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

 Conflicts:

	spring-websockets/src/main/resources/public/index.html

.gitignore

@@ -73,8 +73,6 @@ ninja/devDb.mv.db
 **/out-tsc
 **/nbproject/
 **/nb-configuration.xml
-core-scala/.cache-main
-core-scala/.cache-tests
 
 
 persistence-modules/hibernate5/transaction.log
@@ -87,7 +85,9 @@ transaction.log
 *-shell.log
 
 apache-cxf/cxf-aegis/baeldung.xml
-apache-fop/src/test/resources/input.xml
-apache-fop/src/test/resources/output_herold.pdf
-apache-fop/src/test/resources/output_html2fo.pdf
-apache-fop/src/test/resources/output_jtidy.pdf
+testing-modules/report-*.json
+
+libraries-2/*.db
+
+# SDKMan
+.sdkmanrc

README.md

@@ -1,5 +1,3 @@
-**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
 ==============================
 
@@ -22,10 +20,38 @@ This project is **a collection of small and focused tutorials** - each covering
 A strong focus of these is, of course, the Spring Framework - Spring, Spring Boot and Spring Security. 
 In additional to Spring, the modules here are covering a number of aspects in Java. 
 
+Profile based segregation
+====================
+
+We are using maven build profiles to segregate the huge list of individual projects we have in our repository.
+
+The projects are broadly divided into 3 list: first, second and heavy. 
+
+Next, they are segregated further on the basis of tests that we want to execute.
+
+Therefore, we have a total of 6 profiles:
+
+| Profile                 | Includes                    | Type of test enabled |
+| ----------------------- | --------------------------- | -------------------- |
+| default-first           | First set of projects       | *UnitTest            |
+| integration-lite-first  | First set of projects       | *IntegrationTest     |
+| default-second          | Second set of projects      | *UnitTest            |
+| integration-lite-second | Second set of projects      | *IntegrationTest     |
+| default-heavy           | Heavy/long running projects | *UnitTest            |
+| integration-heavy       | Heavy/long running projects | *IntegrationTest     |
 
 Building the project
 ====================
-To do the full build, do: `mvn clean install`
+
+Though it should not be needed often to build the entire repository at once because we are usually concerned with a specific module.
+
+But if we want to, we can invoke the below command from the root of the repository if we want to build the entire repository with only Unit Tests enabled:
+
+`mvn clean install -Pdefault-first,default-second,default-heavy`
+
+or if we want to build the entire repository with Integration Tests enabled, we can do:
+
+`mvn clean install -Pintegration-lite-first,integration-lite-second,integration-heavy`
 
 
 Building a single module
@@ -46,8 +72,18 @@ When you're working with an individual module, there's no need to import all of
 
 Running Tests
 =============
-The command `mvn clean install` will run the unit tests in a module.
-To run the integration tests, use the command `mvn clean install -Pintegration-lite-first`
+The command `mvn clean install` from within a module will run the unit tests in that module.
+For Spring modules this will also run the `SpringContextTest` if present.
+
+To run the integration tests, use the command:
+
+`mvn clean install -Pintegration-lite-first` or 
+
+`mvn clean install -Pintegration-lite-second` or 
+
+`mvn clean install -Pintegration-heavy`
+
+depending on the list where our module exists
 
 
 

akka-http/pom.xml

@@ -1,7 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-         xmlns="http://maven.apache.org/POM/4.0.0"
-         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+<project
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+    xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
     <modelVersion>4.0.0</modelVersion>
     <artifactId>akka-http</artifactId>
     <name>akka-http</name>

akka-streams/pom.xml

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<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>akka-streams</artifactId>
     <name>akka-streams</name>

algorithms-genetic/README.md

@@ -5,6 +5,6 @@ This module contains articles about genetic algorithms.
 ### Relevant articles:
 
