Merge branch 'master' into feature/ktln-43/working-with-lists-in-kotlin

core-java-modules/core-java-14/src/main/java/com/baeldung/java14/record/Person.java

@@ -4,19 +4,19 @@ import java.util.Objects;
 
 public record Person (String name, String address) {
 	
-	public static String UNKWOWN_ADDRESS = "Unknown";
-	public static String UNNAMED = "Unnamed";
+	  public static String UNKNOWN_ADDRESS = "Unknown";
+	  public static String UNNAMED = "Unnamed";
 
-	public Person {
-		Objects.requireNonNull(name);
-		Objects.requireNonNull(address);
-	}
+	  public Person {
+		    Objects.requireNonNull(name);
+		    Objects.requireNonNull(address);
+	  }
 	
-	public Person(String name) {
-		this(name, UNKWOWN_ADDRESS);
-	}
+	  public Person(String name) {
+		    this(name, UNKNOWN_ADDRESS);
+	  }
 	
-	public static Person unnamed(String address) {
-		return new Person(UNNAMED, address);
-	}
-}
+	  public static Person unnamed(String address) {
+		    return new Person(UNNAMED, address);
+	  }
+}

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/record/PersonTest.java

@@ -134,7 +134,7 @@ public class PersonTest {
         Person person = new Person(name);
 
         assertEquals(name, person.name());
-        assertEquals(Person.UNKWOWN_ADDRESS, person.address());
+        assertEquals(Person.UNKNOWN_ADDRESS, person.address());
     }
 
     @Test
@@ -147,4 +147,4 @@ public class PersonTest {
         assertEquals(Person.UNNAMED, person.name());
         assertEquals(address, person.address());
     }
-}
+}

core-java-modules/core-java-8-datetime-2/pom.xml

@@ -4,7 +4,7 @@
     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-8-datetime</artifactId>
+    <artifactId>core-java-8-datetime-2</artifactId>
     <version>${project.parent.version}</version>
     <name>core-java-8-datetime</name>
     <packaging>jar</packaging>
@@ -41,7 +41,6 @@
     </dependencies>
 
     <build>
-        <finalName>core-java-datetime-java8</finalName>
         <resources>
             <resource>
                 <directory>src/main/resources</directory>

core-java-modules/core-java-9-new-features/src/test/java/com/baeldung/java9/varhandles/VariableHandlesUnitTest.java

@@ -5,7 +5,7 @@ import org.junit.Test;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.VarHandle;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
 
 public class VariableHandlesUnitTest {
 
@@ -18,25 +18,23 @@ public class VariableHandlesUnitTest {
 
     @Test
     public void whenVariableHandleForPublicVariableIsCreated_ThenItIsInitializedProperly() throws NoSuchFieldException, IllegalAccessException {
-        VarHandle publicIntHandle = MethodHandles
+        VarHandle PUBLIC_TEST_VARIABLE = MethodHandles
           .lookup()
           .in(VariableHandlesUnitTest.class)
           .findVarHandle(VariableHandlesUnitTest.class, "publicTestVariable", int.class);
 
-        assertThat(publicIntHandle.coordinateTypes().size() == 1);
-        assertThat(publicIntHandle.coordinateTypes().get(0) == VariableHandlesUnitTest.class);
-
+        assertEquals(1, PUBLIC_TEST_VARIABLE.coordinateTypes().size());
+        assertEquals(VariableHandlesUnitTest.class, PUBLIC_TEST_VARIABLE.coordinateTypes().get(0));
     }
 
     @Test
     public void whenVariableHandleForPrivateVariableIsCreated_ThenItIsInitializedProperly() throws NoSuchFieldException, IllegalAccessException {
-        VarHandle privateIntHandle = MethodHandles
+        VarHandle PRIVATE_TEST_VARIABLE = MethodHandles
           .privateLookupIn(VariableHandlesUnitTest.class, MethodHandles.lookup())
           .findVarHandle(VariableHandlesUnitTest.class, "privateTestVariable", int.class);
 
-        assertThat(privateIntHandle.coordinateTypes().size() == 1);
-        assertThat(privateIntHandle.coordinateTypes().get(0) == VariableHandlesUnitTest.class);
-
+        assertEquals(1, PRIVATE_TEST_VARIABLE.coordinateTypes().size());
+        assertEquals(VariableHandlesUnitTest.class, PRIVATE_TEST_VARIABLE.coordinateTypes().get(0));
     }
 
     @Test
@@ -44,63 +42,64 @@ public class VariableHandlesUnitTest {
         VarHandle arrayVarHandle = MethodHandles
           .arrayElementVarHandle(int[].class);
 
