Merge branch 'master' into BAEL-3596_Asynchronous_Method_Calls_in_Java

.gitignore

@@ -39,7 +39,6 @@ target/
 spring-openid/src/main/resources/application.properties
 .recommenders/
 /spring-hibernate4/nbproject/
-spring-security-openid/src/main/resources/application.properties
 
 spring-all/*.log
 

README.md

@@ -1,3 +1,4 @@
+**UPDATE**: The price of "Learn Spring Security OAuth" will permanently change on the 11th of December, along with the upcoming OAuth2 material: http://bit.ly/github-lss
 
 The Courses
 ==============================

algorithms-miscellaneous-3/README.md

@@ -15,5 +15,4 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Creating a Triangle with for Loops in Java](https://www.baeldung.com/java-print-triangle)
 - [Efficient Word Frequency Calculator in Java](https://www.baeldung.com/java-word-frequency)
 - [The K-Means Clustering Algorithm in Java](https://www.baeldung.com/java-k-means-clustering-algorithm)
-- [Creating a Custom Annotation in Java](https://www.baeldung.com/java-custom-annotation)
 - More articles: [[<-- prev]](/algorithms-miscellaneous-2) [[next -->]](/algorithms-miscellaneous-4)

algorithms-miscellaneous-5/README.md

@@ -10,4 +10,6 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Find If Two Numbers Are Relatively Prime in Java](https://www.baeldung.com/java-two-relatively-prime-numbers)
 - [Knapsack Problem Implementation in Java](https://www.baeldung.com/java-knapsack)
 - [How to Determine if a Binary Tree is Balanced](https://www.baeldung.com/java-balanced-binary-tree)
+- [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
+- [Overview of Combinatorial Problems in Java](https://www.baeldung.com/java-combinatorial-algorithms)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-4)

algorithms-miscellaneous-5/pom.xml

@@ -34,6 +34,11 @@
             <artifactId>tradukisto</artifactId>
             <version>${tradukisto.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>28.1-jre</version>
+        </dependency>
 
         <dependency>
             <groupId>org.assertj</groupId>

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/Follower.java

@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.greedy;
+
+import lombok.Getter;
+
+public class Follower {
+
+    @Getter String username;
+    @Getter long count;
+    
+    public Follower(String username, long count) {
+        super();
+        this.username = username;
+        this.count = count;
+    }
+    
+    @Override
+    public String toString() {
+        return "User: " + username + ", Followers: " + count + "\n\r" ; 
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/FollowersPath.java

@@ -0,0 +1,44 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FollowersPath {
+
+    private List<Follower> accounts;
+    private long count;
+    
+    public FollowersPath() {
+        super();
+        this.accounts = new ArrayList<>();
+    }
+    
+    public List<Follower> getAccounts() {
+        return accounts;
+    }
+    public long getCount() {
+        return count;
+    }
+    
+    public void addFollower(String username, long count) {
+        accounts.add(new Follower(username, count));
+    }
+    
+    public void addCount(long count) {
+        this.count += count;
+    }
+    
+    @Override
+    public String toString() {
+        String details = "";
+        for(Follower a : accounts) {
+            details+=a.toString() + ", ";
+        }
+        
+        return "Total: " + count + ", \n\r" +
+                " Details: { " + "\n\r" + 
+                details + "\n\r" + 
+                " }";
+    }
+    
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/GreedyAlgorithm.java

@@ -0,0 +1,43 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.List;
+
+public class GreedyAlgorithm {
+
+    int currentLevel = 0;
+    final int maxLevel = 3; 
+    SocialConnector sc;
+    FollowersPath fp;
+    
+    public GreedyAlgorithm(SocialConnector sc) {
+        super();
+        this.sc = sc;
+        this.fp = new FollowersPath();
+    }
+    
+    public long findMostFollowersPath(String account) {
+        long max = 0;
+        SocialUser toFollow = null;
+        
+        List<SocialUser> followers = sc.getFollowers(account);
+        for (SocialUser el : followers) {
+            long followersCount = el.getFollowersCount();
+            if (followersCount > max) {
+                toFollow = el;
+                max = followersCount;
+            }
+        }
+        
+        if (currentLevel < maxLevel - 1) {
+            currentLevel++;
+            max += findMostFollowersPath(toFollow.getUsername());
+            return max;
+        } else {
+            return max;
+        }            
+    }
+    
+    public FollowersPath getFollowers() {
+        return fp;
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/NonGreedyAlgorithm.java

@@ -0,0 +1,43 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.List;
+
+public class NonGreedyAlgorithm {
+
+    int currentLevel = 0;
+    final int maxLevel = 3; 
+    SocialConnector tc;
+    
+    public NonGreedyAlgorithm(SocialConnector tc, int level) {
+        super();
+        this.tc = tc;
+        this.currentLevel = level;
+    }
+      
+    public long findMostFollowersPath(String account) {
+        List<SocialUser> followers = tc.getFollowers(account);
+        long total = currentLevel > 0 ? followers.size() : 0;
+
+        if (currentLevel < maxLevel ) {
+            currentLevel++;
+
+            long[] count = new long[followers.size()];
+            int i = 0;
+            for (SocialUser el : followers) {
+                NonGreedyAlgorithm sub = new NonGreedyAlgorithm(tc, currentLevel);
+                count[i] = sub.findMostFollowersPath(el.getUsername());
+                i++;
+            }
+            
+            long max = 0;
+            for (; i > 0; i--) {
+                if (count[i-1] > max )
+                    max = count[i-1];
+            }
+            
+            return total + max;
+        }
+        
+        return total;
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/SocialConnector.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import lombok.Getter;
+import lombok.Setter;
+
+public class SocialConnector {
+    private boolean isCounterEnabled = true;
+    private int counter = 4;
+    @Getter @Setter List<SocialUser> users;
+    
+    public SocialConnector() {
+        users = new ArrayList<>();
+    }
+    
+    public boolean switchCounter() {
+        this.isCounterEnabled = !this.isCounterEnabled;
+        return this.isCounterEnabled;
+    }
+    
+    public List<SocialUser> getFollowers(String account) {
+        if (counter < 0)
+            throw new IllegalStateException ("API limit reached");
+        else {
+            if(this.isCounterEnabled) counter--;
+            for(SocialUser user : users) {
+                if (user.getUsername().equals(account)) {
+                    return user.getFollowers();
+                }
+            }
+        }
+        return new ArrayList<>();
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/SocialUser.java

@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import lombok.Getter;
+
+public class SocialUser {
+
+    @Getter private String username;
+    @Getter private List<SocialUser> followers;
+
+    public SocialUser(String username) {
+        super();
+        this.username = username;
+        this.followers = new ArrayList<>();
+    }
+    
+    public SocialUser(String username, List<SocialUser> followers) {
+        super();
+        this.username = username;
+        this.followers = followers;
+    }
+    
+    public long getFollowersCount() {
+        return followers.size();
+    }
+    
+    public void addFollowers(List<SocialUser> followers) {
+        this.followers.addAll(followers);
+    }
+    
+    @Override
+    public boolean equals(Object obj) {
+        return ((SocialUser) obj).getUsername().equals(username);
+    }
+    
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/integerstreammedian/MedianOfIntegerStream.java

@@ -0,0 +1,42 @@
+package com.baeldung.algorithms.integerstreammedian;
+
+import java.util.PriorityQueue;
+import java.util.Queue;
+
+import static java.util.Comparator.reverseOrder;
+
+public class MedianOfIntegerStream {
+
+    private Queue<Integer> minHeap, maxHeap;
+
+    MedianOfIntegerStream() {
+        minHeap = new PriorityQueue<>();
+        maxHeap = new PriorityQueue<>(reverseOrder());
+    }
+
+    void add(int num) {
+        if (!minHeap.isEmpty() && num < minHeap.peek()) {
+            maxHeap.offer(num);
+            if (maxHeap.size() > minHeap.size() + 1) {
+                minHeap.offer(maxHeap.poll());
+            }
+        } else {
+            minHeap.offer(num);
+            if (minHeap.size() > maxHeap.size() + 1) {
+                maxHeap.offer(minHeap.poll());
+            }
+        }
+    }
+
+    double getMedian() {
+        int median;
+        if (minHeap.size() < maxHeap.size()) {
+            median = maxHeap.peek();
+        } else if (minHeap.size() > maxHeap.size()) {
+            median = minHeap.peek();
+        } else {
+            median = (minHeap.peek() + maxHeap.peek()) / 2;
+        }
+        return median;
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/integerstreammedian/MedianOfIntegerStream2.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.integerstreammedian;
+
+import java.util.PriorityQueue;
+import java.util.Queue;
+
+import static java.util.Comparator.reverseOrder;
+
+public class MedianOfIntegerStream2 {
+
+    private Queue<Integer> minHeap, maxHeap;
+
+    MedianOfIntegerStream2() {
+        minHeap = new PriorityQueue<>();
+        maxHeap = new PriorityQueue<>(reverseOrder());
+    }
+
+    void add(int num) {
+        if (minHeap.size() == maxHeap.size()) {
+            maxHeap.offer(num);
+            minHeap.offer(maxHeap.poll());
+        } else {
+            minHeap.offer(num);
+            maxHeap.offer(minHeap.poll());
+        }
+    }
+
+    double getMedian() {
+        int median;
+        if (minHeap.size() > maxHeap.size()) {
+            median = minHeap.peek();
+        } else {
+            median = (minHeap.peek() + maxHeap.peek()) / 2;
+        }
+        return median;
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/kruskal/CycleDetector.java

@@ -0,0 +1,72 @@
+package com.baeldung.algorithms.kruskal;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CycleDetector {
+
+    List<DisjointSetInfo> nodes;
+
+    public CycleDetector(int totalNodes) {
+        initDisjointSets(totalNodes);
+    }
+
+    public boolean detectCycle(Integer u, Integer v) {
+        Integer rootU = pathCompressionFind(u);
+        Integer rootV = pathCompressionFind(v);
+        if (rootU.equals(rootV)) {
+            return true;
+        }
+        unionByRank(rootU, rootV);
+        return false;
+    }
+
+    private void initDisjointSets(int totalNodes) {
+        nodes = new ArrayList<>(totalNodes);
+        for (int i = 0; i < totalNodes; i++) {
+            nodes.add(new DisjointSetInfo(i));
+        }
+    }
+
+    private Integer find(Integer node) {
+        Integer parent = nodes.get(node).getParentNode();
+        if (parent.equals(node)) {
+            return node;
+        } else {
+            return find(parent);
+        }
+    }
+
+    private Integer pathCompressionFind(Integer node) {
+        DisjointSetInfo setInfo = nodes.get(node);
+        Integer parent = setInfo.getParentNode();
+        if (parent.equals(node)) {
+            return node;
+        } else {
+            Integer parentNode = find(parent);
+            setInfo.setParentNode(parentNode);
+            return parentNode;
+        }
+    }
+
+    private void union(Integer rootU, Integer rootV) {
+        DisjointSetInfo setInfoU = nodes.get(rootU);
+        setInfoU.setParentNode(rootV);
+    }
+
+    private void unionByRank(int rootU, int rootV) {
+        DisjointSetInfo setInfoU = nodes.get(rootU);
+        DisjointSetInfo setInfoV = nodes.get(rootV);
+        int rankU = setInfoU.getRank();
+        int rankV = setInfoV.getRank();
+        if (rankU < rankV) {
+            setInfoU.setParentNode(rootV);
+        } else {
+            setInfoV.setParentNode(rootU);
+            if (rankU == rankV) {
+                setInfoU.setRank(rankU + 1);
+            }
+        }
+    }
+
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/kruskal/DisjointSetInfo.java

@@ -0,0 +1,28 @@
+package com.baeldung.algorithms.kruskal;
+
+public class DisjointSetInfo {
+
+    private Integer parentNode;
+    private int rank;
+
+    DisjointSetInfo(Integer nodeNumber) {
+        setParentNode(nodeNumber);
+        setRank(1);
+    }
+
+    public Integer getParentNode() {
+        return parentNode;
+    }
+
+    public void setParentNode(Integer parentNode) {
+        this.parentNode = parentNode;
+    }
+
+    public int getRank() {
+        return rank;
+    }
+
+    public void setRank(int rank) {
+        this.rank = rank;
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/kruskal/Kruskal.java

@@ -0,0 +1,53 @@
+package com.baeldung.algorithms.kruskal;
+
+import com.google.common.graph.EndpointPair;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Set;
+
+public class Kruskal {
+
+    public ValueGraph<Integer, Double> minSpanningTree(ValueGraph<Integer, Double> graph) {
+
+        return spanningTree(graph, true);
+    }
+
+    public ValueGraph<Integer, Double> maxSpanningTree(ValueGraph<Integer, Double> graph) {
+        return spanningTree(graph, false);
+    }
+
+    private ValueGraph<Integer, Double> spanningTree(ValueGraph<Integer, Double> graph, boolean minSpanningTree) {
+        Set<EndpointPair<Integer>> edges = graph.edges();
+        List<EndpointPair<Integer>> edgeList = new ArrayList<>(edges);
+
+        if (minSpanningTree) {
+            edgeList.sort(Comparator.comparing(e -> graph.edgeValue(e).get()));
+        } else {
+            edgeList.sort(Collections.reverseOrder(Comparator.comparing(e -> graph.edgeValue(e).get())));
+        }
+
+        int totalNodes = graph.nodes().size();
+        CycleDetector cycleDetector = new CycleDetector(totalNodes);
+        int edgeCount = 0;
+
+        MutableValueGraph<Integer, Double> spanningTree = ValueGraphBuilder.undirected().build();
+        for (EndpointPair<Integer> edge : edgeList) {
+            if (cycleDetector.detectCycle(edge.nodeU(), edge.nodeV())) {
+                continue;
+            }
+            spanningTree.putEdgeValue(edge.nodeU(), edge.nodeV(), graph.edgeValue(edge).get());
+            edgeCount++;
+            if (edgeCount == totalNodes - 1) {
+                break;
+            }
+        }
+        return spanningTree;
+    }
+
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/greedy/GreedyAlgorithmUnitTest.java

