Merge branch 'master' into master

algorithms/README.md

@@ -6,3 +6,5 @@
 - [Validating Input With Finite Automata in Java](http://www.baeldung.com/finite-automata-java)
 - [Introduction to Jenetics Library](http://www.baeldung.com/jenetics)
 - [Check If a Number Is Prime in Java](http://www.baeldung.com/java-prime-numbers)
+- [Example of Hill Climbing Algorithm](http://www.baeldung.com/java-hill-climbing-algorithm)
+- [Monte Carlo Tree Search for Tic-Tac-Toe Game](http://www.baeldung.com/java-monte-carlo-tree-search)

algorithms/src/main/java/com/baeldung/algorithms/BinarySearch.java

@@ -0,0 +1,53 @@
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+public class BinarySearch {
+
+    public int runBinarySearchIteratively(int[] sortedArray, int key, int low, int high) {
+
+        int index = Integer.MAX_VALUE;
+
+        while (low <= high) {
+
+            int mid = (low + high) / 2;
+
+            if (sortedArray[mid] < key) {
+                low = mid + 1;
+            } else if (sortedArray[mid] > key) {
+                high = mid - 1;
+            } else if (sortedArray[mid] == key) {
+                index = mid;
+                break;
+            }
+        }
+        return index;
+    }
+
+    public int runBinarySearchRecursively(int[] sortedArray, int key, int low, int high) {
+
+        int middle = (low + high) / 2;
+        if (high < low) {
+            return -1;
+        }
+
+        if (key == sortedArray[middle]) {
+          return middle;
+        } else if (key < sortedArray[middle]) {
+          return runBinarySearchRecursively(sortedArray, key, low, middle - 1);
+        } else {
+          return runBinarySearchRecursively(sortedArray, key, middle + 1, high);
+        }
+    }
+
+    public int runBinarySearchUsingJavaArrays(int[] sortedArray, Integer key) {
+        int index = Arrays.binarySearch(sortedArray, key);
+        return index;
+    }
+
+    public int runBinarySearchUsingJavaCollections(List<Integer> sortedList, Integer key) {
+        int index = Collections.binarySearch(sortedList, key);
+        return index;
+    }
+
+}

algorithms/src/main/java/com/baeldung/algorithms/minimax/MiniMax.java

@@ -18,12 +18,12 @@ public class MiniMax {
         constructTree(root);
     }
 
-    private void constructTree(Node node) {
+    private void constructTree(Node parentNode) {
-        List<Integer> listofPossibleHeaps = GameOfBones.getPossibleStates(node.getNoOfBones());
+        List<Integer> listofPossibleHeaps = GameOfBones.getPossibleStates(parentNode.getNoOfBones());
-        boolean isMaxPlayer = !node.isMaxPlayer();
+        boolean isChildMaxPlayer = !parentNode.isMaxPlayer();
         listofPossibleHeaps.forEach(n -> {
-            Node newNode = new Node(n, isMaxPlayer);
+            Node newNode = new Node(n, isChildMaxPlayer);
-            node.addChild(newNode);
+            parentNode.addChild(newNode);
             if (newNode.getNoOfBones() > 0) {
                 constructTree(newNode);
             }

algorithms/src/test/java/algorithms/BinarySearchTest.java

@@ -0,0 +1,41 @@
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+
+public class BinarySearchTest {
+
+    int[] sortedArray = { 0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9 };
+    int key = 6;
+    int expectedIndexForSearchKey = 7;
+    int low = 0;
+    int high = sortedArray.length - 1;
+    List<Integer> sortedList = Arrays.asList(0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9);
+    
+    @Test
+    public void givenASortedArrayOfIntegers_whenBinarySearchRunIterativelyForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchIteratively(sortedArray, key, low, high));
+    }
+
+    @Test
+    public void givenASortedArrayOfIntegers_whenBinarySearchRunRecursivelyForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchRecursively(sortedArray, key, low, high));
+    }
+    
+    @Test
+    public void givenASortedArrayOfIntegers_whenBinarySearchRunUsingArraysClassStaticMethodForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchUsingJavaArrays(sortedArray, key));
+    }
+    
+    @Test
+    public void givenASortedListOfIntegers_whenBinarySearchRunUsingCollectionsClassStaticMethodForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchUsingJavaCollections(sortedList, key));
+    }
+    
+}

apache-shiro/.gitignore

@@ -0,0 +1,4 @@
+
+/.idea/
+/target/
+/apache-shiro.iml

apache-shiro/pom.xml

@@ -0,0 +1,78 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.baeldung</groupId>
+    <artifactId>apache-shiro</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>1.5.2.RELEASE</version>
+    </parent>
+
+    <properties>
+        <apache-shiro-core-version>1.4.0</apache-shiro-core-version>
+        <log4j-version>1.2.17</log4j-version>
+        <slf4j-version>1.7.25</slf4j-version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-freemarker</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.shiro</groupId>
+            <artifactId>shiro-spring-boot-web-starter</artifactId>
+            <version>${apache-shiro-core-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.shiro</groupId>
+            <artifactId>shiro-core</artifactId>
+            <version>${apache-shiro-core-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>jcl-over-slf4j</artifactId>
+            <version>${slf4j-version}</version>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-log4j12</artifactId>
+            <version>${slf4j-version}</version>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>${log4j-version}</version>
+            <scope>runtime</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.6.2</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    
+</project>

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

@@ -0,0 +1,85 @@
+package com.baeldung;
+
+import org.apache.shiro.SecurityUtils;
+import org.apache.shiro.authc.*;
+import org.apache.shiro.mgt.DefaultSecurityManager;
+import org.apache.shiro.mgt.SecurityManager;
+import org.apache.shiro.realm.Realm;
+import org.apache.shiro.realm.text.IniRealm;
+import org.apache.shiro.session.Session;
+import org.apache.shiro.subject.Subject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Main {
+
+    private static final transient Logger log = LoggerFactory.getLogger(Main.class);
+
+    public static void main(String[] args) {
+
+        Realm realm = new MyCustomRealm();
+        SecurityManager securityManager = new DefaultSecurityManager(realm);
+
+        SecurityUtils.setSecurityManager(securityManager);
+        Subject currentUser = SecurityUtils.getSubject();
+
+        if (!currentUser.isAuthenticated()) {
+          UsernamePasswordToken token 
+            = new UsernamePasswordToken("user", "password");
+          token.setRememberMe(true);
+          try {
+              currentUser.login(token);
+          } catch (UnknownAccountException uae) {
+              log.error("Username Not Found!", uae);
+          } catch (IncorrectCredentialsException ice) {
+              log.error("Invalid Credentials!", ice);
+          } catch (LockedAccountException lae) {
+              log.error("Your Account is Locked!", lae);
+          } catch (AuthenticationException ae) {
+              log.error("Unexpected Error!", ae);
+          }
+        }
+
+        log.info("User [" + currentUser.getPrincipal() + "] logged in successfully.");
+
+        if (currentUser.hasRole("admin")) {
+            log.info("Welcome Admin");
+        } else if(currentUser.hasRole("editor")) {
+            log.info("Welcome, Editor!");
+        } else if(currentUser.hasRole("author")) {
+            log.info("Welcome, Author");
+        } else {
+            log.info("Welcome, Guest");
+        }
+
+        if(currentUser.isPermitted("articles:compose")) {
+            log.info("You can compose an article");
+        } else {
+            log.info("You are not permitted to compose an article!");
+        }
+
+        if(currentUser.isPermitted("articles:save")) {
+            log.info("You can save articles");
+        } else {
+            log.info("You can not save articles");
+        }
+
+        if(currentUser.isPermitted("articles:publish")) {
+            log.info("You can publish articles");
+        } else {
+            log.info("You can not publish articles");
+        }
+
+        Session session = currentUser.getSession();
+        session.setAttribute("key", "value");
+        String value = (String) session.getAttribute("key");
+        if (value.equals("value")) {
+            log.info("Retrieved the correct value! [" + value + "]");
+        }
+
+        currentUser.logout();
+
+        System.exit(0);
+    }
+
+}

