System.lineSeparator())[0];
+        assertEquals("Line 1", extractedLine);
+    }
+}

core-java-modules/core-java-io-3/src/test/resources/linesInput.txt

@@ -0,0 +1,5 @@
+Line 1
+Line 2
+Line 3
+Line 4
+Line 5

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

@@ -10,4 +10,5 @@ This module contains articles about working with the Java Virtual Machine (JVM).
 - [boolean and boolean[] Memory Layout in the JVM](https://www.baeldung.com/jvm-boolean-memory-layout)
 - [Where Is the Array Length Stored in JVM?](https://www.baeldung.com/java-jvm-array-length)
 - [Memory Address of Objects in Java](https://www.baeldung.com/java-object-memory-address)
+- [List All Classes Loaded in a Specific Class Loader](https://www.baeldung.com/java-list-classes-class-loader)
 - More articles: [[<-- prev]](/core-java-modules/core-java-jvm)

core-java-modules/core-java-jvm-2/src/main/java/com/baeldung/loadedclasslisting/Launcher.java

@@ -0,0 +1,19 @@
+package com.baeldung.loadedclasslisting;
+
+import java.util.Arrays;
+
+public class Launcher {
+
+    public static void main(String[] args) {
+        printClassesLoadedBy("BOOTSTRAP");
+        printClassesLoadedBy("SYSTEM");
+        printClassesLoadedBy("EXTENSION");
+    }
+
+    private static void printClassesLoadedBy(String classLoaderType) {
+        System.out.println(classLoaderType + " ClassLoader : ");
+        Class<?>[] classes = ListLoadedClassesAgent.listLoadedClasses(classLoaderType);
+        Arrays.asList(classes)
+            .forEach(clazz -> System.out.println(clazz.getCanonicalName()));
+    }
+}

core-java-modules/core-java-jvm-2/src/main/java/com/baeldung/loadedclasslisting/ListLoadedClassesAgent.java

@@ -0,0 +1,40 @@
+package com.baeldung.loadedclasslisting;
+
+import java.lang.instrument.Instrumentation;
+
+public class ListLoadedClassesAgent {
+
+    private static Instrumentation instrumentation;
+
+    public static void premain(String agentArgs, Instrumentation instrumentation) {
+        ListLoadedClassesAgent.instrumentation = instrumentation;
+    }
+
+    public static Class<?>[] listLoadedClasses(String classLoaderType) {
+        if (instrumentation == null) {
+            throw new IllegalStateException(
+              "ListLoadedClassesAgent is not initialized.");
+        }
+        return instrumentation.getInitiatedClasses(
+          getClassLoader(classLoaderType));
+    }
+
+    private static ClassLoader getClassLoader(String classLoaderType) {
+        ClassLoader classLoader = null;
+        switch (classLoaderType) {
+        case "SYSTEM":
+            classLoader = ClassLoader.getSystemClassLoader();
+            break;
+        case "EXTENSION":
+            classLoader = ClassLoader.getSystemClassLoader().getParent();
+            break;
+        // passing a null value to the Instrumentation : getInitiatedClasses method
+        // defaults to the bootstrap class loader
+        case "BOOTSTRAP":
+            break;
+        default:
+            break;
+        }
+        return classLoader;
+    }
+}

core-java-modules/core-java-jvm-2/src/main/java/com/baeldung/loadedclasslisting/MANIFEST.MF

@@ -0,0 +1 @@
+Premain-Class: com.baeldung.loadedclasslisting.ListLoadedClassesAgent

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/java8/entity/Human.java

@@ -37,7 +37,7 @@ public class Human {
 
     public static int compareByNameThenAge(final Human lhs, final Human rhs) {
         if (lhs.name.equals(rhs.name)) {
-            return lhs.age - rhs.age;
+            return Integer.compare(lhs.age, rhs.age);
         } else {
             return lhs.name.compareTo(rhs.name);
         }

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/java8/lambda/tips/Bar.java

@@ -6,8 +6,11 @@ public interface Bar {
 
     String method(String string);
 
-    default String defaultMethod() {
+    default String defaultBar() {
-        return "String from Bar";
+        return "Default String from Bar";
     }
 
+    default String defaultCommon() {
+        return "Default Common from Bar";
+    }
 }

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/java8/lambda/tips/Baz.java

@@ -6,7 +6,11 @@ public interface Baz {
 
     String method(String string);
 
-    default String defaultMethod() {
+    default String defaultBaz() {
-        return "String from Baz";
+        return "Default String from Baz";
+    }
+
+    default String defaultCommon(){
+        return "Default Common from Baz";
     }
 }

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/java8/lambda/tips/FooExtended.java

@@ -5,8 +5,7 @@ package com.baeldung.java8.lambda.tips;
 public interface FooExtended extends Baz, Bar {
 
     @Override
-    default String defaultMethod() {
+    default String defaultCommon() {
-        return Bar.super.defaultMethod();
+        return Bar.super.defaultCommon();
     }
-
 }

core-java-modules/core-java-lambdas/src/test/java/com/baeldung/java8/Java8SortUnitTest.java

@@ -54,7 +54,7 @@ public class Java8SortUnitTest {
         final List<Human> humans = Lists.newArrayList(new Human("Sarah", 12), new Human("Sarah", 10), new Human("Zack", 12));
         humans.sort((lhs, rhs) -> {
             if (lhs.getName().equals(rhs.getName())) {
-                return lhs.getAge() - rhs.getAge();
+                return Integer.compare(lhs.getAge(), rhs.getAge());
             } else {
                 return lhs.getName().compareTo(rhs.getName());
             }

core-java-modules/core-java-lambdas/src/test/java/com/baeldung/java8/lambda/tips/Java8FunctionalInteracesLambdasUnitTest.java

@@ -39,9 +39,9 @@ public class Java8FunctionalInteracesLambdasUnitTest {
     @Test
     public void defaultMethodFromExtendedInterface_whenReturnDefiniteString_thenCorrect() {
         final FooExtended fooExtended = string -> string;
-        final String result = fooExtended.defaultMethod();
+        final String result = fooExtended.defaultCommon();
 
-        assertEquals("String from Bar", result);
+        assertEquals("Default Common from Bar", result);
     }
 
     @Test

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

@@ -4,4 +4,5 @@ This module contains articles about core features in the Java language
 
 - [Class.isInstance vs Class.isAssignableFrom](https://www.baeldung.com/java-isinstance-isassignablefrom)
 - [Converting a Java String Into a Boolean](https://www.baeldung.com/java-string-to-boolean)
+- [When are Static Variables Initialized in Java?](https://www.baeldung.com/java-static-variables-initialization)
 - [[<-- Prev]](/core-java-modules/core-java-lang-2)

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

@@ -3,6 +3,7 @@
 This module contains articles about types in Java
 
 ### Relevant Articles: 
+
 - [Java Classes and Objects](https://www.baeldung.com/java-classes-objects)
 - [Guide to the this Java Keyword](https://www.baeldung.com/java-this)
 - [Nested Classes in Java](https://www.baeldung.com/java-nested-classes)
@@ -10,3 +11,4 @@ This module contains articles about types in Java
 - [Iterating Over Enum Values in Java](https://www.baeldung.com/java-enum-iteration)
 - [Attaching Values to Java Enum](https://www.baeldung.com/java-enum-values)
 - [A Guide to Java Enums](https://www.baeldung.com/a-guide-to-java-enums)
+- [Determine if an Object is of Primitive Type](https://www.baeldung.com/java-object-primitive-type)

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparable/Player.java

@@ -45,7 +45,7 @@ public class Player implements Comparable<Player> {
 
     @Override
     public int compareTo(Player otherPlayer) {
-        return (this.getRanking() - otherPlayer.getRanking());
+        return Integer.compare(getRanking(), otherPlayer.getRanking());
     }
 
