added files for BidiMapUnitTest

asciidoctor/README.md

@@ -0,0 +1,3 @@
+### Relevant articles
+
+- [Introduction to Asciidoctor](http://www.baeldung.com/introduction-to-asciidoctor)

asciidoctor/pom.xml

@@ -0,0 +1,56 @@
+<?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">
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>asciidoctor</artifactId>
+    <name>asciidoctor</name>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.asciidoctor</groupId>
+                <artifactId>asciidoctor-maven-plugin</artifactId>
+                <version>1.5.5</version>
+                <dependencies>
+                    <dependency>
+                        <groupId>org.asciidoctor</groupId>
+                        <artifactId>asciidoctorj-pdf</artifactId>
+                        <version>1.5.0-alpha.15</version>
+                    </dependency>
+                </dependencies>
+                <executions>
+                    <execution>
+                        <id>output-pdf</id>
+                        <phase>generate-resources</phase>
+                        <goals>
+                            <goal>process-asciidoc</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <sourceDirectory>src/docs/asciidoc</sourceDirectory>
+                    <outputDirectory>target/docs/asciidoc</outputDirectory>
+                    <backend>pdf</backend>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <dependencies>        
+        <dependency>
+            <groupId>org.asciidoctor</groupId>
+            <artifactId>asciidoctorj</artifactId>
+            <version>1.5.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.asciidoctor</groupId>
+            <artifactId>asciidoctorj-pdf</artifactId>
+            <version>1.5.0-alpha.11</version>
+        </dependency>        
+    </dependencies>
+</project>

camel-api/README.md

@@ -0,0 +1,15 @@
+Example for the Article on Camel API with SpringBoot
+
+to start up, run:
+	mvn spring-boot:run
+	
+them, do a POST http request to:
+	http://localhost:8080/camel/api/bean 
+
+with the HEADER: Content-Type: application/json, 
+
+and a BODY Payload like {"id": 1,"name": "World"}
+
+and we will get a return code of 201 and the response: Hello, World - if the transform() method from Application class is uncommented and the process() method is commented
+
+or return code of 201 and the response: {"id": 10,"name": "Hello, World"} - if the transform() method from Application class is commented and the process() method is uncommented 

camel-api/pom.xml

@@ -0,0 +1,80 @@
+<?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.example</groupId>
+	<artifactId>spring-boot-camel</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+
+	<name>Spring-Boot - Camel API</name>
+
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+		<maven-compiler-plugin.version>3.6.0</maven-compiler-plugin.version>
+		<maven-surefire-plugin.version>2.19.1</maven-surefire-plugin.version>
+		<camel.version>2.19.1</camel.version>
+	    <spring-boot-starter.version>1.5.4.RELEASE</spring-boot-starter.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-servlet-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-jackson-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-swagger-java-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.camel</groupId>
+			<artifactId>camel-spring-boot-starter</artifactId>
+			<version>${camel.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+			<version>${spring-boot-starter.version}</version>
+		</dependency>
+	</dependencies>
+	
+	<build>
+		<defaultGoal>spring-boot:run</defaultGoal>
+
+		<plugins>
+			<plugin>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>${maven-compiler-plugin.version}</version>
+				<configuration>
+					<source>1.8</source>
+					<target>1.8</target>
+				</configuration>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<version>${maven-surefire-plugin.version}</version>
+			</plugin>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+				<version>${spring-boot-starter.version}</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>repackage</goal>
+						</goals>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
+</project>

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

@@ -0,0 +1,104 @@
+package com.baeldung.camel;
+
+import javax.ws.rs.core.MediaType;
+
+import org.apache.camel.CamelContext;
+import org.apache.camel.Exchange;
+import org.apache.camel.Processor;
+import org.apache.camel.builder.RouteBuilder;
+import org.apache.camel.component.servlet.CamelHttpTransportServlet;
+import org.apache.camel.impl.DefaultCamelContext;
+import org.apache.camel.model.rest.RestBindingMode;
+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 {
+
+    @Value("${server.port}")
+    String serverPort;
+    
+    @Value("${baeldung.api.path}")
+    String contextPath;
+    
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+
+    @Bean
+    ServletRegistrationBean servletRegistrationBean() {
+        ServletRegistrationBean servlet = new ServletRegistrationBean(new CamelHttpTransportServlet(), contextPath+"/*");
+        servlet.setName("CamelServlet");
+        return servlet;
+    }
+
+
+    @Component
+    class RestApi extends RouteBuilder {
+
+        @Override
+        public void configure() {
+
+            CamelContext context = new DefaultCamelContext();
+
+            
+            // http://localhost:8080/camel/api-doc
+            restConfiguration().contextPath(contextPath) //
+                .port(serverPort)
+                .enableCORS(true)
+                .apiContextPath("/api-doc")
+                .apiProperty("api.title", "Test REST API")
+                .apiProperty("api.version", "v1")
+                .apiProperty("cors", "true") // cross-site
+                .apiContextRouteId("doc-api")
+                .component("servlet")
+                .bindingMode(RestBindingMode.json)
+                .dataFormatProperty("prettyPrint", "true");
+/** 
+The Rest DSL supports automatic binding json/xml contents to/from POJOs using Camels Data Format.
+By default the binding mode is off, meaning there is no automatic 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. 
+This allows you, as a developer, to work with the POJOs in Java code.
+*/         
+            
+            rest("/api/").description("Teste REST Service")
+                .id("api-route")
+                .post("/bean")
+                .produces(MediaType.APPLICATION_JSON)
+                .consumes(MediaType.APPLICATION_JSON)
+//                .get("/hello/{place}")
+                .bindingMode(RestBindingMode.auto)
+                .type(MyBean.class)
+                .enableCORS(true)
+//                .outType(OutBean.class)
+
+                .to("direct:remoteService");
+            
+       
+            from("direct:remoteService")
+                .routeId("direct-route")
+                .tracing()
+                .log(">>> ${body.id}")
+                .log(">>> ${body.name}")
+//                .transform().simple("blue ${in.body.name}")                
+                .process(new Processor() {
+                    @Override
+                    public void process(Exchange exchange) throws Exception {
+                        MyBean bodyIn = (MyBean) exchange.getIn().getBody();
+                        
+                        ExampleServices.example(bodyIn);
+
+                        exchange.getIn().setBody(bodyIn);
+                    }
+                })
+                .setHeader(Exchange.HTTP_RESPONSE_CODE, constant(201));
+        }
+    }
+}

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

@@ -0,0 +1,15 @@
+package com.baeldung.camel;
+
+/**
+ * a Mock class to show how some other layer
+ * (a persistence layer, for instance)
+ * could be used insida a Camel
+ * 
+ */
+public class ExampleServices {
+
+    public static void example(MyBean bodyIn) {
+        bodyIn.setName( "Hello, " + bodyIn.getName() );
+        bodyIn.setId(bodyIn.getId()*10);
+    }
+}

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

@@ -0,0 +1,18 @@
+package com.baeldung.camel;
+
+public class MyBean {
+    private Integer id;
+    private String name;
+    public Integer getId() {
+        return id;
+    }
+    public void setId(Integer id) {
+        this.id = id;
+    }
+    public String getName() {
+        return name;
+    }
+    public void setName(String name) {
+        this.name = name;
+    }
+}

camel-api/src/main/resources/application.properties

@@ -0,0 +1,15 @@
+logging.config=classpath:logback.xml
+
+# the options from org.apache.camel.spring.boot.CamelConfigurationProperties can be configured here
+camel.springboot.name=MyCamel
+
+# lets listen on all ports to ensure we can be invoked from the pod IP
+server.address=0.0.0.0
+management.address=0.0.0.0
+
+# lets use a different management port in case you need to listen to HTTP requests on 8080
+management.port=8081
+
+# disable all management enpoints except health
+endpoints.enabled = true
+endpoints.health.enabled = true

camel-api/src/main/resources/application.yml

@@ -0,0 +1,27 @@
+server:
+  port: 8080
+
+# for example purposes of Camel version 2.18 and below
+baeldung:
+  api:
+    path: '/camel' 
+
+camel:
+  springboot:
+    # The Camel context name
+    name: ServicesRest
+
+# Binding health checks to a different port
+management:
+  port: 8081
+
+# disable all management enpoints except health
+endpoints:
+  enabled: false
+  health:
+    enabled: true
+
+# The application configuration properties
+quickstart:
+  generateOrderPeriod: 10s
+  processOrderPeriod: 30s

camel-api/src/main/resources/logback.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE xml>
+<configuration>
+
+  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+    <!-- encoders are assigned the type
+         ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
+    <encoder>
+      <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <root level="info">
+    <appender-ref ref="STDOUT" />
+  </root>
+
+</configuration>

core-java/pom.xml

@@ -327,6 +327,22 @@
                 </executions>
             </plugin>
 
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.6.0</version>
+                <configuration>
+                    <executable>java</executable>
+                    <mainClass>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</mainClass>
+                    <arguments>
+                        <argument>-Xmx300m</argument>
+                        <argument>-XX:+UseParallelGC</argument>
+                        <argument>-classpath</argument>
+                        <classpath/>
+                        <argument>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</argument>
+                    </arguments>
+                </configuration>
+            </plugin>
         </plugins>
 
     </build>

core-java/src/main/java/com/baeldung/concurrent/blockingqueue/NumbersConsumer.java

@@ -6,7 +6,7 @@ public class NumbersConsumer implements Runnable {
     private final BlockingQueue<Integer> queue;
     private final int poisonPill;
 
-    public NumbersConsumer(BlockingQueue<Integer> queue, int poisonPill) {
+    NumbersConsumer(BlockingQueue<Integer> queue, int poisonPill) {
         this.queue = queue;
         this.poisonPill = poisonPill;
     }

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

@@ -9,7 +9,7 @@ public class NumbersProducer implements Runnable {
     private final int poisonPill;
     private final int poisonPillPerProducer;
 
-    public NumbersProducer(BlockingQueue<Integer> numbersQueue, int poisonPill, int poisonPillPerProducer) {
+    NumbersProducer(BlockingQueue<Integer> numbersQueue, int poisonPill, int poisonPillPerProducer) {
         this.numbersQueue = numbersQueue;
         this.poisonPill = poisonPill;
         this.poisonPillPerProducer = poisonPillPerProducer;

core-java/src/main/java/com/baeldung/concurrent/countdownlatch/BrokenWorker.java

@@ -7,7 +7,7 @@ public class BrokenWorker implements Runnable {
     private final List<String> outputScraper;
     private final CountDownLatch countDownLatch;
 
-    public BrokenWorker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
+    BrokenWorker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
         this.outputScraper = outputScraper;
         this.countDownLatch = countDownLatch;
     }

core-java/src/main/java/com/baeldung/concurrent/countdownlatch/WaitingWorker.java

@@ -10,7 +10,7 @@ public class WaitingWorker implements Runnable {
     private final CountDownLatch callingThreadBlocker;
     private final CountDownLatch completedThreadCounter;
 
-    public WaitingWorker(final List<String> outputScraper, final CountDownLatch readyThreadCounter, final CountDownLatch callingThreadBlocker, CountDownLatch completedThreadCounter) {
+    WaitingWorker(final List<String> outputScraper, final CountDownLatch readyThreadCounter, final CountDownLatch callingThreadBlocker, CountDownLatch completedThreadCounter) {
 
         this.outputScraper = outputScraper;
         this.readyThreadCounter = readyThreadCounter;

core-java/src/main/java/com/baeldung/concurrent/countdownlatch/Worker.java

@@ -7,7 +7,7 @@ public class Worker implements Runnable {
     private final List<String> outputScraper;
     private final CountDownLatch countDownLatch;
 
-    public Worker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
+    Worker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
         this.outputScraper = outputScraper;
         this.countDownLatch = countDownLatch;
     }