-        assertThat(arrayVarHandle.coordinateTypes().size() == 2);
-        assertThat(arrayVarHandle.coordinateTypes().get(0) == int[].class);
+        assertEquals(2, arrayVarHandle.coordinateTypes().size());
+        assertEquals(int[].class, arrayVarHandle.coordinateTypes().get(0));
     }
 
     @Test
     public void givenVarHandle_whenGetIsInvoked_ThenValueOfVariableIsReturned() throws NoSuchFieldException, IllegalAccessException {
-        VarHandle publicIntHandle = MethodHandles
+        VarHandle PUBLIC_TEST_VARIABLE = MethodHandles
           .lookup()
           .in(VariableHandlesUnitTest.class)
           .findVarHandle(VariableHandlesUnitTest.class, "publicTestVariable", int.class);
 
-        assertThat((int) publicIntHandle.get(this) == 1);
+        assertEquals(1, (int) PUBLIC_TEST_VARIABLE.get(this));
     }
 
     @Test
     public void givenVarHandle_whenSetIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
-        VarHandle publicIntHandle = MethodHandles
+        VarHandle VARIABLE_TO_SET = MethodHandles
           .lookup()
           .in(VariableHandlesUnitTest.class)
           .findVarHandle(VariableHandlesUnitTest.class, "variableToSet", int.class);
-        publicIntHandle.set(this, 15);
 
-        assertThat((int) publicIntHandle.get(this) == 15);
+        VARIABLE_TO_SET.set(this, 15);
+        assertEquals(15, (int) VARIABLE_TO_SET.get(this));
     }
 
     @Test
     public void givenVarHandle_whenCompareAndSetIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
-        VarHandle publicIntHandle = MethodHandles
+        VarHandle VARIABLE_TO_COMPARE_AND_SET = MethodHandles
           .lookup()
           .in(VariableHandlesUnitTest.class)
           .findVarHandle(VariableHandlesUnitTest.class, "variableToCompareAndSet", int.class);
-        publicIntHandle.compareAndSet(this, 1, 100);
 
-        assertThat((int) publicIntHandle.get(this) == 100);
+        VARIABLE_TO_COMPARE_AND_SET.compareAndSet(this, 1, 100);
+        assertEquals(100, (int) VARIABLE_TO_COMPARE_AND_SET.get(this));
     }
 
     @Test
     public void givenVarHandle_whenGetAndAddIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
-        VarHandle publicIntHandle = MethodHandles
+        VarHandle VARIABLE_TO_GET_AND_ADD = MethodHandles
           .lookup()
           .in(VariableHandlesUnitTest.class)
           .findVarHandle(VariableHandlesUnitTest.class, "variableToGetAndAdd", int.class);
-        int before = (int) publicIntHandle.getAndAdd(this, 200);
 
-        assertThat(before == 0);
-        assertThat((int) publicIntHandle.get(this) == 200);
+        int before = (int) VARIABLE_TO_GET_AND_ADD.getAndAdd(this, 200);
+
+        assertEquals(0, before);
+        assertEquals(200, (int) VARIABLE_TO_GET_AND_ADD.get(this));
     }
 
     @Test
     public void givenVarHandle_whenGetAndBitwiseOrIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
-        VarHandle publicIntHandle = MethodHandles
+        VarHandle VARIABLE_TO_BITWISE_OR = MethodHandles
           .lookup()
           .in(VariableHandlesUnitTest.class)
           .findVarHandle(VariableHandlesUnitTest.class, "variableToBitwiseOr", byte.class);
-        byte before = (byte) publicIntHandle.getAndBitwiseOr(this, (byte) 127);
+        byte before = (byte) VARIABLE_TO_BITWISE_OR.getAndBitwiseOr(this, (byte) 127);
 
-        assertThat(before == 0);
-        assertThat(variableToBitwiseOr == 127);
+        assertEquals(0, before);
+        assertEquals(127, (byte) VARIABLE_TO_BITWISE_OR.get(this));
     }
 }

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

@@ -9,3 +9,4 @@
 - [Differences Between Collection.clear() and Collection.removeAll()](https://www.baeldung.com/java-collection-clear-vs-removeall)
 - [Performance of contains() in a HashSet vs ArrayList](https://www.baeldung.com/java-hashset-arraylist-contains-performance)
 - [Fail-Safe Iterator vs Fail-Fast Iterator](https://www.baeldung.com/java-fail-safe-vs-fail-fast-iterator)
+- [Quick Guide to the Java Stack](https://www.baeldung.com/java-stack)