 }

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparator/PlayerAgeComparator.java

@@ -6,7 +6,7 @@ public class PlayerAgeComparator implements Comparator<Player> {
 
     @Override
     public int compare(Player firstPlayer, Player secondPlayer) {
-       return (firstPlayer.getAge() - secondPlayer.getAge());
+       return Integer.compare(firstPlayer.getAge(), secondPlayer.getAge());
     }
 
 }

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparator/PlayerRankingComparator.java

@@ -6,7 +6,7 @@ public class PlayerRankingComparator implements Comparator<Player> {
 
     @Override
     public int compare(Player firstPlayer, Player secondPlayer) {
-       return (firstPlayer.getRanking() - secondPlayer.getRanking());
+       return Integer.compare(firstPlayer.getRanking(), secondPlayer.getRanking());
     }
 
 }

core-java-modules/core-java-lang/src/test/java/com/baeldung/comparator/AvoidingSubtractionUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.comparator;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class AvoidingSubtractionUnitTest {
+
+    @Test
+    public void givenTwoPlayers_whenUsingSubtraction_thenOverflow() {
+        Comparator<Player> comparator = (p1, p2) -> p1.getRanking() - p2.getRanking();
+        Player player1 = new Player(59, "John", Integer.MAX_VALUE);
+        Player player2 = new Player(67, "Roger", -1);
+
+        List<Player> players = Arrays.asList(player1, player2);
+        players.sort(comparator);
+        System.out.println(players);
+
+        assertEquals("John", players.get(0).getName());
+        assertEquals("Roger", players.get(1).getName());
+    }
+}

core-java-modules/core-java-lang/src/test/java/com/baeldung/comparator/Java8ComparatorUnitTest.java

@@ -1,14 +1,14 @@
 package com.baeldung.comparator;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.Before;
+import org.junit.Test;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
-import org.junit.Before;
+import static org.junit.Assert.assertEquals;
-import org.junit.Test;
 
 public class Java8ComparatorUnitTest {
 
@@ -28,7 +28,7 @@ public class Java8ComparatorUnitTest {
     @Test
     public void whenComparing_UsingLambda_thenSorted() {
         System.out.println("************** Java 8 Comaparator **************");
-        Comparator<Player> byRanking = (Player player1, Player player2) -> player1.getRanking() - player2.getRanking();
+        Comparator<Player> byRanking = (Player player1, Player player2) -> Integer.compare(player1.getRanking(), player2.getRanking());
 
         System.out.println("Before Sorting : " + footballTeam);
         Collections.sort(footballTeam, byRanking);

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

@@ -12,5 +12,6 @@ This module contains articles about working with the operating system (OS) in Ja
 - [How to Print Screen in Java](http://www.baeldung.com/print-screen-in-java)
 - [Pattern Search with Grep in Java](http://www.baeldung.com/grep-in-java)
 - [How to Run a Shell Command in Java](http://www.baeldung.com/run-shell-command-in-java)
+- [Taking Screenshots Using Java](https://www.baeldung.com/java-taking-screenshots)
 
-This module uses Java 9, so make sure to have the JDK 9 installed to run it.
+This module uses Java 9, so make sure to have the JDK 9 installed to run it.

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

@@ -1,3 +1,4 @@
 ### Relevant Articles:
 
 - [Reading the Value of ‘private’ Fields from a Different Class in Java](https://www.baeldung.com/java-reflection-read-private-field-value)
+- [Set Field Value With Reflection](https://www.baeldung.com/java-set-private-field-value)

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

@@ -1,13 +1,13 @@
 ## Core Java Cookbooks and Examples
 
 ### Relevant Articles: 
-[Getting Started with Java Properties](http://www.baeldung.com/java-properties)
+- [Getting Started with Java Properties](http://www.baeldung.com/java-properties)
-[Java Money and the Currency API](http://www.baeldung.com/java-money-and-currency)
+- [Java Money and the Currency API](http://www.baeldung.com/java-money-and-currency)
-[Introduction to Java Serialization](http://www.baeldung.com/java-serialization)
+- [Introduction to Java Serialization](http://www.baeldung.com/java-serialization)
-[Guide to UUID in Java](http://www.baeldung.com/java-uuid)
+- [Guide to UUID in Java](http://www.baeldung.com/java-uuid)
-[Compiling Java *.class Files with javac](http://www.baeldung.com/javac)
+- [Compiling Java *.class Files with javac](http://www.baeldung.com/javac)
-[Introduction to Javadoc](http://www.baeldung.com/javadoc)
+- [Introduction to Javadoc](http://www.baeldung.com/javadoc)
-[Guide to the Externalizable Interface in Java](http://www.baeldung.com/java-externalizable)
+- [Guide to the Externalizable Interface in Java](http://www.baeldung.com/java-externalizable)
-[What is the serialVersionUID?](http://www.baeldung.com/java-serial-version-uid)
+- [What is the serialVersionUID?](http://www.baeldung.com/java-serial-version-uid)
-[A Guide to the ResourceBundle](http://www.baeldung.com/java-resourcebundle)
+- [A Guide to the ResourceBundle](http://www.baeldung.com/java-resourcebundle)
-[Merging java.util.Properties Objects](https://www.baeldung.com/java-merging-properties)
+- [Merging java.util.Properties Objects](https://www.baeldung.com/java-merging-properties)

core-java-modules/pom.xml

@@ -22,6 +22,7 @@
         <!-- <module>core-java-11</module> --> <!-- We haven't upgraded to java 11. Fixing in BAEL-10841 -->
         <!-- <module>core-java-12</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
         <!-- <module>core-java-13</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
+        <!-- <module>core-java-14</module> --> <!-- We haven't upgraded to java 14.-->
         <module>core-java-8</module>
         <module>core-java-8-2</module>
 
@@ -59,15 +60,20 @@
         <module>core-java-concurrency-basic</module>
         <module>core-java-concurrency-basic-2</module>
         <module>core-java-concurrency-collections</module>
+        <module>core-java-concurrency-collections-2</module>
+        <module>core-java-console</module>
 
+        <!--<module>core-java-8-datetime</module>--> <!-- unit test case failure -->
+        <module>core-java-8-datetime-2</module>
         <!-- <module>core-java-date-operations-1</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
         <module>core-java-date-operations-2</module>
         <!-- We haven't upgraded to java 9. -->
         <!-- <module>core-java-datetime-computations</module> <module>core-java-datetime-conversion</module> <module>core-java-datetime-java8</module> <module>core-java-datetime-string</module> -->
+        <module>core-java-8-datetime</module>
 
         <module>core-java-exceptions</module>
         <module>core-java-exceptions-2</module>
-
+        <module>core-java-exceptions-3</module>
         <module>core-java-function</module>
 
         <module>core-java-io</module>

core-kotlin-modules/core-kotlin/README.md

@@ -3,6 +3,7 @@
 This module contains articles about Kotlin core features.
 
