雪花算法生成ID（兩套代碼）

代碼不是自己寫的。
收集而來！

第一套

package com.utils;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;

/**
 * @author 子誠
 * Description：雪花算法生成唯一ID
 * 時間：2020/6/30 19:19
 */
public final class IdWorker {

    /**
     * 時間起始標記點，作爲基準，一般取系統的最近時間（一旦確定不能變動）
     */
    private final static long TWEPOCH = 1288834974657L;

    /**
     * 機器標識位數
     */
    private final static long WORKER_ID_BITS = 5L;

    /**
     * 數據中心標識位數
     */
    private final static long DATA_CENTER_ID_BITS = 5L;

    /**
     * 機器ID最大值
     */
    private final static long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS);

    /**
     * 數據中心ID最大值
     */
    private final static long MAX_DATA_CENTER_ID = ~(-1L << DATA_CENTER_ID_BITS);

    /**
     * 毫秒內自增位
     */
    private final static long SEQUENCE_BITS = 12L;

    /**
     * 機器ID偏左移12位
     */
    private final static long WORKER_ID_SHIFT = SEQUENCE_BITS;

    /**
     * 數據中心ID左移17位
     */
    private final static long DATA_CENTER_ID_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS;

    /**
     * 時間毫秒左移22位
     */
    private final static long TIME_STAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATA_CENTER_ID_BITS;

    private final static long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);

    /**
     * 上次生產id時間戳
     */
    private static long LAST_TIME_STAMP = -1L;

    /**
     * 0，併發控制
     */
    private long sequence = 0L;

    private final long workerId;

    /**
     * 數據標識id部分
     */
    private final long DATA_CENTER_ID;

    public IdWorker() {
        this.DATA_CENTER_ID = getDatacenterId(MAX_DATA_CENTER_ID);
        this.workerId = getMaxWorkerId(DATA_CENTER_ID, MAX_WORKER_ID);
    }

    public IdWorker(long workerId, long datacenterId) {
        if (workerId > MAX_WORKER_ID || workerId < 0) {
            throw new IllegalArgumentException(String.format("id不能大於最大值 %d 或者小於 0", MAX_WORKER_ID));
        }
        if (datacenterId > MAX_DATA_CENTER_ID || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("數據中心id不能大於最大值 %d 或者小於 0", MAX_DATA_CENTER_ID));
        }
        this.workerId = workerId;
        this.DATA_CENTER_ID = datacenterId;
    }

    /**
     * 獲取下一個ID
     *
     * @return id
     */
    public synchronized long nextId() {
        long timestamp = timeGen();
        if (timestamp < LAST_TIME_STAMP) {
            throw new RuntimeException(String.format("時間生成異常 %d", LAST_TIME_STAMP - timestamp));
        }

        if (LAST_TIME_STAMP == timestamp) {
            // 當前毫秒內，則+1
            sequence = (sequence + 1) & SEQUENCE_MASK;
            if (sequence == 0) {
                // 當前毫秒內計數滿了，則等待下一秒
                timestamp = tilNextMillis(LAST_TIME_STAMP);
            }
        } else {
            sequence = 0L;
        }
        LAST_TIME_STAMP = timestamp;
        // ID偏移組合生成最終的ID，並返回ID

        return ((timestamp - TWEPOCH) << TIME_STAMP_LEFT_SHIFT)
                | (DATA_CENTER_ID << DATA_CENTER_ID_SHIFT)
                | (workerId << WORKER_ID_SHIFT) | sequence;
    }

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

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

    /**
     * <p>
     * 獲取 maxWorkerId
     * </p>
     */
    private static long getMaxWorkerId(long dataCenterId, long maxWorkerId) {
        StringBuilder mpid = new StringBuilder();
        mpid.append(dataCenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (!name.isEmpty()) {
            /*
             * GET jvmPid
             */
            mpid.append(name.split("@")[0]);
        }
        /*
         * MAC + PID 的 hashcode 獲取16個低位
         */
        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }

    /**
     * <p>
     * 數據標識id部分
     * </p>
     */
    private static long getDatacenterId(long maxDatacenterId) {
        long id = 0L;
        try {
            InetAddress ip = InetAddress.getLocalHost();
            NetworkInterface network = NetworkInterface.getByInetAddress(ip);
            if (network == null) {
                id = 1L;
            } else {
                byte[] mac = network.getHardwareAddress();
                id = ((0x000000FF & (long) mac[mac.length - 1])
                        | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
                id = id % (maxDatacenterId + 1);
            }
        } catch (Exception e) {
            System.out.println(" getDatacenterId: " + e.getMessage());
        }
        return id;
    }

    /**
     * 靜態工具類
     *
     * @return id
     */
    public static synchronized String generateId() {
        String id = String.valueOf(new IdWorker().nextId());
        return id;
    }

    /**
     * 測試
     */
    public static void main(String[] args) {
        System.out.println("當前時間戳：" + System.currentTimeMillis());
        for (int i = 0; i < 10; i++) {
            //生成唯一雪花id
            String id = IdWorker.generateId();
            System.out.println("第" + i + "個：" + id + ";長度爲：" + id.length());
        }
    }
}

第二套

package com.utils;

import org.apache.commons.lang3.RandomUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.SystemUtils;

import java.net.Inet4Address;
import java.net.UnknownHostException;

