Merge remote-tracking branch 'Baeldung/master' into active_mq

# Conflicts: # .gitignore # LICENSE # README.md # core-java-modules/README.md # core-java-modules/core-java-11/README.md # core-java-modules/core-java-11/pom.xml # core-java-modules/core-java-8/README.md # core-java-modules/core-java-8/pom.xml # core-java-modules/core-java-8/src/main/resources/logback.xml # core-java-modules/core-java-annotations/README.md # core-java-modules/core-java-annotations/pom.xml # core-java-modules/core-java-collections-2/README.md # core-java-modules/core-java-collections-2/pom.xml # core-java-modules/core-java-collections-3/README.md # core-java-modules/core-java-collections-3/pom.xml # core-java-modules/core-java-collections-conversions-2/README.md # core-java-modules/core-java-collections-conversions-2/pom.xml # core-java-modules/core-java-collections-conversions/README.md # core-java-modules/core-java-collections-conversions/pom.xml # core-java-modules/core-java-collections-list/README.md # core-java-modules/core-java-collections-list/pom.xml # core-java-modules/core-java-collections/pom.xml # core-java-modules/core-java-datetime-conversion/README.md # core-java-modules/core-java-datetime-conversion/pom.xml # core-java-modules/core-java-datetime-conversion/src/test/java/com/baeldung/datetime/ConvertInstantToTimestampUnitTest.java # core-java-modules/core-java-io-2/pom.xml # core-java-modules/core-java-io/README.md # core-java-modules/core-java-io/pom.xml # core-java-modules/core-java-io/src/test/resources/fileTest.txt # core-java-modules/core-java-io/src/test/resources/sampleTextFile.txt # core-java-modules/core-java-lambdas/README.md # core-java-modules/core-java-lambdas/pom.xml # core-java-modules/core-java-serialization/pom.xml # core-java-modules/core-java-streams/README.md # core-java-modules/core-java-streams/pom.xml # core-java-modules/core-java-strings/README.md # core-java-modules/core-java-strings/pom.xml # core-java-modules/core-java-strings/src/test/resources/stringtoolong.txt # core-java-modules/core-java-uuid/README.md # core-java-modules/core-java-uuid/pom.xml # core-java-modules/pom.xml # image-processing/README.md # image-processing/pom.xml # image-processing/src/main/java/com/baeldung/imageprocessing/addingtext/AddText.java # image-processing/src/main/java/com/baeldung/imageprocessing/opencv/CameraStream.java # jackson-modules/jackson-annotations/README.md # jackson-modules/jackson-annotations/pom.xml # jackson-modules/jackson-conversions-2/README.md # jackson-modules/jackson-conversions-2/pom.xml # jackson-modules/jackson-conversions/README.md # jackson-modules/jackson-conversions/pom.xml # jackson-modules/jackson-custom-conversions/README.md # jackson-modules/jackson-custom-conversions/pom.xml # jackson-modules/jackson-custom-conversions/src/test/java/com/baeldung/defaultserializercustomserializer/CallingDefaultSerializerUnitTest.java # jackson-modules/jackson-custom-conversions/src/test/java/com/baeldung/deserialization/CustomDeserializationUnitTest.java # jackson-modules/jackson-exceptions/README.md # jackson-modules/jackson-exceptions/pom.xml # jackson-modules/jackson-exceptions/src/test/java/com/baeldung/exceptions/JacksonExceptionsUnitTest.java # jackson-modules/jackson-exceptions/src/test/java/com/baeldung/mappingexception/JacksonMappingExceptionUnitTest.java # jackson-modules/pom.xml # parent-boot-1/pom.xml # parent-boot-2/pom.xml # parent-boot-3/pom.xml # patterns-modules/design-patterns-architectural/pom.xml # patterns-modules/design-patterns-architectural/src/main/java/com/baeldung/repositoryvsdaopattern/UserDaoImpl.java # patterns-modules/design-patterns-behavioral-2/README.md # patterns-modules/design-patterns-behavioral-2/pom.xml # patterns-modules/design-patterns-creational-2/README.md # patterns-modules/design-patterns-creational-2/pom.xml # patterns-modules/design-patterns-singleton/README.md # patterns-modules/design-patterns-structural/src/main/resources/log4jstructuraldp.properties # patterns-modules/enterprise-patterns/pom.xml # patterns-modules/intercepting-filter/pom.xml # patterns-modules/pom.xml # persistence-modules/activejdbc/pom.xml # persistence-modules/hibernate5/README.md # persistence-modules/hibernate5/pom.xml # persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/interceptors/CustomInterceptor.java # persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/interceptors/entity/User.java # persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/namingstrategy/CustomPhysicalNamingStrategy.java # persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/persistjson/Customer.java # persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/persistjson/HashMapConverter.java # persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/pojo/OrderEntryIdClass.java # persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/pojo/OrderEntryPK.java # persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/IdentifiersIntegrationTest.java # persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/bootstrap/BootstrapAPIIntegrationTest.java # persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/proxy/HibernateProxyUnitTest.java # persistence-modules/hibernate5/src/test/resources/hibernate-interceptors.properties # persistence-modules/hibernate5/src/test/resources/hibernate-lifecycle.properties # persistence-modules/hibernate5/src/test/resources/hibernate-namingstrategy.properties # persistence-modules/hibernate5/src/test/resources/hibernate-persistjson.properties # persistence-modules/hibernate5/src/test/resources/hibernate.properties # persistence-modules/pom.xml # persistence-modules/spring-data-jpa-crud/pom.xml # persistence-modules/spring-data-jpa-crud/src/main/java/com/baeldung/repository/FruitRepository.java # persistence-modules/spring-data-jpa-repo-2/README.md # persistence-modules/spring-data-jpa-repo-2/pom.xml # persistence-modules/spring-data-jpa-repo-2/src/main/java/com/baeldung/spring/data/persistence/customrepository/model/User.java # persistence-modules/spring-data-jpa-repo-2/src/main/java/com/baeldung/spring/data/persistence/customrepository/repository/CustomUserRepositoryImpl.java # persistence-modules/spring-data-jpa-repo-2/src/main/java/com/baeldung/spring/data/persistence/saveperformance/Book.java # persistence-modules/spring-data-jpa-repo-2/src/main/resources/application.properties # persistence-modules/spring-data-mongodb-reactive/pom.xml # persistence-modules/spring-data-redis/README.md # persistence-modules/spring-data-redis/pom.xml # persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/reactive/redis/config/RedisConfig.java # persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/redis/config/RedisConfig.java # persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/redis/model/Student.java # persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/redis/queue/RedisMessageSubscriber.java # persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/reactive/redis/template/RedisKeyCommandsManualTest.java # persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/reactive/redis/template/RedisTemplateListOpsManualTest.java # persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/reactive/redis/template/RedisTemplateValueOpsManualTest.java # persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/redis/repo/StudentRepositoryManualTest.java # pom.xml # testing-modules/assertion-libraries/README.md # testing-modules/assertion-libraries/pom.xml # testing-modules/junit-5-basics/README.md # testing-modules/junit-5-basics/pom.xml # testing-modules/mockito-2/src/main/java/com/baeldung/nullmatcher/Helper.java # testing-modules/mockito-2/src/main/java/com/baeldung/nullmatcher/Main.java # testing-modules/mockito-2/src/main/java/com/baeldung/wantedbutnotinvocked/Helper.java # testing-modules/mockito-2/src/main/java/com/baeldung/wantedbutnotinvocked/Main.java # testing-modules/mockito-2/src/test/java/com/baeldung/nullmatcher/MainUnitTest.java # testing-modules/mockito-2/src/test/java/com/baeldung/wantedbutnotinvocked/MainUnitTest.java # testing-modules/pom.xml # testing-modules/spring-mockito/pom.xml # web-modules/dropwizard/pom.xml # web-modules/jakarta-ee/README.md # web-modules/jakarta-ee/pom.xml # web-modules/jakarta-ee/src/test/java/com/baeldung/eclipse/krazo/UserControllerUnitTest.java # web-modules/java-lite/pom.xml # web-modules/javax-servlets-2/README.md # web-modules/javax-servlets-2/pom.xml # web-modules/javax-servlets/pom.xml # web-modules/jee-7/pom.xml # web-modules/jooby/pom.xml # web-modules/ninja/pom.xml # web-modules/pom.xml # web-modules/ratpack/pom.xml # web-modules/resteasy/pom.xml # web-modules/restx/pom.xml # web-modules/spark-java/pom.xml # web-modules/vraptor/pom.xml # xml/README.md # xml/pom.xml # xml/src/main/resources/customer-binding.xml # xml/src/main/resources/sax/baeldung.xml # xml/src/test/resources/example_default_parser.xml # xml/src/test/resources/example_dom4j.xml # xml/src/test/resources/example_jaxb.xml # xml/src/test/resources/example_jaxen.xml # xml/src/test/resources/example_jdom.xml # xml/src/test/resources/example_stax.xml # xml/src/test/resources/sax/baeldung.xml # xml/src/test/resources/xml/websites.xml # xml/src/test/resources/xml/xee_attribute.xml
2024-04-30 12:23:19 -04:00
parent c18eb6d2ed 8cabe509a5
commit a51b7b55d9
27985 changed files with 1584039 additions and 0 deletions
@@ -0,0 +1,42 @@
+package com.baeldung.timebaseduuid;
+
+import com.fasterxml.uuid.Generators;
+
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+
+public class JavaUUIDCreatorBenchmark {
+
+public static void main(String[] args) throws InterruptedException {
+
+    int threadCount = 128;
+    int iterationCount = 100_000;
+    Map<UUID, Long> uuidMap = new ConcurrentHashMap<>();
+    AtomicLong collisionCount = new AtomicLong();
+    long startNanos = System.nanoTime();
+    CountDownLatch endLatch = new CountDownLatch(threadCount);
+
+    for (long i = 0; i < threadCount; i++) {
+        long threadId = i;
+        new Thread(() -> {
+            for (long j = 0; j < iterationCount; j++) {
+                UUID uuid = Generators.timeBasedGenerator().generate();
+                Long existingUUID = uuidMap.put(uuid, (threadId * iterationCount) + j);
+                if(existingUUID != null) {
+                    collisionCount.incrementAndGet();
+                }
+            }
+            endLatch.countDown();
+        }).start();
+    }
+
+    endLatch.await();
+    System.out.println(threadCount * iterationCount + " UUIDs generated, " + collisionCount + " collisions in "
+            + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos) + "ms");
+}
+}
+
@@ -0,0 +1,13 @@
+package com.baeldung.timebaseduuid;
+
+import com.fasterxml.uuid.Generators;
+
+public class JavaUUIDCreatorExample {
+
+    public static void main(String[] args) {
+        System.out.println("UUID Version 1: " + Generators.timeBasedGenerator().generate());
