Merge pull request #8 from eugenp/master

sync up

algorithms-miscellaneous-4/src/main/java/com/baeldung/algorithms/smallestinteger/SmallestMissingPositiveInteger.java

@@ -0,0 +1,37 @@
+package com.baeldung.algorithms.smallestinteger;
+
+import java.util.Arrays;
+
+public class SmallestMissingPositiveInteger {
+    public static int searchInSortedArray(int[] input) {
+        for (int i = 0; i < input.length; i++) {
+            if (i != input[i]) {
+                return i;
+            }
+        }
+
+        return input.length;
+    }
+
+    public static int searchInUnsortedArraySortingFirst(int[] input) {
+        Arrays.sort(input);
+        return searchInSortedArray(input);
+    }
+
+    public static int searchInUnsortedArrayBooleanArray(int[] input) {
+        boolean[] flags = new boolean[input.length];
+        for (int number : input) {
+            if (number < flags.length) {
+                flags[number] = true;
+            }
+        }
+
+        for (int i = 0; i < flags.length; i++) {
+            if (!flags[i]) {
+                return i;
+            }
+        }
+
+        return flags.length;
+    }
+}

algorithms-miscellaneous-4/src/test/java/com/baeldung/algorithms/smallestinteger/SmallestMissingPositiveIntegerUnitTest.java

@@ -0,0 +1,88 @@
+package com.baeldung.algorithms.smallestinteger;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SmallestMissingPositiveIntegerUnitTest {
+    @Test
+    void givenArrayWithThreeMissing_whenSearchInSortedArray_thenThree() {
+        int[] input = new int[] {0, 1, 2, 4, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInSortedArray(input);
+
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    void givenArrayWithOneAndThreeMissing_whenSearchInSortedArray_thenOne() {
+        int[] input = new int[] {0, 2, 4, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInSortedArray(input);
+
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    void givenArrayWithoutMissingInteger_whenSearchInSortedArray_thenArrayLength() {
+        int[] input = new int[] {0, 1, 2, 3, 4, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInSortedArray(input);
+
+        assertThat(result).isEqualTo(input.length);
+    }
+
+    @Test
+    void givenArrayWithThreeMissing_whenSearchInUnsortedArraySortingFirst_thenThree() {
+        int[] input = new int[] {1, 4, 0, 5, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArraySortingFirst(input);
+
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    void givenArrayWithOneAndThreeMissing_whenSearchInUnsortedArraySortingFirst_thenOne() {
+        int[] input = new int[] {4, 2, 0, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArraySortingFirst(input);
+
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    void givenArrayWithoutMissingInteger_whenSearchInUnsortedArraySortingFirst_thenArrayLength() {
+        int[] input = new int[] {4, 5, 1, 3, 0, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArraySortingFirst(input);
+
+        assertThat(result).isEqualTo(input.length);
+    }
+
+    @Test
+    void givenArrayWithThreeMissing_whenSearchInUnsortedArrayBooleanArray_thenThree() {
+        int[] input = new int[] {1, 4, 0, 5, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArrayBooleanArray(input);
+
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    void givenArrayWithOneAndThreeMissing_whenSearchInUnsortedArrayBooleanArray_thenOne() {
+        int[] input = new int[] {4, 2, 0, 5};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArrayBooleanArray(input);
+
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    void givenArrayWithoutMissingInteger_whenSearchInUnsortedArrayBooleanArray_thenArrayLength() {
+        int[] input = new int[] {4, 5, 1, 3, 0, 2};
+
+        int result = SmallestMissingPositiveInteger.searchInUnsortedArrayBooleanArray(input);
+
+        assertThat(result).isEqualTo(input.length);
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/binarygap/BinaryGap.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.binarygap;
+
+public class BinaryGap {
+    static int calculateBinaryGap(int n) {
+        return calculateBinaryGap(n >>> Integer.numberOfTrailingZeros(n), 0, 0);
+    }
+
+    static int calculateBinaryGap(int n, int current, int maximum) {
+        if (n == 0) {
+            return maximum;
+        } else if ((n & 1) == 0) {
+            return calculateBinaryGap(n >>> 1, current + 1, maximum);
+        } else {
+            return calculateBinaryGap(n >>> 1, 0, Math.max(maximum, current));
+        }
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/binarygap/BinaryGapUnitTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.binarygap;
+
+import static com.baeldung.algorithms.binarygap.BinaryGap.calculateBinaryGap;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class BinaryGapUnitTest {
+
+    @Test public void givenNoOccurrenceOfBoundedZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(63);
+        assertEquals(0, result);
+    }
+
+    @Test public void givenTrailingZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(40);
+        assertEquals(1, result);
+    }
+
+    @Test public void givenSingleOccurrenceOfBoundedZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(9);
+        assertEquals(2, result);
+    }
+
+    @Test public void givenMultipleOccurrenceOfBoundedZeros_whenCalculateBinaryGap_thenOutputCorrectResult() {
+
+        int result = calculateBinaryGap(145);
+        assertEquals(3, result);
+    }
+
+}