 - [Introduction to Jenetics Library](https://www.baeldung.com/jenetics)
-- [Ant Colony Optimization](https://www.baeldung.com/java-ant-colony-optimization)
+- [Ant Colony Optimization with a Java Example](https://www.baeldung.com/java-ant-colony-optimization)
 - [Design a Genetic Algorithm in Java](https://www.baeldung.com/java-genetic-algorithm)
 - [The Traveling Salesman Problem in Java](https://www.baeldung.com/java-simulated-annealing-for-traveling-salesman)

algorithms-genetic/pom.xml

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<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>algorithms-genetic</artifactId>
     <version>0.0.1-SNAPSHOT</version>

algorithms-miscellaneous-1/README.md

@@ -6,8 +6,8 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 ### Relevant articles:
 
 - [Validating Input With Finite Automata in Java](https://www.baeldung.com/java-finite-automata)
-- [Example of Hill Climbing Algorithm](https://www.baeldung.com/java-hill-climbing-algorithm)
-- [Introduction to Minimax Algorithm](https://www.baeldung.com/java-minimax-algorithm)
+- [Example of Hill Climbing Algorithm in Java](https://www.baeldung.com/java-hill-climbing-algorithm)
+- [Introduction to Minimax Algorithm with a Java Implementation](https://www.baeldung.com/java-minimax-algorithm)
 - [How to Calculate Levenshtein Distance in Java?](https://www.baeldung.com/java-levenshtein-distance)
 - [How to Find the Kth Largest Element in Java](https://www.baeldung.com/java-kth-largest-element)
-- More articles: [[next -->]](/../algorithms-miscellaneous-2)
+- More articles: [[next -->]](/algorithms-miscellaneous-2)

algorithms-miscellaneous-1/pom.xml

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<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>algorithms-miscellaneous-1</artifactId>
     <version>0.0.1-SNAPSHOT</version>

algorithms-miscellaneous-2/README.md

@@ -14,4 +14,4 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Displaying Money Amounts in Words](https://www.baeldung.com/java-money-into-words)
 - [A Collaborative Filtering Recommendation System in Java](https://www.baeldung.com/java-collaborative-filtering-recommendations)
 - [Implementing A* Pathfinding in Java](https://www.baeldung.com/java-a-star-pathfinding)
-- More articles: [[<-- prev]](/../algorithms-miscellaneous-1) [[next -->]](/../algorithms-miscellaneous-3)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-1) [[next -->]](/algorithms-miscellaneous-3)

algorithms-miscellaneous-2/pom.xml

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<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>algorithms-miscellaneous-2</artifactId>
     <version>0.0.1-SNAPSHOT</version>

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

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

algorithms-miscellaneous-3/README.md

@@ -13,6 +13,5 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Checking if a Java Graph has a Cycle](https://www.baeldung.com/java-graph-has-a-cycle)
 - [A Guide to the Folding Technique in Java](https://www.baeldung.com/folding-hashing-technique)
 - [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)
 - More articles: [[<-- prev]](/algorithms-miscellaneous-2) [[next -->]](/algorithms-miscellaneous-4)

algorithms-miscellaneous-3/pom.xml

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<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>algorithms-miscellaneous-3</artifactId>
     <version>0.0.1-SNAPSHOT</version>

algorithms-miscellaneous-4/README.md

@@ -5,8 +5,8 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 ### Relevant articles:
 
 - [Multi-Swarm Optimization Algorithm in Java](https://www.baeldung.com/java-multi-swarm-algorithm)
-- [Check If a String Contains All The Letters of The Alphabet](https://www.baeldung.com/java-string-contains-all-letters)
-- [Find the Middle Element of a Linked List](https://www.baeldung.com/java-linked-list-middle-element)
+- [Check If a String Contains All The Letters of The Alphabet with Java](https://www.baeldung.com/java-string-contains-all-letters)
+- [Find the Middle Element of a Linked List in Java](https://www.baeldung.com/java-linked-list-middle-element)
 - [Find Substrings That Are Palindromes in Java](https://www.baeldung.com/java-palindrome-substrings)
 - [Find the Longest Substring without Repeating Characters](https://www.baeldung.com/java-longest-substring-without-repeated-characters)
 - [Permutations of an Array in Java](https://www.baeldung.com/java-array-permutations)