+        System.out.println("UUID Version 6: " + Generators.timeBasedReorderedGenerator().generate());
+        System.out.println("UUID Version 7: " + Generators.timeBasedEpochGenerator().generate());
+
+    }
+}
@@ -0,0 +1,42 @@
+package com.baeldung.timebaseduuid;
+
+import com.github.f4b6a3.uuid.UuidCreator;
+
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+
+public class UUIDCreatorBenchmark {
+
+    public static void main(String[] args) throws InterruptedException {
+
+        int threadCount = 128;
+        int iterationCount = 100_000;
+        Map<UUID, Long> uuidMap = new ConcurrentHashMap<>();
+        AtomicLong collisionCount = new AtomicLong();
+        long startNanos = System.nanoTime();
+        CountDownLatch endLatch = new CountDownLatch(threadCount);
+
+        for (long i = 0; i < threadCount; i++) {
+            long threadId = i;
+            new Thread(() -> {
+                for (long j = 0; j < iterationCount; j++) {
+                    UUID uuid = UuidCreator.getTimeBased();
+                    Long existingUUID = uuidMap.put(uuid, (threadId * iterationCount) + j);
+                    if(existingUUID != null) {
+                        collisionCount.incrementAndGet();
+                    }
+                }
+                endLatch.countDown();
+            }).start();
+        }
+
+        endLatch.await();
+        System.out.println(threadCount * iterationCount + " UUIDs generated, " + collisionCount + " collisions in "
+                + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos) + "ms");
+    }
+}
@@ -0,0 +1,13 @@
+package com.baeldung.timebaseduuid;
+
+import com.github.f4b6a3.uuid.UuidCreator;
+
+public class UUIDCreatorExample {
+
+    public static void main(String[] args) {
+        System.out.println("UUID Version 1: " + UuidCreator.getTimeBased());
+        System.out.println("UUID Version 6: " + UuidCreator.getTimeOrdered());
+        System.out.println("UUID Version 7: " + UuidCreator.getTimeOrderedEpoch());
+    }
+}
+
@@ -0,0 +1,164 @@
+package com.baeldung.uuid;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
+import java.util.Random;
+import java.util.UUID;
+
+public final class UUIDGenerator {
+
+    private static final char[] hexArray = "0123456789ABCDEF".toCharArray();
+
+    private UUIDGenerator() {
+    }
+
+    /**
+     * Type 1 UUID Generation
+     */
+    public static UUID generateType1UUID() {
+
+        final long most64SigBits = get64MostSignificantBitsForVersion1();
+        final long least64SigBits = get64LeastSignificantBitsForVersion1();
+
+        return new UUID(most64SigBits, least64SigBits);
+    }
+
+    private static long get64LeastSignificantBitsForVersion1() {
+        final long random63BitLong = new Random().nextLong() & 0x3FFFFFFFFFFFFFFFL;
+        long variant3BitFlag = 0x8000000000000000L;
+        return random63BitLong | variant3BitFlag;
+    }
+
+    private static long get64MostSignificantBitsForVersion1() {
+        final long currentTimeMillis = System.currentTimeMillis();
+        final long time_low = (currentTimeMillis & 0x0000_0000_FFFF_FFFFL) << 32;
+        final long time_mid = ((currentTimeMillis >> 32) & 0xFFFF) << 16;
+        final long version = 1 << 12;
+        final long time_high = ((currentTimeMillis >> 48) & 0x0FFF);
+        return time_low | time_mid | version | time_high;
+    }
+
+    /**
+     * Type 3 UUID Generation
+     */
+    public static UUID generateType3UUID(String namespace, String name) {
+
+        final byte[] nameSpaceBytes = bytesFromUUID(namespace);
+        final byte[] nameBytes = name.getBytes(StandardCharsets.UTF_8);
+        final byte[] result = joinBytes(nameSpaceBytes, nameBytes);