/**
 * @author 子誠
 * Description：雪花算法生成唯一ID
 * 時間：2020/6/30 19:19
 */
public class SnowflakeIdWorker {

    // ==============================Fields===========================================
    /**
     * 開始時間截 (2015-01-01)
     */
    private final long twepoch = 1288834974657L;


    /**
     * 機器id所佔的位數
     */
    private final long workerIdBits = 5L;

    /**
     * 數據標識id所佔的位數
     */
    private final long dataCenterIdBits = 5L;

    /**
     * 支持的最大機器id，結果是31 (這個移位算法可以很快的計算出幾位二進制數所能表示的最大十進制數)
     */
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);

    /**
     * 支持的最大數據標識id，結果是31
     */
    private final long maxDataCenterId = -1L ^ (-1L << dataCenterIdBits);

    /**
     * 序列在id中佔的位數
     */
    private final long sequenceBits = 12L;

    /**
     * 機器ID向左移12位
     */
    private final long workerIdShift = sequenceBits;

    /**
     * 數據標識id向左移17位(12+5)
     */
    private final long dataCenterIdShift = sequenceBits + workerIdBits;

    /**
     * 時間截向左移22位(5+5+12)
     */
    private final long timestampLeftShift = sequenceBits + workerIdBits + dataCenterIdBits;

    /**
     * 生成序列的掩碼，這裏爲4095 (0b111111111111=0xfff=4095)
     */
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);

    /**
     * 工作機器ID(0~31)
     */
    private long workerId;

    /**
     * 數據中心ID(0~31)
     */
    private long dataCenterId;

    /**
     * 毫秒內序列(0~4095)
     */
    private long sequence = 0L;

    /**
     * 上次生成ID的時間截
     */
    private long lastTimestamp = -1L;

    private static SnowflakeIdWorker idWorker;

    static {
        idWorker = new SnowflakeIdWorker(getWorkId(), getDataCenterId());
    }

    //==============================Constructors=====================================

    /**
     * 構造函數
     *
     * @param workerId     工作ID (0~31)
     * @param dataCenterId 數據中心ID (0~31)
     */
    public SnowflakeIdWorker(long workerId, long dataCenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("workerId can't be greater than %d or less than 0", maxWorkerId));
        }
        if (dataCenterId > maxDataCenterId || dataCenterId < 0) {
            throw new IllegalArgumentException(String.format("dataCenterId can't be greater than %d or less than 0", maxDataCenterId));
        }
        this.workerId = workerId;
        this.dataCenterId = dataCenterId;
    }

    // ==============================Methods==========================================

    /**
     * 獲得下一個ID (該方法是線程安全的)
     *
     * @return SnowflakeId
     */
    public synchronized long nextId() {
        long timestamp = timeGen();

        //如果當前時間小於上一次ID生成的時間戳，說明系統時鐘回退過這個時候應當拋出異常
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(
                    String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }

        //如果是同一時間生成的，則進行毫秒內序列
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            //毫秒內序列溢出
            if (sequence == 0) {
                //阻塞到下一個毫秒,獲得新的時間戳
                timestamp = tilNextMillis(lastTimestamp);
            }
        }
        //時間戳改變，毫秒內序列重置
        else {
            sequence = 0L;
        }

        //上次生成ID的時間截
        lastTimestamp = timestamp;

        //移位並通過或運算拼到一起組成64位的ID
        return ((timestamp - twepoch) << timestampLeftShift)
                | (dataCenterId << dataCenterIdShift)
                | (workerId << workerIdShift)
                | sequence;
    }

    /**
     * 阻塞到下一個毫秒，直到獲得新的時間戳
     *
     * @param lastTimestamp 上次生成ID的時間截
     * @return 當前時間戳
     */
    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    /**
     * 返回以毫秒爲單位的當前時間
     *
     * @return 當前時間(毫秒)
     */
    protected long timeGen() {
        return System.currentTimeMillis();
    }

    private static Long getWorkId() {
        try {
            String hostAddress = Inet4Address.getLocalHost().getHostAddress();
            int[] ints = StringUtils.toCodePoints(hostAddress);
            int sums = 0;
            for (int b : ints) {
                sums += b;
            }
            return (long) (sums % 32);
        } catch (UnknownHostException e) {
            // 如果獲取失敗，則使用隨機數備用
            return RandomUtils.nextLong(0, 31);
        }
    }

    private static Long getDataCenterId() {
        int[] ints = StringUtils.toCodePoints(SystemUtils.getHostName());
        int sums = 0;
        for (int i : ints) {
            sums += i;
        }
        return (long) (sums % 32);
    }


    /**
     * 靜態工具類
     *
     * @return
     */
    public static synchronized String generateId() {
        long longId = idWorker.nextId();
        //轉成字符串
        String id = String.valueOf(longId);
        return id;
    }

    //==============================Test=============================================

    /**
     * 測試
     */
    public static void main(String[] args) {
        System.out.println(System.currentTimeMillis());
        long startTime = System.nanoTime();
        for (int i = 0; i < 100; i++) {
            //生成唯一雪花id
            String id = SnowflakeIdWorker.generateId();
            System.out.println("第" + i + "個：" + id + ";長度爲：" + id.length());
        }
        System.out.println((System.nanoTime() - startTime) / 1000000 + "ms");
    }
}