Merge pull request #9 from eugenp/master

merge sync

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/Graph.java

@@ -0,0 +1,30 @@
+package com.baeldung.algorithms.astar;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+
+public class Graph<T extends GraphNode> {
+    private final Set<T> nodes;
+
+    private final Map<String, Set<String>> connections;
+
+    public Graph(Set<T> nodes, Map<String, Set<String>> connections) {
+        this.nodes = nodes;
+        this.connections = connections;
+    }
+
+    public T getNode(String id) {
+        return nodes.stream()
+            .filter(node -> node.getId().equals(id))
+            .findFirst()
+            .orElseThrow(() -> new IllegalArgumentException("No node found with ID"));
+    }
+
+    public Set<T> getConnections(T node) {
+        return connections.get(node.getId()).stream()
+            .map(this::getNode)
+            .collect(Collectors.toSet());
+    }
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/GraphNode.java

@@ -0,0 +1,5 @@
+package com.baeldung.algorithms.astar;
+
+public interface GraphNode {
+    String getId();
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/RouteFinder.java

@@ -0,0 +1,66 @@
+package com.baeldung.algorithms.astar;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.PriorityQueue;
+import java.util.Queue;
+import java.util.stream.Collectors;
+
+public class RouteFinder<T extends GraphNode> {
+    private final Graph<T> graph;
+    private final Scorer<T> nextNodeScorer;
+    private final Scorer<T> targetScorer;
+
+    public RouteFinder(Graph<T> graph, Scorer<T> nextNodeScorer, Scorer<T> targetScorer) {
+        this.graph = graph;
+        this.nextNodeScorer = nextNodeScorer;
+        this.targetScorer = targetScorer;
+    }
+
+    public List<T> findRoute(T from, T to) {
+        Map<T, RouteNode<T>> allNodes = new HashMap<>();
+        Queue<RouteNode> openSet = new PriorityQueue<>();
+
+        RouteNode<T> start = new RouteNode<>(from, null, 0d, targetScorer.computeCost(from, to));
+        allNodes.put(from, start);
+        openSet.add(start);
+
+        while (!openSet.isEmpty()) {
+            System.out.println("Open Set contains: " + openSet.stream().map(RouteNode::getCurrent).collect(Collectors.toSet()));
+            RouteNode<T> next = openSet.poll();
+            System.out.println("Looking at node: " + next);
+            if (next.getCurrent().equals(to)) {
+                System.out.println("Found our destination!");
+
+                List<T> route = new ArrayList<>();
+                RouteNode<T> current = next;
+                do {
+                    route.add(0, current.getCurrent());
+                    current = allNodes.get(current.getPrevious());
+                } while (current != null);
+
+                System.out.println("Route: " + route);
+                return route;
+            }
+
+            graph.getConnections(next.getCurrent()).forEach(connection -> {
+                double newScore = next.getRouteScore() + nextNodeScorer.computeCost(next.getCurrent(), connection);
+                RouteNode<T> nextNode = allNodes.getOrDefault(connection, new RouteNode<>(connection));
+                allNodes.put(connection, nextNode);
+
+                if (nextNode.getRouteScore() > newScore) {
+                    nextNode.setPrevious(next.getCurrent());
+                    nextNode.setRouteScore(newScore);
+                    nextNode.setEstimatedScore(newScore + targetScorer.computeCost(connection, to));
+                    openSet.add(nextNode);
+                    System.out.println("Found a better route to node: " + nextNode);
+                }
+            });
+        }
+
+        throw new IllegalStateException("No route found");
+    }
+
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/RouteNode.java