algorithms-miscellaneous-4/pom.xml

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<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>algorithms-miscellaneous-4</artifactId>
     <version>0.0.1-SNAPSHOT</version>

algorithms-miscellaneous-5/README.md

@@ -9,14 +9,11 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Reversing a Binary Tree in Java](https://www.baeldung.com/java-reversing-a-binary-tree)
 - [Find If Two Numbers Are Relatively Prime in Java](https://www.baeldung.com/java-two-relatively-prime-numbers)
 - [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)
+- [How to Determine if a Binary Tree is Balanced in Java](https://www.baeldung.com/java-balanced-binary-tree)
 - [Overview of Combinatorial Problems in Java](https://www.baeldung.com/java-combinatorial-algorithms)
-- [Prim’s Algorithm](https://www.baeldung.com/java-prim-algorithm)
-- [Maximum Subarray Problem](https://www.baeldung.com/java-maximum-subarray)
-- [How to Merge Two Sorted Arrays](https://www.baeldung.com/java-merge-sorted-arrays)
-- [Median of Stream of Integers using Heap](https://www.baeldung.com/java-stream-integers-median-using-heap)
-- [Kruskal’s Algorithm for Spanning Trees](https://www.baeldung.com/java-spanning-trees-kruskal)
-- [Balanced Brackets Algorithm in Java](https://www.baeldung.com/java-balanced-brackets-algorithm)
-- [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
-- [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
-- More articles: [[<-- prev]](/../algorithms-miscellaneous-4)
+- [Prim’s Algorithm with a Java Implementation](https://www.baeldung.com/java-prim-algorithm)
+- [Maximum Subarray Problem in Java](https://www.baeldung.com/java-maximum-subarray)
+- [How to Merge Two Sorted Arrays in Java](https://www.baeldung.com/java-merge-sorted-arrays)
+- [Median of Stream of Integers using Heap in Java](https://www.baeldung.com/java-stream-integers-median-using-heap)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-4) [[next -->]](/algorithms-miscellaneous-6)
+

algorithms-miscellaneous-5/pom.xml

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<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>algorithms-miscellaneous-5</artifactId>
     <version>0.0.1-SNAPSHOT</version>
@@ -23,12 +25,6 @@
             <artifactId>commons-math3</artifactId>
             <version>${commons-math3.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.projectlombok</groupId>
-            <artifactId>lombok</artifactId>
-            <version>${lombok.version}</version>
-            <scope>provided</scope>
-        </dependency>
         <dependency>
             <groupId>pl.allegro.finance</groupId>
             <artifactId>tradukisto</artifactId>
@@ -39,11 +35,6 @@
             <artifactId>guava</artifactId>
             <version>${guava.version}</version>
         </dependency>
-        <dependency>
-            <groupId>com.fasterxml.jackson.core</groupId>
-            <artifactId>jackson-databind</artifactId>
-            <version>${jackson.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.junit.platform</groupId>
             <artifactId>junit-platform-commons</artifactId>
@@ -76,7 +67,6 @@
         <commons-codec.version>1.11</commons-codec.version>
         <commons-math3.version>3.6.1</commons-math3.version>
         <guava.version>28.1-jre</guava.version>
-        <jackson.version>2.10.2</jackson.version>
         <junit.platform.version>1.6.0</junit.platform.version>
     </properties>
 