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

@@ -0,0 +1,81 @@
+package com.baeldung.concurrent.cyclicbarrier;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+
+public class CyclicBarrierDemo {
+
+    private CyclicBarrier cyclicBarrier;
+    private List<List<Integer>> partialResults = Collections.synchronizedList(new ArrayList<>());
+    private Random random = new Random();
+    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 "
+                + NUM_PARTIAL_RESULTS + " partial results each");
+        for (int i = 0; i < NUM_WORKERS; i++) {
+            Thread worker = new Thread(new NumberCruncherThread());
+            worker.setName("Thread " + i);
+            worker.start();
+        }
+    }
+
+    class NumberCruncherThread implements Runnable {
+
+        @Override
+        public void run() {
+            String thisThreadName = Thread.currentThread().getName();
+            List<Integer> partialResult = new ArrayList<>();
+            for (int i = 0; i < NUM_PARTIAL_RESULTS; i++) {
+                Integer num = random.nextInt(10);
+                System.out.println(thisThreadName
+                        + ": Crunching some numbers! Final result - " + num);
+                partialResult.add(num);
+            }
+            partialResults.add(partialResult);
+            try {
+                System.out.println(thisThreadName + " waiting for others to reach barrier.");
+                cyclicBarrier.await();
+            } catch (InterruptedException | BrokenBarrierException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+
+    class AggregatorThread implements Runnable {
+
+        @Override
+        public void run() {
+            String thisThreadName = Thread.currentThread().getName();
+            System.out.println(thisThreadName + ": Computing final sum of " + NUM_WORKERS
+                    + " 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+" ");
+                    sum += partialResult;
+                }
+                System.out.println();
+            }
+            System.out.println(Thread.currentThread().getName() + ": Final result = " + sum);
+        }
+
+    }
+
+    public static void main(String[] args) {
+        CyclicBarrierDemo play = new CyclicBarrierDemo();
+        play.runSimulation(5, 3);
+    }
+
+}

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

@@ -9,7 +9,7 @@ public class DelayObject implements Delayed {
     private String data;
     private long startTime;
 
-    public DelayObject(String data, long delayInMilliseconds) {
+    DelayObject(String data, long delayInMilliseconds) {
         this.data = data;
         this.startTime = System.currentTimeMillis() + delayInMilliseconds;
     }

core-java/src/main/java/com/baeldung/concurrent/delayqueue/DelayQueueConsumer.java

@@ -7,9 +7,9 @@ import java.util.concurrent.atomic.AtomicInteger;
 public class DelayQueueConsumer implements Runnable {
     private BlockingQueue<DelayObject> queue;
     private final Integer numberOfElementsToTake;
-    public final AtomicInteger numberOfConsumedElements = new AtomicInteger();
+    final AtomicInteger numberOfConsumedElements = new AtomicInteger();
 
-    public DelayQueueConsumer(BlockingQueue<DelayObject> queue, Integer numberOfElementsToTake) {
+    DelayQueueConsumer(BlockingQueue<DelayObject> queue, Integer numberOfElementsToTake) {
         this.queue = queue;
         this.numberOfElementsToTake = numberOfElementsToTake;
     }

core-java/src/main/java/com/baeldung/concurrent/delayqueue/DelayQueueProducer.java

@@ -9,7 +9,7 @@ public class DelayQueueProducer implements Runnable {
     private final Integer numberOfElementsToProduce;
     private final Integer delayOfEachProducedMessageMilliseconds;
 
-    public DelayQueueProducer(BlockingQueue<DelayObject> queue,
+    DelayQueueProducer(BlockingQueue<DelayObject> queue,
                        Integer numberOfElementsToProduce,
                        Integer delayOfEachProducedMessageMilliseconds) {
         this.queue = queue;

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

@@ -5,7 +5,7 @@ public class Philosopher implements Runnable {
     private final Object leftFork;
     private final Object rightFork;
 
-    public Philosopher(Object left, Object right) {
+    Philosopher(Object left, Object right) {
         this.leftFork = left;
         this.rightFork = right;
     }
@@ -30,7 +30,6 @@ public class Philosopher implements Runnable {
             }
         } catch (InterruptedException e) {
             Thread.currentThread().interrupt();
-            return;
         }
     }
 }

core-java/src/main/java/com/baeldung/concurrent/future/FactorialSquareCalculator.java

@@ -7,7 +7,7 @@ public class FactorialSquareCalculator extends RecursiveTask<Integer> {
 
     final private Integer n;
 
-    public FactorialSquareCalculator(Integer n) {
+    FactorialSquareCalculator(Integer n) {
         this.n = n;
     }
 

core-java/src/main/java/com/baeldung/concurrent/future/SquareCalculator.java

@@ -3,15 +3,15 @@ package com.baeldung.concurrent.future;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
 
-public class SquareCalculator {
+class SquareCalculator {
 
     private final ExecutorService executor;
 
-    public SquareCalculator(ExecutorService executor) {
+    SquareCalculator(ExecutorService executor) {
         this.executor = executor;
     }
 
-    public Future<Integer> calculate(Integer input) {
+    Future<Integer> calculate(Integer input) {
         return executor.submit(() -> {
             Thread.sleep(1000);
             return input * input;

core-java/src/main/java/com/baeldung/concurrent/locks/ReentrantLockWithCondition.java

@@ -13,23 +13,23 @@ import static java.lang.Thread.sleep;
 
 public class ReentrantLockWithCondition {
 
-	static Logger logger = LoggerFactory.getLogger(ReentrantLockWithCondition.class);
+    private static Logger LOG = LoggerFactory.getLogger(ReentrantLockWithCondition.class);
 
-	Stack<String> stack = new Stack<>();
+    private Stack<String> stack = new Stack<>();
-	int CAPACITY = 5;
+    private static final int CAPACITY = 5;
 
-	ReentrantLock lock = new ReentrantLock();
+    private ReentrantLock lock = new ReentrantLock();
-	Condition stackEmptyCondition = lock.newCondition();
+    private Condition stackEmptyCondition = lock.newCondition();
-	Condition stackFullCondition = lock.newCondition();
+    private Condition stackFullCondition = lock.newCondition();
 
-	public void pushToStack(String item) throws InterruptedException {
+    private void pushToStack(String item) throws InterruptedException {
         try {
             lock.lock();
             if (stack.size() == CAPACITY) {
-				logger.info(Thread.currentThread().getName() + " wait on stack full");
+                LOG.info(Thread.currentThread().getName() + " wait on stack full");
                 stackFullCondition.await();
             }
-			logger.info("Pushing the item " + item);
+            LOG.info("Pushing the item " + item);
             stack.push(item);
             stackEmptyCondition.signalAll();
         } finally {
@@ -38,11 +38,11 @@ public class ReentrantLockWithCondition {
 
     }
 
-	public String popFromStack() throws InterruptedException {
+    private String popFromStack() throws InterruptedException {
         try {
             lock.lock();
             if (stack.size() == 0) {
-				logger.info(Thread.currentThread().getName() + " wait on stack empty");
+                LOG.info(Thread.currentThread().getName() + " wait on stack empty");
                 stackEmptyCondition.await();
             }
             return stack.pop();
@@ -70,7 +70,7 @@ public class ReentrantLockWithCondition {
         service.execute(() -> {
             for (int i = 0; i < 10; i++) {
                 try {
-					logger.info("Item popped " + object.popFromStack());
+                    LOG.info("Item popped " + object.popFromStack());
                 } catch (InterruptedException e) {
                     e.printStackTrace();
                 }

core-java/src/main/java/com/baeldung/concurrent/locks/SharedObjectWithLock.java

@@ -12,48 +12,48 @@ import static java.lang.Thread.sleep;
 
 public class SharedObjectWithLock {
 
-	Logger logger = LoggerFactory.getLogger(SharedObjectWithLock.class);
+    private static final Logger LOG = LoggerFactory.getLogger(SharedObjectWithLock.class);
 
-	ReentrantLock lock = new ReentrantLock(true);
+    private ReentrantLock lock = new ReentrantLock(true);
 
-	int counter = 0;
+    private int counter = 0;
 
-	public void perform() {
+    void perform() {
 
         lock.lock();
-		logger.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
+        LOG.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
         try {
-			logger.info("Thread - " + Thread.currentThread().getName() + " processing");
+            LOG.info("Thread - " + Thread.currentThread().getName() + " processing");
             counter++;
         } catch (Exception exception) {
-			logger.error(" Interrupted Exception ", exception);
+            LOG.error(" Interrupted Exception ", exception);
         } finally {
             lock.unlock();
-			logger.info("Thread - " + Thread.currentThread().getName() + " released the lock");
+            LOG.info("Thread - " + Thread.currentThread().getName() + " released the lock");
         }
     }
 
-	public void performTryLock() {
+    private void performTryLock() {
 
-		logger.info("Thread - " + Thread.currentThread().getName() + " attempting to acquire the lock");
+        LOG.info("Thread - " + Thread.currentThread().getName() + " attempting to acquire the lock");
         try {
             boolean isLockAcquired = lock.tryLock(2, TimeUnit.SECONDS);
             if (isLockAcquired) {
                 try {
-					logger.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
+                    LOG.info("Thread - " + Thread.currentThread().getName() + " acquired the lock");
 
-					logger.info("Thread - " + Thread.currentThread().getName() + " processing");
+                    LOG.info("Thread - " + Thread.currentThread().getName() + " processing");
                     sleep(1000);
                 } finally {
                     lock.unlock();
-					logger.info("Thread - " + Thread.currentThread().getName() + " released the lock");
+                    LOG.info("Thread - " + Thread.currentThread().getName() + " released the lock");
 
                 }
             }
         } catch (InterruptedException exception) {
-			logger.error(" Interrupted Exception ", exception);
+            LOG.error(" Interrupted Exception ", exception);
         }
-		logger.info("Thread - " + Thread.currentThread().getName() + " could not acquire the lock");
+        LOG.info("Thread - " + Thread.currentThread().getName() + " could not acquire the lock");
     }
 
     public ReentrantLock getLock() {
@@ -78,12 +78,8 @@ public class SharedObjectWithLock {
         final ExecutorService service = Executors.newFixedThreadPool(threadCount);
         final SharedObjectWithLock object = new SharedObjectWithLock();
 
-		service.execute(() -> {
+        service.execute(object::perform);
-			object.perform();
+        service.execute(object::performTryLock);
-		});
-		service.execute(() -> {
-			object.performTryLock();
-		});
 
         service.shutdown();
 

core-java/src/main/java/com/baeldung/concurrent/locks/StampedLockDemo.java

@@ -12,8 +12,8 @@ import java.util.concurrent.locks.StampedLock;
 import static java.lang.Thread.sleep;
 
 public class StampedLockDemo {
-	Map<String, String> map = new HashMap<>();
+    private Map<String, String> map = new HashMap<>();
-	Logger logger = LoggerFactory.getLogger(StampedLockDemo.class);
+    private Logger logger = LoggerFactory.getLogger(StampedLockDemo.class);
 
     private final StampedLock lock = new StampedLock();
 
@@ -44,7 +44,7 @@ public class StampedLockDemo {
 
     }
 
-	public String readWithOptimisticLock(String key) throws InterruptedException {
+    private String readWithOptimisticLock(String key) throws InterruptedException {
         long stamp = lock.tryOptimisticRead();
         String value = map.get(key);
 

core-java/src/main/java/com/baeldung/concurrent/locks/SynchronizedHashMapWithRWLock.java

@@ -15,8 +15,8 @@ import static java.lang.Thread.sleep;
 
 public class SynchronizedHashMapWithRWLock {
 
-	static Map<String, String> syncHashMap = new HashMap<>();
+    private static Map<String, String> syncHashMap = new HashMap<>();
-	Logger logger = LoggerFactory.getLogger(SynchronizedHashMapWithRWLock.class);
+    private Logger logger = LoggerFactory.getLogger(SynchronizedHashMapWithRWLock.class);
 
     private final ReadWriteLock lock = new ReentrantReadWriteLock();
     private final Lock readLock = lock.readLock();
@@ -84,7 +84,7 @@ public class SynchronizedHashMapWithRWLock {
 
         SynchronizedHashMapWithRWLock object;
 
-		public Reader(SynchronizedHashMapWithRWLock object) {
+        Reader(SynchronizedHashMapWithRWLock object) {
             this.object = object;
         }
 

core-java/src/main/java/com/baeldung/concurrent/semaphores/CounterUsingMutex.java

@@ -0,0 +1,31 @@
+package com.baeldung.concurrent.semaphores;
+
+import java.util.concurrent.Semaphore;
+
+class CounterUsingMutex {
+
+    private final Semaphore mutex;
+    private int count;
+
+    CounterUsingMutex() {
+        mutex = new Semaphore(1);
+        count = 0;
+    }
+
+    void increase() throws InterruptedException {
+        mutex.acquire();
+        this.count = this.count + 1;
+        Thread.sleep(1000);
+        mutex.release();
+
+    }
+
+    int getCount() {
+        return this.count;
+    }
+
+    boolean hasQueuedThreads() {
+        return mutex.hasQueuedThreads();
+    }
+
+}

core-java/src/main/java/com/baeldung/concurrent/semaphores/DelayQueueUsingTimedSemaphore.java