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/abaproblem/Account.java

@@ -0,0 +1,66 @@
+package com.baeldung.abaproblem;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Account {
+
+    private AtomicInteger balance;
+    private AtomicInteger transactionCount;
+    private ThreadLocal<Integer> currentThreadCASFailureCount;
+
+    public Account() {
+        this.balance = new AtomicInteger(0);
+        this.transactionCount = new AtomicInteger(0);
+        this.currentThreadCASFailureCount = new ThreadLocal<>();
+        this.currentThreadCASFailureCount.set(0);
+    }
+
+    public int getBalance() {
+        return balance.get();
+    }
+
+    public int getTransactionCount() {
+        return transactionCount.get();
+    }
+
+    public int getCurrentThreadCASFailureCount() {
+        return currentThreadCASFailureCount.get();
+    }
+
+    public boolean withdraw(int amount) {
+        int current = getBalance();
+        maybeWait();
+        boolean result = balance.compareAndSet(current, current - amount);
+        if (result) {
+            transactionCount.incrementAndGet();
+        } else {
+            int currentCASFailureCount = currentThreadCASFailureCount.get();
+            currentThreadCASFailureCount.set(currentCASFailureCount + 1);
+        }
+        return result;
+    }
+
+    private void maybeWait() {
+        if ("thread1".equals(Thread.currentThread().getName())) {
+            try {
+                TimeUnit.SECONDS.sleep(2);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        }
+    }
+
+    public boolean deposit(int amount) {
+        int current = balance.get();
+        boolean result = balance.compareAndSet(current, current + amount);
+        if (result) {
+            transactionCount.incrementAndGet();
+        } else {
+            int currentCASFailureCount = currentThreadCASFailureCount.get();
+            currentThreadCASFailureCount.set(currentCASFailureCount + 1);
+        }
+        return result;
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-3/src/test/java/com/baeldung/abaproblem/AccountUnitTest.java

@@ -0,0 +1,98 @@
+package com.baeldung.abaproblem;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class AccountUnitTest {
+
+    private Account account;
+
+    @BeforeEach
+    public void setUp() {
+        account = new Account();
+    }
+
+    @Test
+    public void zeroBalanceInitializationTest() {
+        assertEquals(0, account.getBalance());
+        assertEquals(0, account.getTransactionCount());
+        assertEquals(0, account.getCurrentThreadCASFailureCount());
+    }
+
+    @Test
+    public void depositTest() {
+        final int moneyToDeposit = 50;
+
+        assertTrue(account.deposit(moneyToDeposit));
+
+        assertEquals(moneyToDeposit, account.getBalance());
+    }
+
+    @Test
+    public void withdrawTest() throws InterruptedException {
+        final int defaultBalance = 50;
+        final int moneyToWithdraw = 20;
+
+        account.deposit(defaultBalance);
+
+        assertTrue(account.withdraw(moneyToWithdraw));
+
+        assertEquals(defaultBalance - moneyToWithdraw, account.getBalance());
+    }
+
+    @Test
+    public void abaProblemTest() throws InterruptedException {
+        final int defaultBalance = 50;
+
+        final int amountToWithdrawByThread1 = 20;
+        final int amountToWithdrawByThread2 = 10;
+        final int amountToDepositByThread2 = 10;
+
+        assertEquals(0, account.getTransactionCount());
+        assertEquals(0, account.getCurrentThreadCASFailureCount());
+        account.deposit(defaultBalance);
+        assertEquals(1, account.getTransactionCount());
+
+        Thread thread1 = new Thread(() -> {
+
+            // this will take longer due to the name of the thread
+            assertTrue(account.withdraw(amountToWithdrawByThread1));
+
+            // thread 1 fails to capture ABA problem
+            assertNotEquals(1, account.getCurrentThreadCASFailureCount());
+
+        }, "thread1");
+
+        Thread thread2 = new Thread(() -> {
+
+            assertTrue(account.deposit(amountToDepositByThread2));
+            assertEquals(defaultBalance + amountToDepositByThread2, account.getBalance());
+
+            // this will be fast due to the name of the thread
+            assertTrue(account.withdraw(amountToWithdrawByThread2));
+
+            // thread 1 didn't finish yet, so the original value will be in place for it
+            assertEquals(defaultBalance, account.getBalance());
+
+            assertEquals(0, account.getCurrentThreadCASFailureCount());
+        }, "thread2");
+
+        thread1.start();
+        thread2.start();
+        thread1.join();
+        thread2.join();
+
+        // compareAndSet operation succeeds for thread 1
+        assertEquals(defaultBalance - amountToWithdrawByThread1, account.getBalance());
+
+        //but there are other transactions
+        assertNotEquals(2, account.getTransactionCount());
+
+        // thread 2 did two modifications as well
+        assertEquals(4, account.getTransactionCount());
+    }
+}