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/boruvka/BoruvkaMST.java

@@ -1,61 +0,0 @@
-package com.baeldung.algorithms.boruvka;
-
-public class BoruvkaMST {
-
-    private static Tree mst = new Tree();
-    private static int totalWeight;
-
-    public BoruvkaMST(Graph graph) {
-        DisjointSet dSet = new DisjointSet(graph.getNodes());
-
-        // repeat at most log N times or until we have N-1 edges
-        for (int t = 1; t < graph.getNodes() && mst.getEdgeCount() < graph.getNodes() - 1; t = t + t) {
-
-            // foreach tree in forest, find closest edge
-            Edge[] closestEdgeArray = new Edge[graph.getNodes()];
-            for (Edge edge : graph.getAllEdges()) {
-                int first = edge.getFirst();
-                int second = edge.getSecond();
-                int firstParent = dSet.getParent(first);
-                int secondParent = dSet.getParent(second);
-                if (firstParent == secondParent) {
-                    continue; // same tree
-                }
-                if (closestEdgeArray[firstParent] == null || edge.getWeight() < closestEdgeArray[firstParent].getWeight()) {
-                    closestEdgeArray[firstParent] = edge;
-                }
-                if (closestEdgeArray[secondParent] == null || edge.getWeight() < closestEdgeArray[secondParent].getWeight()) {
-                    closestEdgeArray[secondParent] = edge;
-                }
-            }
-
-            // add newly discovered edges to MST
-            for (int i = 0; i < graph.getNodes(); i++) {
-                Edge edge = closestEdgeArray[i];
-                if (edge != null) {
-                    int first = edge.getFirst();
-                    int second = edge.getSecond();
-                    // don't add the same edge twice
-                    if (dSet.getParent(first) != dSet.getParent(second)) {
-                        mst.addEdge(edge);
-                        totalWeight += edge.getWeight();
-                        dSet.union(first, second);
-                    }
-                }
-            }
-        }
-    }
-
-    public Iterable<Edge> getMST() {
-        return mst;
-    }
-
-    public int getTotalWeight() {
-        return totalWeight;
-    }
-
-    public String toString() {
-        return "MST: " + mst.toString() + " | Total Weight: " + totalWeight;
-    }
-
-}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/boruvka/DisjointSet.java

@@ -1,49 +0,0 @@
-package com.baeldung.algorithms.boruvka;
-
-import java.util.Arrays;
-
-public class DisjointSet {
-
-    private int[] nodeParents;
-    private int[] nodeRanks;
-
-    public DisjointSet(int n) {
-        nodeParents = new int[n];
-        nodeRanks = new int[n];
-        for (int i = 0; i < n; i++) {
-            nodeParents[i] = i;
-            nodeRanks[i] = 0;
-        }
-    }
-
-    public int getParent(int node) {
-        while (node != nodeParents[node]) {
-            node = nodeParents[node];
-        }
-        return node;
-    }
-
-    public void union(int node1, int node2) {
-        int node1Parent = getParent(node1);
-        int node2Parent = getParent(node2);
-        if (node1Parent == node2Parent) {
-            return;
-        }
-
-        if (nodeRanks[node1Parent] < nodeRanks[node2Parent]) {
-            nodeParents[node1Parent] = node2Parent;
-        }
-        else if (nodeRanks[node1Parent] > nodeRanks[node2Parent]) {
-            nodeParents[node2Parent] = node1Parent;
-        }
-        else {
-            nodeParents[node2Parent] = node1Parent;
-            nodeRanks[node1Parent]++;
-        }
-    }
-
-    public String toString() {
-        return "Parent: " + Arrays.toString(nodeParents) + "Rank: " + Arrays.toString(nodeRanks);
-    }
-
-}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/boruvka/Edge.java

@@ -1,40 +0,0 @@
-package com.baeldung.algorithms.boruvka;
-
-public class Edge {
-
-    private final int first;
-    private final int second;
-    private final int weight;
-
-    public Edge(int first, int second, int weight) {
-        this.first = first;
-        this.second = second;
-        this.weight = weight;
-    }
-
-    public double getWeight() {
-        return weight;
-    }
-
-    public int getFirst() {
-        return first;
-    }
-    
-    public int getSecond() {
-        return second;
-    }
-
-    public int getOtherNode(int firstNode) {
-        int secondNode = 0;
-        if (firstNode == first)
-            secondNode = second;
-        else if (firstNode == second)
-            secondNode = first;
-        return secondNode;
-    }
-
-    public String toString() {
-        return String.format("%d-%d %d", first, second, weight);
-    }
-
-}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/boruvka/Graph.java