@@ -0,0 +1,67 @@
+package com.baeldung.algorithms.astar;
+
+import java.util.StringJoiner;
+
+class RouteNode<T extends GraphNode> implements Comparable<RouteNode> {
+    private final T current;
+    private T previous;
+    private double routeScore;
+    private double estimatedScore;
+
+    RouteNode(T current) {
+        this(current, null, Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY);
+    }
+
+    RouteNode(T current, T previous, double routeScore, double estimatedScore) {
+        this.current = current;
+        this.previous = previous;
+        this.routeScore = routeScore;
+        this.estimatedScore = estimatedScore;
+    }
+
+    T getCurrent() {
+        return current;
+    }
+
+    T getPrevious() {
+        return previous;
+    }
+
+    double getRouteScore() {
+        return routeScore;
+    }
+
+    double getEstimatedScore() {
+        return estimatedScore;
+    }
+
+    void setPrevious(T previous) {
+        this.previous = previous;
+    }
+
+    void setRouteScore(double routeScore) {
+        this.routeScore = routeScore;
+    }
+
+    void setEstimatedScore(double estimatedScore) {
+        this.estimatedScore = estimatedScore;
+    }
+
+    @Override
+    public int compareTo(RouteNode other) {
+        if (this.estimatedScore > other.estimatedScore) {
+            return 1;
+        } else if (this.estimatedScore < other.estimatedScore) {
+            return -1;
+        } else {
+            return 0;
+        }
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", RouteNode.class.getSimpleName() + "[", "]").add("current=" + current)
+            .add("previous=" + previous).add("routeScore=" + routeScore).add("estimatedScore=" + estimatedScore)
+            .toString();
+    }
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/Scorer.java

@@ -0,0 +1,5 @@
+package com.baeldung.algorithms.astar;
+
+public interface Scorer<T extends GraphNode> {
+    double computeCost(T from, T to);
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/underground/HaversineScorer.java

@@ -0,0 +1,19 @@
+package com.baeldung.algorithms.astar.underground;
+
+import com.baeldung.algorithms.astar.Scorer;
+
+public class HaversineScorer implements Scorer<Station> {
+    @Override
+    public double computeCost(Station from, Station to) {
+        double R = 6372.8; // In kilometers
+
+        double dLat = Math.toRadians(to.getLatitude() - from.getLatitude());
+        double dLon = Math.toRadians(to.getLongitude() - from.getLongitude());
+        double lat1 = Math.toRadians(from.getLatitude());
+        double lat2 = Math.toRadians(to.getLatitude());
+
+        double a = Math.pow(Math.sin(dLat / 2),2) + Math.pow(Math.sin(dLon / 2),2) * Math.cos(lat1) * Math.cos(lat2);
+        double c = 2 * Math.asin(Math.sqrt(a));
+        return R * c;
+    }
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/underground/Station.java

@@ -0,0 +1,42 @@
+package com.baeldung.algorithms.astar.underground;
+
+import java.util.StringJoiner;
+
+import com.baeldung.algorithms.astar.GraphNode;
+
+public class Station implements GraphNode {
+    private final String id;
+    private final String name;
+    private final double latitude;
+    private final double longitude;
+
+    public Station(String id, String name, double latitude, double longitude) {
+        this.id = id;
+        this.name = name;
+        this.latitude = latitude;
+        this.longitude = longitude;
+    }
+
+    @Override
+    public String getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public double getLatitude() {
+        return latitude;
+    }
+
+    public double getLongitude() {
+        return longitude;
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", Station.class.getSimpleName() + "[", "]").add("id='" + id + "'")
+            .add("name='" + name + "'").add("latitude=" + latitude).add("longitude=" + longitude).toString();
+    }
+}

algorithms-miscellaneous-4/README.md

@@ -11,4 +11,5 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [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)
+- [Find the Smallest Missing Integer in an Array](https://www.baeldung.com/java-smallest-missing-integer-in-array)
 - More articles: [[<-- prev]](/algorithms-miscellaneous-3) [[next -->]](/algorithms-miscellaneous-5)

algorithms-miscellaneous-5/README.md

@@ -9,4 +9,5 @@ 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)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-4)

algorithms-miscellaneous-5/pom.xml

@@ -17,6 +17,11 @@
             <artifactId>commons-codec</artifactId>
             <version>${commons-codec.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
@@ -28,6 +33,7 @@
             <artifactId>tradukisto</artifactId>
             <version>${tradukisto.version}</version>
         </dependency>
+
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -52,6 +58,7 @@
         <tradukisto.version>1.0.1</tradukisto.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
+        <commons-math3.version>3.6.1</commons-math3.version>
     </properties>
 
 </project>

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/caesarcipher/CaesarCipher.java

