Merge pull request #10 from eugenp/master

Pulling latest changes

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

@@ -28,14 +28,14 @@ public class Log {
                 System.out.println("Had " + count + " commits overall on current branch");
 
                 logs = git.log()
-                        .add(repository.resolve("remotes/origin/testbranch"))
+                        .add(repository.resolve(git.getRepository().getFullBranch()))
                         .call();
                 count = 0;
                 for (RevCommit rev : logs) {
                     System.out.println("Commit: " + rev /* + ", name: " + rev.getName() + ", id: " + rev.getId().getName() */);
                     count++;
                 }
-                System.out.println("Had " + count + " commits overall on test-branch");
+                System.out.println("Had " + count + " commits overall on "+git.getRepository().getFullBranch());
 
                 logs = git.log()
                         .all()

JGit/src/test/java/com/baeldung/jgit/JGitBugIntegrationTest.java

@@ -1,3 +1,5 @@
+package com.baeldung.jgit;
+
 import com.baeldung.jgit.helper.Helper;
 import org.eclipse.jgit.lib.ObjectLoader;
 import org.eclipse.jgit.lib.ObjectReader;

akka-http/pom.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0"?>
+<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>
+
+	<parent>
+		<artifactId>parent-modules</artifactId>
+		<groupId>com.baeldung</groupId>
+		<version>1.0.0-SNAPSHOT</version>
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-http_2.12</artifactId>
+			<version>${akka.http.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-stream_2.12</artifactId>
+			<version>2.5.11</version>
+		</dependency>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-http-jackson_2.12</artifactId>
+			<version>${akka.http.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>com.typesafe.akka</groupId>
+			<artifactId>akka-http-testkit_2.12</artifactId>
+			<version>${akka.http.version}</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+		<java.version>1.8</java.version>
+		<akka.http.version>10.0.11</akka.http.version>
+		<akka.stream.version>2.5.11</akka.stream.version>
+	</properties>
+</project>

akka-http/src/main/java/com/baeldung/akkahttp/User.java

@@ -0,0 +1,26 @@
+package com.baeldung.akkahttp;
+
+public class User {
+
+    private final Long id;
+
+    private final String name;
+
+    public User() {
+        this.name = "";
+        this.id = null;
+    }
+
+    public User(Long id, String name) {
+        this.name = name;
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Long getId() {
+        return id;
+    }
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserActor.java

@@ -0,0 +1,41 @@
+package com.baeldung.akkahttp;
+
+import akka.actor.AbstractActor;
+import akka.actor.Props;
+import akka.japi.pf.FI;
+import com.baeldung.akkahttp.UserMessages.ActionPerformed;
+import com.baeldung.akkahttp.UserMessages.CreateUserMessage;
+import com.baeldung.akkahttp.UserMessages.GetUserMessage;
+
+
+class UserActor extends AbstractActor {
+
+  private UserService userService = new UserService();
+
+  static Props props() {
+    return Props.create(UserActor.class);
+  }
+
+  @Override
+  public Receive createReceive() {
+    return receiveBuilder()
+            .match(CreateUserMessage.class, handleCreateUser())
+            .match(GetUserMessage.class, handleGetUser())
+            .build();
+  }
+
+  private FI.UnitApply<CreateUserMessage> handleCreateUser() {
+    return createUserMessageMessage -> {
+      userService.createUser(createUserMessageMessage.getUser());
+      sender().tell(new ActionPerformed(String.format("User %s created.", createUserMessageMessage.getUser()
+              .getName())), getSelf());
+    };
+  }
+
+  private FI.UnitApply<GetUserMessage> handleGetUser() {
+    return getUserMessageMessage -> {
+      sender().tell(userService.getUser(getUserMessageMessage.getUserId()), getSelf());
+    };
+  }
+
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserMessages.java

@@ -0,0 +1,49 @@
+package com.baeldung.akkahttp;
+
+import java.io.Serializable;
+
+public interface UserMessages {
+
+  class ActionPerformed implements Serializable {
+
+    private static final long serialVersionUID = 1L;
+
+    private final String description;
+
+    public ActionPerformed(String description) {
+      this.description = description;
+    }
+
+    public String getDescription() {
+      return description;
+    }
+  }
+
+  class CreateUserMessage implements Serializable {
+
+    private static final long serialVersionUID = 1L;
+    private final User user;
+
+    public CreateUserMessage(User user) {
+      this.user = user;
+    }
+
+    public User getUser() {
+      return user;
+    }
+  }
+
+  class GetUserMessage implements Serializable {
+    private static final long serialVersionUID = 1L;
+    private final Long userId;
+
+    public GetUserMessage(Long userId) {
+      this.userId = userId;
+    }
+
+    public Long getUserId() {
+      return userId;
+    }
+  }
+
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserServer.java

@@ -0,0 +1,70 @@
+package com.baeldung.akkahttp;
+
+import java.util.Optional;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.TimeUnit;
+
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.http.javadsl.marshallers.jackson.Jackson;
+import akka.http.javadsl.model.StatusCodes;
+import akka.http.javadsl.server.HttpApp;
+import akka.http.javadsl.server.Route;
+import akka.pattern.PatternsCS;
+import akka.util.Timeout;
+import com.baeldung.akkahttp.UserMessages.ActionPerformed;
+import com.baeldung.akkahttp.UserMessages.CreateUserMessage;
+import com.baeldung.akkahttp.UserMessages.GetUserMessage;
+import scala.concurrent.duration.Duration;
+import static akka.http.javadsl.server.PathMatchers.*;
+
+class UserServer extends HttpApp {
+
+  private final ActorRef userActor;
+
+  Timeout timeout = new Timeout(Duration.create(5, TimeUnit.SECONDS));
+
+  UserServer(ActorRef userActor) {
+    this.userActor = userActor;
+  }
+
+  @Override
+  public Route routes() {
+    return path("users", this::postUser)
+            .orElse(path(segment("users").slash(longSegment()), id ->
+                    route(getUser(id))));
+  }
+
+  private Route getUser(Long id) {
+    return get(() -> {
+      CompletionStage<Optional<User>> user = PatternsCS.ask(userActor, new GetUserMessage(id), timeout)
+              .thenApply(obj -> (Optional<User>) obj);
+
+      return onSuccess(() -> user, performed -> {
+        if (performed.isPresent())
+          return complete(StatusCodes.OK, performed.get(), Jackson.marshaller());
+        else
+          return complete(StatusCodes.NOT_FOUND);
+      });
+    });
+  }
+
+  private Route postUser() {
+    return route(post(() -> entity(Jackson.unmarshaller(User.class), user -> {
+      CompletionStage<ActionPerformed> userCreated = PatternsCS.ask(userActor, new CreateUserMessage(user), timeout)
+              .thenApply(obj -> (ActionPerformed) obj);
+
+      return onSuccess(() -> userCreated, performed -> {
+        return complete(StatusCodes.CREATED, performed, Jackson.marshaller());
+      });
+    })));
+  }
+
+  public static void main(String[] args) throws Exception {
+    ActorSystem system = ActorSystem.create("userServer");
+    ActorRef userActor = system.actorOf(UserActor.props(), "userActor");
+    UserServer server = new UserServer(userActor);
+    server.startServer("localhost", 8080, system);
+  }
+
+}

akka-http/src/main/java/com/baeldung/akkahttp/UserService.java

@@ -0,0 +1,35 @@
+package com.baeldung.akkahttp;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+public class UserService {
+
+  private final static List<User> users = new ArrayList<>();
+
+  static {
+    users.add(new User(1l, "Alice"));
+    users.add(new User(2l, "Bob"));
+    users.add(new User(3l, "Chris"));
+    users.add(new User(4l, "Dick"));
+    users.add(new User(5l, "Eve"));
+    users.add(new User(6l, "Finn"));
+  }
+
+  public Optional<User> getUser(Long id) {
+    return users.stream()
+            .filter(user -> user.getId()
+                    .equals(id))
+            .findFirst();
+  }
+
+  public void createUser(User user) {
+    users.add(user);
+  }
+
+  public List<User> getUsers(){
+    return users;
+  }
+
+}

