Merge pull request #3 from eugenp/master

update

.gitignore

@@ -85,7 +85,6 @@ transaction.log
 *-shell.log
 
 apache-cxf/cxf-aegis/baeldung.xml
-apache-fop/src/test/resources/input.xml
-apache-fop/src/test/resources/output_herold.pdf
-apache-fop/src/test/resources/output_html2fo.pdf
-apache-fop/src/test/resources/output_jtidy.pdf
+testing-modules/report-*.json
+
+libraries-2/*.db

algorithms-miscellaneous-2/src/test/java/com/baeldung/jgrapht/GraphImageGenerationUnitTest.java

@@ -1,16 +1,21 @@
 package com.baeldung.jgrapht;
 
 import static org.junit.Assert.assertTrue;
+
 import java.awt.Color;
 import java.awt.image.BufferedImage;
 import java.io.File;
 import java.io.IOException;
+
 import javax.imageio.ImageIO;
+
 import org.jgrapht.ext.JGraphXAdapter;
 import org.jgrapht.graph.DefaultDirectedGraph;
 import org.jgrapht.graph.DefaultEdge;
+import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
+
 import com.mxgraph.layout.mxCircleLayout;
 import com.mxgraph.layout.mxIGraphLayout;
 import com.mxgraph.util.mxCellRenderer;
@@ -20,7 +25,7 @@ public class GraphImageGenerationUnitTest {
 
     @Before
     public void createGraph() throws IOException {
-        File imgFile = new File("src/test/resources/graph.png");
+        File imgFile = new File("src/test/resources/graph1.png");
         imgFile.createNewFile();
         g = new DefaultDirectedGraph<String, DefaultEdge>(DefaultEdge.class);
         String x1 = "x1";
@@ -34,12 +39,18 @@ public class GraphImageGenerationUnitTest {
         g.addEdge(x3, x1);
     }
 
+    @After
+    public void cleanup() {
+        File imgFile = new File("src/test/resources/graph1.png");
+        imgFile.deleteOnExit();
+    }
+
     @Test
     public void givenAdaptedGraph_whenWriteBufferedImage_ThenFileShouldExist() throws IOException {
         JGraphXAdapter<String, DefaultEdge> graphAdapter = new JGraphXAdapter<String, DefaultEdge>(g);
         mxIGraphLayout layout = new mxCircleLayout(graphAdapter);
         layout.execute(graphAdapter.getDefaultParent());
-        File imgFile = new File("src/test/resources/graph.png");
+        File imgFile = new File("src/test/resources/graph1.png");
         BufferedImage image = mxCellRenderer.createBufferedImage(graphAdapter, null, 2, Color.WHITE, true, null);
         ImageIO.write(image, "PNG", imgFile);
         assertTrue(imgFile.exists());

algorithms-miscellaneous-6/README.md

@@ -7,4 +7,6 @@
 - [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
 - [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
 - [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
+- [Implementing a 2048 Solver in Java](https://www.baeldung.com/2048-java-solver)
+- [Finding Top K Elements in an Array](https://www.baeldung.com/java-array-top-elements)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-5)

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/play2048/Play2048.java

@@ -1,7 +1,7 @@
 package com.baeldung.algorithms.play2048;
 
 public class Play2048 {
-    private static final int SIZE = 3;
+    private static final int SIZE = 4;
     private static final int INITIAL_NUMBERS = 2;
 
     public static void main(String[] args) {

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/BruteForceTopKElementsFinder.java

@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class BruteForceTopKElementsFinder implements TopKElementsFinder<Integer> {
+
+    public List<Integer> findTopK(List<Integer> input, int k) {
+        List<Integer> array = new ArrayList<>(input);
+        List<Integer> topKList = new ArrayList<>();
+
+        for (int i = 0; i < k; i++) {
+            int maxIndex = 0;
+
+            for (int j = 1; j < array.size(); j++) {
+                if (array.get(j) > array.get(maxIndex)) {
+                    maxIndex = j;
+                }
+            }
+
+            topKList.add(array.remove(maxIndex));
+        }
+
+        return topKList;
+    }
+}

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/MaxHeapTopKElementsFinder.java

@@ -0,0 +1,26 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.PriorityQueue;
+
+public class MaxHeapTopKElementsFinder implements TopKElementsFinder<Integer> {
+
+    public List<Integer> findTopK(List<Integer> input, int k) {
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>();
+
+        input.forEach(number -> {
+            maxHeap.add(number);
+
+            if (maxHeap.size() > k) {
+                maxHeap.poll();
+            }
+        });
+
+        List<Integer> topKList = new ArrayList<>(maxHeap);
+        Collections.reverse(topKList);
+
+        return topKList;
+    }
+}

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/TopKElementsFinder.java

@@ -0,0 +1,7 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.List;
+
+public interface TopKElementsFinder<T extends Comparable<T>> {
+    List<T> findTopK(List<T> input, int k);
+}

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/topkelements/TreeSetTopKElementsFinder.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.topkelements;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class TreeSetTopKElementsFinder implements TopKElementsFinder<Integer> {
+
+    public List<Integer> findTopK(List<Integer> input, int k) {
+        Set<Integer> sortedSet = new TreeSet<>(Comparator.reverseOrder());
+        sortedSet.addAll(input);
+
+        return sortedSet.stream().limit(k).collect(Collectors.toList());
+    }
+}

algorithms-miscellaneous-6/src/test/java/com/baeldung/algorithms/topkelements/TopKElementsFinderUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung.algorithms.topkelements;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+public class TopKElementsFinderUnitTest {
+    private final TopKElementsFinder<Integer> bruteForceFinder = new BruteForceTopKElementsFinder();
+    private final TopKElementsFinder<Integer> maxHeapFinder = new MaxHeapTopKElementsFinder();
+    private final TopKElementsFinder<Integer> treeSetFinder = new TreeSetTopKElementsFinder();
+
+    private final int k = 4;
+    private final List<Integer> distinctIntegers = Arrays.asList(1, 2, 3, 9, 7, 6, 12);
+    private final List<Integer> distinctIntegersTopK = Arrays.asList(9, 7, 6, 12);
+    private final List<Integer> nonDistinctIntegers = Arrays.asList(1, 2, 3, 3, 9, 9, 7, 6, 12);
+    private final List<Integer> nonDistinctIntegersTopK = Arrays.asList(9, 9, 7, 12);
+
+
+    @Test
+    public void givenArrayDistinctIntegers_whenBruteForceFindTopK_thenReturnKLargest() {
+        assertThat(bruteForceFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayDistinctIntegers_whenMaxHeapFindTopK_thenReturnKLargest() {
+        assertThat(maxHeapFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayDistinctIntegers_whenTreeSetFindTopK_thenReturnKLargest() {
+        assertThat(treeSetFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayNonDistinctIntegers_whenBruteForceFindTopK_thenReturnKLargest() {
+        assertThat(bruteForceFinder.findTopK(nonDistinctIntegers, k)).containsOnlyElementsOf(nonDistinctIntegersTopK);
+    }
+
+    @Test
+    public void givenArrayNonDistinctIntegers_whenMaxHeapFindTopK_thenReturnKLargest() {
+        assertThat(maxHeapFinder.findTopK(nonDistinctIntegers, k)).containsOnlyElementsOf(nonDistinctIntegersTopK);
+    }
+}

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)
@@ -11,3 +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)
+- [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-cxf/README.md

@@ -7,4 +7,3 @@ This module contains articles about Apache CXF
 - [Apache CXF Support for RESTful Web Services](https://www.baeldung.com/apache-cxf-rest-api)
 - [A Guide to Apache CXF with Spring](https://www.baeldung.com/apache-cxf-with-spring)
 - [Introduction to Apache CXF](https://www.baeldung.com/introduction-to-apache-cxf)
-- [Server-Sent Events (SSE) In JAX-RS](https://www.baeldung.com/java-ee-jax-rs-sse)

apache-cxf/sse-jaxrs/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Server-Sent Events (SSE) In JAX-RS](https://www.baeldung.com/java-ee-jax-rs-sse)

apache-libraries/pom.xml

@@ -2,7 +2,7 @@
 <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>apache-miscellaneous-1</artifactId>
+    <artifactId>apache-libraries</artifactId>
     <version>0.0.1-SNAPSHOT</version>
     <name>apache-libraries</name>
 