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

@@ -0,0 +1,102 @@
+package com.baeldung;
+
+import org.apache.shiro.authc.*;
+import org.apache.shiro.authz.AuthorizationInfo;
+import org.apache.shiro.authz.SimpleAuthorizationInfo;
+import org.apache.shiro.realm.jdbc.JdbcRealm;
+import org.apache.shiro.subject.PrincipalCollection;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.*;
+
+public class MyCustomRealm extends JdbcRealm {
+
+    private Map<String, String> credentials = new HashMap<>();
+    private Map<String, Set<String>> roles = new HashMap<>();
+    private Map<String, Set<String>> perm = new HashMap<>();
+
+    {
+      credentials.put("user", "password");
+      credentials.put("user2", "password2");
+      credentials.put("user3", "password3");
+
+      roles.put("user", new HashSet<>(Arrays.asList("admin")));
+      roles.put("user2", new HashSet<>(Arrays.asList("editor")));
+      roles.put("user3", new HashSet<>(Arrays.asList("author")));
+
+      perm.put("admin", new HashSet<>(Arrays.asList("*")));
+      perm.put("editor", new HashSet<>(Arrays.asList("articles:*")));
+      perm.put("author",
+        new HashSet<>(Arrays.asList("articles:compose",
+          "articles:save")));
+
+    }
+
+    @Override
+    protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token)
+      throws AuthenticationException {
+
+        UsernamePasswordToken uToken = (UsernamePasswordToken) token;
+
+        if(uToken.getUsername() == null
+          || uToken.getUsername().isEmpty()
+          || !credentials.containsKey(uToken.getUsername())
+          ) {
+            throw new UnknownAccountException("username not found!");
+        }
+
+
+        return new SimpleAuthenticationInfo(
+          uToken.getUsername(), credentials.get(uToken.getUsername()),
+          getName());
+    }
+
+    @Override
+    protected AuthorizationInfo doGetAuthorizationInfo(PrincipalCollection principals) {
+        Set<String> roleNames = new HashSet<>();
+        Set<String> permissions = new HashSet<>();
+
+        principals.forEach(p -> {
+            try {
+                Set<String> roles = getRoleNamesForUser(null, (String) p);
+                roleNames.addAll(roles);
+                permissions.addAll(getPermissions(null, null,roles));
+            } catch (SQLException e) {
+                e.printStackTrace();
+            }
+        });
+
+        SimpleAuthorizationInfo info = new SimpleAuthorizationInfo(roleNames);
+        info.setStringPermissions(permissions);
+        return info;
+    }
+
+    @Override
+    protected Set<String> getRoleNamesForUser(Connection conn, String username) throws SQLException {
+        if(!roles.containsKey(username)) {
+            throw new SQLException("username not found!");
+        }
+
+       return roles.get(username);
+    }
+
+    @Override
+    protected Set<String> getPermissions(Connection conn, String username, Collection<String> roleNames) throws SQLException {
+        for (String role : roleNames) {
+            if (!perm.containsKey(role)) {
+                throw new SQLException("role not found!");
+            }
+        }
+
+        Set<String> finalSet = new HashSet<>();
+        for (String role : roleNames) {
+            finalSet.addAll(perm.get(role));
+        }
+
+        return finalSet;
+    }
+
+}

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

@@ -0,0 +1,45 @@
+package com.baeldung;
+
+import org.apache.shiro.realm.Realm;
+import org.apache.shiro.spring.web.config.DefaultShiroFilterChainDefinition;
+import org.apache.shiro.spring.web.config.ShiroFilterChainDefinition;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Bean;
+
+/**
+ * Created by smatt on 21/08/2017.
+ */
+@SpringBootApplication
+public class ShiroSpringApplication {
+
+    private static final transient Logger log = LoggerFactory.getLogger(ShiroSpringApplication.class);
+
+    public static void main(String... args) {
+        SpringApplication.run(ShiroSpringApplication.class, args);
+    }
+
+
+    @Bean
+    public Realm realm() {
+        return new MyCustomRealm();
+    }
+
+
+    @Bean
+    public ShiroFilterChainDefinition shiroFilterChainDefinition() {
+        DefaultShiroFilterChainDefinition filter
+          = new DefaultShiroFilterChainDefinition();
+
+        filter.addPathDefinition("/secure", "authc");
+        filter.addPathDefinition("/**", "anon");
+
+        return filter;
+    }
+
+
+
+
+}

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

@@ -0,0 +1,105 @@
+package com.baeldung.controllers;
+
+import com.baeldung.models.UserCredentials;
+import org.apache.shiro.SecurityUtils;
+import org.apache.shiro.authc.AuthenticationException;
+import org.apache.shiro.authc.UsernamePasswordToken;
+import org.apache.shiro.subject.Subject;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.ModelMap;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.servlet.mvc.support.RedirectAttributes;
+
+import javax.servlet.http.HttpServletRequest;
+
+@Controller
+public class ShiroSpringController {
+
+
+
+    @GetMapping("/")
+    public String index() {
+       return "index";
+    }
+
+
+    @RequestMapping( value = "/login", method = {RequestMethod.GET, RequestMethod.POST})
+    public String login(HttpServletRequest req, UserCredentials cred, RedirectAttributes attr) {
+
+      if(req.getMethod().equals(RequestMethod.GET.toString())) {
+        return "login";
+      }
+      else {
+
+        Subject subject = SecurityUtils.getSubject();
+
+        if(!subject.isAuthenticated()) {
+          UsernamePasswordToken token = new UsernamePasswordToken(
+            cred.getUsername(), cred.getPassword(), cred.isRememberMe());
+          try {
+            subject.login(token);
+          } catch (AuthenticationException ae) {
+              ae.printStackTrace();
+              attr.addFlashAttribute("error", "Invalid Credentials");
+              return "redirect:/login";
+          }
+        }
+
+        return "redirect:/secure";
+      }
+    }
+
+
+    @GetMapping("/secure")
+    public String secure(ModelMap modelMap) {
+
+        Subject currentUser = SecurityUtils.getSubject();
+        String role = "", permission = "";
+
+        if(currentUser.hasRole("admin")) {
+            role = role  + "You are an Admin";
+        }
+        else if(currentUser.hasRole("editor")) {
+            role = role + "You are an Editor";
+        }
+        else if(currentUser.hasRole("author")) {
+            role = role + "You are an Author";
+        }
+
+        if(currentUser.isPermitted("articles:compose")) {
+            permission = permission + "You can compose an article, ";
+        } else {
+            permission = permission + "You are not permitted to compose an article!, ";
+        }
+
+        if(currentUser.isPermitted("articles:save")) {
+            permission = permission + "You can save articles, ";
+        } else {
+            permission = permission + "\nYou can not save articles, ";
+        }
+
+        if(currentUser.isPermitted("articles:publish")) {
+            permission = permission  + "\nYou can publish articles";
+        } else {
+            permission = permission + "\nYou can not publish articles";
+        }
+
+        modelMap.addAttribute("username", currentUser.getPrincipal());
+        modelMap.addAttribute("permission", permission);
+        modelMap.addAttribute("role", role);
+
+        return "secure";
+    }
+
+
+    @PostMapping("/logout")
+    public String logout() {
+       Subject subject = SecurityUtils.getSubject();
+       subject.logout();
+       return "redirect:/";
+    }
+
+}

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

@@ -0,0 +1,40 @@
+package com.baeldung.models;
+
+public class UserCredentials {
+
+    private String username;
+    private String password;
+    private boolean rememberMe = false;
+
+    public UserCredentials() {}
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    public boolean isRememberMe() {
+        return rememberMe;
+    }
+
+    public void setRememberMe(boolean rememberMe) {
+        this.rememberMe = rememberMe;
+    }
+
+    @Override
+    public String toString() {
+        return "username = " + getUsername()
+                + "\nrememberMe = " + isRememberMe();
+    }
+}

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

@@ -0,0 +1,11 @@
+server.port=9000
+server.servlet-path=/
+server.context-path=/
+
+#shiro-spring-boot-config
+shiro.loginUrl = /login
+shiro.successUrl = /secure
+shiro.unauthorizedUrl = /login
+
+#freemarker
+spring.freemarker.suffix=.ftl

apache-shiro/src/main/resources/log4j.properties

@@ -0,0 +1,12 @@
+log4j.rootLogger=INFO, stdout
+
+log4j.appender.stdout=org.apache.log4j.ConsoleAppender
+log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
+log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m %n
+
+log4j.logger.org.apache=WARN
+
+log4j.logger.org.apache.shiro=INFO
+
+log4j.logger.org.apache.shiro.util.ThreadContext=WARN
+log4j.logger.org.apache.shiro.cache.ehcache.EhCache=WARN

apache-shiro/src/main/resources/shiro.ini

@@ -0,0 +1,9 @@
+[users]
+user = password,admin
+user2 = password2,editor
+user3 = password3,author
+
+[roles]
+admin = *
+editor = articles:*
+author = articles:compose,articles:save