 ### Relevant articles:
+
 - [Introduction to the Kotlin Language](https://www.baeldung.com/kotlin-intro)
 - [Kotlin Java Interoperability](https://www.baeldung.com/kotlin-java-interoperability)
 - [Get a Random Number in Kotlin](https://www.baeldung.com/kotlin-random-number)
@@ -10,3 +11,4 @@ This module contains articles about Kotlin core features.
 - [Kotlin Ternary Conditional Operator](https://www.baeldung.com/kotlin-ternary-operator)
 - [Sequences in Kotlin](https://www.baeldung.com/kotlin/sequences)
 - [Converting Kotlin Data Class from JSON using GSON](https://www.baeldung.com/kotlin-json-convert-data-class)
+- [Exception Handling in Kotlin](https://www.baeldung.com/kotlin/exception-handling)

deeplearning4j/README.md

@@ -5,3 +5,4 @@ This module contains articles about Deeplearning4j.
 ### Relevant Articles:
 - [A Guide to Deeplearning4j](https://www.baeldung.com/deeplearning4j)
 - [Logistic Regression in Java](https://www.baeldung.com/java-logistic-regression)
+- [How to Implement a CNN with Deeplearning4j](https://www.baeldung.com/java-cnn-deeplearning4j)

docker/README.md

@@ -1,3 +1,4 @@
 ## Relevant Articles:
 
 - [Introduction to Docker Compose](https://www.baeldung.com/docker-compose)
+- [Creating Docker Images with Spring Boot](https://www.baeldung.com/spring-boot-docker-images)

excelformula/README.md

@@ -1,5 +0,0 @@
-## Apache POI
-
-This module contains articles about Apache POI
-
-### Relevant Articles:

java-collections-conversions-2/README.md

@@ -3,6 +3,8 @@
 This module contains articles about conversions among Collection types and arrays in Java.
 
 ### Relevant Articles: 
+
 - [Array to String Conversions](https://www.baeldung.com/java-array-to-string)
 - [Mapping Lists with ModelMapper](https://www.baeldung.com/java-modelmapper-lists)
+- [Converting List to Map With a Custom Supplier](https://www.baeldung.com/list-to-map-supplier)
 - More articles: [[<-- prev]](../java-collections-conversions)

java-collections-conversions-2/src/test/java/com/baeldung/arrayconversion/ArrayToListConversionUnitTest.java

@@ -0,0 +1,32 @@
+package com.baeldung.arrayconversion;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class ArrayToListConversionUnitTest {
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void givenAnArray_whenConvertingToList_returnUnmodifiableListUnitTest() {
+        String[] stringArray = new String[] { "A", "B", "C", "D" };
+        List<String> stringList = Arrays.asList(stringArray);
+        System.out.println(stringList);
+        stringList.set(0, "E");
+        System.out.println(stringList);
+        System.out.println(Arrays.toString(stringArray));
+        stringList.add("F");
+    }
+
+    @Test
+    public void givenAnArray_whenConvertingToList_returnModifiableListUnitTest() {
+        String[] stringArray = new String[] { "A", "B", "C", "D" };
+        List<String> stringList = new ArrayList<>(Arrays.asList(stringArray));
+        System.out.println(stringList);
+        stringList.set(0, "E");
+        System.out.println(stringList);
+        System.out.println(Arrays.toString(stringArray));
+        stringList.add("F");
+    }
+}

java-collections-conversions/README.md

@@ -5,7 +5,6 @@ This module contains articles about conversions among Collection types and array
 ### Relevant Articles: 
 - [Converting between an Array and a List in Java](https://www.baeldung.com/convert-array-to-list-and-list-to-array)
 - [Converting between an Array and a Set in Java](https://www.baeldung.com/convert-array-to-set-and-set-to-array)
-- [Converting between a List and a Set in Java](https://www.baeldung.com/convert-list-to-set-and-set-to-list)
 - [Convert a Map to an Array, List or Set in Java](https://www.baeldung.com/convert-map-values-to-array-list-set)
 - [Converting a List to String in Java](https://www.baeldung.com/java-list-to-string)
 - [How to Convert List to Map in Java](https://www.baeldung.com/java-list-to-map)

java-collections-conversions/src/test/java/com/baeldung/java/collections/JavaCollectionConversionUnitTest.java

@@ -101,42 +101,6 @@ public class JavaCollectionConversionUnitTest {
         final int[] primitiveTargetArray = ArrayUtils.toPrimitive(targetArray);
     }
 
-    // Set -> List; List -> Set
-
-    public final void givenUsingCoreJava_whenSetConvertedToList_thenCorrect() {
-        final Set<Integer> sourceSet = Sets.newHashSet(0, 1, 2, 3, 4, 5);
-        final List<Integer> targetList = new ArrayList<>(sourceSet);
-    }
-
-    public final void givenUsingCoreJava_whenListConvertedToSet_thenCorrect() {
-        final List<Integer> sourceList = Lists.newArrayList(0, 1, 2, 3, 4, 5);
-        final Set<Integer> targetSet = new HashSet<>(sourceList);
-    }
-
-    public final void givenUsingGuava_whenSetConvertedToList_thenCorrect() {
-        final Set<Integer> sourceSet = Sets.newHashSet(0, 1, 2, 3, 4, 5);
-        final List<Integer> targetList = Lists.newArrayList(sourceSet);
-    }
-
-    public final void givenUsingGuava_whenListConvertedToSet_thenCorrect() {
-        final List<Integer> sourceList = Lists.newArrayList(0, 1, 2, 3, 4, 5);
-        final Set<Integer> targetSet = Sets.newHashSet(sourceList);
-    }
-
-    public final void givenUsingCommonsCollections_whenListConvertedToSet_thenCorrect() {
-        final List<Integer> sourceList = Lists.newArrayList(0, 1, 2, 3, 4, 5);
-
-        final Set<Integer> targetSet = new HashSet<>(6);
-        CollectionUtils.addAll(targetSet, sourceList);
-    }
-
-    public final void givenUsingCommonsCollections_whenSetConvertedToList_thenCorrect() {
-        final Set<Integer> sourceSet = Sets.newHashSet(0, 1, 2, 3, 4, 5);
-
-        final List<Integer> targetList = new ArrayList<>(6);
-        CollectionUtils.addAll(targetList, sourceSet);
-    }
-
     // Map (values) -> Array, List, Set
 
     @Test
@@ -144,7 +108,7 @@ public class JavaCollectionConversionUnitTest {
         final Map<Integer, String> sourceMap = createMap();
 
         final Collection<String> values = sourceMap.values();
-        final String[] targetArray = values.toArray(new String[values.size()]);
+        final String[] targetArray = values.toArray(new String[0]);
     }
 
     @Test

java-numbers-4/README.md

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

javax-servlets/README.md

@@ -12,4 +12,4 @@ This module contains articles about Servlets.
 - [Jakarta EE Servlet Exception Handling](https://www.baeldung.com/servlet-exceptions)
 - [Context and Servlet Initialization Parameters](https://www.baeldung.com/context-servlet-initialization-param)
 - [The Difference between getRequestURI and getPathInfo in HttpServletRequest](https://www.baeldung.com/http-servlet-request-requesturi-pathinfo)
-- Difference between request.getSession() and request.getSession(true)
+- [Difference between request.getSession() and request.getSession(true)](https://www.baeldung.com/java-request-getsession)

jgit/src/main/java/com/baeldung/jgit/porcelain/AddFile.java

@@ -6,6 +6,8 @@ import com.baeldung.jgit.helper.Helper;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.Repository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Simple snippet which shows how to add a file to the index
@@ -14,6 +16,8 @@ import org.eclipse.jgit.lib.Repository;
  */
 public class AddFile {
 
+    private static final Logger logger = LoggerFactory.getLogger(AddFile.class);
+
     public static void main(String[] args) throws IOException, GitAPIException {
         // prepare a new test-repository
         try (Repository repository = Helper.createNewRepository()) {
@@ -29,7 +33,7 @@ public class AddFile {
                         .addFilepattern("testfile")
                         .call();
 