@@ -0,0 +1,83 @@
+package com.baeldung.algorithms.caesarcipher;
+
+import org.apache.commons.math3.stat.inference.ChiSquareTest;
+
+import java.util.Arrays;
+import java.util.stream.IntStream;
+
+public class CaesarCipher {
+    private static final char LETTER_A = 'a';
+    private static final char LETTER_Z = 'z';
+    private static final int ALPHABET_SIZE = LETTER_Z - LETTER_A + 1;
+    private static final double[] ENGLISH_LETTERS_PROBABILITIES = {0.073, 0.009, 0.030, 0.044, 0.130, 0.028, 0.016, 0.035, 0.074, 0.002, 0.003, 0.035, 0.025, 0.078, 0.074, 0.027, 0.003, 0.077, 0.063, 0.093, 0.027, 0.013, 0.016, 0.005, 0.019, 0.001};
+
+    public String cipher(String message, int offset) {
+        StringBuilder result = new StringBuilder();
+
+        for (char character : message.toCharArray()) {
+            if (character != ' ') {
+                int originalAlphabetPosition = character - LETTER_A;
+                int newAlphabetPosition = (originalAlphabetPosition + offset) % ALPHABET_SIZE;
+                char newCharacter = (char) (LETTER_A + newAlphabetPosition);
+                result.append(newCharacter);
+            } else {
+                result.append(character);
+            }
+        }
+
+        return result.toString();
+    }
+
+    public String decipher(String message, int offset) {
+        return cipher(message, ALPHABET_SIZE - (offset % ALPHABET_SIZE));
+    }
+
+    public int breakCipher(String message) {
+        return probableOffset(chiSquares(message));
+    }
+
+    private double[] chiSquares(String message) {
+        double[] expectedLettersFrequencies = expectedLettersFrequencies(message.length());
+
+        double[] chiSquares = new double[ALPHABET_SIZE];
+
+        for (int offset = 0; offset < chiSquares.length; offset++) {
+            String decipheredMessage = decipher(message, offset);
+            long[] lettersFrequencies = observedLettersFrequencies(decipheredMessage);
+            double chiSquare = new ChiSquareTest().chiSquare(expectedLettersFrequencies, lettersFrequencies);
+            chiSquares[offset] = chiSquare;
+        }
+
+        return chiSquares;
+    }
+
+    private long[] observedLettersFrequencies(String message) {
+        return IntStream.rangeClosed(LETTER_A, LETTER_Z)
+          .mapToLong(letter -> countLetter((char) letter, message))
+          .toArray();
+    }
+
+    private long countLetter(char letter, String message) {
+        return message.chars()
+          .filter(character -> character == letter)
+          .count();
+    }
+
+    private double[] expectedLettersFrequencies(int messageLength) {
+        return Arrays.stream(ENGLISH_LETTERS_PROBABILITIES)
+          .map(probability -> probability * messageLength)
+          .toArray();
+    }
+
+    private int probableOffset(double[] chiSquares) {
+        int probableOffset = 0;
+        for (int offset = 0; offset < chiSquares.length; offset++) {
+            System.out.println(String.format("Chi-Square for offset %d: %.2f", offset, chiSquares[offset]));
+            if (chiSquares[offset] < chiSquares[probableOffset]) {
+                probableOffset = offset;
+            }
+        }
+
+        return probableOffset;
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/caesarcipher/CaesarCipherUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.algorithms.caesarcipher;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class CaesarCipherUnitTest {
+    private static final String SENTENCE = "he told me i could never teach a llama to drive";
+    private static final String SENTENCE_SHIFTED_THREE = "kh wrog ph l frxog qhyhu whdfk d oodpd wr gulyh";
+    private static final String SENTENCE_SHIFTED_TEN = "ro dyvn wo s myevn xofob dokmr k vvkwk dy nbsfo";
+
+    private CaesarCipher algorithm = new CaesarCipher();
+
+    @Test
+    void givenSentenceAndShiftThree_whenCipher_thenCipheredMessageWithoutOverflow() {
+        String cipheredSentence = algorithm.cipher(SENTENCE, 3);
+
+        assertThat(cipheredSentence)
+          .isEqualTo(SENTENCE_SHIFTED_THREE);
+    }
+
+    @Test
+    void givenSentenceAndShiftTen_whenCipher_thenCipheredMessageWithOverflow() {
+        String cipheredSentence = algorithm.cipher(SENTENCE, 10);
+
+        assertThat(cipheredSentence)
+          .isEqualTo(SENTENCE_SHIFTED_TEN);
+    }
+
+    @Test
+    void givenSentenceAndShiftThirtySix_whenCipher_thenCipheredLikeTenMessageWithOverflow() {
+        String cipheredSentence = algorithm.cipher(SENTENCE, 36);
+
+        assertThat(cipheredSentence)
+          .isEqualTo(SENTENCE_SHIFTED_TEN);
+    }
+
+    @Test
+    void givenSentenceShiftedThreeAndShiftThree_whenDecipher_thenOriginalSentenceWithoutOverflow() {
+        String decipheredSentence = algorithm.decipher(SENTENCE_SHIFTED_THREE, 3);
+
+        assertThat(decipheredSentence)
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedTenAndShiftTen_whenDecipher_thenOriginalSentenceWithOverflow() {
+        String decipheredSentence = algorithm.decipher(SENTENCE_SHIFTED_TEN, 10);
+
+        assertThat(decipheredSentence)
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedTenAndShiftThirtySix_whenDecipher_thenOriginalSentenceWithOverflow() {
+        String decipheredSentence = algorithm.decipher(SENTENCE_SHIFTED_TEN, 36);
+
+        assertThat(decipheredSentence)
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedThree_whenBreakCipher_thenOriginalSentence() {
+        int offset = algorithm.breakCipher(SENTENCE_SHIFTED_THREE);
+
+        assertThat(offset)
+          .isEqualTo(3);
+
+        assertThat(algorithm.decipher(SENTENCE_SHIFTED_THREE, offset))
+          .isEqualTo(SENTENCE);
+    }
+
+    @Test
+    void givenSentenceShiftedTen_whenBreakCipher_thenOriginalSentence() {
+        int offset = algorithm.breakCipher(SENTENCE_SHIFTED_TEN);
+
+        assertThat(offset)
+          .isEqualTo(10);
+
+        assertThat(algorithm.decipher(SENTENCE_SHIFTED_TEN, offset))
+          .isEqualTo(SENTENCE);
+    }
+}

