How do I create a unique ID in Java?

Numeric ID generation: AtomicLong

For those who like it one step at a time, AtomicLong is your way to create simple, sequential numeric IDs:

AtomicLong counter = new AtomicLong();
long numericID = counter.getAndIncrement(); // Pop! Goes the counter
String uniqueNumericID = String.valueOf(numericID); // Convert long to String; like turning water into wine, amirite?


Key: AtomicLong.getAndIncrement()
Output: Incremental, thread-safe long ID converted to String because, strings attached!

Sync or swim: Thread safety in custom ID generators

Going rogue with custom ID generation? Here’s how to keep it swim in the thread pool:

private long customIdCounter = 0;

public synchronized long nextId() {
  // All aboard the ID train, one ticket at a time!
  return customIdCounter++;
}


Key: synchronized
Output: A thread-safe custom ID. Single line, no crowd rush!

Time n' Host: Crafting Unique IDs in Distributed Systems

Ticking clocks and IP addresses are great spice for your ID salad. How about adding some flavor to it:

long timeComponent = System.currentTimeMillis(); // Time waits for no ID!
String hostAddress = InetAddress.getLocalHost().getHostAddress(); // Hey, who is the host?
String customID = timeComponent + "-" + hostAddress + "-" + UUID.randomUUID().toString(); // Voila, Chef's special!


Key: System.currentTimeMillis() and InetAddress.getLocalHost().getHostAddress()
Output: A blend of time, host, and UUID. Savory!

The beauty of randomness: UUID.randomUUID()

To understand the magic behind the UUID.randomUUID(), imagine being at a lottery. Everyone has a unique ticket, waiting for the lucky draw.

Each ticket is a combo of numbers (🔢) and letters (🔡) - just like a UUID in Java.

Here we go, drumroll please!

UUID uniqueKey = UUID.randomUUID();  // Et Voila, your unique ticket to the lottery!


In this lottery of unique IDs, every ticket is a winner!

Unique IDs: [🎟️1a2b, 🎟️3c4d, 🎟️5e6f, ...]
// Each 🎟️ has its own unique combination, just like a UUID in Java.

Enjoy the show and thank the UUID class for making this happen. Here's how UUID spins the lottery wheel:

A closer look at UUID

• The UUID.randomUUID() leverages SecureRandom to churn out unique IDs. So, you can rest assured there are no backstage interventions!
• The UUID.randomUUID().toString() gives you a String, ready for display. No additional libraries needed - it's all included in your Java ticket price!
• The format? It offers you a 16-byte (128-bit) number in a recognizable 8-4-4-4-12 pattern of hexadecimal digits to feast your eyes on!

Pitfalls and perfecting custom IDs

• If you're leaning on AtomicLong, consider its climbing capability. Like an eager hiker, it might run out of mountain, so plan for its potential overflow.
• Make sure your custom ID solutions are battle-tested. Performing in a synchronized ballet is different from free dancing in a multi-threaded environment.
• Getting host details might reveal some network surprises. Keep in mind the shape-shifting nature of host identity in containerized environments.