akka-http/src/test/java/com/baeldung/akkahttp/UserServerUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.akkahttp;
+
+import akka.actor.ActorRef;
+import akka.actor.ActorSystem;
+import akka.http.javadsl.model.ContentTypes;
+import akka.http.javadsl.model.HttpEntities;
+import akka.http.javadsl.model.HttpRequest;
+import akka.http.javadsl.testkit.JUnitRouteTest;
+import akka.http.javadsl.testkit.TestRoute;
+import org.junit.Test;
+
+public class UserServerUnitTest extends JUnitRouteTest {
+
+  ActorSystem system = ActorSystem.create("helloAkkaHttpServer");
+
+  ActorRef userActorRef = system.actorOf(UserActor.props(), "userActor");
+
+  TestRoute appRoute = testRoute(new UserServer(userActorRef).routes());
+
+  @Test
+  public void whenRequest_thenActorResponds() {
+
+    appRoute.run(HttpRequest.GET("/users/1"))
+            .assertEntity(alice())
+            .assertStatusCode(200);
+
+    appRoute.run(HttpRequest.GET("/users/42"))
+            .assertStatusCode(404);
+
+    appRoute.run(HttpRequest.DELETE("/users/1"))
+            .assertStatusCode(200);
+
+    appRoute.run(HttpRequest.DELETE("/users/42"))
+            .assertStatusCode(200);
+
+    appRoute.run(HttpRequest.POST("/users")
+            .withEntity(HttpEntities.create(ContentTypes.APPLICATION_JSON, zaphod())))
+            .assertStatusCode(201);
+
+  }
+
+  private String alice() {
+    return "{\"id\":1,\"name\":\"Alice\"}";
+  }
+
+  private String zaphod() {
+    return "{\"id\":42,\"name\":\"Zaphod\"}";
+  }
+
+}

algorithms-miscellaneous-1/README.md

@@ -10,4 +10,6 @@
 - [Multi-Swarm Optimization Algorithm in Java](http://www.baeldung.com/java-multi-swarm-algorithm)
 - [String Search Algorithms for Large Texts](http://www.baeldung.com/java-full-text-search-algorithms)
 - [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](http://www.baeldung.com/java-linked-list-middle-element)
+- [Find the Middle Element of a Linked List](http://www.baeldung.com/java-linked-list-middle-element)
+- [Calculate Factorial in Java](https://www.baeldung.com/java-calculate-factorial)
+- [Find Substrings That Are Palindromes in Java](https://www.baeldung.com/java-palindrome-substrings)

algorithms-miscellaneous-1/pom.xml

@@ -17,6 +17,11 @@
             <artifactId>commons-math3</artifactId>
             <version>${commons-math3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
         <dependency>
             <groupId>commons-codec</groupId>
             <artifactId>commons-codec</artifactId>
@@ -73,6 +78,7 @@
         <commons-math3.version>3.6.1</commons-math3.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
+        <guava.version>25.1-jre</guava.version>
     </properties>
 
 </project>

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/factorial/Factorial.java

@@ -0,0 +1,63 @@
+package com.baeldung.algorithms.factorial;
+
+import java.math.BigInteger;
+import java.util.stream.LongStream;
+
+import org.apache.commons.math3.util.CombinatoricsUtils;
+
+import com.google.common.math.BigIntegerMath;
+
+public class Factorial {
+
+    public long factorialUsingForLoop(int n) {
+        long fact = 1;
+        for (int i = 2; i <= n; i++) {
+            fact = fact * i;
+        }
+        return fact;
+    }
+
+    public long factorialUsingStreams(int n) {
+        return LongStream.rangeClosed(1, n)
+            .reduce(1, (long x, long y) -> x * y);
+    }
+
+    public long factorialUsingRecursion(int n) {
+        if (n <= 2) {
+            return n;
+        }
+        return n * factorialUsingRecursion(n - 1);
+    }
+
+    private Long[] factorials = new Long[20];
+
+    public long factorialUsingMemoize(int n) {
+
+        if (factorials[n] != null) {
+            return factorials[n];
+        }
+
+        if (n <= 2) {
+            return n;
+        }
+        long nthValue = n * factorialUsingMemoize(n - 1);
+        factorials[n] = nthValue;
+        return nthValue;
+    }
+
+    public BigInteger factorialHavingLargeResult(int n) {
+        BigInteger result = BigInteger.ONE;
+        for (int i = 2; i <= n; i++)
+            result = result.multiply(BigInteger.valueOf(i));
+        return result;
+    }
+
+    public long factorialUsingApacheCommons(int n) {
+        return CombinatoricsUtils.factorial(n);
+    }
+
+    public BigInteger factorialUsingGuava(int n) {
+        return BigIntegerMath.factorial(n);
+    }
+
+}

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharacters.java

@@ -0,0 +1,54 @@
+package com.baeldung.algorithms.string;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public class LongestSubstringNonRepeatingCharacters {
+
+    public static String getUniqueCharacterSubstringBruteForce(String input) {
+        String output = "";
+        for (int start = 0; start < input.length(); start++) {
+            Set<Character> visited = new HashSet<>();
+            int end = start;
+            for (; end < input.length(); end++) {
+                char currChar = input.charAt(end);
+                if (visited.contains(currChar)) {
+                    break;
+                } else {
+                    visited.add(currChar);
+                }
+            }
+            if (output.length() < end - start + 1) {
+                output = input.substring(start, end);
+            }
+        }
+        return output;
+    }
+
+    public static String getUniqueCharacterSubstring(String input) {
+        Map<Character, Integer> visited = new HashMap<>();
+        String output = "";
+        for (int start = 0, end = 0; end < input.length(); end++) {
+            char currChar = input.charAt(end);
+            if (visited.containsKey(currChar)) {
+                start = Math.max(visited.get(currChar) + 1, start);
+            }
+            if (output.length() < end - start + 1) {
+                output = input.substring(start, end + 1);
+            }
+            visited.put(currChar, end);
+        }
+        return output;
+    }
+
+    public static void main(String[] args) {
+        if(args.length > 0) {
+            System.out.println(getUniqueCharacterSubstring(args[0]));
+        } else {
+            System.err.println("This program expects command-line input. Please try again!");
+        }
+    }
+
+}

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/string/SubstringPalindrome.java