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)

apache-poi/src/main/java/com/baeldung/poi/excel/setformula/ExcelFormula.java

@@ -0,0 +1,26 @@
+package com.baeldung.poi.excel.setformula;
+
+import org.apache.poi.xssf.usermodel.XSSFCell;
+import org.apache.poi.xssf.usermodel.XSSFFormulaEvaluator;
+import org.apache.poi.xssf.usermodel.XSSFSheet;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+public class ExcelFormula {
+    public double setFormula(String fileLocation, XSSFWorkbook wb, String formula) throws IOException {
+        XSSFSheet sheet = wb.getSheetAt(0);
+        int lastCellNum = sheet.getRow(0).getLastCellNum();
+        XSSFCell formulaCell = sheet.getRow(0).createCell(lastCellNum);
+        formulaCell.setCellFormula(formula);
+        XSSFFormulaEvaluator formulaEvaluator = wb.getCreationHelper().createFormulaEvaluator();
+        formulaEvaluator.evaluateFormulaCell(formulaCell);
+        FileOutputStream fileOut = new FileOutputStream(new File(fileLocation));
+        wb.write(fileOut);
+        wb.close();
+        fileOut.close();
+        return formulaCell.getNumericCellValue();
+    }
+}

apache-poi/src/test/java/com/baeldung/poi/excel/setformula/ExcelFormulaUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.poi.excel.setformula;
+
+import org.apache.poi.ss.util.CellReference;
+import org.apache.poi.xssf.usermodel.XSSFSheet;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.junit.Assert;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Paths;
+
+class ExcelFormulaUnitTest {
+    private static String FILE_NAME = "com/baeldung/poi/excel/setformula/SetFormulaTest.xlsx";
+    private String fileLocation;
+    private ExcelFormula excelFormula;
+
+    @BeforeEach
+    public void setup() throws URISyntaxException {
+        fileLocation = Paths.get(ClassLoader.getSystemResource(FILE_NAME).toURI()).toString();
+        excelFormula = new ExcelFormula();
+    }
+
+    @Test
+    void givenExcelData_whenSetFormula_thenSuccess() throws IOException {
+        FileInputStream inputStream = new FileInputStream(new File(fileLocation));
+        XSSFWorkbook wb = new XSSFWorkbook(inputStream);
+        XSSFSheet sheet = wb.getSheetAt(0);
+        double resultColumnA = 0;
+        double resultColumnB = 0;
+        for (int row = 0; row <= sheet.getLastRowNum(); row++) {
+            resultColumnA += sheet.getRow(row).getCell(0).getNumericCellValue();
+            resultColumnB += sheet.getRow(row).getCell(1).getNumericCellValue();
+        }
+        String colNameA = CellReference.convertNumToColString(0);
+        String colNameB = CellReference.convertNumToColString(1);
+        String startCellA = colNameA + 1;
+        String stopCellA = colNameA + (sheet.getLastRowNum() + 1);
+        String sumFormulaForColumnA = String.format("SUM(%s:%s)", startCellA, stopCellA);
+        String startCellB = colNameB + 1;
+        String stopCellB = colNameB + (sheet.getLastRowNum() + 1);
+        String sumFormulaForColumnB = String.format("SUM(%s:%s)", startCellB, stopCellB);
+
+        double resultValue = excelFormula.setFormula(fileLocation, wb, sumFormulaForColumnA + "-" + sumFormulaForColumnB);
+
+        Assert.assertEquals(resultColumnA - resultColumnB, resultValue, 0d);
+    }
+}

apache-shiro/README.md

@@ -6,4 +6,4 @@ This module contains articles about Apache Shiro
 
 - [Introduction to Apache Shiro](https://www.baeldung.com/apache-shiro)
 - [Permissions-Based Access Control with Apache Shiro](https://www.baeldung.com/apache-shiro-access-control)
-
+- [Spring Security vs Apache Shiro](https://www.baeldung.com/spring-security-vs-apache-shiro)

apache-shiro/pom.xml

@@ -39,10 +39,19 @@
             <artifactId>jcl-over-slf4j</artifactId>
             <scope>runtime</scope>
         </dependency>
+        <!-- spring-sec -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-security</artifactId>
+        </dependency>
     </dependencies>
 
     <properties>
-        <apache-shiro-core-version>1.4.0</apache-shiro-core-version>
+        <apache-shiro-core-version>1.5.3</apache-shiro-core-version>
         <log4j-version>1.2.17</log4j-version>
     </properties>
 

apache-shiro/src/main/java/com/baeldung/comparison/shiro/CustomRealm.java

@@ -0,0 +1,96 @@
+package com.baeldung.comparison.shiro;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+import org.apache.shiro.authc.AuthenticationException;
+import org.apache.shiro.authc.AuthenticationInfo;
+import org.apache.shiro.authc.AuthenticationToken;
+import org.apache.shiro.authc.SimpleAuthenticationInfo;
+import org.apache.shiro.authc.UnknownAccountException;
+import org.apache.shiro.authc.UsernamePasswordToken;
+import org.apache.shiro.authz.AuthorizationInfo;
+import org.apache.shiro.authz.SimpleAuthorizationInfo;
+import org.apache.shiro.realm.jdbc.JdbcRealm;
+import org.apache.shiro.subject.PrincipalCollection;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class CustomRealm extends JdbcRealm {
+    
+    private Logger logger = LoggerFactory.getLogger(CustomRealm.class);
+
+    private Map<String, String> credentials = new HashMap<>();
+    private Map<String, Set<String>> roles = new HashMap<>();
+    private Map<String, Set<String>> permissions = new HashMap<>();
+
+    {
+        credentials.put("Tom", "password");
+        credentials.put("Jerry", "password");
+
+        roles.put("Jerry", new HashSet<>(Arrays.asList("ADMIN")));
+        roles.put("Tom", new HashSet<>(Arrays.asList("USER")));
+
+        permissions.put("ADMIN", new HashSet<>(Arrays.asList("READ", "WRITE")));
+        permissions.put("USER", new HashSet<>(Arrays.asList("READ")));
+    }
+
+    @Override
+    protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token) throws AuthenticationException {
+
+        UsernamePasswordToken userToken = (UsernamePasswordToken) token;
+
+        if (userToken.getUsername() == null || userToken.getUsername()
+            .isEmpty() || !credentials.containsKey(userToken.getUsername())) {
+            throw new UnknownAccountException("User doesn't exist");
+        }
+
+        return new SimpleAuthenticationInfo(userToken.getUsername(), credentials.get(userToken.getUsername()), getName());
+    }
+
+    @Override
+    protected AuthorizationInfo doGetAuthorizationInfo(PrincipalCollection principals) {
+        Set<String> roles = new HashSet<>();
+        Set<String> permissions = new HashSet<>();
+
+        for (Object user : principals) {
+            try {
+                roles.addAll(getRoleNamesForUser(null, (String) user));
+                permissions.addAll(getPermissions(null, null, roles));
+            } catch (SQLException e) {
+                logger.error(e.getMessage());
+            }
+        }
+        SimpleAuthorizationInfo authInfo = new SimpleAuthorizationInfo(roles);
+        authInfo.setStringPermissions(permissions);
+        return authInfo;
+    }
+
+    @Override
+    protected Set<String> getRoleNamesForUser(Connection conn, String username) throws SQLException {
+        if (!roles.containsKey(username)) {
+            throw new SQLException("User doesn't exist");
+        }
+        return roles.get(username);
+    }
+
+    @Override
+    protected Set<String> getPermissions(Connection conn, String username, Collection<String> roles) throws SQLException {
+        Set<String> userPermissions = new HashSet<>();
+
+        for (String role : roles) {
+            if (!permissions.containsKey(role)) {
+                throw new SQLException("Role doesn't exist");
+            }
+            userPermissions.addAll(permissions.get(role));
+        }
+        return userPermissions;
+    }
+
+}

apache-shiro/src/main/java/com/baeldung/comparison/shiro/ShiroApplication.java

@@ -0,0 +1,33 @@
+package com.baeldung.comparison.shiro;
+
+import org.apache.shiro.realm.Realm;
+import org.apache.shiro.spring.web.config.DefaultShiroFilterChainDefinition;
+import org.apache.shiro.spring.web.config.ShiroFilterChainDefinition;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration;
+import org.springframework.context.annotation.Bean;
+
+@SpringBootApplication(exclude = SecurityAutoConfiguration.class)
+public class ShiroApplication {
+
+    public static void main(String... args) {
+        SpringApplication.run(ShiroApplication.class, args);
+    }
+
+    @Bean
+    public Realm customRealm() {
+        return new CustomRealm();
+    }
+
+    @Bean
+    public ShiroFilterChainDefinition shiroFilterChainDefinition() {
+        DefaultShiroFilterChainDefinition filter = new DefaultShiroFilterChainDefinition();
+
+        filter.addPathDefinition("/home", "authc");
+        filter.addPathDefinition("/**", "anon");
+
+        return filter;
+    }
+
+}

apache-shiro/src/main/java/com/baeldung/comparison/shiro/controllers/ShiroController.java