core-java-modules/README.md

@@ -5,6 +5,5 @@ This module contains modules about core Java
 ## Relevant articles:
 
 - [Multi-Module Maven Application with Java Modules](https://www.baeldung.com/maven-multi-module-project-java-jpms)
-- [Guide to Java FileChannel](https://www.baeldung.com/java-filechannel)
 - [Understanding the NumberFormatException in Java](https://www.baeldung.com/java-number-format-exception)
 - [Will an Error Be Caught by Catch Block in Java?](https://www.baeldung.com/java-error-catch)

core-java-modules/core-java-9-improvements/README.md

@@ -0,0 +1,17 @@
+## Core Java 9
+
+This module contains articles about the improvements to core Java features introduced with Java 9.
+
+### Relevant Articles:
+
+- [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
+- [Java 9 Optional API Additions](https://www.baeldung.com/java-9-optional)
+- [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
+- [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
+- [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
+- [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)
+
+#### Relevant articles not in this module:
+
+- [Java 9 Process API Improvements](https://www.baeldung.com/java-9-process-api) (see the [core-java-os](/core-java-os) module)
+

core-java-modules/core-java-9-improvements/pom.xml

@@ -0,0 +1,73 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-9</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.jayway.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${awaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>apache.snapshots</id>
+            <url>http://repository.apache.org/snapshots/</url>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <!-- testing -->
+        <assertj.version>3.10.0</assertj.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <awaitility.version>1.7.0</awaitility.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+        <guava.version>25.1-jre</guava.version>
+    </properties>
+
+</project>

core-java-modules/core-java-9-jigsaw/README.md

@@ -0,0 +1,11 @@
+## Core Java 9
+
+This module contains articles about Project Jigsaw and the Java Platform Module System (JPMS), introduced with Java 9.
+
+### Relevant Articles:
+
+- [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)
+- [A Guide to Java 9 Modularity](https://www.baeldung.com/java-9-modularity)
+- [Java 9 java.lang.Module API](https://www.baeldung.com/java-9-module-api)
+
+

core-java-modules/core-java-9-jigsaw/pom.xml

@@ -0,0 +1,35 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-9-jigsaw</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <build>
+        <finalName>core-java-9-jigsaw</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+    </properties>
+
+</project>

core-java-modules/core-java-9-new-features/README.md

@@ -0,0 +1,14 @@
+## Core Java 9
+
+This module contains articles about core Java features that have been introduced in Java 9.
+
+### Relevant Articles:
+
+- [Java 9 New Features](https://www.baeldung.com/new-java-9)
+- [Java 9 Variable Handles Demystified](http://www.baeldung.com/java-variable-handles)
+- [Exploring the New HTTP Client in Java 9 and 11](http://www.baeldung.com/java-9-http-client)
+- [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)
+- [Ahead of Time Compilation (AoT)](https://www.baeldung.com/ahead-of-time-compilation)
+- [Introduction to Java 9 StackWalking API](https://www.baeldung.com/java-9-stackwalking-api)
+- [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
+- [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)

core-java-modules/core-java-9-new-features/pom.xml

@@ -0,0 +1,60 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-9-new-features</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9-new-features</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>apache.snapshots</id>
+            <url>http://repository.apache.org/snapshots/</url>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <!-- testing -->
+        <assertj.version>3.10.0</assertj.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+    </properties>
+
+</project>