@@ -0,0 +1,58 @@
+package com.baeldung.algorithms.greedy;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class GreedyAlgorithmUnitTest {
+
+    private SocialConnector prepareNetwork() {
+        SocialConnector sc = new SocialConnector();
+        SocialUser root = new SocialUser("root");
+        SocialUser child1 = new SocialUser("child1");
+        SocialUser child2 = new SocialUser("child2");
+        SocialUser child3 = new SocialUser("child3");
+        SocialUser child21 = new SocialUser("child21");
+        SocialUser child211 = new SocialUser("child211");
+        SocialUser child2111 = new SocialUser("child2111");
+        SocialUser child31 = new SocialUser("child31");
+        SocialUser child311 = new SocialUser("child311");
+        SocialUser child3111 = new SocialUser("child3111");
+        child211.addFollowers(Arrays.asList(new SocialUser[]{child2111}));
+        child311.addFollowers(Arrays.asList(new SocialUser[]{child3111}));
+        child21.addFollowers(Arrays.asList(new SocialUser[]{child211}));
+        child31.addFollowers(Arrays.asList(new SocialUser[]{child311, 
+          new SocialUser("child312"), new SocialUser("child313"), new SocialUser("child314")}));
+        child1.addFollowers(Arrays.asList(new SocialUser[]{new SocialUser("child11"), new SocialUser("child12")}));
+        child2.addFollowers(Arrays.asList(new SocialUser[]{child21, new SocialUser("child22"), new SocialUser("child23")}));
+        child3.addFollowers(Arrays.asList(new SocialUser[]{child31}));
+        root.addFollowers(Arrays.asList(new SocialUser[]{child1, child2, child3}));
+        sc.setUsers(Arrays.asList(new SocialUser[]{root, child1, child2, child3, child21, child31, child311, child211}));
+        return sc;
+    }
+
+    @Test
+    public void greedyAlgorithmTest() {
+        GreedyAlgorithm ga = new GreedyAlgorithm(prepareNetwork());
+        assertEquals(ga.findMostFollowersPath("root"), 5);
+    }
+
+    @Test
+    public void nongreedyAlgorithmTest() {
+        NonGreedyAlgorithm nga = new NonGreedyAlgorithm(prepareNetwork(), 0);
+        Assertions.assertThrows(IllegalStateException.class, () -> {
+            nga.findMostFollowersPath("root");
+          });
+    }
+
+    @Test
+    public void nongreedyAlgorithmUnboundedTest() {
+        SocialConnector sc = prepareNetwork();
+        sc.switchCounter();
+        NonGreedyAlgorithm nga = new NonGreedyAlgorithm(sc, 0);
+        assertEquals(nga.findMostFollowersPath("root"), 6);
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/integerstreammedian/MedianOfIntegerStreamUnitTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.algorithms.integerstreammedian;
+
+import org.junit.Test;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class MedianOfIntegerStreamUnitTest {
+
+    @Test
+    public void givenStreamOfIntegers_whenAnElementIsRead_thenMedianChangesWithApproach1() {
+        MedianOfIntegerStream mis = new MedianOfIntegerStream();
+        for (Map.Entry<Integer, Double> e : testcaseFixture().entrySet()) {
+            mis.add(e.getKey());
+            assertEquals(e.getValue(), (Double) mis.getMedian());
+        }
+    }
+
+    @Test
+    public void givenStreamOfIntegers_whenAnElementIsRead_thenMedianChangesWithApproach2() {
+        MedianOfIntegerStream2 mis = new MedianOfIntegerStream2();
+        for (Map.Entry<Integer, Double> e : testcaseFixture().entrySet()) {
+            mis.add(e.getKey());
+            assertEquals(e.getValue(), (Double) mis.getMedian());
+        }
+    }
+
+    private Map<Integer, Double> testcaseFixture() {
+        return new LinkedHashMap<Integer, Double>() {{
+            put(1, 1d);
+            put(7, 4d);
+            put(5, 5d);
+            put(8, 6d);
+            put(3, 5d);
+            put(9, 6d);
+            put(4, 5d);
+        }};
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/kruskal/KruskalUnitTest.java

@@ -0,0 +1,67 @@
+package com.baeldung.algorithms.kruskal;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Before;
+import org.junit.Test;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+import com.baeldung.algorithms.kruskal.Kruskal;
+
+public class KruskalUnitTest {
+
+    private MutableValueGraph<Integer, Double> graph;
+
+    @Before
+    public void setup() {
+        graph = ValueGraphBuilder.undirected().build();
+        graph.putEdgeValue(0, 1, 8.0);
+        graph.putEdgeValue(0, 2, 5.0);
+        graph.putEdgeValue(1, 2, 9.0);
+        graph.putEdgeValue(1, 3, 11.0);
+        graph.putEdgeValue(2, 3, 15.0);
+        graph.putEdgeValue(2, 4, 10.0);
+        graph.putEdgeValue(3, 4, 7.0);
+    }
+
+    @Test
+    public void givenGraph_whenMinimumSpanningTree_thenOutputCorrectResult() {
+        final Kruskal kruskal = new Kruskal();
+        ValueGraph<Integer, Double> spanningTree = kruskal.minSpanningTree(graph);
+
+        assertTrue(spanningTree.hasEdgeConnecting(0, 1));
+        assertTrue(spanningTree.hasEdgeConnecting(0, 2));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 4));
+        assertTrue(spanningTree.hasEdgeConnecting(3, 4));
+        assertEquals(graph.edgeValue(0, 1), spanningTree.edgeValue(0, 1));
+        assertEquals(graph.edgeValue(0, 2), spanningTree.edgeValue(0, 2));
+        assertEquals(graph.edgeValue(2, 4), spanningTree.edgeValue(2, 4));
+        assertEquals(graph.edgeValue(3, 4), spanningTree.edgeValue(3, 4));
+
+        assertFalse(spanningTree.hasEdgeConnecting(1, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(1, 3));
+        assertFalse(spanningTree.hasEdgeConnecting(2, 3));
+    }
+
+    @Test
+    public void givenGraph_whenMaximumSpanningTree_thenOutputCorrectResult() {
+        final Kruskal kruskal = new Kruskal();
+        ValueGraph<Integer, Double> spanningTree = kruskal.maxSpanningTree(graph);
+
+        assertTrue(spanningTree.hasEdgeConnecting(0, 1));
+        assertTrue(spanningTree.hasEdgeConnecting(1, 3));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 3));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 4));
+        assertEquals(graph.edgeValue(0, 1), spanningTree.edgeValue(0, 1));
+        assertEquals(graph.edgeValue(1, 3), spanningTree.edgeValue(1, 3));
+        assertEquals(graph.edgeValue(2, 3), spanningTree.edgeValue(2, 3));
+        assertEquals(graph.edgeValue(2, 4), spanningTree.edgeValue(2, 4));
+
+        assertFalse(spanningTree.hasEdgeConnecting(0, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(1, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(3, 4));
+    }
+}

algorithms-searching/README.md

@@ -9,3 +9,4 @@ This module contains articles about searching algorithms.
 - [Breadth-First Search Algorithm in Java](https://www.baeldung.com/java-breadth-first-search)
 - [String Search Algorithms for Large Texts](https://www.baeldung.com/java-full-text-search-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)

algorithms-searching/src/main/java/com/baeldung/algorithms/quadtree/Point.java

@@ -0,0 +1,24 @@
+package com.baeldung.algorithms.quadtree;
+
+public class Point {
+    private float x;
+    private float y;
+
+    public Point(float x, float y) {
+        this.x = x;
+        this.y = y;
+    }
+
+    public float getX() {
+        return x;
+    }
+
+    public float getY() {
+        return y;
+    }
+
+    @Override
+    public String toString() {
+        return "[" + x + " , " + y + "]";
+    }
+}

algorithms-searching/src/main/java/com/baeldung/algorithms/quadtree/QuadTree.java

@@ -0,0 +1,109 @@
+package com.baeldung.algorithms.quadtree;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class QuadTree {
+    private static final int MAX_POINTS = 3;
+    private Region area;
+    private List<Point> points = new ArrayList<>();
+    private List<QuadTree> quadTrees = new ArrayList<>();
+    private StringBuilder searchTraversePath;
+
+    public QuadTree(Region area) {
+        this.area = area;
+    }
+
+    public boolean addPoint(Point point) {
+        if (this.area.containsPoint(point)) {
+            if (this.points.size() < MAX_POINTS) {
+                this.points.add(point);
+                return true;
+            } else {
+                if (this.quadTrees.size() == 0) {
+                    createQuadrants();
+                }
+                return addPointToOneQuadrant(point);
+            }
+        }
+        return false;
+    }
+
+    private boolean addPointToOneQuadrant(Point point) {
+        boolean isPointAdded;
+        for (int i = 0; i < 4; i++) {
+            isPointAdded = this.quadTrees.get(i)
+                .addPoint(point);
+            if (isPointAdded)
+                return true;
+        }
+        return false;
+    }
+
+    private void createQuadrants() {
+        Region region;
+        for (int i = 0; i < 4; i++) {
+            region = this.area.getQuadrant(i);
+            quadTrees.add(new QuadTree(region));
+        }
+    }
+
+    public List<Point> search(Region searchRegion, List<Point> matches, String depthIndicator) {
+        searchTraversePath = new StringBuilder();
+        if (matches == null) {
+            matches = new ArrayList<Point>();
+            searchTraversePath.append(depthIndicator)
+                .append("Search Boundary =")
+                .append(searchRegion)
+                .append("\n");
+        }
+        if (!this.area.doesOverlap(searchRegion)) {
+            return matches;
+        } else {
+            for (Point point : points) {
+                if (searchRegion.containsPoint(point)) {
+                    searchTraversePath.append(depthIndicator)
+                    .append("Found match " + point)
+                    .append("\n");
+                    matches.add(point);
+                }
+            }
+            if (this.quadTrees.size() > 0) {
+                for (int i = 0; i < 4; i++) {
+                    searchTraversePath.append(depthIndicator)
+                        .append("Q")
+                        .append(i)
+                        .append("-->")
+                        .append(quadTrees.get(i).area)
+                        .append("\n");
+                    quadTrees.get(i)
+                        .search(searchRegion, matches, depthIndicator + "\t");
+                    this.searchTraversePath.append(quadTrees.get(i)
+                        .printSearchTraversePath());
+                }
+            }
+        }
+        return matches;
+    }
+
+    public String printTree(String depthIndicator) {
+        String str = "";
+        if (depthIndicator == "") {
+            str += "Root-->" + area.toString() + "\n";
+        }
+
+        for (Point point : points) {
+            str += depthIndicator + point.toString() + "\n";
+        }
+        for (int i = 0; i < quadTrees.size(); i++) {
+            str += depthIndicator + "Q" + String.valueOf(i) + "-->" + quadTrees.get(i).area.toString() + "\n";
+            str += quadTrees.get(i)
+                .printTree(depthIndicator + "\t");
+        }
+        return str;
+    }
+
+    public String printSearchTraversePath() {
+        return searchTraversePath.toString();
+    }
+}

algorithms-searching/src/main/java/com/baeldung/algorithms/quadtree/Region.java

@@ -0,0 +1,85 @@
+package com.baeldung.algorithms.quadtree;
+
+public class Region {
+    private float x1;
+    private float y1;
+    private float x2;
+    private float y2;
+
+    public Region(float x1, float y1, float x2, float y2) {
+        if (x1 >= x2 || y1 >= y2)
+            throw new IllegalArgumentException("(x1,y1) should be lesser than (x2,y2)");
+        this.x1 = x1;
+        this.y1 = y1;
+        this.x2 = x2;
+        this.y2 = y2;
+    }
+
+    public Region getQuadrant(int quadrantIndex) {
+        float quadrantWidth = (this.x2 - this.x1) / 2;
+        float quadrantHeight = (this.y2 - this.y1) / 2;
+
+        // 0=SW, 1=NW, 2=NE, 3=SE
+        switch (quadrantIndex) {
+        case 0:
+            return new Region(x1, y1, x1 + quadrantWidth, y1 + quadrantHeight);
+        case 1:
+            return new Region(x1, y1 + quadrantHeight, x1 + quadrantWidth, y2);
+        case 2:
+            return new Region(x1 + quadrantWidth, y1 + quadrantHeight, x2, y2);
+        case 3:
+            return new Region(x1 + quadrantWidth, y1, x2, y1 + quadrantHeight);
+        }
+        return null;
+    }
+
+    public boolean containsPoint(Point point) {
+        // Consider left and top side to be inclusive for points on border
+        return point.getX() >= this.x1 
+            && point.getX() < this.x2 
+            && point.getY() >= this.y1 
+            && point.getY() < this.y2;
+    }
+
+    public boolean doesOverlap(Region testRegion) {
+        // Is test region completely to left of my region?
+        if (testRegion.getX2() < this.getX1()) {
+            return false;
+        }
+        // Is test region completely to right of my region?
+        if (testRegion.getX1() > this.getX2()) {
+            return false;
+        }
+        // Is test region completely above my region?
+        if (testRegion.getY1() > this.getY2()) {
+            return false;
+        }
+        // Is test region completely below my region?
+        if (testRegion.getY2() < this.getY1()) {
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public String toString() {
+        return "[Region (x1=" + x1 + ", y1=" + y1 + "), (x2=" + x2 + ", y2=" + y2 + ")]";
+    }
+
+    public float getX1() {
+        return x1;
+    }
+
+    public float getY1() {
+        return y1;
+    }
+
+    public float getX2() {
+        return x2;
+    }
+
+    public float getY2() {
+        return y2;
+    }
+
+}

algorithms-searching/src/test/java/com/baeldung/algorithms/quadtree/QuadTreeSearchUnitTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.algorithms.quadtree;
+
+import org.junit.Assert;
+
+import java.util.List;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class QuadTreeSearchUnitTest {
+    
+    private static final Logger LOGGER = LoggerFactory.getLogger(QuadTreeSearchUnitTest.class);
+
+    private static QuadTree quadTree;
+
+    @BeforeClass
+    public static void setUp() {
+        Region area = new Region(0, 0, 400, 400);
+        quadTree = new QuadTree(area);
+
+        float[][] points = new float[][] { { 21, 25 }, { 55, 53 }, { 70, 318 }, { 98, 302 }, 
+            { 49, 229 }, { 135, 229 }, { 224, 292 }, { 206, 321 }, { 197, 258 }, { 245, 238 } };
+
+        for (int i = 0; i < points.length; i++) {
+            Point point = new Point(points[i][0], points[i][1]);
+            quadTree.addPoint(point);
+        }
+        LOGGER.info("\n" + quadTree.printTree(""));
+        LOGGER.info("==============================================");
+    }
+
+    @Test
+    public void givenQuadTree_whenSearchingForRange_thenReturn1MatchingItem() {
+        Region searchArea = new Region(200, 200, 250, 250);
+        List<Point> result = quadTree.search(searchArea, null, "");
+        LOGGER.info(result.toString());
+        LOGGER.info(quadTree.printSearchTraversePath());
+       
+        Assert.assertEquals(1, result.size());
+        Assert.assertArrayEquals(new float[] { 245, 238 }, 
+            new float[]{result.get(0).getX(), result.get(0).getY() }, 0);
+    }
+    
+    @Test
+    public void givenQuadTree_whenSearchingForRange_thenReturn2MatchingItems() {
+        Region searchArea = new Region(0, 0, 100, 100);
+        List<Point> result = quadTree.search(searchArea, null, "");
+        LOGGER.info(result.toString());
+        LOGGER.info(quadTree.printSearchTraversePath());
+        
+        Assert.assertEquals(2, result.size());
+        Assert.assertArrayEquals(new float[] { 21, 25 }, 
+            new float[]{result.get(0).getX(), result.get(0).getY() }, 0);
+        Assert.assertArrayEquals(new float[] { 55, 53 }, 
+            new float[]{result.get(1).getX(), result.get(1).getY() }, 0);
+        
+    }
+}

apache-fop/src/main/webapp/WEB-INF/web.xml

@@ -16,7 +16,7 @@
     </context-param>
     <context-param>
         <param-name>contextConfigLocation</param-name>
-        <param-value>org.baeldung.config</param-value>
+        <param-value>com.baeldung.config</param-value>
     </context-param>
 