@@ -0,0 +1,90 @@
+package com.baeldung.algorithms.string;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class SubstringPalindrome {
+
+    public Set<String> findAllPalindromesUsingCenter(String input) {
+        final Set<String> palindromes = new HashSet<>();
+        if (input == null || input.isEmpty()) {
+            return palindromes;
+        }
+        if (input.length() == 1) {
+            palindromes.add(input);
+            return palindromes;
+        }
+        for (int i = 0; i < input.length(); i++) {
+            palindromes.addAll(findPalindromes(input, i, i + 1));
+            palindromes.addAll(findPalindromes(input, i, i));
+        }
+        return palindromes;
+    }
+
+    private Set<String> findPalindromes(String input, int low, int high) {
+        Set<String> result = new HashSet<>();
+        while (low >= 0 && high < input.length() && input.charAt(low) == input.charAt(high)) {
+            result.add(input.substring(low, high + 1));
+            low--;
+            high++;
+        }
+        return result;
+    }
+
+    public Set<String> findAllPalindromesUsingBruteForceApproach(String input) {
+        Set<String> palindromes = new HashSet<>();
+        if (input == null || input.isEmpty()) {
+            return palindromes;
+        }
+        if (input.length() == 1) {
+            palindromes.add(input);
+            return palindromes;
+        }
+        for (int i = 0; i < input.length(); i++) {
+            for (int j = i + 1; j <= input.length(); j++)
+                if (isPalindrome(input.substring(i, j))) {
+                    palindromes.add(input.substring(i, j));
+                }
+        }
+        return palindromes;
+    }
+
+    private boolean isPalindrome(String input) {
+        StringBuilder plain = new StringBuilder(input);
+        StringBuilder reverse = plain.reverse();
+        return (reverse.toString()).equals(input);
+    }
+
+    public Set<String> findAllPalindromesUsingManachersAlgorithm(String input) {
+        Set<String> palindromes = new HashSet<>();
+        String formattedInput = "@" + input + "#";
+        char inputCharArr[] = formattedInput.toCharArray();
+        int max;
+        int radius[][] = new int[2][input.length() + 1];
+        for (int j = 0; j <= 1; j++) {
+            radius[j][0] = max = 0;
+            int i = 1;
+            while (i <= input.length()) {
+                palindromes.add(Character.toString(inputCharArr[i]));
+                while (inputCharArr[i - max - 1] == inputCharArr[i + j + max])
+                    max++;
+                radius[j][i] = max;
+                int k = 1;
+                while ((radius[j][i - k] != max - k) && (k < max)) {
+                    radius[j][i + k] = Math.min(radius[j][i - k], max - k);
+                    k++;
+                }
+                max = Math.max(max - k, 0);
+                i += k;
+            }
+        }
+        for (int i = 1; i <= input.length(); i++) {
+            for (int j = 0; j <= 1; j++) {
+                for (max = radius[j][i]; max > 0; max--) {
+                    palindromes.add(input.substring(i - max - 1, max + j + i - 1));
+                }
+            }
+        }
+        return palindromes;
+    }
+}

algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/factorial/FactorialUnitTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.algorithms.factorial;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.math.BigInteger;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class FactorialUnitTest {
+
+    Factorial factorial;
+
+    @Before
+    public void setup() {
+        factorial = new Factorial();
+    }
+
+    @Test
+    public void whenCalculatingFactorialUsingForLoop_thenCorrect() {
+        int n = 5;
+
+        assertThat(factorial.factorialUsingForLoop(n)).isEqualTo(120);
+    }
+
+    @Test
+    public void whenCalculatingFactorialUsingStreams_thenCorrect() {
+        int n = 5;
+
+        assertThat(factorial.factorialUsingStreams(n)).isEqualTo(120);
+    }
+
+    @Test
+    public void whenCalculatingFactorialUsingRecursion_thenCorrect() {
+        int n = 5;
+
+        assertThat(factorial.factorialUsingRecursion(n)).isEqualTo(120);
+    }
+
+    @Test
+    public void whenCalculatingFactorialUsingMemoize_thenCorrect() {
+        int n = 5;
+
+        assertThat(factorial.factorialUsingMemoize(n)).isEqualTo(120);
+
+        n = 6;
+
+        assertThat(factorial.factorialUsingMemoize(n)).isEqualTo(720);
+    }
+
+    @Test
+    public void whenCalculatingFactorialHavingLargeResult_thenCorrect() {
+        int n = 22;
+
+        assertThat(factorial.factorialHavingLargeResult(n)).isEqualTo(new BigInteger("1124000727777607680000"));
+    }
+
+    @Test
+    public void whenCalculatingFactorialUsingApacheCommons_thenCorrect() {
+        int n = 5;
+
+        assertThat(factorial.factorialUsingApacheCommons(n)).isEqualTo(120);
+    }
+
+    @Test
+    public void whenCalculatingFactorialUsingGuava_thenCorrect() {
+        int n = 22;
+
+        assertThat(factorial.factorialUsingGuava(n)).isEqualTo(new BigInteger("1124000727777607680000"));
+    }
+
+}

algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharactersUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.algorithms.string;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static com.baeldung.algorithms.string.LongestSubstringNonRepeatingCharacters.getUniqueCharacterSubstring;
+import static com.baeldung.algorithms.string.LongestSubstringNonRepeatingCharacters.getUniqueCharacterSubstringBruteForce;
+
+public class LongestSubstringNonRepeatingCharactersUnitTest {
+
+    @Test
+    void givenString_whenGetUniqueCharacterSubstringBruteForceCalled_thenResultFoundAsExpectedUnitTest() {
+        assertEquals("", getUniqueCharacterSubstringBruteForce(""));
+        assertEquals("A", getUniqueCharacterSubstringBruteForce("A"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstringBruteForce("AABCDEF"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstringBruteForce("ABCDEFF"));
+        assertEquals("NGISAWE", getUniqueCharacterSubstringBruteForce("CODINGISAWESOME"));
+        assertEquals("be coding", getUniqueCharacterSubstringBruteForce("always be coding"));
+    }
+
+    @Test
+    void givenString_whenGetUniqueCharacterSubstringCalled_thenResultFoundAsExpectedUnitTest() {
+        assertEquals("", getUniqueCharacterSubstring(""));
+        assertEquals("A", getUniqueCharacterSubstring("A"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstring("AABCDEF"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstring("ABCDEFF"));
+        assertEquals("NGISAWE", getUniqueCharacterSubstring("CODINGISAWESOME"));
+        assertEquals("be coding", getUniqueCharacterSubstring("always be coding"));
+    }
+
+}

algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/string/SubstringPalindromeUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.algorithms.string;
+
+import static org.junit.Assert.assertEquals;
+import java.util.HashSet;
+import java.util.Set;
+import org.junit.Test;
+
+public class SubstringPalindromeUnitTest {
+
+    private static final String INPUT_BUBBLE = "bubble";
+    private static final String INPUT_CIVIC = "civic";
+    private static final String INPUT_INDEED = "indeed";
+    private static final String INPUT_ABABAC = "ababac";
+
+    Set<String> EXPECTED_PALINDROME_BUBBLE = new HashSet<String>() {
+        {
+            add("b");
+            add("u");
+            add("l");
+            add("e");
+            add("bb");
+            add("bub");
+        }
+    };
+
+    Set<String> EXPECTED_PALINDROME_CIVIC = new HashSet<String>() {
+        {
+            add("civic");
+            add("ivi");
+            add("i");
+            add("c");
+            add("v");
+        }
+    };
+
+    Set<String> EXPECTED_PALINDROME_INDEED = new HashSet<String>() {
+        {
+            add("i");
+            add("n");
+            add("d");
+            add("e");
+            add("ee");
+            add("deed");
+        }
+    };
+
+    Set<String> EXPECTED_PALINDROME_ABABAC = new HashSet<String>() {
+        {
+            add("a");
+            add("b");
+            add("c");
+            add("aba");
+            add("bab");
+            add("ababa");
+        }
+    };
+
+    private SubstringPalindrome palindrome = new SubstringPalindrome();
+
+    @Test
+    public void whenUsingManachersAlgorithm_thenFindsAllPalindromes() {
+        assertEquals(EXPECTED_PALINDROME_BUBBLE, palindrome.findAllPalindromesUsingManachersAlgorithm(INPUT_BUBBLE));
+        assertEquals(EXPECTED_PALINDROME_INDEED, palindrome.findAllPalindromesUsingManachersAlgorithm(INPUT_INDEED));
+        assertEquals(EXPECTED_PALINDROME_CIVIC, palindrome.findAllPalindromesUsingManachersAlgorithm(INPUT_CIVIC));
+        assertEquals(EXPECTED_PALINDROME_ABABAC, palindrome.findAllPalindromesUsingManachersAlgorithm(INPUT_ABABAC));
+    }
+
+    @Test
+    public void whenUsingCenterApproach_thenFindsAllPalindromes() {
+        assertEquals(EXPECTED_PALINDROME_BUBBLE, palindrome.findAllPalindromesUsingCenter(INPUT_BUBBLE));
+        assertEquals(EXPECTED_PALINDROME_INDEED, palindrome.findAllPalindromesUsingCenter(INPUT_INDEED));
+        assertEquals(EXPECTED_PALINDROME_CIVIC, palindrome.findAllPalindromesUsingCenter(INPUT_CIVIC));
+        assertEquals(EXPECTED_PALINDROME_ABABAC, palindrome.findAllPalindromesUsingCenter(INPUT_ABABAC));
+    }
+
+    @Test
+    public void whenUsingBruteForceApproach_thenFindsAllPalindromes() {
+        assertEquals(EXPECTED_PALINDROME_BUBBLE, palindrome.findAllPalindromesUsingBruteForceApproach(INPUT_BUBBLE));
+        assertEquals(EXPECTED_PALINDROME_INDEED, palindrome.findAllPalindromesUsingBruteForceApproach(INPUT_INDEED));
+        assertEquals(EXPECTED_PALINDROME_CIVIC, palindrome.findAllPalindromesUsingBruteForceApproach(INPUT_CIVIC));
+        assertEquals(EXPECTED_PALINDROME_ABABAC, palindrome.findAllPalindromesUsingBruteForceApproach(INPUT_ABABAC));
+    }
+}