-                System.out.println("Added file " + myfile + " to repository at " + repository.getDirectory());
+                logger.debug("Added file " + myfile + " to repository at " + repository.getDirectory());
             }
         }
     }

jgit/src/main/java/com/baeldung/jgit/porcelain/CommitAll.java

@@ -7,6 +7,8 @@ import com.baeldung.jgit.helper.Helper;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.Repository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Simple snippet which shows how to commit all files
@@ -15,6 +17,8 @@ import org.eclipse.jgit.lib.Repository;
  */
 public class CommitAll {
 
+    private static final Logger logger = LoggerFactory.getLogger(CommitAll.class);
+
     public static void main(String[] args) throws IOException, GitAPIException {
         // prepare a new test-repository
         try (Repository repository = Helper.createNewRepository()) {
@@ -44,7 +48,7 @@ public class CommitAll {
                         .call();
 
 
-                System.out.println("Committed all changes to repository at " + repository.getDirectory());
+                logger.debug("Committed all changes to repository at " + repository.getDirectory());
             }
         }
     }

jgit/src/main/java/com/baeldung/jgit/porcelain/CreateAndDeleteTag.java

@@ -9,6 +9,8 @@ import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Simple snippet which shows how to create a tag
@@ -17,6 +19,8 @@ import org.eclipse.jgit.revwalk.RevWalk;
  */
 public class CreateAndDeleteTag {
 
+    private static final Logger logger = LoggerFactory.getLogger(CreateAndDeleteTag.class);
+
     public static void main(String[] args) throws IOException, GitAPIException {
         // prepare test-repository
         try (Repository repository = Helper.openJGitRepository()) {
@@ -26,7 +30,7 @@ public class CreateAndDeleteTag {
 
                 // set it on the current HEAD
                 Ref tag = git.tag().setName("tag_for_testing").call();
-                System.out.println("Created/moved tag " + tag + " to repository at " + repository.getDirectory());
+                logger.debug("Created/moved tag " + tag + " to repository at " + repository.getDirectory());
 
                 // remove the tag again
                 git.tagDelete().setTags("tag_for_testing").call();
@@ -36,14 +40,14 @@ public class CreateAndDeleteTag {
                 try (RevWalk walk = new RevWalk(repository)) {
                     RevCommit commit = walk.parseCommit(id);
                     tag = git.tag().setObjectId(commit).setName("tag_for_testing").call();
-                    System.out.println("Created/moved tag " + tag + " to repository at " + repository.getDirectory());
+                    logger.debug("Created/moved tag " + tag + " to repository at " + repository.getDirectory());
 
                     // remove the tag again
                     git.tagDelete().setTags("tag_for_testing").call();
 
                     // create an annotated tag
                     tag = git.tag().setName("tag_for_testing").setAnnotated(true).call();
-                    System.out.println("Created/moved tag " + tag + " to repository at " + repository.getDirectory());
+                    logger.debug("Created/moved tag " + tag + " to repository at " + repository.getDirectory());
 
                     // remove the tag again
                     git.tagDelete().setTags("tag_for_testing").call();

jgit/src/main/java/com/baeldung/jgit/porcelain/Log.java

@@ -7,6 +7,9 @@ import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /**
  * Simple snippet which shows how to get the commit-ids for a file to provide log information.
  *
@@ -14,6 +17,8 @@ import org.eclipse.jgit.revwalk.RevCommit;
  */
 public class Log {
 
+    private static final Logger logger = LoggerFactory.getLogger(Log.class);
+
     @SuppressWarnings("unused")
     public static void main(String[] args) throws IOException, GitAPIException {
         try (Repository repository = Helper.openJGitRepository()) {
@@ -22,30 +27,30 @@ public class Log {
                         .call();
                 int count = 0;
                 for (RevCommit rev : logs) {
-                    //System.out.println("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
+                    logger.trace("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
                     count++;
                 }
-                System.out.println("Had " + count + " commits overall on current branch");
+                logger.debug("Had " + count + " commits overall on current branch");
 
                 logs = git.log()
                         .add(repository.resolve(git.getRepository().getFullBranch()))
                         .call();
                 count = 0;
                 for (RevCommit rev : logs) {
-                    System.out.println("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
+                    logger.trace("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
                     count++;
                 }
-                System.out.println("Had " + count + " commits overall on "+git.getRepository().getFullBranch());
+                logger.debug("Had " + count + " commits overall on "+git.getRepository().getFullBranch());
 
                 logs = git.log()
                         .all()
                         .call();
                 count = 0;
                 for (RevCommit rev : logs) {
-                    //System.out.println("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
+                    logger.trace("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
                     count++;
                 }
-                System.out.println("Had " + count + " commits overall in repository");
+                logger.debug("Had " + count + " commits overall in repository");
 
                 logs = git.log()
                         // for all log.all()
@@ -53,10 +58,10 @@ public class Log {
                         .call();
                 count = 0;
                 for (RevCommit rev : logs) {
-                    //System.out.println("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
+                    logger.trace("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
                     count++;
                 }
-                System.out.println("Had " + count + " commits on README.md");
+                logger.debug("Had " + count + " commits on README.md");
 
                 logs = git.log()
                         // for all log.all()
@@ -64,10 +69,10 @@ public class Log {
                         .call();
                 count = 0;
                 for (RevCommit rev : logs) {
-                    //System.out.println("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
+                    logger.trace("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
                     count++;
                 }
-                System.out.println("Had " + count + " commits on pom.xml");
+                logger.debug("Had " + count + " commits on pom.xml");
             }
         }
     }

jgit/src/test/java/com/baeldung/jgit/porcelain/PorcelainUnitTest.java

@@ -11,7 +11,8 @@ public class PorcelainUnitTest {
         CommitAll.main(null);
         
         CreateAndDeleteTag.main(null);
-         
+
-        Log.main(null);    
+        Log.main(null);
+
     }
 }

jmh/README.md

@@ -6,3 +6,4 @@ This module contains articles about the Java Microbenchmark Harness (JMH).
 
 - [Microbenchmarking with Java](https://www.baeldung.com/java-microbenchmark-harness)
 - [A Guide to False Sharing and @Contended](https://www.baeldung.com/java-false-sharing-contended)
+- [Performance Comparison of boolean[] vs BitSet](https://www.baeldung.com/java-boolean-array-bitset-performance)

json-2/README.md

@@ -3,5 +3,7 @@
 This module contains articles about JSON.
 
 ### Relevant Articles:
+
 - [Introduction to Jsoniter](https://www.baeldung.com/java-jsoniter)
 - [Introduction to Moshi Json](https://www.baeldung.com/java-json-moshi)
+- [Hypermedia Serialization With JSON-LD](https://www.baeldung.com/json-linked-data)

jsoup/README.md

@@ -5,6 +5,7 @@ This module contains articles about jsoup.
 ### Relevant Articles: 
 - [Parsing HTML in Java with Jsoup](https://www.baeldung.com/java-with-jsoup)
 - [How to add proxy support to Jsoup?](https://www.baeldung.com/java-jsoup-proxy)
+- [Preserving Line Breaks When Using Jsoup](https://www.baeldung.com/jsoup-line-breaks)
 
 ### Build the Project
 

libraries-5/pom.xml

@@ -32,12 +32,6 @@
             <artifactId>pact-jvm-consumer-junit_2.11</artifactId>
             <version>${pact.version}</version>
             <scope>test</scope>
-            <exclusions>
-                <exclusion>
-                    <groupId>org.codehaus.groovy</groupId>
-                    <artifactId>groovy-all</artifactId>
-                </exclusion>
-            </exclusions>
         </dependency>
 
         <!-- https://mvnrepository.com/artifact/com.typesafe.akka/akka-actor -->
@@ -53,10 +47,10 @@
             <scope>test</scope>
 