@@ -0,0 +1,99 @@
+package com.baeldung.comparison.shiro.controllers;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.apache.shiro.SecurityUtils;
+import org.apache.shiro.authc.AuthenticationException;
+import org.apache.shiro.authc.UsernamePasswordToken;
+import org.apache.shiro.subject.Subject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.servlet.mvc.support.RedirectAttributes;
+
+import com.baeldung.comparison.shiro.models.UserCredentials;
+
+@Controller
+public class ShiroController {
+    
+    private Logger logger = LoggerFactory.getLogger(ShiroController.class);
+
+    @GetMapping("/")
+    public String getIndex() {
+        return "comparison/index";
+    }
+
+    @GetMapping("/login")
+    public String showLoginPage() {
+        return "comparison/login";
+    }
+
+    @PostMapping("/login")
+    public String doLogin(HttpServletRequest req, UserCredentials credentials, RedirectAttributes attr) {
+
+        Subject subject = SecurityUtils.getSubject();
+
+        if (!subject.isAuthenticated()) {
+            UsernamePasswordToken token = new UsernamePasswordToken(credentials.getUsername(), credentials.getPassword());
+            try {
+                subject.login(token);
+            } catch (AuthenticationException ae) {
+                logger.error(ae.getMessage());
+                attr.addFlashAttribute("error", "Invalid Credentials");
+                return "redirect:/login";
+            }
+        }
+        return "redirect:/home";
+    }
+
+    @GetMapping("/home")
+    public String getMeHome(Model model) {
+
+        addUserAttributes(model);
+
+        return "comparison/home";
+    }
+
+    @GetMapping("/admin")
+    public String adminOnly(Model model) {
+        addUserAttributes(model);
+
+        Subject currentUser = SecurityUtils.getSubject();
+        if (currentUser.hasRole("ADMIN")) {
+            model.addAttribute("adminContent", "only admin can view this");
+        }
+        return "comparison/home";
+    }
+
+    @PostMapping("/logout")
+    public String logout() {
+        Subject subject = SecurityUtils.getSubject();
+        subject.logout();
+        return "redirect:/";
+    }
+
+    private void addUserAttributes(Model model) {
+        Subject currentUser = SecurityUtils.getSubject();
+        String permission = "";
+
+        if (currentUser.hasRole("ADMIN")) {
+            model.addAttribute("role", "ADMIN");
+        } else if (currentUser.hasRole("USER")) {
+            model.addAttribute("role", "USER");
+        }
+
+        if (currentUser.isPermitted("READ")) {
+            permission = permission + " READ";
+        }
+
+        if (currentUser.isPermitted("WRITE")) {
+            permission = permission + " WRITE";
+        }
+        model.addAttribute("username", currentUser.getPrincipal());
+        model.addAttribute("permission", permission);
+    }
+
+}

apache-shiro/src/main/java/com/baeldung/comparison/shiro/models/UserCredentials.java

@@ -0,0 +1,28 @@
+package com.baeldung.comparison.shiro.models;
+
+public class UserCredentials {
+
+    private String username;
+    private String password;
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    @Override
+    public String toString() {
+        return "username = " + getUsername();
+    }
+}

apache-shiro/src/main/java/com/baeldung/comparison/springsecurity/Application.java

@@ -0,0 +1,19 @@
+package com.baeldung.comparison.springsecurity;
+
+import org.apache.shiro.spring.boot.autoconfigure.ShiroAnnotationProcessorAutoConfiguration;
+import org.apache.shiro.spring.boot.autoconfigure.ShiroAutoConfiguration;
+import org.apache.shiro.spring.config.web.autoconfigure.ShiroWebAutoConfiguration;
+import org.apache.shiro.spring.config.web.autoconfigure.ShiroWebFilterConfiguration;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication(exclude = {ShiroAutoConfiguration.class,
+        ShiroAnnotationProcessorAutoConfiguration.class,
+        ShiroWebAutoConfiguration.class,
+        ShiroWebFilterConfiguration.class})
+public class Application {
+
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+}

apache-shiro/src/main/java/com/baeldung/comparison/springsecurity/config/SecurityConfig.java

@@ -0,0 +1,45 @@
+package com.baeldung.comparison.springsecurity.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
+
+@EnableWebSecurity
+public class SecurityConfig extends WebSecurityConfigurerAdapter {
+
+    @Override
+    protected void configure(HttpSecurity http) throws Exception {
+        http.csrf().disable().authorizeRequests(authorize -> authorize.antMatchers("/index", "/login")
+            .permitAll()
+            .antMatchers("/home", "/logout")
+            .authenticated()
+            .antMatchers("/admin/**")
+            .hasRole("ADMIN"))
+            .formLogin(formLogin -> formLogin.loginPage("/login")
+                .failureUrl("/login-error"));
+    }
+
+    @Override
+    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
+        auth.inMemoryAuthentication()
+            .withUser("Jerry")
+            .password(passwordEncoder().encode("password"))
+            .authorities("READ", "WRITE")
+            .roles("ADMIN")
+            .and()
+            .withUser("Tom")
+            .password(passwordEncoder().encode("password"))
+            .authorities("READ")
+            .roles("USER");
+    }
+
+    @Bean
+    public PasswordEncoder passwordEncoder() {
+        return new BCryptPasswordEncoder();
+    }
+
+}

apache-shiro/src/main/java/com/baeldung/comparison/springsecurity/web/SpringController.java

@@ -0,0 +1,79 @@
+package com.baeldung.comparison.springsecurity.web;
+
+import java.util.Collection;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.springframework.security.authentication.AnonymousAuthenticationToken;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.security.core.userdetails.User;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+@Controller
+public class SpringController {
+
+    @GetMapping("/")
+    public String getIndex() {
+        return "comparison/index";
+    }
+
+    @GetMapping("/login")
+    public String showLoginPage() {
+        return "comparison/login";
+    }
+
+    @RequestMapping("/login-error")
+    public String loginError(Model model) {
+        model.addAttribute("error", "Invalid Credentials");
+        return "comparison/login";
+    }
+
+    @PostMapping("/login")
+    public String doLogin(HttpServletRequest req) {
+        return "redirect:/home";
+    }
+
+    @GetMapping("/home")
+    public String showHomePage(HttpServletRequest req, Model model) {
+        addUserAttributes(model);
+        return "comparison/home";
+    }
+
+    @GetMapping("/admin")
+    public String adminOnly(HttpServletRequest req, Model model) {
+        addUserAttributes(model);
+        model.addAttribute("adminContent", "only admin can view this");
+        return "comparison/home";
+    }
+
+    private void addUserAttributes(Model model) {
+        Authentication auth = SecurityContextHolder.getContext()
+            .getAuthentication();
+        if (auth != null && !auth.getClass()
+            .equals(AnonymousAuthenticationToken.class)) {
+            User user = (User) auth.getPrincipal();
+            model.addAttribute("username", user.getUsername());
+
+            Collection<GrantedAuthority> authorities = user.getAuthorities();
+
+            for (GrantedAuthority authority : authorities) {
+                if (authority.getAuthority()
+                    .contains("USER")) {
+                    model.addAttribute("role", "USER");
+                    model.addAttribute("permission", "READ");
+                } else if (authority.getAuthority()
+                    .contains("ADMIN")) {
+                    model.addAttribute("role", "ADMIN");
+                    model.addAttribute("permission", "READ WRITE");
+                }
+            }
+        }
+    }
+
+}

apache-shiro/src/main/java/com/baeldung/intro/Main.java

@@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.intro;
 
 import org.apache.shiro.SecurityUtils;
 import org.apache.shiro.authc.AuthenticationException;

apache-shiro/src/main/java/com/baeldung/intro/MyCustomRealm.java

@@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.intro;
 
 import java.sql.Connection;
 import java.sql.SQLException;

apache-shiro/src/main/java/com/baeldung/intro/ShiroSpringApplication.java

@@ -1,4 +1,4 @@
-package com.baeldung;
+package com.baeldung.intro;
 
 import org.apache.shiro.realm.Realm;
 import org.apache.shiro.spring.web.config.DefaultShiroFilterChainDefinition;
@@ -7,12 +7,13 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration;
 import org.springframework.context.annotation.Bean;
 
