Merge branch 'BAEL-16646' into BAEL-16646-2

# Conflicts:
#	core-java-modules/pom.xml
#	java-dates/README.md

core-java-modules/core-java-collections-list-2/src/main/java/com/baeldung/findastring/FindAStringInGivenList.java

@@ -0,0 +1,72 @@
+package com.baeldung.findastring;
+
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import org.apache.commons.collections4.IterableUtils;
+import org.apache.commons.collections4.IteratorUtils;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+public class FindAStringInGivenList {
+
+
+    public List<String> findUsingLoopWithRegex(String search, List<String> list) {
+
+        List<String> matches = new ArrayList<String>();
+
+        String pattern = ".*"+search+".*";
+        Pattern p = Pattern.compile(pattern);
+
+        for(String str: list) {
+            if (p.matcher(str).matches()) {
+                matches.add(str);
+            }
+        }
+
+        return matches;
+    }
+
+
+    public List<String> findUsingLoop(String search, List<String> list) {
+
+        List<String> matches = new ArrayList<String>();
+
+        for(String str: list) {
+            if (str.contains(search)) {
+                matches.add(str);
+            }
+        }
+
+        return matches;
+    }
+
+    public List<String> findUsingStream(String search, List<String> list) {
+
+        List<String> matchingElements =
+                list.stream()
+                        .filter(str -> str.trim().contains(search))
+                        .collect(Collectors.toList());
+
+        return matchingElements;
+    }
+
+    public List<String> findUsingGuava(String search, List<String> list) {
+        Iterable<String> result = Iterables.filter(list, Predicates.containsPattern(search));
+
+        return Lists.newArrayList(result.iterator());
+    }
+
+    public List<String> findUsingCommonsCollection(String search, List<String> list) {
+        Iterable<String> result = IterableUtils.filteredIterable(list, new org.apache.commons.collections4.Predicate<String>() {
+            public boolean evaluate(String listElement) {
+                return listElement.contains(search);
+            }
+        });
+
+        return IteratorUtils.toList(result.iterator());
+    }
+
+}

core-java-modules/core-java-collections-list-2/src/test/java/com/baeldung/findastring/FindAStringInListUnitTest.java

@@ -0,0 +1,62 @@
+package com.baeldung.findastring;
+
+import java.util.ArrayList;
+import java.util.List;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.Test;
+public class FindAStringInListUnitTest {
+
+    private static List<String> list = new ArrayList<>();
+
+    static {
+        list.add("Jack and Jill");
+        list.add("James and Sarah");
+        list.add("Sam and Louise");
+        list.add("Jack");
+        list.add("");
+    }
+
+    private static FindAStringInGivenList findAStringInGivenList = new FindAStringInGivenList();
+
+    @Test
+    public void givenAString_whenFoundUsingLoopWithRegex_thenReturnList() {
+        List matchingElements = findAStringInGivenList.findUsingLoopWithRegex("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingLoop_thenReturnList() {
+        List matchingElements = findAStringInGivenList.findUsingLoop("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+
+    @Test
+    public void givenAString_whenFoundUsingStream_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingStream("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingCommonsCollection_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingCommonsCollection("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+    @Test
+    public void givenAString_whenFoundUsingGuava_thenReturnList(){
+        List matchingElements = findAStringInGivenList.findUsingGuava("Jack", list);
+        assertEquals(2, matchingElements.size());
+        assertEquals("Jack and Jill", matchingElements.get(0));
+        assertEquals("Jack", matchingElements.get(1));
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-2/README.md