     <listener>

apache-fop/src/test/java/com/baeldung/java/ApacheFOPConvertHTMLIntegrationTest.java

@@ -1,4 +1,4 @@
-package org.baeldung.java;
+package com.baeldung.java;
 
 import java.io.BufferedOutputStream;
 import java.io.File;

apache-fop/src/test/java/com/baeldung/java/ApacheFOPHeroldLiveTest.java

@@ -1,4 +1,4 @@
-package org.baeldung.java;
+package com.baeldung.java;
 
 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;

apache-olingo/olingo2/pom.xml

@@ -3,7 +3,7 @@
          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>org.baeldung.examples.olingo2</groupId>
+    <groupId>com.baeldung.examples.olingo2</groupId>
     <artifactId>olingo2</artifactId>
     <name>olingo2</name>
     <description>Sample Olingo 2 Project</description>

apache-olingo/olingo2/src/main/java/com/baeldung/examples/olingo2/CarsODataJPAServiceFactory.java

@@ -1,4 +1,4 @@
-package org.baeldung.examples.olingo2;
+package com.baeldung.examples.olingo2;
 
 import java.util.List;
 import java.util.Map;
@@ -9,10 +9,8 @@ import javax.persistence.EntityManagerFactory;
 import javax.persistence.EntityTransaction;
 import javax.persistence.FlushModeType;
 import javax.persistence.LockModeType;
-import javax.persistence.Persistence;
 import javax.persistence.Query;
 import javax.persistence.StoredProcedureQuery;
-import javax.persistence.SynchronizationType;
 import javax.persistence.TypedQuery;
 import javax.persistence.criteria.CriteriaBuilder;
 import javax.persistence.criteria.CriteriaDelete;
@@ -25,11 +23,8 @@ import org.apache.olingo.odata2.api.processor.ODataContext;
 import org.apache.olingo.odata2.jpa.processor.api.ODataJPAContext;
 import org.apache.olingo.odata2.jpa.processor.api.ODataJPAServiceFactory;
 import org.apache.olingo.odata2.jpa.processor.api.exception.ODataJPARuntimeException;
-import org.baeldung.examples.olingo2.JerseyConfig.EntityManagerFilter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.springframework.orm.jpa.EntityManagerFactoryUtils;
-import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
 import org.springframework.stereotype.Component;
 
 /**
@@ -58,7 +53,7 @@ public class CarsODataJPAServiceFactory extends ODataJPAServiceFactory {
         ODataJPAContext ctx = getODataJPAContext();
         ODataContext octx = ctx.getODataContext();
         HttpServletRequest request = (HttpServletRequest)octx.getParameter(ODataContext.HTTP_SERVLET_REQUEST_OBJECT);
-        EntityManager em = (EntityManager)request.getAttribute(EntityManagerFilter.EM_REQUEST_ATTRIBUTE);
+        EntityManager em = (EntityManager)request.getAttribute(JerseyConfig.EntityManagerFilter.EM_REQUEST_ATTRIBUTE);
                 
         // Here we're passing the EM that was created by the EntityManagerFilter (see JerseyConfig)
         ctx.setEntityManager(new EntityManagerWrapper(em));

apache-olingo/olingo2/src/main/java/com/baeldung/examples/olingo2/JerseyConfig.java

@@ -1,11 +1,10 @@
-    package org.baeldung.examples.olingo2;
+    package com.baeldung.examples.olingo2;
 
 import java.io.IOException;
 
 import javax.persistence.EntityManager;
 import javax.persistence.EntityManagerFactory;
 import javax.persistence.EntityTransaction;
-import javax.servlet.ServletContext;
 import javax.servlet.http.HttpServletRequest;
 import javax.ws.rs.ApplicationPath;
 import javax.ws.rs.Path;

apache-olingo/olingo2/src/main/java/com/baeldung/examples/olingo2/Olingo2SampleApplication.java

@@ -1,8 +1,7 @@
-package org.baeldung.examples.olingo2;
+package com.baeldung.examples.olingo2;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
-import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
 
 @SpringBootApplication

apache-olingo/olingo2/src/main/java/com/baeldung/examples/olingo2/domain/CarMaker.java

@@ -1,4 +1,4 @@
-package org.baeldung.examples.olingo2.domain;
+package com.baeldung.examples.olingo2.domain;
 
 import java.util.List;
 

apache-olingo/olingo2/src/main/java/com/baeldung/examples/olingo2/domain/CarModel.java

@@ -1,4 +1,4 @@
-package org.baeldung.examples.olingo2.domain;
+package com.baeldung.examples.olingo2.domain;
 
 import javax.persistence.Entity;
 import javax.persistence.FetchType;

apache-olingo/olingo2/src/test/java/com/baeldung/examples/olingo2/Olingo2SampleApplicationUnitTest.java

@@ -1,4 +1,4 @@
-package org.baeldung.examples.olingo2;
+package com.baeldung.examples.olingo2;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;

apache-rocketmq/README.md

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

apache-rocketmq/pom.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>apache-rocketmq</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <name>apache-rocketmq</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.rocketmq</groupId>
+            <artifactId>rocketmq-spring-boot-starter</artifactId>
+            <version>2.0.4</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <geode.core>1.6.0</geode.core>
+    </properties>
+</project>

apache-rocketmq/src/main/java/com/baeldung/rocketmq/consumer/CartEventConsumer.java

@@ -0,0 +1,34 @@
+package com.baeldung.rocketmq.consumer;
+
+import com.baeldung.rocketmq.event.CartItemEvent;
+import org.apache.rocketmq.spring.annotation.RocketMQMessageListener;
+import org.apache.rocketmq.spring.core.RocketMQListener;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.stereotype.Service;
+
+@SpringBootApplication
+public class CartEventConsumer {
+
+    public static void main(String[] args) {
+        SpringApplication.run(CartEventConsumer.class, args);
+    }
+
+    @Service
+    @RocketMQMessageListener(topic = "cart-item-add-topic", consumerGroup = "cart-consumer_cart-item-add-topic")
+    public class CardItemAddConsumer implements RocketMQListener<CartItemEvent> {
+        public void onMessage(CartItemEvent addItemEvent) {
+            System.out.println("Adding item: " + addItemEvent);
+            // logic
+        }
+    }
+
+    @Service
+    @RocketMQMessageListener(topic = "cart-item-removed-topic", consumerGroup = "cart-consumer_cart-item-removed-topic")
+    public class CardItemRemoveConsumer implements RocketMQListener<CartItemEvent> {
+        public void onMessage(CartItemEvent removeItemEvent) {
+            System.out.println("Removing item: " + removeItemEvent);
+            // logic
+        }
+    }
+}

apache-rocketmq/src/main/java/com/baeldung/rocketmq/event/CartItemEvent.java

@@ -0,0 +1,32 @@
+package com.baeldung.rocketmq.event;
+
+public class CartItemEvent {
+    private String itemId;
+    private int quantity;
+
+    public CartItemEvent(String itemId, int quantity) {
+        this.itemId = itemId;
+        this.quantity = quantity;
+    }
+
+    public String getItemId() {
+        return itemId;
+    }
+
+    public void setItemId(String itemId) {
+        this.itemId = itemId;
+    }
+
+    public int getQuantity() {
+        return quantity;
+    }
+
+    public void setQuantity(int quantity) {
+        this.quantity = quantity;
+    }
+
+    @Override
+    public String toString() {
+        return "CartItemEvent{" + "itemId='" + itemId + '\'' + ", quantity=" + quantity + '}';
+    }
+}

apache-rocketmq/src/main/java/com/baeldung/rocketmq/producer/CartEventProducer.java

@@ -0,0 +1,26 @@
+package com.baeldung.rocketmq.producer;
+
+
+import com.baeldung.rocketmq.event.CartItemEvent;
+import org.apache.rocketmq.spring.core.RocketMQTemplate;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class CartEventProducer implements CommandLineRunner {
+
+    @Autowired
+    private RocketMQTemplate rocketMQTemplate;
+
+    public static void main(String[] args) {
+        SpringApplication.run(CartEventProducer.class, args);
+    }
+
+    public void run(String... args) throws Exception {
+        rocketMQTemplate.convertAndSend("cart-item-add-topic", new CartItemEvent("bike", 1));
+        rocketMQTemplate.convertAndSend("cart-item-add-topic", new CartItemEvent("computer", 2));
+        rocketMQTemplate.convertAndSend("cart-item-removed-topic", new CartItemEvent("bike", 1));
+    }
+}

apache-rocketmq/src/main/java/com/baeldung/rocketmq/transaction/TransactionListenerImpl.java

@@ -0,0 +1,21 @@
+package com.baeldung.rocketmq.transaction;
+
+import org.apache.rocketmq.spring.annotation.RocketMQTransactionListener;
+import org.apache.rocketmq.spring.core.RocketMQLocalTransactionListener;
+import org.apache.rocketmq.spring.core.RocketMQLocalTransactionState;
+import org.springframework.messaging.Message;
+
+@RocketMQTransactionListener(txProducerGroup = "test-transaction")
+class TransactionListenerImpl implements RocketMQLocalTransactionListener {
+    @Override
+    public RocketMQLocalTransactionState executeLocalTransaction(Message msg, Object arg) {
+        // ... local transaction process, return ROLLBACK, COMMIT or UNKNOWN
+        return RocketMQLocalTransactionState.UNKNOWN;
+    }
+
+    @Override
+    public RocketMQLocalTransactionState checkLocalTransaction(Message msg) {
+        // ... check transaction status and return ROLLBACK, COMMIT or UNKNOWN
+        return RocketMQLocalTransactionState.COMMIT;
+    }
+}

apache-rocketmq/src/main/resources/application.properties

@@ -0,0 +1,9 @@
+rocketmq.name-server=127.0.0.1:9876
+rocketmq.producer.group=my-group
+rocketmq.producer.send-message-timeout=300000
+rocketmq.producer.compress-message-body-threshold=4096
+rocketmq.producer.max-message-size=4194304
+rocketmq.producer.retry-times-when-send-async-failed=0
+rocketmq.producer.retry-next-server=true
+rocketmq.producer.retry-times-when-send-failed=2
+

core-groovy-2/src/main/groovy/com/baeldung/metaprogramming/extension/BasicExtensions.groovy

@@ -2,10 +2,13 @@ package com.baeldung.metaprogramming.extension
 
 import com.baeldung.metaprogramming.Employee
 
+import java.time.LocalDate
+import java.time.Year
+
 class BasicExtensions {
     
     static int getYearOfBirth(Employee self) {
-        return (new Date().getYear() + 1900) - self.age;
+        return Year.now().value - self.age
     }
     
     static String capitalize(String self) {

core-groovy-2/src/test/groovy/com/baeldung/metaprogramming/MetaprogrammingUnitTest.groovy

@@ -1,6 +1,9 @@
 package com.baeldung.metaprogramming
 
-import groovy.time.TimeCategory
+
+import java.time.LocalDate
+import java.time.Period
+import java.time.Year
 
 class MetaprogrammingUnitTest extends GroovyTestCase {
 
@@ -51,14 +54,16 @@ class MetaprogrammingUnitTest extends GroovyTestCase {
 
     void testJavaMetaClass() {
         String.metaClass.capitalize = { String str ->
-            str.substring(0, 1).toUpperCase() + str.substring(1);
+            str.substring(0, 1).toUpperCase() + str.substring(1)
         }
         assert "norman".capitalize() == "Norman"
     }
 
     void testEmployeeExtension() {
-        Employee emp = new Employee(age: 28)
-        assert emp.getYearOfBirth() == 1991
+        def age = 28
+        def expectedYearOfBirth = Year.now() - age
+        Employee emp = new Employee(age: age)
+        assert emp.getYearOfBirth() == expectedYearOfBirth.value
     }
 
     void testJavaClassesExtensions() {
@@ -115,4 +120,4 @@ class MetaprogrammingUnitTest extends GroovyTestCase {
         Employee employee = new Employee(1, "Norman", "Lewis", 28)
         employee.logEmp()
     }
-}
+}

core-java-lambdas/README.md

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

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

@@ -12,3 +12,4 @@ This module contains articles about Java 11 core features
 - [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)
+- [Benchmark JDK Collections vs Eclipse Collections](https://www.baeldung.com/jdk-collections-vs-eclipse-collections)

core-java-modules/core-java-11/src/test/java/com/baeldung/patternreuse/PatternJava11UnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.patternreuse;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.Predicate;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class PatternJava11UnitTest {
+
+    @Test
+    public void givenPreCompiledPattern_whenCallAsMatchPredicate_thenReturnMatchPredicateToMatchesPattern() {
+        List<String> namesToValidate = Arrays.asList("Fabio Silva", "Fabio Luis Silva");
+        Pattern firstLastNamePreCompiledPattern = Pattern.compile("[a-zA-Z]{3,} [a-zA-Z]{3,}");
+
+        Predicate<String> patternAsMatchPredicate = firstLastNamePreCompiledPattern.asMatchPredicate();
+        List<String> validatedNames = namesToValidate.stream()
+                .filter(patternAsMatchPredicate)
+                .collect(Collectors.toList());
+
+        assertTrue(validatedNames.contains("Fabio Silva"));
+        assertFalse(validatedNames.contains("Fabio Luis Silva"));
+    }
+}

core-java-modules/core-java-14/pom.xml

@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>com.baeldung</groupId>
+	<artifactId>core-java-14</artifactId>
+	<version>1.0.0-SNAPSHOT</version>
+	<name>core-java-14</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>
+	</parent>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>${maven-compiler-plugin.version}</version>
+				<configuration>
+					<source>${maven.compiler.source.version}</source>
+					<target>${maven.compiler.target.version}</target>
+					<compilerArgs>
+						<compilerArg>
+							--enable-preview
+						</compilerArg>
+					</compilerArgs>
+				</configuration>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<version>3.0.0-M3</version>
+				<configuration>
+					<argLine>--enable-preview</argLine>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
+	<properties>
+		<maven.compiler.source.version>14</maven.compiler.source.version>
+		<maven.compiler.target.version>14</maven.compiler.target.version>
+	</properties>
+
+</project>

core-java-modules/core-java-14/src/main/java/com/baeldung/serial/MySerialClass.java