algorithms-miscellaneous-2/pom.xml

@@ -33,6 +33,11 @@
             <artifactId>jgrapht-core</artifactId>
             <version>${org.jgrapht.core.version}</version>
         </dependency>
+        <dependency>
+        	<groupId>org.jgrapht</groupId>
+        	<artifactId>jgrapht-ext</artifactId>
+        	<version>${org.jgrapht.ext.version}</version>
+        </dependency>
         <dependency>
             <groupId>pl.allegro.finance</groupId>
             <artifactId>tradukisto</artifactId>
@@ -83,6 +88,7 @@
         <commons-math3.version>3.6.1</commons-math3.version>
         <tradukisto.version>1.0.1</tradukisto.version>
         <org.jgrapht.core.version>1.0.1</org.jgrapht.core.version>
+        <org.jgrapht.ext.version>1.0.1</org.jgrapht.ext.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
     </properties>

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

@@ -0,0 +1,47 @@
+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.Before;
+import org.junit.Test;
+import com.mxgraph.layout.mxCircleLayout;
+import com.mxgraph.layout.mxIGraphLayout;
+import com.mxgraph.util.mxCellRenderer;
+
+public class GraphImageGenerationUnitTest {
+    static DefaultDirectedGraph<String, DefaultEdge> g;
+
+    @Before
+    public void createGraph() throws IOException {
+        File imgFile = new File("src/test/resources/graph.png");
+        imgFile.createNewFile();
+        g = new DefaultDirectedGraph<String, DefaultEdge>(DefaultEdge.class);
+        String x1 = "x1";
+        String x2 = "x2";
+        String x3 = "x3";
+        g.addVertex(x1);
+        g.addVertex(x2);
+        g.addVertex(x3);
+        g.addEdge(x1, x2);
+        g.addEdge(x2, x3);
+        g.addEdge(x3, x1);
+    }
+
+    @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");
+        BufferedImage image = mxCellRenderer.createBufferedImage(graphAdapter, null, 2, Color.WHITE, true, null);
+        ImageIO.write(image, "PNG", imgFile);
+        assertTrue(imgFile.exists());
+    }
+}

algorithms-sorting/src/main/java/com/baeldung/algorithms/mergesort/MergeSort.java

@@ -34,7 +34,7 @@ public class MergeSort {
 
         while (i < left && j < right) {
 
-            if (l[i] < r[j])
+            if (l[i] <= r[j])
                 a[k++] = l[i++];
             else
                 a[k++] = r[j++];

apache-curator/pom.xml

@@ -59,7 +59,7 @@
     <properties>
         <curator.version>4.0.1</curator.version>
         <zookeeper.version>3.4.11</zookeeper.version>
-        <jackson-databind.version>2.9.4</jackson-databind.version>
+        <jackson-databind.version>2.9.7</jackson-databind.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <avaitility.version>1.7.0</avaitility.version>

core-java-11/README.md

@@ -0,0 +1,5 @@
+### Relevant articles
+
+- [Java 11 Single File Source Code](https://www.baeldung.com/java-single-file-source-code)
+- [Java 11 Local Variable Syntax for Lambda Parameters](https://www.baeldung.com/java-var-lambda-params)
+

core-java-11/src/main/java/com/baeldung/Outer.java

@@ -0,0 +1,24 @@
+package com.baeldung;
+
+import java.lang.reflect.Method;
+
+public class Outer {
+
+    public void outerPublic() {
+    }
+
+    private void outerPrivate() {
+    }
+
+    class Inner {
+
+        public void innerPublic() {
+            outerPrivate();
+        }
+
+        public void innerPublicReflection(Outer ob) throws Exception {
+            Method method = ob.getClass().getDeclaredMethod("outerPrivate");
+            method.invoke(ob);
+        }
+    }
+}

core-java-11/src/main/java/com/baeldung/add

@@ -0,0 +1,12 @@
+#!/usr/local/bin/java --source 11
+
+import java.util.Arrays;
+
+public class Addition
+{
+    public static void main(String[] args) {
+        System.out.println(Arrays.stream(args)
+          .mapToInt(Integer::parseInt)
+          .sum());
+    }
+}

core-java-11/src/test/java/com/baeldung/NewStringAPIUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung;
+
+import static org.hamcrest.CoreMatchers.is;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class NewStringAPIUnitTest {
+
+    @Test
+    public void whenRepeatStringTwice_thenGetStringTwice() {
+        String output = "La ".repeat(2) + "Land";
+
+        is(output).equals("La La Land");
+    }
+
+    @Test
+    public void whenStripString_thenReturnStringWithoutWhitespaces() {
+        is("\n\t  hello   \u2005".strip()).equals("hello");
+    }
+
+    @Test
+    public void whenTrimAdvanceString_thenReturnStringWithWhitespaces() {
+        is("\n\t  hello   \u2005".trim()).equals("hello   \u2005");
+    }
+
+    @Test
+    public void whenBlankString_thenReturnTrue() {
+        assertTrue("\n\t\u2005  ".isBlank());
+    }
+
+    @Test
+    public void whenMultilineString_thenReturnNonEmptyLineCount() {
+        String multilineStr = "This is\n \n a multiline\n string.";
+
+        long lineCount = multilineStr.lines()
+          .filter(String::isBlank)
+          .count();
+
+        is(lineCount).equals(3L);
+    }
+}

core-java-11/src/test/java/com/baeldung/OuterUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung;
+
+import static org.junit.Assert.assertTrue;
+import static org.hamcrest.CoreMatchers.is;
+
+import java.util.Arrays;
+import java.util.Set;
+import java.util.stream.Collectors;
+import org.junit.Test;
+
+public class OuterUnitTest {
+
+    private static final String NEST_HOST_NAME = "com.baeldung.Outer";
+
+    @Test
+    public void whenGetNestHostFromOuter_thenGetNestHost() {
+        is(Outer.class.getNestHost().getName()).equals(NEST_HOST_NAME);
+    }
+
+    @Test
+    public void whenGetNestHostFromInner_thenGetNestHost() {
+        is(Outer.Inner.class.getNestHost().getName()).equals(NEST_HOST_NAME);
+    }
+
+    @Test
+    public void whenCheckNestmatesForNestedClasses_thenGetTrue() {
+        is(Outer.Inner.class.isNestmateOf(Outer.class)).equals(true);
+    }
+
+    @Test
+    public void whenCheckNestmatesForUnrelatedClasses_thenGetFalse() {
+        is(Outer.Inner.class.isNestmateOf(Outer.class)).equals(false);
+    }
+
+    @Test
+    public void whenGetNestMembersForNestedClasses_thenGetAllNestedClasses() {
+        Set<String> nestMembers = Arrays.stream(Outer.Inner.class.getNestMembers())
+          .map(Class::getName)
+          .collect(Collectors.toSet());
+
+        is(nestMembers.size()).equals(2);
+
+        assertTrue(nestMembers.contains("com.baeldung.Outer"));
+        assertTrue(nestMembers.contains("com.baeldung.Outer$Inner"));
+    }
+}

