Merge remote-tracking branch 'upstream/master'

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/maximumsubarray/KadaneAlgorithm.java

@@ -13,22 +13,22 @@ public class KadaneAlgorithm {
         int start = 0;
         int end = 0;
 
-        int maxSoFar = 0, maxEndingHere = 0;
-
+        int maxSoFar = arr[0], maxEndingHere = arr[0];
         for (int i = 0; i < size; i++) {
 
             if (arr[i] > maxEndingHere + arr[i]) {
                 start = i;
                 maxEndingHere = arr[i];
-            } else
+            } else {
                 maxEndingHere = maxEndingHere + arr[i];
+            }
 
             if (maxSoFar < maxEndingHere) {
                 maxSoFar = maxEndingHere;
                 end = i;
             }
         }
-        logger.info("Found Maximum Subarray between {} and {}", start, end);
+        logger.info("Found Maximum Subarray between {} and {}", Math.min(start, end), end);
         return maxSoFar;
     }
 }

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/maximumsubarray/KadaneAlgorithmUnitTest.java

@@ -9,11 +9,22 @@ class KadaneAlgorithmUnitTest {
     @Test
     void givenArrayWithNegativeNumberWhenMaximumSubarrayThenReturns6() {
         //given
-        int[] arr = new int[]{-3, 1, -8, 4, -1, 2, 1, -5, 5};
+        int[] arr = new int[] { -3, 1, -8, 4, -1, 2, 1, -5, 5 };
         //when
         KadaneAlgorithm algorithm = new KadaneAlgorithm();
         int maxSum = algorithm.maxSubArraySum(arr);
         //then
         assertEquals(6, maxSum);
     }
+
+    @Test
+    void givenArrayWithAllNegativeNumbersWhenMaximumSubarrayThenReturnsExpectedResult() {
+        //given
+        int[] arr = new int[] { -8, -7, -5, -4, -3, -1, -2 };
+        //when
+        KadaneAlgorithm algorithm = new KadaneAlgorithm();
+        int maxSum = algorithm.maxSubArraySum(arr);
+        //then
+        assertEquals(-1, maxSum);
+    }
 }

apache-poi/README.md

@@ -11,3 +11,4 @@ This module contains articles about Apache POI
 - [Get String Value of Excel Cell with Apache POI](https://www.baeldung.com/java-apache-poi-cell-string-value)
 - [Read Excel Cell Value Rather Than Formula With Apache POI](https://www.baeldung.com/apache-poi-read-cell-value-formula)
 - [Setting Formulas in Excel with Apache POI](https://www.baeldung.com/java-apache-poi-set-formulas)
+- [Insert a Row in Excel Using Apache POI](https://www.baeldung.com/apache-poi-insert-excel-row)

apache-poi/src/test/java/com/baeldung/poi/excel/insert/ExcelInsertRowUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.poi.excel.insert;
+
+import org.apache.poi.ss.usermodel.Sheet;
+import org.apache.poi.ss.usermodel.Workbook;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Paths;
+
+public class ExcelInsertRowUnitTest {
+    private static final String FILE_NAME = "test.xlsx";
+    private static final String NEW_FILE_NAME = "new_test.xlsx";
+    private String fileLocation;
+
+    @Before
+    public void setup() throws URISyntaxException {
+        fileLocation = Paths.get(ClassLoader.getSystemResource(FILE_NAME).toURI()).toString();
+    }
+
+    @Test
+    public void givenWorkbook_whenInsertRowBetween_thenRowCreated() throws IOException {
+        int startRow = 2;
+        int rowNumber = 1;
+        Workbook workbook = new XSSFWorkbook(fileLocation);
+        Sheet sheet = workbook.getSheetAt(0);
+        int lastRow = sheet.getLastRowNum();
+        if (lastRow < startRow) {
+            sheet.createRow(startRow);
+        }
+        sheet.shiftRows(startRow, lastRow, rowNumber, true, true);
+        sheet.createRow(startRow);
+        FileOutputStream outputStream = new FileOutputStream(NEW_FILE_NAME);
+        workbook.write(outputStream);
+        File file = new File(NEW_FILE_NAME);
+
+        final int expectedRowResult = 5;
+        Assertions.assertEquals(expectedRowResult, workbook.getSheetAt(0).getLastRowNum());
+
+        outputStream.close();
+        file.delete();
+        workbook.close();
+    }
+
+}

core-java-modules/core-java-10/README.md

@@ -5,9 +5,10 @@ This module contains articles about Java 10 core features
 ### Relevant Articles: 
 
 - [Java 10 LocalVariable Type-Inference](http://www.baeldung.com/java-10-local-variable-type-inference)
-- [Guide to Java 10](http://www.baeldung.com/java-10-overview)
+- [New Features in Java 10](https://www.baeldung.com/java-10-overview)
 - [Copy a List to Another List in Java](http://www.baeldung.com/java-copy-list-to-another)
 - [Deep Dive Into the New Java JIT Compiler – Graal](https://www.baeldung.com/graal-java-jit-compiler)
 - [Copying Sets in Java](https://www.baeldung.com/java-copy-sets)
 - [Converting between a List and a Set in Java](https://www.baeldung.com/convert-list-to-set-and-set-to-list)
 - [Java IndexOutOfBoundsException “Source Does Not Fit in Dest”](https://www.baeldung.com/java-indexoutofboundsexception)
+- [Collect a Java Stream to an Immutable Collection](https://www.baeldung.com/java-stream-immutable-collection)

core-java-modules/core-java-10/src/test/java/com/baeldung/java10/streams/StreamToImmutableJava10UnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.java10.streams;
+
+import static java.util.stream.Collectors.toUnmodifiableList;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Test;
+
+public class StreamToImmutableJava10UnitTest {
+
+    @Test
+    public void whenUsingCollectorsToUnmodifiableList_thenSuccess() {
+        List<String> givenList = Arrays.asList("a", "b", "c");
+        List<String> result = givenList.stream()
+            .collect(toUnmodifiableList());
+
+        System.out.println(result.getClass());
+    }
+}

core-java-modules/core-java-12/README.md

@@ -1,5 +1,4 @@
 ## Relevant Articles:
 
-
 - [String API Updates in Java 12](https://www.baeldung.com/java12-string-api)
-- [Java 12 New Features](https://www.baeldung.com/java-12-new-features)
+- [New Features in Java 12](https://www.baeldung.com/java-12-new-features)

core-java-modules/core-java-13/README.md

@@ -1,4 +1,4 @@
 ### Relevant articles:
 
 - [Java Switch Statement](https://www.baeldung.com/java-switch)
-- [New Java 13 Features](https://www.baeldung.com/java-13-new-features)
+- [New Features in Java 13](https://www.baeldung.com/java-13-new-features)

core-java-modules/core-java-14/README.md

@@ -10,4 +10,4 @@ This module contains articles about Java 14.
 - [Helpful NullPointerExceptions in Java 14](https://www.baeldung.com/java-14-nullpointerexception)
 - [Foreign Memory Access API in Java 14](https://www.baeldung.com/java-foreign-memory-access)
 - [Java 14 Record Keyword](https://www.baeldung.com/java-record-keyword)
-- [Java 14 – New Features](https://www.baeldung.com/java-14-new-features)
+- [New Features in Java 14](https://www.baeldung.com/java-14-new-features)

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

@@ -4,7 +4,7 @@ This module contains articles about core Java features that have been introduced
 
 ### Relevant Articles:
 
-- [Java 9 New Features](https://www.baeldung.com/new-java-9)
+- [New Features in Java 9](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)

core-java-modules/core-java-annotations/src/main/java/com/baeldung/annotations/AnnotatedClass.java

@@ -0,0 +1,8 @@
+package com.baeldung.annotations;
+
+import javax.annotation.Generated;
+
+@RetentionAnnotation
+@Generated("Available only on source code")
+public class AnnotatedClass {
+}

core-java-modules/core-java-annotations/src/main/java/com/baeldung/annotations/RetentionAnnotation.java

@@ -0,0 +1,12 @@
+package com.baeldung.annotations;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.TYPE;
+
+@Target(TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface RetentionAnnotation {
+}

core-java-modules/core-java-annotations/src/test/java/com/baeldung/annotations/AnnotatedClassUnitTest.java

@@ -0,0 +1,18 @@
+package com.baeldung.annotations;
+
+import org.junit.Test;
+
+import java.lang.annotation.Annotation;
+
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertThat;
+
+public class AnnotatedClassUnitTest {
+
+    @Test
+    public void whenAnnotationRetentionPolicyRuntime_shouldAccess() {
+        AnnotatedClass anAnnotatedClass = new AnnotatedClass();
+        Annotation[] annotations = anAnnotatedClass.getClass().getAnnotations();
+        assertThat(annotations.length, is(1));
+    }
+}

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

@@ -3,4 +3,4 @@
 This module contains articles about Java Character Class
 
 ### Relevant Articles: 
-- [Character#isAlphabetic vs Character#isLetter](https://www.baeldung.com/java-character-isletter-isalphabetic)
+- [Character#isAlphabetic vs. Character#isLetter](https://www.baeldung.com/java-character-isletter-isalphabetic)

core-java-modules/core-java-collections-4/README.md

@@ -5,3 +5,4 @@
 ### Relevant Articles: 
 
 - [ArrayList vs. LinkedList vs. HashMap in Java](https://www.baeldung.com/java-arraylist-vs-linkedlist-vs-hashmap)
+- [Java Deque vs. Stack](https://www.baeldung.com/java-deque-vs-stack)

core-java-modules/core-java-collections-4/pom.xml

@@ -25,7 +25,7 @@
     </dependencies>
 
     <properties>
-        <assertj.version>3.18.0</assertj.version>
+        <assertj.version>3.19.0</assertj.version>
     </properties>
 
 </project>

core-java-modules/core-java-collections-4/src/main/java/com/baeldung/collections/dequestack/ArrayLifoStack.java

@@ -0,0 +1,91 @@
+package com.baeldung.collections.dequestack;
+
+import java.util.ArrayDeque;
+import java.util.Collection;
+import java.util.Deque;
+import java.util.Iterator;
+
+public class ArrayLifoStack<E> implements LifoStack<E> {
+    private final Deque<E> deque = new ArrayDeque<>();
+
+    @Override
+    public void push(E item) {
+        deque.addFirst(item);
+    }
+
+    @Override
+    public E pop() {
+        return deque.removeFirst();
+    }
+
+    @Override
+    public E peek() {
+        return deque.peekFirst();
+    }
+
+    // implementing methods from the Collection interface
+    @Override
+    public int size() {
+        return deque.size();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return deque.isEmpty();
+    }
+
+    @Override
+    public boolean contains(Object o) {
+        return deque.contains(o);
+    }
+
+    @Override
+    public Iterator<E> iterator() {
+        return deque.iterator();
+    }
+
+    @Override
+    public Object[] toArray() {
+        return deque.toArray();
+    }
+
+    @Override
+    public <T> T[] toArray(T[] a) {
+        return deque.toArray(a);
+    }
+
+    @Override
+    public boolean add(E e) {
+        return deque.add(e);
+    }
+
+    @Override
+    public boolean remove(Object o) {
+        return deque.remove(o);
+    }
+
+    @Override
+    public boolean containsAll(Collection<?> c) {
+        return deque.containsAll(c);
+    }
+
+    @Override
+    public boolean addAll(Collection<? extends E> c) {
+        return deque.addAll(c);
+    }
+
+    @Override
+    public boolean removeAll(Collection<?> c) {
+        return deque.removeAll(c);
+    }
+
+    @Override
+    public boolean retainAll(Collection<?> c) {
+        return deque.retainAll(c);
+    }
+
+    @Override
+    public void clear() {
+        deque.clear();
+    }
+}

core-java-modules/core-java-collections-4/src/main/java/com/baeldung/collections/dequestack/LifoStack.java

@@ -0,0 +1,12 @@
+package com.baeldung.collections.dequestack;
+
+import java.util.Collection;
+
+public interface LifoStack<E> extends Collection<E> {
+
+    E peek();
+
+    E pop();
+
+    void push(E item);
+}

core-java-modules/core-java-collections-4/src/test/java/com/baeldung/collections/dequestack/StackVsDequeUnitTest.java