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

@@ -0,0 +1,10 @@
+<html>
+<head>
+    <title>Index</title>
+</head>
+<body>
+    <h1>Welcome Guest!</h1>
+    <br>
+    <a href="/login">Login</a>
+</body>
+</html>

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

@@ -0,0 +1,27 @@
+<html>
+<head>
+    <title>Login</title>
+</head>
+<body style="margin-left: 30px;">
+<h3>Login</h3>
+<br>
+<form action="/login" method="post">
+    <#if (error?length > 0)??>
+        <p style="color:darkred;">${error}</p>
+    <#else>
+    </#if>
+
+    <label for="username">Username</label>
+    <br>
+    <input type="text" name="username">
+    <br><br>
+    <label for="password">Password</label>
+    <br>
+    <input type="password" name="password">
+    <br><br>
+    <input type="checkbox" name="rememberMe"> Remember Me
+    <br><br>
+    <input type="submit" value="Submit">
+</form>
+</body>
+</html>

apache-shiro/src/main/resources/templates/secure.ftl

@@ -0,0 +1,15 @@
+<html>
+<head>
+    <title>Secure</title>
+</head>
+<body style="margin-left: 30px;">
+<h1>Welcome ${username}!</h1>
+<p><strong>Role</strong>: ${role}</p>
+<p><strong>Permissions</strong></p>
+<p>${permission}</p>
+<br>
+<form role="form" action="/logout" method="POST">
+   <input type="Submit" value="Logout" />
+</form>
+</body>
+</html>

apache-velocity/src/main/webapp/WEB-INF/velocity.properties

@@ -1,4 +1,4 @@
 resource.loader=webapp
 webapp.resource.loader.class=org.apache.velocity.tools.view.WebappResourceLoader
-webapp.resource.loader.path = .
+webapp.resource.loader.path = 
 webapp.resource.loader.cache = true

asciidoctor/README.md

@@ -1,3 +1,4 @@
 ### Relevant articles
 
 - [Introduction to Asciidoctor](http://www.baeldung.com/introduction-to-asciidoctor)
+- [Generating a Book with Asciidoctor](http://www.baeldung.com/asciidoctor-book)

asciidoctor/pom.xml

@@ -35,7 +35,12 @@
                 <configuration>
                     <sourceDirectory>src/docs/asciidoc</sourceDirectory>
                     <outputDirectory>target/docs/asciidoc</outputDirectory>
+                    <attributes>
+                        <pdf-stylesdir>${project.basedir}/src/themes</pdf-stylesdir>
+                        <pdf-style>custom</pdf-style>
+                    </attributes>
                     <backend>pdf</backend>
+                    <doctype>book</doctype>
                 </configuration>
             </plugin>
         </plugins>

asciidoctor/src/docs/asciidoc/test.adoc

@@ -1,3 +1,13 @@
-== Introduction Section
+:icons: font
 
-Hi. I'm a simple test to see if this Maven build is working. If you see me in a nice PDF, then it means everything is [red]#working#.
+
+= Generating book with AsciiDoctorj
+Baeldung
+
+[abstract]
+This is the actual content.
+
+== First Section
+
+This is first section of the book where you can include some nice icons like icon:comment[].
+You can also create http://www.baeldung.com[links]

asciidoctor/src/themes/custom-theme.yml

@@ -0,0 +1,29 @@
+title_page:
+  align: left
+
+page:
+  layout: portrait
+  margin: [0.75in, 1in, 0.75in, 1in]
+  size: A4
+base:
+  font_color: #333333
+  line_height_length: 17
+  line_height: $base_line_height_length / $base_font_size
+link:
+  font_color: #009900
+
+header:
+  height: 0.5in
+  line_height: 1
+  recto_content:
+    center: '{document-title}'
+  verso_content:
+    center: '{document-title}'
+
+footer:
+  height: 0.5in
+  line_height: 1
+  recto_content:
+    right: '{chapter-title} | *{page-number}*'
+  verso_content:
+    left: '*{page-number}* | {chapter-title}'

aws/pom.xml

@@ -18,9 +18,41 @@
         <aws-lambda-java-events.version>1.3.0</aws-lambda-java-events.version>
         <aws-lambda-java-core.version>1.1.0</aws-lambda-java-core.version>
         <gson.version>2.8.0</gson.version>
+        <aws-java-sdk.version>1.11.154</aws-java-sdk.version>
+        <junit.version>4.12</junit.version>
+        <mockito-core.version>2.8.9</mockito-core.version>
+        <assertj-core.version>3.8.0</assertj-core.version>
     </properties>
 
     <dependencies>
+    
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-java-sdk</artifactId>
+            <version>${aws-java-sdk.version}</version>
+        </dependency>
+        
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+        
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>${mockito-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    
         <dependency>
             <groupId>com.amazonaws</groupId>
             <artifactId>aws-lambda-java-core</artifactId>

aws/src/main/java/com/baeldung/s3/AWSS3Service.java

@@ -0,0 +1,87 @@
+package com.baeldung.s3;
+
+import java.io.File;
+import java.util.List;
+
+import com.amazonaws.services.s3.AmazonS3;
+import com.amazonaws.services.s3.AmazonS3Client;
+import com.amazonaws.services.s3.model.Bucket;
+import com.amazonaws.services.s3.model.CopyObjectResult;
+import com.amazonaws.services.s3.model.DeleteObjectsRequest;
+import com.amazonaws.services.s3.model.DeleteObjectsResult;
+import com.amazonaws.services.s3.model.ObjectListing;
+import com.amazonaws.services.s3.model.PutObjectResult;
+import com.amazonaws.services.s3.model.S3Object;
+
+public class AWSS3Service {
+    private final AmazonS3 s3client;
+
+    public AWSS3Service() { 
+        this(new AmazonS3Client() {
+        }); 
+    } 
+    
+    public AWSS3Service(AmazonS3 s3client) {
+        this.s3client = s3client;
+    }
+    
+    //is bucket exist?
+    public boolean doesBucketExist(String bucketName) { 
+        return s3client.doesBucketExist(bucketName); 
+    } 
+    
+    //create a bucket
+    public Bucket createBucket(String bucketName) { 
+        return s3client.createBucket(bucketName); 
+    } 
+
+    //list all buckets
+    public List<Bucket> listBuckets() { 
+        return s3client.listBuckets(); 
+    }
+
+    //delete a bucket
+    public void deleteBucket(String bucketName) { 
+        s3client.deleteBucket(bucketName); 
+    }  
+    
+    //uploading object
+    public PutObjectResult putObject(String bucketName, String key, File file) {
+        return s3client.putObject(bucketName, key, file);
+    }
+    
+    //listing objects
+    public ObjectListing listObjects(String bucketName) {
+        return s3client.listObjects(bucketName);
+    }
+    
+    //get an object
+    public S3Object getObject(String bucketName, String objectKey) {
+        return s3client.getObject(bucketName, objectKey);
+    } 
+    
+    //copying an object
+    public CopyObjectResult copyObject(
+      String sourceBucketName,
+      String sourceKey,
+      String destinationBucketName,
+      String destinationKey
+    ) {
+        return s3client.copyObject(
+          sourceBucketName, 
+          sourceKey, 
+          destinationBucketName, 
+          destinationKey
+        );
+    }
+    
+    //deleting an object
+    public void deleteObject(String bucketName, String objectKey) {
+        s3client.deleteObject(bucketName, objectKey);
+    }
+    
+    //deleting multiple Objects
+    public DeleteObjectsResult deleteObjects(DeleteObjectsRequest delObjReq) {
+        return s3client.deleteObjects(delObjReq);
+    }
+}