@@ -0,0 +1,19 @@
+=========
+
+## Core Java Concurrency Advanced Examples
+
+This module contains articles about advanced topics about multithreading with core Java.
+
+### Relevant Articles: 
+- [Semaphores in Java](https://www.baeldung.com/java-semaphore)
+- [Daemon Threads in Java](https://www.baeldung.com/java-daemon-thread)
+- [Priority-based Job Scheduling in Java](https://www.baeldung.com/java-priority-job-schedule)
+- [Brief Introduction to Java Thread.yield()](https://www.baeldung.com/java-thread-yield)
+- [Print Even and Odd Numbers Using 2 Threads](https://www.baeldung.com/java-even-odd-numbers-with-2-threads)
+- [Java CyclicBarrier vs CountDownLatch](https://www.baeldung.com/java-cyclicbarrier-countdownlatch)
+- [Guide to the Fork/Join Framework in Java](https://www.baeldung.com/java-fork-join)
+- [Guide to ThreadLocalRandom in Java](https://www.baeldung.com/java-thread-local-random)
+- [The Thread.join() Method in Java](https://www.baeldung.com/java-thread-join)
+- [Passing Parameters to Java Threads](https://www.baeldung.com/java-thread-parameters)
+
+[[<-- previous]](/core-java-modules/core-java-concurrency-advanced)[[next -->]](/core-java-modules/core-java-concurrency-advanced-3)

core-java-modules/core-java-concurrency-advanced-2/pom.xml

@@ -0,0 +1,59 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-concurrency-advanced-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-concurrency-advanced-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh-generator-annprocess.version}</version>
+        </dependency>
+        
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-concurrency-advanced-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <jmh-core.version>1.19</jmh-core.version>
+        <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>
+        
+        <assertj.version>3.6.1</assertj.version>
+    </properties>
+
+</project>

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierResetExample.java

@@ -4,6 +4,7 @@ import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CyclicBarrier;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
 public class CyclicBarrierResetExample {
@@ -36,6 +37,11 @@ public class CyclicBarrierResetExample {
             });
         }
         es.shutdown();
+        try {
+            es.awaitTermination(1, TimeUnit.SECONDS);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
         return updateCount.get();
     }
 

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/daemon/NewThread.java

@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.daemon;
+
+public class NewThread extends Thread {
+    public void run() {
+    	long startTime = System.currentTimeMillis();
+        while (true) {
+            for (int i = 0; i < 10; i++) {
+                System.out.println(this.getName() + ": New Thread is running..." + i);
+                try {
+                    //Wait for one sec so it doesn't print too fast
+                    Thread.sleep(1000);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+            }
+            // prevent the Thread to run forever. It will finish it's execution after 2 seconds
+            if (System.currentTimeMillis() - startTime > 2000) {
+            	Thread.currentThread().interrupt();
+            	break;
+            }
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/parameters/AverageCalculator.java

@@ -1,4 +1,4 @@
-package com.baeldung.concurrent.parameter;
+package com.baeldung.concurrent.parameters;
 
 import java.util.concurrent.Callable;
 import java.util.stream.IntStream;

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/concurrent/parameters/ParameterizedThreadExample.java

@@ -1,4 +1,4 @@
-package com.baeldung.concurrent.parameter;
+package com.baeldung.concurrent.parameters;
 
 import java.util.concurrent.Callable;
 import java.util.stream.IntStream;

core-java-modules/core-java-concurrency-advanced-2/src/test/java/com/baeldung/concurrent/parameters/ParameterizedThreadUnitTest.java

@@ -1,14 +1,13 @@
-package com.baeldung.parameters;
+package com.baeldung.concurrent.parameters;
 
-import com.baeldung.concurrent.parameter.AverageCalculator;
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
 
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.stream.IntStream;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.Test;
 
 public class ParameterizedThreadUnitTest {
 

core-java-modules/core-java-concurrency-advanced-2/src/test/java/com/baeldung/forkjoin/Java8ForkJoinIntegrationTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.java8;
+package com.baeldung.forkjoin;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;

core-java-modules/core-java-concurrency-advanced-3/README.md

@@ -0,0 +1,9 @@
+=========
+
+## Core Java Concurrency Advanced Examples
+
+This module contains articles about advanced topics about multithreading with core Java.
+
+### Relevant Articles: 
+
+[[<-- previous]](/core-java-modules/core-java-concurrency-advanced-2)

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

@@ -0,0 +1,33 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-concurrency-advanced-3</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-concurrency-advanced-3</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-concurrency-advanced-3</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+    </properties>
+
+</project>

core-java-modules/core-java-concurrency-advanced/.gitignore

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

core-java-modules/core-java-concurrency-advanced/README.md

@@ -1,25 +1,16 @@
 ## Core Java Concurrency Advanced Examples
 
-This module contains articles about advanced concurrency in core Java.
+This module contains articles about advanced topics about multithreading with core Java.
 