aws/src/test/java/com/baeldung/dynamodb/rule/LocalDbCreationRule.java

@@ -15,7 +15,7 @@ public class LocalDbCreationRule extends ExternalResource {
     @Override
     protected void before() throws Exception {
         String port = "8000";
-        this.server = ServerRunner.createServerFromCommandLineArgs(new String[]{"-inMemory", "-port", port});
+        this.server = ServerRunner.createServerFromCommandLineArgs(new String[]{"-inMemory","-sharedDb" ,"-port", port});
         server.start();
     }
 

cloud-foundry-uaa/cf-uaa-oauth2-resource-server/src/main/java/com/baeldung/cfuaa/oauth2/resourceserver/CFUAAOAuth2ResourceServerRestController.java

@@ -18,7 +18,7 @@ public class CFUAAOAuth2ResourceServerRestController {
 
     @GetMapping("/read")
     public String read(JwtAuthenticationToken jwtAuthenticationToken) {
-        return "Hello write: " + jwtAuthenticationToken.getTokenAttributes();
+        return "Hello read: " + jwtAuthenticationToken.getTokenAttributes();
     }
 
     @GetMapping("/write")

code-generation/README.md

@@ -7,3 +7,4 @@ This module contains articles about automatic code generation
 - [Introduction to AutoValue](https://www.baeldung.com/introduction-to-autovalue)
 - [Introduction to AutoFactory](https://www.baeldung.com/autofactory)
 - [Google AutoService](https://www.baeldung.com/google-autoservice)
+- [Defensive Copies for Collections Using AutoValue](https://www.baeldung.com/autovalue-defensive-copies)

core-java-modules/core-java-11/pom.xml

@@ -29,6 +29,27 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.collections</groupId>
+            <artifactId>eclipse-collections</artifactId>
+            <version>10.0.0</version>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.collections</groupId>
+            <artifactId>eclipse-collections-api</artifactId>
+            <version>10.0.0</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -42,6 +63,42 @@
                     <target>${maven.compiler.target.version}</target>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>3.2.1</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <finalName>${uberjar.name}</finalName>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>org.openjdk.jmh.Main</mainClass>
+                                </transformer>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
+                            </transformers>
+                            <filters>
+                                <filter>
+                                    <!--
+                                        Shading signed JARs will fail without this.
+                                        http://stackoverflow.com/questions/999489/invalid-signature-file-when-attempting-to-run-a-jar
+                                    -->
+                                    <artifact>*:*</artifact>
+                                    <excludes>
+                                        <exclude>META-INF/*.SF</exclude>
+                                        <exclude>META-INF/*.DSA</exclude>
+                                        <exclude>META-INF/*.RSA</exclude>
+                                    </excludes>
+                                </filter>
+                            </filters>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>
 