core-java-11/src/test/java/com/baeldung/optional/OptionalUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.optional;
+
+import org.junit.Test;
+
+import java.util.Optional;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Unit tests for {@link Optional} in Java 11.
+ */
+public class OptionalUnitTest {
+
+    @Test
+    public void givenAnEmptyOptional_isEmpty_thenBehavesAsExpected() {
+        Optional<String> opt = Optional.of("Baeldung");
+        assertFalse(opt.isEmpty());
+
+        opt = Optional.ofNullable(null);
+        assertTrue(opt.isEmpty());
+    }
+}

core-java-8/README.md

@@ -15,7 +15,6 @@
 - [Guide to Java 8 Comparator.comparing()](http://www.baeldung.com/java-8-comparator-comparing)
 - [Guide To Java 8 Optional](http://www.baeldung.com/java-optional)
 - [Guide to the Java 8 forEach](http://www.baeldung.com/foreach-java)
-- [Java Base64 Encoding and Decoding](http://www.baeldung.com/java-base64-encode-and-decode)
 - [The Difference Between map() and flatMap()](http://www.baeldung.com/java-difference-map-and-flatmap)
 - [Static and Default Methods in Interfaces in Java](http://www.baeldung.com/java-static-default-methods)
 - [Efficient Word Frequency Calculator in Java](http://www.baeldung.com/java-word-frequency)

core-java-8/pom.xml

@@ -1,5 +1,5 @@
 <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">
+         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-8</artifactId>
@@ -104,6 +104,24 @@
             <artifactId>aspectjweaver</artifactId>
             <version>${asspectj.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.powermock</groupId>
+            <artifactId>powermock-module-junit4</artifactId>
+            <version>${powermock.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.powermock</groupId>
+            <artifactId>powermock-api-mockito2</artifactId>
+            <version>${powermock.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jmockit</groupId>
+            <artifactId>jmockit</artifactId>
+            <version>${jmockit.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
@@ -119,7 +137,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.1</version>
+                <version>${maven-compiler-plugin.version}</version>
                 <configuration>
                     <source>1.8</source>
                     <target>1.8</target>
@@ -142,6 +160,16 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>${maven-surefire-plugin.version}</version>
+                <configuration>
+                    <argLine>
+                        -javaagent:${settings.localRepository}/org/jmockit/jmockit/${jmockit.version}/jmockit-${jmockit.version}.jar
+                    </argLine>
+                    <disableXmlReport>true</disableXmlReport>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 
@@ -159,9 +187,14 @@
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <asspectj.version>1.8.9</asspectj.version>
+        <powermock.version>2.0.0-RC.4</powermock.version>
+        <jmockit.version>1.44</jmockit.version>
         <avaitility.version>1.7.0</avaitility.version>
         <jmh-core.version>1.19</jmh-core.version>
         <jmh-generator.version>1.19</jmh-generator.version>
         <spring-boot-maven-plugin.version>2.0.4.RELEASE</spring-boot-maven-plugin.version>
+        <!-- plugins -->
+        <maven-compiler-plugin.version>3.8.0</maven-compiler-plugin.version>
+        <maven-surefire-plugin.version>2.22.1</maven-surefire-plugin.version>
     </properties>
 </project>

core-java-8/src/main/java/com/baeldung/interfaces/Electronic.java

@@ -0,0 +1,22 @@
+package com.baeldung.interfaces;
+
+public interface Electronic {
+    //Constant variable
+    public static final String LED = "LED";
+
+    //Abstract method
+    public int getElectricityUse();
+
+    // Static method
+    public static boolean isEnergyEfficient(String electtronicType) {
+        if (electtronicType.equals(LED)) {
+            return true;
+        }
+        return false;
+    }
+
+    //Default method
+    public default void printDescription() {
+        System.out.println("Electronic Description");
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/Employee.java

@@ -0,0 +1,15 @@
+package com.baeldung.interfaces;
+
+public class Employee {
+
+    private double salary;
+
+    public double getSalary() {
+        return salary;
+    }
+
+    public void setSalary(double salary) {
+        this.salary = salary;
+    }
+
+}

core-java-8/src/main/java/com/baeldung/interfaces/EmployeeSalaryComparator.java

@@ -0,0 +1,18 @@
+package com.baeldung.interfaces;
+
+import java.util.Comparator;
+
+public class EmployeeSalaryComparator implements Comparator<Employee> {
+
+    @Override
+    public int compare(Employee employeeA, Employee employeeB) {
+
+        if(employeeA.getSalary() < employeeB.getSalary()){
+            return -1;
+        }else if(employeeA.getSalary() > employeeB.getSalary()){
+            return 1;
+        }else{
+            return 0;
+        }
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/HasColor.java

@@ -0,0 +1,5 @@
+package com.baeldung.interfaces;
+
+public interface HasColor {
+    public String getColor();
+}

core-java-8/src/main/java/com/baeldung/interfaces/Motorcycle.java

@@ -0,0 +1,10 @@
+package com.baeldung.interfaces;
+
+import com.baeldung.interfaces.multiinheritance.Transform;
+
+public class Motorcycle implements Transform {
+    @Override
+    public void transform() {
+        // Implementation
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/Truck.java

@@ -0,0 +1,8 @@
+package com.baeldung.interfaces;
+
+public class Truck extends Vehicle {
+    @Override
+    public void transform() {
+        // implementation
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/Vehicle.java

@@ -0,0 +1,6 @@
+package com.baeldung.interfaces;
+
+import com.baeldung.interfaces.multiinheritance.Transform;
+
+public abstract class Vehicle implements Transform {
+}

core-java-8/src/main/java/com/baeldung/interfaces/multiinheritance/Car.java

@@ -0,0 +1,13 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public class Car implements Fly, Transform {
+    @Override
+    public void fly() {
+        System.out.println("I can Fly!!");
+    }
+
+    @Override
+    public void transform() {
+        System.out.println("I can Transform!!");
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/multiinheritance/Fly.java

@@ -0,0 +1,5 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public abstract interface Fly{
+    void fly();
+}

core-java-8/src/main/java/com/baeldung/interfaces/multiinheritance/Transform.java

@@ -0,0 +1,10 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public interface Transform {
+
+    void transform();
+
+    default void printSpecs(){
+        System.out.println("Transform Specification");
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/multiinheritance/Vehicle.java

@@ -0,0 +1,13 @@
+package com.baeldung.interfaces.multiinheritance;
+
+public class Vehicle implements Fly, Transform {
+    @Override
+    public void fly() {
+        System.out.println("I can Fly!!");
+    }
+
+    @Override
+    public void transform() {
+        System.out.println("I can Transform!!");
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/polymorphysim/Circle.java

@@ -0,0 +1,25 @@
+package com.baeldung.interfaces.polymorphysim;
+
+public class Circle implements Shape {
+
+    private double radius;
+
+    public Circle(double radius){
+        this.radius = radius;
+    }
+
+    @Override
+    public String name() {
+        return "Circle";
+    }
+
+    @Override
+    public double area() {
+        return Math.PI * (radius * radius);
+    }
+
+    @Override
+    public String getColor() {
+        return "green";
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/polymorphysim/DisplayShape.java