 ### Relevant Articles: 
-- [Introduction to Thread Pools in Java](http://www.baeldung.com/thread-pool-java-and-guava)
-- [Guide to CountDownLatch in Java](http://www.baeldung.com/java-countdown-latch)
-- [Guide to java.util.concurrent.Locks](http://www.baeldung.com/java-concurrent-locks)
-- [An Introduction to ThreadLocal in Java](http://www.baeldung.com/java-threadlocal)
-- [LongAdder and LongAccumulator in Java](http://www.baeldung.com/java-longadder-and-longaccumulator)
-- [The Dining Philosophers Problem in Java](http://www.baeldung.com/java-dining-philoshophers)
-- [Guide to the Java Phaser](http://www.baeldung.com/java-phaser)
-- [An Introduction to Atomic Variables in Java](http://www.baeldung.com/java-atomic-variables)
-- [CyclicBarrier in Java](http://www.baeldung.com/java-cyclic-barrier)
-- [Guide to the Volatile Keyword in Java](http://www.baeldung.com/java-volatile)
-- [Semaphores in Java](http://www.baeldung.com/java-semaphore)
-- [Daemon Threads in Java](http://www.baeldung.com/java-daemon-thread)
-- [Priority-based Job Scheduling in Java](http://www.baeldung.com/java-priority-job-schedule)
-- [Brief Introduction to Java Thread.yield()](https://www.baeldung.com/java-thread-yield)
-- [Print Even and Odd Numbers Using 2 Threads](https://www.baeldung.com/java-even-odd-numbers-with-2-threads)
-- [Java CyclicBarrier vs CountDownLatch](https://www.baeldung.com/java-cyclicbarrier-countdownlatch)
-- [Guide to the Fork/Join Framework in Java](http://www.baeldung.com/java-fork-join)
-- [Guide to ThreadLocalRandom in Java](http://www.baeldung.com/java-thread-local-random)
-- [The Thread.join() Method in Java](http://www.baeldung.com/java-thread-join)
-- [Passing Parameters to Java Threads](https://www.baeldung.com/java-thread-parameters)
+- [Introduction to Thread Pools in Java](https://www.baeldung.com/thread-pool-java-and-guava)
+- [Guide to CountDownLatch in Java](https://www.baeldung.com/java-countdown-latch)
+- [Guide to java.util.concurrent.Locks](https://www.baeldung.com/java-concurrent-locks)
+- [An Introduction to ThreadLocal in Java](https://www.baeldung.com/java-threadlocal)
+- [LongAdder and LongAccumulator in Java](https://www.baeldung.com/java-longadder-and-longaccumulator)
+- [The Dining Philosophers Problem in Java](https://www.baeldung.com/java-dining-philoshophers)
+- [Guide to the Java Phaser](https://www.baeldung.com/java-phaser)
+- [An Introduction to Atomic Variables in Java](https://www.baeldung.com/java-atomic-variables)
+- [CyclicBarrier in Java](https://www.baeldung.com/java-cyclic-barrier)
+- [Guide to the Volatile Keyword in Java](https://www.baeldung.com/java-volatile)
+- More Articles: [[next -->]](/core-java-modules/core-java-concurrency-advanced-2)

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

@@ -47,16 +47,6 @@
             <version>${avaitility.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-core</artifactId>
-            <version>${jmh-core.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-annprocess</artifactId>
-            <version>${jmh-generator-annprocess.version}</version>
-        </dependency>
     </dependencies>
 