core-java-modules/core-java-9/.gitignore

@@ -1,13 +0,0 @@
-*.class
-
-#folders#
-/target
-/neoDb*
-/data
-/src/main/webapp/WEB-INF/classes
-*/META-INF/*
-
-# Packaged files #
-*.jar
-*.war
-*.ear

core-java-modules/core-java-9/README.md

@@ -4,28 +4,13 @@ This module contains articles about Java 9 core features
 
 ### Relevant Articles:
 
-- [Java 9 New Features](https://www.baeldung.com/new-java-9)
-- [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
-- [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)
-- [Java 9 Variable Handles Demystified](http://www.baeldung.com/java-variable-handles)
-- [Exploring the New HTTP Client in Java 9 and 11](http://www.baeldung.com/java-9-http-client)
 - [Method Handles in Java](http://www.baeldung.com/java-method-handles)
 - [Introduction to Chronicle Queue](http://www.baeldung.com/java-chronicle-queue)
 - [Optional orElse Optional](http://www.baeldung.com/java-optional-or-else-optional)
 - [Iterate Through a Range of Dates in Java](https://www.baeldung.com/java-iterate-date-range)
 - [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
 - [Immutable Set in Java](https://www.baeldung.com/java-immutable-set)
-- [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)
-- [Ahead of Time Compilation (AoT)](https://www.baeldung.com/ahead-of-time-compilation)
-- [Java 9 Process API Improvements](https://www.baeldung.com/java-9-process-api)
-- [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
-- [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)
-- [Java 9 Optional API Additions](https://www.baeldung.com/java-9-optional)
-- [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)
-- [Introduction to Java 9 StackWalking API](https://www.baeldung.com/java-9-stackwalking-api)
-- [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
-- [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
-- [A Guide to Java 9 Modularity](https://www.baeldung.com/java-9-modularity)
-- [Java 9 java.lang.Module API](https://www.baeldung.com/java-9-module-api)
-- [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
 - [Filtering a Stream of Optionals in Java](https://www.baeldung.com/java-filter-stream-of-optional)
+
+Note: also contains part of the code for the article
+[How to Filter a Collection in Java](https://www.baeldung.com/java-collection-filtering).

core-java-modules/core-java-9/src/main/java/.gitignore

@@ -1,13 +0,0 @@
-*.class
-
-#folders#
-/target
-/neoDb*
-/data
-/src/main/webapp/WEB-INF/classes
-*/META-INF/*
-
-# Packaged files #
-*.jar
-*.war
-*.ear

core-java-modules/core-java-9/src/test/java/com/baeldung/java9/README.MD

@@ -1,2 +0,0 @@
-### Relevant Artiles:
-- [Filtering a Stream of Optionals in Java](http://www.baeldung.com/java-filter-stream-of-optional)

core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/duplicatescounter/DuplicatesCounter.java

@@ -1,4 +1,4 @@
-package com.baeldung.list;
+package com.baeldung.list.duplicatescounter;
 
 import java.util.HashMap;
 import java.util.List;

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/collection/filtering/CollectionFilteringUnitTest.java

@@ -33,9 +33,9 @@ public class CollectionFilteringUnitTest {
 
         for (Employee employee : originalList) {
             for (String name : nameFilter) {
-                if (employee.getName()
-                    .equalsIgnoreCase(name)) {
+                if (employee.getName().equals(name)) {
                     filteredList.add(employee);
+                    //break;
                 }
             }
         }

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/duplicatescounter/DuplicatesCounterUnitTest.java

@@ -1,4 +1,4 @@
-package com.baeldung.list;
+package com.baeldung.list.duplicatescounter;
 
 import org.assertj.core.util.Lists;
 import org.junit.jupiter.api.Test;

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

@@ -11,148 +11,171 @@ 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();
-        }
-
+    public void givenDir_whenMkdir_thenDirIsDeleted() {
+        File directory = new File("dir");
+        assertTrue(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();
+    public void givenFile_whenCreateNewFile_thenFileIsDeleted() {
+        File file = new File("file.txt");
+        try {
+            assertTrue(file.createNewFile());
+        } catch (IOException e) {
+            fail("Could not create " + "file.txt");
         }
-
         assertTrue(file.delete());
     }
 