@@ -0,0 +1,50 @@
+package com.baeldung.serial;
+
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.ObjectStreamException;
+import java.io.ObjectStreamField;
+import java.io.Serial;
+import java.io.Serializable;
+
+/**
+ * Class showcasing the usage of the Java 14 @Serial annotation.
+ * 
+ * @author Donato Rimenti
+ */
+public class MySerialClass implements Serializable {
+	
+	@Serial
+	private static final ObjectStreamField[] serialPersistentFields = null;
+	
+	@Serial
+	private static final long serialVersionUID = 1;
+
+	@Serial
+	private void writeObject(ObjectOutputStream stream) throws IOException {
+		// ...
+	}
+
+	@Serial
+	private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
+		// ...
+	}
+
+	@Serial
+	private void readObjectNoData() throws ObjectStreamException {
+		// ...
+	}
+
+	@Serial
+	private Object writeReplace() throws ObjectStreamException {
+		// ...
+		return null;
+	}
+
+	@Serial
+	private Object readResolve() throws ObjectStreamException {
+		// ...
+		return null;
+	}
+}

core-java-modules/core-java-arrays-2/pom.xml

@@ -19,6 +19,16 @@
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
+        </dependency>
+		<dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
         </dependency>
         <!-- test scoped -->
         <dependency>
@@ -37,9 +47,34 @@
                 <filtering>true</filtering>
             </resource>
         </resources>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-shade-plugin</artifactId>
+				<version>3.2.0</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>
+		<jmh.version>1.19</jmh.version>
         <!-- util -->
         <commons-lang3.version>3.9</commons-lang3.version>
         <!-- testing -->

core-java-modules/core-java-arrays-2/src/main/java/com/baeldung/arraysort/ArraySortingBenchmark.java

@@ -0,0 +1,72 @@
+package com.baeldung.arraysort;
+
+import java.util.Arrays;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+@BenchmarkMode(Mode.AverageTime)
+@Warmup(iterations = 5)
+@Measurement(iterations = 10)
+@Fork(2)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+public class ArraySortingBenchmark {
+
+    @State(Scope.Benchmark)
+    public static class ArrayContainer {
+
+        @Param({ "1000", "10000", "100000", "1000000" })
+        int arraySize;
+
+        // initial unsorted array
+        int[] unsortedArray;
+        
+        //cloned array to sort
+        int[] arrayToSort;
+
+        @Setup(Level.Trial)
+        public void createUnSortedArray() {
+            unsortedArray = new int[arraySize];
+            for (int i = 0; i < arraySize; i++) {
+                unsortedArray[i] = new Random().nextInt(1000);
+            }
+        }
+
+        @Setup(Level.Invocation)
+        public void createUnSortedArrayCopy() {
+            arrayToSort = unsortedArray.clone();
+        }
+
+        int[] getArrayToSort() {
+            return arrayToSort;
+        }
+    }
+
+    @Benchmark
+    public void benchmark_arrays_parallel_sort(ArrayContainer d, Blackhole b) {
+        int[] arr = d.getArrayToSort();
+        Arrays.parallelSort(arr);
+        b.consume(arr);
+    }
+
+    @Benchmark
+    public void benchmark_arrays_sort(ArrayContainer d, Blackhole b) {
+        int[] arr = d.getArrayToSort();
+        Arrays.sort(arr);
+        b.consume(arr);
+    }
+
+}

core-java-modules/core-java-arrays-2/src/test/java/com/baeldung/arraysort/SortComparisonUnitTest.java

@@ -0,0 +1,185 @@
+package com.baeldung.arraysort;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNotSame;
+
+import java.util.Arrays;
+import java.util.Random;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+
+/**
+ * Time taken by JUnit test cases can be seen in JUnit Runner
+ * @author rchaudhary23
+ *
+ */
+
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class SortComparisonUnitTest {
+
+    private int[] sizeOfArrays = { 1000, 10000, 100000, 1000000 };
+
+    private int[] _1000_elements_array;
+    private int[] _10000_elements_array;
+    private int[] _100000_elements_array;
+    private int[] _1000000_elements_array;
+
+    @Before
+    public void setUp() throws Exception {
+
+        _1000_elements_array = new int[sizeOfArrays[0]];
+        _10000_elements_array = new int[sizeOfArrays[1]];
+        _100000_elements_array = new int[sizeOfArrays[2]];
+        _1000000_elements_array = new int[sizeOfArrays[3]];
+
+        Random random = new Random();
+        for (int i = 0; i < sizeOfArrays[0]; i++) {
+            _1000_elements_array[i] = random.nextInt(sizeOfArrays[0]) + random.nextInt(sizeOfArrays[0]);
+        }
+
+        for (int i = 0; i < sizeOfArrays[1]; i++) {
+            _10000_elements_array[i] = random.nextInt(sizeOfArrays[1]) + random.nextInt(sizeOfArrays[1]);
+        }
+
+        for (int i = 0; i < sizeOfArrays[2]; i++) {
+            _100000_elements_array[i] = random.nextInt(sizeOfArrays[2]) + random.nextInt(sizeOfArrays[2]);
+        }
+
+        for (int i = 0; i < sizeOfArrays[3]; i++) {
+            _1000000_elements_array[i] = random.nextInt(sizeOfArrays[3]) + random.nextInt(sizeOfArrays[3]);
+        }
+
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenUsingArraysSortMethod_thenSortFullArrayInAscendingOrder() {
+
+        int[] array = { 10, 4, 6, 2, 1, 9, 7, 8, 3, 5 };
+        int[] expected = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
+
+        Arrays.sort(array);
+
+        assertArrayEquals(expected, array);
+
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenUsingArraysSortMethodWithRange_thenSortRangeOfArrayInAscendingOrder() {
+        int[] array = { 10, 4, 6, 2, 1, 9, 7, 8, 3, 5 };
+        int[] expected = { 10, 4, 1, 2, 6, 7, 8, 9, 3, 5 };
+
+        Arrays.sort(array, 2, 8);
+
+        assertArrayEquals(expected, array);
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenUsingArraysParallelSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] array = { 10, 4, 6, 2, 1, 9, 7, 8, 3, 5 };
+        int[] expected = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
+
+        Arrays.parallelSort(array);
+
+        assertArrayEquals(expected, array);
+    }
+
+    @Test
+    public void givenArrayOfIntegers_whenUsingArraysParallelSortMethodWithRange_thenSortRangeOfArrayInAscendingOrder() {
+        int[] array = { 10, 4, 6, 2, 1, 9, 7, 8, 3, 5 };
+        int[] expected = { 10, 4, 1, 2, 6, 7, 8, 9, 3, 5 };
+
+        Arrays.parallelSort(array, 2, 8);
+
+        assertArrayEquals(expected, array);
+    }
+
+    @Test
+    public void givenIntegerArrayOf1000Elements_whenUsingArraysSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] sequentialDataSet = Arrays.copyOf(_1000_elements_array, _1000_elements_array.length);
+        Arrays.sort(sequentialDataSet);
+
+        assertNotNull(sequentialDataSet);
+        assertNotSame(Arrays.copyOf(_1000_elements_array, _1000_elements_array.length), sequentialDataSet);
+
+    }
+
+    @Test
+    public void givenIntegerArrayOf1000Elements_whenUsingArraysParallelSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] parallelDataSet = Arrays.copyOf(_1000_elements_array, _1000_elements_array.length);
+        Arrays.parallelSort(parallelDataSet);
+
+        assertNotNull(parallelDataSet);
+        assertNotSame(Arrays.copyOf(_1000_elements_array, _1000_elements_array.length), parallelDataSet);
+
+    }
+
+    @Test
+    public void givenIntegerArrayOf10000Elements_whenUsingArraysSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] sequentialDataSet = Arrays.copyOf(_10000_elements_array, _10000_elements_array.length);
+        Arrays.sort(sequentialDataSet);
+
+        assertNotNull(sequentialDataSet);
+        assertNotSame(Arrays.copyOf(_10000_elements_array, _10000_elements_array.length), sequentialDataSet);
+    }
+
+    @Test
+    public void givenIntegerArrayOf10000Elements_whenUsingArraysParallelSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] parallelDataSet = Arrays.copyOf(_10000_elements_array, _10000_elements_array.length);
+        Arrays.parallelSort(parallelDataSet);
+
+        assertNotNull(parallelDataSet);
+        assertNotSame(Arrays.copyOf(_10000_elements_array, _10000_elements_array.length), parallelDataSet);
+    }
+
+    @Test
+    public void givenIntegerArrayOf100000Elements_whenUsingArraysSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] sequentialDataSet = Arrays.copyOf(_100000_elements_array, _100000_elements_array.length);
+        Arrays.sort(sequentialDataSet);
+
+        assertNotNull(sequentialDataSet);
+        assertNotSame(Arrays.copyOf(_100000_elements_array, _100000_elements_array.length), sequentialDataSet);
+    }
+
+    @Test
+    public void givenIntegerArrayOf100000Elements_whenUsingArraysParallelSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] parallelDataSet = Arrays.copyOf(_100000_elements_array, _100000_elements_array.length);
+        Arrays.parallelSort(parallelDataSet);
+
+        assertNotNull(parallelDataSet);
+        assertNotSame(Arrays.copyOf(_100000_elements_array, _100000_elements_array.length), parallelDataSet);
+    }
+
+    @Test
+    public void givenIntegerArrayOf1000000Elements_whenUsingArraysSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] sequentialDataSet = Arrays.copyOf(_1000000_elements_array, _1000000_elements_array.length);
+        Arrays.sort(sequentialDataSet);
+
+        assertNotNull(sequentialDataSet);
+        assertNotSame(Arrays.copyOf(_1000000_elements_array, _1000000_elements_array.length), sequentialDataSet);
+    }
+
+    @Test
+    public void givenIntegerArrayOf1000000Elements_whenUsingArraysParallelSortMethod_thenSortFullArrayInAscendingOrder() {
+        int[] parallelDataSet = Arrays.copyOf(_1000000_elements_array, _1000000_elements_array.length);
+        Arrays.parallelSort(parallelDataSet);
+
+        assertNotNull(parallelDataSet);
+        assertNotSame(Arrays.copyOf(_1000000_elements_array, _1000000_elements_array.length), parallelDataSet);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        sizeOfArrays = null;
+        _1000_elements_array = null;
+        _10000_elements_array = null;
+        _100000_elements_array = null;
+        _1000000_elements_array = null;
+    }
+}
+
+

core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/duplicatescounter/DuplicatesCounter.java

@@ -24,11 +24,21 @@ public class DuplicatesCounter {
         return resultMap;
     }
 
-    public static <T> Map<T, Long> countByClassicalLoopWithMapCompute(List<T> inputList) {
+    public static <T> Map<T, Long> countByForEachLoopWithGetOrDefault(List<T> inputList) {
         Map<T, Long> resultMap = new HashMap<>();
-        for (T element : inputList) {
-            resultMap.compute(element, (k, v) -> v == null ? 1 : v + 1);
-        }
+        inputList.forEach(e -> resultMap.put(e, resultMap.getOrDefault(e, 0L) + 1L));
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByForEachLoopWithMapCompute(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        inputList.forEach(e -> resultMap.compute(e, (k, v) -> v == null ? 1L : v + 1L));
+        return resultMap;
+    }
+
+    public static <T> Map<T, Long> countByForEachLoopWithMapMerge(List<T> inputList) {
+        Map<T, Long> resultMap = new HashMap<>();
+        inputList.forEach(e -> resultMap.merge(e, 1L, Long::sum));
         return resultMap;
     }
 

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/duplicatescounter/DuplicatesCounterUnitTest.java

@@ -11,7 +11,6 @@ import static org.assertj.core.data.MapEntry.entry;
 
 class DuplicatesCounterUnitTest {
 
-
     private static List<String> INPUT_LIST = Lists.list(
         "expect1",
         "expect2", "expect2",
@@ -24,10 +23,21 @@ class DuplicatesCounterUnitTest {
         verifyResult(result);
     }
 
+    @Test
+    void givenInput_whenCountByForEachLoopWithGetOrDefault_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByForEachLoopWithGetOrDefault(INPUT_LIST);
+        verifyResult(result);
+    }
 
     @Test
-    void givenInput_whenCountByClassicalLoopWithMapCompute_thenGetResultMap() {
-        Map<String, Long> result = DuplicatesCounter.countByClassicalLoopWithMapCompute(INPUT_LIST);
+    void givenInput_whenCountByForEachLoopWithMapCompute_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByForEachLoopWithMapCompute(INPUT_LIST);
+        verifyResult(result);
+    }
+
+    @Test
+    void givenInput_whenCountByForEachLoopWithMapMerge_thenGetResultMap() {
+        Map<String, Long> result = DuplicatesCounter.countByForEachLoopWithMapMerge(INPUT_LIST);
         verifyResult(result);
     }
 

core-java-modules/core-java-date-operations/src/main/java/com/baeldung/date/comparison/DateComparisonUtils.java

@@ -1,8 +1,10 @@
 package com.baeldung.date.comparison;
 
 import java.text.SimpleDateFormat;
+import java.time.Instant;
 import java.time.LocalDate;
 import java.time.ZoneId;
+import java.time.temporal.ChronoUnit;
 import java.util.Calendar;
 import java.util.Date;
 import java.util.TimeZone;
@@ -23,6 +25,14 @@ public class DateComparisonUtils {
         return localDate1.isEqual(localDate2);
     }
 
+    public static boolean isSameDayUsingInstant(Date date1, Date date2) {
+        Instant instant1 = date1.toInstant()
+            .truncatedTo(ChronoUnit.DAYS);
+        Instant instant2 = date2.toInstant()
+            .truncatedTo(ChronoUnit.DAYS);
+        return instant1.equals(instant2);
+    }
+
     public static boolean isSameDayUsingSimpleDateFormat(Date date1, Date date2) {
         SimpleDateFormat fmt = new SimpleDateFormat("yyyyMMdd");
         return fmt.format(date1)

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/date/comparison/DateComparisonUtilsUnitTest.java

@@ -1,13 +1,13 @@
 package com.baeldung.date.comparison;
 
-import org.junit.Test;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.util.Date;
 