     <build>
@@ -78,8 +68,6 @@
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
         <avaitility.version>1.7.0</avaitility.version>
-        <jmh-core.version>1.19</jmh-core.version>
-        <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>
     </properties>
 
 </project>

core-java-modules/core-java-concurrency-advanced/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierCompletionMethodExample.java

@@ -4,6 +4,7 @@ import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CyclicBarrier;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
 public class CyclicBarrierCompletionMethodExample {
@@ -35,6 +36,11 @@ public class CyclicBarrierCompletionMethodExample {
             });
         }
         es.shutdown();
+        try {
+            es.awaitTermination(1, TimeUnit.SECONDS);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
         return updateCount.get();
     }
 

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

@@ -12,9 +12,11 @@ public class SemaPhoreDemo {
 		System.out.println("Number of threads waiting to acquire: " + semaphore.getQueueLength());
 
 		if (semaphore.tryAcquire()) {
-			semaphore.acquire();
+			try {		
 			// perform some critical operations
-			semaphore.release();
+			} finally {
+				semaphore.release();
+			}
 		}
 
 	}

core-java-modules/core-java-io-2/src/test/java/com/baeldung/file/FileClassDemoUnitTest.java

@@ -0,0 +1,179 @@
+package com.baeldung.file;
+
+import org.junit.Test;
+
+import java.io.*;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.*;
+
+public class FileClassDemoUnitTest {
+
+    @Test
+    public void givenDirectoryCreated_whenMkdirIsInvoked_thenDirectoryIsDeleted() {
+        File directory = new File("testDirectory");
+        if (!directory.isDirectory() || !directory.exists()) {
+            directory.mkdir();
+        }
+
+        assertTrue(directory.delete());
+    }
+
+    @Test
+    public void givenFileCreated_whenCreateNewFileIsInvoked_thenFileIsDeleted() throws IOException {
+        File file = new File("testFile.txt");
+        if (!file.isFile() || !file.exists()) {
+            file.createNewFile();
+        }
+
+        assertTrue(file.delete());
+    }
+
+
+    @Test
+    public void givenFileCreated_whenCreateNewFileInvoked_thenMetadataIsAsExpected() throws IOException {
+
+        // different Operating systems have different separator characters
+        String separatorCharacter = System.getProperty("file.separator");
+
+        File parentDirectory = makeDirectory("filesDirectory");
+
+        File childFile = new File(parentDirectory, "file1.txt");
+        childFile.createNewFile();
+
+        assertTrue(childFile.getName().equals("file1.txt"));
+        assertTrue(childFile.getParentFile().getName().equals(parentDirectory.getName()));
+        assertTrue(childFile.getPath().equals(parentDirectory.getPath() + separatorCharacter + "file1.txt"));
+
+        removeDirectory(parentDirectory);
+    }
+
+
+    @Test(expected = FileNotFoundException.class)
+    public void givenReadOnlyFileCreated_whenCreateNewFileInvoked_thenFileCannotBeWrittenTo() throws IOException {
+        File parentDirectory = makeDirectory("filesDirectory");
+
+        File childFile = new File(parentDirectory, "file1.txt");
+        childFile.createNewFile();
+
+        childFile.setWritable(false);
+
+        FileOutputStream fos = new FileOutputStream(childFile);
+        fos.write("Hello World".getBytes()); // write operation
+        fos.flush();
+        fos.close();
+
+        removeDirectory(parentDirectory);
+    }
+
+    @Test(expected = FileNotFoundException.class)
+    public void givenWriteOnlyFileCreated_whenCreateNewFileInvoked_thenFileCannotBeReadFrom() throws IOException {
+        File parentDirectory = makeDirectory("filesDirectory");
+
+        File childFile = new File(parentDirectory, "file1.txt");
+        childFile.createNewFile();
+
+        childFile.setReadable(false);
+
+        FileInputStream fis = new FileInputStream(childFile);