-
     @Test
-    public void givenFileCreated_whenCreateNewFileInvoked_thenMetadataIsAsExpected() throws IOException {
+    public void givenFile_whenCreateNewFile_thenMetadataIsCorrect() {
 
-        // different Operating systems have different separator characters
-        String separatorCharacter = System.getProperty("file.separator");
+        String sep = File.separator;
 
-        File parentDirectory = makeDirectory("filesDirectory");
+        File parentDir = makeDir("filesDir");
 
-        File childFile = new File(parentDirectory, "file1.txt");
-        childFile.createNewFile();
+        File child = new File(parentDir, "file.txt");
+        try {
+            child.createNewFile();
+        } catch (IOException e) {
+            fail("Could not create " + "file.txt");
+        }
 
-        assertTrue(childFile.getName().equals("file1.txt"));
-        assertTrue(childFile.getParentFile().getName().equals(parentDirectory.getName()));
-        assertTrue(childFile.getPath().equals(parentDirectory.getPath() + separatorCharacter + "file1.txt"));
+        assertEquals("file.txt", child.getName());
+        assertEquals(parentDir.getName(), child.getParentFile().getName());
+        assertEquals(parentDir.getPath() + sep + "file.txt", child.getPath());
 
-        removeDirectory(parentDirectory);
+        removeDir(parentDir);
     }
 
 
-    @Test(expected = FileNotFoundException.class)
-    public void givenReadOnlyFileCreated_whenCreateNewFileInvoked_thenFileCannotBeWrittenTo() throws IOException {
-        File parentDirectory = makeDirectory("filesDirectory");
+    @Test
+    public void givenReadOnlyFile_whenCreateNewFile_thenCantModFile() {
+        File parentDir = makeDir("readDir");
 
-        File childFile = new File(parentDirectory, "file1.txt");
-        childFile.createNewFile();
-
-        childFile.setWritable(false);
-
-        FileOutputStream fos = new FileOutputStream(childFile);
+        File child = new File(parentDir, "file.txt");
+        try {
+            child.createNewFile();
+        } catch (IOException e) {
+            fail("Could not create " + "file.txt");
+        }
+        child.setWritable(false);
+        boolean writable = true;
+        try (FileOutputStream fos = new FileOutputStream(child)) {
             fos.write("Hello World".getBytes()); // write operation
             fos.flush();
-        fos.close();
-
-        removeDirectory(parentDirectory);
+        } catch (IOException e) {
+            writable = false;
+        } finally {
+            removeDir(parentDir);
         }
-
-    @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);
+        assertFalse(writable);
     }
 
     @Test
-    public void givenFilesCreatedInDirectory_whenCreateNewFileInvoked_thenTheyCanBeListedAsExpected() throws IOException {
-        File directory = makeDirectory("filtersDirectory");
+    public void givenWriteOnlyFile_whenCreateNewFile_thenCantReadFile() {
+        File parentDir = makeDir("writeDir");
 
-        File csvFile = new File(directory, "csvFile.csv");
-        csvFile.createNewFile();
+        File child = new File(parentDir, "file.txt");
+        try {
+            child.createNewFile();
+        } catch (IOException e) {
+            fail("Could not create " + "file.txt");
+        }
+        child.setReadable(false);
+        boolean readable = true;
+        try (FileInputStream fis = new FileInputStream(child)) {
+            fis.read(); // read operation
+        } catch (IOException e) {
+            readable = false;
+        } finally {
+            removeDir(parentDir);
+        }
+        assertFalse(readable);
+    }
 
-        File txtFile = new File(directory, "txtFile.txt");
-        txtFile.createNewFile();
+    @Test
+    public void givenFilesInDir_whenCreateNewFile_thenCanListFiles() {
+        File parentDir = makeDir("filtersDir");
+
+        String[] files = {"file1.csv", "file2.txt"};
+        for (String file : files) {
+            try {
+                new File(parentDir, file).createNewFile();
+            } catch (IOException e) {
+                fail("Could not create " + file);
+            }
+        }
 