@@ -0,0 +1,90 @@
+package com.baeldung.collections.dequestack;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.Stack;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class StackVsDequeUnitTest {
+
+    @Test
+    void givenAStack_whenAccessByIndex_thenElementCanBeRead() {
+        Stack<String> myStack = new Stack<>();
+        myStack.push("I am the 1st element."); //index 0
+        myStack.push("I am the 2nd element."); //index 1
+        myStack.push("I am the 3rd element."); //index 2
+        //access by index
+        assertThat(myStack.get(0)).isEqualTo("I am the 1st element.");
+    }
+
+    @Test
+    void givenAStack_whenIterate_thenFromBottomToTop() {
+        Stack<String> myStack = new Stack<>();
+        myStack.push("I am at the bottom.");
+        myStack.push("I am in the middle.");
+        myStack.push("I am at the top.");
+
+        Iterator<String> it = myStack.iterator();
+
+        assertThat(it).toIterable().containsExactly(
+          "I am at the bottom.",
+          "I am in the middle.",
+          "I am at the top.");
+    }
+
+    @Test
+    void givenAStack_whenAddOrRemoveByIndex_thenElementCanBeAddedOrRemoved() {
+        Stack<String> myStack = new Stack<>();
+        myStack.push("I am the 1st element.");
+        myStack.push("I am the 3rd element.");
+
+        assertThat(myStack.size()).isEqualTo(2);
+
+        //insert by index
+        myStack.add(1, "I am the 2nd element.");
+        assertThat(myStack.size()).isEqualTo(3);
+        assertThat(myStack.get(1)).isEqualTo("I am the 2nd element.");
+        //remove by index
+        myStack.remove(1);
+        assertThat(myStack.size()).isEqualTo(2);
+    }
+
+    @Test
+    void givenADeque_whenAddOrRemoveLastElement_thenTheLastElementCanBeAddedOrRemoved() {
+        Deque<String> myStack = new ArrayDeque<>();
+        myStack.push("I am the 1st element.");
+        myStack.push("I am the 2nd element.");
+        myStack.push("I am the 3rd element.");
+
+        assertThat(myStack.size()).isEqualTo(3);
+
+        //insert element to the bottom of the stack
+        myStack.addLast("I am the NEW element.");
+        assertThat(myStack.size()).isEqualTo(4);
+        assertThat(myStack.peek()).isEqualTo("I am the 3rd element.");
+
+        //remove element from the bottom of the stack
+        String removedStr = myStack.removeLast();
+        assertThat(myStack.size()).isEqualTo(3);
+        assertThat(removedStr).isEqualTo("I am the NEW element.");
+    }
+
+    @Test
+    void givenADeque_whenIterate_thenFromTopToBottom() {
+        Deque<String> myStack = new ArrayDeque<>();
+        myStack.push("I am at the bottom.");
+        myStack.push("I am in the middle.");
+        myStack.push("I am at the top.");
+
+        Iterator<String> it = myStack.iterator();
+
+        assertThat(it).toIterable().containsExactly(
+          "I am at the top.",
+          "I am in the middle.",
+          "I am at the bottom.");
+    }
+}

core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/primitive/PrimitivesListPerformance.java

@@ -8,6 +8,7 @@ import org.openjdk.jmh.runner.options.Options;
 import org.openjdk.jmh.runner.options.OptionsBuilder;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 
@@ -18,12 +19,12 @@ import java.util.concurrent.TimeUnit;
 @State(Scope.Thread)
 public class PrimitivesListPerformance {
 
-    private List<Integer> arrayList = new ArrayList<>();
-    private TIntArrayList tList = new TIntArrayList();
-    private cern.colt.list.IntArrayList coltList = new cern.colt.list.IntArrayList();
-    private IntArrayList fastUtilList = new IntArrayList();
+    private List<Integer> arrayList = new ArrayList<>(Arrays.asList(0, 1, 2, 3, 4, 5, 6, 7, 8, 9));
+    private TIntArrayList tList = new TIntArrayList(new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
+    private cern.colt.list.IntArrayList coltList = new cern.colt.list.IntArrayList(new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
+    private IntArrayList fastUtilList = new IntArrayList(new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
 
-    private int getValue = 10;
+    private int getValue = 4;
 
     @Benchmark
     public boolean addArrayList() {

core-java-modules/core-java-collections-maps-3/README.md

@@ -7,4 +7,6 @@ This module contains articles about Map data structures in Java.
 - [Comparing Two HashMaps in Java](https://www.baeldung.com/java-compare-hashmaps)
 - [The Map.computeIfAbsent() Method](https://www.baeldung.com/java-map-computeifabsent)
 - [Collections.synchronizedMap vs. ConcurrentHashMap](https://www.baeldung.com/java-synchronizedmap-vs-concurrenthashmap)
+- [Java HashMap Load Factor](https://www.baeldung.com/java-hashmap-load-factor)
+- [Converting java.util.Properties to HashMap](https://www.baeldung.com/java-convert-properties-to-hashmap)
 - More articles: [[<-- prev]](/core-java-modules/core-java-collections-maps-2)

core-java-modules/core-java-collections-maps-3/pom.xml

@@ -20,6 +20,11 @@
             <artifactId>jmh-core</artifactId>
             <version>${jmh-core.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>

core-java-modules/core-java-collections-maps-3/src/main/java/com/baeldung/map/propertieshashmap/PropertiesToHashMapConverter.java

@@ -0,0 +1,39 @@
+package com.baeldung.map.propertieshashmap;
+
+import com.google.common.collect.Maps;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import java.util.stream.Collectors;
+
+public class PropertiesToHashMapConverter {
+
+    @SuppressWarnings({"rawtypes", "unchecked"})
+    public static HashMap<String, String> typeCastConvert(Properties prop) {
+        Map step1 = prop;
+        Map<String, String> step2 = (Map<String, String>) step1;
+        return new HashMap<>(step2);
+    }
+
+    public static HashMap<String, String> loopConvert(Properties prop) {
+        HashMap<String, String> retMap = new HashMap<>();
+        for (Map.Entry<Object, Object> entry : prop.entrySet()) {
+            retMap.put(String.valueOf(entry.getKey()), String.valueOf(entry.getValue()));
+        }
+        return retMap;
+    }
+
+    public static HashMap<String, String> streamConvert(Properties prop) {
+        return prop.entrySet().stream().collect(
+                Collectors.toMap(
+                  e -> String.valueOf(e.getKey()),
+                  e -> String.valueOf(e.getValue()),
+                  (prev, next) -> next, HashMap::new
+                ));
+    }
+
+    public static HashMap<String, String> guavaConvert(Properties prop) {
+        return Maps.newHashMap(Maps.fromProperties(prop));
+    }
+}

core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/hashmap/loadfactor/HashMapLoadFactorUnitTest.java

@@ -0,0 +1,49 @@
+package com.baeldung.map.hashmap.loadfactor;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Assert;
+import org.junit.jupiter.api.Test;
+
+public class HashMapLoadFactorUnitTest {
+
+    @Test
+    public void whenCreateMapWithDefaultParam_thenSucces() {
+        Map<String, String> mapWithDefaultParams = new HashMap<>();
+        mapWithDefaultParams.put("1", "one");
+        mapWithDefaultParams.put("2", "two");
+        mapWithDefaultParams.put("3", "three");
+        mapWithDefaultParams.put("4", "four");
+        mapWithDefaultParams.put("5", "five");
+        
+        Assert.assertEquals(5, mapWithDefaultParams.size());
+    }
+
+    @Test
+    public void whenCreateMapWithInitialCapacity_thenSucces() {
+        Map<String, String> mapWithInitialCapacity = new HashMap<>(5);
+        mapWithInitialCapacity.put("1", "one");
+        mapWithInitialCapacity.put("2", "two");
+        mapWithInitialCapacity.put("3", "three");
+        
+        Assert.assertEquals(3, mapWithInitialCapacity.size());
+    }
+
+    @Test
+    public void whenCreateMapWithInitialCapacityAndLF_thenSucces() {
+        Map<String, String> mapWithInitialCapacityAndLF = new HashMap<>(5, 0.5f);
+        mapWithInitialCapacityAndLF.put("1", "one");
+        mapWithInitialCapacityAndLF.put("2", "two");
+        mapWithInitialCapacityAndLF.put("3", "three");
+        mapWithInitialCapacityAndLF.put("4", "four");
+        mapWithInitialCapacityAndLF.put("5", "five");
+        mapWithInitialCapacityAndLF.put("6", "six");
+        mapWithInitialCapacityAndLF.put("7", "seven");
+        mapWithInitialCapacityAndLF.put("8", "eight");
+        mapWithInitialCapacityAndLF.put("9", "nine");
+        mapWithInitialCapacityAndLF.put("10", "ten");
+     
+        Assert.assertEquals(10, mapWithInitialCapacityAndLF.size());
+    }
+}

core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/propertieshashmap/PropertiesToHashMapConverterUnitTest.java

@@ -0,0 +1,192 @@
+package com.baeldung.map.propertieshashmap;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.HashMap;
+import java.util.Properties;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PropertiesToHashMapConverterUnitTest {
+
+    private Properties properties;
+
+    private final static String propertyFileName = "toHashMap.properties";
+
+    @BeforeEach
+    public void setup() throws IOException {
+        properties = new Properties();
+        try (InputStream is = getClass().getClassLoader().getResourceAsStream(propertyFileName)) {
+            if (is != null) {
+                properties.load(is);
+            }
+        }
+    }
+
+    @Test
+    public void havingPropertiesLoaded_whenCheck_thenEquals() {
+        assertEquals(3, properties.size());
+        assertEquals("str_value", properties.get("property1"));
+        assertEquals("123", properties.get("property2"));
+        assertEquals("", properties.get("property3"));
+    }
+
+    @Test
+    public void whenPropertiesModified_thenTypeSafeIssues() {
+        compromiseProperties(properties);
+
+        assertEquals(5, properties.size());
+
+        assertNull(properties.getProperty("property4"));
+        assertNotEquals(String.class, properties.get("property4").getClass());
+        assertEquals(456, properties.get("property4"));
+
+
+        assertNull(properties.getProperty("5"));
+        assertNotEquals(String.class, properties.get(5).getClass());
+        assertEquals(10.11, properties.get(5));
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenTypeCastConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.typeCastConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenTypeCastConvert_thenClassCastException() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.typeCastConvert(properties);
+        assertEquals(5, hMap.size());
+
+        assertThrows(ClassCastException.class, () -> {
+            String s = hMap.get("property4");
+        });
+        assertEquals(Integer.class, ((Object) hMap.get("property4")).getClass());
+
+        assertNull(hMap.get("5"));
+        assertNotNull(hMap.get(5));
+        assertThrows(ClassCastException.class, () -> {
+            String s = hMap.get(5);
+        });
+        assertEquals(Double.class, ((Object) hMap.get(5)).getClass());
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenLoopConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.loopConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenLoopConvert_thenNoClassCastException() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.loopConvert(properties);
+        assertEquals(5, hMap.size());
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("property4");
+        });
+        assertEquals(String.class, hMap.get("property4").getClass());
+        assertEquals("456", hMap.get("property4"));
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("5");
+        });
+        assertEquals("10.11", hMap.get("5"));
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenStreamConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.streamConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenStreamConvert_thenNoClassCastException() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.streamConvert(properties);
+        assertEquals(5, hMap.size());
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("property4");
+        });
+        assertEquals(String.class, hMap.get("property4").getClass());
+        assertEquals("456", hMap.get("property4"));
+
+        assertDoesNotThrow(() -> {
+            String s = hMap.get("5");
+        });
+        assertEquals("10.11", hMap.get("5"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenLoopConvertAndStreamConvert_thenHashMapsSame() {
+        compromiseProperties(properties);
+        HashMap<String, String> hMap1 = PropertiesToHashMapConverter.loopConvert(properties);
+        HashMap<String, String> hMap2 = PropertiesToHashMapConverter.streamConvert(properties);
+
+        assertEquals(hMap2, hMap1);
+    }
+
+    @Test
+    public void havingNonModifiedProperties_whenGuavaConvert_thenNoTypeSafeIssues() {
+        HashMap<String, String> hMap = PropertiesToHashMapConverter.guavaConvert(properties);
+
+        assertEquals(3, hMap.size());
+        assertEquals(String.class, hMap.get("property1").getClass());
+        assertEquals(properties.get("property1"), hMap.get("property1"));
+        assertEquals(String.class, hMap.get("property2").getClass());
+        assertEquals(properties.get("property2"), hMap.get("property2"));
+        assertEquals(String.class, hMap.get("property3").getClass());
+        assertEquals(properties.get("property3"), hMap.get("property3"));
+    }
+
+    @Test
+    public void havingModifiedProperties_whenGuavaConvert_thenUnableToConvertAndThrowException() {
+        compromiseProperties(properties);
+        assertThrows(Exception.class, () -> PropertiesToHashMapConverter.guavaConvert(properties));
+    }
+
+    @Test
+    public void havingModifiedPropertiesWithNoIntegerValue_whenGuavaConvert_thenNullPointerException() {
+        properties.put("property4", 456);
+        assertThrows(NullPointerException.class, () -> PropertiesToHashMapConverter.guavaConvert(properties));
+    }
+
+    @Test
+    public void havingModifiedPropertiesWithNoIntegerKey_whenGuavaConvert_thenClassCastException() {
+        properties.put(5, 10.11);
+        assertThrows(ClassCastException.class, () -> PropertiesToHashMapConverter.guavaConvert(properties));
+    }
+
+
+    private void compromiseProperties(Properties prop) {
+        prop.put("property4", 456);
+        prop.put(5, 10.11);
+    }
+}

core-java-modules/core-java-collections-maps-3/src/test/resources/toHashMap.properties