+        fis.read(); // read operation
+        fis.close();
+
+        removeDirectory(parentDirectory);
+    }
+
+    @Test
+    public void givenFilesCreatedInDirectory_whenCreateNewFileInvoked_thenTheyCanBeListedAsExpected() throws IOException {
+        File directory = makeDirectory("filtersDirectory");
+
+        File csvFile = new File(directory, "csvFile.csv");
+        csvFile.createNewFile();
+
+        File txtFile = new File(directory, "txtFile.txt");
+        txtFile.createNewFile();
+
+        //normal listing
+        assertEquals(2, directory.list().length);
+
+        //filtered listing
+        FilenameFilter csvFilter = (dir, ext) -> ext.endsWith(".csv");
+        assertEquals(1, directory.list(csvFilter).length);
+
+        removeDirectory(directory);
+    }
+
+    @Test
+    public void givenDirectoryIsCreated_whenMkdirInvoked_thenDirectoryCanBeRenamed() {
+
+        File source = makeDirectory("source");
+        File destination = makeDirectory("destination");
+        source.renameTo(destination);
+
+        assertFalse(source.isDirectory());
+        assertTrue(destination.isDirectory());
+
+        removeDirectory(destination);
+    }
+
+    @Test
+    public void givenDataIsWrittenToFile_whenWriteIsInvoked_thenFreeSpaceOnSystemDecreases() throws IOException {
+
+        String name = System.getProperty("user.home") + System.getProperty("file.separator") + "test";
+        File testDir = makeDirectory(name);
+        File sample = new File(testDir, "sample.txt");
+
+        long freeSpaceBeforeWrite = testDir.getFreeSpace();
+        writeSampleDataToFile(sample);
+
+        long freeSpaceAfterWrite = testDir.getFreeSpace();
+        assertTrue(freeSpaceAfterWrite < freeSpaceBeforeWrite);
+
+        removeDirectory(testDir);
+    }
+
+    private static File makeDirectory(String directoryName) {
+        File directory = new File(directoryName);
+        directory.mkdir();
+        if (directory.isDirectory()) {
+            return directory;
+        }
+        throw new RuntimeException("Directory not created for " + directoryName);
+    }
+
+    private static void removeDirectory(File directory) {
+        // make sure you don't delete your home directory here
+        if (directory.getPath().equals(System.getProperty("user.home"))) {
+            return;
+        }
+
+        // remove directory and its files from system
+        if (directory != null && directory.exists()) {
+            // delete all files inside the directory
+            File[] filesInDirectory = directory.listFiles();
+            if (filesInDirectory != null) {
+                List<File> files = Arrays.asList(filesInDirectory);
+                files.forEach(f -> deleteFile(f));
+            }
+
+            // finally delete the directory itself
+            deleteFile(directory);
+        }
+    }
+
+    private static void deleteFile(File fileToDelete) {
+        if (fileToDelete != null && fileToDelete.exists()) {
+            fileToDelete.delete();
+        }
+    }
+
+    private static void writeSampleDataToFile(File sample) throws IOException {
+        //write sample text to file
+        try (FileOutputStream out = new FileOutputStream(sample)) {
+            for (int i = 1; i <= 100000; i++) {
+                String sampleText = "Sample line number " + i + "\n";
+                out.write(sampleText.getBytes());
+            }
+        }
+    }
+}

core-java-modules/core-java-lambdas/src/test/java/com/baeldung/java8/lambda/methodreference/MethodReferenceUnitTest.java

@@ -35,9 +35,9 @@ public class MethodReferenceUnitTest {
     public void referenceToInstanceMethodOfArbitratyObjectOfParticularType() {
         List<Integer> numbers = Arrays.asList(5, 3, 50, 24, 40, 2, 9, 18);
         numbers.stream()
-            .sorted((a, b) -> Integer.compare(a, b));
+            .sorted((a, b) -> a.compareTo(b));
         numbers.stream()
-            .sorted(Integer::compare);
+            .sorted(Integer::compareTo);
     }
 