+
+        return UUID.nameUUIDFromBytes(result);
+    }
+
+    /**
+     * Type 4 UUID Generation
+     */
+    public static UUID generateType4UUID() {
+        return UUID.randomUUID();
+    }
+
+    /**
+     * Type 5 UUID Generation
+     */
+    public static UUID generateType5UUID(String namespace, String name) {
+
+        final byte[] nameSpaceBytes = bytesFromUUID(namespace);
+        final byte[] nameBytes = name.getBytes(StandardCharsets.UTF_8);
+        final byte[] result = joinBytes(nameSpaceBytes, nameBytes);
+
+        return type5UUIDFromBytes(result);
+    }
+
+    public static UUID type5UUIDFromBytes(byte[] name) {
+        final MessageDigest md;
+        try {
+            md = MessageDigest.getInstance("SHA-1");
+        } catch (NoSuchAlgorithmException exception) {
+            throw new InternalError("SHA-1 not supported", exception);
+        }
+        final byte[] bytes = Arrays.copyOfRange(md.digest(name), 0, 16);
+        bytes[6] &= 0x0f; /* clear version        */
+        bytes[6] |= 0x50; /* set to version 5     */
+        bytes[8] &= 0x3f; /* clear variant        */
+        bytes[8] |= 0x80; /* set to IETF variant  */
+        return constructType5UUID(bytes);
+    }
+
+    private static UUID constructType5UUID(byte[] data) {
+        long msb = 0;
+        long lsb = 0;
+        assert data.length == 16 : "data must be 16 bytes in length";
+
+        for (int i = 0; i < 8; i++) {
+            msb = (msb << 8) | (data[i] & 0xff);
+        }
+
+        for (int i = 8; i < 16; i++) {
+            lsb = (lsb << 8) | (data[i] & 0xff);
+        }
+        return new UUID(msb, lsb);
+    }
+
+    private static byte[] bytesFromUUID(String uuidHexString) {
+        final String normalizedUUIDHexString = uuidHexString.replace("-", "");
+
+        assert normalizedUUIDHexString.length() == 32;
+
+        final byte[] bytes = new byte[16];
+        for (int i = 0; i < 16; i++) {
+            final byte b = hexToByte(normalizedUUIDHexString.substring(i * 2, i * 2 + 2));
+            bytes[i] = b;
+        }
+        return bytes;
+    }
+
+    public static byte hexToByte(String hexString) {
+        final int firstDigit = Character.digit(hexString.charAt(0), 16);
+        final int secondDigit = Character.digit(hexString.charAt(1), 16);
+        return (byte) ((firstDigit << 4) + secondDigit);
+    }
+
+    public static byte[] joinBytes(byte[] byteArray1, byte[] byteArray2) {
+        final int finalLength = byteArray1.length + byteArray2.length;
+        final byte[] result = new byte[finalLength];
+
+        System.arraycopy(byteArray1, 0, result, 0, byteArray1.length);
+        System.arraycopy(byteArray2, 0, result, byteArray1.length, byteArray2.length);
+        return result;
+    }
+
+    public static UUID generateType5UUID(String name) {
+
+        try {
+
+            final byte[] bytes = name.getBytes(StandardCharsets.UTF_8);
+            final MessageDigest md = MessageDigest.getInstance("SHA-1");
+
+            final byte[] hash = md.digest(bytes);
+
+            long msb = getLeastAndMostSignificantBitsVersion5(hash, 0);
+            long lsb = getLeastAndMostSignificantBitsVersion5(hash, 8);
+            // Set the version field
+            msb &= ~(0xfL << 12);
+            msb |= 5L << 12;
+            // Set the variant field to 2
+            lsb &= ~(0x3L << 62);
+            lsb |= 2L << 62;
+            return new UUID(msb, lsb);
+
+        } catch (NoSuchAlgorithmException e) {
+            throw new AssertionError(e);
+        }
+    }
+
+    private static long getLeastAndMostSignificantBitsVersion5(final byte[] src, final int offset) {