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
+import org.junit.Test;
 
 public class DateComparisonUtilsUnitTest {
 
@@ -23,6 +23,7 @@ public class DateComparisonUtilsUnitTest {
     @Test
     public void givenDatesWithDifferentTime_whenIsSameDay_thenReturnsTrue() {
         assertTrue(DateComparisonUtils.isSameDayUsingLocalDate(day1Morning, day1Evening));
+        assertTrue(DateComparisonUtils.isSameDayUsingInstant(day1Morning, day1Evening));
         assertTrue(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Morning, day1Evening));
         assertTrue(DateComparisonUtils.isSameDayUsingCalendar(day1Morning, day1Evening));
         assertTrue(DateComparisonUtils.isSameDayUsingApacheCommons(day1Morning, day1Evening));
@@ -35,6 +36,9 @@ public class DateComparisonUtilsUnitTest {
         assertFalse(DateComparisonUtils.isSameDayUsingLocalDate(day1Morning, day2Morning));
         assertFalse(DateComparisonUtils.isSameDayUsingLocalDate(day1Evening, day2Morning));
 
+        assertFalse(DateComparisonUtils.isSameDayUsingInstant(day1Morning, day2Morning));
+        assertFalse(DateComparisonUtils.isSameDayUsingInstant(day1Evening, day2Morning));
+
         assertFalse(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Morning, day2Morning));
         assertFalse(DateComparisonUtils.isSameDayUsingSimpleDateFormat(day1Evening, day2Morning));
 

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/DateUtilsUnitTest.java

@@ -9,12 +9,6 @@ import static org.junit.Assert.assertEquals;
 
 public class DateUtilsUnitTest {
 
-    @Test
-    public void givenTimeMillis_thenDateIsReturned() {
-        Date now = DateUtils.getNow();
-        assertEquals(DateUtils.getDate(now.getTime()), now);
-    }
-
     @Test
     public void givenDateAndPattern_thenDateIsCorrectlyReturned() throws ParseException {
         long milliseconds = new Date(2020 - 1900, 0, 1).getTime();

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/sql/DateUtilsUnitTest.java

@@ -9,11 +9,6 @@ import org.junit.Test;
 
 public class DateUtilsUnitTest {
 
-    @Test
-    public void givenCurrentDate_thenTodayIsReturned() {
-        assertEquals(DateUtils.getNow().toLocalDate(), LocalDate.now());
-    }
-
     @Test(expected = IllegalArgumentException.class)
     public void givenDateAsString_whenPatternIsNotRespected_thenExceptionIsThrown() {
         DateUtils.getDate("2020 01 01");

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/datetime/sql/TimestampUtilsUnitTest.java

@@ -1,22 +1,13 @@
 package com.baeldung.datetime.sql;
 
-import static org.junit.Assert.assertEquals;
-
 import org.junit.Test;
 
-import com.baeldung.datetime.sql.TimestampUtils;
-
 import java.text.ParseException;
-import java.util.Date;
+
+import static org.junit.Assert.assertEquals;
 
 public class TimestampUtilsUnitTest {
 
-    @Test
-    public void givenCurrentTimestamp_thenNowIsReturned() {
-        assertEquals(TimestampUtils.getNow()
-            .getTime(), new Date().getTime());
-    }
-
     @Test(expected = IllegalArgumentException.class)
     public void givenTimestampAsString_whenPatternIsNotRespected_thenExceptionIsThrown() {
         TimestampUtils.getTimestamp("2020/01/01 10:11-12");

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/jvmtimezone/ModifyDefaultTimezoneUnitTest.java

@@ -1,9 +1,8 @@
-package com.baeldung.timezone;
+package com.baeldung.jvmtimezone;
 
 import org.junit.Test;
 
 import java.util.Calendar;
-import java.util.Date;
 import java.util.TimeZone;
 
 import static org.junit.Assert.assertEquals;
@@ -13,9 +12,7 @@ public class ModifyDefaultTimezoneUnitTest {
     @Test
     public void givenDefaultTimezoneSet_thenDateTimezoneIsCorrect() {
         TimeZone.setDefault(TimeZone.getTimeZone("Portugal"));
-        Date date = new Date();
         Calendar calendar = Calendar.getInstance();
-        calendar.setTime(date);
         assertEquals(calendar.getTimeZone(), TimeZone.getTimeZone("Portugal"));
     }
 

core-java-modules/core-java-date-operations/src/test/java/com/baeldung/jvmtimezone/ModifyTimezonePropertyUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.timezone;
+package com.baeldung.jvmtimezone;
 
 import org.junit.After;
 import org.junit.Before;
@@ -14,7 +14,7 @@ public class ModifyTimezonePropertyUnitTest {
 
     @Before
     public void setup() {
-        System.setProperty("user.timezone", "IST");
+        System.setProperty("user.timezone", "Asia/Kolkata");
         TimeZone.setDefault(null);
     }
 
@@ -25,10 +25,8 @@ public class ModifyTimezonePropertyUnitTest {
 
     @Test
     public void givenTimezonePropertySet_thenDateTimezoneIsCorrect() {
-        Date date = new Date();
         Calendar calendar = Calendar.getInstance();
-        calendar.setTime(date);
-        assertEquals(calendar.getTimeZone(), TimeZone.getTimeZone("IST"));
+        assertEquals(calendar.getTimeZone(), TimeZone.getTimeZone("Asia/Kolkata"));
     }
 
 }

core-java-modules/core-java-exceptions-2/src/main/java/com/baeldung/exceptions/CatchingThrowable.java

@@ -0,0 +1,38 @@
+package com.baeldung.exceptions;
+
+import java.util.Set;
+import java.util.UUID;
+
+public class CatchingThrowable  {
+
+    class CapacityException extends Exception {
+        CapacityException(String message) {
+            super(message);
+        }
+    }
+
+    class StorageAPI {
+
+        public void addIDsToStorage(int capacity, Set<String> storage) throws CapacityException {
+            if (capacity < 1) {
+                throw new CapacityException("Capacity of less than 1 is not allowed");
+            }
+            int count = 0;
+            while (count < capacity) {
+                storage.add(UUID.randomUUID().toString());
+                count++;
+            }
+        }
+
+        // other methods go here ...
+    }
+
+    public void add(StorageAPI api, int capacity, Set<String> storage) {
+        try {
+            api.addIDsToStorage(capacity, storage);
+        } catch (Throwable throwable) {
+            // do something here
+        }
+    }
+
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/finallykeyword/FinallyExample.java

@@ -0,0 +1,14 @@
+package com.baeldung.finallykeyword;
+
+public class FinallyExample {
+
+    public void printCount(String count) {
+        try {
+            System.out.println("The count is " + Integer.parseInt(count));
+        } catch (NumberFormatException e) {
+            System.out.println("No count");
+        } finally {
+            System.out.println("In finally");
+        }
+    }
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/finallykeyword/FinallyExecutedCases.java

@@ -0,0 +1,53 @@
+package com.baeldung.finallykeyword;
+
+public class FinallyExecutedCases {
+
+    public void noExceptionFinally() {
+        try {
+            System.out.println("Inside try");
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+
+    public void unhandledException() throws Exception {
+        try {
+            System.out.println("Inside try");
+            throw new Exception();
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+
+    public void handledException() {
+        try {
+            System.out.println("Inside try");
+            throw new Exception();
+        } catch (Exception e) {
+            System.out.println("Inside catch");
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+
+    public String returnFromTry() {
+        try {
+            System.out.println("Inside try");
+            return "from try";
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+
+    public String returnFromCatch() {
+        try {
+            System.out.println("Inside try");
+            throw new Exception();
+        } catch (Exception e) {
+            System.out.println("Inside catch");
+            return "from catch";
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/finallykeyword/FinallyNotExecutedCases.java

@@ -0,0 +1,54 @@
+package com.baeldung.finallykeyword;
+
+public class FinallyNotExecutedCases {
+
+    public void callingSystemExit() {
+        try {
+            System.out.println("Inside try");
+            System.exit(1);
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+
+    public void callingRuntimeHalt() {
+        try {
+            System.out.println("Inside try");
+            Runtime.getRuntime()
+                .halt(1);
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+
+    public void infiniteLoop() {
+        try {
+            System.out.println("Inside try");
+            while (true) {
+            }
+        } finally {
+            System.out.println("Inside finally");
+        }
+    }
+
+    public void daemonThread() throws InterruptedException {
+        Runnable runnable = () -> {
+            try {
+                System.out.println("Inside try");
+            } finally {
+                try {
+                    Thread.sleep(1000);
+                    System.out.println("Inside finally");
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+            }
+        };
+        Thread regular = new Thread(runnable);
+        Thread daemon = new Thread(runnable);
+        daemon.setDaemon(true);
+        regular.start();
+        Thread.sleep(300);
+        daemon.start();
+    }
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/finallykeyword/PitfallsWhenUsingFinally.java

@@ -0,0 +1,33 @@
+package com.baeldung.finallykeyword;
+
+public class PitfallsWhenUsingFinally {
+
+    public String disregardsUnCaughtException() {
+        try {
+            System.out.println("Inside try");
+            throw new RuntimeException();
+        } finally {
+            System.out.println("Inside finally");
+            return "from finally";
+        }
+    }
+
+    public String ignoringOtherReturns() {
+        try {
+            System.out.println("Inside try");
+            return "from try";
+        } finally {
+            System.out.println("Inside finally");
+            return "from finally";
+        }
+    }
+
+    public String throwsException() {
+        try {
+            System.out.println("Inside try");
+            return "from try";
+        } finally {
+            throw new RuntimeException();
+        }
+    }
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/methodmultiplereturnvalues/Coordinates.java

@@ -0,0 +1,49 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+public class Coordinates {
+
+    private double longitude;
+    private double latitude;
+    private String placeName;
+    
+    public Coordinates() {}
+    
+    public Coordinates(double longitude, double latitude, String placeName) {
+        this.longitude = longitude;
+        this.latitude = latitude;
+        this.placeName = placeName;
+    }
+
+    public double calculateDistance(Coordinates c) {
+        
+        double s1 = Math.abs(this.longitude - c.longitude);
+        double s2 = Math.abs(this.latitude - c.latitude);
+        
+        return Math.hypot(s1, s2);
+    }
+    
+    public double getLongitude() {
+        return longitude;
+    }
+
+    public void setLongitude(double longitude) {
+        this.longitude = longitude;
+    }
+
+    public double getLatitude() {
+        return latitude;
+    }
+
+    public void setLatitude(double latitude) {
+        this.latitude = latitude;
+    }
+
+    public String getPlaceName() {
+        return placeName;
+    }
+
+    public void setPlaceName(String placeName) {
+        this.placeName = placeName;
+    }
+    
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingArrays.java

@@ -0,0 +1,27 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+class MultipleReturnValuesUsingArrays {
+
+    
+    static double[] getCoordinatesDoubleArray() {
+        
+        double[] coordinates = new double[2];
+
+        coordinates[0] = 10;
+        coordinates[1] = 12.5;
+        
+        return coordinates;
+    }
+
+    
+    static Number[] getCoordinatesNumberArray() {
+        
+        Number[] coordinates = new Number[2];
+
+        coordinates[0] = 10; //Integer
+        coordinates[1] = 12.5; //Double
+        
+        return coordinates;
+    }
+
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingCollections.java

@@ -0,0 +1,30 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+class MultipleReturnValuesUsingCollections {
+
+    static List<Number> getCoordinatesList() {
+
+        List<Number> coordinates = new ArrayList<>();
+
+        coordinates.add(10);
+        coordinates.add(12.5);
+
+        return coordinates;
+    }
+
+    static Map<String, Number> getCoordinatesMap() {
+
+        Map<String, Number> coordinates = new HashMap<>();
+        
+        coordinates.put("longitude", 10);
+        coordinates.put("latitude", 12.5);
+
+        return coordinates;
+    }
+
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingContainer.java

@@ -0,0 +1,14 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+class MultipleReturnValuesUsingContainer {
+
+    static Coordinates getCoordinates() {
+        
+        double longitude = 10;
+        double latitude = 12.5;
+        String placeName = "home";
+        
+        return new Coordinates(longitude, latitude, placeName);
+    }
+    
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingTuples.java

@@ -0,0 +1,17 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+import java.util.List;
+
+class MultipleReturnValuesUsingTuples {
+
+    static Tuple2<Coordinates, Double> getMostDistantPoint(List<Coordinates> coordinatesList,
+                                                           Coordinates target) {
+
+        return coordinatesList.stream()
+            .map(coor -> new Tuple2<>(coor, coor.calculateDistance(target)))
+            .max((d1, d2) -> Double.compare(d1.getSecond(), d2.getSecond()))
+            .get();
+
+    }
+
+}

core-java-modules/core-java-lang-2/src/main/java/com/baeldung/methodmultiplereturnvalues/Tuple2.java

@@ -0,0 +1,31 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+public class Tuple2 <K, V> {
+
+    private K first;
+    private V second;
+    
+    public Tuple2() {}
+    
+    public Tuple2(K first, V second) {
+        this.first = first;
+        this.second = second;
+    }
+
+    public K getFirst() {
+        return first;
+    }
+    
+    public V getSecond() {
+        return second;
+    }
+
+    public void setFirst(K first) {
+        this.first = first;
+    }
+
+    public void setSecond(V second) {
+        this.second = second;
+    }
+
+}

core-java-modules/core-java-lang-2/src/test/java/com/baeldung/finallykeyword/PitfallsWhenUsingFinallyUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.finallykeyword;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class PitfallsWhenUsingFinallyUnitTest {
+
+    PitfallsWhenUsingFinally instance = new PitfallsWhenUsingFinally();
+
+    @Test
+    public void testIgnoresException() {
+        String result = instance.disregardsUnCaughtException();
+        assertEquals("from finally", result);
+    }
+
+    @Test
+    public void testIgnoresOtherReturns() {
+        String result = instance.ignoringOtherReturns();
+        assertEquals("from finally", result);
+    }
+
+    @Test(expected = RuntimeException.class)
+    public void testThrowsException() {
+        instance.throwsException();
+    }
+}

core-java-modules/core-java-lang-2/src/test/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingArraysUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
+
+class MultipleReturnValuesUsingArraysUnitTest {
+
+    @Test
+    void whenUsingArrayOfDoubles_thenMultipleDoubleFieldsAreReturned() {
+
+        double[] coordinates = MultipleReturnValuesUsingArrays.getCoordinatesDoubleArray();
+        assertEquals(10, coordinates[0]);
+        assertEquals(12.5, coordinates[1]);
+    }
+
+    @Test
+    void whenUsingArrayOfNumbers_thenMultipleNumberFieldsAreReturned() {
+        
+        Number[] coordinates = MultipleReturnValuesUsingArrays.getCoordinatesNumberArray();
+        assertEquals(10, coordinates[0]);
+        assertEquals(12.5, coordinates[1]);
+
+    }
+    
+}