@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.semaphores;
+
+import java.util.concurrent.TimeUnit;
+
+import org.apache.commons.lang3.concurrent.TimedSemaphore;
+
+class DelayQueueUsingTimedSemaphore {
+
+    private final TimedSemaphore semaphore;
+
+    DelayQueueUsingTimedSemaphore(long period, int slotLimit) {
+        semaphore = new TimedSemaphore(period, TimeUnit.SECONDS, slotLimit);
+    }
+
+    boolean tryAdd() {
+        return semaphore.tryAcquire();
+    }
+
+    int availableSlots() {
+        return semaphore.getAvailablePermits();
+    }
+
+}

core-java/src/main/java/com/baeldung/concurrent/semaphores/LoginQueueUsingSemaphore.java

@@ -0,0 +1,25 @@
+package com.baeldung.concurrent.semaphores;
+
+import java.util.concurrent.Semaphore;
+
+class LoginQueueUsingSemaphore {
+
+    private final Semaphore semaphore;
+
+    LoginQueueUsingSemaphore(int slotLimit) {
+        semaphore = new Semaphore(slotLimit);
+    }
+
+    boolean tryLogin() {
+        return semaphore.tryAcquire();
+    }
+
+    void logout() {
+        semaphore.release();
+    }
+
+    int availableSlots() {
+        return semaphore.availablePermits();
+    }
+
+}

core-java/src/main/java/com/baeldung/concurrent/skiplist/Event.java

@@ -2,20 +2,20 @@ package com.baeldung.concurrent.skiplist;
 
 import java.time.ZonedDateTime;
 
-public class Event {
+class Event {
     private final ZonedDateTime eventTime;
     private final String content;
 
-    public Event(ZonedDateTime eventTime, String content) {
+    Event(ZonedDateTime eventTime, String content) {
         this.eventTime = eventTime;
         this.content = content;
     }
 
-    public ZonedDateTime getEventTime() {
+    ZonedDateTime getEventTime() {
         return eventTime;
     }
 
-    public String getContent() {
+    String getContent() {
         return content;
     }
 }

core-java/src/main/java/com/baeldung/concurrent/skiplist/EventWindowSort.java

@@ -5,21 +5,21 @@ import java.util.Comparator;
 import java.util.concurrent.ConcurrentNavigableMap;
 import java.util.concurrent.ConcurrentSkipListMap;
 
-public class EventWindowSort {
+class EventWindowSort {
     private final ConcurrentSkipListMap<ZonedDateTime, String> events
       = new ConcurrentSkipListMap<>(Comparator.comparingLong(value -> value.toInstant().toEpochMilli()));
 
-    public void acceptEvent(Event event) {
+    void acceptEvent(Event event) {
         events.put(event.getEventTime(), event.getContent());
     }
 
-    public ConcurrentNavigableMap<ZonedDateTime, String> getEventsFromLastMinute() {
+    ConcurrentNavigableMap<ZonedDateTime, String> getEventsFromLastMinute() {
         return events.tailMap(ZonedDateTime
           .now()
           .minusMinutes(1));
     }
 
-    public ConcurrentNavigableMap<ZonedDateTime, String> getEventsOlderThatOneMinute() {
+    ConcurrentNavigableMap<ZonedDateTime, String> getEventsOlderThatOneMinute() {
         return events.headMap(ZonedDateTime
           .now()
           .minusMinutes(1));

core-java/src/main/java/com/baeldung/concurrent/sleepwait/WaitSleepExample.java

@@ -13,10 +13,10 @@ public class WaitSleepExample {
     private static final Object LOCK = new Object();
 
     public static void main(String... args) throws InterruptedException {
-        sleepWaitInSyncronizedBlocks();
+        sleepWaitInSynchronizedBlocks();
     }
 
-    private static void sleepWaitInSyncronizedBlocks() throws InterruptedException {
+    private static void sleepWaitInSynchronizedBlocks() throws InterruptedException {
         Thread.sleep(1000); // called on the thread
         LOG.debug("Thread '" + Thread.currentThread().getName() + "' is woken after sleeping for 1 second");
 

core-java/src/main/java/com/baeldung/concurrent/synchronize/BaeldungSynchronizedBlocks.java

@@ -5,13 +5,13 @@ public class BaeldungSynchronizedBlocks {
     private int count = 0;
     private static int staticCount = 0;
 
-    public void performSynchronisedTask() {
+    void performSynchronisedTask() {
         synchronized (this) {
             setCount(getCount() + 1);
         }
     }
 
-    public static void performStaticSyncTask() {
+    static void performStaticSyncTask() {
         synchronized (BaeldungSynchronizedBlocks.class) {
             setStaticCount(getStaticCount() + 1);
         }
@@ -25,11 +25,11 @@ public class BaeldungSynchronizedBlocks {
         this.count = count;
     }
 
-    public static int getStaticCount() {
+    static int getStaticCount() {
         return staticCount;
     }
 
-    public static void setStaticCount(int staticCount) {
+    private static void setStaticCount(int staticCount) {
         BaeldungSynchronizedBlocks.staticCount = staticCount;
     }
 }

core-java/src/main/java/com/baeldung/concurrent/synchronize/BaeldungSynchronizedMethods.java

@@ -5,17 +5,17 @@ public class BaeldungSynchronizedMethods {
     private int sum = 0;
     private int syncSum = 0;
 
-    public static int staticSum = 0;
+    static int staticSum = 0;
 
-    public void calculate() {
+    void calculate() {
         setSum(getSum() + 1);
     }
 
-    public synchronized void synchronisedCalculate() {
+    synchronized void synchronisedCalculate() {
         setSyncSum(getSyncSum() + 1);
     }
 
-    public static synchronized void syncStaticCalculate() {
+    static synchronized void syncStaticCalculate() {
         staticSum = staticSum + 1;
     }
 
@@ -27,11 +27,11 @@ public class BaeldungSynchronizedMethods {
         this.sum = sum;
     }
 
-    public int getSyncSum() {
+    int getSyncSum() {
         return syncSum;
     }
 
-    public void setSyncSum(int syncSum) {
+    private void setSyncSum(int syncSum) {
         this.syncSum = syncSum;
     }
 }

core-java/src/main/java/com/baeldung/datetime/UseLocalDate.java

@@ -6,40 +6,40 @@ import java.time.LocalDateTime;
 import java.time.temporal.ChronoUnit;
 import java.time.temporal.TemporalAdjusters;
 
-public class UseLocalDate {
+class UseLocalDate {
 
-    public LocalDate getLocalDateUsingFactoryOfMethod(int year, int month, int dayOfMonth) {
+    LocalDate getLocalDateUsingFactoryOfMethod(int year, int month, int dayOfMonth) {
         return LocalDate.of(year, month, dayOfMonth);
     }
 
-    public LocalDate getLocalDateUsingParseMethod(String representation) {
+    LocalDate getLocalDateUsingParseMethod(String representation) {
         return LocalDate.parse(representation);
     }
 
-    public LocalDate getLocalDateFromClock() {
+    LocalDate getLocalDateFromClock() {
         LocalDate localDate = LocalDate.now();
         return localDate;
     }
 
-    public LocalDate getNextDay(LocalDate localDate) {
+    LocalDate getNextDay(LocalDate localDate) {
         return localDate.plusDays(1);
     }
 
-    public LocalDate getPreviousDay(LocalDate localDate) {
+    LocalDate getPreviousDay(LocalDate localDate) {
         return localDate.minus(1, ChronoUnit.DAYS);
     }
 
-    public DayOfWeek getDayOfWeek(LocalDate localDate) {
+    DayOfWeek getDayOfWeek(LocalDate localDate) {
         DayOfWeek day = localDate.getDayOfWeek();
         return day;
     }
 
-    public LocalDate getFirstDayOfMonth() {
+    LocalDate getFirstDayOfMonth() {
         LocalDate firstDayOfMonth = LocalDate.now().with(TemporalAdjusters.firstDayOfMonth());
         return firstDayOfMonth;
     }
 
-    public LocalDateTime getStartOfDay(LocalDate localDate) {
+    LocalDateTime getStartOfDay(LocalDate localDate) {
         LocalDateTime startofDay = localDate.atStartOfDay();
         return startofDay;
     }

core-java/src/main/java/com/baeldung/datetime/UseLocalTime.java

@@ -5,31 +5,27 @@ import java.time.temporal.ChronoUnit;
 
 public class UseLocalTime {
 
-    public LocalTime getLocalTimeUsingFactoryOfMethod(int hour, int min, int seconds) {
+    LocalTime getLocalTimeUsingFactoryOfMethod(int hour, int min, int seconds) {
-        LocalTime localTime = LocalTime.of(hour, min, seconds);
+        return LocalTime.of(hour, min, seconds);
-        return localTime;
     }
 
-    public LocalTime getLocalTimeUsingParseMethod(String timeRepresentation) {
+    LocalTime getLocalTimeUsingParseMethod(String timeRepresentation) {
-        LocalTime localTime = LocalTime.parse(timeRepresentation);
+        return LocalTime.parse(timeRepresentation);
-        return localTime;
     }
 
-    public LocalTime getLocalTimeFromClock() {
+    private LocalTime getLocalTimeFromClock() {
-        LocalTime localTime = LocalTime.now();
+        return LocalTime.now();
-        return localTime;
     }
 
-    public LocalTime addAnHour(LocalTime localTime) {
+    LocalTime addAnHour(LocalTime localTime) {
-        LocalTime newTime = localTime.plus(1, ChronoUnit.HOURS);
+        return localTime.plus(1, ChronoUnit.HOURS);
-        return newTime;
     }
 
-    public int getHourFromLocalTime(LocalTime localTime) {
+    int getHourFromLocalTime(LocalTime localTime) {
         return localTime.getHour();
     }
 
-    public LocalTime getLocalTimeWithMinuteSetToValue(LocalTime localTime, int minute) {
+    LocalTime getLocalTimeWithMinuteSetToValue(LocalTime localTime, int minute) {
         return localTime.withMinute(minute);
     }
 }

core-java/src/main/java/com/baeldung/datetime/UsePeriod.java

@@ -3,13 +3,13 @@ package com.baeldung.datetime;
 import java.time.LocalDate;
 import java.time.Period;
 
-public class UsePeriod {
+class UsePeriod {
 
-    public LocalDate modifyDates(LocalDate localDate, Period period) {
+    LocalDate modifyDates(LocalDate localDate, Period period) {
         return localDate.plus(period);
     }
 
-    public Period getDifferenceBetweenDates(LocalDate localDate1, LocalDate localDate2) {
+    Period getDifferenceBetweenDates(LocalDate localDate1, LocalDate localDate2) {
         return Period.between(localDate1, localDate2);
     }
 }

core-java/src/main/java/com/baeldung/datetime/UseToInstant.java

@@ -8,12 +8,10 @@ import java.util.Date;
 public class UseToInstant {
 
     public LocalDateTime convertDateToLocalDate(Date date) {
-        LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
+        return LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
-        return localDateTime;
     }
 
     public LocalDateTime convertDateToLocalDate(Calendar calendar) {
-        LocalDateTime localDateTime = LocalDateTime.ofInstant(calendar.toInstant(), ZoneId.systemDefault());
+        return LocalDateTime.ofInstant(calendar.toInstant(), ZoneId.systemDefault());
-        return localDateTime;
     }
 }

core-java/src/main/java/com/baeldung/datetime/UseZonedDateTime.java

@@ -4,10 +4,9 @@ import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
 
-public class UseZonedDateTime {
+class UseZonedDateTime {
 
-    public ZonedDateTime getZonedDateTime(LocalDateTime localDateTime, ZoneId zoneId) {
+    ZonedDateTime getZonedDateTime(LocalDateTime localDateTime, ZoneId zoneId) {
-        ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime, zoneId);
+        return ZonedDateTime.of(localDateTime, zoneId);
-        return zonedDateTime;
     }
 }

core-java/src/main/java/com/baeldung/dirmonitoring/DirectoryMonitoringExample.java

@@ -13,8 +13,7 @@ public class DirectoryMonitoringExample {
 
     private static final Logger LOG = LoggerFactory.getLogger(DirectoryMonitoringExample.class);
 
-
+    private static final int POLL_INTERVAL = 500;
-    public static final int POLL_INTERVAL = 500;
 
     public static void main(String[] args) throws Exception {
         FileAlterationObserver observer = new FileAlterationObserver(System.getProperty("user.home"));

core-java/src/main/java/com/baeldung/doublecolon/Computer.java

@@ -6,12 +6,12 @@ public class Computer {
     private String color;
     private Integer healty;
 
-    public Computer(final int age, final String color) {
+    Computer(final int age, final String color) {
         this.age = age;
         this.color = color;
     }
 
-    public Computer(final Integer age, final String color, final Integer healty) {
+    Computer(final Integer age, final String color, final Integer healty) {
         this.age = age;
         this.color = color;
         this.healty = healty;
@@ -28,7 +28,7 @@ public class Computer {
         this.age = age;
     }
 