@@ -0,0 +1,26 @@
+package com.baeldung.interfaces.polymorphysim;
+
+import java.util.ArrayList;
+
+public class DisplayShape {
+
+    private ArrayList<Shape> shapes;
+
+    public ArrayList<Shape> getShapes() {
+        return shapes;
+    }
+
+    public DisplayShape() {
+        shapes = new ArrayList<>();
+    }
+
+    public void add(Shape shape) {
+        shapes.add(shape);
+    }
+
+    public void display() {
+        for (Shape shape : shapes) {
+            System.out.println(shape.name() + " area: " + shape.area());
+        }
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/polymorphysim/FunctionalMain.java

@@ -0,0 +1,23 @@
+package com.baeldung.interfaces.polymorphysim;
+
+import java.util.function.Predicate;
+
+public class FunctionalMain {
+
+public static void main(String[] args) {
+    Shape circleShape = new Circle(2);
+    Shape squareShape = new Square(2);
+
+    DisplayShape DisplayShape = new DisplayShape();
+    DisplayShape.add(circleShape);
+    DisplayShape.add(squareShape);
+
+    Predicate<Shape> checkArea = (shape) -> shape.area() < 5;
+
+    for (Shape shape : DisplayShape.getShapes()) {
+        if (checkArea.test(shape)) {
+            System.out.println(shape.name() + " " + shape.area());
+        }
+    }
+}
+}

core-java-8/src/main/java/com/baeldung/interfaces/polymorphysim/MainPolymorphic.java

@@ -0,0 +1,15 @@
+package com.baeldung.interfaces.polymorphysim;
+
+public class MainPolymorphic {
+    public static void main(String[] args){
+
+        Shape circleShape = new Circle(2);
+        Shape squareShape = new Square(2);
+
+        DisplayShape displayShape = new DisplayShape();
+        displayShape.add(circleShape);
+        displayShape.add(squareShape);
+
+        displayShape.display();
+    }
+}

core-java-8/src/main/java/com/baeldung/interfaces/polymorphysim/Shape.java

@@ -0,0 +1,9 @@
+package com.baeldung.interfaces.polymorphysim;
+
+import com.baeldung.interfaces.HasColor;
+
+public interface Shape extends HasColor {
+
+    public abstract String name();
+    public abstract double area();
+}

core-java-8/src/main/java/com/baeldung/interfaces/polymorphysim/Square.java

@@ -0,0 +1,25 @@
+package com.baeldung.interfaces.polymorphysim;
+
+public class Square implements Shape {
+
+    private double width;
+
+    public Square(double width) {
+        this.width = width;
+    }
+
+    @Override
+    public String name() {
+        return "Square";
+    }
+
+    @Override
+    public double area() {
+        return width * width;
+    }
+
+    @Override
+    public String getColor() {
+        return "red";
+    }
+}

core-java-8/src/test/java/com/baeldung/interfaces/PolymorphysimUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.interfaces;
+
+import com.baeldung.interfaces.polymorphysim.Circle;
+import com.baeldung.interfaces.polymorphysim.Shape;
+import com.baeldung.interfaces.polymorphysim.Square;
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+public class PolymorphysimUnitTest {
+
+    @Test
+    public void whenInterfacePointsToCircle_CircleAreaMethodisBeingCalled(){
+        double expectedArea = 12.566370614359172;
+        Shape circle = new Circle(2);
+        double actualArea = circle.area();
+        Assertions.assertThat(actualArea).isEqualTo(expectedArea);
+    }
+
+    @Test
+    public void whenInterfacePointsToSquare_SquareAreaMethodisBeingCalled(){
+        double expectedArea = 4;
+        Shape square = new Square(2);
+        double actualArea = square.area();
+        Assertions.assertThat(actualArea).isEqualTo(expectedArea);
+    }
+}

core-java-8/src/test/java/com/baeldung/java8/Java8PredicateChainUnitTest.java

@@ -0,0 +1,131 @@
+package com.baeldung.java8;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.contains;
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+
+public class Java8PredicateChainUnitTest {
+    
+    private List<String> names = Arrays.asList("Adam", "Alexander", "John", "Tom");
+
+    @Test
+    public void whenFilterList_thenSuccess() {
+        List<String> result = names.stream()
+            .filter(name -> name.startsWith("A"))
+            .collect(Collectors.toList());
+
+        assertEquals(2, result.size());
+        assertThat(result, contains("Adam", "Alexander"));
+    }
+
+    @Test
+    public void whenFilterListWithMultipleFilters_thenSuccess() {
+        List<String> result = names.stream()
+            .filter(name -> name.startsWith("A"))
+            .filter(name -> name.length() < 5)
+            .collect(Collectors.toList());
+        
+        assertEquals(1, result.size());
+        assertThat(result, contains("Adam"));
+    }
+
+    @Test
+    public void whenFilterListWithComplexPredicate_thenSuccess() {
+        List<String> result = names.stream()
+            .filter(name -> name.startsWith("A") && name.length() < 5)
+            .collect(Collectors.toList());
+        
+        assertEquals(1, result.size());
+        assertThat(result, contains("Adam"));
+    }
+
+    @Test
+    public void whenFilterListWithCombinedPredicatesInline_thenSuccess() {
+        List<String> result = names.stream()
+            .filter(((Predicate<String>) name -> name.startsWith("A")).and(name -> name.length() < 5))
+            .collect(Collectors.toList());
+        
+        assertEquals(1, result.size());
+        assertThat(result, contains("Adam"));
+    }
+
+    @Test
+    public void whenFilterListWithCombinedPredicatesUsingAnd_thenSuccess() {
+        Predicate<String> predicate1 = str -> str.startsWith("A");
+        Predicate<String> predicate2 = str -> str.length() < 5;
+
+        List<String> result = names.stream()
+            .filter(predicate1.and(predicate2))
+            .collect(Collectors.toList());
+
+        assertEquals(1, result.size());
+        assertThat(result, contains("Adam"));
+    }
+
+    @Test
+    public void whenFilterListWithCombinedPredicatesUsingOr_thenSuccess() {
+        Predicate<String> predicate1 = str -> str.startsWith("J");
+        Predicate<String> predicate2 = str -> str.length() < 4;
+
+        List<String> result = names.stream()
+            .filter(predicate1.or(predicate2))
+            .collect(Collectors.toList());
+
+        assertEquals(2, result.size());
+        assertThat(result, contains("John", "Tom"));
+    }
+
+    @Test
+    public void whenFilterListWithCombinedPredicatesUsingOrAndNegate_thenSuccess() {
+        Predicate<String> predicate1 = str -> str.startsWith("J");
+        Predicate<String> predicate2 = str -> str.length() < 4;
+
+        List<String> result = names.stream()
+            .filter(predicate1.or(predicate2.negate()))
+            .collect(Collectors.toList());
+
+        assertEquals(3, result.size());
+        assertThat(result, contains("Adam", "Alexander", "John"));
+    }
+
+    @Test
+    public void whenFilterListWithCollectionOfPredicatesUsingAnd_thenSuccess() {
+        List<Predicate<String>> allPredicates = new ArrayList<Predicate<String>>();
+        allPredicates.add(str -> str.startsWith("A"));
+        allPredicates.add(str -> str.contains("d"));
+        allPredicates.add(str -> str.length() > 4);
+
+        List<String> result = names.stream()
+            .filter(allPredicates.stream()
+                .reduce(x -> true, Predicate::and))
+            .collect(Collectors.toList());
+
+        assertEquals(1, result.size());
+        assertThat(result, contains("Alexander"));
+    }
+
+    @Test
+    public void whenFilterListWithCollectionOfPredicatesUsingOr_thenSuccess() {
+        List<Predicate<String>> allPredicates = new ArrayList<Predicate<String>>();
+        allPredicates.add(str -> str.startsWith("A"));
+        allPredicates.add(str -> str.contains("d"));
+        allPredicates.add(str -> str.length() > 4);
+
+        List<String> result = names.stream()
+            .filter(allPredicates.stream()
+                .reduce(x -> false, Predicate::or))
+            .collect(Collectors.toList());
+
+        assertEquals(2, result.size());
+        assertThat(result, contains("Adam", "Alexander"));
+    }
+
+}