         </dependency>
-                <dependency>
+        <dependency>
-                    <groupId>one.util</groupId>
+            <groupId>one.util</groupId>
-                    <artifactId>streamex</artifactId>
+            <artifactId>streamex</artifactId>
-                    <version>${streamex.version}</version>
+            <version>${streamex.version}</version>
         </dependency>
         <dependency>
             <groupId>net.bytebuddy</groupId>

libraries-5/src/test/java/com/baeldung/pact/PactConsumerDrivenContractUnitTest.java

@@ -5,8 +5,6 @@ import au.com.dius.pact.consumer.PactProviderRuleMk2;
 import au.com.dius.pact.consumer.PactVerification;
 import au.com.dius.pact.consumer.dsl.PactDslWithProvider;
 import au.com.dius.pact.model.RequestResponsePact;
-
-import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.springframework.http.HttpEntity;
@@ -28,15 +26,30 @@ public class PactConsumerDrivenContractUnitTest {
 
     @Pact(consumer = "test_consumer")
     public RequestResponsePact createPact(PactDslWithProvider builder) {
-        Map<String, String> headers = new HashMap<String, String>();
+        Map<String, String> headers = new HashMap<>();
         headers.put("Content-Type", "application/json");
 
-        return builder.given("test GET").uponReceiving("GET REQUEST").path("/pact").method("GET").willRespondWith().status(200).headers(headers).body("{\"condition\": true, \"name\": \"tom\"}").given("test POST").uponReceiving("POST REQUEST").method("POST")
+        return builder
-                .headers(headers).body("{\"name\": \"Michael\"}").path("/pact").willRespondWith().status(201).toPact();
+          .given("test GET")
+            .uponReceiving("GET REQUEST")
+            .path("/pact")
+            .method("GET")
+          .willRespondWith()
+            .status(200)
+            .headers(headers)
+            .body("{\"condition\": true, \"name\": \"tom\"}")
+          .given("test POST")
+            .uponReceiving("POST REQUEST")
+            .method("POST")
+            .headers(headers)
+            .body("{\"name\": \"Michael\"}")
+            .path("/pact")
+          .willRespondWith()
+            .status(201)
+          .toPact();
     }
 
     @Test
-    @Ignore
     @PactVerification()
     public void givenGet_whenSendRequest_shouldReturn200WithProperHeaderAndBody() {
         // when

libraries-testing/src/test/resources/logback.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <logger name="org.dbunit" level="INFO" />
+</configuration>
+

maven-modules/maven-profiles/pom.xml

@@ -66,27 +66,29 @@
                 </file>
             </activation>
         </profile>
+        <profile>
+            <id>show-active-profiles</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-help-plugin</artifactId>
+                        <version>${help.plugin.version}</version>
+                        <executions>
+                            <execution>
+                                <id>show-profiles</id>
+                                <phase>compile</phase>
+                                <goals>
+                                    <goal>active-profiles</goal>
+                                </goals>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
     </profiles>
 
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-help-plugin</artifactId>
-                <version>${help.plugin.version}</version>
-                <executions>
-                    <execution>
-                        <id>show-profiles</id>
-                        <phase>compile</phase>
-                        <goals>
-                            <goal>active-profiles</goal>
-                        </goals>
-                    </execution>
-                </executions>
-            </plugin>
-        </plugins>
-    </build>
-
     <properties>
        <help.plugin.version>3.2.0</help.plugin.version>
     </properties>

maven-modules/optional-dependencies/README.md

@@ -1,3 +1,3 @@
 ### Relevant Articles:
 
-- Optional Dependency in Maven
+- [Optional Dependency in Maven](https://www.baeldung.com/maven-optional-dependency)

patterns/pom.xml

@@ -21,6 +21,7 @@
         <module>dip</module>
         <module>cqrs-es</module>
         <module>front-controller</module>
+        <module>hexagonal-architecture</module>
         <module>intercepting-filter</module>
         <module>solid</module>
     </modules>

patterns/solid/README.md

@@ -4,3 +4,4 @@
 - [Single Responsibility Principle in Java](https://www.baeldung.com/java-single-responsibility-principle)
 - [Open/Closed Principle in Java](https://www.baeldung.com/java-open-closed-principle)
 - [Interface Segregation Principle in Java](https://www.baeldung.com/java-interface-segregation)
+- [Liskov Substitution Principle in Java](https://www.baeldung.com/java-liskov-substitution-principle)

performance-tests/README.md

@@ -5,6 +5,7 @@ This module contains articles about performance testing.
 ### Relevant Articles: 
 
 - [Performance of Java Mapping Frameworks](https://www.baeldung.com/java-performance-mapping-frameworks)
+- [Performance Effects of Exceptions in Java](https://www.baeldung.com/java-exceptions-performance)
 
 ### Running
 

performance-tests/pom.xml

@@ -19,27 +19,14 @@
             <version>${orika.version}</version>
         </dependency>
         <dependency>
-            <groupId>net.sf.dozer</groupId>
+            <groupId>com.github.dozermapper</groupId>
-            <artifactId>dozer</artifactId>
+            <artifactId>dozer-core</artifactId>
             <version>${dozer.version}</version>
-        </dependency>
+        </dependency>       
-        <dependency>
-            <groupId>io.craftsman</groupId>
-            <artifactId>dozer-jdk8-support</artifactId>
-            <version>${dozer-jdk8-support.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.mapstruct</groupId>
-            <artifactId>mapstruct-jdk8</artifactId>
+            <artifactId>mapstruct</artifactId>
-            <version>${mapstruct-jdk8.version}</version>
+            <version>${mapstruct.version}</version>
-            <optional>true</optional>
-        </dependency>
-        <!-- https://mvnrepository.com/artifact/org.mapstruct/mapstruct-processor -->
-        <dependency>
-            <groupId>org.mapstruct</groupId>
-            <artifactId>mapstruct-processor</artifactId>
-            <version>${mapstruct-jdk8.version}</version>
-            <scope>provided</scope>
         </dependency>
 