aws/src/main/java/com/baeldung/s3/S3Application.java

@@ -0,0 +1,101 @@
+package com.baeldung.s3;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.apache.commons.io.FileUtils;
+
+import com.amazonaws.auth.AWSCredentials;
+import com.amazonaws.auth.AWSStaticCredentialsProvider;
+import com.amazonaws.auth.BasicAWSCredentials;
+import com.amazonaws.regions.Regions;
+import com.amazonaws.services.s3.AmazonS3;
+import com.amazonaws.services.s3.AmazonS3ClientBuilder;
+import com.amazonaws.services.s3.model.Bucket;
+import com.amazonaws.services.s3.model.DeleteObjectsRequest;
+import com.amazonaws.services.s3.model.ObjectListing;
+import com.amazonaws.services.s3.model.S3Object;
+import com.amazonaws.services.s3.model.S3ObjectInputStream;
+import com.amazonaws.services.s3.model.S3ObjectSummary;
+
+public class S3Application {
+
+    private static final AWSCredentials credentials;
+    private static String bucketName;  
+
+    static {
+        //put your accesskey and secretkey here
+        credentials = new BasicAWSCredentials(
+          "<AWS accesskey>", 
+          "<AWS secretkey>"
+        );
+    }
+    
+    public static void main(String[] args) throws IOException {
+        //set-up the client
+        AmazonS3 s3client = AmazonS3ClientBuilder
+          .standard()
+          .withCredentials(new AWSStaticCredentialsProvider(credentials))
+          .withRegion(Regions.US_EAST_2)
+          .build();
+        
+        AWSS3Service awsService = new AWSS3Service(s3client);
+
+        bucketName = "baeldung-bucket";
+
+        //creating a bucket
+        if(awsService.doesBucketExist(bucketName)) {
+            System.out.println("Bucket name is not available."
+              + " Try again with a different Bucket name.");
+            return;
+        }
+        awsService.createBucket(bucketName);
+        
+        //list all the buckets
+        for(Bucket s : awsService.listBuckets() ) {
+            System.out.println(s.getName());
+        }
+        
+        //deleting bucket
+        awsService.deleteBucket("baeldung-bucket-test2");
+        
+        //uploading object
+        awsService.putObject(
+          bucketName, 
+          "Document/hello.txt",
+          new File("/Users/user/Document/hello.txt")
+        );
+
+        //listing objects
+        ObjectListing objectListing = awsService.listObjects(bucketName);
+        for(S3ObjectSummary os : objectListing.getObjectSummaries()) {
+            System.out.println(os.getKey());
+        }
+
+        //downloading an object
+        S3Object s3object = awsService.getObject(bucketName, "Document/hello.txt");
+        S3ObjectInputStream inputStream = s3object.getObjectContent();
+        FileUtils.copyInputStreamToFile(inputStream, new File("/Users/user/Desktop/hello.txt"));
+        
+        //copying an object
+        awsService.copyObject(
+          "baeldung-bucket", 
+          "picture/pic.png", 
+          "baeldung-bucket2", 
+          "Document/picture.png"
+        );
+        
+        //deleting an object
+        awsService.deleteObject(bucketName, "Document/hello.txt");
+
+        //deleting multiple objects
+        String objkeyArr[] = {
+          "Document/hello2.txt", 
+          "Document/picture.png"
+        };
+        
+        DeleteObjectsRequest delObjReq = new DeleteObjectsRequest("baeldung-bucket")
+          .withKeys(objkeyArr);
+        awsService.deleteObjects(delObjReq);
+    }
+}

aws/src/test/java/com/baeldung/s3/AWSS3ServiceIntegrationTest.java

@@ -0,0 +1,113 @@
+package com.baeldung.s3;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.io.File;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.amazonaws.services.s3.AmazonS3;
+import com.amazonaws.services.s3.model.CopyObjectResult;
+import com.amazonaws.services.s3.model.DeleteObjectsRequest;
+import com.amazonaws.services.s3.model.DeleteObjectsResult;
+import com.amazonaws.services.s3.model.PutObjectResult; 
+
+public class AWSS3ServiceIntegrationTest {
+
+    private static final String BUCKET_NAME = "bucket_name"; 
+    private static final String KEY_NAME = "key_name"; 
+    private static final String BUCKET_NAME2 = "bucket_name2"; 
+    private static final String KEY_NAME2 = "key_name2"; 
+ 
+    private AmazonS3 s3; 
+    private AWSS3Service service; 
+ 
+    @Before 
+    public void setUp() { 
+        s3 = mock(AmazonS3.class); 
+        service = new AWSS3Service(s3); 
+    } 
+ 
+    @Test 
+    public void whenInitializingAWSS3Service_thenNotNull() { 
+        assertThat(new AWSS3Service()).isNotNull(); 
+    } 
+    
+    @Test 
+    public void whenVerifyingIfS3BucketExist_thenCorrect() { 
+        service.doesBucketExist(BUCKET_NAME); 
+        verify(s3).doesBucketExist(BUCKET_NAME); 
+    } 
+ 
+    @Test 
+    public void whenVerifyingCreationOfS3Bucket_thenCorrect() { 
+        service.createBucket(BUCKET_NAME); 
+        verify(s3).createBucket(BUCKET_NAME); 
+    } 
+ 
+    @Test 
+    public void whenVerifyingListBuckets_thenCorrect() { 
+        service.listBuckets(); 
+        verify(s3).listBuckets(); 
+    } 
+
+    @Test 
+    public void whenDeletingBucket_thenCorrect() { 
+        service.deleteBucket(BUCKET_NAME); 
+        verify(s3).deleteBucket(BUCKET_NAME); 
+    } 
+    
+    @Test 
+    public void whenVerifyingPutObject_thenCorrect() { 
+        File file = mock(File.class); 
+        PutObjectResult result = mock(PutObjectResult.class); 
+        when(s3.putObject(anyString(), anyString(), (File) any())).thenReturn(result); 
+ 
+        assertThat(service.putObject(BUCKET_NAME, KEY_NAME, file)).isEqualTo(result); 
+        verify(s3).putObject(BUCKET_NAME, KEY_NAME, file); 
+    }
+    
+    @Test 
+    public void whenVerifyingListObjects_thenCorrect() { 
+        service.listObjects(BUCKET_NAME); 
+        verify(s3).listObjects(BUCKET_NAME); 
+    } 
+    
+    @Test 
+    public void whenVerifyingGetObject_thenCorrect() { 
+        service.getObject(BUCKET_NAME, KEY_NAME); 
+        verify(s3).getObject(BUCKET_NAME, KEY_NAME); 
+    } 
+    
+    @Test 
+    public void whenVerifyingCopyObject_thenCorrect() { 
+        CopyObjectResult result = mock(CopyObjectResult.class); 
+        when(s3.copyObject(anyString(), anyString(), anyString(), anyString())).thenReturn(result); 
+ 
+        assertThat(service.copyObject(BUCKET_NAME, KEY_NAME, BUCKET_NAME2, KEY_NAME2)).isEqualTo(result); 
+        verify(s3).copyObject(BUCKET_NAME, KEY_NAME, BUCKET_NAME2, KEY_NAME2);
+    } 
+    
+    @Test 
+    public void whenVerifyingDeleteObject_thenCorrect() { 
+        service.deleteObject(BUCKET_NAME, KEY_NAME); 
+        verify(s3).deleteObject(BUCKET_NAME, KEY_NAME); 
+    }
+    
+    @Test 
+    public void whenVerifyingDeleteObjects_thenCorrect() { 
+        DeleteObjectsRequest request = mock(DeleteObjectsRequest.class);
+        DeleteObjectsResult result = mock(DeleteObjectsResult.class);
+        when(s3.deleteObjects((DeleteObjectsRequest)any())).thenReturn(result); 
+        
+        assertThat(service.deleteObjects(request)).isEqualTo(result);
+        verify(s3).deleteObjects(request); 
+    }
+    
+}

bootique/config.yml

@@ -0,0 +1,11 @@
+log:
+  level: warn
+  appenders:
+    - type: file
+      logFormat: '%c{20}: %m%n'
+      file: /home/logger.log
+
+jetty:
+  context: /hello
+  connector:
+    port: 10001

bootique/dependency-reduced-pom.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+  <parent>
+    <artifactId>bootique-parent</artifactId>
+    <groupId>io.bootique.parent</groupId>
+    <version>0.12</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.baeldung.bootique</groupId>
+  <artifactId>bootique</artifactId>
+  <name>bootique</name>
+  <version>1.0-SNAPSHOT</version>
+  <url>http://maven.apache.org</url>
+  <build>
+    <plugins>
+      <plugin>
+        <artifactId>maven-shade-plugin</artifactId>
+      </plugin>
+    </plugins>
+  </build>
+  <dependencies>
+    <dependency>
+      <groupId>io.bootique</groupId>
+      <artifactId>bootique-test</artifactId>
+      <version>0.23</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>3.8.1</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>io.bootique.bom</groupId>
+        <artifactId>bootique-bom</artifactId>
+        <version>0.23</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+  <properties>
+    <main.class>com.baeldung.bootique.App</main.class>
+  </properties>
+</project>
+