     @Test

core-java-modules/core-java-lang-math/README.md

@@ -5,3 +5,4 @@
 ### Relevant Articles: 
 - [Java 8 Math New Methods](https://www.baeldung.com/java-8-math)
 - [Java 8 Unsigned Arithmetic Support](https://www.baeldung.com/java-unsigned-arithmetic)
+- [How to Separate Double into Integer and Decimal Parts](https://www.baeldung.com/java-separate-double-into-integer-decimal-parts)

core-java-modules/core-java-lang-oop-2/README.md

@@ -7,7 +7,6 @@ This module contains articles about Object-oriented programming (OOP) in Java
 - [Cannot Reference “X” Before Supertype Constructor Has Been Called](https://www.baeldung.com/java-cannot-reference-x-before-supertype-constructor-error)
 - [Anonymous Classes in Java](https://www.baeldung.com/java-anonymous-classes)
 - [Raw Types in Java](https://www.baeldung.com/raw-types-java)
-- [Java ‘private’ Access Modifier](https://www.baeldung.com/java-private-keyword)
 - [Marker Interfaces in Java](https://www.baeldung.com/java-marker-interfaces)
 - [Java equals() and hashCode() Contracts](https://www.baeldung.com/java-equals-hashcode-contracts)
 - [Immutable Objects in Java](https://www.baeldung.com/java-immutable-object)

core-java-modules/core-java-lang-oop-3/README.md

@@ -9,4 +9,9 @@ This module contains articles about Object-oriented programming (OOP) in Java
 - [Guide to the this Java Keyword](https://www.baeldung.com/java-this)
 - [Java Public Access Modifier](https://www.baeldung.com/java-public-keyword)
 - [Composition, Aggregation and Association in Java](https://www.baeldung.com/java-composition-aggregation-association)
+- [Nested Classes in Java](https://www.baeldung.com/java-nested-classes)
+- [A Guide to Inner Interfaces in Java](https://www.baeldung.com/java-inner-interfaces)
+- [Java Classes and Objects](https://www.baeldung.com/java-classes-objects)
+- [Java Interfaces](https://www.baeldung.com/java-interfaces)
+- [Static and Dynamic Binding in Java](https://www.baeldung.com/java-static-dynamic-binding)
 - [[<-- Prev]](/core-java-modules/core-java-lang-oop-2)

core-java-modules/core-java-lang-oop-3/pom.xml

@@ -1,7 +1,6 @@
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <groupId>com.baeldung</groupId>
     <artifactId>core-java-lang-oop-3</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-lang-oop-3</name>
@@ -15,6 +14,24 @@
     </parent>
 
     <dependencies>
+        <!-- logging -->
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>${log4j.version}</version>
+        </dependency>
+        <dependency> <!-- needed to bridge to slf4j for projects that use the log4j APIs directly -->
+            <groupId>org.slf4j</groupId>
+            <artifactId>log4j-over-slf4j</artifactId>
+            <version>${org.slf4j.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>com.h2database</groupId>
             <artifactId>h2</artifactId>
@@ -23,4 +40,18 @@
         </dependency>
     </dependencies>
 
+    <build>
+        <finalName>core-java-lang-oop-3</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+
 </project>

core-java-modules/core-java-lang-oop-3/src/main/java/com/baeldung/innerinterfaces/CommaSeparatedCustomers.java

@@ -1,4 +1,4 @@
-package com.baeldung.interfaces;
+package com.baeldung.innerinterfaces;
 
 import java.util.ArrayList;
 import java.util.List;

core-java-modules/core-java-lang-oop-3/src/main/java/com/baeldung/innerinterfaces/Customer.java

@@ -1,4 +1,4 @@
-package com.baeldung.interfaces;
+package com.baeldung.innerinterfaces;
 
 public class Customer {
     public interface List {

core-java-modules/core-java-lang-oop-3/src/main/java/com/baeldung/parameterpassing/NonPrimitives.java

@@ -17,7 +17,7 @@ public class NonPrimitives {
         b1.num++;
     }
 }
- 
+
 class FooClass {
     public int num;
    

core-java-modules/core-java-lang-oop-3/src/test/java/com/baeldung/binding/AnimalUnitTest.java