core-java-modules/core-java-lang-2/src/test/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingCollectionsUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class MultipleReturnValuesUsingCollectionsUnitTest {
+
+    @Test
+    void whenUsingList_thenMultipleFieldsAreReturned() {
+        
+        List<Number> coordinates = MultipleReturnValuesUsingCollections.getCoordinatesList();
+        assertEquals(Integer.valueOf(10), coordinates.get(0));
+        assertEquals(Double.valueOf(12.5), coordinates.get(1));
+    }
+    
+    @Test
+    void whenUsingMap_thenMultipleFieldsAreReturned() {
+        
+        Map<String, Number> coordinates = MultipleReturnValuesUsingCollections.getCoordinatesMap();
+        assertEquals(Integer.valueOf(10), coordinates.get("longitude"));
+        assertEquals(Double.valueOf(12.5), coordinates.get("latitude"));
+    }
+}

core-java-modules/core-java-lang-2/src/test/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingContainerUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
+
+class MultipleReturnValuesUsingContainerUnitTest {
+
+    @Test
+    void whenUsingContainerClass_thenMultipleFieldsAreReturned() {
+        
+        Coordinates coordinates = MultipleReturnValuesUsingContainer.getCoordinates();
+        
+        assertEquals(10, coordinates.getLongitude());
+        assertEquals(12.5, coordinates.getLatitude());
+        assertEquals("home", coordinates.getPlaceName());
+    }
+}

core-java-modules/core-java-lang-2/src/test/java/com/baeldung/methodmultiplereturnvalues/MultipleReturnValuesUsingTuplesUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.methodmultiplereturnvalues;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+class MultipleReturnValuesUsingTuplesUnitTest {
+
+    @Test
+    void whenUsingTuple_thenMultipleFieldsAreReturned() {
+        
+        List<Coordinates> coordinatesList = new ArrayList<>();
+        coordinatesList.add(new Coordinates(1, 1, "home"));
+        coordinatesList.add(new Coordinates(2, 2, "school"));
+        coordinatesList.add(new Coordinates(3, 3, "hotel"));
+        
+        Coordinates target = new Coordinates(5, 5, "gym");
+        
+        Tuple2<Coordinates, Double> mostDistantPoint = MultipleReturnValuesUsingTuples.getMostDistantPoint(coordinatesList, target);
+        
+        assertEquals(1, mostDistantPoint.getFirst().getLongitude());
+        assertEquals(1, mostDistantPoint.getFirst().getLatitude());
+        assertEquals("home", mostDistantPoint.getFirst().getPlaceName());
+        assertEquals(5.66, BigDecimal.valueOf(mostDistantPoint.getSecond()).setScale(2, RoundingMode.HALF_UP).doubleValue());
+        
+    }
+    
+}

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

@@ -7,3 +7,5 @@
 - [Java 8 Unsigned Arithmetic Support](https://www.baeldung.com/java-unsigned-arithmetic)
 - [How to Separate Double into Integer and Decimal Parts](https://www.baeldung.com/java-separate-double-into-integer-decimal-parts)
 - [The strictfp Keyword in Java](https://www.baeldung.com/java-strictfp)
+- [Basic Calculator in Java](https://www.baeldung.com/java-basic-calculator)
+- [Overflow and Underflow in Java](https://www.baeldung.com/java-overflow-underflow)

core-java-modules/core-java-lang-math/src/main/java/com/baeldung/powerset/PowerSetUtility.java

@@ -0,0 +1,320 @@
+package com.baeldung.powerset;
+
+import com.google.common.collect.Sets;
+
+import javax.annotation.Nullable;
+import java.util.AbstractSet;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Set;
+
+public class PowerSetUtility<T> {
+
+    private Map<T, Integer> map = new HashMap<>();
+    private List<T> reverseMap = new ArrayList<>();
+
+    //Lazy Load PowerSet class
+    private static class PowerSet<E> extends AbstractSet<Set<E>> {
+        private Map<E, Integer> map = new HashMap<>();
+        private List<E> reverseMap = new ArrayList<>();
+        private Set<E> set;
+
+        public PowerSet(Set<E> set) {
+            this.set = set;
+            initializeMap();
+        }
+
+        abstract class ListIterator<K> implements Iterator<K> {
+
+            protected int position = 0;
+            private int size;
+
+            public ListIterator(int size) {
+                this.size = size;
+            }
+
+            @Override
+            public boolean hasNext() {
+                return position < size;
+            }
+        }
+
+        static class Subset<E> extends AbstractSet<E> {
+            private Map<E, Integer> map;
+            private List<E> reverseMap;
+            private int mask;
+
+            public Subset(Map<E, Integer> map, List<E> reverseMap, int mask) {
+                this.map = map;
+                this.reverseMap = reverseMap;
+                this.mask = mask;
+            }
+
+            @Override
+            public Iterator<E> iterator() {
+                return new Iterator<E>() {
+                    int remainingSetBits = mask;
+
+                    @Override
+                    public boolean hasNext() {
+                        return remainingSetBits != 0;
+                    }
+
+                    @Override
+                    public E next() {
+                        int index = Integer.numberOfTrailingZeros(remainingSetBits);
+                        if (index == 32) {
+                            throw new NoSuchElementException();
+                        }
+                        remainingSetBits &= ~(1 << index);
+                        return reverseMap.get(index);
+                    }
+                };
+            }
+
+            @Override
+            public int size() {
+                return Integer.bitCount(mask);
+            }
+
+            @Override
+            public boolean contains(@Nullable Object o) {
+                Integer index = map.get(o);
+                return index != null && (mask & (1 << index)) != 0;
+            }
+        }
+
+        @Override
+        public Iterator<Set<E>> iterator() {
+            return new ListIterator<Set<E>>(this.size()) {
+                @Override
+                public Set<E> next() {
+                    return new Subset<>(map, reverseMap, position++);
+                }
+            };
+        }
+
+        @Override
+        public int size() {
+            return (1 << this.set.size());
+        }
+
+        @Override
+        public boolean contains(@Nullable Object obj) {
+            if (obj instanceof Set) {
+                Set<?> set = (Set<?>) obj;
+                return reverseMap.containsAll(set);
+            }
+            return false;
+        }
+
+        @Override
+        public boolean equals(@Nullable Object obj) {
+            if (obj instanceof PowerSet) {
+                PowerSet<?> that = (PowerSet<?>) obj;
+                return set.equals(that.set);//Set equals check to have the same element regardless of the order of the items
+            }
+            return super.equals(obj);
+        }
+
+
+        private void initializeMap() {
+            int mapId = 0;
+            for (E c : this.set) {
+                map.put(c, mapId++);
+                reverseMap.add(c);
+            }
+        }
+    }
+
+    public Set<Set<T>> lazyLoadPowerSet(Set<T> set) {
+        return new PowerSet<>(set);
+    }
+
+    public Set<Set<T>> recursivePowerSet(Set<T> set) {
+        if (set.isEmpty()) {
+            Set<Set<T>> ret = new HashSet<>();
+            ret.add(set);
+            return ret;
+        }
+
+        T element = set.iterator().next();
+        Set<T> subSetWithoutElement = getSubSetWithoutElement(set, element);
+        Set<Set<T>> powerSetSubSetWithoutElement = recursivePowerSet(subSetWithoutElement);
+
+        Set<Set<T>> powerSetSubSetWithElement = addElementToAll(powerSetSubSetWithoutElement, element);
+
+        Set<Set<T>> powerSet = new HashSet<>();
+        powerSet.addAll(powerSetSubSetWithoutElement);
+        powerSet.addAll(powerSetSubSetWithElement);
+        return powerSet;
+    }
+
+    public Set<Set<T>> recursivePowerSetIndexRepresentation(Collection<T> set) {
+        initializeMap(set);
+        Set<Set<Integer>> powerSetIndices = recursivePowerSetIndexRepresentation(0, set.size());
+        return unMapIndex(powerSetIndices);
+    }
+
+    private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithReverseLexicographicalOrder(int n) {
+        List<List<Boolean>> powerSet = new ArrayList<>();
+        for (int i = 0; i < (1 << n); i++) {
+            List<Boolean> subset = new ArrayList<>(n);
+            for (int j = 0; j < n; j++)
+                subset.add(((1 << j) & i) > 0);
+            powerSet.add(subset);
+        }
+        return powerSet;
+    }
+
+    private List<List<Boolean>> iterativePowerSetByLoopOverNumbersWithGrayCodeOrder(int n) {
+        List<List<Boolean>> powerSet = new ArrayList<>();
+        for (int i = 0; i < (1 << n); i++) {
+            List<Boolean> subset = new ArrayList<>(n);
+            for (int j = 0; j < n; j++) {
+                int grayEquivalent = i ^ (i >> 1);
+                subset.add(((1 << j) & grayEquivalent) > 0);
+            }
+            powerSet.add(subset);
+        }
+        return powerSet;
+    }
+
+    public Set<Set<T>> recursivePowerSetBinaryRepresentation(Collection<T> set) {
+        initializeMap(set);
+        Set<List<Boolean>> powerSetBoolean = recursivePowerSetBinaryRepresentation(0, set.size());
+        return unMapBinary(powerSetBoolean);
+    }
+
+    public List<List<T>> iterativePowerSetByLoopOverNumbers(Set<T> set) {
+        initializeMap(set);
+                List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithReverseLexicographicalOrder(set.size());
+        return unMapListBinary(sets);
+    }
+
+    public List<List<T>> iterativePowerSetByLoopOverNumbersMinimalChange(Set<T> set) {
+        initializeMap(set);
+        List<List<Boolean>> sets = iterativePowerSetByLoopOverNumbersWithGrayCodeOrder(set.size());
+        return unMapListBinary(sets);
+    }
+
+    public static int getRankInLexicographicalOrder(List<Boolean> subset) {
+        int rank = 0;
+        for (int i = 0; i < subset.size(); i++)
+            if (subset.get(i))
+                rank += (1 << (subset.size() - i - 1));
+        return rank;
+    }
+
+    public static List<Boolean> getSubsetForRankInLexicographicalOrder(int rank, int sizeOfSet) {
+        Boolean[] subset = new Boolean[sizeOfSet];
+        for(int j = 0; j < sizeOfSet; j++) {
+            subset[sizeOfSet - j - 1] = ((rank & (1 << j)) > 0);
+        }
+        return Arrays.asList(subset);
+    }
+
+    private Set<Set<Integer>> recursivePowerSetIndexRepresentation(int idx, int n) {
+        if (idx == n) {
+            Set<Set<Integer>> empty = new HashSet<>();
+            empty.add(new HashSet<>());
+            return empty;
+        }
+        Set<Set<Integer>> powerSetSubset = recursivePowerSetIndexRepresentation(idx + 1, n);
+        Set<Set<Integer>> powerSet = new HashSet<>(powerSetSubset);
+        for (Set<Integer> s : powerSetSubset) {
+            HashSet<Integer> subSetIdxInclusive = new HashSet<>(s);
+            subSetIdxInclusive.add(idx);
+            powerSet.add(subSetIdxInclusive);
+        }
+        return powerSet;
+    }
+
+    private Set<List<Boolean>> recursivePowerSetBinaryRepresentation(int idx, int n) {
+        if (idx == n) {
+            Set<List<Boolean>> powerSetOfEmptySet = new HashSet<>();
+            powerSetOfEmptySet.add(Arrays.asList(new Boolean[n]));
+            return powerSetOfEmptySet;
+        }
+        Set<List<Boolean>> powerSetSubset = recursivePowerSetBinaryRepresentation(idx + 1, n);
+        Set<List<Boolean>> powerSet = new HashSet<>();
+        for (List<Boolean> s : powerSetSubset) {
+            List<Boolean> subSetIdxExclusive = new ArrayList<>(s);
+            subSetIdxExclusive.set(idx, false);
+            powerSet.add(subSetIdxExclusive);
+            List<Boolean> subSetIdxInclusive = new ArrayList<>(s);
+            subSetIdxInclusive.set(idx, true);
+            powerSet.add(subSetIdxInclusive);
+        }
+        return powerSet;
+    }
+
+    private void initializeMap(Collection<T> collection) {
+        int mapId = 0;
+        for (T c : collection) {
+            map.put(c, mapId++);
+            reverseMap.add(c);
+        }
+    }
+
+    private Set<Set<T>> unMapIndex(Set<Set<Integer>> sets) {
+        Set<Set<T>> ret = new HashSet<>();
+        for (Set<Integer> s : sets) {
+            HashSet<T> subset = new HashSet<>();
+            for (Integer i : s)
+                subset.add(reverseMap.get(i));
+            ret.add(subset);
+        }
+        return ret;
+    }
+
+    private Set<Set<T>> unMapBinary(Collection<List<Boolean>> sets) {
+        Set<Set<T>> ret = new HashSet<>();
+        for (List<Boolean> s : sets) {
+            HashSet<T> subset = new HashSet<>();
+            for (int i = 0; i < s.size(); i++)
+                if (s.get(i))
+                    subset.add(reverseMap.get(i));
+            ret.add(subset);
+        }
+        return ret;
+    }
+
+    private List<List<T>> unMapListBinary(Collection<List<Boolean>> sets) {
+        List<List<T>> ret = new ArrayList<>();
+        for (List<Boolean> s : sets) {
+            List<T> subset = new ArrayList<>();
+            for (int i = 0; i < s.size(); i++)
+                if (s.get(i))
+                    subset.add(reverseMap.get(i));
+            ret.add(subset);
+        }
+        return ret;
+    }
+
+    private Set<Set<T>> addElementToAll(Set<Set<T>> powerSetSubSetWithoutElement, T element) {
+        Set<Set<T>> powerSetSubSetWithElement = new HashSet<>();
+        for (Set<T> subsetWithoutElement : powerSetSubSetWithoutElement) {
+            Set<T> subsetWithElement = new HashSet<>(subsetWithoutElement);
+            subsetWithElement.add(element);
+            powerSetSubSetWithElement.add(subsetWithElement);
+        }
+        return powerSetSubSetWithElement;
+    }
+
+    private Set<T> getSubSetWithoutElement(Set<T> set, T element) {
+        Set<T> subsetWithoutElement = new HashSet<>();
+        for (T s : set) {
+            if (!s.equals(element))
+                subsetWithoutElement.add(s);
+        }
+        return subsetWithoutElement;
+    }
+}

core-java-modules/core-java-lang-math/src/test/java/com/baeldung/powerset/PowerSetUtilityUnitTest.java