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

@@ -0,0 +1,5 @@
+#Core Java Console
+
+[Read and Write User Input in Java](http://www.baeldung.com/java-console-input-output)
+[Formatting with printf() in Java](https://www.baeldung.com/java-printstream-printf)
+[ASCII Art in Java](http://www.baeldung.com/ascii-art-in-java)

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

@@ -0,0 +1,142 @@
+<?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-console</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-console</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>
+
+    <build>
+        <finalName>core-java-console</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>copy-dependencies</id>
+                        <phase>prepare-package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}/libs</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>${exec-maven-plugin.version}</version>
+                <configuration>
+                    <executable>java</executable>
+                    <mainClass>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</mainClass>
+                    <arguments>
+                        <argument>-Xmx300m</argument>
+                        <argument>-XX:+UseParallelGC</argument>
+                        <argument>-classpath</argument>
+                        <classpath />
+                        <argument>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</argument>
+                    </arguments>
+                </configuration>
+            </plugin>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>${maven-javadoc-plugin.version}</version>
+                <configuration>
+                    <source>${source.version}</source>
+                    <target>${target.version}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <profiles>
+        <profile>
+            <id>integration</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <phase>integration-test</phase>
+                                <goals>
+                                    <goal>test</goal>
+                                </goals>
+                                <configuration>
+                                    <excludes>
+                                        <exclude>**/*ManualTest.java</exclude>
+                                    </excludes>
+                                    <includes>
+                                        <include>**/*IntegrationTest.java</include>
+                                        <include>**/*IntTest.java</include>
+                                    </includes>
+                                </configuration>
+                            </execution>
+                        </executions>
+                        <configuration>
+                            <systemPropertyVariables>
+                                <test.mime>json</test.mime>
+                            </systemPropertyVariables>
+                        </configuration>
+                    </plugin>
+                    <plugin>
+                        <groupId>org.codehaus.mojo</groupId>
+                        <artifactId>exec-maven-plugin</artifactId>
+                        <version>${exec-maven-plugin.version}</version>
+                        <executions>
+                            <execution>
+                                <id>run-benchmarks</id>
+                                <!-- <phase>integration-test</phase> -->
+                                <phase>none</phase>
+                                <goals>
+                                    <goal>exec</goal>
+                                </goals>
+                                <configuration>
+                                    <classpathScope>test</classpathScope>
+                                    <executable>java</executable>
+                                    <arguments>
+                                        <argument>-classpath</argument>
+                                        <classpath />
+                                        <argument>org.openjdk.jmh.Main</argument>
+                                        <argument>.*</argument>
+                                    </arguments>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
+
+    <properties>
+        <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
+        <exec-maven-plugin.version>1.6.0</exec-maven-plugin.version>
+        <source.version>1.8</source.version>
+        <target.version>1.8</target.version>
+    </properties>
+
+</project>

core-java-modules/core-java-console/src/test/java/com/baeldung/asciiart/AsciiArtIntegrationTest.java

@@ -1,10 +1,9 @@
 package com.baeldung.asciiart;
 
-import java.awt.Font;
-
+import com.baeldung.asciiart.AsciiArt.Settings;
 import org.junit.Test;
 
-import com.baeldung.asciiart.AsciiArt.Settings;
+import java.awt.*;
 
 public class AsciiArtIntegrationTest {
 
@@ -16,5 +15,4 @@ public class AsciiArtIntegrationTest {
         
         asciiArt.drawString(text, "*", settings);
     }
-    
 }

core-java-modules/core-java-date-operations-2/README.md

@@ -8,4 +8,5 @@ This module contains articles about date operations in Java.
 - [Converting Java Date to OffsetDateTime](https://www.baeldung.com/java-convert-date-to-offsetdatetime)
 - [How to Set the JVM Time Zone](https://www.baeldung.com/java-jvm-time-zone)
 - [How to determine day of week by passing specific date in Java?](https://www.baeldung.com/java-get-day-of-week)
+- [Finding Leap Years in Java](https://www.baeldung.com/java-leap-year)
 - [[<-- Prev]](/core-java-modules/core-java-date-operations-1)