@@ -0,0 +1,3 @@
+property1=str_value
+property2=123
+property3=

core-java-modules/core-java-concurrency-collections/src/test/java/com/baeldung/java/stream/ThreadPoolInParallelStreamIntegrationTest.java

@@ -21,14 +21,16 @@ public class ThreadPoolInParallelStreamIntegrationTest {
         long lastNum = 1_000_000;
 
         List<Long> aList = LongStream.rangeClosed(firstNum, lastNum).boxed().collect(Collectors.toList());
-
         ForkJoinPool customThreadPool = new ForkJoinPool(4);
-        long actualTotal = customThreadPool
-          .submit(() -> aList.parallelStream()
-            .reduce(0L, Long::sum))
-          .get();
 
-        assertEquals((lastNum + firstNum) * lastNum / 2, actualTotal);
+        try {
+            long actualTotal = customThreadPool
+              .submit(() -> aList.parallelStream().reduce(0L, Long::sum))
+              .get();
+            assertEquals((lastNum + firstNum) * lastNum / 2, actualTotal);
+        } finally {
+            customThreadPool.shutdown();
+        }
     }
 
     @Test

core-java-modules/core-java-io-conversions/src/test/java/com/baeldung/filetoinputstream/JavaXToInputStreamUnitTest.java

@@ -5,12 +5,12 @@ import com.google.common.io.CharSource;
 import com.google.common.io.Files;
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
-import org.apache.commons.io.input.ReaderInputStream;
 import org.junit.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.*;
+import java.nio.charset.StandardCharsets;
 
 public class JavaXToInputStreamUnitTest {
     protected final Logger logger = LoggerFactory.getLogger(getClass());
@@ -28,7 +28,7 @@ public class JavaXToInputStreamUnitTest {
     @Test
     public final void givenUsingGuava_whenConvertingStringToInputStream_thenCorrect() throws IOException {
         final String initialString = "text";
-        final InputStream targetStream = new ReaderInputStream(CharSource.wrap(initialString).openStream());
+        final InputStream targetStream = CharSource.wrap(initialString).asByteSource(StandardCharsets.UTF_8).openStream();
 
         IOUtils.closeQuietly(targetStream);
     }

core-java-modules/core-java-jpms/decoupling-pattern2/consumermodule/pom.xml

@@ -17,7 +17,7 @@
     <dependencies>
         <dependency>
             <groupId>com.baeldung.servicemodule</groupId>
-            <artifactId>servicemodule</artifactId>
+            <artifactId>servicemodule2</artifactId>
             <version>${servicemodule.version}</version>
         </dependency>
         <dependency>
@@ -41,4 +41,4 @@
         <providermodule.version>1.0</providermodule.version>
     </properties>
 
-</project>
+</project>

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

@@ -77,7 +77,6 @@
         <assertj.version>3.6.1</assertj.version>
         <!-- instrumentation -->
         <javaassist.version>3.27.0-GA</javaassist.version>
-        <esapi.version>2.1.0.1</esapi.version>
         <sun.tools.version>1.8.0</sun.tools.version>
         <jol-core.version>0.10</jol-core.version>
         <asm.version>8.0.1</asm.version>

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

@@ -11,4 +11,5 @@ This module contains articles about core features in the Java language
 - [The transient Keyword in Java](https://www.baeldung.com/java-transient-keyword)
 - [How to Access an Iteration Counter in a For Each Loop](https://www.baeldung.com/java-foreach-counter)
 - [Comparing Doubles in Java](https://www.baeldung.com/java-comparing-doubles)
+- [Guide to Implementing the compareTo Method](https://www.baeldung.com/java-compareto)
 - [[<-- Prev]](/core-java-modules/core-java-lang-2)

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

@@ -0,0 +1,5 @@
+## Core Java Lang (Part 4)
+
+This module contains articles about core features in the Java language
+
+- [The Java final Keyword – Impact on Performance](https://www.baeldung.com/java-final-performance)

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

@@ -0,0 +1,47 @@
+<?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>core-java-lang-4</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-lang-4</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <artifactId>core-java-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-lang-4</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <jmh.version>1.28</jmh.version>
+    </properties>
+      
+</project>

core-java-modules/core-java-lang-4/src/main/java/com/baeldung/finalkeyword/BenchmarkRunner.java

@@ -0,0 +1,34 @@
+package com.baeldung.finalkeyword;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+
+import java.util.concurrent.TimeUnit;
+
+public class BenchmarkRunner {
+
+    public static void main(String[] args) throws Exception {
+        org.openjdk.jmh.Main.main(args);
+    }
+
+    @Benchmark
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    @BenchmarkMode(Mode.AverageTime)
+    public static String concatNonFinalStrings() {
+        String x = "x";
+        String y = "y";
+        return x + y;
+    }
+
+    @Benchmark
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    @BenchmarkMode(Mode.AverageTime)
+    public static String concatFinalStrings() {
+        final String x = "x";
+        final String y = "y";
+        return x + y;
+    }
+
+}

core-java-modules/core-java-lang-4/src/main/java/com/baeldung/finalkeyword/ClassVariableFinal.java

@@ -0,0 +1,19 @@
+package com.baeldung.finalkeyword;
+
+import java.io.Console;
+
+public class ClassVariableFinal {
+
+    static final boolean doX = false;
+    static final boolean doY = true;
+
+    public static void main(String[] args) {
+        Console console = System.console();
+        if (doX) {
+            console.writer().println("x");
+        } else if (doY) {
+            console.writer().println("y");
+        }
+    }
+
+}

core-java-modules/core-java-lang-4/src/main/java/com/baeldung/finalkeyword/ClassVariableNonFinal.java

@@ -0,0 +1,19 @@
+package com.baeldung.finalkeyword;
+
+import java.io.Console;
+
+public class ClassVariableNonFinal {
+
+    static boolean doX = false;
+    static boolean doY = true;
+
+    public static void main(String[] args) {
+        Console console = System.console();
+        if (doX) {
+            console.writer().println("x");
+        } else if (doY) {
+            console.writer().println("y");
+        }
+    }
+
+}

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

@@ -4,6 +4,5 @@
 
 ### Relevant articles:
 
-- [Calculate Factorial in Java](https://www.baeldung.com/java-calculate-factorial)
 - [Evaluating a Math Expression in Java](https://www.baeldung.com/java-evaluate-math-expression-string)
 - More articles: [[<-- Prev]](/core-java-modules/core-java-lang-math-2)

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

@@ -8,3 +8,4 @@ This module contains articles about generics in Java
 - [Raw Types in Java](https://www.baeldung.com/raw-types-java)
 - [Super Type Tokens in Java Generics](https://www.baeldung.com/java-super-type-tokens)
 - [Java Warning “unchecked conversion”](https://www.baeldung.com/java-unchecked-conversion)
+- [Java Warning “Unchecked Cast”](https://www.baeldung.com/java-warning-unchecked-cast)

core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/uncheckedcast/UncheckedCast.java

@@ -0,0 +1,26 @@
+package com.baeldung.uncheckedcast;
+
+import java.time.LocalDate;
+import java.time.Month;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
+
+public class UncheckedCast {
+    public static Map getRawMap() {
+        Map rawMap = new HashMap();
+        rawMap.put("date 1", LocalDate.of(2021, Month.FEBRUARY, 10));
+        rawMap.put("date 2", LocalDate.of(1992, Month.AUGUST, 8));
+        rawMap.put("date 3", LocalDate.of(1976, Month.NOVEMBER, 18));
+        return rawMap;
+    }
+
+    public static Map getRawMapWithMixedTypes() {
+        Map rawMap = new HashMap();
+        rawMap.put("date 1", LocalDate.of(2021, Month.FEBRUARY, 10));
+        rawMap.put("date 2", LocalDate.of(1992, Month.AUGUST, 8));
+        rawMap.put("date 3", LocalDate.of(1976, Month.NOVEMBER, 18));
+        rawMap.put("date 4", new Date());
+        return rawMap;
+    }
+}

core-java-modules/core-java-lang-oop-generics/src/test/java/com/baeldung/uncheckedcast/UncheckedCastUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.uncheckedcast;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.time.LocalDate;
+import java.time.Month;
+import java.util.Map;
+
+public class UncheckedCastUnitTest {
+
+    @Test
+    public void givenRawMap_whenCastToTypedMap_shouldHaveCompilerWarning() {
+        Map<String, LocalDate> castFromRawMap = (Map<String, LocalDate>) UncheckedCast.getRawMap();
+        Assert.assertEquals(3, castFromRawMap.size());
+        Assert.assertEquals(castFromRawMap.get("date 2"), LocalDate.of(1992, Month.AUGUST, 8));
+    }
+
+    @Test(expected = ClassCastException.class)
+    public void givenMixTypedRawMap_whenCastToTypedMap_shouldThrowClassCastException() {
+        Map<String, LocalDate> castFromRawMap = (Map<String, LocalDate>) UncheckedCast.getRawMapWithMixedTypes();
+        Assert.assertEquals(4, castFromRawMap.size());
+        Assert.assertTrue(castFromRawMap.get("date 4").isAfter(castFromRawMap.get("date 3")));
+    }
+}

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/classfile/Outer.java

@@ -0,0 +1,131 @@
+package com.baeldung.classfile;
+
+import org.apache.commons.lang3.StringUtils;
+import com.baeldung.classfile.HelloWorld.HelloSomeone;
+
+public class Outer {
+
+    // Static Nested class
+    static class StaticNested {
+        public String message() {
+            return "This is a static Nested Class";
+        }
+    }
+
+    // Non-static Nested class
+    class Nested {
+        public String message() {
+            return "This is a non-static Nested Class";
+        }
+    }
+
+    // Local class
+    public String message() {
+        class Local {
+            private String message() {
+                return "This is a Local Class within a method";
+            }
+        }
+        Local local = new Local();
+        return local.message();
+    }
+
+    // Local class within if clause
+    public String message(String name) {
+        if (StringUtils.isEmpty(name)) {
+            class Local {
+                private String message() {
+                    return "This is a Local Class within if clause";
+                }
+            }
+            Local local = new Local();
+            return local.message();
+        } else
+            return "Welcome to " + name;
+    }
+
+    // Anonymous Inner class extending a class
+    public String greet() {
+        Outer anonymous = new Outer() {
+            public String greet() {
+                return "Running Anonymous Class...";
+            }
+        };
+        return anonymous.greet();
+    }
+
+    // Anonymous inner class implementing an interface
+    public String greet(String name) {
+
+        HelloWorld helloWorld = new HelloWorld() {
+            public String greet(String name) {
+                return "Welcome to " + name;
+            }
+
+        };
+        return helloWorld.greet(name);
+    }
+
+    // Anonymous inner class implementing nested interface
+    public String greetSomeone(String name) {
+
+        HelloSomeone helloSomeOne = new HelloSomeone() {
+            public String greet(String name) {
+                return "Hello " + name;
+            }
+
+        };
+        return helloSomeOne.greet(name);
+    }
+
+    // Nested interface within a class
+    interface HelloOuter {
+        public String hello(String name);
+    }
+
+    // Enum within a class
+    enum Color {
+        RED, GREEN, BLUE;
+    }
+}
+
+interface HelloWorld {
+
+    public String greet(String name);
+
+    // Nested class within an interface
+    class InnerClass {
+        public String greet(String name) {
+            return "Inner class within an interface";
+        }
+    }
+
+    // Nested interface within an interfaces
+    interface HelloSomeone {
+        public String greet(String name);
+    }
+
+    // Enum within an interface
+    enum Directon {
+        NORTH, SOUTH, EAST, WEST;
+    }
+}
+
+enum Level {
+    LOW, MEDIUM, HIGH;
+
+}
+
+enum Foods {
+
+    DRINKS, EATS;
+
+    // Enum within Enum
+    enum DRINKS {
+        APPLE_JUICE, COLA;
+    }
+
+    enum EATS {
+        POTATO, RICE;
+    }
+}

core-java-modules/core-java-lang-oop-types/src/test/java/com/baeldung/classfile/OuterUnitTest.java