         //normal listing
-        assertEquals(2, directory.list().length);
+        assertEquals(2, parentDir.list().length);
 
         //filtered listing
         FilenameFilter csvFilter = (dir, ext) -> ext.endsWith(".csv");
-        assertEquals(1, directory.list(csvFilter).length);
+        assertEquals(1, parentDir.list(csvFilter).length);
 
-        removeDirectory(directory);
+        removeDir(parentDir);
     }
 
     @Test
-    public void givenDirectoryIsCreated_whenMkdirInvoked_thenDirectoryCanBeRenamed() {
+    public void givenDir_whenMkdir_thenCanRenameDir() {
 
-        File source = makeDirectory("source");
-        File destination = makeDirectory("destination");
-        source.renameTo(destination);
+        File source = makeDir("source");
+        File destination = makeDir("destination");
+        boolean renamed = source.renameTo(destination);
 
+        if (renamed) {
             assertFalse(source.isDirectory());
             assertTrue(destination.isDirectory());
 
-        removeDirectory(destination);
+            removeDir(destination);
+        }
     }
 
     @Test
-    public void givenDataIsWrittenToFile_whenWriteIsInvoked_thenFreeSpaceOnSystemDecreases() throws IOException {
+    public void givenDataWritten_whenWrite_thenFreeSpaceReduces() {
 
-        String name = System.getProperty("user.home") + System.getProperty("file.separator") + "test";
-        File testDir = makeDirectory(name);
+        String home = System.getProperty("user.home");
+        String sep = File.separator;
+        File testDir = makeDir(home + sep + "test");
         File sample = new File(testDir, "sample.txt");
 
-        long freeSpaceBeforeWrite = testDir.getFreeSpace();
+        long freeSpaceBefore = testDir.getFreeSpace();
+        try {
             writeSampleDataToFile(sample);
-
-        long freeSpaceAfterWrite = testDir.getFreeSpace();
-        assertTrue(freeSpaceAfterWrite < freeSpaceBeforeWrite);
-
-        removeDirectory(testDir);
+        } catch (IOException e) {
+            fail("Could not write to " + "sample.txt");
         }
 
-    private static File makeDirectory(String directoryName) {
-        File directory = new File(directoryName);
+        long freeSpaceAfter = testDir.getFreeSpace();
+        assertTrue(freeSpaceAfter < freeSpaceBefore);
+
+        removeDir(testDir);
+    }
+
+    private static File makeDir(String name) {
+        File directory = new File(name);
         directory.mkdir();
         if (directory.isDirectory()) {
             return directory;
         }
-        throw new RuntimeException("Directory not created for " + directoryName);
+        throw new RuntimeException("'" + name + "' not made!");
     }
 
-    private static void removeDirectory(File directory) {
+    private static void removeDir(File directory) {
         // make sure you don't delete your home directory here
-        if (directory.getPath().equals(System.getProperty("user.home"))) {
+        String home = System.getProperty("user.home");
+        if (directory.getPath().equals(home)) {
             return;
         }
 
         // remove directory and its files from system
-        if (directory != null && directory.exists()) {
+        if (directory.exists()) {
             // delete all files inside the directory
-            File[] filesInDirectory = directory.listFiles();
-            if (filesInDirectory != null) {
-                List<File> files = Arrays.asList(filesInDirectory);
+            File[] dirFiles = directory.listFiles();
+            if (dirFiles != null) {
+                List<File> files = Arrays.asList(dirFiles);
                 files.forEach(f -> deleteFile(f));
             }
 
@@ -171,8 +194,8 @@ public class FileClassDemoUnitTest {
         //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());
+                String text = "Sample line number " + i + "\n";
+                out.write(text.getBytes());
             }
         }
     }