bootique/pom.xml

@@ -0,0 +1,66 @@
+<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/maven-v4_0_0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>com.baeldung.bootique</groupId>
+	<artifactId>bootique</artifactId>
+	<packaging>jar</packaging>
+	<version>1.0-SNAPSHOT</version>
+	<name>bootique</name>
+	<url>http://maven.apache.org</url>
+
+	<properties>
+		<main.class>com.baeldung.bootique.App</main.class>
+	</properties>
+
+	<parent>
+		<groupId>io.bootique.parent</groupId>
+		<artifactId>bootique-parent</artifactId>
+		<version>0.12</version>
+	</parent>
+
+	<dependencyManagement>
+		<dependencies>
+			<dependency>
+				<groupId>io.bootique.bom</groupId>
+				<artifactId>bootique-bom</artifactId>
+				<version>0.23</version>
+				<type>pom</type>
+				<scope>import</scope>
+			</dependency>
+		</dependencies>
+	</dependencyManagement>
+
+	<dependencies>
+		<dependency>
+			<groupId>io.bootique.jersey</groupId>
+			<artifactId>bootique-jersey</artifactId>
+			<scope>compile</scope>
+		</dependency>
+		<dependency>
+			<groupId>io.bootique.logback</groupId>
+			<artifactId>bootique-logback</artifactId>
+			<scope>compile</scope>
+		</dependency>
+		<dependency>
+			<groupId>io.bootique</groupId>
+			<artifactId>bootique-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.12</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-shade-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

bootique/src/main/java/com/baeldung/bootique/App.java

@@ -0,0 +1,41 @@
+package com.baeldung.bootique;
+
+import com.baeldung.bootique.module.ModuleBinder;
+import com.baeldung.bootique.router.IndexController;
+import com.baeldung.bootique.router.SaveController;
+import com.google.inject.Module;
+import io.bootique.Bootique;
+import io.bootique.jersey.JerseyModule;
+import io.bootique.log.BootLogger;
+
+import java.util.function.Supplier;
+
+public class App {
+
+    public static void main(String[] args) {
+        Module module = binder -> JerseyModule.extend(binder).addResource(IndexController.class)
+          .addResource(SaveController.class);
+        Bootique.app(args).module(module).module(ModuleBinder.class).bootLogger(new BootLogger() {
+            @Override
+            public void trace(Supplier<String> arg0) {
+                // ...
+            }
+
+            @Override
+            public void stdout(String arg0) {
+                // ...
+            }
+
+            @Override
+            public void stderr(String arg0, Throwable arg1) {
+                // ...
+            }
+
+            @Override
+            public void stderr(String arg0) {
+                // ...
+            }
+        }).autoLoadModules().exec();
+    }
+
+}

bootique/src/main/java/com/baeldung/bootique/module/ModuleBinder.java

@@ -0,0 +1,15 @@
+package com.baeldung.bootique.module;
+
+import com.baeldung.bootique.service.HelloService;
+import com.baeldung.bootique.service.impl.HelloServiceImpl;
+import com.google.inject.Binder;
+import com.google.inject.Module;
+
+public class ModuleBinder implements Module {
+
+    @Override
+    public void configure(Binder binder) {
+        binder.bind(HelloService.class).to(HelloServiceImpl.class);
+    }
+
+}

bootique/src/main/java/com/baeldung/bootique/module/ModuleProvider.java

@@ -0,0 +1,13 @@
+package com.baeldung.bootique.module;
+
+import com.google.inject.Module;
+import io.bootique.BQModuleProvider;
+
+public class ModuleProvider implements BQModuleProvider {
+
+    @Override
+    public Module module() {
+        return new ModuleBinder();
+    }
+
+}

bootique/src/main/java/com/baeldung/bootique/router/IndexController.java

@@ -0,0 +1,14 @@
+package com.baeldung.bootique.router;
+
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+
+@Path("/")
+public class IndexController {
+
+    @GET
+    public String index() {
+        return "Hello, baeldung!";
+    }
+
+}

bootique/src/main/java/com/baeldung/bootique/router/SaveController.java

@@ -0,0 +1,20 @@
+package com.baeldung.bootique.router;
+
+import com.baeldung.bootique.service.HelloService;
+import com.google.inject.Inject;
+
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+
+@Path("/save")
+public class SaveController {
+
+    @Inject
+    HelloService helloService;
+
+    @POST
+    public String save() {
+        return "Data Saved!";
+    }
+
+}

bootique/src/main/java/com/baeldung/bootique/service/HelloService.java

@@ -0,0 +1,7 @@
+package com.baeldung.bootique.service;
+
+public interface HelloService {
+
+	boolean save();
+
+}

bootique/src/main/java/com/baeldung/bootique/service/impl/HelloServiceImpl.java

@@ -0,0 +1,12 @@
+package com.baeldung.bootique.service.impl;
+
+import com.baeldung.bootique.service.HelloService;
+
+public class HelloServiceImpl implements HelloService {
+
+	@Override
+	public boolean save() {
+		return true;
+	}
+
+}

bootique/src/main/resources/META-INF/services/io.bootique.BQModuleProvider

@@ -0,0 +1 @@
+com.baeldung.bootique.module.ModuleProvider

bootique/src/test/java/com/baeldung/bootique/AppTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.bootique;
+
+import com.baeldung.bootique.service.HelloService;
+import io.bootique.BQRuntime;
+import io.bootique.test.junit.BQDaemonTestFactory;
+import io.bootique.test.junit.BQTestFactory;
+import org.junit.Rule;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class AppTest {
+
+    @Rule
+    public BQTestFactory bqTestFactory = new BQTestFactory();
+
+    @Rule
+    public BQDaemonTestFactory bqDaemonTestFactory = new BQDaemonTestFactory();
+
+    @Test
+    public void givenService_expectBoolen() {
+        BQRuntime runtime = bqTestFactory.app("--server").autoLoadModules().createRuntime();
+        HelloService service = runtime.getInstance(HelloService.class);
+        assertEquals(true, service.save());
+    }
+
+}

camel-api/src/main/java/com/baeldung/camel/Application.java

@@ -13,14 +13,13 @@ import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.web.servlet.ServletRegistrationBean;
-import org.springframework.boot.web.support.SpringBootServletInitializer;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.stereotype.Component;
 
 @SpringBootApplication
 @ComponentScan(basePackages="com.baeldung.camel")
-public class Application extends SpringBootServletInitializer {
+public class Application{
 
     @Value("${server.port}")
     String serverPort;
@@ -62,10 +61,12 @@ public class Application extends SpringBootServletInitializer {
                 .bindingMode(RestBindingMode.json)
                 .dataFormatProperty("prettyPrint", "true");
 /** 
-The Rest DSL supports automatic binding json/xml contents to/from POJOs using Camels Data Format.
+The Rest DSL supports automatic binding json/xml contents to/from 
-By default the binding mode is off, meaning there is no automatic binding happening for incoming and outgoing messages.
+POJOs using Camels Data Format.
-You may want to use binding if you develop POJOs that maps to your REST services request and response types. 
+By default the binding mode is off, meaning there is no automatic 
-This allows you, as a developer, to work with the POJOs in Java code.
+binding happening for incoming and outgoing messages.
+You may want to use binding if you develop POJOs that maps to 
+your REST services request and response types. 
 */         
             
             rest("/api/").description("Teste REST Service")

core-java-9/README.md

@@ -13,3 +13,6 @@
 - [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)
+- [Java 9 Optional API Additions](http://www.baeldung.com/java-9-optional)
+- [Java 9 Reactive Streams](http://www.baeldung.com/java-9-reactive-streams)
+- [How to Get All Dates Between Two Dates?](http://www.baeldung.com/java-between-dates)

core-java-9/src/main/java/com/baeldung/java9/process/ServiceMain.java

@@ -6,7 +6,7 @@ public class ServiceMain {
 
     public static void main(String[] args) throws InterruptedException {
         ProcessHandle thisProcess = ProcessHandle.current();
-        long pid = thisProcess.getPid();
+        long pid = thisProcess.pid();
 