@@ -1,64 +0,0 @@
-package com.baeldung.algorithms.boruvka;
-
-import java.io.IOException;
-
-import com.fasterxml.jackson.core.JsonParseException;
-import com.fasterxml.jackson.databind.JsonMappingException;
-
-public class Graph {
-
-    private int nodes;
-    private int edges;
-    private Tree[] trees;
-
-    public Graph(Input jsonGraph) throws JsonParseException, JsonMappingException, IOException {
-        nodes = jsonGraph.getNodes();
-        trees = (Tree[]) new Tree[nodes];
-        for (int i = 0; i < nodes; i++) {
-            trees[i] = new Tree();
-        }
-
-        int edgesFromInput = jsonGraph.getEdges();
-        for (int i = 0; i < edgesFromInput; i++) {
-            int first = jsonGraph.getEdgeList()
-                .get(i)
-                .getFirst();
-            int second = jsonGraph.getEdgeList()
-                .get(i)
-                .getSecond();
-            int weight = jsonGraph.getEdgeList()
-                .get(i)
-                .getWeight();
-            Edge edge = new Edge(first, second, weight);
-            
-            trees[first].addEdge(edge);
-            trees[second].addEdge(edge);
-            edges++;
-        }
-
-    }
-
-    public int getNodes() {
-        return nodes;
-    }
-
-    public int getEdges() {
-        return edges;
-    }
-
-    public Iterable<Edge> iterableTree(int i) {
-        return trees[i];
-    }
-
-    public Iterable<Edge> getAllEdges() {
-        Iterable<Edge> list = new Tree();
-        for (int i = 0; i < nodes; i++) {
-            for (Edge edge : iterableTree(i)) {
-                if (edge.getOtherNode(i) > i) {
-                    ((Tree) list).addEdge(edge);
-                }
-            }
-        }
-        return list;
-    }
-}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/boruvka/Input.java

@@ -1,65 +0,0 @@
-package com.baeldung.algorithms.boruvka;
-
-import java.util.List;
-
-public class Input {
-    private int nodes;
-    private int edges;
-    private List<E> edgeList;
-
-    public int getNodes() {
-        return nodes;
-    }
-
-    public void setNodes(int nodes) {
-        this.nodes = nodes;
-    }
-
-    public int getEdges() {
-        return edges;
-    }
-
-    public void setEdges(int edges) {
-        this.edges = edges;
-    }
-
-    public List<E> getEdgeList() {
-        return edgeList;
-    }
-
-    public void setEdgeList(List<E> edgeList) {
-        this.edgeList = edgeList;
-    }
-
-    static class E {
-        private int first;
-        private int second;
-        private int weight;
-
-        public int getFirst() {
-            return first;
-        }
-
-        public void setFirst(int first) {
-            this.first = first;
-        }
-
-        public int getSecond() {
-            return second;
-        }
-
-        public void setSecond(int second) {
-            this.second = second;
-        }
-
-        public int getWeight() {
-            return weight;
-        }
-
-        public void setWeight(int weight) {
-            this.weight = weight;
-        }
-
-    }
-
-}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/boruvka/Tree.java

@@ -1,63 +0,0 @@
-package com.baeldung.algorithms.boruvka;
-
-import java.util.Iterator;
-
-public class Tree implements Iterable<Edge> {
-    private Node root;
-    private int edgeCount;
-
-    private static class Node {
-        private Edge edge;
-        private Node next;
-
-        public String toString() {
-            String nextStr = next != null ? next.toString() : "";
-            return edge.toString() + " | " + nextStr;
-        }
-    }
-
-    public Tree() {
-        root = null;
-        edgeCount = 0;
-    }
-
-    public int getEdgeCount() {
-        return edgeCount;
-    }
-
-    public void addEdge(Edge edge) {
-        Node oldRoot = root;
-        root = new Node();
-        root.edge = edge;
-        root.next = oldRoot;
-        edgeCount++;
-    }
-
-    public String toString() {
-        String rootStr = root != null ? root.toString() : "";
-        return "Tree: " + rootStr + "Size: " + edgeCount;
-    }
-
-    public Iterator<Edge> iterator() {
-        return new LinkedIterator(root);
-    }
-
-    private class LinkedIterator implements Iterator<Edge> {
-        private Node current;
-
-        public LinkedIterator(Node root) {
-            current = root;
-        }
-
-        public boolean hasNext() {
-            return current != null;
-        }
-
-        public Edge next() {
-            Edge edge = current.edge;
-            current = current.next;
-            return edge;
-        }
-    }
-
-}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/boruvka/BoruvkaUnitTest.java