@@ -50,6 +107,7 @@
         <maven.compiler.target.version>11</maven.compiler.target.version>
         <guava.version>27.1-jre</guava.version>
         <assertj.version>3.11.1</assertj.version>
+        <uberjar.name>benchmarks</uberjar.name>
+        <jmh.version>1.22</jmh.version>
     </properties>
-
 </project>

core-java-modules/core-java-11/src/main/java/com/baeldung/benchmark/IntegerListFilter.java

@@ -0,0 +1,70 @@
+package com.baeldung.benchmark;
+
+import org.eclipse.collections.api.list.MutableList;
+import org.eclipse.collections.api.list.primitive.IntList;
+import org.eclipse.collections.api.list.primitive.MutableIntList;
+import org.eclipse.collections.impl.factory.primitive.IntLists;
+import org.eclipse.collections.impl.list.mutable.FastList;
+import org.eclipse.collections.impl.list.mutable.primitive.IntArrayList;
+import org.openjdk.jmh.annotations.*;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.PrimitiveIterator;
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.SECONDS)
+@Fork(2)
+public class IntegerListFilter {
+
+    private List<Integer> jdkIntList;
+    private MutableList<Integer> ecMutableList;
+    private IntList ecIntList;
+    private ExecutorService executor;
+
+    @Setup
+    public void setup() {
+        PrimitiveIterator.OfInt iterator = new Random(1L).ints(-10000, 10000).iterator();
+        ecMutableList = FastList.newWithNValues(1_000_000, iterator::nextInt);
+        jdkIntList = new ArrayList<>(1_000_000);
+        jdkIntList.addAll(ecMutableList);
+        ecIntList = ecMutableList.collectInt(i -> i, new IntArrayList(1_000_000));
+        executor = Executors.newWorkStealingPool();
+    }
+
+    @Benchmark
+    public List<Integer> jdkList() {
+        return jdkIntList.stream().filter(i -> i % 5 == 0).collect(Collectors.toList());
+    }
+
+    @Benchmark
+    public MutableList<Integer> ecMutableList() {
+        return ecMutableList.select(i -> i % 5 == 0);
+    }
+
+    @Benchmark
+    public List<Integer> jdkListParallel() {
+        return jdkIntList.parallelStream().filter(i -> i % 5 == 0).collect(Collectors.toList());
+    }
+
+    @Benchmark
+    public MutableList<Integer> ecMutableListParallel() {
+        return ecMutableList.asParallel(executor, 100_000).select(i -> i % 5 == 0).toList();
+    }
+
+    @Benchmark
+    public IntList ecPrimitive() {
+        return this.ecIntList.select(i -> i % 5 == 0);
+    }
+
+    @Benchmark
+    public IntList ecPrimitiveParallel() {
+        return this.ecIntList.primitiveParallelStream().filter(i -> i % 5 == 0).collect(IntLists.mutable::empty, MutableIntList::add, MutableIntList::addAll);
+    }
+}

core-java-modules/core-java-11/src/main/java/com/baeldung/benchmark/IntegerListSum.java