-    public String getColor() {
+    String getColor() {
         return color;
     }
 
@@ -36,11 +36,11 @@ public class Computer {
         this.color = color;
     }
 
-    public Integer getHealty() {
+    Integer getHealty() {
         return healty;
     }
 
-    public void setHealty(final Integer healty) {
+    void setHealty(final Integer healty) {
         this.healty = healty;
     }
 
@@ -72,10 +72,7 @@ public class Computer {
 
         final Computer computer = (Computer) o;
 
-        if (age != null ? !age.equals(computer.age) : computer.age != null) {
+        return (age != null ? age.equals(computer.age) : computer.age == null) && (color != null ? color.equals(computer.color) : computer.color == null);
-            return false;
-        }
-        return color != null ? color.equals(computer.color) : computer.color == null;
 
     }
 

core-java/src/main/java/com/baeldung/doublecolon/ComputerUtils.java

@@ -7,8 +7,8 @@ import java.util.List;
 
 public class ComputerUtils {
 
-    public static final ComputerPredicate after2010Predicate = (c) -> (c.getAge() > 2010);
+    static final ComputerPredicate after2010Predicate = (c) -> (c.getAge() > 2010);
-    public static final ComputerPredicate blackPredicate = (c) -> "black".equals(c.getColor());
+    static final ComputerPredicate blackPredicate = (c) -> "black".equals(c.getColor());
 
     public static List<Computer> filter(final List<Computer> inventory, final ComputerPredicate p) {
 
@@ -18,7 +18,7 @@ public class ComputerUtils {
         return result;
     }
 
-    public static void repair(final Computer computer) {
+    static void repair(final Computer computer) {
         if (computer.getHealty() < 50) {
             computer.setHealty(100);
         }

core-java/src/main/java/com/baeldung/doublecolon/MacbookPro.java

@@ -13,7 +13,7 @@ public class MacbookPro extends Computer {
         super(age, color);
     }
 
-    public MacbookPro(Integer age, String color, Integer healty) {
+    MacbookPro(Integer age, String color, Integer healty) {
         super(age, color, healty);
     }
 

core-java/src/main/java/com/baeldung/dynamicproxy/TimingDynamicInvocationHandler.java

@@ -15,7 +15,7 @@ public class TimingDynamicInvocationHandler implements InvocationHandler {
 
     private Object target;
 
-    public TimingDynamicInvocationHandler(Object target) {
+    TimingDynamicInvocationHandler(Object target) {
         this.target = target;
 
         for(Method method: target.getClass().getDeclaredMethods()) {

core-java/src/main/java/com/baeldung/equalshashcode/entities/Square.java

@@ -1,10 +1,10 @@
 package com.baeldung.equalshashcode.entities;
 
-import java.awt.Color;
+import java.awt.*;
 
 public class Square extends Rectangle {
 
-    Color color;
+    private Color color;
 
     public Square(double width, Color color) {
         super(width, width);

core-java/src/main/java/com/baeldung/filesystem/jndi/LookupFSJNDI.java

@@ -8,7 +8,7 @@ import javax.naming.InitialContext;
 import javax.naming.NamingException;
 
 public class LookupFSJNDI {
-    InitialContext ctx = null;
+    private InitialContext ctx = null;
 
     public LookupFSJNDI() throws NamingException {
         super();

core-java/src/main/java/com/baeldung/map/iteration/MapIteration.java

@@ -1,58 +1,71 @@
 package com.baeldung.map.iteration;
 
-import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.Iterator;
-import java.util.List;
 import java.util.Map;
 
 public class MapIteration {
 
-    public List<String> iterateUsingEntrySet(Map<String, Integer> map) {
+    public static void main(String[] args) {
-        List<String> mapKeyValueList = new ArrayList<>();
+        MapIteration mapIteration = new MapIteration();
+        Map<String, Integer> map = new HashMap<>();
+
+        map.put("One", 1);
+        map.put("Three", 3);
+        map.put("Two", 2);
+
+        System.out.println("Iterating Keys of Map Using KeySet");
+        mapIteration.iterateKeys(map);
+
+        System.out.println("Iterating Map Using Entry Set");
+        mapIteration.iterateUsingEntrySet(map);
+
+        System.out.println("Iterating Using Iterator and Map Entry");
+        mapIteration.iterateUsingIteratorAndEntry(map);
+
+        System.out.println("Iterating Using KeySet and For Each");
+        mapIteration.iterateUsingKeySetAndForeach(map);
+
+        System.out.println("Iterating Map Using Lambda Expression");
+        mapIteration.iterateUsingLambda(map);
+
+        System.out.println("Iterating Using Stream API");
+        mapIteration.iterateUsingStreamAPI(map);
+    }
+
+    public void iterateUsingEntrySet(Map<String, Integer> map) {
         for (Map.Entry<String, Integer> entry : map.entrySet()) {
-            mapKeyValueList.add(entry.getKey() + ":" + entry.getValue());
+            System.out.println(entry.getKey() + ":" + entry.getValue());
         }
-        return mapKeyValueList;
     }
 
-    public List<String> iterateUsingLambda(Map<String, Integer> map) {
+    public void iterateUsingLambda(Map<String, Integer> map) {
-        List<String> mapKeyValueList = new ArrayList<>();
+        map.forEach((k, v) -> System.out.println((k + ":" + v)));
-        map.forEach((k, v) -> mapKeyValueList.add(k + ":" + v));
-        return mapKeyValueList;
     }
 
-    public List<String> iterateUsingIteratorAndEntry(Map<String, Integer> map) {
+    public void iterateUsingIteratorAndEntry(Map<String, Integer> map) {
-        ArrayList<String> mapKeyValueList = new ArrayList<>();
         Iterator<Map.Entry<String, Integer>> iterator = map.entrySet().iterator();
-
         while (iterator.hasNext()) {
             Map.Entry<String, Integer> pair = iterator.next();
-            mapKeyValueList.add(pair.getKey() + ":" + pair.getValue());
+            System.out.println(pair.getKey() + ":" + pair.getValue());
+        }
     }
 
-        return mapKeyValueList;
+    public void iterateUsingKeySetAndForeach(Map<String, Integer> map) {
-    }
-
-    public List<String> iterateUsingKeySetAndForeach(Map<String, Integer> map) {
-        List<String> mapKeyValueList = new ArrayList<>();
         for (String key : map.keySet()) {
-            mapKeyValueList.add(key + ":" + map.get(key));
+            System.out.println(key + ":" + map.get(key));
         }
-        return mapKeyValueList;
     }
 
-    public List<String> iterateUsingStreamAPI(Map<String, Integer> map) {
+    public void iterateUsingStreamAPI(Map<String, Integer> map) {
-        ArrayList<String> mapKeyValueList = new ArrayList<>();
+        map.entrySet().stream().forEach(e -> System.out.println(e.getKey() + ":" + e.getValue()));
-        map.entrySet().stream().forEach(e -> mapKeyValueList.add(e.getKey() + ":" + e.getValue()));
-        return mapKeyValueList;
     }
 
-    public ArrayList<String> iterateKeys(Map<String, Integer> map) {
+    public void iterateKeys(Map<String, Integer> map) {
-        ArrayList<String> mapKeyList = new ArrayList<>();
         for (String key : map.keySet()) {
-            mapKeyList.add(key);
+            System.out.println(key);
         }
-        return mapKeyList;
+
     }
 
 }

core-java/src/main/java/com/baeldung/maths/BigDecimalImpl.java

@@ -0,0 +1,18 @@
+package com.baeldung.maths;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+public class BigDecimalImpl {
+
+    public static void main(String[] args) {
+
+        BigDecimal serviceTax = new BigDecimal("56.0084578639");
+        serviceTax = serviceTax.setScale(2, RoundingMode.CEILING);
+
+        BigDecimal entertainmentTax = new BigDecimal("23.00689");
+        entertainmentTax = entertainmentTax.setScale(2, RoundingMode.FLOOR);
+
+        BigDecimal totalTax = serviceTax.add(entertainmentTax);
+    }
+}

core-java/src/main/java/com/baeldung/maths/BigIntegerImpl.java

@@ -0,0 +1,16 @@
+package com.baeldung.maths;
+
+import java.math.BigInteger;
+
+public class BigIntegerImpl {
+
+    public static void main(String[] args) {
+
+        BigInteger numStarsMilkyWay = new BigInteger("8731409320171337804361260816606476");
+        BigInteger numStarsAndromeda = new BigInteger("5379309320171337804361260816606476");
+        
+        BigInteger totalStars = numStarsMilkyWay.add(numStarsAndromeda);
+
+    }
+
+}

core-java/src/main/java/com/baeldung/outofmemoryerror/OutOfMemoryGCLimitExceed.java

@@ -0,0 +1,19 @@
+package com.baeldung.outofmemoryerror;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Random;
+
+public class OutOfMemoryGCLimitExceed {
+    public static void addRandomDataToMap() {
+        Map<Integer, String> dataMap = new HashMap<>();
+        Random r = new Random();
+        while (true) {
+            dataMap.put(r.nextInt(), String.valueOf(r.nextInt()));
+        }
+    }
+
+    public static void main(String[] args) {
+        OutOfMemoryGCLimitExceed.addRandomDataToMap();
+    }
+}

core-java/src/main/java/com/baeldung/typeerasure/ArrayContentPrintUtil.java

@@ -0,0 +1,16 @@
+package com.baeldung.typeerasure;
+
+public class ArrayContentPrintUtil {
+
+   public static <E> void printArray(E[] array) {
+        for (E element : array) {
+            System.out.printf("%s ", element);
+        }
+    }
+    
+    public static <E extends Comparable<E>> void printArray(E[] array) {
+        for (E element : array) {
+            System.out.printf("%s ", element);
+        }
+    }
+}

core-java/src/main/java/com/baeldung/typeerasure/BoundStack.java

@@ -0,0 +1,37 @@
+package com.baeldung.typeerasure;
+
+import java.util.Arrays;
+
+public class BoundStack<E extends Comparable<E>> {
+
+    private E[] stackContent;
+    private int total;
+
+    public BoundStack(int capacity) {
+        this.stackContent = (E[]) new Object[capacity];
+    }
+
+    public void push(E data) {
+        if (total == stackContent.length) {
+            resize(2 * stackContent.length);
+        }
+        stackContent[total++] = data;
+    }
+
+    public E pop() {
+        if (!isEmpty()) {
+            E datum = stackContent[total];
+            stackContent[total--] = null;
+            return datum;
+        }
+        return null;
+    }
+
+    private void resize(int capacity) {
+        Arrays.copyOf(stackContent, capacity);
+    }
+
+    public boolean isEmpty() {
+        return total == 0;
+    }
+}

core-java/src/main/java/com/baeldung/typeerasure/IntegerStack.java

@@ -0,0 +1,13 @@
+package com.baeldung.typeerasure;
+
+public class IntegerStack extends Stack<Integer> {
+
+    public IntegerStack(int capacity) {
+        super(capacity);
+    }
+
+    public void push(Integer value) {
+        System.out.println("Pushing into my integerStack");
+        super.push(value);
+    }
+}

core-java/src/main/java/com/baeldung/typeerasure/Stack.java

@@ -0,0 +1,39 @@
+package com.baeldung.typeerasure;
+
+import java.util.Arrays;
+
+public class Stack<E> {
+
+    private E[] stackContent;
+    private int total;
+
+    public Stack(int capacity) {
+        this.stackContent = (E[]) new Object[capacity];
+    }
+
+    public void push(E data) {
+        System.out.println("In base stack push#");
+        if (total == stackContent.length) {
+            resize(2 * stackContent.length);
+        }
+        stackContent[total++] = data;
+    }
+
+    public E pop() {
+        if (!isEmpty()) {
+            E datum = stackContent[total];
+            stackContent[total--] = null;
+            return datum;
+        }
+        return null;
+    }
+
+    private void resize(int capacity) {
+        Arrays.copyOf(stackContent, capacity);
+    }
+
+    public boolean isEmpty() {
+        return total == 0;
+    }
+
+}

core-java/src/test/java/com/baeldung/concurrent/semaphores/SemaphoresManualTest.java