core-java-modules/core-java-io/README.md

@@ -13,22 +13,11 @@ This module contains articles about core Java input and output (IO)
 - [Differences Between the Java WatchService API and the Apache Commons IO Monitor Library](http://www.baeldung.com/java-watchservice-vs-apache-commons-io-monitor-library)
 - [File Size in Java](http://www.baeldung.com/java-file-size)
 - [Comparing getPath(), getAbsolutePath(), and getCanonicalPath() in Java](http://www.baeldung.com/java-path)
-- [Using Java MappedByteBuffer](http://www.baeldung.com/java-mapped-byte-buffer)
 - [How to Copy a File with Java](http://www.baeldung.com/java-copy-file)
 - [Java – Append Data to a File](http://www.baeldung.com/java-append-to-file)
 - [FileNotFoundException in Java](http://www.baeldung.com/java-filenotfound-exception)
 - [How to Read a File in Java](http://www.baeldung.com/reading-file-in-java)
-- [A Guide To NIO2 Asynchronous File Channel](http://www.baeldung.com/java-nio2-async-file-channel)
-- [A Guide To NIO2 FileVisitor](http://www.baeldung.com/java-nio2-file-visitor)
-- [A Guide To NIO2 File Attribute APIs](http://www.baeldung.com/java-nio2-file-attribute)
-- [Introduction to the Java NIO2 File API](http://www.baeldung.com/java-nio-2-file-api)
 - [Zipping and Unzipping in Java](http://www.baeldung.com/java-compress-and-uncompress)
-- [Java NIO2 Path API](http://www.baeldung.com/java-nio-2-path)
-- [A Guide to WatchService in Java NIO2](http://www.baeldung.com/java-nio2-watchservice)
-- [Guide to Java NIO2 Asynchronous Channel APIs](http://www.baeldung.com/java-nio-2-async-channels)
-- [A Guide to NIO2 Asynchronous Socket Channel](http://www.baeldung.com/java-nio2-async-socket-channel)
-- [Download a File From an URL in Java](http://www.baeldung.com/java-download-file)
-- [Create a Symbolic Link with Java](http://www.baeldung.com/java-symlink)
 - [Quick Use of FilenameFilter](http://www.baeldung.com/java-filename-filter)
 - [Read a File into an ArrayList](https://www.baeldung.com/java-file-to-arraylist)
 - [Guide to Java OutputStream](https://www.baeldung.com/java-outputstream)
@@ -40,6 +29,5 @@ This module contains articles about core Java input and output (IO)
 - [How to Write to a CSV File in Java](https://www.baeldung.com/java-csv)
 - [List Files in a Directory in Java](https://www.baeldung.com/java-list-directory-files)
 - [Java InputStream to Byte Array and ByteBuffer](https://www.baeldung.com/convert-input-stream-to-array-of-bytes)
-- [Introduction to the Java NIO Selector](https://www.baeldung.com/java-nio-selector)
 - [How to Avoid the Java FileNotFoundException When Loading Resources](https://www.baeldung.com/java-classpath-resource-cannot-be-opened)
 - [[More -->]](/core-java-modules/core-java-io-2)

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

@@ -27,12 +27,6 @@
             <version>${hsqldb.version}</version>
             <scope>runtime</scope>
         </dependency>
-        <!-- https://mvnrepository.com/artifact/org.asynchttpclient/async-http-client -->
-        <dependency>
-            <groupId>org.asynchttpclient</groupId>
-            <artifactId>async-http-client</artifactId>
-            <version>${async-http-client.version}</version>
-        </dependency>
         <dependency>
             <groupId>com.opencsv</groupId>
             <artifactId>opencsv</artifactId>
@@ -155,7 +149,6 @@
         <!-- maven plugins -->
         <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
         <hsqldb.version>2.4.0</hsqldb.version>
-        <async-http-client.version>2.4.5</async-http-client.version>
         <!-- Mime Type Libraries -->
         <tika.version>1.18</tika.version>
         <jmime-magic.version>0.1.5</jmime-magic.version>

core-java-modules/core-java-io/src/main/java/com/baeldung/java/nio/selector/README.md

@@ -1,2 +0,0 @@
-###Relevant Articles:
-- [Introduction to the Java NIO Selector](http://www.baeldung.com/java-nio-selector)

core-java-modules/core-java-io/src/test/java/com/baeldung/filechannel/FileChannelUnitTest.java