@@ -0,0 +1,46 @@
+package com.baeldung.classfile;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
+import com.baeldung.classfile.Outer.Nested;
+
+public class OuterUnitTest {
+
+    @Test
+    public void when_static_nestedClass_then_verifyOutput() {
+        Outer.StaticNested nestedClass = new Outer.StaticNested();
+        assertEquals("This is a static Nested Class", nestedClass.message());
+    }
+
+    @Test
+    public void when_nestedClass_then_verifyOutput() {
+        Outer outer = new Outer();
+        Nested nestedClass = outer.new Nested();
+        assertEquals("This is a non-static Nested Class", nestedClass.message());
+    }
+
+    @Test
+    public void when_localClass_then_verifyOutput() {
+        Outer outer = new Outer();
+        assertEquals("This is a Local Class within a method", outer.message());
+    }
+
+    @Test
+    public void when_localClassInIfClause_then_verifyOutput() {
+        Outer outer = new Outer();
+        assertEquals("Welcome to Baeldung", outer.message("Baeldung"));
+        assertEquals("This is a Local Class within if clause", outer.message(""));
+    }
+
+    @Test
+    public void when_anonymousClass_then_verifyOutput() {
+        Outer outer = new Outer();
+        assertEquals("Running Anonymous Class...", outer.greet());
+    }
+
+    @Test
+    public void when_anonymousClassHelloWorld_then_verifyOutput() {
+        Outer outer = new Outer();
+        assertEquals("Welcome to Baeldung", outer.greet("Baeldung"));
+    }
+}

core-java-modules/core-java-nio-2/pom.xml

@@ -14,5 +14,12 @@
         <version>0.0.1-SNAPSHOT</version>
         <relativePath>../</relativePath>
     </parent>
-
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>3.6.1</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
 </project>

core-java-modules/core-java-nio-2/src/test/java/com/baeldung/selector/SelectorManualTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.selector;
+
+import org.junit.Test;
+import java.io.IOException;
+import java.nio.channels.Pipe;
+import java.nio.channels.SelectableChannel;
+import java.nio.channels.Selector;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import static java.nio.channels.SelectionKey.OP_READ;
+
+public class SelectorManualTest {
+
+    @Test
+    public void whenWakeUpCalledOnSelector_thenBlockedThreadReturns() throws IOException, InterruptedException {
+        Pipe pipe = Pipe.open();
+
+        Selector selector = Selector.open();
+        SelectableChannel channel = pipe.source();
+        channel.configureBlocking(false);
+        channel.register(selector, OP_READ);
+
+        List<String> invocationStepsTracker = Collections.synchronizedList(new ArrayList<>());
+
+        CountDownLatch latch = new CountDownLatch(1);
+
+        Thread thread = new Thread(() -> {
+            invocationStepsTracker.add(">> Count down");
+            latch.countDown();
+            try {
+                invocationStepsTracker.add(">> Start select");
+                selector.select();
+                invocationStepsTracker.add(">> End select");
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        });
+
+        invocationStepsTracker.add(">> Start await");
+        thread.start();
+        latch.await();
+        invocationStepsTracker.add(">> End await");
+
+        invocationStepsTracker.add(">> Wakeup thread");
+
+        selector.wakeup();
+        channel.close();
+
+        assertThat(invocationStepsTracker)
+          .containsExactly(
+            ">> Start await",
+            ">> Count down",
+            ">> Start select",
+            ">> End await",
+            ">> Wakeup thread",
+            ">> End select"
+          );
+    }
+}

core-java-modules/core-java-reflection-2/README.md

@@ -4,3 +4,4 @@
 - [Set Field Value With Reflection](https://www.baeldung.com/java-set-private-field-value)
 - [Checking If a Method is Static Using Reflection in Java](https://www.baeldung.com/java-check-method-is-static)
 - [Checking if a Java Class is ‘abstract’ Using Reflection](https://www.baeldung.com/java-reflection-is-class-abstract)
+- [Invoking a Private Method in Java](https://www.baeldung.com/java-call-private-method)

core-java-modules/core-java-reflection-2/pom.xml

@@ -14,6 +14,15 @@
         <relativePath>../</relativePath>
     </parent>
     
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-test</artifactId>
+            <version>${spring.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+    
     <build>
         <finalName>core-java-reflection-2</finalName>
         <resources>
@@ -40,5 +49,6 @@
         <maven-compiler-plugin.version>3.8.0</maven-compiler-plugin.version>
         <source.version>1.8</source.version>
         <target.version>1.8</target.version>
+        <spring.version>5.3.4</spring.version>
     </properties>
 </project>

core-java-modules/core-java-reflection-2/src/main/java/com/baeldung/reflection/access/privatemethods/LongArrayUtil.java

@@ -0,0 +1,18 @@
+package com.baeldung.reflection.access.privatemethods;
+
+public class LongArrayUtil {
+
+    public static int indexOf(long[] array, long target) {
+        return indexOf(array, target, 0, array.length);
+    }
+
+    private static int indexOf(long[] array, long target, int start, int end) {
+        for (int i = start; i < end; i++) {
+            if (array[i] == target) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+}

core-java-modules/core-java-reflection-2/src/test/java/com/baeldung/reflection/access/privatemethods/InvokePrivateMethodsUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.reflection.access.privatemethods;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.test.util.ReflectionTestUtils;
+
+import java.lang.reflect.Method;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class InvokePrivateMethodsUnitTest {
+
+    private final long[] someLongArray = new long[] { 1L, 2L, 1L, 4L, 2L };
+
+    @Test
+    void whenSearchingForLongValueInSubsequenceUsingReflection_thenTheCorrectIndexOfTheValueIsReturned() throws Exception {
+        Method indexOfMethod = LongArrayUtil.class.getDeclaredMethod("indexOf", long[].class, long.class, int.class, int.class);
+        indexOfMethod.setAccessible(true);
+
+        assertEquals(2, indexOfMethod.invoke(LongArrayUtil.class, someLongArray, 1L, 1, someLongArray.length), "The index should be 2.");
+    }
+
+    @Test
+    void whenSearchingForLongValueInSubsequenceUsingSpring_thenTheCorrectIndexOfTheValueIsReturned() throws Exception {
+        int indexOfSearchTarget = ReflectionTestUtils.invokeMethod(LongArrayUtil.class, "indexOf", someLongArray, 1L, 1, someLongArray.length);
+        assertEquals(2, indexOfSearchTarget, "The index should be 2.");
+    }
+
+}

core-java-modules/core-java-security-2/README.md

@@ -15,4 +15,5 @@ This module contains articles about core Java Security
 - [Security Context Basics: User, Subject and Principal](https://www.baeldung.com/security-context-basics)
 - [Java AES Encryption and Decryption](https://www.baeldung.com/java-aes-encryption-decryption)
 - [InvalidAlgorithmParameterException: Wrong IV Length](https://www.baeldung.com/java-invalidalgorithmparameter-exception)
+- [The java.security.egd JVM Option](https://www.baeldung.com/java-security-egd)
 - More articles: [[<-- prev]](/core-java-modules/core-java-security)

core-java-modules/pom.xml

@@ -82,6 +82,7 @@
         <module>core-java-lang</module>
         <module>core-java-lang-2</module>
         <module>core-java-lang-3</module>
+        <module>core-java-lang-4</module>
         <module>core-java-lang-math</module>
         <module>core-java-lang-math-2</module>
         <module>core-java-lang-math-3</module>

data-structures/src/main/java/com/baeldung/circularbuffer/CircularBuffer.java

@@ -10,10 +10,8 @@ public class CircularBuffer<E> {
 
     @SuppressWarnings("unchecked")
     public CircularBuffer(int capacity) {
-
         this.capacity = (capacity < 1) ? DEFAULT_CAPACITY : capacity;
-        this.data = (E[]) new Object[capacity];
-
+        this.data = (E[]) new Object[this.capacity];
         this.readSequence = 0;
         this.writeSequence = -1;
     }

data-structures/src/main/java/com/baeldung/circularlinkedlist/CircularLinkedList.java

@@ -5,7 +5,7 @@ import org.slf4j.LoggerFactory;
 
 public class CircularLinkedList {
 
-    final Logger LOGGER = LoggerFactory.getLogger(CircularLinkedList.class);
+    final Logger logger = LoggerFactory.getLogger(CircularLinkedList.class);
 
     private Node head = null;
     private Node tail = null;
@@ -42,24 +42,29 @@ public class CircularLinkedList {
     }
 
     public void deleteNode(int valueToDelete) {
-
         Node currentNode = head;
-
-        if (head != null) {
-            if (currentNode.value == valueToDelete) {
-                head = head.nextNode;
-                tail.nextNode = head;
-            } else {
-                do {
-                    Node nextNode = currentNode.nextNode;
-                    if (nextNode.value == valueToDelete) {
-                        currentNode.nextNode = nextNode.nextNode;
-                        break;
-                    }
-                    currentNode = currentNode.nextNode;
-                } while (currentNode != head);
-            }
+        if (head == null) {
+            return;
         }
+        do {
+            Node nextNode = currentNode.nextNode;
+            if (nextNode.value == valueToDelete) {
+                if (tail == head) {
+                    head = null;
+                    tail = null;
+                } else {
+                    currentNode.nextNode = nextNode.nextNode;
+                    if (head == nextNode) {
+                        head = head.nextNode;
+                    }
+                    if (tail == nextNode) {
+                        tail = currentNode;
+                    }
+                }
+                break;
+            }
+            currentNode = nextNode;
+        } while (currentNode != head);
     }
 
     public void traverseList() {
@@ -68,7 +73,7 @@ public class CircularLinkedList {
 
         if (head != null) {
             do {
-                LOGGER.info(currentNode.value + " ");
+                logger.info(currentNode.value + " ");
                 currentNode = currentNode.nextNode;
             } while (currentNode != head);
         }

data-structures/src/test/java/com/baeldung/circularlinkedlist/CircularLinkedListUnitTest.java

@@ -1,10 +1,10 @@
 package com.baeldung.circularlinkedlist;
 
+import org.junit.Test;
+
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
-import org.junit.Test;
-
 public class CircularLinkedListUnitTest {
 
     @Test
@@ -23,7 +23,7 @@ public class CircularLinkedListUnitTest {
     }
 
     @Test
-    public void givenACircularLinkedList_WhenDeletingElements_ThenListDoesNotContainThoseElements() {
+    public void givenACircularLinkedList_WhenDeletingInOrderHeadMiddleTail_ThenListDoesNotContainThoseElements() {
         CircularLinkedList cll = createCircularLinkedList();
 
         assertTrue(cll.containsNode(13));
@@ -39,6 +39,32 @@ public class CircularLinkedListUnitTest {
         assertFalse(cll.containsNode(46));
     }
 