+        long ans = 0;
+        for (int i = offset + 7; i >= offset; i -= 1) {
+            ans <<= 8;
+            ans |= src[i] & 0xffL;
+        }
+        return ans;
+    }
+}
@@ -0,0 +1,64 @@
+package com.baeldung.uuid;
+
+import static org.apache.commons.codec.binary.Base64.decodeBase64;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.ByteBuffer;
+import java.util.Base64;
+import java.util.UUID;
+
+import org.apache.commons.lang3.Conversion;
+import org.junit.jupiter.api.Test;
+
+public class DecodeUUIDStringFromBase64UnitTest {
+    private final UUID originalUUID = UUID.fromString("cc5f93f7-8cf1-4a51-83c6-e740313a0c6c");
+
+    @Test
+    public void givenEncodedString_whenDecodingUsingBase64Decoder_thenGiveExpectedUUID() {
+        String expectedEncodedString = "UUrxjPeTX8xsDDoxQOfGgw";
+        byte[] decodedBytes = Base64.getDecoder()
+          .decode(expectedEncodedString);
+        UUID uuid = convertToUUID(decodedBytes);
+        assertEquals(originalUUID, uuid);
+    }
+
+    @Test
+    public void givenEncodedString_whenDecodingUsingByteBufferAndBase64UrlDecoder_thenGiveExpectedUUID() {
+        String expectedEncodedString = "zF-T94zxSlGDxudAMToMbA";
+        byte[] decodedBytes = Base64.getUrlDecoder()
+          .decode(expectedEncodedString);
+        ByteBuffer byteBuffer = ByteBuffer.wrap(decodedBytes);
+        long mostSignificantBits = byteBuffer.getLong();
+        long leastSignificantBits = byteBuffer.getLong();
+        UUID uuid = new UUID(mostSignificantBits, leastSignificantBits);
+        assertEquals(originalUUID, uuid);
+    }
+
+    @Test
+    public void givenEncodedString_whenDecodingUsingApacheUtils_thenGiveExpectedUUID() {
+        String expectedEncodedString = "UUrxjPeTX8xsDDoxQOfGgw";
+        byte[] decodedBytes = decodeBase64(expectedEncodedString);
+        UUID uuid = Conversion.byteArrayToUuid(decodedBytes, 0);
+        assertEquals(originalUUID, uuid);
+    }
+
+    private UUID convertToUUID(byte[] src) {
+        long mostSignificantBits = convertBytesToLong(src, 0);
+        long leastSignificantBits = convertBytesToLong(src, 8);
+
+        return new UUID(mostSignificantBits, leastSignificantBits);
+    }
+
+    private long convertBytesToLong(byte[] uuidBytes, int start) {
+        long result = 0;
+
+        for(int i = 0; i < 8; i++) {
+            int shift = i * 8;
+            long bits = (255L & (long)uuidBytes[i + start]) << shift;
+            long mask = 255L << shift;
+            result = result & ~mask | bits;
+        }
+
+        return result;
+    }
+}
@@ -0,0 +1,62 @@
+package com.baeldung.uuid;
+
+import static org.apache.commons.codec.binary.Base64.encodeBase64URLSafeString;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.ByteBuffer;
+import java.util.Base64;
+import java.util.UUID;
+
+import org.apache.commons.lang3.Conversion;
+import org.junit.jupiter.api.Test;
+
+public class EncodeUUIDToBase64StringUnitTest {
+    private final UUID originalUUID = UUID.fromString("cc5f93f7-8cf1-4a51-83c6-e740313a0c6c");
+
+    @Test
+    public void givenUUID_whenEncodingUsingBase64Encoder_thenGiveExpectedEncodedString() {
+        String expectedEncodedString = "UUrxjPeTX8xsDDoxQOfGgw";
+        byte[] uuidBytes = convertToByteArray(originalUUID);
+        String encodedUUID = Base64.getEncoder().withoutPadding()
+          .encodeToString(uuidBytes);
+        assertEquals(expectedEncodedString, encodedUUID);
+    }
+
+    @Test
+    public void givenUUID_whenEncodingUsingByteBufferAndBase64UrlEncoder_thenGiveExpectedEncodedString() {
+        String expectedEncodedString = "zF-T94zxSlGDxudAMToMbA";