@@ -0,0 +1,114 @@
+package com.baeldung.concurrent.semaphores;
+
+import org.junit.Test;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class SemaphoresManualTest {
+
+    // ========= login queue ======
+
+    @Test
+    public void givenLoginQueue_whenReachLimit_thenBlocked() {
+        final int slots = 10;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final LoginQueueUsingSemaphore loginQueue = new LoginQueueUsingSemaphore(slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(loginQueue::tryLogin));
+        executorService.shutdown();
+
+        assertEquals(0, loginQueue.availableSlots());
+        assertFalse(loginQueue.tryLogin());
+    }
+
+    @Test
+    public void givenLoginQueue_whenLogout_thenSlotsAvailable() {
+        final int slots = 10;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final LoginQueueUsingSemaphore loginQueue = new LoginQueueUsingSemaphore(slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(loginQueue::tryLogin));
+        executorService.shutdown();
+
+        assertEquals(0, loginQueue.availableSlots());
+        loginQueue.logout();
+        assertTrue(loginQueue.availableSlots() > 0);
+        assertTrue(loginQueue.tryLogin());
+    }
+
+    // ========= delay queue =======
+
+    @Test
+    public void givenDelayQueue_whenReachLimit_thenBlocked() {
+        final int slots = 50;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final DelayQueueUsingTimedSemaphore delayQueue = new DelayQueueUsingTimedSemaphore(1, slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(delayQueue::tryAdd));
+        executorService.shutdown();
+
+        assertEquals(0, delayQueue.availableSlots());
+        assertFalse(delayQueue.tryAdd());
+    }
+
+    @Test
+    public void givenDelayQueue_whenTimePass_thenSlotsAvailable() throws InterruptedException {
+        final int slots = 50;
+        final ExecutorService executorService = Executors.newFixedThreadPool(slots);
+        final DelayQueueUsingTimedSemaphore delayQueue = new DelayQueueUsingTimedSemaphore(1, slots);
+        IntStream.range(0, slots)
+          .forEach(user -> executorService.execute(delayQueue::tryAdd));
+        executorService.shutdown();
+
+        assertEquals(0, delayQueue.availableSlots());
+        Thread.sleep(1000);
+        assertTrue(delayQueue.availableSlots() > 0);
+        assertTrue(delayQueue.tryAdd());
+    }
+
+    // ========== mutex ========
+
+    @Test
+    public void whenMutexAndMultipleThreads_thenBlocked() throws InterruptedException {
+        final int count = 5;
+        final ExecutorService executorService = Executors.newFixedThreadPool(count);
+        final CounterUsingMutex counter = new CounterUsingMutex();
+        IntStream.range(0, count)
+          .forEach(user -> executorService.execute(() -> {
+              try {
+                  counter.increase();
+              } catch (final InterruptedException e) {
+                  e.printStackTrace();
+              }
+          }));
+        executorService.shutdown();
+
+        assertTrue(counter.hasQueuedThreads());
+    }
+
+    @Test
+    public void givenMutexAndMultipleThreads_ThenDelay_thenCorrectCount() throws InterruptedException {
+        final int count = 5;
+        final ExecutorService executorService = Executors.newFixedThreadPool(count);
+        final CounterUsingMutex counter = new CounterUsingMutex();
+        IntStream.range(0, count)
+          .forEach(user -> executorService.execute(() -> {
+              try {
+                  counter.increase();
+              } catch (final InterruptedException e) {
+                  e.printStackTrace();
+              }
+          }));
+        executorService.shutdown();
+        assertTrue(counter.hasQueuedThreads());
+        Thread.sleep(5000);
+        assertFalse(counter.hasQueuedThreads());
+        assertEquals(count, counter.getCount());
+    }
+}

core-java/src/test/java/com/baeldung/map/iteration/MapIterationTest.java

@@ -1,69 +0,0 @@
-package com.baeldung.map.iteration;
-
-import static org.junit.Assert.assertTrue;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-import org.junit.BeforeClass;
-import org.junit.Test;
-
-public class MapIterationTest {
-
-    public static Map<String, Integer> testMap = new HashMap<String, Integer>();
-    public static String testString1 = "One:1";
-    public static String testString2 = "Two:2";
-    public static String testString3 = "Three:3";
-
-    @BeforeClass
-    public static void createTestData() {
-        testMap.put("One", 1);
-        testMap.put("Three", 3);
-        testMap.put("Two", 2);
-    }
-
-    @Test
-    public void givenMap_whenIterateUsingEntrySetReturnsAllEntries_thenCorrect() {
-        MapIteration mapIteration = new MapIteration();
-        List<String> list = mapIteration.iterateUsingEntrySet(testMap);
-        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
-    }
-
-    @Test
-    public void givenMap_whenIterateUsingLambdaReturnsAllEntries_thenCorrect() {
-        MapIteration mapIteration = new MapIteration();
-        List<String> list = mapIteration.iterateUsingLambda(testMap);
-        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
-    }
-
-    @Test
-    public void givenMap_whenIterateUsingIteratorAndEntryReturnsAllEntries_thenCorrect() {
-        MapIteration mapIteration = new MapIteration();
-        List<String> list = mapIteration.iterateUsingIteratorAndEntry(testMap);
-        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
-    }
-
-    @Test
-    public void givenMap_whenIterateUsingKeySetAndForeachReturnsAllEntries_thenCorrect() {
-        MapIteration mapIteration = new MapIteration();
-        List<String> list = mapIteration.iterateUsingKeySetAndForeach(testMap);
-        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
-    }
-
-    @Test
-    public void givenMap_whenIterateUsingStreamAPIReturnsAllEntries_thenCorrect() {
-        MapIteration mapIteration = new MapIteration();
-        List<String> list = mapIteration.iterateUsingStreamAPI(testMap);
-        assertTrue((list.contains(testString1)) && (list.contains(testString2)) && (list.contains(testString3)));
-    }
-
-    @Test
-    public void givenMap_whenIterateUsingKeysReturnsAllKeys_thenCorrect() {
-        MapIteration mapIteration = new MapIteration();
-        ArrayList<String> list = mapIteration.iterateKeys(testMap);
-        assertTrue((list.contains("One")) && (list.contains("Two")) && (list.contains("Three")));
-    }
-
-}

core-java/src/test/java/com/baeldung/maths/BigDecimalImplTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.maths;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BigDecimalImplTest {
+
+    @Test
+    public void givenBigDecimalNumbers_whenAddedTogether_thenGetExpectedResult() {
+        BigDecimal serviceTax = new BigDecimal("56.0084578639");
+        serviceTax = serviceTax.setScale(2, RoundingMode.CEILING);
+
+        BigDecimal entertainmentTax = new BigDecimal("23.00689");
+        entertainmentTax = entertainmentTax.setScale(2, RoundingMode.FLOOR);
+
+        BigDecimal totalTax = serviceTax.add(entertainmentTax);
+        BigDecimal result = BigDecimal.valueOf(79.01);
+
+        Assert.assertEquals(result, totalTax);
+
+    }
+}

core-java/src/test/java/com/baeldung/maths/BigIntegerImplTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.maths;
+
+import java.math.BigInteger;
+
+import org.junit.Assert;
+
+import org.junit.Test;
+
+public class BigIntegerImplTest {
+
+    @Test
+    public void givenBigIntegerNumbers_whenAddedTogether_thenGetExpectedResult() {
+        BigInteger numStarsMilkyWay = new BigInteger("8731409320171337804361260816606476");
+        BigInteger numStarsAndromeda = new BigInteger("5379309320171337804361260816606476");
+
+        BigInteger totalStars = numStarsMilkyWay.add(numStarsAndromeda);
+        BigInteger result = new BigInteger("14110718640342675608722521633212952");
+
+        Assert.assertEquals(result, totalStars);
+    }
+
+}

core-java/src/test/java/com/baeldung/typeerasure/TypeErasureUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.typeerasure;
+
+import org.junit.Test;
+
+public class TypeErasureUnitTest {
+
+    @Test(expected = ClassCastException.class)
+    public void givenIntegerStack_whenStringPushedAndAssignPoppedValueToInteger_shouldFail() {
+        IntegerStack integerStack = new IntegerStack(5);
+        Stack stack = integerStack;
+        stack.push("Hello");
+        Integer data = integerStack.pop();
+    }
+
+    @Test
+    public void givenAnyArray_whenInvokedPrintArray_shouldSucceed() {
+        Integer[] scores = new Integer[] { 100, 200, 10, 99, 20 };
+        ArrayContentPrintUtil.printArray(scores);
+    }
+
+}

guest/memory-leaks/pom.xml

@@ -0,0 +1,39 @@
+<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>memory-leaks</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+
+	<dependencies>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.12</version>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<resources>
+			<resource>
+				<directory>src/main/resources/</directory>
+				<excludes>
+					<exclude>**/*.java</exclude>
+				</excludes>
+			</resource>
+			<resource>
+				<directory>src/test/resources/</directory>
+			</resource>
+		</resources>
+		<plugins>
+			<plugin>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<version>3.5</version>
+				<configuration>
+					<source>1.8</source>
+					<target>1.8</target>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+</project>

guest/memory-leaks/src/test/java/com/baeldung/Key.java

@@ -0,0 +1,11 @@
+package com.baeldung;
+
+public class Key {
+
+    public static String key;
+
+    public Key(String key) {
+        Key.key = key;
+    }
+
+}

guest/memory-leaks/src/test/java/com/baeldung/MemoryLeaksTest.java

@@ -0,0 +1,98 @@
+//package com.baeldung;
+//
+//import java.io.BufferedReader;
+//import java.io.File;
+//import java.io.IOException;
+//import java.io.InputStream;
+//import java.io.InputStreamReader;
+//import java.net.URISyntaxException;
+//import java.net.URL;
+//import java.net.URLConnection;
+//import java.nio.charset.StandardCharsets;
+//import java.nio.file.Files;
+//import java.nio.file.Paths;
+//import java.nio.file.StandardOpenOption;
+//import java.util.ArrayList;
+//import java.util.Map;
+//import java.util.Random;
+//import java.util.Scanner;
+//
+//import org.junit.FixMethodOrder;
+//import org.junit.Test;
+//import org.junit.runner.RunWith;
+//import org.junit.runners.JUnit4;
+//import org.junit.runners.MethodSorters;
+//
+//@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+//@RunWith(JUnit4.class)
+//public class MemoryLeaksTest {
+//    private Random random = new Random();
+//    public static final ArrayList<Double> list = new ArrayList<Double>(1000000);
+//
+//    @Test
+//    public void givenStaticField_whenLotsOfOperations_thenMemoryLeak() throws InterruptedException {
+//        for (int i = 0; i < 1000000; i++) {
+//            list.add(random.nextDouble());
+//        }
+//        System.gc();
+//        Thread.sleep(10000); //to allow GC do its job
+//    }
+//
+//    
+//    @Test
+//    public void givenNormalField_whenLotsOfOperations_thenGCWorksFine() throws InterruptedException {
+//        addElementsToTheList();
+//        System.gc();
+//        Thread.sleep(10000); //to allow GC do its job
+//    }
+//    
+//    private void addElementsToTheList(){
+//        ArrayList<Double> list = new ArrayList<Double>(1000000);
+//        for (int i = 0; i < 1000000; i++) {
+//            list.add(random.nextDouble());
+//        }
+//    }
+//
+//    @SuppressWarnings({ "resource" })
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenLengthString_whenIntern_thenOutOfMemory() throws IOException, InterruptedException {
+//        Thread.sleep(15000);
+//        String str = new Scanner(new File("src/test/resources/large.txt"), "UTF-8").useDelimiter("\\A")
+//            .next();
+//        System.gc();
+//        str.intern();
+//        Thread.sleep(10000);
+//    }
+//
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenURL_whenUnclosedStream_thenOutOfMemory() throws IOException, URISyntaxException {
+//        String str = "";
+//        URLConnection conn = new URL("http:norvig.com/big.txt").openConnection();
+//        BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8));
+//        while (br.readLine() != null) {
+//            str += br.readLine();
+//        }
+//        Files.write(Paths.get("src/main/resources/"), str.getBytes(), StandardOpenOption.CREATE);
+//    }
+//
+//    @SuppressWarnings("unused")
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenConnection_whenUnclosed_thenOutOfMemory() throws IOException, URISyntaxException {
+//        URL url = new URL("ftp:speedtest.tele2.net");
+//        URLConnection urlc = url.openConnection();
+//        InputStream is = urlc.getInputStream();
+//        String str = "";
+//        while (true) {
+//            str += is.toString()
+//                .intern();
+//        }
+//    }
+//
+//    @Test(expected = OutOfMemoryError.class)
+//    public void givenMap_whenNoEqualsNoHashCodeMethods_thenOutOfMemory() throws IOException, URISyntaxException {
+//        Map<Object, Object> map = System.getProperties();
+//        while (true) {
+//            map.put(new Key("key"), "value");
+//        }
+//    }
+//}

jee7/pom.xml

@@ -31,6 +31,7 @@
 		<arquillian-glassfish.version>1.0.0.Final</arquillian-glassfish.version>
 