+    @Test
+    public void givenACircularLinkedList_WhenDeletingInOrderTailMiddleHead_ThenListDoesNotContainThoseElements() {
+        CircularLinkedList cll = createCircularLinkedList();
+
+        assertTrue(cll.containsNode(46));
+        cll.deleteNode(46);
+        assertFalse(cll.containsNode(46));
+
+        assertTrue(cll.containsNode(1));
+        cll.deleteNode(1);
+        assertFalse(cll.containsNode(1));
+
+        assertTrue(cll.containsNode(13));
+        cll.deleteNode(13);
+        assertFalse(cll.containsNode(13));
+    }
+
+    @Test
+    public void givenACircularLinkedListWithOneNode_WhenDeletingElement_ThenListDoesNotContainTheElement() {
+        CircularLinkedList cll = new CircularLinkedList();
+        cll.addNode(1);
+        cll.deleteNode(1);
+        assertFalse(cll.containsNode(1));
+    }
+
+
     private CircularLinkedList createCircularLinkedList() {
         CircularLinkedList cll = new CircularLinkedList();
 

docker/README.md

@@ -3,3 +3,4 @@
 - [Introduction to Docker Compose](https://www.baeldung.com/docker-compose)
 - [Reusing Docker Layers with Spring Boot](https://www.baeldung.com/docker-layers-spring-boot)
 - [Running Spring Boot with PostgreSQL in Docker Compose](https://www.baeldung.com/spring-boot-postgresql-docker)
+- [How To Configure Java Heap Size Inside a Docker Container](https://www.baeldung.com/ops/docker-jvm-heap-size)

docker/heap-sizing/Dockerfile

@@ -0,0 +1,4 @@
+FROM openjdk:8u92-jdk-alpine
+COPY /src /src/
+RUN mkdir /app && ls /src && javac /src/main/java/com/baeldung/docker/heapsizing/PrintXmxXms.java -d /app
+CMD java -version && java $JAVA_OPTS -cp /app com.baeldung.docker.heapsizing.PrintXmxXms

docker/heap-sizing/pom.xml

@@ -0,0 +1,61 @@
+<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.4.2</version>
+        <relativePath/> <!-- lookup parent from repository -->
+    </parent>
+    <groupId>com.baeldung.docker</groupId>
+    <artifactId>heap-sizing</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>heap-sizing</name>
+    <description>Demo project for Spring Boot</description>
+    <properties>
+        <java.version>11</java.version>
+    </properties>
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-webflux</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.projectreactor</groupId>
+            <artifactId>reactor-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+                <configuration>
+                    <image>
+                        <name>heapsizing-demo</name>
+                    </image>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>com.google.cloud.tools</groupId>
+                <artifactId>jib-maven-plugin</artifactId>
+                <version>2.7.1</version>
+
+                <configuration>
+                    <to>
+                        <image>heapsizing-demo-jib</image>
+                    </to>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

docker/heap-sizing/src/main/java/com/baeldung/docker/heapsizing/HeapSizingApplication.java

@@ -0,0 +1,19 @@
+package com.baeldung.docker.heapsizing;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+import java.util.logging.Logger;
+
+import static com.baeldung.docker.heapsizing.PrintXmxXms.logMemory;
+
+@SpringBootApplication
+public class HeapSizingApplication {
+    private static final Logger logger = Logger.getLogger(HeapSizingApplication.class.getName());
+
+    public static void main(String[] args) {
+        SpringApplication.run(HeapSizingApplication.class, args);
+        logMemory(logger);
+    }
+
+}

docker/heap-sizing/src/main/java/com/baeldung/docker/heapsizing/PrintXmxXms.java

@@ -0,0 +1,36 @@
+package com.baeldung.docker.heapsizing;
+
+import java.lang.management.ManagementFactory;
+import java.lang.management.MemoryMXBean;
+import java.lang.management.MemoryPoolMXBean;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class PrintXmxXms {
+
+    private static final Logger logger = Logger.getLogger(PrintXmxXms.class.getName());
+
+    public static void main(String[] args) {
+        logMemory(logger);
+    }
+
+    /**
+     * We're reusing this method in HeapSizingApplication, therefore this method was extracted
+     * to avoid repetition.
+     */
+    static void logMemory(Logger logger) {
+        float mb = 1024f * 1024f;
+        MemoryMXBean memoryBean = ManagementFactory.getMemoryMXBean();
+
+        // xmx controls the maximum size of the memory allocation pool,
+        // which includes the heap, the garbage collector's survivor space, and other pools.
+        float xmx = memoryBean.getHeapMemoryUsage().getMax() / mb;
+        float xms = memoryBean.getHeapMemoryUsage().getInit() / mb;
+        logger.log(Level.INFO, "Initial Memory (xms) : {0}mb", xms);
+        logger.log(Level.INFO, "Max Memory (xmx) : {0}mb", xmx);
+
+        for (MemoryPoolMXBean mp : ManagementFactory.getMemoryPoolMXBeans()) {
+            logger.log(Level.INFO, "Pool: {0} (type {1}) = {2}", new Object[]{ mp.getName(), mp.getType(), mp.getUsage().getMax() / mb });
+        }
+    }
+}

guest/core-kotlin/README.md

@@ -1,3 +1,3 @@
 ### Relevant Articles:
 
-- [Kotlin vs Java](https://www.baeldung.com/kotlin/kotlin-vs-java)
+- [Kotlin vs Java](https://www.baeldung.com/kotlin/vs-java)

jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/bidirection/ItemWithRef.java

@@ -1,12 +1,12 @@
 package com.baeldung.jackson.bidirection;
 
-import com.fasterxml.jackson.annotation.JsonManagedReference;
+import com.fasterxml.jackson.annotation.JsonBackReference;
 
 public class ItemWithRef {
     public int id;
     public String itemName;
 
-    @JsonManagedReference
+    @JsonBackReference
     public UserWithRef owner;
 
     public ItemWithRef() {

jackson-modules/jackson-annotations/src/main/java/com/baeldung/jackson/bidirection/UserWithRef.java

@@ -3,13 +3,13 @@ package com.baeldung.jackson.bidirection;
 import java.util.ArrayList;
 import java.util.List;
 
-import com.fasterxml.jackson.annotation.JsonBackReference;
+import com.fasterxml.jackson.annotation.JsonManagedReference;
 
 public class UserWithRef {
     public int id;
     public String name;
 
-    @JsonBackReference
+    @JsonManagedReference
     public List<ItemWithRef> userItems;
 
     public UserWithRef() {
@@ -19,7 +19,7 @@ public class UserWithRef {
     public UserWithRef(final int id, final String name) {
         this.id = id;
         this.name = name;
-        userItems = new ArrayList<ItemWithRef>();
+        userItems = new ArrayList<>();
     }
 
     public void addItem(final ItemWithRef item) {

jackson-modules/jackson-annotations/src/test/java/com/baeldung/jackson/bidirection/JacksonBidirectionRelationUnitTest.java

@@ -1,7 +1,9 @@
 package com.baeldung.jackson.bidirection;
 
 import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
+import static org.hamcrest.Matchers.nullValue;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
 
@@ -16,7 +18,7 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 
 public class JacksonBidirectionRelationUnitTest {
 
-    @Test(expected = JsonMappingException.class)
+    @Test (expected = JsonMappingException.class)
     public void givenBidirectionRelation_whenSerializing_thenException() throws JsonProcessingException {
         final User user = new User(1, "John");
         final Item item = new Item(2, "book", user);
@@ -26,16 +28,39 @@ public class JacksonBidirectionRelationUnitTest {
     }
 
     @Test
-    public void givenBidirectionRelation_whenUsingJacksonReferenceAnnotation_thenCorrect() throws JsonProcessingException {
+    public void givenBidirectionRelation_whenUsingJacksonReferenceAnnotationWithSerialization_thenCorrect() throws JsonProcessingException {
         final UserWithRef user = new UserWithRef(1, "John");
         final ItemWithRef item = new ItemWithRef(2, "book", user);
         user.addItem(item);
 
-        final String result = new ObjectMapper().writeValueAsString(item);
+        final String itemJson = new ObjectMapper().writeValueAsString(item);
+        final String userJson = new ObjectMapper().writeValueAsString(user);
 
-        assertThat(result, containsString("book"));
-        assertThat(result, containsString("John"));
-        assertThat(result, not(containsString("userItems")));
+        assertThat(itemJson, containsString("book"));
+        assertThat(itemJson, not(containsString("John")));
+
+        assertThat(userJson, containsString("John"));
+        assertThat(userJson, containsString("userItems"));
+        assertThat(userJson, containsString("book"));
+    }
+
+    @Test
+    public void givenBidirectionRelation_whenUsingJacksonReferenceAnnotationWithDeserialization_thenCorrect() throws JsonProcessingException {
+        final UserWithRef user = new UserWithRef(1, "John");
+        final ItemWithRef item = new ItemWithRef(2, "book", user);
+        user.addItem(item);
+
+        final String itemJson = new ObjectMapper().writeValueAsString(item);
+        final String userJson = new ObjectMapper().writeValueAsString(user);
+
+        final ItemWithRef itemRead = new ObjectMapper().readValue(itemJson, ItemWithRef.class);
+        final UserWithRef userRead = new ObjectMapper().readValue(userJson, UserWithRef.class);
+
+        assertThat(itemRead.itemName, is("book"));
+        assertThat(itemRead.owner, nullValue());
+
+        assertThat(userRead.name, is("John"));
+        assertThat(userRead.userItems.get(0).itemName, is("book"));
     }
 
     @Test

java-collections-maps-3/README.md

@@ -3,3 +3,4 @@
 - [Java Map With Case-Insensitive Keys](https://www.baeldung.com/java-map-with-case-insensitive-keys)
 - [Using a Byte Array as Map Key in Java](https://www.baeldung.com/java-map-key-byte-array)
 - [Using the Map.Entry Java Class](https://www.baeldung.com/java-map-entry)
+- [Optimizing HashMap’s Performance](https://www.baeldung.com/java-hashmap-optimize-performance)

java-collections-maps-3/src/main/java/com/baeldung/map/hashing/Member.java

@@ -0,0 +1,6 @@
+package com.baeldung.map.hashing;
+
+class Member {
+    Integer id;
+    String name;
+}

java-collections-maps-3/src/main/java/com/baeldung/map/hashing/MemberWithBadHashing.java

@@ -0,0 +1,8 @@
+package com.baeldung.map.hashing;
+
+public class MemberWithBadHashing extends Member {
+    @Override
+    public int hashCode() {
+        return name.hashCode();
+    }
+}

java-collections-maps-3/src/main/java/com/baeldung/map/hashing/MemberWithGuavaHashing.java

@@ -0,0 +1,18 @@
+package com.baeldung.map.hashing;
+
+import com.google.common.base.Charsets;
+import com.google.common.hash.HashFunction;
+import com.google.common.hash.Hashing;
+
+public class MemberWithGuavaHashing extends Member {
+    @Override
+    public int hashCode() {
+        HashFunction hashFunction = Hashing.murmur3_32();
+        return hashFunction.newHasher()
+                .putInt(id)
+                .putString(name, Charsets.UTF_8)
+                .hash().hashCode();
+    }
+
+
+}

java-collections-maps-3/src/main/java/com/baeldung/map/hashing/MemberWithId.java

@@ -0,0 +1,18 @@
+package com.baeldung.map.hashing;
+
+public class MemberWithId extends Member {
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        MemberWithId that = (MemberWithId) o;
+
+        return id.equals(that.id);
+    }
+
+    @Override
+    public int hashCode() {
+        return id;
+    }
+}

java-collections-maps-3/src/main/java/com/baeldung/map/hashing/MemberWithIdAndName.java

@@ -0,0 +1,23 @@
+package com.baeldung.map.hashing;
+
+import java.util.Objects;
+
+public class MemberWithIdAndName extends Member {
+    public static final int PRIME = 31;
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        MemberWithObjects that = (MemberWithObjects) o;
+        return Objects.equals(id, that.id) &&
+                Objects.equals(name, that.name);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = id.hashCode();
+        result = PRIME * result + (name == null ? 0  : name.hashCode());
+        return result;
+    }
+}

java-collections-maps-3/src/main/java/com/baeldung/map/hashing/MemberWithObjects.java

