Merge pull request #1 from eugenp/master

update

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

@@ -5,7 +5,7 @@ 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)

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/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-maps-3/README.md

@@ -7,4 +7,5 @@ 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)
 - 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/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-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-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-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-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"
+          );
+    }
+}

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);
+    }
+
+}