@@ -14,13 +14,13 @@ import org.mockito.Mock;
 import org.mockito.junit.MockitoJUnitRunner;
 import org.slf4j.LoggerFactory;
 
+import java.util.List;
+
 import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertThat;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
-import java.util.List;
-
 /**
  * Created by madhumita.g on 01-08-2018.
  */

core-java-modules/core-java-lang-oop-3/src/test/java/com/baeldung/innerinterfaces/InnerInterfaceUnitTest.java

@@ -1,11 +1,13 @@
-package com.baeldung.interfaces;
-
-import static org.junit.Assert.assertEquals;
+package com.baeldung.innerinterfaces;
 
+import com.baeldung.innerinterfaces.CommaSeparatedCustomers;
+import com.baeldung.innerinterfaces.Customer;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
+import static org.junit.Assert.assertEquals;
+
 @RunWith(JUnit4.class)
 public class InnerInterfaceUnitTest {
     @Test

core-java-modules/core-java-lang-oop-3/src/test/java/com/baeldung/nestedclass/Enclosing.java

@@ -15,7 +15,7 @@ public class Enclosing {
 
     @Test
     public void test() {
-        Enclosing.StaticNested nested = new Enclosing.StaticNested();
+        StaticNested nested = new StaticNested();
         nested.run();
     }
 }

core-java-modules/core-java-lang-oop-3/src/test/java/com/baeldung/nestedclass/NewOuter.java

@@ -23,7 +23,7 @@ public class NewOuter {
     @Test
     public void test() {
         NewOuter outer = new NewOuter();
-        NewOuter.InnerClass inner = outer.new InnerClass();
+        InnerClass inner = outer.new InnerClass();
         inner.run();
 
     }

core-java-modules/core-java-lang-oop-3/src/test/java/com/baeldung/nestedclass/Outer.java

@@ -14,7 +14,7 @@ public class Outer {
     @Test
     public void test() {
         Outer outer = new Outer();
-        Outer.Inner inner = outer.new Inner();
+        Inner inner = outer.new Inner();
         inner.run();
     }
 }

core-java-modules/core-java-lang-oop-3/src/test/java/com/baeldung/objects/ObjectsUnitTest.java

@@ -1,11 +1,11 @@
 package com.baeldung.objects;
 
-import static org.junit.Assert.*;
-
 import org.junit.Before;
 import org.junit.Test;
 
-public class CarUnitTest {
+import static org.junit.Assert.*;
+
+public class ObjectsUnitTest {
     
     private Car car;
 

core-java-modules/core-java-lang-operators/README.md

@@ -4,3 +4,4 @@
 - [The Modulo Operator in Java](https://www.baeldung.com/modulo-java)
 - [Java instanceof Operator](https://www.baeldung.com/java-instanceof)
 - [A Guide to Increment and Decrement Unary Operators in Java](https://www.baeldung.com/java-unary-operators)
+- [Java Compound Operators](https://www.baeldung.com/java-compound-operators)

core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/diamondoperator/Car.java

@@ -1,4 +1,4 @@
-package com.baeldung.java.diamond;
+package com.baeldung.diamondoperator;
 
 public class Car<T extends Engine> implements Vehicle<T> {
 

core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/diamondoperator/DiamondOperatorUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.java.diamond;
+package com.baeldung.diamondoperator;
 
 import static org.junit.Assert.assertNotNull;
 

core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/diamondoperator/Diesel.java

@@ -1,4 +1,4 @@
-package com.baeldung.java.diamond;
+package com.baeldung.diamondoperator;
 
 public class Diesel implements Engine {
 

core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/diamondoperator/Engine.java

@@ -1,4 +1,4 @@
-package com.baeldung.java.diamond;
+package com.baeldung.diamondoperator;
 
 public interface Engine {
 

core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/diamondoperator/Vehicle.java