 /**
  * Created by smatt on 21/08/2017.
  */
-@SpringBootApplication
+@SpringBootApplication(exclude = SecurityAutoConfiguration.class)
 public class ShiroSpringApplication {
 
     private static final transient Logger log = LoggerFactory.getLogger(ShiroSpringApplication.class);
@@ -29,7 +30,7 @@ public class ShiroSpringApplication {
 
 
     @Bean
-    public ShiroFilterChainDefinition shiroFilterChainDefinition() {
+    public ShiroFilterChainDefinition filterChainDefinition() {
         DefaultShiroFilterChainDefinition filter
           = new DefaultShiroFilterChainDefinition();
 

apache-shiro/src/main/java/com/baeldung/intro/controllers/ShiroSpringController.java

@@ -1,6 +1,5 @@
-package com.baeldung.controllers;
+package com.baeldung.intro.controllers;
 
-import com.baeldung.models.UserCredentials;
 import org.apache.shiro.SecurityUtils;
 import org.apache.shiro.authc.AuthenticationException;
 import org.apache.shiro.authc.UsernamePasswordToken;
@@ -13,6 +12,8 @@ import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.servlet.mvc.support.RedirectAttributes;
 
+import com.baeldung.intro.models.UserCredentials;
+
 import javax.servlet.http.HttpServletRequest;
 
 @Controller

apache-shiro/src/main/java/com/baeldung/intro/models/UserCredentials.java

@@ -1,4 +1,4 @@
-package com.baeldung.models;
+package com.baeldung.intro.models;
 
 public class UserCredentials {
 

apache-shiro/src/main/java/com/baeldung/permissions/custom/Main.java

@@ -1,4 +1,4 @@
-package com.baeldung.shiro.permissions.custom;
+package com.baeldung.permissions.custom;
 
 import org.apache.shiro.SecurityUtils;
 import org.apache.shiro.authc.AuthenticationException;

apache-shiro/src/main/java/com/baeldung/permissions/custom/PathPermission.java

@@ -1,4 +1,4 @@
-package com.baeldung.shiro.permissions.custom;
+package com.baeldung.permissions.custom;
 
 import org.apache.shiro.authz.Permission;
 

apache-shiro/src/main/java/com/baeldung/permissions/custom/PathPermissionResolver.java

@@ -1,4 +1,4 @@
-package com.baeldung.shiro.permissions.custom;
+package com.baeldung.permissions.custom;
 
 import org.apache.shiro.authz.Permission;
 import org.apache.shiro.authz.permission.PermissionResolver;

apache-shiro/src/main/resources/templates/comparison/home.ftl

@@ -0,0 +1,19 @@
+<html>
+<head>
+    <title>Home Page</title>
+</head>
+<body style="margin-left: 30px;">
+<h1>Welcome ${username}!</h1>
+<p><strong>Role</strong>: ${role}</p>
+<p><strong>Permissions</strong></p>
+<p>${permission}</p>
+<a href="/admin">Admin only</a>
+<#if adminContent??>
+  ${adminContent}
+</#if>
+<br>
+<form role="form" action="/logout" method="POST">
+   <input type="Submit" value="Logout" />
+</form>
+</body>
+</html>

apache-shiro/src/main/resources/templates/comparison/index.ftl

@@ -0,0 +1,10 @@
+<html>
+<head>
+    <title>Index</title>
+</head>
+<body>
+    <h1>Welcome Guest!</h1>
+    <br>
+    Go to the <a href="/home">secured page
+</body>
+</html>

apache-shiro/src/main/resources/templates/comparison/login.ftl

@@ -0,0 +1,25 @@
+<html>
+<head>
+    <title>Login</title>
+</head>
+<body style="margin-left: 30px;">
+<h3>Login</h3>
+<br>
+<form action="/login" method="post">
+    <#if (error?length > 0)??>
+        <p style="color:darkred;">${error}</p>
+    <#else>
+    </#if>
+
+    <label for="username">Username</label>
+    <br>
+    <input type="text" name="username">
+    <br><br>
+    <label for="password">Password</label>
+    <br>
+    <input type="password" name="password">
+    <br><br>
+    <input type="submit" value="Submit">
+</form>
+</body>
+</html>

apache-shiro/src/test/java/com/baeldung/comparison/shiro/SpringContextTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.comparison.shiro;
+
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import com.baeldung.comparison.shiro.ShiroApplication;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(classes = { ShiroApplication.class })
+public class SpringContextTest {
+
+    @Test
+    public void whenSpringContextIsBootstrapped_thenNoExceptions() {
+
+    }
+
+}

apache-shiro/src/test/java/com/baeldung/comparison/springsecurity/SpringContextTest.java

@@ -0,0 +1,19 @@
+package com.baeldung.comparison.springsecurity;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import com.baeldung.comparison.springsecurity.Application;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest(classes = { Application.class })
+public class SpringContextTest {
+
+    @Test
+    public void whenSpringContextIsBootstrapped_thenNoExceptions() {
+
+    }
+
+}

aws-app-sync/pom.xml

@@ -2,23 +2,16 @@
 <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>
-    <parent>
-        <groupId>org.springframework.boot</groupId>
-        <artifactId>spring-boot-starter-parent</artifactId>
-        <version>2.2.6.RELEASE</version>
-        <relativePath/> <!-- lookup parent from repository -->
-    </parent>
-
-    <groupId>com.baeldung</groupId>
     <artifactId>aws-app-sync</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
     <name>aws-app-sync</name>
-
     <description>Spring Boot using AWS App Sync</description>
-
-    <properties>
-        <java.version>1.8</java.version>
-    </properties>
+    
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-boot-2</relativePath>
+    </parent>
 
     <dependencies>
 

aws-app-sync/src/test/java/com/baeldung/awsappsync/AwsAppSyncApplicationUnitTest.java

@@ -12,7 +12,7 @@ import static org.junit.jupiter.api.Assertions.*;
 
 @SpringBootTest
 @Disabled
-class AwsAppSyncApplicationTests {
+class AwsAppSyncApplicationUnitTest {
 
     @Test
     void givenGraphQuery_whenListEvents_thenReturnAllEvents() {

cdi/pom.xml

@@ -1,8 +1,8 @@
 <?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">
+        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>cdi</artifactId>
     <version>1.0-SNAPSHOT</version>
@@ -10,9 +10,9 @@
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-spring-4</artifactId>
+        <artifactId>parent-spring-5</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-spring-4</relativePath>
+        <relativePath>../parent-spring-5</relativePath>
     </parent>
 
     <dependencies>
@@ -26,28 +26,22 @@
             <artifactId>weld-se-core</artifactId>
             <version>${weld-se-core.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.hamcrest</groupId>
-            <artifactId>hamcrest</artifactId>
-            <version>${hamcrest.version}</version>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
             <version>${assertj-core.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.springframework</groupId>
-            <artifactId>spring-context</artifactId>
-            <version>${spring.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.aspectj</groupId>
             <artifactId>aspectjweaver</artifactId>
             <version>${aspectjweaver.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <version>${spring.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-test</artifactId>
@@ -61,7 +55,6 @@
         <weld-se-core.version>3.0.5.Final</weld-se-core.version>
         <aspectjweaver.version>1.9.2</aspectjweaver.version>
         <assertj-core.version>3.10.0</assertj-core.version>
-        <spring.version>5.1.2.RELEASE</spring.version>
     </properties>
 
 </project>

cloud-foundry-uaa/cf-uaa-oauth2-client/pom.xml

@@ -6,7 +6,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.example</groupId>
     <artifactId>cf-uaa-oauth2-client</artifactId>
-    <name>uaa-client-webapp</name>
+    <name>cf-uaa-oauth2-client</name>
     <description>Demo project for Spring Boot</description>
 
