生成19位bigint/long类型的不重复id

项目中经常会用到id，一个项目中偶尔会使用到全局id，要求不重复且具有一定的查询效率，所以写了一个19位的不重复id生成器

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public class IdWorker {
	/**
	 * 一启动就创建一个worker，如果有多台机器，则workerID和datacenterID可以从配置文件中读取
	 */
	private static IdWorker worker = new IdWorker(1, 1, 1);

	/**
	 * 生成一个ID
	 * 
	 * @return
	 */
	public static long getId() {
		return worker.nextId();
	}

	private long workerId;
	private long datacenterId;
	private long sequence;

	private IdWorker(long workerId, long datacenterId, long sequence) {
		if (workerId > maxWorkerId || workerId < 0) {
			throw new IllegalArgumentException(
					String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
		}

		if (datacenterId > maxDatacenterId || datacenterId < 0) {
			throw new IllegalArgumentException(
					String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
		}

		System.out.printf(
				"worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d \r\n",
				timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId);

		this.workerId = workerId;
		this.datacenterId = datacenterId;
		this.sequence = sequence;
	}

	private long twepoch = 1288834974657L;

	private long workerIdBits = 5L;
	private long datacenterIdBits = 5L;
	private long maxWorkerId = -1L ^ (-1L << workerIdBits);
	private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
	private long sequenceBits = 12L;

	private long workerIdShift = sequenceBits;
	private long datacenterIdShift = sequenceBits + workerIdBits;
	private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
	private long sequenceMask = -1L ^ (-1L << sequenceBits);

	private long lastTimestamp = -1L;

	private synchronized long nextId() {
		long timestamp = timeGen();

		if (timestamp < lastTimestamp) {
			System.err.printf("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp);
			throw new RuntimeException(String.format(
					"Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
		}

		if (lastTimestamp == timestamp) {
			sequence = (sequence + 1) & sequenceMask;
			if (sequence == 0) {
				timestamp = tilNextMillis(lastTimestamp);
			}
		} else {
			sequence = 0;
		}

		lastTimestamp = timestamp;
		return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift)
				| (workerId << workerIdShift) | sequence;
	}

	private long tilNextMillis(long lastTimestamp) {
		long timestamp = timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = timeGen();
		}
		return timestamp;
	}

	private long timeGen() {
		return System.currentTimeMillis();
	}

	static Map<Long, Long> kvs = Collections.synchronizedMap(new HashMap<Long, Long>());

	// ---------------测试---------------
	public static void main(String[] args) {
		for (int i = 0; i < 10; i++) {
			Thread t = new Thread(new Runnable() {
				public void run() {
					// System.out.println( Thread.currentThread().getId());
					for (int i = 0; i < 1000; i++) {
						long id = IdWorker.getId();
						System.out.println(id);
						if (!kvs.containsKey(id)) {
							kvs.put(id, id);
							// System.out.println(id);
						} else {
							System.out.println("重复的ID：" + id);
						}
						try {
							Thread.sleep(1);
						} catch (InterruptedException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
					}
				}
			});
			t.start();
		}
	}
}