 		<maven-war-plugin.version>2.6</maven-war-plugin.version>
+		<org.springframework.security.version>4.2.3.RELEASE</org.springframework.security.version>
 	</properties>
 
 	<prerequisites>
@@ -136,6 +137,34 @@
 			<artifactId>standard</artifactId>
 			<version>1.1.2</version>
 		</dependency>
+
+		<dependency>
+			<groupId>javax.mvc</groupId>
+			<artifactId>javax.mvc-api</artifactId>
+			<version>20160715</version>
+		</dependency>
+		<dependency>
+			<groupId>org.glassfish.ozark</groupId>
+			<artifactId>ozark</artifactId>
+			<version>20160715</version>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.security</groupId>
+			<artifactId>spring-security-web</artifactId>
+			<version>${org.springframework.security.version}</version>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.security</groupId>
+			<artifactId>spring-security-config</artifactId>
+			<version>${org.springframework.security.version}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.security</groupId>
+			<artifactId>spring-security-taglibs</artifactId>
+			<version>${org.springframework.security.version}</version>
+		</dependency>
 	</dependencies>
 
 	<build>
@@ -378,4 +407,18 @@
 			</properties>
 		</profile>
 	</profiles>
+
+	<repositories>
+		<repository>
+			<id>bintray-mvc-spec-maven</id>
+			<name>bintray</name>
+			<url>http://dl.bintray.com/mvc-spec/maven</url>
+			<releases>
+				<enabled>true</enabled>
+			</releases>
+			<snapshots>
+				<enabled>false</enabled>
+			</snapshots>
+		</repository>
+	</repositories>
 </project>

jee7/src/main/java/com/baeldung/springSecurity/ApplicationConfig.java

@@ -0,0 +1,13 @@
+package com.baeldung.springSecurity;
+
+import javax.ws.rs.ApplicationPath;
+import javax.ws.rs.core.Application;
+
+/**
+ * Application class required by JAX-RS. If you don't want to have any
+ * prefix in the URL, you can set the application path to "/".
+ */
+@ApplicationPath("/")
+public class ApplicationConfig extends Application {
+
+}

jee7/src/main/java/com/baeldung/springSecurity/SecurityWebApplicationInitializer.java

@@ -0,0 +1,10 @@
+package com.baeldung.springSecurity;
+
+import org.springframework.security.web.context.AbstractSecurityWebApplicationInitializer;
+
+public class SecurityWebApplicationInitializer extends AbstractSecurityWebApplicationInitializer {
+
+    public SecurityWebApplicationInitializer() {
+        super(SpringSecurityConfig.class);
+    }
+}

jee7/src/main/java/com/baeldung/springSecurity/SpringSecurityConfig.java

@@ -0,0 +1,46 @@
+package com.baeldung.springSecurity;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+
+@Configuration
+@EnableWebSecurity
+public class SpringSecurityConfig extends WebSecurityConfigurerAdapter {
+    @Override
+    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
+        auth
+          .inMemoryAuthentication()
+          .withUser("user1")
+          .password("user1Pass")
+          .roles("USER")
+          .and()
+          .withUser("admin")
+          .password("adminPass")
+          .roles("ADMIN");
+    }
+
+    @Override
+    protected void configure(HttpSecurity http) throws Exception {
+        http
+          .csrf()
+          .disable()
+          .authorizeRequests()
+          .antMatchers("/auth/login*")
+          .anonymous()
+          .antMatchers("/home/admin*")
+          .hasRole("ADMIN")
+          .anyRequest()
+          .authenticated()
+          .and()
+          .formLogin()
+          .loginPage("/auth/login")
+          .defaultSuccessUrl("/home", true)
+          .failureUrl("/auth/login?error=true")
+          .and()
+          .logout()
+          .logoutSuccessUrl("/auth/login");
+    }
+}

jee7/src/main/java/com/baeldung/springSecurity/controller/HomeController.java

@@ -0,0 +1,28 @@
+package com.baeldung.springSecurity.controller;
+
+import javax.mvc.annotation.Controller;
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+
+@Path("/home")
+@Controller
+public class HomeController {
+
+    @GET
+    public String home() {
+        return "home.jsp";
+    }
+
+    @GET
+    @Path("/user")
+    public String admin() {
+        return "user.jsp";
+    }
+
+    @GET
+    @Path("/admin")
+    public String user() {
+        return "admin.jsp";
+    }
+
+}

jee7/src/main/java/com/baeldung/springSecurity/controller/LoginController.java

@@ -0,0 +1,15 @@
+package com.baeldung.springSecurity.controller;
+
+import javax.mvc.annotation.Controller;
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+
+@Path("/auth/login")
+@Controller
+public class LoginController {
+
+    @GET
+    public String login() {
+        return "login.jsp";
+    }
+}

jee7/src/main/webapp/WEB-INF/views/admin.jsp

@@ -0,0 +1,12 @@
+<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
+<%@ taglib prefix="security" uri="http://www.springframework.org/security/tags" %>
+<html>
+<head></head>
+
+<body>
+    <h1>Welcome to the ADMIN page</h1>
+
+    <a href="<c:url value="/logout" />">Logout</a>
+
+</body>
+</html>

jee7/src/main/webapp/WEB-INF/views/home.jsp

@@ -0,0 +1,26 @@
+<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
+<%@ taglib prefix="security" uri="http://www.springframework.org/security/tags" %>
+<html>
+<head></head>
+
+<body>
+    <h1>This is the body of the sample view</h1>
+
+    <security:authorize access="hasRole('USER')">
+        This text is only visible to a user
+        <br/> <br/>
+        <a href="<c:url value="/home/user" />">Restricted Admin Page</a>
+        <br/> <br/>
+    </security:authorize>
+	
+    <security:authorize access="hasRole('ADMIN')">
+        This text is only visible to an admin
+        <br/>
+        <a href="<c:url value="/home/admin" />">Admin Page</a>
+        <br/>
+    </security:authorize>
+
+    <a href="<c:url value="/logout" />">Logout</a>
+
+</body>
+</html>

jee7/src/main/webapp/WEB-INF/views/login.jsp

@@ -0,0 +1,26 @@
+<html>
+<head></head>
+
+<body>
+<h1>Login</h1>
+
+<form name='f' action="/auth/login" method='POST'>
+
+    <table>
+        <tr>
+            <td>User:</td>
+            <td><input type='text' name='username' value=''></td>
+        </tr>
+        <tr>
+            <td>Password:</td>
+            <td><input type='password' name='password'/></td>
+        </tr>
+        <tr>
+            <td><input name="submit" type="submit" value="submit"/></td>
+        </tr>
+    </table>
+
+</form>
+
+</body>
+</html>

jee7/src/main/webapp/WEB-INF/views/user.jsp

@@ -0,0 +1,12 @@
+<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
+<%@ taglib prefix="security" uri="http://www.springframework.org/security/tags" %>
+<html>
+<head></head>
+
+<body>
+    <h1>Welcome to the Restricted Admin page</h1>
+
+    <a href="<c:url value="/logout" />">Logout</a>
+
+</body>
+</html>

kotlin-mockito/README.md

@@ -1,8 +0,0 @@
-## Relevant articles:
-
-- [Introduction to the Kotlin Language](http://www.baeldung.com/kotlin)
-- [A guide to the “when{}” block in Kotlin](http://www.baeldung.com/kotlin-when)
-- [Comprehensive Guide to Null Safety in Kotlin](http://www.baeldung.com/kotlin-null-safety)
-- [Kotlin Java Interoperability](http://www.baeldung.com/kotlin-java-interoperability)
-- [Difference Between “==” and “===” in Kotlin](http://www.baeldung.com/kotlin-equality-operators)
-- [Generics in Kotlin](http://www.baeldung.com/kotlin-generics)

kotlin-mockito/pom.xml

@@ -1,121 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
-
-    <artifactId>kotlin-mockito</artifactId>
-    <version>1.0-SNAPSHOT</version>
-
-    <parent>
-        <groupId>com.baeldung</groupId>
-        <artifactId>parent-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-    </parent>
-
-    <dependencies>
-        <dependency>
-            <groupId>org.jetbrains.kotlin</groupId>
-            <artifactId>kotlin-stdlib</artifactId>
-            <version>${kotlin.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.mockito</groupId>
-            <artifactId>mockito-core</artifactId>
-            <version>${mockito.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>${junit.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>com.nhaarman</groupId>
-            <artifactId>mockito-kotlin</artifactId>
-            <version>${mockito-kotlin.version}</version>
-            <scope>test</scope>
-        </dependency>
-    </dependencies>
-
-    <build>
-        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
-        <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
-
-        <plugins>
-            <plugin>
-                <artifactId>kotlin-maven-plugin</artifactId>
-                <groupId>org.jetbrains.kotlin</groupId>
-                <version>${kotlin.version}</version>
-                <executions>
-                    <execution>
-                        <id>compile</id>
-                        <goals>
-                            <goal>compile</goal>
-                        </goals>
-                        <configuration>
-                            <sourceDirs>
-                                <sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
-                                <sourceDir>${project.basedir}/src/main/java</sourceDir>
-                            </sourceDirs>
-                        </configuration>
-                    </execution>
-                    <execution>
-                        <id>test-compile</id>
-                        <goals>
-                            <goal>test-compile</goal>
-                        </goals>
-                        <configuration>
-                            <sourceDirs>
-                                <sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
-                                <sourceDir>${project.basedir}/src/test/java</sourceDir>
-                            </sourceDirs>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler.version}</version>
-                <executions>
-                    <!-- Replacing default-compile as it is treated specially 
-                        by maven -->
-                    <execution>
-                        <id>default-compile</id>
-                        <phase>none</phase>
-                    </execution>
-                    <!-- Replacing default-testCompile as it is treated specially 
-                        by maven -->
-                    <execution>
-                        <id>default-testCompile</id>
-                        <phase>none</phase>
-                    </execution>
-                    <execution>
-                        <id>java-compile</id>
-                        <phase>compile</phase>
-                        <goals>
-                            <goal>compile</goal>
-                        </goals>
-                    </execution>
-                    <execution>
-                        <id>java-test-compile</id>
-                        <phase>test-compile</phase>
-                        <goals>
-                            <goal>testCompile</goal>
-                        </goals>
-                    </execution>
-                </executions>
-            </plugin>
-        </plugins>
-    </build>
-
-    <properties>
-        <mockito.version>2.8.9</mockito.version>
-        <junit.version>4.12</junit.version>
-        <kotlin.version>1.1.2-4</kotlin.version>
-        <mockito-kotlin.version>1.5.0</mockito-kotlin.version>
-        <maven-compiler.version>3.5.1</maven-compiler.version>
-    </properties>
-
-</project>

kotlin-mockito/src/main/java/com/baeldung/java/ArrayExample.java

@@ -1,24 +0,0 @@
-package com.baeldung.java;
-
-import java.io.File;
-import java.io.FileReader;
-import java.io.IOException;
-
-public class ArrayExample {
-
-    public int sumValues(int[] nums) {
-        int res = 0;
-
-        for (int x:nums) {
-            res += x;
-        }
-
-        return res;
-    }
-
-    public void writeList() throws IOException {
-        File file = new File("E://file.txt");
-        FileReader fr = new FileReader(file);
-        fr.close();
-    }
-}

kotlin-mockito/src/main/java/com/baeldung/java/Customer.java

@@ -1,24 +0,0 @@
-package com.baeldung.java;
-
-public class Customer {
-
-    private String firstName;
-    private String lastName;
-
-    public String getFirstName() {
-        return firstName;
-    }
-
-    public void setFirstName(String firstName) {
-        this.firstName = firstName;
-    }
-
-    public String getLastName() {
-        return lastName;
-    }
-
-    public void setLastName(String lastName) {
-        this.lastName = lastName;
-    }
-
-}

kotlin-mockito/src/main/java/com/baeldung/java/StringUtils.java

@@ -1,7 +0,0 @@
-package com.baeldung.java;
-
-public class StringUtils {
-    public static String toUpperCase(String name) {
-        return name.toUpperCase();
-    }
-}

kotlin-mockito/src/test/java/com/baeldung/kotlin/JavaCallToKotlinUnitTest.java

@@ -1,17 +0,0 @@
-package com.baeldung.kotlin;
-
-import org.junit.Test;
-
-import static org.junit.Assert.assertEquals;
-
-public class JavaCallToKotlinUnitTest {
-    @Test
-    public void givenKotlinClass_whenCallFromJava_shouldProduceResults() {
-        //when
-        int res = new MathematicsOperations().addTwoNumbers(2, 4);
-
-        //then
-        assertEquals(6, res);
-
-    }
-}

kotlin/pom.xml

@@ -3,7 +3,6 @@
          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>kotlin</artifactId>
     <version>1.0-SNAPSHOT</version>
 