@@ -0,0 +1,19 @@
+package com.baeldung.map.hashing;
+
+import java.util.Objects;
+
+public class MemberWithObjects extends Member {
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        MemberWithObjects that = (MemberWithObjects) o;
+        return Objects.equals(id, that.id) &&
+                Objects.equals(name, that.name);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, name);
+    }
+}

java-collections-maps-3/src/test/java/com/baeldung/map/hashing/HashingUnitTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.map.hashing;
+
+import com.google.common.base.Stopwatch;
+import org.junit.jupiter.api.Test;
+
+import java.time.Duration;
+import java.util.HashMap;
+import java.util.SplittableRandom;
+import java.util.function.Supplier;
+
+public class HashingUnitTest {
+
+    public static final int SAMPLES = 1000000;
+    private SplittableRandom random = new SplittableRandom();
+
+    private String[] names = {"John", "Adam", "Suzie"};
+
+    @Test
+    void givenPrimitiveByteArrayKey_whenRetrievingFromMap_shouldRetrieveDifferentObjects() {
+        // bad hashing example is prohibitively slow for bigger samples
+//        Duration[] badHashing = testDuration(MemberWithBadHashing::new);
+        Duration[] withId = testDuration(MemberWithId::new);
+        Duration[] withObjects = testDuration(MemberWithObjects::new);
+        Duration[] withIdAndName = testDuration(MemberWithIdAndName::new);
+
+//        System.out.println("Inserting with bad hashing:");
+//        System.out.println(badHashing[0]);
+//        System.out.println("Getting with bad hashing:");
+//        System.out.println(badHashing[1]);
+
+        System.out.println("Inserting with id hashing:");
+        System.out.println(withId[0]);
+        System.out.println("Getting with id hashing:");
+        System.out.println(withId[1]);
+
+        System.out.println("Inserting with id and name hashing:");
+        System.out.println(withIdAndName[0]);
+        System.out.println("Getting with id and name hashing:");
+        System.out.println(withIdAndName[1]);
+
+        System.out.println("Inserting with Objects hashing:");
+        System.out.println(withObjects[0]);
+        System.out.println("Getting with Objects hashing:");
+        System.out.println(withObjects[1]);
+    }
+
+    private String randomName() {
+        return names[random.nextInt(2)];
+    }
+
+    private <T extends Member> Duration[] testDuration(Supplier<T> factory) {
+        HashMap<T, String> map = new HashMap<>();
+        Stopwatch stopwatch = Stopwatch.createUnstarted();
+
+        stopwatch.start();
+        for(int i = 0; i < SAMPLES; i++) {
+            T member = factory.get();
+            member.id = i;
+            member.name = randomName();
+            map.put(member, member.name);
+        }
+        stopwatch.stop();
+        Duration elapsedInserting = stopwatch.elapsed();
+        stopwatch.reset();
+
+        stopwatch.start();
+        for (T key : map.keySet()) {
+            map.get(key);
+        }
+        stopwatch.stop();
+        Duration elapsedGetting = stopwatch.elapsed();
+        stopwatch.reset();
+
+        return new Duration[]{elapsedInserting, elapsedGetting};
+    }
+}

java-rmi/src/test/java/com/baeldung/rmi/JavaRMIIntegrationTest.java

@@ -20,7 +20,7 @@ public class JavaRMIIntegrationTest {
 			MessengerServiceImpl server = new MessengerServiceImpl();
 			server.createStubAndBind();
 		} catch (RemoteException e) {
-			fail("Exception Occurred");
+			fail("Exception Occurred: " + e);
 		}
 	}
 	
@@ -34,11 +34,9 @@ public class JavaRMIIntegrationTest {
 			
 			String expectedMessage = "Server Message";			
 			assertEquals(responseMessage, expectedMessage);
-		} catch (RemoteException e) {
-			fail("Exception Occurred");
-		} catch (NotBoundException nb) {
-			fail("Exception Occurred");
-		}
+		} catch (RemoteException | NotBoundException e) {
+			fail("Exception Occurred: " + e);
+		};
 	}
 	
 }

jjwt/README.md

@@ -47,3 +47,4 @@ Available commands (assumes httpie - https://github.com/jkbrzt/httpie):
 ## Relevant articles:
 
 - [Supercharge Java Authentication with JSON Web Tokens (JWTs)](https://www.baeldung.com/java-json-web-tokens-jjwt)
+- [Decode a JWT Token in Java](https://www.baeldung.com/java-jwt-token-decode)

jjwt/pom.xml

@@ -41,6 +41,12 @@
             <artifactId>jjwt</artifactId>
             <version>${jjwt.version}</version>
         </dependency>
+
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <properties>

jjwt/src/main/java/io/jsonwebtoken/jjwtfun/util/JWTDecoderUtil.java

@@ -0,0 +1,46 @@
+package io.jsonwebtoken.jjwtfun.util;
+
+import io.jsonwebtoken.SignatureAlgorithm;
+import io.jsonwebtoken.impl.crypto.DefaultJwtSignatureValidator;
+
+import javax.crypto.spec.SecretKeySpec;
+import java.util.Base64;
+
+import static io.jsonwebtoken.SignatureAlgorithm.HS256;
+
+public class JWTDecoderUtil {
+
+    public static String decodeJWTToken(String token) {
+        Base64.Decoder decoder = Base64.getDecoder();
+
+        String[] chunks = token.split("\\.");
+
+        String header = new String(decoder.decode(chunks[0]));
+        String payload = new String(decoder.decode(chunks[1]));
+
+        return header + " " + payload;
+    }
+
+    public static String decodeJWTToken(String token, String secretKey) throws Exception {
+        Base64.Decoder decoder = Base64.getDecoder();
+
+        String[] chunks = token.split("\\.");
+
+        String header = new String(decoder.decode(chunks[0]));
+        String payload = new String(decoder.decode(chunks[1]));
+
+        String tokenWithoutSignature = chunks[0] + "." + chunks[1];
+        String signature = chunks[2];
+
+        SignatureAlgorithm sa = HS256;
+        SecretKeySpec secretKeySpec = new SecretKeySpec(secretKey.getBytes(), sa.getJcaName());
+
+        DefaultJwtSignatureValidator validator = new DefaultJwtSignatureValidator(sa, secretKeySpec);
+
+        if (!validator.isValid(tokenWithoutSignature, signature)) {
+            throw new Exception("Could not verify JWT token integrity!");
+        }
+
+        return header + " " + payload;
+    }
+}

jjwt/src/test/java/io/jsonwebtoken/jjwtfun/util/JWTDecoderUtilUnitTest.java

@@ -0,0 +1,32 @@
+package io.jsonwebtoken.jjwtfun.util;
+
+import io.jsonwebtoken.SignatureAlgorithm;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class JWTDecoderUtilUnitTest {
+
+    private final static String SIMPLE_TOKEN = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkJhZWxkdW5nIFVzZXIiLCJpYXQiOjE1MTYyMzkwMjJ9";
+    private final static String SIGNED_TOKEN = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkJhZWxkdW5nIFVzZXIiLCJpYXQiOjE1MTYyMzkwMjJ9.qH7Zj_m3kY69kxhaQXTa-ivIpytKXXjZc1ZSmapZnGE";
+
+    @Test
+    void givenSimpleToken_whenDecoding_thenStringOfHeaderPayloadAreReturned() {
+        assertThat(JWTDecoderUtil.decodeJWTToken(SIMPLE_TOKEN))
+          .contains(SignatureAlgorithm.HS256.getValue());
+    }
+
+    @Test
+    void givenSignedToken_whenDecodingWithInvalidSecret_thenIntegrityIsNotValidated() {
+        assertThatThrownBy(() -> JWTDecoderUtil.decodeJWTToken(SIGNED_TOKEN, "BAD_SECRET"))
+          .hasMessage("Could not verify JWT token integrity!");
+    }
+
+    @Test
+    void givenSignedToken_whenDecodingWithValidSecret_thenIntegrityIsValidated() throws Exception {
+        assertThat(JWTDecoderUtil.decodeJWTToken(SIGNED_TOKEN, "MySecretKey"))
+          .contains("Baeldung User");
+    }
+}

jmeter/README.md

@@ -7,7 +7,7 @@ It contains the code of a simple API for some CRUD operations built using Spring
 
 - Maven
 - JDK 8
-- MongoDB
+- MongoDB (Note: for the Write Extracted Data to a File Using JMeter example MongoDB is not required)
 