     <parent>

core-groovy-2/determine-datatype/pom.xml

@@ -1,44 +0,0 @@
-<project xmlns="http://maven.apache.org/POM/4.0.0"
-    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
-    <groupId>com.baeldung.groovy</groupId>
-    <artifactId>determine-datatype</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
-    <build>
-        <sourceDirectory>src</sourceDirectory>
-        <plugins>
-            <plugin>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.0</version>
-                <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
-                </configuration>
-            </plugin>
-            <plugin>
-                <groupId>org.codehaus.gmaven</groupId>
-                <artifactId>groovy-maven-plugin</artifactId>
-                <dependencies>
-                    <dependency>
-                        <groupId>org.codehaus.groovy</groupId>
-                        <artifactId>groovy-all</artifactId>
-                        <version>2.0.6</version>
-                    </dependency>
-                </dependencies>
-            </plugin>
-        </plugins>
-    </build>
-    <dependencies>
-        <!-- https://mvnrepository.com/artifact/org.junit/junit5-engine -->
-        <dependency>
-            <groupId>org.junit</groupId>
-            <artifactId>junit5-engine</artifactId>
-            <version>${junit5.version}</version>
-        </dependency>
-    </dependencies>
-
-    <properties>
-        <junit5.version>5.0.0-ALPHA</junit5.version>
-    </properties>
-</project>

core-groovy-2/determine-datatype/src/com/baeldung/groovy/determine/datatype/Person.groovy

@@ -1,14 +0,0 @@
-package com.baeldung.groovy.determine.datatype
-
-class Person {
-    
-    private int ageAsInt
-    private Double ageAsDouble
-    private String ageAsString
-    
-    Person() {}
-    Person(int ageAsInt) { this.ageAsInt =  ageAsInt}
-    Person(Double ageAsDouble) { this.ageAsDouble =  ageAsDouble}
-    Person(String ageAsString) { this.ageAsString =  ageAsString}    
-}
-class Student extends Person {}

core-groovy-2/determine-datatype/src/com/baeldung/groovy/determine/datatype/PersonTest.groovy

@@ -1,55 +0,0 @@
-package com.baeldung.groovy.determine.datatype;
-
-import org.junit.Assert
-import org.junit.Test;
-
-public class PersonTest {
-    
-    @Test
-    public void givenWhenParameterTypeIsInteger_thenReturnTrue() {
-        Person personObj = new Person(10)
-        Assert.assertTrue(personObj.ageAsInt instanceof Integer);
-    }
-    
-    @Test
-    public void givenWhenParameterTypeIsDouble_thenReturnTrue() {
-        Person personObj = new Person(10.0)
-        Assert.assertTrue((personObj.ageAsDouble).getClass() == Double)
-    }
-    
-    @Test
-    public void givenWhenParameterTypeIsString_thenReturnTrue() {
-        Person personObj = new Person("10 years")
-        Assert.assertTrue(personObj.ageAsString.class == String)
-    }
-    
-    @Test
-    public void givenClassName_WhenParameterIsInteger_thenReturnTrue() {
-        Assert.assertTrue(Person.class.getDeclaredField('ageAsInt').type == int.class)
-    }
-    
-    @Test
-    public void givenWhenObjectIsInstanceOfType_thenReturnTrue() {
-        Person personObj = new Person()
-        Assert.assertTrue(personObj instanceof Person)
-    }
-
-    @Test
-    public void givenWhenInstanceIsOfSubtype_thenReturnTrue() {
-        Student studentObj = new Student()
-        Assert.assertTrue(studentObj in Person)
-    }
-    
-    @Test
-    public void givenGroovyList_WhenFindClassName_thenReturnTrue() {
-      def ageList = ['ageAsString','ageAsDouble', 10]   
-      Assert.assertTrue(ageList.class == ArrayList)     
-      Assert.assertTrue(ageList.getClass() == ArrayList)
-    }
-    
-    @Test
-    public void givenGrooyMap_WhenFindClassName_thenReturnTrue() {
-      def ageMap = [ageAsString: '10 years', ageAsDouble: 10.0]
-      Assert.assertFalse(ageMap.class == LinkedHashMap)
-    }
-}

core-groovy/README.md

@@ -13,4 +13,5 @@ This module contains articles about core Groovy concepts
 - [Converting a String to a Date in Groovy](https://www.baeldung.com/groovy-string-to-date)
 - [Guide to I/O in Groovy](https://www.baeldung.com/groovy-io)
 - [Convert String to Integer in Groovy](https://www.baeldung.com/groovy-convert-string-to-integer)
+- [Groovy Variable Scope](https://www.baeldung.com/groovy/variable-scope)
 - [[More -->]](/core-groovy-2)

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: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">
+        xmlns="http://maven.apache.org/POM/4.0.0"
+        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-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>
-        <artifactId>parent-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-        <relativePath>../../</relativePath>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <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-10/src/test/java/com/baeldung/java10/list/CopyListServiceUnitTest.java

@@ -10,5 +10,6 @@ public class CopyListServiceUnitTest {
     @Test(expected = UnsupportedOperationException.class)
     public void whenModifyCopyOfList_thenThrowsException() {
         List<Integer> copyList = List.copyOf(Arrays.asList(1, 2, 3, 4));
+        copyList.add(4);
     }
 }

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

@@ -8,7 +8,7 @@ This module contains articles about Java 11 core features
 - [Java 11 Local Variable Syntax for Lambda Parameters](https://www.baeldung.com/java-var-lambda-params)
 - [Java 11 String API Additions](https://www.baeldung.com/java-11-string-api)
 - [Java 11 Nest Based Access Control](https://www.baeldung.com/java-nest-based-access-control)
-- [Exploring the New HTTP Client in Java 9 and 11](https://www.baeldung.com/java-9-http-client)
+- [Exploring the New HTTP Client in Java](https://www.baeldung.com/java-9-http-client)
 - [An Introduction to Epsilon GC: A No-Op Experimental Garbage Collector](https://www.baeldung.com/jvm-epsilon-gc-garbage-collector)
 - [Guide to jlink](https://www.baeldung.com/jlink)
 - [Negate a Predicate Method Reference with Java 11](https://www.baeldung.com/java-negate-predicate-method-reference)

core-java-modules/core-java-8-datetime-2/pom.xml

@@ -6,7 +6,7 @@
     <modelVersion>4.0.0</modelVersion>
     <artifactId>core-java-8-datetime-2</artifactId>
     <version>${project.parent.version}</version>
-    <name>core-java-8-datetime</name>
+    <name>core-java-8-datetime-2</name>
     <packaging>jar</packaging>
     <parent>
         <groupId>com.baeldung.core-java-modules</groupId>

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-9-jigsaw/src/simple-modules/main.app/com/baeldung/modules/main/MainApp.java

@@ -1,12 +1,15 @@
 package com.baeldung.modules.main;
 
+import com.baeldung.modules.hello.HelloInterface;
 import com.baeldung.modules.hello.HelloModules;
+import java.util.ServiceLoader;
 
 public class MainApp {
     public static void main(String[] args) {
         HelloModules.doSomething();
-
-        HelloModules module = new HelloModules();
-        module.sayHello();
+        
+        Iterable<HelloInterface> services = ServiceLoader.load(HelloInterface.class);
+        HelloInterface service = services.iterator().next();
+        service.sayHello();
     }
 }

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

@@ -13,3 +13,5 @@ This module contains articles about core Java features that have been introduced
 - [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
 - [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)
 - [Multi-Release JAR Files with Maven](https://www.baeldung.com/maven-multi-release-jars)
+- [The Difference between RxJava API and the Java 9 Flow API](https://www.baeldung.com/rxjava-vs-java-flow-api)
+- [How to Get a Name of a Method Being Executed?](https://www.baeldung.com/java-name-of-executing-method)

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/currentmethod/CurrentExecutingMethodUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.java9.currentmethod;
+
+import org.junit.Test;
+
+import java.util.Optional;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class CurrentExecutingMethodUnitTest {
+
+    @Test
+    public void givenJava9_whenWalkingTheStack_thenFindMethod() {
+        StackWalker walker = StackWalker.getInstance();
+        Optional<String> methodName = walker.walk(frames -> frames
+          .findFirst()
+          .map(StackWalker.StackFrame::getMethodName)
+        );
+
+        assertTrue(methodName.isPresent());
+        assertEquals("givenJava9_whenWalkingTheStack_thenFindMethod", methodName.get());
+    }
+}

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

@@ -9,3 +9,4 @@ This module contains articles about Java 9 core features
 - [Iterate Through a Range of Dates in Java](https://www.baeldung.com/java-iterate-date-range)
 - [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
 - [Immutable ArrayList in Java](https://www.baeldung.com/java-immutable-list)
+- [Easy Ways to Write a Java InputStream to an OutputStream](https://www.baeldung.com/java-inputstream-to-outputstream)

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

@@ -5,4 +5,4 @@ This module contains complete guides about arrays in Java
 ### Relevant Articles: 
 - [Arrays in Java: A Reference Guide](https://www.baeldung.com/java-arrays-guide)
 - [Guide to the java.util.Arrays Class](https://www.baeldung.com/java-util-arrays)
-- [What is [Ljava.lang.Object;?]](https://www.baeldung.com/java-tostring-array)
+- [What is \[Ljava.lang.Object;?](https://www.baeldung.com/java-tostring-array)

