Generate UUIDs in Java

import java.util.UUID;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class UuidExample {
    public static void main(String[] args) {
        // UUID v4 (random)
        UUID uuid4 = UUID.randomUUID();
        System.out.println(uuid4);  // Example: 3d6f9e64-7d8a-4c3e-8f2b-1a4e5c6d7e8f

        // UUID v3 (namespaced with MD5)
        UUID uuid3 = generateUuidV3("example.com");
        System.out.println(uuid3);  // Always same: 9073926b-929f-31c2-abc9-fad77ae3e8eb

        // Parse UUID from string
        String uuidString = "3d6f9e64-7d8a-4c3e-8f2b-1a4e5c6d7e8f";
        UUID parsed = UUID.fromString(uuidString);
        System.out.println(parsed.version());  // Outputs: 4

        // Generate multiple UUIDs
        for (int i = 0; i < 5; i++) {
            System.out.println(UUID.randomUUID());
        }
    }

    // Helper method for UUID v3 generation
    private static UUID generateUuidV3(String name) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] hash = md.digest(name.getBytes(StandardCharsets.UTF_8));
            hash[6] &= 0x0f;  // Clear version
            hash[6] |= 0x30;  // Set to version 3
            hash[8] &= 0x3f;  // Clear variant
            hash[8] |= 0x80;  // Set to IETF variant
            return UUID.nameUUIDFromBytes(hash);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }
}