@@ -1,48 +0,0 @@
-package com.baeldung.algorithms.boruvka;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStreamReader;
-
-import org.junit.Before;
-import org.junit.Test;
-
-import com.fasterxml.jackson.core.JsonParseException;
-import com.fasterxml.jackson.databind.JsonMappingException;
-import com.fasterxml.jackson.databind.ObjectMapper;
-
-public class BoruvkaUnitTest {
-
-    private Input input;
-    private static String INPUT_JSON = "/input.json";
-
-    @Before
-    public void convertInputJsonToObject() throws JsonParseException, JsonMappingException, IOException {
-        ObjectMapper mapper = new ObjectMapper();
-        StringBuilder jsonStr = new StringBuilder();
-        try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(BoruvkaMST.class.getResourceAsStream(INPUT_JSON)))) {
-            String line;
-            while ((line = bufferedReader.readLine()) != null) {
-                jsonStr.append(line)
-                    .append("\n");
-            }
-        }
-
-        input = mapper.readValue(jsonStr.toString(), Input.class);
-
-    }
-
-    @Test
-    public void givenInputGraph_whenBoruvkaPerformed_thenMinimumSpanningTree() throws JsonParseException, JsonMappingException, IOException {
-        Graph graph = new Graph(input);
-        BoruvkaMST boruvkaMST = new BoruvkaMST(graph);
-
-        Tree mst = (Tree) boruvkaMST.getMST();
-
-        assertEquals(30, boruvkaMST.getTotalWeight());
-        assertEquals(4, mst.getEdgeCount());
-    }
-
-}

algorithms-miscellaneous-6/README.md

@@ -0,0 +1,13 @@
+### Relevant Articles:
+
+- [Boruvka’s Algorithm for Minimum Spanning Trees in Java](https://www.baeldung.com/java-boruvka-algorithm)
+- [Gradient Descent in Java](https://www.baeldung.com/java-gradient-descent)
+- [Kruskal’s Algorithm for Spanning Trees with a Java Implementation](https://www.baeldung.com/java-spanning-trees-kruskal)
+- [Balanced Brackets Algorithm in Java](https://www.baeldung.com/java-balanced-brackets-algorithm)
+- [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
+- [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
+- [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
+- [Implementing a 2048 Solver in Java](https://www.baeldung.com/2048-java-solver)
+- [Finding Top K Elements in a Java Array](https://www.baeldung.com/java-array-top-elements)
+- [Reversing a Linked List in Java](https://www.baeldung.com/java-reverse-linked-list)
+- More articles: [[<-- prev]](/algorithms-miscellaneous-5)

algorithms-miscellaneous-6/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>
+    <artifactId>algorithms-miscellaneous-6</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>algorithms-miscellaneous-6</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    
+    <dependencies>
+    <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-commons</artifactId>
+            <version>${junit.platform.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${org.assertj.core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
+    </dependencies>
+    
+    <properties>
+        <guava.version>28.1-jre</guava.version>
+        <org.assertj.core.version>3.9.0</org.assertj.core.version>
+        <junit.platform.version>1.6.0</junit.platform.version>
+        <commons-math3.version>3.6.1</commons-math3.version>
+    </properties>
+
+</project>