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-arrays-operations-advanced/src/main/java/com/baeldung/arraycompare/Plane.java

@@ -0,0 +1,39 @@
+package com.baeldung.arraycompare;
+
+import java.util.Objects;
+
+public class Plane {
+
+    private final String name;
+
+    private final String model;
+
+    public Plane(String name, String model) {
+
+        this.name = name;
+        this.model = model;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getModel() {
+        return model;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Plane plane = (Plane) o;
+        return Objects.equals(name, plane.name) && Objects.equals(model, plane.model);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name, model);
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/DeepEqualsCompareUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class DeepEqualsCompareUnitTest {
+
+    @Test
+    public void givenSameContents_whenDeepEquals_thenTrue() {
+        final Plane[][] planes1 = new Plane[][] { new Plane[] { new Plane("Plane 1", "A320") },
+            new Plane[] { new Plane("Plane 2", "B738") } };
+        final Plane[][] planes2 = new Plane[][] { new Plane[] { new Plane("Plane 1", "A320") },
+            new Plane[] { new Plane("Plane 2", "B738") } };
+
+        assertThat(Arrays.deepEquals(planes1, planes2)).isTrue();
+    }
+
+    @Test
+    public void givenSameContentsWithDifferentOrder_whenDeepEquals_thenFalse() {
+        final Plane[][] planes1 = new Plane[][] { new Plane[] { new Plane("Plane 1", "A320") },
+            new Plane[] { new Plane("Plane 2", "B738") } };
+        final Plane[][] planes2 = new Plane[][] { new Plane[] { new Plane("Plane 2", "B738") },
+            new Plane[] { new Plane("Plane 1", "A320") } };
+
+        assertThat(Arrays.deepEquals(planes1, planes2)).isFalse();
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/EqualsCompareUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EqualsCompareUnitTest {
+
+    @Test
+    public void givenSameContents_whenEquals_thenTrue() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+
+        assertThat(Arrays.equals(planes1, planes2)).isTrue();
+    }
+
+    @Test
+    public void givenSameContentsDifferentOrder_whenEquals_thenFalse() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = new String[] { "B738", "A320", "A321", "A319", "B77W", "B737", "A333", "A332" };
+
+        assertThat(Arrays.equals(planes1, planes2)).isFalse();
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/LengthsCompareUnitTest.java

@@ -0,0 +1,18 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class LengthsCompareUnitTest {
+
+    @Test
+    public void givenSameContent_whenSizeCompare_thenTrue() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final Integer[] quantities = new Integer[] { 10, 12, 34, 45, 12, 43, 5, 2 };
+
+        assertThat(planes1).hasSize(8);
+        assertThat(quantities).hasSize(8);
+    }
+}
+

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/OrderCompareUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertTrue;
+
+public class OrderCompareUnitTest {
+    @Test
+    public void givenSameContentDifferentOrder_whenSortedAndDeepEquals_thenTrue() {
+        final Plane[][] planes1 = new Plane[][] {
+            new Plane[] { new Plane("Plane 1", "A320"), new Plane("Plane 2", "B738") } };
+        final Plane[][] planes2 = new Plane[][] {
+            new Plane[] { new Plane("Plane 2", "B738"), new Plane("Plane 1", "A320") } };
+
+        Comparator<Plane> planeComparator = (o1, o2) -> {
+            if (o1.getName()
+                .equals(o2.getName())) {
+                return o2.getModel()
+                    .compareTo(o1.getModel());
+            }
+            return o2.getName()
+                .compareTo(o1.getName());
+        };
+        Arrays.sort(planes1[0], planeComparator);
+        Arrays.sort(planes2[0], planeComparator);
+
+        assertThat(Arrays.deepEquals(planes1, planes2)).isTrue();
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/ReferenceCompareUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ReferenceCompareUnitTest {
+
+    @Test
+    public void givenSameReferences_whenSame_thenTrue() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = planes1;
+
+        assertThat(planes1).isSameAs(planes2);
+
+        planes2[0] = "747";
+
+        assertThat(planes1).isSameAs(planes2);
+        assertThat(planes2[0]).isEqualTo("747");
+        assertThat(planes1[0]).isEqualTo("747");
+    }
+
+    @Test
+    public void givenSameContentDifferentReferences_whenSame_thenFalse() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+
+        assertThat(planes1).isNotSameAs(planes2);
+    }
+}

core-java-modules/core-java-arrays-operations-basic/pom.xml

@@ -13,32 +13,6 @@
     <name>core-java-arrays-operations-basic</name>
     <packaging>jar</packaging>
 
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-shade-plugin</artifactId>
-                <version>${shade.plugin.version}</version>
-                <executions>
-                    <execution>
-                        <phase>package</phase>
-                        <goals>
-                            <goal>shade</goal>
-                        </goals>
-                        <configuration>
-                            <finalName>benchmarks</finalName>
-                            <transformers>
-                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
-                                    <mainClass>org.openjdk.jmh.Main</mainClass>
-                                </transformer>
-                            </transformers>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-        </plugins>
-    </build>
-
     <dependencies>
         <dependency>
             <groupId>org.apache.commons</groupId>
@@ -66,6 +40,32 @@
         </dependency>
     </dependencies>
 
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>${shade.plugin.version}</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <finalName>benchmarks</finalName>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>org.openjdk.jmh.Main</mainClass>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
     <properties>
         <shade.plugin.version>3.2.0</shade.plugin.version>
 

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

@@ -14,32 +14,6 @@
     <name>core-java-arrays-sorting</name>
     <packaging>jar</packaging>
 
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-shade-plugin</artifactId>
-                <version>${shade.plugin.version}</version>
-                <executions>
-                    <execution>
-                        <phase>package</phase>
-                        <goals>
-                            <goal>shade</goal>
-                        </goals>
-                        <configuration>
-                            <finalName>benchmarks</finalName>
-                            <transformers>
-                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
-                                    <mainClass>org.openjdk.jmh.Main</mainClass>
-                                </transformer>
-                            </transformers>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-        </plugins>
-    </build>
-
     <dependencies>
         <!-- Utilities -->
         <dependency>
@@ -74,6 +48,32 @@
         </dependency>
     </dependencies>
 
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>${shade.plugin.version}</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <finalName>benchmarks</finalName>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>org.openjdk.jmh.Main</mainClass>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
     <properties>
         <shade.plugin.version>3.2.0</shade.plugin.version>
 

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

@@ -3,6 +3,7 @@
 ## Core Java Collections Cookbooks and Examples
 
 ### Relevant Articles: 
+
 - [Time Comparison of Arrays.sort(Object[]) and Arrays.sort(int[])](https://www.baeldung.com/arrays-sortobject-vs-sortint)
 - [Java ArrayList vs Vector](https://www.baeldung.com/java-arraylist-vs-vector)
 - [Differences Between HashMap and Hashtable](https://www.baeldung.com/hashmap-hashtable-differences)
@@ -10,3 +11,5 @@
 - [Performance of contains() in a HashSet vs ArrayList](https://www.baeldung.com/java-hashset-arraylist-contains-performance)
 - [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-3/pom.xml

@@ -16,6 +16,11 @@
     </parent>
 
     <dependencies>
+        <dependency>
+            <groupId>org.openjdk.jol</groupId>
+            <artifactId>jol-core</artifactId>
+            <version>${jol-core.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.openjdk.jmh</groupId>
             <artifactId>jmh-core</artifactId>
@@ -27,11 +32,17 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.10</version>
+        </dependency>
     </dependencies>
 
     <properties>
         <openjdk.jmh.version>1.19</openjdk.jmh.version>
         <assertj.version>3.11.1</assertj.version>
+        <jol-core.version>0.10</jol-core.version>
     </properties>
 
 </project>

core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/convertarrayprimitives/ConvertPrimitivesArrayToList.java