@@ -1,165 +0,0 @@
-package com.baeldung.filechannel;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-
-import java.io.ByteArrayOutputStream;
-import java.io.FileInputStream;
-import java.io.FileOutputStream;
-import java.io.IOException;
-import java.io.RandomAccessFile;
-import java.nio.ByteBuffer;
-import java.nio.MappedByteBuffer;
-import java.nio.channels.FileChannel;
-import java.nio.channels.FileLock;
-import java.nio.charset.StandardCharsets;
-
-import org.junit.Test;
-
-public class FileChannelUnitTest {
-
-    @Test
-    public void givenFile_whenReadWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException {
-
-        try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); 
-            FileChannel channel = reader.getChannel(); 
-            ByteArrayOutputStream out = new ByteArrayOutputStream();) {
-
-            int bufferSize = 1024;
-            if (bufferSize > channel.size()) {
-                bufferSize = (int) channel.size();
-            }
-            ByteBuffer buff = ByteBuffer.allocate(bufferSize);
-
-            while (channel.read(buff) > 0) {
-                out.write(buff.array(), 0, buff.position());
-                buff.clear();
-            }
-
-            String fileContent = new String(out.toByteArray(), StandardCharsets.UTF_8);
-
-            assertEquals("Hello world", fileContent);
-        }
-    }
-
-    @Test
-    public void givenFile_whenReadWithFileChannelUsingFileInputStream_thenCorrect() throws IOException {
-
-        try (ByteArrayOutputStream out = new ByteArrayOutputStream(); 
-            FileInputStream fin = new FileInputStream("src/test/resources/test_read.in"); 
-            FileChannel channel = fin.getChannel();) {
-
-            int bufferSize = 1024;
-            if (bufferSize > channel.size()) {
-                bufferSize = (int) channel.size();
-            }
-            ByteBuffer buff = ByteBuffer.allocate(bufferSize);
-
-            while (channel.read(buff) > 0) {
-                out.write(buff.array(), 0, buff.position());
-                buff.clear();
-            }
-            String fileContent = new String(out.toByteArray(), StandardCharsets.UTF_8);
-
-            assertEquals("Hello world", fileContent);
-        }
-    }
-
-    @Test
-    public void givenFile_whenReadAFileSectionIntoMemoryWithFileChannel_thenCorrect() throws IOException {
-
-        try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); 
-            FileChannel channel = reader.getChannel(); 
-            ByteArrayOutputStream out = new ByteArrayOutputStream();) {
-
-            MappedByteBuffer buff = channel.map(FileChannel.MapMode.READ_ONLY, 6, 5);
-
-            if (buff.hasRemaining()) {
-                byte[] data = new byte[buff.remaining()];
-                buff.get(data);
-                assertEquals("world", new String(data, StandardCharsets.UTF_8));
-            }
-        }
-    }
-
-    @Test
-    public void whenWriteWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException {
-        String file = "src/test/resources/test_write_using_filechannel.txt";
-        try (RandomAccessFile writer = new RandomAccessFile(file, "rw"); 
-            FileChannel channel = writer.getChannel();) {
-            ByteBuffer buff = ByteBuffer.wrap("Hello world".getBytes(StandardCharsets.UTF_8));
-
-            channel.write(buff);
-
-            // now we verify whether the file was written correctly
-            RandomAccessFile reader = new RandomAccessFile(file, "r");
-            assertEquals("Hello world", reader.readLine());
-            reader.close();
-        }
-    }
-
-    @Test
-    public void givenFile_whenWriteAFileUsingLockAFileSectionWithFileChannel_thenCorrect() throws IOException {
-        try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "rw"); 
-            FileChannel channel = reader.getChannel(); 
-            FileLock fileLock = channel.tryLock(6, 5, Boolean.FALSE);) {
-
-            assertNotNull(fileLock);
-        }
-    }
-
-    @Test
-    public void givenFile_whenReadWithFileChannelGetPosition_thenCorrect() throws IOException {
-
-        try (ByteArrayOutputStream out = new ByteArrayOutputStream(); 
-            RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); 
-            FileChannel channel = reader.getChannel();) {
-
-            int bufferSize = 1024;
-            if (bufferSize > channel.size()) {
-                bufferSize = (int) channel.size();
-            }
-            ByteBuffer buff = ByteBuffer.allocate(bufferSize);
-
-            while (channel.read(buff) > 0) {
-                out.write(buff.array(), 0, buff.position());
-                buff.clear();
-            }
-
-            // the original file is 11 bytes long, so that's where the position pointer should be
-            assertEquals(11, channel.position());
-
-            channel.position(4);
-            assertEquals(4, channel.position());
-        }
-    }
-
-    @Test
-    public void whenGetFileSize_thenCorrect() throws IOException {
-
-        try (RandomAccessFile reader = new RandomAccessFile("src/test/resources/test_read.in", "r"); 
-            FileChannel channel = reader.getChannel();) {
-
-            // the original file is 11 bytes long, so that's where the position pointer should be
-            assertEquals(11, channel.size());
-        }
-    }
-
-    @Test
-    public void whenTruncateFile_thenCorrect() throws IOException {
-        String input = "this is a test input";
-
-        FileOutputStream fout = new FileOutputStream("src/test/resources/test_truncate.txt");
-        FileChannel channel = fout.getChannel();
-
-        ByteBuffer buff = ByteBuffer.wrap(input.getBytes());
-        channel.write(buff);
-        buff.flip();
-
-        channel = channel.truncate(5);
-        assertEquals(5, channel.size());
-
-        fout.close();
-        channel.close();
-    }
-}