@@ -0,0 +1,225 @@
+package com.baeldung.powerset;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.hamcrest.collection.IsCollectionWithSize;
+import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+import java.util.Set;
+
+public class PowerSetUtilityUnitTest {
+
+    @Test
+    public void givenSet_WhenGuavaLibraryGeneratePowerSet_ThenItContainsAllSubsets() {
+        ImmutableSet<String> set = ImmutableSet.of("APPLE", "ORANGE", "MANGO");
+        Set<Set<String>> powerSet = Sets.powerSet(set);
+        Assertions.assertEquals((1 << set.size()), powerSet.size());
+        MatcherAssert.assertThat(powerSet, Matchers.containsInAnyOrder(
+          ImmutableSet.of(),
+          ImmutableSet.of("APPLE"),
+          ImmutableSet.of("ORANGE"),
+          ImmutableSet.of("APPLE", "ORANGE"),
+          ImmutableSet.of("MANGO"),
+          ImmutableSet.of("APPLE", "MANGO"),
+          ImmutableSet.of("ORANGE", "MANGO"),
+          ImmutableSet.of("APPLE", "ORANGE", "MANGO")
+        ));
+    }
+
+    @Test
+    public void givenSet_WhenPowerSetIsLazyLoadGenerated_ThenItContainsAllSubsets() {
+        Set<String> set = RandomSetOfStringGenerator.generateRandomSet();
+        Set<Set<String>> powerSet = new PowerSetUtility<String>().lazyLoadPowerSet(set);
+
+        //To make sure that the size of power set is (2 power n)
+        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << set.size())));
+        //To make sure that number of occurrence of each element is (2 power n-1)
+        Map<String, Integer> counter = new HashMap<>();
+        for (Set<String> subset : powerSet) {
+            for (String name : subset) {
+                int num = counter.getOrDefault(name, 0);
+                counter.put(name, num + 1);
+            }
+        }
+        counter.forEach((k, v) -> Assertions.assertEquals((1 << (set.size() - 1)), v.intValue()));
+    }
+
+    @Test
+    public void givenSet_WhenPowerSetIsCalculated_ThenItContainsAllSubsets() {
+        Set<String> set = RandomSetOfStringGenerator.generateRandomSet();
+
+        Set<Set<String>> powerSet = new PowerSetUtility<String>().recursivePowerSet(set);
+
+        //To make sure that the size of power set is (2 power n)
+        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << set.size())));
+        //To make sure that number of occurrence of each element is (2 power n-1)
+        Map<String, Integer> counter = new HashMap<>();
+        for (Set<String> subset : powerSet) {
+            for (String name : subset) {
+                int num = counter.getOrDefault(name, 0);
+                counter.put(name, num + 1);
+            }
+        }
+        counter.forEach((k, v) -> Assertions.assertEquals((1 << (set.size() - 1)), v.intValue()));
+    }
+
+    @Test
+    public void givenSet_WhenPowerSetIsCalculatedRecursiveByIndexRepresentation_ThenItContainsAllSubsets() {
+        Set<String> set = RandomSetOfStringGenerator.generateRandomSet();
+
+        Set<Set<String>> powerSet = new PowerSetUtility<String>().recursivePowerSetIndexRepresentation(set);
+
+        //To make sure that the size of power set is (2 power n)
+        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << set.size())));
+        //To make sure that number of occurrence of each element is (2 power n-1)
+        Map<String, Integer> counter = new HashMap<>();
+        for (Set<String> subset : powerSet) {
+            for (String name : subset) {
+                int num = counter.getOrDefault(name, 0);
+                counter.put(name, num + 1);
+            }
+        }
+        counter.forEach((k, v) -> Assertions.assertEquals((1 << (set.size() - 1)), v.intValue()));
+    }
+
+    @Test
+    public void givenSet_WhenPowerSetIsCalculatedRecursiveByBinaryRepresentation_ThenItContainsAllSubsets() {
+        Set<String> set = RandomSetOfStringGenerator.generateRandomSet();
+
+        Set<Set<String>> powerSet = new PowerSetUtility<String>().recursivePowerSetBinaryRepresentation(set);
+
+        //To make sure that the size of power set is (2 power n)
+        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << set.size())));
+        //To make sure that number of occurrence of each element is (2 power n-1)
+        Map<String, Integer> counter = new HashMap<>();
+        for (Set<String> subset : powerSet) {
+            for (String name : subset) {
+                int num = counter.getOrDefault(name, 0);
+                counter.put(name, num + 1);
+            }
+        }
+        counter.forEach((k, v) -> Assertions.assertEquals((1 << (set.size() - 1)), v.intValue()));
+    }
+
+    @Test
+    public void givenSet_WhenPowerSetIsCalculatedIterativePowerSetByLoopOverNumbers_ThenItContainsAllSubsets() {
+        Set<String> set = RandomSetOfStringGenerator.generateRandomSet();
+
+        List<List<String>> powerSet = new PowerSetUtility<String>().iterativePowerSetByLoopOverNumbers(set);
+
+        //To make sure that the size of power set is (2 power n)
+        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << set.size())));
+        //To make sure that number of occurrence of each element is (2 power n-1)
+        Map<String, Integer> counter = new HashMap<>();
+        for (List<String> subset : powerSet) {
+            for (String name : subset) {
+                int num = counter.getOrDefault(name, 0);
+                counter.put(name, num + 1);
+            }
+        }
+        counter.forEach((k, v) -> Assertions.assertEquals((1 << (set.size() - 1)), v.intValue()));
+        //To make sure that one subset is not generated twice
+        Assertions.assertEquals(powerSet.size(), new HashSet<>(powerSet).size());
+        //To make sure that each element in each subset is occurred once
+        for (List<String> subset : powerSet) {
+            Assertions.assertEquals(subset.size(), new HashSet<>(subset).size());
+        }
+    }
+
+    @Test
+    public void givenSet_WhenPowerSetIsCalculatedIterativePowerSetByLoopOverNumbersMinimalChange_ThenItContainsAllSubsetsInGrayOrder() {
+
+        Set<String> set = RandomSetOfStringGenerator.generateRandomSet();
+        List<List<String>> powerSet = new PowerSetUtility<String>().iterativePowerSetByLoopOverNumbersMinimalChange(set);
+
+        //To make sure that the size of power set is (2 power n)
+        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << set.size())));
+        //To make sure that number of occurrence of each element is (2 power n-1)
+        Map<String, Integer> counter = new HashMap<>();
+        for (List<String> subset : powerSet) {
+            for (String name : subset) {
+                int num = counter.getOrDefault(name, 0);
+                counter.put(name, num + 1);
+            }
+        }
+        counter.forEach((k, v) -> Assertions.assertEquals((1 << (set.size() - 1)), v.intValue()));
+        //To make sure that one subset is not generated twice
+        Assertions.assertEquals(powerSet.size(), new HashSet<>(powerSet).size());
+        //To make sure that each element in each subset is occurred once
+        for (List<String> subset : powerSet) {
+            Assertions.assertEquals(subset.size(), new HashSet<>(subset).size());
+        }
+        //To make sure that difference of consecutive subsets is exactly 1
+        for(int i=1; i<powerSet.size(); i++) {
+            int diff = 0;
+            for (String s : powerSet.get(i - 1))
+                if (!powerSet.get(i).contains(s))
+                    diff++;
+            for (String s : powerSet.get(i))
+                if (!powerSet.get(i - 1).contains(s))
+                    diff++;
+            Assertions.assertEquals(1, diff);
+        }
+    }
+
+    @Test
+    public void givenSubset_WhenPowerSetIsInLexicographicalOrder_ReturnCorrectRank() {
+        int n = new Random().nextInt(5) + 5; //a number in [5, 10)
+        for(int i = 0; i < ( 1 << n); i++) {
+            Boolean[] subset = new Boolean[n];
+            for(int j=0; j < n; j++) {
+                subset[n - j - 1] = ((i & (1 << j)) > 0);
+            }
+            Assertions.assertEquals(i, PowerSetUtility.getRankInLexicographicalOrder(Arrays.asList(subset)));
+        }
+    }
+
+    @Test
+    public void givenRanking_WhenPowerSetIsInLexicographicalOrder_ReturnTheSubset() {
+        int n = new Random().nextInt(5) + 5; //a number in [5, 10)
+        List<List<Boolean>> powerSet = new ArrayList<>();
+        for(int i = 0; i < (1 << n); i++) {
+            powerSet.add(PowerSetUtility.getSubsetForRankInLexicographicalOrder(i, n));
+        }
+        //To make sure that the size of power set is (2 power n)
+        MatcherAssert.assertThat(powerSet, IsCollectionWithSize.hasSize((1 << n)));
+        //To make sure that number of occurrence of each index is (2 power n-1)
+        Map<Integer, Integer> counter = new HashMap<>();
+        for (List<Boolean> subset : powerSet) {
+            for (int i = 0; i < subset.size(); i++) {
+                if(subset.get(i)) {
+                    int num = counter.getOrDefault(i, 0);
+                    counter.put(i, num + 1);
+                }
+            }
+        }
+        counter.forEach((k, v) -> Assertions.assertEquals((1 << (n - 1)), v.intValue()));
+        //To make sure that one subset is not generated twice
+        Assertions.assertEquals(powerSet.size(), new HashSet<>(powerSet).size());
+    }
+
+    static class RandomSetOfStringGenerator {
+        private static List<String> fruits = Arrays.asList("Apples", "Avocados", "Banana", "Blueberry", "Cherry", "Clementine", "Cucumber", "Date", "Fig",
+          "Grapefruit"/*, "Grape", "Kiwi", "Lemon", "Mango", "Mulberry", "Melon", "Nectarine", "Olive", "Orange"*/);
+
+        static Set<String> generateRandomSet() {
+            Set<String> set = new HashSet<>();
+            Random random = new Random();
+            int size = random.nextInt(fruits.size());
+            while (set.size() != size) {
+                set.add(fruits.get(random.nextInt(fruits.size())));
+            }
+            return set;
+        }
+    }
+}

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

@@ -11,4 +11,5 @@ This module contains articles about Java operators
 - [Java Compound Operators](https://www.baeldung.com/java-compound-operators)
 - [The XOR Operator in Java](https://www.baeldung.com/java-xor-operator)
 - [Java Bitwise Operators](https://www.baeldung.com/java-bitwise-operators)
+- [Bitwise & vs Logical && Operators](https://www.baeldung.com/bitwise-vs-logical-operators/)
 

core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/andoperators/BitwiseAndLogicalANDOperatorsUnitTest.java

@@ -0,0 +1,71 @@
+package com.baeldung.andoperators;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.Assert.*;
+
+public class BitwiseAndLogicalANDOperatorsUnitTest {
+
+    @Test
+    public void givenTwoTrueBooleans_whenBitwiseAndOperator_thenTrue() {
+        boolean trueBool = true;
+        boolean anotherTrueBool = true;
+        boolean trueANDTrue = trueBool & anotherTrueBool;
+        assertTrue(trueANDTrue);
+    }
+
+    @Test
+    public void givenOneFalseAndOneTrueBooleans_whenBitwiseAndOperator_thenFalse() {
+        boolean trueBool = true;
+        boolean falseBool = false;
+        boolean trueANDFalse = trueBool & falseBool;
+        assertFalse(trueANDFalse);
+    }
+
+    @Test
+    public void givenTwoFalseBooleans_whenBitwiseAndOperator_thenFalse() {
+        boolean falseBool = false;
+        boolean anotherFalseBool = false;
+        boolean falseANDFalse = falseBool & anotherFalseBool;
+        assertFalse(falseANDFalse);
+    }
+
+    @Test
+    public void givenTwoIntegers_whenBitwiseAndOperator_thenNewDecimalNumber() {
+        int six = 6;
+        int five = 5;
+        int shouldBeFour = six & five;
+        assertEquals(4, shouldBeFour);
+    }
+
+    @Test
+    public void givenTwoTrueBooleans_whenLogicalAndOperator_thenTrue() {
+        boolean trueBool = true;
+        boolean anotherTrueBool = true;
+        boolean trueANDTrue = trueBool && anotherTrueBool;
+        assertTrue(trueANDTrue);
+    }
+
+    @Test
+    public void givenOneFalseAndOneTrueBooleans_whenLogicalAndOperator_thenFalse() {
+        boolean trueBool = true;
+        boolean falseBool = false;
+        boolean trueANDFalse = trueBool && falseBool;
+        assertFalse(trueANDFalse);
+    }
+
+    @Test
+    public void givenTwoFalseBooleans_whenLogicalAndOperator_thenFalse() {
+        boolean falseBool = false;
+        boolean anotherFalseBool = false;
+        boolean falseANDFalse = falseBool && anotherFalseBool;
+        assertFalse(falseANDFalse);
+    }
+
+    @Test
+    public void givenTwoFalseExpressions_whenLogicalAndOperator_thenShortCircuitFalse() {
+        boolean shortCircuitResult = (2<1) && (4<5);
+        assertFalse(shortCircuitResult);
+    }
+
+}

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/operators/notoperator/NotOperator.java

@@ -0,0 +1,99 @@
+package com.baeldung.core.operators.notoperator;
+
+/**
+ * Examples used in the article `Using the Not Operator in If Conditions in Java`.
+ */
+public class NotOperator {
+
+    public static void ifElseStatementExample() {
+        boolean isValid = true;
+
+        if (isValid) {
+            System.out.println("Valid");
+        } else {
+            System.out.println("Invalid");
+        }
+    }
+
+    public static void checkIsValidIsFalseWithEmptyIfBlock() {
+        boolean isValid = true;
+
+        if (isValid) {
+
+        } else {
+            System.out.println("Invalid");
+        }
+    }
+
+    public static void checkIsValidIsFalseWithJustTheIfBlock() {
+        boolean isValid = true;
+
+        if (isValid == false) {
+            System.out.println("Invalid");
+        }
+    }
+
+    public static void checkIsValidIsFalseWithTheNotOperator() {
+        boolean isValid = true;
+
+        if (!isValid) {
+            System.out.println("Invalid");
+        }
+    }
+
+    public static void notOperatorWithBooleanValueAsOperand() {
+        System.out.println(!true);   // prints false
+        System.out.println(!false);  // prints true
+        System.out.println(!!false); // prints false
+    }
+
+    public static void applyNotOperatorToAnExpression_example1() {
+        int count = 2;
+
+        System.out.println(!(count > 2));  // prints true
+        System.out.println(!(count <= 2)); // prints false
+    }
+
+    public static void applyNotOperatorToAnExpression_LogicalOperators() {
+        boolean x = true;
+        boolean y = false;
+
+        System.out.println(!(x && y));  // prints true
+        System.out.println(!(x || y));  // prints false
+    }
+
+    public static void precedence_example() {
+        boolean x = true;
+        boolean y = false;
+
+        System.out.println(!x && y);   // prints false
+        System.out.println(!(x && y)); // prints true
+    }
+
+    public static void pitfalls_ComplexConditionsExample() {
+        int count = 9;
+        int total = 100;
+
+        if (!(count >= 10 || total >= 1000)) {
+            System.out.println("Some more work to do");
+        }
+    }
+
+    public static void pitfalls_simplifyComplexConditionsByReversingLogicExample() {
+        int count = 9;
+        int total = 100;
+
+        if (count < 10 && total < 1000) {
+            System.out.println("Some more work to do");
+        }
+    }
+
+    public static void exitEarlyExample() {
+        boolean isValid = false;
+
+        if(!isValid) {
+            throw new IllegalArgumentException("Invalid input");
+        }
+        // Code to execute when isValid == true goes here
+    }
+}