         <dependency>
@@ -77,10 +64,15 @@
                     <source>${javac.target}</source>
                     <target>${javac.target}</target>
                     <annotationProcessorPaths>
+                        <path>
+                            <groupId>org.openjdk.jmh</groupId>
+                            <artifactId>jmh-generator-annprocess</artifactId>
+                            <version>${jmh.version}</version>
+                        </path>
                         <path>
                             <groupId>org.mapstruct</groupId>
                             <artifactId>mapstruct-processor</artifactId>
-                            <version>${mapstruct-processor.version}</version>
+                            <version>${mapstruct.version}</version>
                         </path>
                     </annotationProcessorPaths>
                 </configuration>
@@ -120,28 +112,16 @@
                     </execution>
                 </executions>
             </plugin>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-jar-plugin</artifactId>
-                <version>${maven-jar-plugin.version}</version>
-                <configuration>
-                    <archive>
-                        <manifest>
-                            <mainClass>com.baeldung.performancetests.MappingFrameworksPerformance</mainClass>
-                        </manifest>
-                    </archive>
-                </configuration>
-            </plugin>
         </plugins>
         <pluginManagement>
             <plugins>
                 <plugin>
                     <artifactId>maven-clean-plugin</artifactId>
-                    <version>2.5</version>
+                    <version>${clean.plugin.version}</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-deploy-plugin</artifactId>
-                    <version>2.8.1</version>
+                    <version>${deploy.plugin.version}</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-install-plugin</artifactId>
@@ -179,19 +159,13 @@
         <!--
             JMH version to use with this project.
           -->
-        <jmh.version>1.21</jmh.version>
+        <jmh.version>1.23</jmh.version>
-        <orika.version>1.5.2</orika.version>
+        <orika.version>1.5.4</orika.version>
-        <dozer.version>5.5.1</dozer.version>
+        <dozer.version>6.5.0</dozer.version>
-        <dozer-jdk8-support.version>1.0.2</dozer-jdk8-support.version>
+        <mapstruct.version>1.3.1.Final</mapstruct.version>
-        <mapstruct-jdk8.version>1.2.0.Final</mapstruct-jdk8.version>
+        <modelmapper.version>2.3.8</modelmapper.version>
-        <modelmapper.version>1.1.0</modelmapper.version>
+        <jmapper.version>1.6.1.CR2</jmapper.version>             
-        <jmapper.version>1.6.0.1</jmapper.version>
+        
-        <mapstruct-processor.version>1.2.0.Final</mapstruct-processor.version>
-        <jmh-core.version>1.21</jmh-core.version>
-        <jmh-generator.version>1.21</jmh-generator.version>
-        <maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>
-        <maven-jar-plugin.version>3.2.0</maven-jar-plugin.version>
-
         <!--
             Java source/target to use for compilation.
           -->
@@ -201,14 +175,16 @@
             Name of the benchmark Uber-JAR to generate.
           -->
         <uberjar.name>benchmarks</uberjar.name>
-        <compiler.plugin.version>3.1</compiler.plugin.version>
+        <clean.plugin.version>3.1.0</clean.plugin.version>
-        <shade.plugin.version>2.2</shade.plugin.version>
+        <deploy.plugin.version>3.0.0-M1</deploy.plugin.version>
-        <install.version>2.5.1</install.version>
+        <compiler.plugin.version>3.8.1</compiler.plugin.version>
-        <jar.plugin.version>2.4</jar.plugin.version>
+        <shade.plugin.version>3.2.4</shade.plugin.version>
-        <javadoc.plugin.version>2.9.1</javadoc.plugin.version>
+        <install.version>3.0.0-M1</install.version>
-        <resources.plugin.version>2.6</resources.plugin.version>
+        <jar.plugin.version>3.2.0</jar.plugin.version>
-        <site.plugin.version>3.3</site.plugin.version>
+        <javadoc.plugin.version>3.2.0</javadoc.plugin.version>
-        <source.plugin.version>2.2.1</source.plugin.version>
+        <resources.plugin.version>3.1.0</resources.plugin.version>
+        <site.plugin.version>3.9.1</site.plugin.version>
+        <source.plugin.version>3.2.1</source.plugin.version>
         <surefire.plugin.version>2.17</surefire.plugin.version>
     </properties>
 

performance-tests/src/main/java/com/baeldung/performancetests/dozer/DozerConverter.java

@@ -2,28 +2,28 @@ package com.baeldung.performancetests.dozer;
 
 import com.baeldung.performancetests.Converter;
 import com.baeldung.performancetests.model.destination.DestinationCode;
+import com.baeldung.performancetests.model.destination.Order;
 import com.baeldung.performancetests.model.source.SourceCode;
 import com.baeldung.performancetests.model.source.SourceOrder;
-import com.baeldung.performancetests.model.destination.Order;
+import com.github.dozermapper.core.DozerBeanMapperBuilder;
-import org.dozer.DozerBeanMapper;
+import com.github.dozermapper.core.Mapper;
-import org.dozer.Mapper;
 
-    public class DozerConverter implements Converter {
+public class DozerConverter implements Converter {
-        private final Mapper mapper;
+    private final Mapper mapper;
 
-        public DozerConverter() {
+    public DozerConverter() {
-            DozerBeanMapper mapper = new DozerBeanMapper();
+        this.mapper = DozerBeanMapperBuilder.create()
-            mapper.addMapping(DozerConverter.class.getResourceAsStream("/dozer-mapping.xml"));
+            .withMappingFiles("dozer-mapping.xml")
-            this.mapper = mapper;
+            .build();
-        }
-
-        @Override
-        public Order convert(SourceOrder sourceOrder) {
-            return mapper.map(sourceOrder,Order.class);
-        }
-
-        @Override
-        public DestinationCode convert(SourceCode sourceCode) {
-            return mapper.map(sourceCode, DestinationCode.class);
-        }
     }
+
+    @Override
+    public Order convert(SourceOrder sourceOrder) {
+        return mapper.map(sourceOrder, Order.class);
+    }
+
+    @Override
+    public DestinationCode convert(SourceCode sourceCode) {
+        return mapper.map(sourceCode, DestinationCode.class);
+    }
+}

performance-tests/src/main/resources/dozer-mapping.xml

@@ -1,8 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<mappings xmlns="http://dozer.sourceforge.net"
+<mappings xmlns="http://dozermapper.github.io/schema/bean-mapping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://dozermapper.github.io/schema/bean-mapping https://dozermapper.github.io/schema/bean-mapping.xsd">
-          xsi:schemaLocation="http://dozer.sourceforge.net
-          http://dozer.sourceforge.net/schema/beanmapping.xsd">
 
     <configuration>
         <stop-on-errors>true</stop-on-errors>

performance-tests/src/test/resources/dozer-mapping.xml

@@ -1,8 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<mappings xmlns="http://dozer.sourceforge.net"
+<mappings xmlns="http://dozermapper.github.io/schema/bean-mapping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://dozermapper.github.io/schema/bean-mapping https://dozermapper.github.io/schema/bean-mapping.xsd">
-          xsi:schemaLocation="http://dozer.sourceforge.net
-          http://dozer.sourceforge.net/schema/beanmapping.xsd">
 
     <configuration>
         <stop-on-errors>true</stop-on-errors>

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

@@ -13,3 +13,4 @@
 - [Returning the Generated Keys in JDBC](https://www.baeldung.com/jdbc-returning-generated-keys)
 - [Loading JDBC Drivers](https://www.baeldung.com/java-jdbc-loading-drivers)
 - [Difference Between Statement and PreparedStatement](https://www.baeldung.com/java-statement-preparedstatement)
+- [Extracting Database Metadata Using JDBC](https://www.baeldung.com/jdbc-database-metadata)

persistence-modules/flyway-repair/README.MD

@@ -1 +1,3 @@
 ### Relevant Articles:
+
+- [Flyway Repair With Spring Boot](https://www.baeldung.com/spring-boot-flyway-repair)

persistence-modules/hibernate5/README.md

@@ -13,3 +13,4 @@ This module contains articles about Hibernate 5. Let's not add more articles her
 - [Guide to the Hibernate EntityManager](https://www.baeldung.com/hibernate-entitymanager)
 - [Using c3p0 with Hibernate](https://www.baeldung.com/hibernate-c3p0)
 - [Persist a JSON Object Using Hibernate](https://www.baeldung.com/hibernate-persist-json-object)
+- [What Is the Hi/Lo Algorithm?](https://www.baeldung.com/hi-lo-algorithm-hibernate)

persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/hilo/RestaurantOrder.java

@@ -0,0 +1,34 @@
+package com.baeldung.hibernate.hilo;
+
+import org.hibernate.annotations.GenericGenerator;
+import org.hibernate.annotations.Parameter;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity
+public class RestaurantOrder {
+    @Id
+    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "hilo_sequence_generator")
+    @GenericGenerator(
+      name = "hilo_sequence_generator",
+      strategy = "sequence",
+      parameters = {
+        @Parameter(name = "sequence_name", value = "hilo_seqeunce"),
+        @Parameter(name = "initial_value", value = "1"),
+        @Parameter(name = "increment_size", value = "3"),
+        @Parameter(name = "optimizer", value = "hilo")
+      }
+    )
+    private Long id;
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+}

persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/hilo/HibernateHiloUnitTest.java