@@ -0,0 +1,47 @@
+package com.baeldung.collections.iterators;
+
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import com.google.common.primitives.Ints;
+import org.apache.commons.lang3.ArrayUtils;
+
+public class ConvertPrimitivesArrayToList {
+
+    public static void failConvert() {
+        int[] input = new int[]{1,2,3,4};
+        // List<Integer> inputAsList = Arrays.asList(input);
+    }
+
+    public static List<Integer> iterateConvert(int[] input) {
+        List<Integer> output = new ArrayList<Integer>();
+        for (int value : input) {
+            output.add(value);
+        }
+        return output;
+    }
+
+    public static List<Integer> streamConvert(int[] input) {
+        List<Integer> output = Arrays.stream(input).boxed().collect(Collectors.toList());
+        return output;
+    }
+
+    public static List<Integer> streamConvertIntStream(int[] input) {
+        List<Integer> output = IntStream.of(input).boxed().collect(Collectors.toList());
+        return output;
+    }
+
+    public static List<Integer> guavaConvert(int[] input) {
+        List<Integer> output = Ints.asList(input);
+        return output;
+    }
+
+    public static List<Integer> apacheCommonConvert(int[] input) {
+        Integer[] outputBoxed = ArrayUtils.toObject(input);
+        List<Integer> output = Arrays.asList(outputBoxed);
+        return output;
+    }
+
+}

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/bitset/BitSetUnitTest.java

@@ -0,0 +1,178 @@
+package com.baeldung.collections.bitset;
+
+import org.junit.Test;
+import org.openjdk.jol.info.ClassLayout;
+import org.openjdk.jol.info.GraphLayout;
+
+import java.util.BitSet;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BitSetUnitTest {
+
+    @Test
+    public void givenBoolArray_whenMemoryLayout_thenConsumeMoreThanOneBit() {
+        boolean[] bits = new boolean[1024 * 1024];
+
+        System.out.println(ClassLayout.parseInstance(bits).toPrintable());
+    }
+
+    @Test
+    public void givenBitSet_whenMemoryLayout_thenConsumeOneBitPerFlag() {
+        BitSet bitSet = new BitSet(1024 * 1024);
+
+        System.out.println(GraphLayout.parseInstance(bitSet).toPrintable());
+    }
+
+    @Test
+    public void givenBitSet_whenSetting_thenShouldBeTrue() {
+        BitSet bitSet = new BitSet();
+
+        bitSet.set(10);
+        assertThat(bitSet.get(10)).isTrue();
+
+        bitSet.set(20, 30);
+        for (int i = 20; i <= 29; i++) {
+            assertThat(bitSet.get(i)).isTrue();
+        }
+        assertThat(bitSet.get(30)).isFalse();
+
+        bitSet.set(10, false);
+        assertThat(bitSet.get(10)).isFalse();
+
+        bitSet.set(20, 30, false);
+        for (int i = 20; i <= 30; i++) {
+            assertThat(bitSet.get(i)).isFalse();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenClearing_thenShouldBeFalse() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(42);
+        assertThat(bitSet.get(42)).isTrue();
+
+        bitSet.clear(42);
+        assertThat(bitSet.get(42)).isFalse();
+
+        bitSet.set(10, 20);
+        for (int i = 10; i < 20; i++) {
+            assertThat(bitSet.get(i)).isTrue();
+        }
+
+        bitSet.clear(10, 20);
+        for (int i = 10; i < 20; i++) {
+            assertThat(bitSet.get(i)).isFalse();
+        }
+
+        bitSet.set(10, 20);
+        bitSet.clear();
+        for (int i = 0; i < 100; i++) {
+            assertThat(bitSet.get(i)).isFalse();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenGettingElements_thenShouldReturnRequestedBits() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(42);
+
+        assertThat(bitSet.get(42)).isTrue();
+        assertThat(bitSet.get(43)).isFalse();
+
+        bitSet.set(10, 20);
+        BitSet newBitSet = bitSet.get(10, 20);
+        for (int i = 0; i < 10; i++) {
+            assertThat(newBitSet.get(i)).isTrue();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenFlip_thenTogglesTrueToFalseAndViceVersa() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(42);
+        bitSet.flip(42);
+        assertThat(bitSet.get(42)).isFalse();
+
+        bitSet.flip(12);
+        assertThat(bitSet.get(12)).isTrue();
+
+        bitSet.flip(30, 40);
+        for (int i = 30; i < 40; i++) {
+            assertThat(bitSet.get(i)).isTrue();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenGettingTheSize_thenReturnsTheSize() {
+        BitSet defaultBitSet = new BitSet();
+        assertThat(defaultBitSet.size()).isEqualTo(64);
+
+        BitSet bitSet = new BitSet(1024);
+        assertThat(bitSet.size()).isEqualTo(1024);
+
+        assertThat(bitSet.cardinality()).isEqualTo(0);
+        bitSet.set(10, 30);
+        assertThat(bitSet.cardinality()).isEqualTo(30 - 10);
+
+        assertThat(bitSet.length()).isEqualTo(30);
+        bitSet.set(100);
+        assertThat(bitSet.length()).isEqualTo(101);
+
+        assertThat(bitSet.isEmpty()).isFalse();
+        bitSet.clear();
+        assertThat(bitSet.isEmpty()).isTrue();
+    }
+
+    @Test
+    public void givenBitSet_whenSetOperations_thenShouldReturnAnotherBitSet() {
+        BitSet first = new BitSet();
+        first.set(5, 10);
+
+        BitSet second = new BitSet();
+        second.set(7, 15);
+
+        assertThat(first.intersects(second)).isTrue();
+
+        first.and(second);
+        assertThat(first.get(7)).isTrue();
+        assertThat(first.get(8)).isTrue();
+        assertThat(first.get(9)).isTrue();
+        assertThat(first.get(10)).isFalse();
+
+        first.clear();
+        first.set(5, 10);
+
+        first.xor(second);
+        for (int i = 5; i < 7; i++) {
+            assertThat(first.get(i)).isTrue();
+        }
+        for (int i = 10; i < 15; i++) {
+            assertThat(first.get(i)).isTrue();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenStream_thenStreamsAllSetBits() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(15, 25);
+
+        bitSet.stream().forEach(System.out::println);
+        assertThat(bitSet.stream().count()).isEqualTo(10);
+    }
+
+    @Test
+    public void givenBitSet_whenNextOrPrev_thenReturnsTheNextOrPrevClearOrSetBit() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(15, 25);
+
+        assertThat(bitSet.nextSetBit(13)).isEqualTo(15);
+        assertThat(bitSet.nextSetBit(25)).isEqualTo(-1);
+
+        assertThat(bitSet.nextClearBit(23)).isEqualTo(25);
+
+        assertThat(bitSet.previousClearBit(24)).isEqualTo(14);
+        assertThat(bitSet.previousSetBit(29)).isEqualTo(24);
+        assertThat(bitSet.previousSetBit(14)).isEqualTo(-1);
+    }
+}

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/convertarrayprimitives/ConvertPrimitivesArrayToListUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.collections.iterators;
+
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.stream.Collectors;
+import com.google.common.primitives.Ints;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class ConvertPrimitivesArrayToListUnitTest {
+
+    @Test
+    public void givenArrayWithPrimitives_whenIterativeConvert_thenArrayGetsConverted() {
+        assertEquals(Arrays.asList(1,2,3,4), ConvertPrimitivesArrayToList.iterateConvert(new int[]{1,2,3,4}));
+    }
+
+    @Test
+    public void givenArrayWithPrimitives_whenStreamConvert_thenArrayGetsConverted() {
+        assertEquals(Arrays.asList(1,2,3,4), ConvertPrimitivesArrayToList.streamConvert(new int[]{1,2,3,4}));
+    }
+
+    @Test
+    public void givenArrayWithPrimitives_whenIntStreamConvert_thenArrayGetsConverted() {
+        assertEquals(Arrays.asList(1,2,3,4), ConvertPrimitivesArrayToList.streamConvertIntStream(new int[]{1,2,3,4}));
+    }
+
+    @Test
+    public void givenArrayWithPrimitives_whenGuavaConvert_thenArrayGetsConverted() {
+        assertEquals(Arrays.asList(1,2,3,4), ConvertPrimitivesArrayToList.guavaConvert(new int[]{1,2,3,4}));
+    }
+
+    @Test
+    public void givenArrayWithPrimitives_whenApacheCommonConvert_thenArrayGetsConverted() {
+        assertEquals(Arrays.asList(1,2,3,4), ConvertPrimitivesArrayToList.apacheCommonConvert(new int[]{1,2,3,4}));
+    }
+}

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-list-3/pom.xml

@@ -21,6 +21,12 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+            <scope>compile</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/difference/FindDifferencesBetweenListsUnitTest.java