@@ -1,4 +1,4 @@
-package com.baeldung.java.diamond;
+package com.baeldung.diamondoperator;
 
 public interface Vehicle<T extends Engine> {
 

core-java-modules/core-java-lang-operators/src/test/java/com/baeldung/keyword/InstanceOfUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.keyword.test;
+package com.baeldung.keyword;
 
 import org.junit.Assert;
 import org.junit.jupiter.api.Test;

core-java-modules/core-java-lang-syntax-2/README.md

@@ -5,4 +5,10 @@ This module contains articles about Java syntax
 ### Relevant Articles: 
 
 - [Java ‘private’ Access Modifier](https://www.baeldung.com/java-private-keyword)
+- [Guide to Java Packages](https://www.baeldung.com/java-packages)
+- [If-Else Statement in Java](https://www.baeldung.com/java-if-else)
+- [Control Structures in Java](https://www.baeldung.com/java-control-structures)
+- [Java Double Brace Initialization](https://www.baeldung.com/java-double-brace-initialization)
+- [The Java Native Keyword and Methods](https://www.baeldung.com/java-native)
+- [Variable Scope in Java](https://www.baeldung.com/java-variable-scope)
 - [[<-- Prev]](/core-java-modules/core-java-lang-syntax)

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/controlstructures/ConditionalBranches.java

@@ -1,4 +1,4 @@
-package com.baeldung.controlstructures;
+package com.baeldung.core.controlstructures;
 
 public class ConditionalBranches {
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/controlstructures/Loops.java

@@ -1,4 +1,4 @@
-package com.baeldung.controlstructures;
+package com.baeldung.core.controlstructures;
 
 public class Loops {
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/nativekeyword/DateTimeUtils.java

@@ -1,4 +1,4 @@
-package com.baeldung.nativekeyword;
+package com.baeldung.core.nativekeyword;
 
 public class DateTimeUtils {
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/nativekeyword/NativeMainApp.java

@@ -1,6 +1,4 @@
-package com.baeldung.nativekeyword;
-
-import com.baeldung.nativekeyword.DateTimeUtils;
+package com.baeldung.core.nativekeyword;
 
 public class NativeMainApp {
     public static void main(String[] args) {

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/packages/TodoApp.java

@@ -1,9 +1,9 @@
-package com.baeldung.packages;
+package com.baeldung.core.packages;
+
+import com.baeldung.core.packages.domain.TodoItem;
 
 import java.time.LocalDate;
 
-import com.baeldung.packages.domain.TodoItem;
-
 public class TodoApp {
 
     public static void main(String[] args) {

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/packages/TodoList.java

@@ -1,10 +1,10 @@
-package com.baeldung.packages;
+package com.baeldung.core.packages;
+
+import com.baeldung.core.packages.domain.TodoItem;
 
 import java.util.ArrayList;
 import java.util.List;
 
-import com.baeldung.packages.domain.TodoItem;
-
 public class TodoList {
     private List<TodoItem> todoItems;
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/packages/domain/TodoItem.java

@@ -1,4 +1,4 @@
-package com.baeldung.packages.domain;
+package com.baeldung.core.packages.domain;
 
 import java.time.LocalDate;
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/privatemodifier/Employee.java

@@ -1,4 +1,4 @@
-package com.baeldung.core.modifiers;
+package com.baeldung.core.privatemodifier;
 
 public class Employee {
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/privatemodifier/ExampleClass.java

@@ -1,4 +1,4 @@
-package com.baeldung.core.modifiers;
+package com.baeldung.core.privatemodifier;
 
 public class ExampleClass {
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/privatemodifier/PublicOuterClass.java

@@ -1,4 +1,4 @@
-package com.baeldung.core.modifiers;
+package com.baeldung.core.privatemodifier;
 
 public class PublicOuterClass {
 

core-java-modules/core-java-lang-syntax-2/src/main/java/com/baeldung/core/scope/BracketScopeExample.java

@@ -1,4 +1,4 @@
-package com.baeldung.scope;
+package com.baeldung.core.scope;
 
 public class BracketScopeExample {