src/com/my/sociality/utils/UUIDUtils.java

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package com.my.sociality.utils;




import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.Random;
import java.util.UUID;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Helper for creating random and Type 1 (time-based) UUIDs.
 *
 * @author xuan.chen
 */
public class UUIDUtils {

	private static boolean IS_THREADLOCALRANDOM_AVAILABLE = false;
	private static Random random;
	private static final long leastSigBits;
	private static final ReentrantLock lock = new ReentrantLock();
	private static long lastTime;

	static {
		try {
			IS_THREADLOCALRANDOM_AVAILABLE = null != UUIDUtils.class.getClassLoader().loadClass(
					"java.util.concurrent.ThreadLocalRandom");
		} catch (ClassNotFoundException e) {
		}

		byte[] seed = new SecureRandom().generateSeed(8);
		leastSigBits = new BigInteger(seed).longValue();
		if (!IS_THREADLOCALRANDOM_AVAILABLE) {
			random = new Random(leastSigBits);
		}
	}

	private UUIDUtils() {
	}

	/**
	 * Create a new random UUID.
	 *
	 * @return the new UUID
	 */
	public static String random() {
		byte[] randomBytes = new byte[16];
		if (IS_THREADLOCALRANDOM_AVAILABLE) {
			java.util.concurrent.ThreadLocalRandom.current().nextBytes(randomBytes);
		} else {
			random.nextBytes(randomBytes);
		}

		long mostSigBits = 0;
		for (int i = 0; i < 8; i++) {
			mostSigBits = (mostSigBits << 8) | (randomBytes[i] & 0xff);
		}
		long leastSigBits = 0;
		for (int i = 8; i < 16; i++) {