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/boruvka/BoruvkaMST.java

@@ -0,0 +1,84 @@
+package com.baeldung.algorithms.boruvka;
+
+import com.google.common.graph.EndpointPair;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+
+public class BoruvkaMST {
+
+    private static MutableValueGraph<Integer, Integer> mst = ValueGraphBuilder.undirected()
+        .build();
+    private static int totalWeight;
+
+    public BoruvkaMST(MutableValueGraph<Integer, Integer> graph) {
+
+        int size = graph.nodes().size();
+
+        UnionFind uf = new UnionFind(size);
+
+        // repeat at most log N times or until we have N-1 edges
+        for (int t = 1; t < size && mst.edges().size() < size - 1; t = t + t) {
+            
+            EndpointPair<Integer>[] closestEdgeArray = new EndpointPair[size];
+
+            // foreach tree in graph, find closest edge
+            for (EndpointPair<Integer> edge : graph.edges()) {
+                int u = edge.nodeU();
+                int v = edge.nodeV();
+                int uParent = uf.find(u);
+                int vParent = uf.find(v);
+                if (uParent == vParent) {
+                    continue; // same tree
+                }
+
+                int weight = graph.edgeValueOrDefault(u, v, 0);
+
+                if (closestEdgeArray[uParent] == null) {
+                    closestEdgeArray[uParent] = edge;
+                }
+                if (closestEdgeArray[vParent] == null) {
+                    closestEdgeArray[vParent] = edge;
+                }
+
+                int uParentWeight = graph.edgeValueOrDefault(closestEdgeArray[uParent].nodeU(), closestEdgeArray[uParent].nodeV(), 0);
+                int vParentWeight = graph.edgeValueOrDefault(closestEdgeArray[vParent].nodeU(), closestEdgeArray[vParent].nodeV(), 0);
+
+                if (weight < uParentWeight) {
+                    closestEdgeArray[uParent] = edge;
+                }
+                if (weight < vParentWeight) {
+                    closestEdgeArray[vParent] = edge;
+                }
+            }
+
+            // add newly discovered edges to MST
+            for (int i = 0; i < size; i++) {
+                EndpointPair<Integer> edge = closestEdgeArray[i];
+                if (edge != null) {
+                    int u = edge.nodeU();
+                    int v = edge.nodeV();
+                    int weight = graph.edgeValueOrDefault(u, v, 0);
+                    // don't add the same edge twice
+                    if (uf.find(u) != uf.find(v)) {
+                        mst.putEdgeValue(u, v, weight);
+                        totalWeight += weight;
+                        uf.union(u, v);
+                    }
+                }
+            }
+        }
+    }
+
+    public MutableValueGraph<Integer, Integer> getMST() {
+        return mst;
+    }
+
+    public int getTotalWeight() {
+        return totalWeight;
+    }
+
+    public String toString() {
+        return "MST: " + mst.toString() + " | Total Weight: " + totalWeight;
+    }
+
+}

algorithms-miscellaneous-6/src/main/java/com/baeldung/algorithms/boruvka/UnionFind.java

@@ -0,0 +1,39 @@
+package com.baeldung.algorithms.boruvka;
+
+public class UnionFind {
+    private int[] parents;
+    private int[] ranks;
+
+    public UnionFind(int n) {
+        parents = new int[n];
+        ranks = new int[n];
+        for (int i = 0; i < n; i++) {
+            parents[i] = i;
+            ranks[i] = 0;
+        }
+    }
+
+    public int find(int u) {
+        while (u != parents[u]) {
+            u = parents[u];
+        }
+        return u;
+    }
+
+    public void union(int u, int v) {
+        int uParent = find(u);
+        int vParent = find(v);
+        if (uParent == vParent) {
+            return;
+        }
+
+        if (ranks[uParent] < ranks[vParent]) {
+            parents[uParent] = vParent;
+        } else if (ranks[uParent] > ranks[vParent]) {
+            parents[vParent] = uParent;
+        } else {
+            parents[vParent] = uParent;
+            ranks[uParent]++;
+        }
+    }
+}