@@ -0,0 +1,99 @@
+package com.baeldung.hibernate.hilo;
+
+import org.apache.log4j.BasicConfigurator;
+import org.apache.log4j.Level;
+import org.apache.log4j.LogManager;
+import org.hibernate.HibernateException;
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.hibernate.Transaction;
+import org.hibernate.boot.Metadata;
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.SessionFactoryBuilder;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.service.ServiceRegistry;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.net.URL;
+import java.util.Properties;
+
+import static org.junit.Assert.fail;
+
+public class HibernateHiloUnitTest {
+    private Session session;
+
+    @Before
+    public void init() {
+        try {
+            configureLogger();
+
+            ServiceRegistry serviceRegistry = configureServiceRegistry();
+            SessionFactory factory = getSessionFactoryBuilder(serviceRegistry).build();
+            session = factory.openSession();
+        } catch (HibernateException | IOException e) {
+            fail("Failed to initiate Hibernate Session [Exception:" + e.toString() + "]");
+        }
+    }
+
+    private void configureLogger() {
+        BasicConfigurator.configure();
+        LogManager.getLogger("org.hibernate").setLevel(Level.ERROR);
+        LogManager.getLogger("org.hibernate.id.enhanced.SequenceStructure").setLevel(Level.DEBUG);
+        LogManager.getLogger("org.hibernate.event.internal.AbstractSaveEventListener").setLevel(Level.DEBUG);
+        LogManager.getLogger("org.hibernate.SQL").setLevel(Level.DEBUG);
+    }
+
+
+    private static SessionFactoryBuilder getSessionFactoryBuilder(ServiceRegistry serviceRegistry) {
+        MetadataSources metadataSources = new MetadataSources(serviceRegistry);
+        metadataSources.addAnnotatedClass(RestaurantOrder.class);
+        Metadata metadata = metadataSources.buildMetadata();
+
+        return metadata.getSessionFactoryBuilder();
+    }
+
+    private static ServiceRegistry configureServiceRegistry() throws IOException {
+        Properties properties = getProperties();
+
+        return new StandardServiceRegistryBuilder().applySettings(properties)
+          .build();
+    }
+
+    private static Properties getProperties() throws IOException {
+        Properties properties = new Properties();
+        URL propertiesURL = getPropertiesURL();
+
+        try (FileInputStream inputStream = new FileInputStream(propertiesURL.getFile())) {
+            properties.load(inputStream);
+        }
+
+        return properties;
+    }
+
+    private static URL getPropertiesURL() {
+        return Thread.currentThread()
+          .getContextClassLoader()
+          .getResource("hibernate-hilo.properties");
+    }
+
+    @Test
+    public void givenHiLoAlgorithm_when9EntitiesArePersisted_Then3callsToDBForNextValueShouldBeMade() {
+        Transaction transaction = session.beginTransaction();
+
+        for (int i = 0; i < 9; i++) {
+            session.persist(new RestaurantOrder());
+            session.flush();
+        }
+
+        transaction.commit();
+    }
+
+    @After
+    public void cleanup() {
+        session.close();
+    }
+}

persistence-modules/hibernate5/src/test/resources/hibernate-hilo.properties

@@ -0,0 +1,10 @@
+hibernate.connection.driver_class=org.h2.Driver
+hibernate.connection.url=jdbc:h2:mem:hilo_db;DB_CLOSE_DELAY=-1
+hibernate.connection.username=sa
+hibernate.dialect=org.hibernate.dialect.H2Dialect
+hibernate.show_sql=true
+hibernate.hbm2ddl.auto=create-drop
+hibernate.c3p0.min_size=5
+hibernate.c3p0.max_size=20
+hibernate.c3p0.acquire_increment=5
+hibernate.c3p0.timeout=1800

persistence-modules/java-jpa-3/README.md

@@ -1,3 +1,7 @@
 ## JPA in Java
 
 This module contains articles about the Java Persistence API (JPA) in Java.
+
+### Relevant Articles:
+
+- [JPA Entity Equality](https://www.baeldung.com/jpa-entity-equality)

persistence-modules/pom.xml

@@ -19,12 +19,14 @@
         <module>core-java-persistence</module>
         <module>deltaspike</module>
         <module>elasticsearch</module>
+        <module>flyway</module>
         <module>flyway-repair</module>
         <module>hbase</module>
         <module>hibernate5</module>
         <module>hibernate-mapping</module> <!-- long running -->
         <module>hibernate-ogm</module>
         <module>hibernate-annotations</module>
+        <module>hibernate-exceptions</module>
         <module>hibernate-libraries</module>
         <module>hibernate-jpa</module>
         <module>hibernate-queries</module>
@@ -53,6 +55,7 @@
         <module>spring-boot-persistence-mongodb</module>
         <module>spring-data-cassandra</module>
         <module>spring-data-cassandra-reactive</module>
+        <module>spring-data-cosmosdb</module>
         <module>spring-data-couchbase-2</module>
         <module>spring-data-dynamodb</module>
         <module>spring-data-eclipselink</module>
@@ -78,6 +81,7 @@
         <module>spring-hibernate-5</module> <!-- long running -->
         <module>spring-hibernate4</module>
         <module>spring-jpa</module>
+        <module>spring-jpa-2</module>
         <!-- <module>spring-mybatis</module> --> <!-- needs fixing in BAEL-9021 -->
         <module>spring-persistence-simple</module>
         <module>spring-persistence-simple-2</module>

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

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Introduction to Spring Data Azure Cosmos DB](https://www.baeldung.com/spring-data-cosmos-db)

persistence-modules/spring-data-cosmosdb/pom.xml

@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>spring-data-cosmosdb</artifactId>
+    <name>spring-data-cosmos-db</name>
+    <description>tutorial for spring-data-cosmosdb</description>
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+    
+    <properties>
+        <java.version>1.8</java.version>
+        <cosmodb.version>2.3.0</cosmodb.version>
+    </properties>
+    
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.microsoft.azure</groupId>
+            <artifactId>spring-data-cosmosdb</artifactId>
+            <version>${cosmodb.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+        </dependency>
+    </dependencies>
+    
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

persistence-modules/spring-data-cosmosdb/src/main/java/com/baeldung/spring/data/cosmosdb/AzureCosmosDbApplication.java

@@ -0,0 +1,12 @@
+package com.baeldung.spring.data.cosmosdb;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class AzureCosmosDbApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(AzureCosmosDbApplication.class, args);
+    }
+}

persistence-modules/spring-data-cosmosdb/src/main/java/com/baeldung/spring/data/cosmosdb/config/AzureCosmosDbConfiguration.java

@@ -0,0 +1,37 @@
+package com.baeldung.spring.data.cosmosdb.config;
+
+import com.azure.data.cosmos.CosmosKeyCredential;
+import com.microsoft.azure.spring.data.cosmosdb.config.AbstractCosmosConfiguration;
+import com.microsoft.azure.spring.data.cosmosdb.config.CosmosDBConfig;
+import com.microsoft.azure.spring.data.cosmosdb.repository.config.EnableCosmosRepositories;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@EnableCosmosRepositories(basePackages = "com.baeldung.spring.data.cosmosdb.repository")
+public class AzureCosmosDbConfiguration extends AbstractCosmosConfiguration {
+
+    @Value("${azure.cosmosdb.uri}")
+    private String uri;
+
+    @Value("${azure.cosmosdb.key}")
+    private String key;
+
+    @Value("${azure.cosmosdb.secondaryKey}")
+    private String secondaryKey;
+
+    @Value("${azure.cosmosdb.database}")
+    private String dbName;
+
+    private CosmosKeyCredential cosmosKeyCredential;
+
+    @Bean
+    public CosmosDBConfig getConfig() {
+        this.cosmosKeyCredential = new CosmosKeyCredential(key);
+        CosmosDBConfig cosmosdbConfig = CosmosDBConfig.builder(uri, this.cosmosKeyCredential, dbName)
+            .build();
+        return cosmosdbConfig;
+    }
+}

persistence-modules/spring-data-cosmosdb/src/main/java/com/baeldung/spring/data/cosmosdb/controller/ProductController.java

