sequential UUID using current time.Based on https://blog.2ndquadrant.com/sequential-uuid-generators/

UUIDUtils.java

package uuid;

import java.nio.ByteBuffer;
import java.security.SecureRandom;
import java.time.Instant;
import java.util.UUID;

public class OtherUUIDUtil {

	private static final int UUID_LENGTH = 16;
	private static final int DEFAULT_INTERVAL_LENGTH = 60;
	private static final int DEFAULT_INTERAVL_COUNT = 65536;
	private static volatile SecureRandom numberGenerator = null;

	/**
	 * Static factory to generate sequential UUID using current time
	 * <p>
	 * The timestamp-based sequential UUID generator define the group size and group
	 * count based on data extracted from current timestamp.
	 * <p>
	 * The interval_length (60 seconds by default) is defined as number of seconds
	 * where UUIDs share the same prefix). The prefix length is determined by the
	 * number of intervals (65536 by default, i.e. 2B). With these parameters the
	 * generator wraps around every ~45 days.
	 *
	 * @return A sequentialy generated {@code UUID} using current time
	 */
	public static UUID timeUUID() {
		return timeUUID(DEFAULT_INTERVAL_LENGTH, DEFAULT_INTERAVL_COUNT);
	}

	/**
	 * Static factory to generate sequential UUID using current time
	 * <p>
	 * The timestamp-based sequential UUID generator define the group size and group
	 * count based on data extracted from current timestamp.
	 *
	 * @param intervalLength
	 *            The number of seconds where {@code UUID} share the same prefix
	 * @param intervalCount
	 *            Used to derive the prefix length
	 * @return A sequentialy generated {@code UUID} using current time
	 */
	public static UUID timeUUID(int intervalLength, int intervalCount) {
		assert intervalLength > 1 : "length of interval must be a positive integer";
		assert intervalCount > 1 : "number of intervals must be a positive integer";

		SecureRandom ng = numberGenerator;
		if (ng == null)
			numberGenerator = ng = new SecureRandom();

		int i;
		ByteBuffer buffer = ByteBuffer.allocate(UUID_LENGTH);
		long epoch = Instant.now().getEpochSecond();
		byte[] val = longToTwoLeastSignificantBytes(epoch / intervalLength);

		int prefixBytes = 0;
		while (intervalCount > 1) {
			intervalCount /= 256;
			prefixBytes++;
		}

		for (i = 0; i < prefixBytes; i++)
			buffer.put(i, val[prefixBytes - 1 - i]);

		byte[] randomBytes = new byte[UUID_LENGTH - prefixBytes];
		ng.nextBytes(randomBytes);
		for (i = 0; i < randomBytes.length; i++)
			buffer.put(i + prefixBytes, randomBytes[i]);

		return new UUID(buffer.getLong(), buffer.getLong());
	}

	public static byte[] longToTwoLeastSignificantBytes(long l) {
		byte[] result = new byte[2];
		result[0] = (byte) (l & 0xFF);
		result[1] = (byte) ((l >> 8) & 0xFF);
		return result;
	}
}