core-java-modules/core-java-io/src/test/java/com/baeldung/java/nio2/README.md

@@ -1,11 +0,0 @@
-### Relevant Articles:
-- [Introduction to the Java NIO2 File API](http://www.baeldung.com/java-nio-2-file-api)
-- [Java NIO2 Path API](http://www.baeldung.com/java-nio-2-path)
-- [A Guide To NIO2 Asynchronous File Channel](http://www.baeldung.com/java-nio2-async-file-channel)
-- [Guide to Selenium with JUnit / TestNG](http://www.baeldung.com/java-selenium-with-junit-and-testng)
-- [A Guide to NIO2 Asynchronous Socket Channel](http://www.baeldung.com/java-nio2-async-socket-channel)
-- [A Guide To NIO2 FileVisitor](http://www.baeldung.com/java-nio2-file-visitor)
-- [A Guide To NIO2 File Attribute APIs](http://www.baeldung.com/java-nio2-file-attribute)
-- [How to use the Spring FactoryBean?](http://www.baeldung.com/spring-factorybean)
-- [A Guide to WatchService in Java NIO2](http://www.baeldung.com/java-nio2-watchservice)
-- [Guide to Java NIO2 Asynchronous Channel APIs](http://www.baeldung.com/java-nio-2-async-channels)

core-java-modules/core-java-io/src/test/resources/test_truncate.txt

@@ -1 +0,0 @@
-this 

core-java-modules/core-java-io/src/test/resources/test_write_using_filechannel.txt

@@ -1 +0,0 @@
-Hello world

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

@@ -15,4 +15,4 @@ This module contains articles about Object-oriented programming (OOP) in Java
 - [Java Interfaces](https://www.baeldung.com/java-interfaces)
 - [Static and Dynamic Binding in Java](https://www.baeldung.com/java-static-dynamic-binding)
 - [Methods in Java](https://www.baeldung.com/java-methods)
-- [[<-- Prev]](/core-java-modules/core-java-lang-oop-2)
+- [[<-- Prev]](/core-java-modules/core-java-lang-oop-2) [[More -->]](/core-java-modules/core-java-lang-oop-4)

core-java-modules/core-java-lang-oop-4/README.md

@@ -0,0 +1,6 @@
+## Core Java Lang OOP (Part 4)
+
+This module contains articles about Object-oriented programming (OOP) in Java
+
+### Relevant Articles:
+- [[<-- Prev]](/core-java-modules/core-java-lang-oop-3)

core-java-modules/core-java-lang-oop-4/pom.xml

@@ -0,0 +1,57 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>core-java-lang-oop-4</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-lang-oop-4</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>
+        <!-- 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>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>${h2.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-lang-oop-4</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-4/src/main/java/com/baeldung/strictfpUsage/Circle.java

@@ -0,0 +1,5 @@
+package com.baeldung.strictfpUsage;
+
+public strictfp interface Circle {
+    double computeArea(double radius);
+}