From e14feb5351d23b9df5f476e0352a4e0383c10bf5 Mon Sep 17 00:00:00 2001
From: "alexandru.borza" <alexandru.borza@tazz.ro>
Date: Fri, 17 Mar 2023 19:58:29 +0200
Subject: [PATCH] time-based UUIDs

---
 core-java-modules/core-java-uuid/pom.xml      | 17 +++++++-
 .../timebaseduuid/JavaUUIDCreator.java        | 42 +++++++++++++++++++
 .../baeldung/timebaseduuid/UUIDCreator.java   | 41 ++++++++++++++++++
 3 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/JavaUUIDCreator.java
 create mode 100644 core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/UUIDCreator.java

diff --git a/core-java-modules/core-java-uuid/pom.xml b/core-java-modules/core-java-uuid/pom.xml
index 7d851292f5..442a266dab 100644
--- a/core-java-modules/core-java-uuid/pom.xml
+++ b/core-java-modules/core-java-uuid/pom.xml
@@ -25,6 +25,21 @@
             <artifactId>log4j-over-slf4j</artifactId>
             <version>${org.slf4j.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.github.f4b6a3</groupId>
+            <artifactId>uuid-creator</artifactId>
+            <version>5.2.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.uuid</groupId>
+            <artifactId>java-uuid-generator</artifactId>
+            <version>4.1.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.github.f4b6a3</groupId>
+            <artifactId>tsid-creator</artifactId>
+            <version>5.2.3</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -143,4 +158,4 @@
         <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
     </properties>
 
-</project>
\ No newline at end of file
+</project>
diff --git a/core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/JavaUUIDCreator.java b/core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/JavaUUIDCreator.java
new file mode 100644
index 0000000000..39308c8982
--- /dev/null
+++ b/core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/JavaUUIDCreator.java
@@ -0,0 +1,42 @@
+package com.baeldung.timebaseduuid;
+
+import com.fasterxml.uuid.Generators;
+import com.github.f4b6a3.uuid.UuidCreator;
+
+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 JavaUUIDCreator {
+
+    public static void main(String[] args) throws InterruptedException {
+
+        int threadCount = 128;
+        int iterationCount = 100_000;
+        ConcurrentMap<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++) {
+            final 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");
+    }
+}
diff --git a/core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/UUIDCreator.java b/core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/UUIDCreator.java
new file mode 100644
index 0000000000..8695a54bae
--- /dev/null
+++ b/core-java-modules/core-java-uuid/src/main/java/com/baeldung/timebaseduuid/UUIDCreator.java
@@ -0,0 +1,41 @@
+package com.baeldung.timebaseduuid;
+
+import com.github.f4b6a3.uuid.UuidCreator;
+
+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 UUIDCreator {
+
+    public static void main(String[] args) throws InterruptedException {
+
+        int threadCount = 128;
+        int iterationCount = 100_000;
+        ConcurrentMap<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++) {
+            final 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");
+    }
+}