@@ -13,6 +12,13 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <repositories>
+        <repository>
+            <id>central</id>
+            <url>http://jcenter.bintray.com</url>
+        </repository>
+    </repositories>
+
     <dependencies>
         <dependency>
             <groupId>org.jetbrains.kotlin</groupId>
@@ -31,9 +37,19 @@
             <version>${kotlin-reflect.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlinx</groupId>
+            <artifactId>kotlinx-coroutines-core</artifactId>
+            <version>${kotlinx.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.nhaarman</groupId>
+            <artifactId>mockito-kotlin</artifactId>
+            <version>${mockito-kotlin.version}</version>
+            <scope>test</scope>
+        </dependency>        
     </dependencies>
 
-
     <build>
         <plugins>
             <plugin>
@@ -104,10 +120,12 @@
     </build>
 
     <properties>
-        <kotlin-maven-plugin.version>1.1.1</kotlin-maven-plugin.version>
+        <kotlin-maven-plugin.version>1.1.2</kotlin-maven-plugin.version>
-        <kotlin-test-junit.version>1.1.1</kotlin-test-junit.version>
+        <kotlin-test-junit.version>1.1.2</kotlin-test-junit.version>
-        <kotlin-stdlib.version>1.1.1</kotlin-stdlib.version>
+        <kotlin-stdlib.version>1.1.2</kotlin-stdlib.version>
-        <kotlin-reflect.version>1.1.1</kotlin-reflect.version>
+        <kotlin-reflect.version>1.1.2</kotlin-reflect.version>
+        <kotlinx.version>0.15</kotlinx.version>
+        <mockito-kotlin.version>1.5.0</mockito-kotlin.version>
     </properties>
 
 </project>

kotlin/src/test/kotlin/com/baeldung/kotlin/CoroutinesTest.kt

@@ -0,0 +1,179 @@
+package com.baeldung.kotlin
+
+import kotlinx.coroutines.experimental.*
+import org.junit.Test
+import java.util.concurrent.atomic.AtomicInteger
+import kotlin.coroutines.experimental.buildSequence
+import kotlin.system.measureTimeMillis
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+
+class CoroutinesTest {
+
+    @Test
+    fun givenBuildSequence_whenTakeNElements_thenShouldReturnItInALazyWay() {
+        //given
+        val fibonacciSeq = buildSequence {
+            var a = 0
+            var b = 1
+
+            yield(1)
+
+            while (true) {
+                yield(a + b)
+
+                val tmp = a + b
+                a = b
+                b = tmp
+            }
+        }
+
+        //when
+        val res = fibonacciSeq.take(5).toList()
+
+        //then
+        assertEquals(res, listOf(1, 1, 2, 3, 5))
+    }
+
+    @Test
+    fun givenLazySeq_whenTakeNElements_thenShouldReturnAllElements() {
+        //given
+        val lazySeq = buildSequence {
+            print("START ")
+            for (i in 1..5) {
+                yield(i)
+                print("STEP ")
+            }
+            print("END")
+        }
+        //when
+        val res = lazySeq.take(10).toList()
+
+        //then
+        assertEquals(res, listOf(1, 2, 3, 4, 5))
+    }
+
+    @Test
+    fun givenAsyncCoroutine_whenStartIt_thenShouldExecuteItInTheAsyncWay() {
+        //given
+        val res = mutableListOf<String>()
+
+        //when
+        runBlocking<Unit> {
+            val promise = launch(CommonPool) { expensiveComputation(res) }
+            res.add("Hello,")
+            promise.join()
+        }
+
+        //then
+        assertEquals(res, listOf("Hello,", "word!"))
+    }
+
+
+    suspend fun expensiveComputation(res: MutableList<String>) {
+        delay(1000L)
+        res.add("word!")
+    }
+
+    @Test
+    fun givenHugeAmountOfCoroutines_whenStartIt_thenShouldExecuteItWithoutOutOfMemory() {
+        runBlocking<Unit> {
+            //given
+            val counter = AtomicInteger(0)
+            val numberOfCoroutines = 100_000
+
+            //when
+            val jobs = List(numberOfCoroutines) {
+                launch(CommonPool) {
+                    delay(1L)
+                    counter.incrementAndGet()
+                }
+            }
+            jobs.forEach { it.join() }
+
+            //then
+            assertEquals(counter.get(), numberOfCoroutines)
+        }
+    }
+
+    @Test
+    fun givenCancellableJob_whenRequestForCancel_thenShouldQuit() {
+        runBlocking<Unit> {
+            //given
+            val job = launch(CommonPool) {
+                while (isActive) {
+                    println("is working")
+                }
+            }
+
+            delay(1300L)
+
+            //when
+            job.cancel()
+
+            //then cancel successfully
+
+        }
+    }
+
+    @Test(expected = CancellationException::class)
+    fun givenAsyncAction_whenDeclareTimeout_thenShouldFinishWhenTimedOut() {
+        runBlocking<Unit> {
+            withTimeout(1300L) {
+                repeat(1000) { i ->
+                    println("Some expensive computation $i ...")
+                    delay(500L)
+                }
+            }
+        }
+    }
+
+    @Test
+    fun givenHaveTwoExpensiveAction_whenExecuteThemAsync_thenTheyShouldRunConcurrently() {
+        runBlocking<Unit> {
+            val delay = 1000L
+            val time = measureTimeMillis {
+                //given
+                val one = async(CommonPool) { someExpensiveComputation(delay) }
+                val two = async(CommonPool) { someExpensiveComputation(delay) }
+
+                //when
+                runBlocking {
+                    one.await()
+                    two.await()
+                }
+            }
+
+            //then
+            assertTrue(time < delay * 2)
+        }
+    }
+
+    @Test
+    fun givenTwoExpensiveAction_whenExecuteThemLazy_thenTheyShouldNotConcurrently() {
+        runBlocking<Unit> {
+            val delay = 1000L
+            val time = measureTimeMillis {
+                //given
+                val one = async(CommonPool, CoroutineStart.LAZY) { someExpensiveComputation(delay) }
+                val two = async(CommonPool, CoroutineStart.LAZY) { someExpensiveComputation(delay) }
+
+                //when
+                runBlocking {
+                    one.await()
+                    two.await()
+                }
+            }
+
+            //then
+            assertTrue(time > delay * 2)
+        }
+    }
+
+    suspend fun someExpensiveComputation(delayInMilliseconds: Long) {
+        delay(delayInMilliseconds)
+    }
+
+
+}

libraries/README.md

@@ -17,6 +17,7 @@
 - [Introduction to HikariCP](http://www.baeldung.com/hikaricp)
 - [Serenity BDD with Spring and JBehave](http://www.baeldung.com/serenity-spring-jbehave)
 - [Locality-Sensitive Hashing in Java Using Java-LSH](http://www.baeldung.com/locality-sensitive-hashing)
+- [Apache Commons Collections OrderedMap](http://www.baeldung.com/apache-commons-ordered-map)
 
 
 The libraries module contains examples related to small libraries that are relatively easy to use and does not require any separate module of its own.

libraries/pom.xml

@@ -70,32 +70,6 @@
                     </execution>
                 </executions>
             </plugin>
-            <plugin>
-                <groupId>org.asciidoctor</groupId>
-                <artifactId>asciidoctor-maven-plugin</artifactId>
-                <version>1.5.5</version>
-                <dependencies>
-                    <dependency>
-                        <groupId>org.asciidoctor</groupId>
-                        <artifactId>asciidoctorj-pdf</artifactId>
-                        <version>1.5.0-alpha.15</version>
-                    </dependency>
-                </dependencies>
-                <executions>
-                    <execution>
-                        <id>output-pdf</id>
-                        <phase>generate-resources</phase>
-                        <goals>
-                            <goal>process-asciidoc</goal>
-                        </goals>
-                    </execution>
-                </executions>
-                <configuration>
-                    <sourceDirectory>src/docs/asciidoc</sourceDirectory>
-                    <outputDirectory>target/docs/asciidoc</outputDirectory>
-                    <backend>pdf</backend>
-                </configuration>
-            </plugin>
         </plugins>
     </build>
 
@@ -116,6 +90,11 @@
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-text</artifactId>
+            <version>${commons-text.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-collections4</artifactId>
@@ -216,12 +195,6 @@
             <artifactId>serenity-core</artifactId>
             <version>${serenity.version}</version>
             <scope>test</scope>
-            <exclusions>
-    	        <exclusion>
-                    <groupId>org.asciidoctor</groupId>
-                    <artifactId>asciidoctor-java-integration</artifactId>
-                </exclusion>
-            </exclusions>
         </dependency>
         <dependency>
             <groupId>net.serenity-bdd</groupId>
@@ -365,16 +338,6 @@
             <artifactId>netty-all</artifactId>
             <version>${netty.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.asciidoctor</groupId>
-            <artifactId>asciidoctorj</artifactId>
-            <version>1.5.4</version>
-        </dependency>
-        <dependency>
-            <groupId>org.asciidoctor</groupId>
-            <artifactId>asciidoctorj-pdf</artifactId>
-            <version>1.5.0-alpha.11</version>
-        </dependency>        
         <!-- OpenNLP -->
         <dependency>
             <groupId>org.apache.opennlp</groupId>
@@ -392,11 +355,23 @@
             <artifactId>java-lsh</artifactId>
             <version>${java-lsh.version}</version>
         </dependency>
+        <dependency>
+            <groupId>au.com.dius</groupId>
+            <artifactId>pact-jvm-consumer-junit_2.11</artifactId>
+            <version>${pact.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-all</artifactId>
+            <version>2.4.10</version>
+        </dependency>
     </dependencies>
     <properties>
         <multiverse.version>0.7.0</multiverse.version>
         <cglib.version>3.2.4</cglib.version>
         <commons-lang.version>3.5</commons-lang.version>
+        <commons-text.version>1.1</commons-text.version>
         <commons-beanutils.version>1.9.3</commons-beanutils.version>
         <jasypt.version>1.9.2</jasypt.version>
         <javatuples.version>1.2</javatuples.version>
@@ -421,6 +396,7 @@
         <commons.collections.version>4.1</commons.collections.version>
         <junit.version>4.12</junit.version>
         <java-lsh.version>0.10</java-lsh.version>
+        <pact.version>3.5.0</pact.version>
     </properties>
 
 </project>

libraries/src/main/java/com/baeldung/commons/beanutils/CourseEntity.java

@@ -0,0 +1,35 @@
+package com.baeldung.commons.beanutils;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class CourseEntity {
+    private String name;
+    private List<String> codes;
+    private Map<String, Student> students = new HashMap<String, Student>();
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<String> getCodes() {
+        return codes;
+    }
+
+    public void setCodes(List<String> codes) {
+        this.codes = codes;
+    }
+    
+    public void setStudent(String id, Student student) {
+        students.put(id, student);
+    }
+
+    public Student getStudent(String enrolledId) {
+        return students.get(enrolledId);
+    }
+}

libraries/src/main/java/com/baeldung/commons/beanutils/CourseService.java

@@ -3,6 +3,7 @@ package com.baeldung.commons.beanutils;
 import java.lang.reflect.InvocationTargetException;
 import java.util.List;
 