         Optional<String[]> opArgs = Optional.ofNullable(args);
         String procName = opArgs.map(str -> str.length > 0 ? str[0] : null).orElse(System.getProperty("sun.java.command"));

core-java-9/src/test/java/com/baeldung/java9/language/Java9ObjectsAPIUnitTest.java

@@ -0,0 +1,86 @@
+package com.baeldung.java9.language;
+
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+import static org.hamcrest.Matchers.*;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class Java9ObjectsAPIUnitTest {
+
+    private List<String> aMethodReturningNullList(){
+        return null;
+    }
+
+    @Test
+    public void givenNullObject_whenRequireNonNullElse_thenElse(){
+        List<String> aList = Objects.<List>requireNonNullElse(
+                aMethodReturningNullList(), Collections.EMPTY_LIST);
+        assertThat(aList, is(Collections.EMPTY_LIST));
+    }
+
+    private List<String> aMethodReturningNonNullList(){
+        return List.of("item1", "item2");
+    }
+
+    @Test
+    public void givenObject_whenRequireNonNullElse_thenObject(){
+        List<String> aList = Objects.<List>requireNonNullElse(
+                aMethodReturningNonNullList(), Collections.EMPTY_LIST);
+        assertThat(aList, is(List.of("item1", "item2")));
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void givenNull_whenRequireNonNullElse_thenException(){
+        Objects.<List>requireNonNullElse(null, null);
+    }
+
+    @Test
+    public void givenObject_whenRequireNonNullElseGet_thenObject(){
+        List<String> aList = Objects.<List>requireNonNullElseGet(null, List::of);
+        assertThat(aList, is(List.of()));
+    }
+
+    @Test
+    public void givenNumber_whenInvokeCheckIndex_thenNumber(){
+        int length = 5;
+        assertThat(Objects.checkIndex(4, length), is(4));
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void givenOutOfRangeNumber_whenInvokeCheckIndex_thenException(){
+        int length = 5;
+        Objects.checkIndex(5, length);
+    }
+
+
+    @Test
+    public void givenSubRange_whenCheckFromToIndex_thenNumber(){
+        int length = 6;
+        assertThat(Objects.checkFromToIndex(2,length,length), is(2));
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void givenInvalidSubRange_whenCheckFromToIndex_thenException(){
+        int length = 6;
+        Objects.checkFromToIndex(2,7,length);
+    }
+
+
+    @Test
+    public void givenSubRange_whenCheckFromIndexSize_thenNumber(){
+        int length = 6;
+        assertThat(Objects.checkFromIndexSize(2,3,length), is(2));
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void givenInvalidSubRange_whenCheckFromIndexSize_thenException(){
+        int length = 6;
+        Objects.checkFromIndexSize(2, 6, length);
+    }
+
+
+}

core-java-concurrency/.gitignore

@@ -0,0 +1,26 @@
+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+*.txt
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-concurrency/README.md

@@ -0,0 +1,32 @@
+=========
+
+## Core Java Concurrency Examples
+
+### Relevant Articles: 
+- [Guide To CompletableFuture](http://www.baeldung.com/java-completablefuture)
+- [A Guide to the Java ExecutorService](http://www.baeldung.com/java-executor-service-tutorial)
+- [Introduction to Thread Pools in Java](http://www.baeldung.com/thread-pool-java-and-guava)
+- [Guide to java.util.concurrent.Future](http://www.baeldung.com/java-future)
+- [Guide to java.util.concurrent.BlockingQueue](http://www.baeldung.com/java-blocking-queue)
+- [Guide to CountDownLatch in Java](http://www.baeldung.com/java-countdown-latch)
+- [A Guide to ConcurrentMap](http://www.baeldung.com/java-concurrent-map)
+- [Guide to PriorityBlockingQueue in Java](http://www.baeldung.com/java-priority-blocking-queue)
+- [Avoiding the ConcurrentModificationException in Java](http://www.baeldung.com/java-concurrentmodificationexception)
+- [Custom Thread Pools In Java 8 Parallel Streams](http://www.baeldung.com/java-8-parallel-streams-custom-threadpool)
+- [Guide to java.util.concurrent.Locks](http://www.baeldung.com/java-concurrent-locks)
+- [An Introduction to ThreadLocal in Java](http://www.baeldung.com/java-threadlocal)
+- [Guide to DelayQueue](http://www.baeldung.com/java-delay-queue)
+- [A Guide to Java SynchronousQueue](http://www.baeldung.com/java-synchronous-queue)
+- [Guide to the Java TransferQueue](http://www.baeldung.com/java-transfer-queue)
+- [Guide to the ConcurrentSkipListMap](http://www.baeldung.com/java-concurrent-skip-list-map)
+- [Difference Between Wait and Sleep in Java](http://www.baeldung.com/java-wait-and-sleep)
+- [LongAdder and LongAccumulator in Java](http://www.baeldung.com/java-longadder-and-longaccumulator)
+- [The Dining Philosophers Problem in Java](http://www.baeldung.com/java-dining-philoshophers)
+- [Guide to CopyOnWriteArrayList](http://www.baeldung.com/java-copy-on-write-arraylist)
+- [Guide to the Java Phaser](http://www.baeldung.com/java-phaser)
+- [Guide to Synchronized Keyword in Java](http://www.baeldung.com/java-synchronized)
+- [An Introduction to Atomic Variables in Java](http://www.baeldung.com/java-atomic-variables)
+- [CyclicBarrier in Java](http://www.baeldung.com/java-cyclic-barrier)
+- [Guide to Volatile Keyword in Java](http://www.baeldung.com/java-volatile)
+- [Overview of the java.util.concurrent](http://www.baeldung.com/java-util-concurrent)
+- [Semaphores in Java](http://www.baeldung.com/java-semaphore)

core-java-concurrency/pom.xml

@@ -0,0 +1,237 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-concurrency</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
+
+    <name>core-java-concurrency</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+
+        <!-- utils -->
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>${commons-io.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
+
+
+        <!-- test scoped -->
+
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
+            <groupId>com.jayway.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${avaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+    
+    <build>
+        <finalName>core-java-concurrency</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>copy-dependencies</id>
+                        <phase>prepare-package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}/libs</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <configuration>
+                    <archive>
+                        <manifest>
+                            <addClasspath>true</addClasspath>
+                            <classpathPrefix>libs/</classpathPrefix>
+                            <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
+                        </manifest>
+                    </archive>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                        <configuration>
+                            <archiveBaseDirectory>${project.basedir}</archiveBaseDirectory>
+                            <archive>
+                                <manifest>
+                                    <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
+                                </manifest>
+                            </archive>
+                            <descriptorRefs>
+                                <descriptorRef>jar-with-dependencies</descriptorRef>
+                            </descriptorRefs>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <shadedArtifactAttached>true</shadedArtifactAttached>
+                            <transformers>
+                                <transformer
+                                    implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>com.jolira</groupId>
+                <artifactId>onejar-maven-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <configuration>
+                            <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
+                            <attachToBuild>true</attachToBuild>
+                            <filename>${project.build.finalName}-onejar.${project.packaging}</filename>
+                        </configuration>
+                        <goals>
+                            <goal>one-jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>repackage</goal>
+                        </goals>
+                        <configuration>
+                            <classifier>spring-boot</classifier>
+                            <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+
+    </build>
+
+    <profiles>
+        <profile>
+            <id>integration</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <phase>integration-test</phase>
+                                <goals>
+                                    <goal>test</goal>
+                                </goals>
+                                <configuration>
+                                    <excludes>
+                                        <exclude>**/*ManualTest.java</exclude>
+                                    </excludes>
+                                    <includes>
+                                        <include>**/*IntegrationTest.java</include>
+                                    </includes>
+                                </configuration>
+                            </execution>
+                        </executions>
+                        <configuration>
+                            <systemPropertyVariables>
+                                <test.mime>json</test.mime>
+                            </systemPropertyVariables>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
+    
+    <properties>
+
+        <!-- util -->
+        <guava.version>21.0</guava.version>
+        <commons-lang3.version>3.5</commons-lang3.version>
+        <commons-math3.version>3.6.1</commons-math3.version>
+        <commons-io.version>2.5</commons-io.version>
+        <commons-collections4.version>4.1</commons-collections4.version>
+        <collections-generic.version>4.01</collections-generic.version>
+
+        <!-- testing -->
+        <assertj.version>3.6.1</assertj.version>
+        <avaitility.version>1.7.0</avaitility.version>
+
+    </properties>
+</project>

core-java-concurrency/src/main/java/com/baeldung/concurrent/Scheduledexecutorservice/ScheduledExecutorServiceDemo.java

