生成订单号18位不重复数字

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最近项目中需要用到订单号,在csdn上找到一款根据时间,id,以及machineId,如果并发过大,也可以再用上thread的id,下面贴出代码

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/**
 * 42位的时间前缀+10位的节点标识+12位的sequence避免并发的数字（12位不够用时强制得到新的时间前缀）
 * <p>
 * <b>对系统时间的依赖性非常强，需要关闭ntp的时间同步功能，或者当检测到ntp时间调整后，拒绝分配id。
 *
 * @author
 */
public class OrderNoUtil {
//    private final static Logger logger = LoggerFactory.getLogger(IdWorker.class);

    private final long workerId;
    private final long snsEpoch = 1330328109047L;// 起始标记点，作为基准
    private long sequence;
    private final long workerIdBits = 10L;// 只允许workid的范围为：0-1023
    private final long maxWorkerId = -1L ^ -1L << this.workerIdBits;// 1023,1111111111,10位
    private final long sequenceBits = 12L;// sequence值控制在0-4095

    private final long workerIdShift = this.sequenceBits;// 12
    private final long timestampLeftShift = this.sequenceBits + this.workerIdBits;// 22
    private final long sequenceMask = -1L ^ -1L << this.sequenceBits;// 4095,111111111111,12位

    private long lastTimestamp = -1L;

    {
        sequence = Long.parseLong(PropertiesUtil.getProperty("machine.id"));
    }

    public OrderNoUtil(long workerId) {
        super();
        if (workerId > this.maxWorkerId || workerId < 0) {// workid < 1024[10位：2的10次方]
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", this.maxWorkerId));
        }
        this.workerId = workerId;
    }

    public synchronized long nextId() throws Exception {
        long timestamp = this.timeGen();
        if (this.lastTimestamp == timestamp) {// 如果上一个timestamp与新产生的相等，则sequence加一(0-4095循环)，下次再使用时sequence是新值
            //System.out.println("lastTimeStamp:" + lastTimestamp);
            this.sequence = this.sequence + 1 & this.sequenceMask;
            if (this.sequence == 0) {
                timestamp = this.tilNextMillis(this.lastTimestamp);// 重新生成timestamp
            }
        }
        else {
            this.sequence = 0;
        }
        if (timestamp < this.lastTimestamp) {
//            logger.error(String.format("Clock moved backwards.Refusing to generate id for %d milliseconds", (this.lastTimestamp - timestamp)));
            throw new Exception(String.format("Clock moved backwards.Refusing to generate id for %d milliseconds", (this.lastTimestamp - timestamp)));
        }

        this.lastTimestamp = timestamp;
        // 生成的timestamp
        return timestamp - this.snsEpoch << this.timestampLeftShift | this.workerId << this.workerIdShift | this.sequence;
    }

    /**
     * 保证返回的毫秒数在参数之后
     *
     * @param lastTimestamp
     * @return
     */
    private long tilNextMillis(long lastTimestamp) {
        long timestamp = this.timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }
        return timestamp;
    }

    /**
     * 获得系统当前毫秒数
     *
     * @return
     */
    private long timeGen() {
        return System.currentTimeMillis();
    }

//    public static void main(String[] args) throws Exception {
//        OrderNoUtil iw1 = new OrderNoUtil(0);
////        IdWorker iw2 = new IdWorker(2);
////        IdWorker iw3 = new IdWorker(3);
//        Set<String> strSet = Sets.newHashSet();
//        for(int i = 0; i < 10000000; i++) {
//            String str = iw1.nextId() + "";
//            strSet.add(str);
//        }
//        System.out.println(strSet.size());
//    }
}