 ### Running
 
@@ -36,6 +36,14 @@ Or create a new one via a POST:
 $ curl -X POST -H "Content-Type:application/json" -d '{ "firstName" : "Dassi", "lastName" : "Orleando", "phoneNumber": "+237 545454545", "email": "mymail@yahoo.fr" }' localhost:8080/students
 ```
 
+### Available UUID API
+
+You can view the test response using curl:
+
+```bash
+$ curl localhost:8080/api/uuid
+```
+
 Now with default configurations it will be available at: [http://localhost:8080](http://localhost:8080)
 
 Enjoy it :)
@@ -44,3 +52,4 @@ Enjoy it :)
 
 - [Intro to Performance Testing using JMeter](https://www.baeldung.com/jmeter)
 - [Configure Jenkins to Run and Show JMeter Tests](https://www.baeldung.com/jenkins-and-jmeter)
+- [Write Extracted Data to a File Using JMeter](https://www.baeldung.com/jmeter-write-to-file)

jmeter/src/main/java/com/baeldung/controller/RetrieveUuidController.java

@@ -0,0 +1,18 @@
+package com.baeldung.controller;
+
+import com.baeldung.model.Response;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.UUID;
+
+import static java.lang.String.format;
+
+@RestController
+public class RetrieveUuidController {
+
+    @GetMapping("/api/uuid")
+    public Response uuid() {
+        return new Response(format("Test message... %s.", UUID.randomUUID()));
+    }
+}

jmeter/src/main/java/com/baeldung/model/Response.java

@@ -0,0 +1,40 @@
+package com.baeldung.model;
+
+import java.time.Instant;
+import java.util.UUID;
+
+public class Response {
+    private Instant timestamp;
+    private UUID uuid;
+    private String message;
+
+    public Response(String message) {
+        this.timestamp = Instant.now();
+        this.uuid = UUID.randomUUID();
+        this.message = message;
+    }
+
+    public Instant getTimestamp() {
+        return timestamp;
+    }
+
+    public void setTimestamp(Instant timestamp) {
+        this.timestamp = timestamp;
+    }
+
+    public UUID getUuid() {
+        return uuid;
+    }
+
+    public void setUuid(UUID uuid) {
+        this.uuid = uuid;
+    }
+
+    public String getMessage() {
+        return message;
+    }
+
+    public void setMessage(String message) {
+        this.message = message;
+    }
+}

jmeter/src/main/resources/FileExtractionExample.jmx

@@ -0,0 +1,124 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<jmeterTestPlan version="1.2" properties="5.0" jmeter="5.4.1">
+  <hashTree>
+    <TestPlan guiclass="TestPlanGui" testclass="TestPlan" testname="Test Plan" enabled="true">
+      <stringProp name="TestPlan.comments">To run this test plan you must also be running the Spring application &quot;JmeterApplication&quot; That can be found in this directory</stringProp>
+      <boolProp name="TestPlan.functional_mode">false</boolProp>
+      <boolProp name="TestPlan.tearDown_on_shutdown">true</boolProp>
+      <boolProp name="TestPlan.serialize_threadgroups">false</boolProp>
+      <elementProp name="TestPlan.user_defined_variables" elementType="Arguments" guiclass="ArgumentsPanel" testclass="Arguments" testname="User Defined Variables" enabled="true">
+        <collectionProp name="Arguments.arguments"/>
+      </elementProp>
+      <stringProp name="TestPlan.user_define_classpath"></stringProp>
+    </TestPlan>
+    <hashTree>
+      <ThreadGroup guiclass="ThreadGroupGui" testclass="ThreadGroup" testname="Thread Group" enabled="true">
+        <stringProp name="ThreadGroup.on_sample_error">continue</stringProp>
+        <elementProp name="ThreadGroup.main_controller" elementType="LoopController" guiclass="LoopControlPanel" testclass="LoopController" testname="Loop Controller" enabled="true">
+          <boolProp name="LoopController.continue_forever">false</boolProp>
+          <stringProp name="LoopController.loops">1</stringProp>
+        </elementProp>
+        <stringProp name="ThreadGroup.num_threads">1</stringProp>
+        <stringProp name="ThreadGroup.ramp_time">1</stringProp>
+        <boolProp name="ThreadGroup.scheduler">false</boolProp>
+        <stringProp name="ThreadGroup.duration"></stringProp>
+        <stringProp name="ThreadGroup.delay"></stringProp>
+        <boolProp name="ThreadGroup.same_user_on_next_iteration">true</boolProp>
+      </ThreadGroup>
+      <hashTree>
+        <HTTPSamplerProxy guiclass="HttpTestSampleGui" testclass="HTTPSamplerProxy" testname="Call GET Test endpoint " enabled="true">
+          <elementProp name="HTTPsampler.Arguments" elementType="Arguments" guiclass="HTTPArgumentsPanel" testclass="Arguments" testname="User Defined Variables" enabled="true">
+            <collectionProp name="Arguments.arguments"/>
+          </elementProp>
+          <stringProp name="HTTPSampler.domain">localhost</stringProp>
+          <stringProp name="HTTPSampler.port">8080</stringProp>
+          <stringProp name="HTTPSampler.protocol">http</stringProp>
+          <stringProp name="HTTPSampler.contentEncoding"></stringProp>
+          <stringProp name="HTTPSampler.path">/api/test</stringProp>
+          <stringProp name="HTTPSampler.method">GET</stringProp>
+          <boolProp name="HTTPSampler.follow_redirects">true</boolProp>
+          <boolProp name="HTTPSampler.auto_redirects">false</boolProp>
+          <boolProp name="HTTPSampler.use_keepalive">true</boolProp>
+          <boolProp name="HTTPSampler.DO_MULTIPART_POST">false</boolProp>
+          <stringProp name="HTTPSampler.embedded_url_re"></stringProp>
+          <stringProp name="HTTPSampler.connect_timeout"></stringProp>
+          <stringProp name="HTTPSampler.response_timeout"></stringProp>
+        </HTTPSamplerProxy>
+        <hashTree>
+          <JSONPostProcessor guiclass="JSONPostProcessorGui" testclass="JSONPostProcessor" testname="JSON Extractor" enabled="true">
+            <stringProp name="JSONPostProcessor.referenceNames">message</stringProp>
+            <stringProp name="JSONPostProcessor.jsonPathExprs">$.message</stringProp>
+            <stringProp name="JSONPostProcessor.match_numbers">1</stringProp>
+            <boolProp name="JSONPostProcessor.compute_concat">true</boolProp>
+            <stringProp name="JSONPostProcessor.defaultValues">NOT_FOUND</stringProp>
+          </JSONPostProcessor>
+          <hashTree/>
+          <BeanShellPostProcessor guiclass="TestBeanGUI" testclass="BeanShellPostProcessor" testname="Response to file using BeanShell PostProcessor" enabled="true">
+            <stringProp name="filename"></stringProp>
+            <stringProp name="parameters"></stringProp>
+            <boolProp name="resetInterpreter">false</boolProp>
+            <stringProp name="script">FileWriter fWriter = new FileWriter(&quot;<path>/result.txt&quot;, true);
+BufferedWriter buff = new BufferedWriter(fWriter);
+
+buff.write(&quot;Response Code : &quot; + ctx.getPreviousResult().getResponseCode());
+buff.write(System.getProperty(&quot;line.separator&quot;));
+buff.write(&quot;Response Headers : &quot; + ctx.getPreviousResult().getResponseHeaders());
+buff.write(System.getProperty(&quot;line.separator&quot;));
+buff.write(&quot;Response Body : &quot; + new String(ctx.getPreviousResult().getResponseData()));
+
+buff.write(&quot;More complex extraction : &quot; + vars.get(&quot;message&quot;));
+
+buff.close();
+fWriter.close();</stringProp>
+          </BeanShellPostProcessor>
+          <hashTree/>
+          <ResultSaver guiclass="ResultSaverGui" testclass="ResultSaver" testname="Response to file using file write Listener" enabled="true">
+            <stringProp name="FileSaver.filename">response</stringProp>
+            <boolProp name="FileSaver.errorsonly">false</boolProp>
+            <boolProp name="FileSaver.successonly">false</boolProp>
+            <boolProp name="FileSaver.skipsuffix">false</boolProp>
+            <boolProp name="FileSaver.skipautonumber">false</boolProp>
+          </ResultSaver>
+          <hashTree/>
+        </hashTree>
+        <ResultCollector guiclass="ViewResultsFullVisualizer" testclass="ResultCollector" testname="View Results Tree" enabled="true">
+          <boolProp name="ResultCollector.error_logging">false</boolProp>
+          <objProp>
+            <name>saveConfig</name>
+            <value class="SampleSaveConfiguration">
+              <time>true</time>
+              <latency>true</latency>
+              <timestamp>true</timestamp>
+              <success>true</success>
+              <label>true</label>
+              <code>true</code>
+              <message>true</message>
+              <threadName>true</threadName>
+              <dataType>true</dataType>
+              <encoding>false</encoding>
+              <assertions>true</assertions>
+              <subresults>true</subresults>
+              <responseData>false</responseData>
+              <samplerData>false</samplerData>
+              <xml>false</xml>
+              <fieldNames>true</fieldNames>
+              <responseHeaders>false</responseHeaders>
+              <requestHeaders>false</requestHeaders>
+              <responseDataOnError>false</responseDataOnError>
+              <saveAssertionResultsFailureMessage>true</saveAssertionResultsFailureMessage>
+              <assertionsResultsToSave>0</assertionsResultsToSave>
+              <bytes>true</bytes>
+              <sentBytes>true</sentBytes>
+              <url>true</url>
+              <threadCounts>true</threadCounts>
+              <idleTime>true</idleTime>
+              <connectTime>true</connectTime>
+            </value>
+          </objProp>
+          <stringProp name="filename"></stringProp>
+        </ResultCollector>
+        <hashTree/>
+      </hashTree>
+    </hashTree>
+  </hashTree>
+</jmeterTestPlan>

jmeter/src/test/java/com/baeldung/JmeterIntegrationTest.java

@@ -0,0 +1,35 @@
+package com.baeldung;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.context.WebApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@SpringBootTest
+class JmeterIntegrationTest {
+
+    MockMvc mvc;
+
+    public JmeterIntegrationTest(WebApplicationContext wac) {
+        this.mvc = MockMvcBuilders.webAppContextSetup(wac).build();
+    }
+
+    @Test
+    void whenCallingUUIDController_thenWeShouldRecieveRandomizedResponse() throws Exception {
+        MockHttpServletResponse response = mvc.perform(get("/api/uuid"))
+          .andDo(print())
+          .andExpect(status().isOk())
+          .andReturn()
+          .getResponse();
+
+        assertThat(response.getContentAsString())
+          .contains("Test message...");
+    }
+}

kubernetes/k8s-intro/README.md

@@ -0,0 +1,13 @@
+# Kubernetes Java API Sample Code
+
+This module contains sample code used to show how to use the Kubernetes client Java API.
+
+Before running those samples, make sure that your environment is correctly configured to access
+a working Kubernetes cluster.
+
+An easy way to check that everything is working as expected is issuing any *kubectl get* command:
+
+```shell
+$ kubectl get nodes
+```
+If you get a valid response, then you're good to go.

kubernetes/k8s-intro/pom.xml

@@ -0,0 +1,41 @@
+<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>
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>kubernetes-parent</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <artifactId>k8s-intro</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+
+    <dependencies>
+        <dependency>
+            <groupId>io.kubernetes</groupId>
+            <artifactId>client-java</artifactId>
+            <version>11.0.0</version>
+        </dependency>
+
+        <dependency>
+            <groupId>ch.qos.logback</groupId>
+            <artifactId>logback-classic</artifactId>
+            <version>1.2.3</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.8.1</version>
+                <configuration>
+                    <!-- http://maven.apache.org/plugins/maven-compiler-plugin/ -->
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

kubernetes/k8s-intro/src/main/java/com/baeldung/kubernetes/intro/ApiInvoker.java

@@ -0,0 +1,11 @@
+package com.baeldung.kubernetes.intro;
+
+import io.kubernetes.client.openapi.ApiCallback;
+import io.kubernetes.client.openapi.ApiException;
+import io.kubernetes.client.openapi.apis.CoreV1Api;
+import okhttp3.Call;
+
+@FunctionalInterface
+public interface ApiInvoker<R> {
+    Call apply(CoreV1Api api, ApiCallback<R> callback) throws ApiException;
+}

kubernetes/k8s-intro/src/main/java/com/baeldung/kubernetes/intro/AsyncHelper.java

@@ -0,0 +1,74 @@
+package com.baeldung.kubernetes.intro;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
+import java.util.function.BiFunction;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import io.kubernetes.client.openapi.ApiCallback;
+import io.kubernetes.client.openapi.ApiException;
+import io.kubernetes.client.openapi.apis.CoreV1Api;
+import okhttp3.Call;
+
+public class AsyncHelper<R>  implements ApiCallback<R> {
+    
+    private static final Logger log = LoggerFactory.getLogger(AsyncHelper.class);
+    
+    private CoreV1Api api;
+    private CompletableFuture<R> callResult;
+    
+    private AsyncHelper(CoreV1Api api) {
+        this.api = api;
+    }
+    
+    public static <T> CompletableFuture<T> doAsync(CoreV1Api api, ApiInvoker<T> invoker) {
+        
+        AsyncHelper<T> p = new AsyncHelper<>(api);
+        return p.execute(invoker);
+    }
+    
+    private CompletableFuture<R> execute( ApiInvoker<R> invoker) {
+        
+        try {
+            callResult = new CompletableFuture<>();
+            log.info("[I38] Calling API...");
+            final Call call = invoker.apply(api,this);
+            log.info("[I41] API Succesfully invoked: method={}, url={}",
+              call.request().method(),
+              call.request().url());
+            return callResult;
+        }
+        catch(ApiException aex) {
+            callResult.completeExceptionally(aex);
+            return callResult;
+        }
+    }
+
+    @Override
+    public void onFailure(ApiException e, int statusCode, Map<String, List<String>> responseHeaders) {
+        log.error("[E53] onFailure",e);
+        callResult.completeExceptionally(e);
+    }
+
+    @Override
+    public void onSuccess(R result, int statusCode, Map<String, List<String>> responseHeaders) {
+        log.error("[E61] onSuccess: statusCode={}",statusCode);
+        callResult.complete(result);
+    }
+
+    @Override