core-java-8/src/test/java/com/baeldung/time/LocalDateTimeUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.time;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+
+import java.time.Clock;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+import static org.powermock.api.mockito.PowerMockito.mockStatic;
+
+@RunWith(PowerMockRunner.class)
+@PrepareForTest({ LocalDateTime.class })
+public class LocalDateTimeUnitTest {
+
+    @Test
+    public void givenLocalDateTimeMock_whenNow_thenGetFixedLocalDateTime() {
+        Clock clock = Clock.fixed(Instant.parse("2014-12-22T10:15:30.00Z"), ZoneId.of("UTC"));
+        LocalDateTime dateTime = LocalDateTime.now(clock);
+        mockStatic(LocalDateTime.class);
+        when(LocalDateTime.now()).thenReturn(dateTime);
+        String dateTimeExpected = "2014-12-22T10:15:30";
+
+        LocalDateTime now = LocalDateTime.now();
+
+        assertThat(now).isEqualTo(dateTimeExpected);
+    }
+
+    @Test
+    public void givenFixedClock_whenNow_thenGetFixedLocalDateTime() {
+        Clock clock = Clock.fixed(Instant.parse("2014-12-22T10:15:30.00Z"), ZoneId.of("UTC"));
+        String dateTimeExpected = "2014-12-22T10:15:30";
+
+        LocalDateTime dateTime = LocalDateTime.now(clock);
+
+        assertThat(dateTime).isEqualTo(dateTimeExpected);
+    }
+}

core-java-8/src/test/java/com/baeldung/time/LocalDateTimeWithJMockUnitTest.java

@@ -0,0 +1,48 @@
+package com.baeldung.time;
+
+import mockit.Expectations;
+import mockit.Mock;
+import mockit.MockUp;
+import org.junit.jupiter.api.Test;
+
+import java.time.Clock;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class LocalDateTimeWithJMockUnitTest {
+
+    @Test
+    public void givenLocalDateTimeWithJMock_whenNow_thenGetFixedLocalDateTime() {
+        Clock clock = Clock.fixed(Instant.parse("2014-12-21T10:15:30.00Z"), ZoneId.of("UTC"));
+        new MockUp<LocalDateTime>() {
+            @Mock
+            public LocalDateTime now() {
+                return LocalDateTime.now(clock);
+            }
+        };
+        String dateTimeExpected = "2014-12-21T10:15:30";
+
+        LocalDateTime now = LocalDateTime.now();
+
+        assertThat(now).isEqualTo(dateTimeExpected);
+    }
+
+    @Test
+    public void givenLocalDateTimeWithExpectations_whenNow_thenGetFixedLocalDateTime() {
+        Clock clock = Clock.fixed(Instant.parse("2014-12-23T10:15:30.00Z"), ZoneId.of("UTC"));
+        LocalDateTime dateTimeExpected = LocalDateTime.now(clock);
+        new Expectations(LocalDateTime.class) {
+            {
+                LocalDateTime.now();
+                result = dateTimeExpected;
+            }
+        };
+
+        LocalDateTime now = LocalDateTime.now();
+
+        assertThat(now).isEqualTo(dateTimeExpected);
+    }
+}

core-java-9/README.md

@@ -9,7 +9,6 @@
 - [Java 9 Convenience Factory Methods for Collections](http://www.baeldung.com/java-9-collections-factory-methods) 
 - [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
 - [Java 9 CompletableFuture API Improvements](http://www.baeldung.com/java-9-completablefuture)
-- [Spring Security – Redirect to the Previous URL After Login](http://www.baeldung.com/spring-security-redirect-login)
 - [Java 9 Process API Improvements](http://www.baeldung.com/java-9-process-api)
 - [Introduction to Java 9 StackWalking API](http://www.baeldung.com/java-9-stackwalking-api)
 - [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)

core-java-arrays/README.md

@@ -12,4 +12,4 @@
 - [Arrays in Java: A Reference Guide](https://www.baeldung.com/java-arrays-guide)
 - [How to Invert an Array in Java](http://www.baeldung.com/java-invert-array)
 - [Array Operations in Java](http://www.baeldung.com/java-common-array-operations)
-
+- [Intersection Between two Integer Arrays](https://www.baeldung.com/java-array-intersection)

core-java-arrays/src/main/java/com/baeldung/arraycopy/model/Employee.java

@@ -7,6 +7,14 @@ public class Employee implements Serializable {
     private int id;
     private String name;
 
+    public Employee() {
+    }
+
+    public Employee(int id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
     public int getId() {
         return id;
     }

core-java-arrays/src/test/java/com/baeldung/sort/ArraySortUnitTest.java

@@ -0,0 +1,90 @@
+package com.baeldung.sort;
+
+import com.baeldung.arraycopy.model.Employee;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class ArraySortUnitTest {
+    private Employee[] employees;
+    private int[] numbers;
+    private String[] strings;
+
+    private Employee john = new Employee(6, "John");
+    private Employee mary = new Employee(3, "Mary");
+    private Employee david = new Employee(4, "David");
+
+    @Before
+    public void setup() {
+        createEmployeesArray();
+        createNumbersArray();
+        createStringArray();
+    }
+
+    private void createEmployeesArray() {
+        employees = new Employee[]{john, mary, david};
+    }
+
+    private void createNumbersArray() {
+        numbers = new int[]{-8, 7, 5, 9, 10, -2, 3};
+    }
+
+    private void createStringArray() {
+        strings = new String[]{"learning", "java", "with", "baeldung"};
+    }
+
+    @Test
+    public void givenIntArray_whenSortingAscending_thenCorrectlySorted() {
+        Arrays.sort(numbers);
+
+        assertArrayEquals(new int[]{-8, -2, 3, 5, 7, 9, 10}, numbers);
+    }
+
+    @Test
+    public void givenIntArray_whenSortingDescending_thenCorrectlySorted() {
+        numbers = IntStream.of(numbers).boxed().sorted(Comparator.reverseOrder()).mapToInt(i -> i).toArray();
+
+        assertArrayEquals(new int[]{10, 9, 7, 5, 3, -2, -8}, numbers);
+    }
+
+    @Test
+    public void givenStringArray_whenSortingAscending_thenCorrectlySorted() {
+        Arrays.sort(strings);
+
+        assertArrayEquals(new String[]{"baeldung", "java", "learning", "with"}, strings);
+    }
+
+    @Test
+    public void givenStringArray_whenSortingDescending_thenCorrectlySorted() {
+        Arrays.sort(strings, Comparator.reverseOrder());
+
+        assertArrayEquals(new String[]{"with", "learning", "java", "baeldung"}, strings);
+    }
+
+    @Test
+    public void givenObjectArray_whenSortingAscending_thenCorrectlySorted() {
+        Arrays.sort(employees, Comparator.comparing(Employee::getName));
+
+        assertArrayEquals(new Employee[]{david, john, mary}, employees);
+    }
+
+    @Test
+    public void givenObjectArray_whenSortingDescending_thenCorrectlySorted() {
+        Arrays.sort(employees, Comparator.comparing(Employee::getName).reversed());
+
+        assertArrayEquals(new Employee[]{mary, john, david}, employees);
+    }
+
+    @Test
+    public void givenObjectArray_whenSortingMultipleAttributesAscending_thenCorrectlySorted() {
+        Arrays.sort(employees, Comparator.comparing(Employee::getName).thenComparing(Employee::getId));
+
+        assertArrayEquals(new Employee[]{david, john, mary}, employees);
+    }
+
+}