@@ -0,0 +1,34 @@
+package com.baeldung.concurrent.Scheduledexecutorservice;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+
+public class ScheduledExecutorServiceDemo {
+
+	public void execute() {
+		ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
+
+		ScheduledFuture<?> scheduledFuture = executorService.schedule(() -> {
+			// Task
+		}, 1, TimeUnit.SECONDS);
+
+		executorService.scheduleAtFixedRate(() -> {
+			// Task
+		}, 1, 10, TimeUnit.SECONDS);
+
+		executorService.scheduleWithFixedDelay(() -> {
+			// Task
+		}, 1, 10, TimeUnit.SECONDS);
+
+		Future<String> future = executorService.schedule(() -> {
+			// Task
+			return "Hellow world";
+		}, 1, TimeUnit.SECONDS);
+
+		executorService.shutdown();
+	}
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/atomic/SafeCounterWithLock.java

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

core-java-concurrency/src/main/java/com/baeldung/concurrent/atomic/SafeCounterWithoutLock.java

@@ -0,0 +1,21 @@
+package com.baeldung.concurrent.atomic;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class SafeCounterWithoutLock {
+    private final AtomicInteger counter = new AtomicInteger(0);
+    
+    int getValue() {
+        return counter.get();
+    }
+    
+    void increment() {
+        while(true) {
+            int existingValue = getValue();
+            int newValue = existingValue + 1;
+            if(counter.compareAndSet(existingValue, newValue)) {
+                return;
+            }
+        }
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/atomic/UnsafeCounter.java

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

core-java-concurrency/src/main/java/com/baeldung/concurrent/blockingqueue/NumbersProducer.java

@@ -19,13 +19,15 @@ public class NumbersProducer implements Runnable {
         try {
             generateNumbers();
         } catch (InterruptedException e) {
-            Thread.currentThread().interrupt();
+            Thread.currentThread()
+                .interrupt();
         }
     }
 
     private void generateNumbers() throws InterruptedException {
         for (int i = 0; i < 100; i++) {
-            numbersQueue.put(ThreadLocalRandom.current().nextInt(100));
+            numbersQueue.put(ThreadLocalRandom.current()
+                .nextInt(100));
         }
         for (int j = 0; j < poisonPillPerProducer; j++) {
             numbersQueue.put(poisonPill);

core-java-concurrency/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierDemo.java

@@ -15,14 +15,12 @@ public class CyclicBarrierDemo {
     private int NUM_PARTIAL_RESULTS;
     private int NUM_WORKERS;
 
-
     private void runSimulation(int numWorkers, int numberOfPartialResults) {
         NUM_PARTIAL_RESULTS = numberOfPartialResults;
         NUM_WORKERS = numWorkers;
 
         cyclicBarrier = new CyclicBarrier(NUM_WORKERS, new AggregatorThread());
-        System.out.println("Spawning " + NUM_WORKERS + " worker threads to compute "
+        System.out.println("Spawning " + NUM_WORKERS + " worker threads to compute " + NUM_PARTIAL_RESULTS + " partial results each");
-                + NUM_PARTIAL_RESULTS + " partial results each");
         for (int i = 0; i < NUM_WORKERS; i++) {
             Thread worker = new Thread(new NumberCruncherThread());
             worker.setName("Thread " + i);
@@ -38,8 +36,7 @@ public class CyclicBarrierDemo {
             List<Integer> partialResult = new ArrayList<>();
             for (int i = 0; i < NUM_PARTIAL_RESULTS; i++) {
                 Integer num = random.nextInt(10);
-                System.out.println(thisThreadName
+                System.out.println(thisThreadName + ": Crunching some numbers! Final result - " + num);
-                        + ": Crunching some numbers! Final result - " + num);
                 partialResult.add(num);
             }
             partialResults.add(partialResult);
@@ -57,13 +54,12 @@ public class CyclicBarrierDemo {
         @Override
         public void run() {
             String thisThreadName = Thread.currentThread().getName();
-            System.out.println(thisThreadName + ": Computing final sum of " + NUM_WORKERS
+            System.out.println(thisThreadName + ": Computing final sum of " + NUM_WORKERS + " workers, having " + NUM_PARTIAL_RESULTS + " results each.");
-                    + " workers, having " + NUM_PARTIAL_RESULTS + " results each.");
             int sum = 0;
             for (List<Integer> threadResult : partialResults) {
                 System.out.print("Adding ");
                 for (Integer partialResult : threadResult) {
-                    System.out.print(partialResult+" ");
+                    System.out.print(partialResult + " ");
                     sum += partialResult;
                 }
                 System.out.println();

core-java-concurrency/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierExample.java

@@ -0,0 +1,24 @@
+package com.baeldung.concurrent.cyclicbarrier;
+
+import java.util.concurrent.CyclicBarrier;
+
+public class CyclicBarrierExample {
+
+    public void start() {
+        CyclicBarrier cyclicBarrier = new CyclicBarrier(3, () -> {
+            // Task
+            System.out.println("All previous tasks are completed");
+        });
+
+        Thread t1 = new Thread(new Task(cyclicBarrier), "T1");
+        Thread t2 = new Thread(new Task(cyclicBarrier), "T2");
+        Thread t3 = new Thread(new Task(cyclicBarrier), "T3");
+
+        if (!cyclicBarrier.isBroken()) {
+            t1.start();
+            t2.start();
+            t3.start();
+        }
+    }
+}
+

core-java-concurrency/src/main/java/com/baeldung/concurrent/cyclicbarrier/Task.java

@@ -0,0 +1,24 @@
+package com.baeldung.concurrent.cyclicbarrier;
+
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+
+public class Task implements Runnable {
+
+    private CyclicBarrier barrier;
+
+    public Task(CyclicBarrier barrier) {
+        this.barrier = barrier;
+    }
+
+    @Override
+    public void run() {
+        try {
+            System.out.println("Thread : " + Thread.currentThread().getName() + " is waiting");
+            barrier.await();
+            System.out.println("Thread : " + Thread.currentThread().getName() + " is released");
+        } catch (InterruptedException | BrokenBarrierException e) {
+            e.printStackTrace();
+        }
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/delayqueue/DelayObject.java

@@ -27,9 +27,6 @@ public class DelayObject implements Delayed {
 
     @Override
     public String toString() {
-        return "{" +
+        return "{" + "data='" + data + '\'' + ", startTime=" + startTime + '}';
-                "data='" + data + '\'' +
-                ", startTime=" + startTime +
-                '}';
     }
 }

core-java-concurrency/src/main/java/com/baeldung/concurrent/diningphilosophers/Philosopher.java

@@ -15,7 +15,8 @@ public class Philosopher implements Runnable {
         Thread.sleep(((int) (Math.random() * 100)));
     }
 
-    @Override public void run() {
+    @Override
+    public void run() {
         try {
             while (true) {
                 doAction(System.nanoTime() + ": Thinking"); // thinking

core-java-concurrency/src/main/java/com/baeldung/concurrent/executor/ExecutorDemo.java

@@ -0,0 +1,14 @@
+package com.baeldung.concurrent.executor;
+
+import java.util.concurrent.Executor;
+
+public class ExecutorDemo {
+
+	public void execute() {
+		Executor executor = new Invoker();
+		executor.execute(()->{
+			// task to be performed
+		});
+	}
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/executor/Invoker.java

@@ -0,0 +1,12 @@
+package com.baeldung.concurrent.executor;
+
+import java.util.concurrent.Executor;
+
+public class Invoker implements Executor {
+
+	@Override
+	public void execute(Runnable r) {
+		r.run();
+	}
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/executorservice/ExecutorServiceDemo.java

@@ -0,0 +1,27 @@
+package com.baeldung.concurrent.executorservice;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+public class ExecutorServiceDemo {
+
+    ExecutorService executor = Executors.newFixedThreadPool(10);
+
+    public void execute() {
+
+        executor.submit(() -> {
+            new Task();
+        });
+
+        executor.shutdown();
+        executor.shutdownNow();
+        try {
+            executor.awaitTermination(20l, TimeUnit.NANOSECONDS);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+
+    }
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/executorservice/Task.java