+    public void onUploadProgress(long bytesWritten, long contentLength, boolean done) {
+        log.info("[E61] onUploadProgress: bytesWritten={}, contentLength={}, done={}",bytesWritten,contentLength,done);
+    }
+
+    @Override
+    public void onDownloadProgress(long bytesRead, long contentLength, boolean done) {
+        log.info("[E75] onDownloadProgress: bytesRead={}, contentLength={}, done={}",bytesRead,contentLength,done);
+    }
+}
+

kubernetes/k8s-intro/src/main/java/com/baeldung/kubernetes/intro/ListNodes.java

@@ -0,0 +1,31 @@
+/**
+ * 
+ */
+package com.baeldung.kubernetes.intro;
+
+
+import io.kubernetes.client.openapi.ApiClient;
+import io.kubernetes.client.openapi.apis.CoreV1Api;
+import io.kubernetes.client.openapi.models.V1NodeList;
+import io.kubernetes.client.util.Config;
+
+/**
+ * @author Philippe
+ *
+ */
+public class ListNodes {
+
+    /**
+     * @param args
+     */
+    public static void main(String[] args) throws Exception {
+        
+        ApiClient client  = Config.defaultClient();
+        CoreV1Api api = new CoreV1Api(client);
+        V1NodeList nodeList = api.listNode(null, null, null, null, null, null, null, null, 10, false);
+        nodeList.getItems()
+          .stream()
+          .forEach((node) -> System.out.println(node.getMetadata()));
+    }
+
+}

kubernetes/k8s-intro/src/main/java/com/baeldung/kubernetes/intro/ListNodesAsync.java

@@ -0,0 +1,50 @@
+/**
+ * 
+ */
+package com.baeldung.kubernetes.intro;
+
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import io.kubernetes.client.openapi.ApiClient;
+import io.kubernetes.client.openapi.apis.CoreV1Api;
+import io.kubernetes.client.openapi.models.V1NodeList;
+import io.kubernetes.client.util.Config;
+
+/**
+ * @author Philippe
+ *
+ */
+public class ListNodesAsync {
+    
+    private static Logger log = LoggerFactory.getLogger(ListNodesAsync.class);
+    /**
+     * @param args
+     */
+    public static void main(String[] args) throws Exception {
+        
+        // Initial setup
+        ApiClient client  = Config.defaultClient();
+        CoreV1Api api = new CoreV1Api(client);
+        
+        // Start async call
+        CompletableFuture<V1NodeList> p = AsyncHelper.doAsync(api,(capi,cb) ->
+          capi.listNodeAsync(null, null, null, null, null, null, null, null, 10, false, cb)
+        );
+        
+        p.thenAcceptAsync((nodeList) -> {
+            log.info("[I40] Processing results...");
+            nodeList.getItems()
+            .stream()
+            .forEach((node) -> System.out.println(node.getMetadata()));
+        });
+        
+        log.info("[I46] Waiting results...");
+        p.get(10, TimeUnit.SECONDS);
+    }
+
+}

kubernetes/k8s-intro/src/main/java/com/baeldung/kubernetes/intro/ListPodsPaged.java

@@ -0,0 +1,46 @@
+/**
+ * 
+ */
+package com.baeldung.kubernetes.intro;
+
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import io.kubernetes.client.openapi.ApiClient;
+import io.kubernetes.client.openapi.apis.CoreV1Api;
+import io.kubernetes.client.openapi.models.V1NodeList;
+import io.kubernetes.client.openapi.models.V1PodList;
+import io.kubernetes.client.util.Config;
+
+/**
+ * @author Philippe
+ *
+ */
+public class ListPodsPaged {
+    
+    private static final Logger log = LoggerFactory.getLogger(ListPodsPaged.class);
+
+    /**
+     * @param args
+     */
+    public static void main(String[] args) throws Exception {
+        
+        ApiClient client  = Config.defaultClient();
+        CoreV1Api api = new CoreV1Api(client);
+        String continuationToken = null;
+        int limit = 2; // Just for illustration purposes. Real world values would range from ~100 to ~1000/page 
+        Long remaining = null; 
+        do {
+            log.info("==========================================================================");
+            log.info("Retrieving data: continuationToken={}, remaining={}", continuationToken,remaining);
+            V1PodList items = api.listPodForAllNamespaces(null, continuationToken, null, null, limit, null, null, null, 10, false);
+            continuationToken = items.getMetadata().getContinue();
+            remaining = items.getMetadata().getRemainingItemCount();
+            items.getItems()
+              .stream()
+              .forEach((node) -> System.out.println(node.getMetadata()));
+        } while( continuationToken != null );
+    }
+
+}

kubernetes/k8s-intro/src/test/java/com/baeldung/kubernetes/intro/ListNodesAsyncLiveTest.java

@@ -0,0 +1,10 @@
+package com.baeldung.kubernetes.intro;
+
+import org.junit.jupiter.api.Test;
+
+class ListNodesAsyncLiveTest {
+    @Test
+    void whenListNodes_thenSuccess()  throws Exception {
+        ListNodesAsync.main(new String[] {});
+    }
+}

kubernetes/k8s-intro/src/test/java/com/baeldung/kubernetes/intro/ListNodesLiveTest.java

@@ -0,0 +1,10 @@
+package com.baeldung.kubernetes.intro;
+
+import org.junit.jupiter.api.Test;
+
+class ListNodesLiveTest {
+    @Test
+    void whenListNodes_thenSuccess()  throws Exception {
+        ListNodes.main(new String[] {});
+    }
+}

kubernetes/k8s-intro/src/test/java/com/baeldung/kubernetes/intro/ListPodsPagedLiveTest.java

@@ -0,0 +1,10 @@
+package com.baeldung.kubernetes.intro;
+
+import org.junit.jupiter.api.Test;
+
+class ListPodsPagedLiveTest {
+    @Test
+    void whenListPodsPage_thenSuccess()  throws Exception {
+        ListPodsPaged.main(new String[] {});
+    }
+}

kubernetes/k8s-intro/src/test/resources/logback.xml

@@ -0,0 +1,11 @@
+<configuration>
+  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <root level="debug">
+    <appender-ref ref="STDOUT" />
+  </root>
+</configuration>

kubernetes/pom.xml

@@ -0,0 +1,13 @@
+<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>
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <artifactId>kubernetes-parent</artifactId>
+    <packaging>pom</packaging>
+    <modules>
+        <module>k8s-intro</module>
+    </modules>
+</project>

libraries-http-2/README.md

@@ -7,5 +7,6 @@ This module contains articles about HTTP libraries.
 - [Jetty ReactiveStreams HTTP Client](https://www.baeldung.com/jetty-reactivestreams-http-client)
 - [Decode an OkHttp JSON Response](https://www.baeldung.com/okhttp-json-response)
 - [Retrofit 2 – Dynamic URL](https://www.baeldung.com/retrofit-dynamic-url)
+- [Adding Interceptors in OkHTTP](https://www.baeldung.com/java-okhttp-interceptors)
 - More articles [[<-- prev]](/libraries-http)
 

libraries-http-2/pom.xml

@@ -1,7 +1,7 @@
 <?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">
+    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>libraries-http-2</artifactId>
     <name>libraries-http-2</name>
@@ -13,12 +13,17 @@
     </parent>
 
     <dependencies>
-         <!-- Dependencies for response decoder with okhttp -->
+        <!-- Dependencies for response decoder with okhttp -->
         <dependency>
             <groupId>com.squareup.okhttp3</groupId>
             <artifactId>okhttp</artifactId>
             <version>${okhttp.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.squareup.okhttp3</groupId>
+            <artifactId>logging-interceptor</artifactId>
+            <version>${okhttp.version}</version>
+        </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
@@ -81,9 +86,9 @@
     </dependencies>
 
     <properties>
-        <okhttp.version>3.14.2</okhttp.version>
+        <okhttp.version>4.9.1</okhttp.version>
         <gson.version>2.8.5</gson.version>
-        <mockwebserver.version>3.14.2</mockwebserver.version>
+        <mockwebserver.version>4.9.1</mockwebserver.version>
         <jetty.httpclient.version>1.0.3</jetty.httpclient.version>
         <jetty.server.version>9.4.19.v20190610</jetty.server.version>
         <rxjava2.version>2.2.11</rxjava2.version>

libraries-http-2/src/main/java/com/baeldung/okhttp/interceptors/CacheControlResponeInterceptor.java

@@ -0,0 +1,18 @@
+package com.baeldung.okhttp.interceptors;
+
+import java.io.IOException;
+
+import okhttp3.Interceptor;
+import okhttp3.Response;
+
+public class CacheControlResponeInterceptor implements Interceptor {
+
+    @Override
+    public Response intercept(Chain chain) throws IOException {
+        Response response = chain.proceed(chain.request());
+        return response.newBuilder()
+            .header("Cache-Control", "no-store")
+            .build();
+    }
+
+}

libraries-http-2/src/main/java/com/baeldung/okhttp/interceptors/ErrorMessage.java

@@ -0,0 +1,21 @@
+package com.baeldung.okhttp.interceptors;
+
+public class ErrorMessage {
+
+    private final int status;
+    private final String detail;
+
+    public ErrorMessage(int status, String detail) {
+        this.status = status;
+        this.detail = detail;
+    }
+
+    public int getStatus() {
+        return status;
+    }
+
+    public String getDetail() {
+        return detail;
+    }
+
+}

libraries-http-2/src/main/java/com/baeldung/okhttp/interceptors/ErrorResponseInterceptor.java

@@ -0,0 +1,32 @@
+package com.baeldung.okhttp.interceptors;
+
+import java.io.IOException;
+
+import com.google.gson.Gson;
+
+import okhttp3.Interceptor;
+import okhttp3.MediaType;
+import okhttp3.Response;
+import okhttp3.ResponseBody;
+
+public class ErrorResponseInterceptor implements Interceptor {
+    
+    public static final MediaType APPLICATION_JSON = MediaType.get("application/json; charset=utf-8");
+
+    @Override
+    public Response intercept(Chain chain) throws IOException {
+        Response response = chain.proceed(chain.request());
+        
+        if(!response.isSuccessful()) {
+            Gson gson = new Gson();
+            String body = gson.toJson(new ErrorMessage(response.code(), "The response from the server was not OK"));
+            ResponseBody responseBody = ResponseBody.create(body, APPLICATION_JSON);
+            
+            return response.newBuilder()
+                .body(responseBody)
+                .build();
+        }
+        return response;
+    }
+
+}

libraries-http-2/src/main/java/com/baeldung/okhttp/interceptors/SimpleLoggingInterceptor.java

@@ -0,0 +1,25 @@
+package com.baeldung.okhttp.interceptors;
+
+import java.io.IOException;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import okhttp3.Interceptor;
+import okhttp3.Request;
+import okhttp3.Response;
+
+public class SimpleLoggingInterceptor implements Interceptor {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(SimpleLoggingInterceptor.class);
+
+    @Override
+    public Response intercept(Chain chain) throws IOException {
+        Request request = chain.request();
+
+        LOGGER.info("Intercepted headers: {} from URL: {}", request.headers(), request.url());
+
+        return chain.proceed(request);
+    }
+
+}

libraries-http-2/src/test/java/com/baeldung/okhttp/interceptors/InterceptorIntegrationTest.java

@@ -0,0 +1,90 @@
+package com.baeldung.okhttp.interceptors;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+
+import org.junit.Rule;
+import org.junit.Test;
+
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.Response;
+import okhttp3.logging.HttpLoggingInterceptor;
+import okhttp3.logging.HttpLoggingInterceptor.Level;
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+
+public class InterceptorIntegrationTest {
+
+    @Rule
+    public MockWebServer server = new MockWebServer();
+
+    @Test
+    public void givenSimpleLogginInterceptor_whenRequestSent_thenHeadersLogged() throws IOException {
+        server.enqueue(new MockResponse().setBody("Hello Baeldung Readers!"));
+        
+        OkHttpClient client = new OkHttpClient.Builder()
+            .addNetworkInterceptor(new SimpleLoggingInterceptor())
+            .build();
+
+        Request request = new Request.Builder()
+            .url(server.url("/greeting"))
+            .header("User-Agent", "A Baeldung Reader")
+            .build();
+
+        try (Response response = client.newCall(request).execute()) {
+            assertEquals("Response code should be: ", 200, response.code());
+            assertEquals("Body should be: ", "Hello Baeldung Readers!", response.body().string());
+        }
+    }
+    
+    @Test
+    public void givenResponseInterceptor_whenRequestSent_thenCacheControlSetToNoStore() throws IOException {
+        server.enqueue(new MockResponse().setBody("Hello Baeldung Readers!"));
+        
+        OkHttpClient client = new OkHttpClient.Builder()
+            .addInterceptor(getHttpLogger())
+            .addInterceptor(new CacheControlResponeInterceptor())
+            .build();
+
+        Request request = new Request.Builder()
+            .url(server.url("/greeting"))
+            .header("User-Agent", "A Baeldung Reader")
+            .build();
+
+        try (Response response = client.newCall(request).execute()) {
+            assertEquals("Response code should be: ", 200, response.code());
+            assertEquals("Body should be: ", "Hello Baeldung Readers!", response.body().string());
+            assertEquals("Response cache-control should be", "no-store", response.header("Cache-Control"));
+        }
+    }
+    
+    @Test
+    public void givenErrorResponseInterceptor_whenResponseIs500_thenBodyIsJsonWithStatus() throws IOException {
+        server.enqueue(new MockResponse().setResponseCode(500).setBody("Hello Baeldung Readers!"));
+        
+        OkHttpClient client = new OkHttpClient.Builder()
+            .addInterceptor(getHttpLogger())
+            .addInterceptor(new ErrorResponseInterceptor())
+            .build();
+
+        Request request = new Request.Builder()
+            .url(server.url("/greeting"))
+            .header("User-Agent", "A Baeldung Reader")
+            .build();
+
+        try (Response response = client.newCall(request).execute()) {
+            assertEquals("Response code should be: ", 500, response.code());
+            assertEquals("Body should be: ", "{\"status\":500,\"detail\":\"The response from the server was not OK\"}", 
+                response.body().string());
+        }
+    }
+
+    private HttpLoggingInterceptor getHttpLogger() {
+        HttpLoggingInterceptor logger = new HttpLoggingInterceptor();
+        logger.setLevel(Level.HEADERS);
+        return logger;
+    }
+
+}

maven-modules/maven-plugins/jaxws/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Generate WSDL Stubs with Maven](https://www.baeldung.com/maven-wsdl-stubs)