core-java-collections-list/README.md

@@ -0,0 +1,27 @@
+=========
+
+## Core Java Collections List Cookbooks and Examples
+
+### Relevant Articles: 
+- [Immutable ArrayList in Java](http://www.baeldung.com/java-immutable-list)
+- [Guide to the Java ArrayList](http://www.baeldung.com/java-arraylist)
+- [Random List Element](http://www.baeldung.com/java-random-list-element)
+- [Removing all nulls from a List in Java](http://www.baeldung.com/java-remove-nulls-from-list)
+- [Removing all duplicates from a List in Java](http://www.baeldung.com/java-remove-duplicates-from-list)
+- [How to TDD a List Implementation in Java](http://www.baeldung.com/java-test-driven-list)
+- [Iterating Backward Through a List](http://www.baeldung.com/java-list-iterate-backwards)
+- [Add Multiple Items to an Java ArrayList](http://www.baeldung.com/java-add-items-array-list)
+- [Remove the First Element from a List](http://www.baeldung.com/java-remove-first-element-from-list)
+- [How to Find an Element in a List with Java](http://www.baeldung.com/find-list-element-java)
+- [Copy a List to Another List in Java](http://www.baeldung.com/java-copy-list-to-another)
+- [Finding Max/Min of a List or Collection](http://www.baeldung.com/java-collection-min-max)
+- [Collections.emptyList() vs. New List Instance](https://www.baeldung.com/java-collections-emptylist-new-list)
+- [Remove All Occurrences of a Specific Value from a List](https://www.baeldung.com/java-remove-value-from-list)
+- [Check If Two Lists are Equal in Java](http://www.baeldung.com/java-test-a-list-for-ordinality-and-equality)
+- [Java 8 Streams: Find Items From One List Based On Values From Another List](https://www.baeldung.com/java-streams-find-list-items)
+- [A Guide to the Java LinkedList](http://www.baeldung.com/java-linkedlist)
+- [Java List UnsupportedOperationException](http://www.baeldung.com/java-list-unsupported-operation-exception)
+- [Java List Initialization in One Line](https://www.baeldung.com/java-init-list-one-line)
+- [Ways to Iterate Over a List in Java](https://www.baeldung.com/java-iterate-list)
+- [ClassCastException: Arrays$ArrayList cannot be cast to ArrayList](https://www.baeldung.com/java-classcastexception-arrays-arraylist)
+- [Flattening Nested Collections in Java](http://www.baeldung.com/java-flatten-nested-collections)

core-java-collections-list/pom.xml

@@ -0,0 +1,48 @@
+<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-collections-list</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
+    <name>core-java-collections-list</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <commons-collections4.version>4.1</commons-collections4.version>
+        <commons-lang3.version>3.8.1</commons-lang3.version>
+        <avaitility.version>1.7.0</avaitility.version>
+        <assertj.version>3.11.1</assertj.version>
+        <lombok.version>1.16.12</lombok.version>
+    </properties>
+</project>

core-java-collections-list/src/main/java/com/baeldung/list/multidimensional/ArrayListOfArrayList.java

@@ -0,0 +1,35 @@
+package com.baeldung.list.multidimensional;
+
+import java.util.ArrayList;
+
+public class ArrayListOfArrayList {
+
+    public static void main(String args[]) {
+
+        int numVertices = 3;
+        ArrayList<ArrayList<Integer>> graph = new ArrayList<>(numVertices);
+
+        //Initializing each element of ArrayList with ArrayList
+        for(int i=0; i< numVertices; i++) {
+            graph.add(new ArrayList<Integer>());
+        }
+
+        //We can add any number of columns to each row
+        graph.get(0).add(1);
+        graph.get(1).add(2);
+        graph.get(2).add(0);
+        graph.get(1).add(0);
+        graph.get(2).add(1);
+        graph.get(0).add(2);
+      
+        //Printing all the edges
+        for(int vertexNo=0; vertexNo<numVertices; vertexNo++) {
+            int edgeCount = graph.get(vertexNo).size();
+            ArrayList<Integer> listOfVertices = graph.get(vertexNo);
+            for(int i=0; i<edgeCount; i++) {
+                System.out.println("Vertex "+vertexNo+" is connected to vetex "+listOfVertices.get(i));
+            }
+        }
+    }
+
+}

core-java-collections-list/src/main/java/com/baeldung/list/multidimensional/ThreeDimensionalArrayList.java

@@ -0,0 +1,45 @@
+package com.baeldung.list.multidimensional;
+
+import java.util.ArrayList;
+
+public class ThreeDimensionalArrayList {
+
+    public static void main(String args[]) {
+        
+        int x_axis_length = 2;
+        int y_axis_length = 2;
+        int z_axis_length = 2;
+        ArrayList< ArrayList< ArrayList<String> > > space = new ArrayList<>(x_axis_length);
+
+        //Initializing each element of ArrayList with ArrayList< ArrayList<String> >
+        for(int i=0; i< x_axis_length; i++) {
+            space.add(new ArrayList< ArrayList<String> >(y_axis_length));
+            for(int j =0; j< y_axis_length; j++) {
+                space.get(i).add(new ArrayList<String>(z_axis_length));
+            }
+        }
+
+        //Set Red color for points (0,0,0) and (0,0,1)
+        space.get(0).get(0).add(0,"Red");
+        space.get(0).get(0).add(1,"Red");
+        //Set Blue color for points (0,1,0) and (0,1,1)
+        space.get(0).get(1).add(0,"Blue");
+        space.get(0).get(1).add(1,"Blue");
+        //Set Green color for points (1,0,0) and (1,0,1)
+        space.get(1).get(0).add(0,"Green");
+        space.get(1).get(0).add(1,"Green");
+        //Set Yellow color for points (1,1,0) and (1,1,1)
+        space.get(1).get(1).add(0,"Yellow");
+        space.get(1).get(1).add(1,"Yellow");
+
+        //Printing colors for all the points
+        for(int i=0; i<x_axis_length; i++) {
+            for(int j=0; j<y_axis_length; j++) {
+                for(int k=0; k<z_axis_length; k++) {
+                    System.out.println("Color of point ("+i+","+j+","+k+") is :"+space.get(i).get(j).get(k));
+                }
+            }
+        }
+    }
+
+}

core-java-collections-list/src/test/java/org/baeldung/RandomListElementUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung;
+package org.baeldung;
 
 import com.google.common.collect.Lists;
 import org.junit.Test;

core-java-collections-list/src/test/java/org/baeldung/java/lists/ListJUnitTest.java

@@ -0,0 +1,47 @@
+package org.baeldung.java.lists;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Set;
+import java.util.HashSet;
+
+import java.util.stream.Collectors;
+
+public class ListJUnitTest {
+
+    private final List<String> list1 = Arrays.asList("1", "2", "3", "4");
+    private final List<String> list2 = Arrays.asList("1", "2", "3", "4");
+    private final List<String> list3 = Arrays.asList("1", "2", "4", "3");
+
+    @Test
+    public void whenTestingForEquality_ShouldBeEqual() throws Exception {
+        Assert.assertEquals(list1, list2);
+        Assert.assertNotSame(list1, list2);
+        Assert.assertNotEquals(list1, list3);
+    }
+
+    @Test
+    public void whenIntersection_ShouldReturnCommonElements() throws Exception {
+        List<String> list = Arrays.asList("red", "blue", "blue", "green", "red");
+        List<String> otherList = Arrays.asList("red", "green", "green", "yellow");
+
+        Set<String> commonElements = new HashSet(Arrays.asList("red", "green"));
+
+        Set<String> result = list.stream()
+          .distinct()
+          .filter(otherList::contains)
+          .collect(Collectors.toSet());
+
+        Assert.assertEquals(commonElements, result);
+
+        Set<String> inverseResult = otherList.stream()
+          .distinct()
+          .filter(list::contains)
+          .collect(Collectors.toSet());
+
+        Assert.assertEquals(commonElements, inverseResult);
+    }
+}