core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/CombiningUnitTest.java

@@ -0,0 +1,57 @@
+package com.baeldung.branchprediction;
+
+import java.util.stream.LongStream;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class CombiningUnitTest {
+    private static final Logger LOG = LoggerFactory.getLogger(CombiningUnitTest.class);
+
+    public static final int TOP = 10000000;
+    public static final double FRACTION = 0.1;
+
+    @Test
+    public void combined() {
+        long[] first = LongStream.range(0, TOP)
+            .map(n -> Math.random() < FRACTION ? 0 : n)
+            .toArray();
+        long[] second = LongStream.range(0, TOP)
+            .map(n -> Math.random() < FRACTION ? 0 : n)
+            .toArray();
+
+        long count = 0;
+        long start = System.currentTimeMillis();
+        for (int i = 0; i < TOP; i++) {
+            if (first[i] * second[i] != 0) {
+                ++count;
+            }
+        }
+        long end = System.currentTimeMillis();
+
+        LOG.info("Counted {}/{} numbers using combined mode in {}ms", count, TOP, end - start);
+
+    }
+
+    @Test
+    public void separate() {
+        long[] first = LongStream.range(0, TOP)
+            .map(n -> Math.random() < FRACTION ? 0 : n)
+            .toArray();
+        long[] second = LongStream.range(0, TOP)
+            .map(n -> Math.random() < FRACTION ? 0 : n)
+            .toArray();
+
+        long count = 0;
+        long start = System.currentTimeMillis();
+        for (int i = 0; i < TOP; i++) {
+            if (first[i] != 0 && second[i] != 0) {
+                ++count;
+            }
+        }
+        long end = System.currentTimeMillis();
+
+        LOG.info("Counted {}/{} numbers using separate mode in {}ms", count, TOP, end - start);
+    }
+}

core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/IfUnitTest.java

@@ -0,0 +1,92 @@
+package com.baeldung.branchprediction;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.LongStream;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class IfUnitTest {
+    private static final Logger LOG = LoggerFactory.getLogger(IfUnitTest.class);
+
+    public static final int TOP = 10000000;
+
+    @Test
+    public void majorBranchSorted() {
+        test(TOP, 0.9, false);
+    }
+
+    @Test
+    public void minorBranchSorted() {
+        test(TOP, 0.1, false);
+    }
+
+    @Test
+    public void equalBranchSorted() {
+        test(TOP, 0.5, false);
+    }
+
+    @Test
+    public void allBranchSorted() {
+        test(TOP, 1, false);
+    }
+
+    @Test
+    public void noneBranchSorted() {
+        test(TOP, 0, false);
+    }
+
+    @Test
+    public void majorBranchShuffled() {
+        test(TOP, 0.9, true);
+    }
+
+    @Test
+    public void minorBranchShuffled() {
+        test(TOP, 0.1, true);
+    }
+
+    @Test
+    public void equalBranchShuffled() {
+        test(TOP, 0.5, true);
+    }
+
+    @Test
+    public void allBranchShuffled() {
+        test(TOP, 1, true);
+    }
+
+    @Test
+    public void noneBranchShuffled() {
+        test(TOP, 0, true);
+    }
+
+    private void test(long top, double cutoffPercentage, boolean shuffle) {
+        List<Long> numbers = LongStream.range(0, top)
+            .boxed()
+            .collect(Collectors.toList());
+        if (shuffle) {
+            Collections.shuffle(numbers);
+        }
+
+        long cutoff = (long)(top * cutoffPercentage);
+        long low = 0;
+        long high = 0;
+
+        long start = System.currentTimeMillis();
+        for (Long number : numbers) {
+            if (number < cutoff) {
+                ++low;
+            } else {
+                ++high;
+            }
+        }
+        long end = System.currentTimeMillis();
+
+        LOG.info("Counted {}/{} {} numbers in {}ms", low, high, shuffle ? "shuffled" : "sorted", end - start);
+
+    }
+}

core-java-modules/core-java-perf/src/test/java/com/baeldung/branchprediction/SortingUnitTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.branchprediction;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.LongStream;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class SortingUnitTest {
+    private static final Logger LOG = LoggerFactory.getLogger(SortingUnitTest.class);
+    public static final int BIG = 10000000;
+    public static final int SMALL = 100000;
+
+    @Test
+    public void sortedBig() {
+        test(BIG, false);
+    }
+
+    @Test
+    public void shuffledBig() {
+        test(BIG, true);
+    }
+
+    @Test
+    public void sortedSmall() {
+        test(SMALL, false);
+    }
+
+    @Test
+    public void shuffledSmall() {
+        test(SMALL, true);
+    }
+
+    private void test(long top, boolean shuffle) {
+        List<Long> numbers = LongStream.range(0, top)
+            .boxed()
+            .collect(Collectors.toList());
+
+        if (shuffle) {
+            Collections.shuffle(numbers);
+        }
+
+        long cutoff = top / 2;
+        long count = 0;
+
+        long start = System.currentTimeMillis();
+        for (Long number : numbers) {
+            if (number < cutoff) {
+                ++count;
+            }
+        }
+        long end = System.currentTimeMillis();
+
+        LOG.info("Counted {}/{} {} numbers in {}ms",
+            count, top, shuffle ? "shuffled" : "sorted", end - start);
+    }
+}

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

@@ -1,3 +0,0 @@
-### Relevant Articles:
-
-- [Intro to the Java SecurityManager](https://www.baeldung.com/java-security-manager)

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

@@ -1,16 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
-    <artifactId>core-java-security-manager</artifactId>
-    <version>0.1.0-SNAPSHOT</version>
-    <name>core-java-security-manager</name>
-    <packaging>jar</packaging>
-
-    <parent>
-        <groupId>com.baeldung.core-java-modules</groupId>
-        <artifactId>core-java-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-    </parent>
-
-</project>

core-java-modules/core-java-security-manager/src/test/java/com/baeldung/security/manager/SecurityManagerUnitTest.java

@@ -1,35 +0,0 @@
-package com.baeldung.security.manager;
-
-import org.junit.Test;
-
-import java.net.URL;
-import java.security.AccessControlException;
-import java.util.concurrent.Callable;
-
-public class SecurityManagerUnitTest {
-
-    @Test(expected = AccessControlException.class)
-    public void whenSecurityManagerIsActive_thenNetworkIsNotAccessibleByDefault() throws Exception {
-        doTest(() -> {
-            new URL("http://www.google.com").openConnection().connect();
-            return null;
-        });
-    }
-
-    @Test(expected = AccessControlException.class)
-    public void whenUnauthorizedClassTriesToAccessProtectedOperation_thenAnExceptionIsThrown() throws Exception {
-        doTest(() -> {
-            new Service().operation();
-            return null;
-        });
-    }
-
-    private void doTest(Callable<Void> action) throws Exception {
-        System.setSecurityManager(new SecurityManager());
-        try {
-            action.call();
-        } finally {
-            System.setSecurityManager(null);
-        }
-    }
-}

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

@@ -15,4 +15,5 @@ This module contains articles about core Java Security
 - [The Java SecureRandom Class](https://www.baeldung.com/java-secure-random)
 - [An Introduction to Java SASL](https://www.baeldung.com/java-sasl)
 - [A Guide to Java GSS API](https://www.baeldung.com/java-gss)
+- [Intro to the Java SecurityManager](https://www.baeldung.com/java-security-manager)
 

core-java-modules/core-java-security/src/main/java/com/baeldung/securitymanager/CustomPermission.java

@@ -1,4 +1,4 @@
-package com.baeldung.security.manager;
+package com.baeldung.securitymanager;
 
 import java.security.BasicPermission;
 

core-java-modules/core-java-security/src/main/java/com/baeldung/securitymanager/Service.java

@@ -1,4 +1,4 @@
-package com.baeldung.security.manager;
+package com.baeldung.securitymanager;
 
 public class Service {
 

core-java-modules/core-java-security/src/test/java/com/baeldung/java/md5/JavaMD5UnitTest.java

@@ -1,4 +1,4 @@
-package org.baeldung.java.md5;
+package com.baeldung.java.md5;
 
 import static org.assertj.core.api.Assertions.assertThat;
 

core-java-modules/core-java-security/src/test/java/com/baeldung/securitymanager/SecurityManagerUnitTest.java

@@ -0,0 +1,35 @@
+package com.baeldung.securitymanager;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.net.URL;
+import java.security.AccessControlException;
+
+public class SecurityManagerUnitTest {
+
+    private static final String TESTING_SECURITY_POLICY = "file:src/test/resources/testing.policy";
+
+    @Before
+    public void setUp() {
+        System.setProperty("java.security.policy", TESTING_SECURITY_POLICY);
+        System.setSecurityManager(new SecurityManager());
+    }
+
+    @After
+    public void tearDown() {
+        System.setSecurityManager(null);
+    }
+
+    @Test(expected = AccessControlException.class)
+    public void whenSecurityManagerIsActive_thenNetworkIsNotAccessibleByDefault() throws IOException {
+        new URL("http://www.google.com").openConnection().connect();
+    }
+
+    @Test(expected = AccessControlException.class)
+    public void whenUnauthorizedClassTriesToAccessProtectedOperation_thenAnExceptionIsThrown() {
+        new Service().operation();
+    }
+}

core-java-modules/core-java-security/src/test/resources/testing.policy

@@ -0,0 +1,5 @@
+grant {
+        // This is for testing purposes only.
+        // It allows us to properly reset the security manager after the unit test completes.
+        permission java.lang.RuntimePermission "setSecurityManager";
+};

core-java-modules/core-java-strings/src/test/java/com/baeldung/randomstrings/RandomStringsUnitTest.java

@@ -1,72 +1,103 @@
-package com.baeldung.randomstrings;
-
-import org.apache.commons.lang3.RandomStringUtils;
-import org.junit.Test;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.nio.charset.Charset;
-import java.util.Random;
-
-public class RandomStringsUnitTest {
-
-    private static final Logger LOG = LoggerFactory.getLogger(RandomStringsUnitTest.class);
-
-    @Test
-    public void givenUsingPlainJava_whenGeneratingRandomStringUnbounded_thenCorrect() {
-        final byte[] array = new byte[7]; // length is bounded by 7
-        new Random().nextBytes(array);
-        final String generatedString = new String(array, Charset.forName("UTF-8"));
-
-        LOG.debug(generatedString);
-    }
-
-    @Test
-    public void givenUsingPlainJava_whenGeneratingRandomStringBounded_thenCorrect() {
-        final int leftLimit = 97; // letter 'a'
-        final int rightLimit = 122; // letter 'z'
-        final int targetStringLength = 10;
-        final Random random = new Random();
-        final StringBuilder buffer = new StringBuilder(targetStringLength);
-
-        for (int i = 0; i < targetStringLength; i++) {
-            final int randomLimitedInt = leftLimit + (int) (random.nextFloat() * (rightLimit - leftLimit + 1));
-            buffer.append((char) randomLimitedInt);
-        }
-        final String generatedString = buffer.toString();
-
-        LOG.debug(generatedString);
-    }
-
-    @Test
-    public void givenUsingApache_whenGeneratingRandomString_thenCorrect() {
-        final String generatedString = RandomStringUtils.random(10);
-
-        LOG.debug(generatedString);
-    }
-
-    @Test
-    public void givenUsingApache_whenGeneratingRandomAlphabeticString_thenCorrect() {
-        final String generatedString = RandomStringUtils.randomAlphabetic(10);
-
-        LOG.debug(generatedString);
-    }
-
-    @Test
-    public void givenUsingApache_whenGeneratingRandomAlphanumericString_thenCorrect() {
-        final String generatedString = RandomStringUtils.randomAlphanumeric(10);
-
-        LOG.debug(generatedString);
-    }
-
-    @Test
-    public void givenUsingApache_whenGeneratingRandomStringBounded_thenCorrect() {
-        final int length = 10;
-        final boolean useLetters = true;
-        final boolean useNumbers = false;
-        final String generatedString = RandomStringUtils.random(length, useLetters, useNumbers);
-
-        LOG.debug(generatedString);
-    }
-
-}
+package com.baeldung.randomstrings;
+
+import org.apache.commons.lang3.RandomStringUtils;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.nio.charset.Charset;
+import java.util.Random;
+
+public class RandomStringsUnitTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(RandomStringsUnitTest.class);
+
+    @Test
+    public void givenUsingPlainJava_whenGeneratingRandomStringUnbounded_thenCorrect() {
+        byte[] array = new byte[7]; // length is bounded by 7
+        new Random().nextBytes(array);
+        String generatedString = new String(array, Charset.forName("UTF-8"));
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingPlainJava_whenGeneratingRandomStringBounded_thenCorrect() {
+        int leftLimit = 97; // letter 'a'
+        int rightLimit = 122; // letter 'z'
+        int targetStringLength = 10;
+        Random random = new Random();
+        StringBuilder buffer = new StringBuilder(targetStringLength);
+
+        for (int i = 0; i < targetStringLength; i++) {
+            int randomLimitedInt = leftLimit + (int) (random.nextFloat() * (rightLimit - leftLimit + 1));
+            buffer.append((char) randomLimitedInt);
+        }
+        String generatedString = buffer.toString();
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingJava8_whenGeneratingRandomAlphabeticString_thenCorrect() {
+        int leftLimit = 97; // letter 'a'
+        int rightLimit = 122; // letter 'z'
+        int targetStringLength = 10;
+        Random random = new Random();
+
+        String generatedString = random.ints(leftLimit, rightLimit + 1)
+            .limit(targetStringLength)
+            .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
+            .toString();
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingJava8_whenGeneratingRandomAlphanumericString_thenCorrect() {
+        int leftLimit = 48; // numeral '0'
+        int rightLimit = 122; // letter 'z'
+        int targetStringLength = 10;
+        Random random = new Random();
+
+        String generatedString = random.ints(leftLimit, rightLimit + 1)
+            .filter(i -> (i <= 57 || i >= 65) && (i <= 90 || i >= 97))
+            .limit(targetStringLength)
+            .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
+            .toString();
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomString_thenCorrect() {
+        String generatedString = RandomStringUtils.random(10);
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomAlphabeticString_thenCorrect() {
+        String generatedString = RandomStringUtils.randomAlphabetic(10);
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomAlphanumericString_thenCorrect() {
+        String generatedString = RandomStringUtils.randomAlphanumeric(10);
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomStringBounded_thenCorrect() {
+        int length = 10;
+        boolean useLetters = true;
+        boolean useNumbers = false;
+        String generatedString = RandomStringUtils.random(length, useLetters, useNumbers);
+
+        LOG.debug(generatedString);
+    }
+
+}