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

@@ -12,3 +12,4 @@ This module contains articles about working with the Java Virtual Machine (JVM).
 - [Guide to System.gc()](https://www.baeldung.com/java-system-gc)
 - [Runtime.getRuntime().halt() vs System.exit() in Java](https://www.baeldung.com/java-runtime-halt-vs-system-exit)
 - [Adding Shutdown Hooks for JVM Applications](https://www.baeldung.com/jvm-shutdown-hooks)
+- [How to Get the Size of an Object in Java](http://www.baeldung.com/java-size-of-object)

core-java-modules/core-java-lang-syntax/src/test/java/com/baeldung/varargs/HeapPollutionUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.varargs;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class HeapPollutionUnitTest {
+
+    @Test(expected = ClassCastException.class)
+    public void givenGenericVararg_whenUsedUnsafe_shouldThrowClassCastException() {
+        String one = firstOfFirst(Arrays.asList("one", "two"), Collections.emptyList());
+
+        assertEquals("one", one);
+    }
+
+    @Test(expected = ClassCastException.class)
+    public void givenGenericVararg_whenRefEscapes_mayCauseSubtleBugs() {
+        String[] args = returnAsIs("One", "Two");
+    }
+
+    private static String firstOfFirst(List<String>... strings) {
+        List<Integer> ints = Collections.singletonList(42);
+        Object[] objects = strings;
+        objects[0] = ints;
+
+        return strings[0].get(0);
+    }
+
+    private static <T> T[] toArray(T... arguments) {
+        return arguments;
+    }
+
+    private static <T> T[] returnAsIs(T a, T b) {
+        return toArray(a, b);
+    }
+}

core-java-modules/core-java-reflection/README.MD

@@ -8,3 +8,5 @@
 - [Changing Annotation Parameters At Runtime](http://www.baeldung.com/java-reflection-change-annotation-params)
 - [Dynamic Proxies in Java](http://www.baeldung.com/java-dynamic-proxies)
 - [What Causes java.lang.reflect.InvocationTargetException?](https://www.baeldung.com/java-lang-reflect-invocationtargetexception)
+- [How to Find all Getters Returning Null](http://www.baeldung.com/java-getters-returning-null)
+- [How to Get a Name of a Method Being Executed?](http://www.baeldung.com/java-name-of-executing-method)

core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/java/reflection/ReflectionUnitTest.java

@@ -200,7 +200,7 @@ public class ReflectionUnitTest {
     @Test
     public void givenClassField_whenSetsAndGetsValue_thenCorrect() throws Exception {
         final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
-        final Bird bird = (Bird) birdClass.newInstance();
+        final Bird bird = (Bird) birdClass.getConstructor().newInstance();
         final Field field = birdClass.getDeclaredField("walks");
         field.setAccessible(true);
 
@@ -266,7 +266,7 @@ public class ReflectionUnitTest {
     @Test
     public void givenMethod_whenInvokes_thenCorrect() throws Exception {
         final Class<?> birdClass = Class.forName("com.baeldung.java.reflection.Bird");
-        final Bird bird = (Bird) birdClass.newInstance();
+        final Bird bird = (Bird) birdClass.getConstructor().newInstance();
         final Method setWalksMethod = birdClass.getDeclaredMethod("setWalks", boolean.class);
         final Method walksMethod = birdClass.getDeclaredMethod("walks");
         final boolean walks = (boolean) walksMethod.invoke(bird);

core-java-modules/core-java-string-conversions/src/test/java/com/baeldung/stringtoint/StringToIntOrIntegerUnitTest.java

@@ -26,6 +26,17 @@ public class StringToIntOrIntegerUnitTest {
         assertThat(result).isEqualTo(new Integer(42));
     }
 
+    @Test
+    public void givenString_whenCallingValueOf_shouldCacheSomeValues() {
+        for (int i = -128; i <= 127; i++) {
+            String value = i + "";
+            Integer first = Integer.valueOf(value);
+            Integer second = Integer.valueOf(value);
+
+            assertThat(first).isSameAs(second);
+        }
+    }
+
     @Test
     public void givenString_whenCallingIntegerConstructor_shouldConvertToInt() {
         String givenString = "42";

core-java-modules/core-java-string-operations-2/README.md

@@ -12,4 +12,6 @@ This module contains articles about string operations.
 - [L-Trim and R-Trim Alternatives in Java](https://www.baeldung.com/java-trim-alternatives)
 - [Java Convert PDF to Base64](https://www.baeldung.com/java-convert-pdf-to-base64)
 - [Encode a String to UTF-8 in Java](https://www.baeldung.com/java-string-encode-utf-8)
+- [Guide to Character Encoding](https://www.baeldung.com/java-char-encoding)
+- [Convert Hex to ASCII in Java](https://www.baeldung.com/java-convert-hex-to-ascii) #remove additional readme file
 - More articles: [[<-- prev]](../core-java-string-operations)