@@ -0,0 +1,10 @@
+package com.baeldung.concurrent.executorservice;
+
+public class Task implements Runnable {
+
+	@Override
+	public void run() {
+		// task details
+	}
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/future/FutureDemo.java

@@ -0,0 +1,44 @@
+package com.baeldung.concurrent.future;
+
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+public class FutureDemo {
+
+    public String invoke() {
+
+        String str = null;
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        Future<String> future = executorService.submit(() -> {
+            // Task
+            Thread.sleep(10000l);
+            return "Hellow world";
+        });
+
+        future.cancel(false);
+
+        try {
+            future.get(20, TimeUnit.SECONDS);
+        } catch (InterruptedException | ExecutionException | TimeoutException e1) {
+            e1.printStackTrace();
+        }
+
+        if (future.isDone() && !future.isCancelled()) {
+            try {
+                str = future.get();
+            } catch (InterruptedException | ExecutionException e) {
+                e.printStackTrace();
+            }
+        }
+
+        return str;
+
+    }
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/semaphore/SemaPhoreDemo.java

@@ -0,0 +1,22 @@
+package com.baeldung.concurrent.semaphore;
+
+import java.util.concurrent.Semaphore;
+
+public class SemaPhoreDemo {
+
+	static Semaphore semaphore = new Semaphore(10);
+	
+	public void execute() throws InterruptedException {
+
+		System.out.println("Available permit : " + semaphore.availablePermits());
+		System.out.println("Number of threads waiting to acquire: " + semaphore.getQueueLength());
+
+		if (semaphore.tryAcquire()) {
+			semaphore.acquire();
+			// perform some critical operations
+			semaphore.release();
+		}
+
+	}
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/threadfactory/BaeldungThreadFactory.java

@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.threadfactory;
+
+import java.util.concurrent.ThreadFactory;
+
+public class BaeldungThreadFactory implements ThreadFactory {
+
+    private int threadId;
+    private String name;
+
+    public BaeldungThreadFactory(String name) {
+        threadId = 1;
+        this.name = name;
+    }
+
+    @Override
+    public Thread newThread(Runnable r) {
+        Thread t = new Thread(r, name + "-Thread_" + threadId);
+        System.out.println("created new thread with id : " + threadId + " and name : " + t.getName());
+        threadId++;
+        return t;
+    }
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/threadfactory/Demo.java

@@ -0,0 +1,13 @@
+package com.baeldung.concurrent.threadfactory;
+
+public class Demo {
+
+	public void execute() {
+		BaeldungThreadFactory factory = new BaeldungThreadFactory("BaeldungThreadFactory");
+		for (int i = 0; i < 10; i++) {
+			Thread t = factory.newThread(new Task());
+			t.start();
+		}
+	}
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/threadfactory/Task.java

@@ -0,0 +1,10 @@
+package com.baeldung.concurrent.threadfactory;
+
+public class Task implements Runnable {
+
+    @Override
+    public void run() {
+        // task details
+    }
+
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/volatilekeyword/SharedObject.java

@@ -0,0 +1,13 @@
+package com.baeldung.concurrent.volatilekeyword;
+
+
+public class SharedObject {
+    private volatile int count=0;
+
+    void increamentCount(){
+        count++;
+    }
+    public int  getCount(){
+        return count;
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/threadlocal/Context.java

@@ -4,14 +4,14 @@ package com.baeldung.threadlocal;
 public class Context {
     private final String userName;
 
-    public Context(String userName) {
+    Context(String userName) {
         this.userName = userName;
     }
 
     @Override
     public String toString() {
         return "Context{" +
-                "userNameSecret='" + userName + '\'' +
+          "userNameSecret='" + userName + '\'' +
-                '}';
+          '}';
     }
 }

core-java-concurrency/src/main/java/com/baeldung/threadlocal/SharedMapWithUserContext.java

@@ -5,11 +5,11 @@ import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
 public class SharedMapWithUserContext implements Runnable {
-    public final static Map<Integer, Context> userContextPerUserId = new ConcurrentHashMap<>();
+    final static Map<Integer, Context> userContextPerUserId = new ConcurrentHashMap<>();
     private final Integer userId;
     private UserRepository userRepository = new UserRepository();
 
-    public SharedMapWithUserContext(Integer userId) {
+    SharedMapWithUserContext(Integer userId) {
         this.userId = userId;
     }
 

core-java-concurrency/src/main/java/com/baeldung/threadlocal/ThreadLocalWithUserContext.java

@@ -10,7 +10,7 @@ public class ThreadLocalWithUserContext implements Runnable {
     private final Integer userId;
     private UserRepository userRepository = new UserRepository();
 
-    public ThreadLocalWithUserContext(Integer userId) {
+    ThreadLocalWithUserContext(Integer userId) {
         this.userId = userId;
     }
 

core-java-concurrency/src/main/java/com/baeldung/threadlocal/UserRepository.java

@@ -4,7 +4,7 @@ import java.util.UUID;
 
 
 public class UserRepository {
-    public String getUserNameForUserId(Integer userId) {
+    String getUserNameForUserId(Integer userId) {
         return UUID.randomUUID().toString();
     }
 }

core-java-concurrency/src/main/java/com/baeldung/threadpool/CountingTask.java

@@ -2,19 +2,21 @@ package com.baeldung.threadpool;
 
 import java.util.concurrent.ForkJoinTask;
 import java.util.concurrent.RecursiveTask;
-import java.util.stream.Collectors;
 
 public class CountingTask extends RecursiveTask<Integer> {
 
     private final TreeNode node;
 
-    public CountingTask(TreeNode node) {
+    CountingTask(TreeNode node) {
         this.node = node;
     }
 
     @Override
     protected Integer compute() {
-        return node.value + node.children.stream().map(childNode -> new CountingTask(childNode).fork()).collect(Collectors.summingInt(ForkJoinTask::join));
+        return node.getValue() + node.getChildren().stream()
+          .map(childNode -> new CountingTask(childNode).fork())
+          .mapToInt(ForkJoinTask::join)
+          .sum();
     }
 
 }

core-java-concurrency/src/main/java/com/baeldung/threadpool/TreeNode.java

@@ -0,0 +1,25 @@
+package com.baeldung.threadpool;
+
+import com.google.common.collect.Sets;
+
+import java.util.Set;
+
+public class TreeNode {
+
+    private int value;
+
+    private Set<TreeNode> children;
+
+    TreeNode(int value, TreeNode... children) {
+        this.value = value;
+        this.children = Sets.newHashSet(children);
+    }
+
+    public int getValue() {
+        return value;
+    }
+
+    public Set<TreeNode> getChildren() {
+        return children;
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/transferqueue/Consumer.java

@@ -9,13 +9,12 @@ import java.util.concurrent.atomic.AtomicInteger;
 public class Consumer implements Runnable {
     private static final Logger LOG = LoggerFactory.getLogger(Consumer.class);
 
-    
     private final TransferQueue<String> transferQueue;
     private final String name;
-    private final int numberOfMessagesToConsume;
+    final int numberOfMessagesToConsume;
-    public final AtomicInteger numberOfConsumedMessages = new AtomicInteger();
+    final AtomicInteger numberOfConsumedMessages = new AtomicInteger();
 
-    public Consumer(TransferQueue<String> transferQueue, String name, int numberOfMessagesToConsume) {
+    Consumer(TransferQueue<String> transferQueue, String name, int numberOfMessagesToConsume) {
         this.transferQueue = transferQueue;
         this.name = name;
         this.numberOfMessagesToConsume = numberOfMessagesToConsume;

core-java-concurrency/src/main/java/com/baeldung/transferqueue/Producer.java

@@ -12,10 +12,10 @@ public class Producer implements Runnable {
 
     private final TransferQueue<String> transferQueue;
     private final String name;
-    private final Integer numberOfMessagesToProduce;
+    final Integer numberOfMessagesToProduce;
-    public final AtomicInteger numberOfProducedMessages = new AtomicInteger();
+    final AtomicInteger numberOfProducedMessages = new AtomicInteger();
 
-    public Producer(TransferQueue<String> transferQueue, String name, Integer numberOfMessagesToProduce) {
+    Producer(TransferQueue<String> transferQueue, String name, Integer numberOfMessagesToProduce) {
         this.transferQueue = transferQueue;
         this.name = name;
         this.numberOfMessagesToProduce = numberOfMessagesToProduce;