+import org.apache.commons.beanutils.BeanUtils;
 import org.apache.commons.beanutils.PropertyUtils;
 
 public class CourseService {
@@ -31,4 +32,9 @@ public class CourseService {
         return (String) PropertyUtils.getNestedProperty(
                  course, "enrolledStudent(" + enrollId + ")." + nestedPropertyName);
     }
+    
+    public static void copyProperties(Course course, CourseEntity courseEntity) 
+        throws IllegalAccessException, InvocationTargetException {
+        BeanUtils.copyProperties(course, courseEntity);
+    }
 }

libraries/src/main/java/com/baeldung/commons/collectionutil/Address.java

@@ -0,0 +1,47 @@
+package com.baeldung.commons.collectionutil;
+
+public class Address {
+
+    private String locality;
+    private String city;
+    private String zip;
+
+    public String getLocality() {
+        return locality;
+    }
+
+    public void setLocality(String locality) {
+        this.locality = locality;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getZip() {
+        return zip;
+    }
+
+    public void setZip(String zip) {
+        this.zip = zip;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Address [locality=").append(locality).append(", city=").append(city).append(", zip=").append(zip).append("]");
+        return builder.toString();
+    }
+
+    public Address(String locality, String city, String zip) {
+        super();
+        this.locality = locality;
+        this.city = city;
+        this.zip = zip;
+    }
+
+}

libraries/src/main/java/com/baeldung/commons/collectionutil/Customer.java

@@ -0,0 +1,118 @@
+package com.baeldung.commons.collectionutil;
+
+public class Customer implements Comparable<Customer> {
+
+    private Integer id;
+    private String name;
+    private Long phone;
+    private String locality;
+    private String city;
+    private String zip;
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Long getPhone() {
+        return phone;
+    }
+
+    public void setPhone(Long phone) {
+        this.phone = phone;
+    }
+
+    public String getLocality() {
+        return locality;
+    }
+
+    public void setLocality(String locality) {
+        this.locality = locality;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getZip() {
+        return zip;
+    }
+
+    public void setZip(String zip) {
+        this.zip = zip;
+    }
+
+    public Customer(Integer id, String name, Long phone, String locality, String city, String zip) {
+        super();
+        this.id = id;
+        this.name = name;
+        this.phone = phone;
+        this.locality = locality;
+        this.city = city;
+        this.zip = zip;
+    }
+
+    public Customer(Integer id, String name, Long phone) {
+        super();
+        this.id = id;
+        this.name = name;
+        this.phone = phone;
+    }
+    
+    public Customer(String name) {
+        super();
+        this.name = name;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Customer other = (Customer) obj;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        return true;
+    }
+
+    public int compareTo(Customer o) {
+        return this.name.compareTo(o.getName());
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Customer [id=").append(id).append(", name=").append(name).append(", phone=").append(phone).append("]");
+        return builder.toString();
+    }
+
+}

libraries/src/test/java/com/baeldung/commons/beanutils/CourseServiceTest.java

@@ -35,4 +35,19 @@ public class CourseServiceTest {
         Assert.assertEquals(studentName, accessedStudentName);
     }
 
+    @Test
+    public void givenCopyProperties_whenCopyCourseToCourseEntity_thenCopyPropertyWithSameName()
+        throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
+        Course course = new Course();
+        course.setName("Computer Science");
+        course.setCodes(Arrays.asList("CS"));
+        course.setEnrolledStudent("ST-1", new Student());
+
+        CourseEntity courseEntity = new CourseEntity();
+
+        CourseService.copyProperties(course, courseEntity);
+        Assert.assertEquals(course.getName(), courseEntity.getName());
+        Assert.assertEquals(course.getCodes(), courseEntity.getCodes());
+        Assert.assertNull(courseEntity.getStudent("ST-1"));
+    }
 }

libraries/src/test/java/com/baeldung/commons/collections/BidiMapUnitTest.java

@@ -0,0 +1,49 @@
+package com.baeldung.commons.collections;
+
+import org.apache.commons.collections4.BidiMap;
+import org.apache.commons.collections4.bidimap.DualHashBidiMap;
+import org.apache.commons.collections4.bidimap.DualLinkedHashBidiMap;
+import org.apache.commons.collections4.bidimap.DualTreeBidiMap;
+import org.apache.commons.collections4.bidimap.TreeBidiMap;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * Created by smatt on 03/07/2017.
+ */
+public class BidiMapUnitTest {
+
+    @Test
+    public void givenKeyValue_whenPut_thenAddEntryToMap() {
+        BidiMap<String, String> map = new DualHashBidiMap<>();
+        map.put("key1", "value1");
+        map.put("key2", "value2");
+        assertEquals(map.size(), 2);
+    }
+
+    @Test
+    public void whenInverseBidiMap_thenInverseKeyValue() {
+        BidiMap<String, String> map = new DualHashBidiMap<>();
+        map.put("key1", "value1");
+        map.put("key2", "value2");
+        BidiMap<String, String> rMap = map.inverseBidiMap();
+        assertTrue(rMap.containsKey("value1") && rMap.containsKey("value2"));
+    }
+
+    @Test
+    public void givenValue_whenRemoveValue_thenRemoveMatchingMapEntry() {
+        BidiMap<String, String> map = new DualHashBidiMap<>();
+        map.put("key1", "value1");
+        map.put("key2", "value2");
+        map.removeValue("value2");
+        assertFalse(map.containsKey("key2"));
+    }
+
+    @Test
+    public void givenValue_whenGetKey_thenMappedKey() {
+        BidiMap<String, String> map = new DualHashBidiMap<>();
+        map.put("key1", "value1");
+        assertEquals(map.getKey("value1"), "key1");
+    }
+}

libraries/src/test/java/com/baeldung/commons/collections/CollectionUtilsGuideTest.java

@@ -0,0 +1,113 @@
+package com.baeldung.commons.collections;
+
+
+import com.baeldung.commons.collectionutil.Address;
+import com.baeldung.commons.collectionutil.Customer;
+import org.apache.commons.collections4.Closure;
+import org.apache.commons.collections4.CollectionUtils;
+import org.apache.commons.collections4.Predicate;
+import org.apache.commons.collections4.Transformer;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class CollectionUtilsGuideTest {
+
+
+    Customer customer1 = new Customer(1, "Daniel", 123456l, "locality1", "city1", "1234");
+    Customer customer4 = new Customer(4, "Bob", 456789l, "locality4", "city4", "4567");
+    List<Customer> list1, list2, list3, linkedList1;
+
+    @Before
+    public void setup() {
+        Customer customer2 = new Customer(2, "Fredrik", 234567l, "locality2", "city2", "2345");
+        Customer customer3 = new Customer(3, "Kyle", 345678l, "locality3", "city3", "3456");
+        Customer customer5 = new Customer(5, "Cat", 567890l, "locality5", "city5", "5678");
+        Customer customer6 = new Customer(6, "John", 678901l, "locality6", "city6", "6789");
+
+        list1 = Arrays.asList(customer1, customer2, customer3);
+        list2 = Arrays.asList(customer4, customer5, customer6);
+        list3 = Arrays.asList(customer1, customer2);
+
+        linkedList1 = new LinkedList<>(list1);
+    }
+    
+    @Test
+    public void givenList_whenAddIgnoreNull_thenNoNullAdded() {
+        CollectionUtils.addIgnoreNull(list1, null);
+        assertFalse(list1.contains(null));
+    }
+    
+    @Test
+    public void givenTwoSortedLists_whenCollated_thenSorted() {
+        List<Customer> sortedList = CollectionUtils.collate(list1, list2);
+
+        assertEquals(6, sortedList.size());
+        assertTrue(sortedList.get(0).getName().equals("Bob"));
+        assertTrue(sortedList.get(2).getName().equals("Daniel"));
+    }
+    
+    @Test
+    public void givenListOfCustomers_whenTransformed_thenListOfAddress() {
+        Collection<Address> addressCol = CollectionUtils.collect(list1, customer -> {
+            return new Address(customer.getLocality(), customer.getCity(), customer.getZip());
+        });
+        
+        List<Address> addressList = new ArrayList<>(addressCol);
+        assertTrue(addressList.size() == 3);
+        assertTrue(addressList.get(0).getLocality().equals("locality1"));
+    }
+    
+    @Test
+    public void givenCustomerList_whenFiltered_thenCorrectSize() {
+        
+        boolean isModified = CollectionUtils.filter(linkedList1, customer -> Arrays.asList("Daniel","Kyle").contains(customer.getName()));
+        
+        //filterInverse does the opposite. It removes the element from the list if the Predicate returns true
+        //select and selectRejected work the same way except that they do not remove elements from the given collection and return a new collection 
+        
+        assertTrue(isModified && linkedList1.size() == 2);
+    }
+    
+    @Test
+    public void givenNonEmptyList_whenCheckedIsNotEmpty_thenTrue() {
+        List<Customer> emptyList = new ArrayList<>();
+        List<Customer> nullList = null;
+        
+        //Very handy at times where we want to check if a collection is not null and not empty too.
+        //isNotEmpty does the opposite. Handy because using ! operator on isEmpty makes it missable while reading
+        assertTrue(CollectionUtils.isNotEmpty(list1));
+        assertTrue(CollectionUtils.isEmpty(nullList));
+        assertTrue(CollectionUtils.isEmpty(emptyList));
+    }
+    
+    @Test
+    public void givenCustomerListAndASubcollection_whenChecked_thenTrue() {
+        assertTrue(CollectionUtils.isSubCollection(list3, list1));
+    }
+    
+    @Test
+    public void givenTwoLists_whenIntersected_thenCheckSize() {
+        Collection<Customer> intersection = CollectionUtils.intersection(list1, list3);
+        assertTrue(intersection.size() == 2);
+    }
+    
+    @Test
+    public void givenTwoLists_whenSubtracted_thenCheckElementNotPresentInA() {
+        Collection<Customer> result = CollectionUtils.subtract(list1, list3);
+        assertFalse(result.contains(customer1));
+    }
+    
+    @Test
+    public void givenTwoLists_whenUnioned_thenCheckElementPresentInResult() {
+        Collection<Customer> union = CollectionUtils.union(list1, list2);
+        assertTrue(union.contains(customer1));
+        assertTrue(union.contains(customer4));
+    }
+    
+}

libraries/src/test/java/com/baeldung/commons/collections/orderedmap/OrderedMapUnitTest.java

@@ -1,5 +1,10 @@
 package com.baeldung.commons.collections.orderedmap;
 
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.List;
+
 import org.apache.commons.collections4.OrderedMap;
 import org.apache.commons.collections4.OrderedMapIterator;
 import org.apache.commons.collections4.map.LinkedMap;
@@ -7,11 +12,6 @@ import org.apache.commons.collections4.map.ListOrderedMap;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.ArrayList;
-import java.util.List;
-
-import static org.junit.Assert.assertEquals;
-
 public class OrderedMapUnitTest {
 
     private String[] names = {"Emily", "Mathew", "Rose", "John", "Anna"};
@@ -45,11 +45,12 @@ public class OrderedMapUnitTest {
         // as defined in the constant arrays of names and ages:
 
         OrderedMapIterator<String, Integer> runnersIterator = this.runnersLinkedMap.mapIterator();
-        for (int i = 0; runnersIterator.hasNext(); i++) {
+        int i = 0;
+        while (runnersIterator.hasNext()) {
             runnersIterator.next();
-
             assertEquals(runnersIterator.getKey(), this.names[i]);
             assertEquals(runnersIterator.getValue(), this.ages[i]);
+            i++;
         }
     }
 
@@ -59,11 +60,12 @@ public class OrderedMapUnitTest {
         // as defined in the constant arrays of names and ages:
 
         OrderedMapIterator<String, Integer> runnersIterator = this.runnersListOrderedMap.mapIterator();
-        for (int i = 0; runnersIterator.hasNext(); i++) {
+        int i = 0;
+        while (runnersIterator.hasNext()) {
             runnersIterator.next();
-
             assertEquals(runnersIterator.getKey(), this.names[i]);
             assertEquals(runnersIterator.getValue(), this.ages[i]);
+            i++;
         }
     }
 
@@ -73,9 +75,11 @@ public class OrderedMapUnitTest {
         // as defined in the constant arrays of names and ages
 
         String name = this.runnersLinkedMap.firstKey();
-        for (int i = 0; name != null; i++) {
+        int i = 0;
+        while (name != null) {
             assertEquals(name, this.names[i]);
             name = this.runnersLinkedMap.nextKey(name);
+            i++;
         }
     }
 
@@ -85,9 +89,11 @@ public class OrderedMapUnitTest {
         // as defined in the constant arrays of names and ages
 
         String name = this.runnersListOrderedMap.firstKey();
-        for (int i = 0; name != null; i++) {
+        int i = 0;
+        while (name != null) {
             assertEquals(name, this.names[i]);
             name = this.runnersListOrderedMap.nextKey(name);
+            i++;
         }
     }
 
@@ -97,9 +103,11 @@ public class OrderedMapUnitTest {
         // as defined in the constant arrays of names and ages
 
         String name = this.runnersLinkedMap.lastKey();
-        for (int i = RUNNERS_COUNT - 1; name != null; i--) {
+        int i = RUNNERS_COUNT - 1;
+        while (name != null) {
             assertEquals(name, this.names[i]);
             name = this.runnersLinkedMap.previousKey(name);
+            i--;
         }
     }
 
@@ -109,9 +117,11 @@ public class OrderedMapUnitTest {
         // as defined in the constant arrays of names and ages
 
         String name = this.runnersListOrderedMap.lastKey();
-        for (int i = RUNNERS_COUNT - 1; name != null; i--) {
+        int i = RUNNERS_COUNT - 1;
+        while (name != null) {
             assertEquals(name, this.names[i]);
             name = this.runnersListOrderedMap.previousKey(name);
+            i--;
         }
     }