@@ -0,0 +1,53 @@
+package com.baeldung.spring.data.cosmosdb.controller;
+
+import com.baeldung.spring.data.cosmosdb.entity.Product;
+import com.baeldung.spring.data.cosmosdb.service.ProductService;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.DeleteMapping;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.ResponseStatus;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+import java.util.Optional;
+
+@RestController
+@RequestMapping("/products")
+public class ProductController {
+
+    private ProductService productService;
+
+    @Autowired
+    public ProductController(ProductService productService) {
+        this.productService = productService;
+    }
+
+    @PostMapping
+    @ResponseStatus(HttpStatus.CREATED)
+    public void create(@RequestBody Product product) {
+        productService.saveProduct(product);
+    }
+
+    @GetMapping(value = "/{id}/category/{category}")
+    public Optional<Product> get(@PathVariable String id, @PathVariable String category) {
+        return productService.findById(id, category);
+    }
+
+    @DeleteMapping(value = "/{id}/category/{category}")
+    public void delete(@PathVariable String id, @PathVariable String category) {
+        productService.delete(id, category);
+    }
+
+    @GetMapping
+    public List<Product> getByName(@RequestParam String name) {
+        return productService.findProductByName(name);
+    }
+
+}

persistence-modules/spring-data-cosmosdb/src/main/java/com/baeldung/spring/data/cosmosdb/entity/Product.java

@@ -0,0 +1,26 @@
+package com.baeldung.spring.data.cosmosdb.entity;
+
+import com.microsoft.azure.spring.data.cosmosdb.core.mapping.Document;
+import com.microsoft.azure.spring.data.cosmosdb.core.mapping.PartitionKey;
+
+import org.springframework.data.annotation.Id;
+
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@Document(collection = "products")
+public class Product {
+
+    @Id
+    private String productid;
+
+    private String productName;
+
+    private double price;
+
+    @PartitionKey
+    private String productCategory;
+
+}

persistence-modules/spring-data-cosmosdb/src/main/java/com/baeldung/spring/data/cosmosdb/repository/ProductRepository.java

@@ -0,0 +1,14 @@
+package com.baeldung.spring.data.cosmosdb.repository;
+
+import com.baeldung.spring.data.cosmosdb.entity.Product;
+import com.microsoft.azure.spring.data.cosmosdb.repository.CosmosRepository;
+
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+
+@Repository
+public interface ProductRepository extends CosmosRepository<Product, String> {
+    List<Product> findByProductName(String productName);
+
+}

persistence-modules/spring-data-cosmosdb/src/main/java/com/baeldung/spring/data/cosmosdb/service/ProductService.java

@@ -0,0 +1,38 @@
+package com.baeldung.spring.data.cosmosdb.service;
+
+import com.azure.data.cosmos.PartitionKey;
+import com.baeldung.spring.data.cosmosdb.entity.Product;
+import com.baeldung.spring.data.cosmosdb.repository.ProductRepository;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+import java.util.List;
+import java.util.Optional;
+
+@Component
+public class ProductService {
+
+    private ProductRepository repository;
+
+    @Autowired
+    public ProductService(ProductRepository repository) {
+        this.repository = repository;
+    }
+
+    public List<Product> findProductByName(String productName) {
+        return repository.findByProductName(productName);
+    }
+
+    public Optional<Product> findById(String productId, String category) {
+        return repository.findById(productId, new PartitionKey(category));
+    }
+
+    public void saveProduct(Product product) {
+        repository.save(product);
+    }
+
+    public void delete(String productId, String category) {
+        repository.deleteById(productId, new PartitionKey(category));
+    }
+}

persistence-modules/spring-data-cosmosdb/src/main/resources/application.properties

@@ -0,0 +1,4 @@
+azure.cosmosdb.uri=cosmodb-uri
+azure.cosmosdb.key=cosmodb-primary-key
+azure.cosmosdb.secondaryKey=cosmodb-second-key
+azure.cosmosdb.database=cosmodb-name

persistence-modules/spring-data-cosmosdb/src/test/java/com/baeldung/spring/data/cosmosdb/AzureCosmosDbApplicationManualTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.spring.data.cosmosdb;
+
+import com.azure.data.cosmos.PartitionKey;
+import com.baeldung.spring.data.cosmosdb.entity.Product;
+import com.baeldung.spring.data.cosmosdb.repository.ProductRepository;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.util.Assert;
+
+@SpringBootTest
+public class AzureCosmosDbApplicationManualTest {
+
+    @Autowired
+    ProductRepository productRepository;
+
+    @Test
+    public void givenProductIsCreated_whenCallFindById_thenProductIsFound() {
+        Product product = new Product();
+        product.setProductid("1001");
+        product.setProductCategory("Shirt");
+        product.setPrice(110.0);
+        product.setProductName("Blue Shirt");
+
+        productRepository.save(product);
+        Product retrievedProduct = productRepository.findById("1001", new PartitionKey("Shirt"))
+            .orElse(null);
+        Assert.notNull(retrievedProduct, "Retrieved Product is Null");
+
+    }
+
+}

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

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Introduction to Spring Data JDBC](https://www.baeldung.com/spring-data-jdbc-intro)

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

@@ -0,0 +1,16 @@
+## Spring Data JPA - Query
+
+This module contains articles about querying data using Spring Data JPA 
+
+### Relevant Articles: 
+- [Use Criteria Queries in a Spring Data Application](https://www.baeldung.com/spring-data-criteria-queries)
+- More articles: [[<-- prev]](../spring-data-jpa-query)
+
+### Eclipse Config 
+After importing the project into Eclipse, you may see the following error:  
+"No persistence xml file found in project"
+
+This can be ignored: 
+- Project -> Properties -> Java Persistance -> JPA -> Error/Warnings -> Select Ignore on "No persistence xml file found in project"
+Or: 
+- Eclipse -> Preferences - Validation - disable the "Build" execution of the JPA Validator 

persistence-modules/spring-data-jpa-query-2/pom.xml

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>spring-data-jpa-query</artifactId>
+    <name>spring-data-jpa-query-2</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+    </dependencies>
+
+</project>

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/dao/BookRepositoryCustom.java

@@ -1,9 +1,9 @@
 package com.baeldung.persistence.dao;
 
-import java.util.List;
-
 import com.baeldung.persistence.model.Book;
 
+import java.util.List;
+
 public interface BookRepositoryCustom {
 
     List<Book> findBooksByAuthorNameAndTitle(String authorName, String title);

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/dao/BookRepositoryImpl.java

@@ -1,7 +1,7 @@
 package com.baeldung.persistence.dao;
 
-import java.util.ArrayList;
+import com.baeldung.persistence.model.Book;
-import java.util.List;
+import org.springframework.stereotype.Repository;
 
 import javax.persistence.EntityManager;
 import javax.persistence.TypedQuery;
@@ -9,9 +9,8 @@ import javax.persistence.criteria.CriteriaBuilder;
 import javax.persistence.criteria.CriteriaQuery;
 import javax.persistence.criteria.Predicate;
 import javax.persistence.criteria.Root;
-
+import java.util.ArrayList;
-import com.baeldung.persistence.model.Book;
+import java.util.List;
-import org.springframework.stereotype.Repository;
 
 @Repository
 public class BookRepositoryImpl implements BookRepositoryCustom {