+        ByteBuffer byteBuffer = ByteBuffer.wrap(new byte[16]);
+        byteBuffer.putLong(originalUUID.getMostSignificantBits());
+        byteBuffer.putLong(originalUUID.getLeastSignificantBits());
+        String encodedUUID = Base64.getUrlEncoder().withoutPadding()
+          .encodeToString(byteBuffer.array());
+        assertEquals(expectedEncodedString, encodedUUID);
+    }
+
+    @Test
+    public void givenUUID_whenEncodingUsingApacheUtils_thenGiveExpectedEncodedString() {
+        String expectedEncodedString = "UUrxjPeTX8xsDDoxQOfGgw";
+        byte[] bytes = Conversion.uuidToByteArray(originalUUID, new byte[16], 0, 16);
+        String encodedUUID = encodeBase64URLSafeString(bytes);
+        assertEquals(expectedEncodedString, encodedUUID);
+    }
+
+    private byte[] convertToByteArray(UUID uuid) {
+        byte[] result = new byte[16];
+
+        long mostSignificantBits = uuid.getMostSignificantBits();
+        fillByteArray(0, 8, result, mostSignificantBits);
+
+        long leastSignificantBits = uuid.getLeastSignificantBits();
+        fillByteArray(8, 16, result, leastSignificantBits);
+
+        return result;
+    }
+
+    private static void fillByteArray(int start, int end, byte[] result, long bits) {
+        for (int i = start; i < end; i++) {
+            int shift = i * 8;
+            result[i] = (byte) ((int) (255L & bits >> shift));
+        }
+    }
+}
@@ -0,0 +1,62 @@
+package com.baeldung.uuid;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class UUIDFromStringUnitTest {
+    @Test
+    void whenStringInUUIDFormat_thenFromStringWorks() {
+        String inputStr = "bbcc4621-d88f-4a94-ae2f-b38072bf5087";
+        
+        UUID uuid = UUID.fromString(inputStr);
+        UUID uuid2 = UUID.fromString(inputStr);
+        UUID uuid3 = UUID.fromString(inputStr);
+
+        assertEquals(inputStr, uuid.toString());
+
+        assertEquals(uuid, uuid2);
+        assertEquals(uuid, uuid3);
+
+    }
+
+    @Test
+    void whenStringNotInUUIDFormat_thenFromStringRaisesException() {
+        String inputStr = "I am not a standard UUID representation.";
+        assertThrows(IllegalArgumentException.class, () -> UUID.fromString(inputStr));
+    }
+
+    @Test
+    void whenStringInFreeFormat_thenNameUUIDFromBytesWorks() {
+        String inputStr = "I am not a standard UUID representation.";
+
+        UUID uuid = UUID.nameUUIDFromBytes(inputStr.getBytes());
+        UUID uuid2 = UUID.nameUUIDFromBytes(inputStr.getBytes());
+        UUID uuid3 = UUID.nameUUIDFromBytes(inputStr.getBytes());
+
+        assertTrue(uuid != null);
+
+        assertEquals(uuid, uuid2);
+        assertEquals(uuid, uuid3);
+
+        assertEquals(3, uuid.version());
+    }
+
+    @Test
+    void whenStringInFreeFormat_thenGenerateVer5UUIDWorks() {
+        String inputStr = "I am not a standard UUID representation.";
+
+        UUID uuid = UUIDGenerator.generateType5UUID(inputStr);
+        UUID uuid2 = UUIDGenerator.generateType5UUID(inputStr);
+        UUID uuid3 = UUIDGenerator.generateType5UUID(inputStr);
+
+        assertEquals(5, uuid.version());
+
+        assertTrue(uuid != null);
+
+        assertEquals(uuid, uuid2);
+        assertEquals(uuid, uuid3);
+    }
+}
@@ -0,0 +1,84 @@
+package com.baeldung.uuid;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.UnsupportedEncodingException;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class UUIDGeneratorUnitTest {
+
+    private static final String NAMESPACE_URL = "6ba7b811-9dad-11d1-80b4-00c04fd430c8";
+    private static final String NAMESPACE_DNS = "6ba7b810-9dad-11d1-80b4-00c04fd430c8";
+
+    @Test
+    void shouldGenerateType1UUIDWithCorrectVersionAndVariant() {
