id生成器 sonwFlake算法

/*
* Copyright (c) 2014 xiaomaihd and/or its affiliates.All Rights Reserved.
* http://www.xiaomaihd.com
*/

    import lombok.extern.slf4j.Slf4j;
    
    /**
     * Created by YangFan on 15/4/21 下午6:34.
     * <p>
     */
    @Slf4j
    public class IdWorker {
        private final long workerId;
        private final static long twepoch = 1361753741828L;
        private long sequence = 0L;
        //机器标识位数
        private final static long workerIdBits = 5L;
        //机器ID最大值
        public final static long maxWorkerId = -1L ^ -1L << workerIdBits;
        //毫秒内自增位
        private final static long sequenceBits = 10L;
        //机器ID偏左移位
        private final static long workerIdShift = sequenceBits;
        //时间毫秒左移
        private final static long timestampLeftShift = sequenceBits + workerIdBits;
        public final static long sequenceMask = -1L ^ -1L << sequenceBits;
    
        private long lastTimestamp = -1L;
    
        public IdWorker(final long workerId) {
            super();
            if (workerId > maxWorkerId || workerId < 0) {
                throw new IllegalArgumentException(String.format(
                        "worker Id can't be greater than %d or less than 0",
                        maxWorkerId));
            }
            this.workerId = workerId;
        }
    
        public synchronized long nextId() {
            long timestamp = this.timeGen();
            if (this.lastTimestamp == timestamp) {
                //当前毫秒内，则+1
                this.sequence = (this.sequence + 1) & sequenceMask;
                if (this.sequence == 0) {
                    System.out.println("###########" + sequenceMask);
                    //当前毫秒内计数满了，则等待下一秒
                    timestamp = this.tilNextMillis(this.lastTimestamp);
                }
            } else {
                this.sequence = 0;
            }
            //时间错误
        
            if (timestamp < this.lastTimestamp) {
                try {
                    throw new Exception(
                            String.format(
                                    "Clock moved backwards.  Refusing to generate id for %d milliseconds",
                                    this.lastTimestamp - timestamp));
                } catch (Exception e) {
                    log.error(e.getMessage(), e);
                }
            }
    
            this.lastTimestamp = timestamp;
            //ID偏移组合生成最终的ID，并返回ID
            long nextId = ((timestamp - twepoch << timestampLeftShift))
                    | (this.workerId << workerIdShift) | (this.sequence);
    //  System.out.println("timestamp:" + timestamp + ",timestampLeftShift:"
    //    + timestampLeftShift + ",nextId:" + nextId + ",workerId:"
    //    + workerId + ",sequence:" + sequence);
            return nextId;
        }
    
        //等待下一个毫秒的到来
        private long tilNextMillis(final long lastTimestamp) {
            long timestamp = this.timeGen();
            while (timestamp <= lastTimestamp) {
                timestamp = this.timeGen();
            }
            return timestamp;
        }
    
        private long timeGen() {
            return System.currentTimeMillis();
        }
        
    }

拓展了一层
/*
* Copyright (c) 2014 xiaomaihd and/or its affiliates.All Rights Reserved.
* http://www.xiaomaihd.com
*/
package com.longe.nuclear.util.id;

    /**
     * Created by YangFan on 15/4/24 下午3:12.
     * <p>
     * ID工具类
     */
    public class IdUtil {
    
        private static IdWorker idWorker = new IdWorker(1);
    
        private IdUtil() {
        }
    
        public static long generateId() {
            return idWorker.nextId();
        }
            
    }

调用IdUtil .generateId()就可以处理并发ID生成问题，这个ID生成的是纯数字 底层是2进制的64位长度，UUID是16进制32位。