@@ -0,0 +1,67 @@
+package com.baeldung.benchmark;
+
+import org.eclipse.collections.api.list.MutableList;
+import org.eclipse.collections.api.list.primitive.IntList;
+import org.eclipse.collections.impl.list.mutable.FastList;
+import org.eclipse.collections.impl.list.mutable.primitive.IntArrayList;
+import org.openjdk.jmh.annotations.*;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.PrimitiveIterator;
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.SECONDS)
+@Fork(2)
+public class IntegerListSum {
+
+    private List<Integer> jdkIntList;
+    private MutableList<Integer> ecMutableList;
+    private ExecutorService executor;
+    private IntList ecIntList;
+
+    @Setup
+    public void setup() {
+        PrimitiveIterator.OfInt iterator = new Random(1L).ints(-10000, 10000).iterator();
+        ecMutableList = FastList.newWithNValues(1_000_000, iterator::nextInt);
+        jdkIntList = new ArrayList<>(1_000_000);
+        jdkIntList.addAll(ecMutableList);
+        ecIntList = ecMutableList.collectInt(i -> i, new IntArrayList(1_000_000));
+        executor = Executors.newWorkStealingPool();
+    }
+
+    @Benchmark
+    public long jdkList() {
+        return jdkIntList.stream().mapToLong(i -> i).sum();
+    }
+
+    @Benchmark
+    public long ecMutableList() {
+        return ecMutableList.sumOfInt(i -> i);
+    }
+
+    @Benchmark
+    public long jdkListParallel() {
+        return jdkIntList.parallelStream().mapToLong(i -> i).sum();
+    }
+
+    @Benchmark
+    public long ecMutableListParallel() {
+        return ecMutableList.asParallel(executor, 100_000).sumOfInt(i -> i);
+    }
+
+    @Benchmark
+    public long ecPrimitive() {
+        return this.ecIntList.sum();
+    }
+
+    @Benchmark
+    public long ecPrimitiveParallel() {
+        return this.ecIntList.primitiveParallelStream().sum();
+    }
+}

core-java-modules/core-java-11/src/test/java/com/baeldung/benchmark/IntegerListFilterUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.benchmark;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+
+public class IntegerListFilterUnitTest {
+
+    private IntegerListFilter integerListFilter;
+
+    @Before
+    public void init() {
+        integerListFilter = new IntegerListFilter();
+        integerListFilter.setup();
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenJDKListsMustBeOfSameSize() {
+        assertEquals(integerListFilter.jdkList().size(), integerListFilter.jdkListParallel().size());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenMutableListsMustBeOfSameSize() {
+        assertEquals(integerListFilter.ecMutableList().size(), integerListFilter.ecMutableListParallel().size());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenPrimitiveListsMustBeOfSameSize() {
+        assertEquals(integerListFilter.ecPrimitive().size(), integerListFilter.ecPrimitiveParallel().size());
+    }
+}

core-java-modules/core-java-11/src/test/java/com/baeldung/benchmark/IntegerListSumUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.benchmark;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+
+public class IntegerListSumUnitTest {
+
+    private IntegerListSum integerListSum;
+
+    @Before
+    public void init() {
+        integerListSum = new IntegerListSum();
+        integerListSum.setup();
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenJDKListsMustHaveSameValue() {
+        assertEquals(integerListSum.jdkList(), integerListSum.jdkListParallel());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenMutableListsMustHaveSameValue() {
+        assertEquals(integerListSum.ecMutableList(), integerListSum.ecMutableListParallel());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenPrimitiveListsMustHaveSameValue() {
+        assertEquals(integerListSum.ecPrimitive(), integerListSum.ecPrimitiveParallel());
+    }
+}

core-java-modules/core-java-11/src/test/resources/sample.txt

@@ -0,0 +1 @@
+Sample file content

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

@@ -9,4 +9,5 @@ This module contains articles about the Java List collection
 - [List of Primitive Integer Values in Java](https://www.baeldung.com/java-list-primitive-int)
 - [Performance Comparison of Primitive Lists in Java](https://www.baeldung.com/java-list-primitive-performance)
 - [Filtering a Java Collection by a List](https://www.baeldung.com/java-filter-collection-by-list)
+- [How to Count Duplicate Elements in Arraylist](https://www.baeldung.com/java-count-duplicate-elements-arraylist)
 - [[<-- Prev]](/core-java-modules/core-java-collections-list-2)

core-java-modules/core-java-concurrency-advanced-3/pom.xml

@@ -14,11 +14,18 @@
         <relativePath>../../parent-java</relativePath>
     </parent>
 
-    <dependencies>
-    </dependencies>
-
     <build>
         <finalName>core-java-concurrency-advanced-3</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
         <resources>
             <resource>
                 <directory>src/main/resources</directory>
@@ -28,6 +35,8 @@
     </build>
 
     <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
     </properties>
 
 </project>

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/commonissues/CollectionsConcurrencyIssues.java