+        UUID uuid = UUIDGenerator.generateType1UUID();
+        assertEquals(36, uuid.toString().length());
+        assertEquals(1, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    void shouldGenerateType1UUIDWithTheCurrentDate() {
+        UUID uuid = UUIDGenerator.generateType1UUID();
+        long time = uuid.timestamp();
+        LocalDateTime dateTime = LocalDateTime.ofInstant(Instant.ofEpochMilli(time), ZoneId.systemDefault());
+        assertEquals(LocalDate.now(), dateTime.toLocalDate());
+    }
+
+    @Test
+    void version_3_UUID_is_correctly_generated_for_domain_baeldung_com() {
+
+        UUID uuid = UUIDGenerator.generateType3UUID(NAMESPACE_DNS, "baeldung.com");
+
+        assertEquals("23785b78-0132-3ac6-aff6-cfd5be162139", uuid.toString());
+        assertEquals(3, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    void version_3_UUID_is_correctly_generated_for_domain_d() {
+
+        UUID uuid = UUIDGenerator.generateType3UUID(NAMESPACE_DNS, "d");
+
+        assertEquals("dbd41ecb-f466-33de-b309-1468addfc63b", uuid.toString());
+        assertEquals(3, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_4_UUID_is_generated_with_correct_length_version_and_variant() {
+
+        UUID uuid = UUIDGenerator.generateType4UUID();
+
+        assertEquals(36, uuid.toString().length());
+        assertEquals(4, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_5_UUID_is_correctly_generated_for_domain_baeldung_com() throws UnsupportedEncodingException {
+
+        UUID uuid = UUIDGenerator.generateType5UUID(NAMESPACE_URL, "baeldung.com");
+
+        assertEquals("aeff44a5-8a61-52b6-bcbe-c8e5bd7d0300", uuid.toString());
+        assertEquals(5, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+
+    @Test
+    public void version_5_UUID_is_correctly_generated_for_domain_baeldung_name() {
+
+        UUID uuid = UUIDGenerator.generateType5UUID("baeldung.com");
+
+        assertEquals("efd5462b-b07a-52a3-94ea-bf575c0e0e75", uuid.toString());
+        assertEquals(5, uuid.version());
+        assertEquals(2, uuid.variant());
+    }
+}
@@ -0,0 +1,22 @@
+package com.baeldung.uuid;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class UUIDPositiveLongGeneratorUnitTest {
+
+    @Test
+    public void whenGetMostSignificantBits_thenAssertPositive() {
+        long randomPositiveLong = Math.abs(UUID.randomUUID().getMostSignificantBits());
+        assertThat(randomPositiveLong).isNotNegative();
+    }
+
+    @Test
+    public void whenGetLeastSignificantBits_thenAssertPositive() {
+        long randomPositiveLong = Math.abs(UUID.randomUUID().getLeastSignificantBits());
+        assertThat(randomPositiveLong).isNotNegative();
+    }
+}
@@ -0,0 +1,29 @@
+package com.baeldung.uuid;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.UUID;
+import java.util.regex.Pattern;
+
+public class UUIDValidatorUnitTest {
+
+  @Test
+  public void whenValidUUIDStringIsValidated_thenValidationSucceeds() {
+    String validUUID = "26929514-237c-11ed-861d-0242ac120002";
+    Assertions.assertEquals(UUID.fromString(validUUID).toString(), validUUID);
+
+    String invalidUUID = "invalid-uuid";
+    Assertions.assertThrows(IllegalArgumentException.class, () -> UUID.fromString(invalidUUID));
+  }
+
+  @Test
+  public void whenUUIDIsValidatedUsingRegex_thenValidationSucceeds() {
+    Pattern UUID_REGEX =
+        Pattern.compile("^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$");
+
+    Assertions.assertTrue(UUID_REGEX.matcher("26929514-237c-11ed-861d-0242ac120002").matches());
+
+    Assertions.assertFalse(UUID_REGEX.matcher("invalid-uuid").matches());
+  }
+}