@@ -0,0 +1,96 @@
+package com.baeldung.list.difference;
+
+import com.google.common.collect.Sets;
+import org.apache.commons.collections4.CollectionUtils;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.assertj.core.api.Assertions.*;
+
+public class FindDifferencesBetweenListsUnitTest {
+
+    private static final List<String> listOne = Arrays.asList("Jack", "Tom", "Sam", "John", "James", "Jack");
+    private static final List<String> listTwo = Arrays.asList("Jack", "Daniel", "Sam", "Alan", "James", "George");
+
+    @Test
+    public void givenLists_whenUsingPlainJavaImpl_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(listOne);
+        differences.removeAll(listTwo);
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactly("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingPlainJavaImpl_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(listTwo);
+        differences.removeAll(listOne);
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingJavaStreams_thenDifferencesAreFound() {
+        List<String> differences = listOne.stream()
+                .filter(element -> !listTwo.contains(element))
+                .collect(Collectors.toList());
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactly("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingJavaStreams_thenDifferencesAreFound() {
+        List<String> differences = listTwo.stream()
+                .filter(element -> !listOne.contains(element))
+                .collect(Collectors.toList());
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingGoogleGuava_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(Sets.difference(Sets.newHashSet(listOne), Sets.newHashSet(listTwo)));
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactlyInAnyOrder("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingGoogleGuava_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(Sets.difference(Sets.newHashSet(listTwo), Sets.newHashSet(listOne)));
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactlyInAnyOrder("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingApacheCommons_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>((CollectionUtils.removeAll(listOne, listTwo)));
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactly("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingApacheCommons_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>((CollectionUtils.removeAll(listTwo, listOne)));
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingPlainJavaImpl_thenDifferencesWithDuplicatesAreFound() {
+        List<String> differences = new ArrayList<>(listOne);
+        listTwo.forEach(differences::remove);
+        assertThat(differences).containsExactly("Tom", "John", "Jack");
+    }
+
+    @Test
+    public void givenLists_whenUsingApacheCommons_thenDifferencesWithDuplicatesAreFound() {
+        List<String> differences = new ArrayList<>(CollectionUtils.subtract(listOne, listTwo));
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Tom", "John", "Jack");
+    }
+
+}

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

@@ -21,20 +21,15 @@
             <version>${eclipse-collections.version}</version>
         </dependency>
         <dependency>
-            <groupId>net.sf.trove4j</groupId>
-            <artifactId>trove4j</artifactId>
-            <version>${trove4j.version}</version>
+            <groupId>com.carrotsearch</groupId>
+            <artifactId>hppc</artifactId>
+            <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 cern.colt.map.OpenIntDoubleHashMap;
-import gnu.trove.map.TDoubleIntMap;
-import gnu.trove.map.hash.TDoubleIntHashMap;
+import com.carrotsearch.hppc.IntLongHashMap;
+import com.carrotsearch.hppc.IntLongScatterMap;
+import com.carrotsearch.hppc.IntObjectHashMap;
+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-concurrency-advanced-3/README.md

@@ -15,4 +15,5 @@ This module contains articles about advanced topics about multithreading with co
 - [The ABA Problem in Concurrency](https://www.baeldung.com/cs/aba-concurrency)
 - [Introduction to Lock-Free Data Structures](https://www.baeldung.com/lock-free-programming)
 - [Introduction to Exchanger in Java](https://www.baeldung.com/java-exchanger)
+- [Why Not To Start A Thread In The Constructor?](https://www.baeldung.com/java-thread-constructor)
 - [[<-- previous]](/core-java-modules/core-java-concurrency-advanced-2)

core-java-modules/core-java-concurrency-advanced-3/src/test/java/com/baeldung/workstealing/PrimeNumbersManualTest.java

@@ -15,7 +15,15 @@ import java.util.logging.Logger;
 
 import static org.junit.Assert.fail;
 
-public class PrimeNumbersUnitManualTest {
+/**
+ * This test expects the file target/test-classes/META-INF/BenchmarkList to be present.
+ *
+ * Before running the test ensure that the file is present. 
+ * If not, please run mvn install on the module.
+ * 
+ */
+
+public class PrimeNumbersManualTest {
 
     private static Logger logger = Logger.getAnonymousLogger();
 

core-java-modules/core-java-concurrency-advanced/src/main/java/com/baeldung/threadlocal/ThreadLocalAwareThreadPool.java

@@ -0,0 +1,25 @@
+package com.baeldung.threadlocal;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+public class ThreadLocalAwareThreadPool extends ThreadPoolExecutor {
+
+    public ThreadLocalAwareThreadPool(int corePoolSize,
+      int maximumPoolSize,
+      long keepAliveTime,
+      TimeUnit unit,
+      BlockingQueue<Runnable> workQueue,
+      ThreadFactory threadFactory,
+      RejectedExecutionHandler handler) {
+        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
+    }
+
+    @Override
+    protected void afterExecute(Runnable r, Throwable t) {
+        // Call remove on each ThreadLocal
+    }
+}

core-java-modules/core-java-concurrency-basic-2/README.md

@@ -3,10 +3,12 @@
 This module contains articles about basic Java concurrency
 
 ### Relevant Articles: 
+
 - [How to Delay Code Execution in Java](https://www.baeldung.com/java-delay-code-execution)
 - [wait and notify() Methods in Java](https://www.baeldung.com/java-wait-notify)
 - [Difference Between Wait and Sleep in Java](https://www.baeldung.com/java-wait-and-sleep)
 - [Guide to the Synchronized Keyword in Java](https://www.baeldung.com/java-synchronized)
 - [Life Cycle of a Thread in Java](https://www.baeldung.com/java-thread-lifecycle)
 - [Guide to AtomicMarkableReference](https://www.baeldung.com/java-atomicmarkablereference)
+- [Why are Local Variables Thread-Safe in Java](https://www.baeldung.com/java-local-variables-thread-safe)
 - [[<-- Prev]](/core-java-modules/core-java-concurrency-basic)

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/localvariables/LocalAndLambda.java

@@ -0,0 +1,10 @@
+package com.baeldung.concurrent.localvariables;
+
+public class LocalAndLambda {
+    public static void main(String... args) {
+        String text = "";
+        // Un-commenting the next line will break compilation, because text is no longer effectively final
+        // text = "675";
+        new Thread(() -> System.out.println(text)).start();
+    }
+}

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/localvariables/LocalVariables.java

@@ -0,0 +1,20 @@
+package com.baeldung.concurrent.localvariables;
+
+import java.security.SecureRandom;
+
+public class LocalVariables implements Runnable {
+    private int field;
+
+    public static void main(String... args) {
+        LocalVariables target = new LocalVariables();
+        new Thread(target).start();
+        new Thread(target).start();
+    }
+
+    @Override
+    public void run() {
+        field = new SecureRandom().nextInt();
+        int local = new SecureRandom().nextInt();
+        System.out.println(field + " - " + local);
+    }
+}

core-java-modules/core-java-concurrency-collections-2/README.md

@@ -1,3 +1,5 @@
 ### Relevant Articles:
 
 - [Introduction to Lock Striping](https://www.baeldung.com/java-lock-stripping)
+- [Guide to the Java TransferQueue](http://www.baeldung.com/java-transfer-queue)
+- [[<-- Prev]](/core-java-modules/core-java-concurrency-collections)

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

@@ -3,9 +3,16 @@
     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.concurrent.lock</groupId>
     <artifactId>core-java-concurrency-collections-2</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-concurrency-collections-2</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>
         <dependency>
@@ -30,19 +37,6 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
-    <build>
-        <sourceDirectory>src</sourceDirectory>
-        <plugins>
-            <plugin>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.8.0</version>
-                <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
 
     <properties>
         <jmh.version>1.21</jmh.version>

core-java-modules/core-java-concurrency-collections-2/src/test/java/com/baeldung/concurrent/queue/ConcurrentLinkedQueueUnitTest.java

@@ -19,7 +19,7 @@ import org.junit.FixMethodOrder;
 import org.junit.Test;
 
 @FixMethodOrder
-public class TestConcurrentLinkedQueue {
+public class ConcurrentLinkedQueueUnitTest {
 
     @Test
     public void givenThereIsExistingCollection_WhenAddedIntoQueue_ThenShouldContainElements() {

core-java-modules/core-java-concurrency-collections-2/src/test/java/com/baeldung/concurrent/queue/LinkedBlockingQueueUnitTest.java

@@ -18,7 +18,7 @@ import org.junit.FixMethodOrder;
 import org.junit.Test;
 
 @FixMethodOrder
-public class TestLinkedBlockingQueue {
+public class LinkedBlockingQueueUnitTest {
 
     @Test
     public void givenThereIsExistingCollection_WhenAddedIntoQueue_ThenShouldContainElements() {