@@ -0,0 +1,53 @@
+package com.baeldung.commonissues;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class CollectionsConcurrencyIssues {
+
+    private void putIfAbsentList_NonAtomicOperation_ProneToConcurrencyIssues() {
+        List<String> list = Collections.synchronizedList(new ArrayList<>());
+        if (!list.contains("foo")) {
+            list.add("foo");
+        }
+    }
+
+    private void putIfAbsentList_AtomicOperation_ThreadSafe() {
+        List<String> list = Collections.synchronizedList(new ArrayList<>());
+        synchronized (list) {
+            if (!list.contains("foo")) {
+                list.add("foo");
+            }
+        }
+    }
+
+    private void putIfAbsentMap_NonAtomicOperation_ProneToConcurrencyIssues() {
+        Map<String, String> map = new ConcurrentHashMap<>();
+        if (!map.containsKey("foo")) {
+            map.put("foo", "bar");
+        }
+    }
+
+    private void putIfAbsentMap_AtomicOperation_BetterApproach() {
+        Map<String, String> map = new ConcurrentHashMap<>();
+        synchronized (map) {
+            if (!map.containsKey("foo")) {
+                map.put("foo", "bar");
+            }
+        }
+    }
+
+    private void putIfAbsentMap_AtomicOperation_BestApproach() {
+        Map<String, String> map = new ConcurrentHashMap<>();
+        map.putIfAbsent("foo", "bar");
+    }
+
+    private void computeIfAbsentMap_AtomicOperation() {
+        Map<String, String> map = new ConcurrentHashMap<>();
+        map.computeIfAbsent("foo", key -> key + "bar");
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/commonissues/Counter.java

@@ -0,0 +1,13 @@
+package com.baeldung.commonissues;
+
+class Counter {
+    private int counter = 0;
+
+    public void increment() {
+        counter++;
+    }
+
+    public int getValue() {
+        return counter;
+    }
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/commonissues/DeadlockExample.java

@@ -0,0 +1,42 @@
+package com.baeldung.commonissues;
+
+public class DeadlockExample {
+
+    public static Object lock1 = new Object();
+    public static Object lock2 = new Object();
+
+    public static void main(String args[]) {
+        Thread threadA = new Thread(() -> {
+            synchronized (lock1) {
+                System.out.println("ThreadA: Holding lock 1...");
+                sleep();
+                System.out.println("ThreadA: Waiting for lock 2...");
+
+                synchronized (lock2) {
+                    System.out.println("ThreadA: Holding lock 1 & 2...");
+                }
+            }
+        });
+        Thread threadB = new Thread(() -> {
+            synchronized (lock2) {
+                System.out.println("ThreadB: Holding lock 2...");
+                sleep();
+                System.out.println("ThreadB: Waiting for lock 1...");
+
+                synchronized (lock1) {
+                    System.out.println("ThreadB: Holding lock 1 & 2...");
+                }
+            }
+        });
+        threadA.start();
+        threadB.start();
+    }
+
+    private static void sleep() {
+        try {
+            Thread.sleep(100);
+        } catch (InterruptedException e) {
+            throw new RuntimeException();
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/commonissues/SimpleDateFormatThreadUnsafetyExample.java

@@ -0,0 +1,35 @@
+package com.baeldung.commonissues;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class SimpleDateFormatThreadUnsafetyExample {
+
+    private static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
+
+    public static void main(String[] args) {
+        String dateStr = "2019-10-29T11:12:21";
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        for (int i = 0; i < 20; i++) {
+            executorService.submit(() -> parseDate(dateStr));
+        }
+
+        executorService.shutdown();
+    }
+
+    private static void parseDate(String dateStr) {
+        try {
+            Date date = simpleDateFormat.parse(dateStr);
+            System.out.println("Successfully Parsed Date " + date);
+        } catch (ParseException e) {
+            System.out.println("ParseError " + e.getMessage());
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/commonissues/SynchronizedCounter.java

@@ -0,0 +1,13 @@
+package com.baeldung.commonissues;
+
+class SynchronizedCounter {
+    private int counter = 0;
+
+    public synchronized void increment() {
+        counter++;
+    }
+
+    public synchronized int getValue() {
+        return counter;
+    }
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/commonissues/SynchronizedVolatileCounter.java

@@ -0,0 +1,13 @@
+package com.baeldung.commonissues;
+
+class SynchronizedVolatileCounter {
+    private volatile int counter = 0;
+
+    public synchronized void increment() {
+        counter++;
+    }
+
+    public int getValue() {
+        return counter;
+    }
+}