Snowflake雪花算法（2）

package com.black.uuid.util;

/**

 * snowflake雪花算法

 *

 * @author Black

 * @date 2019年7月6日 下午4:15:11

 * @version 0.1.0

 * @copyright black.cn

 */

public class SnowflakeUtil {

/**

* 起始的时间戳

*/

private final static long START_STMP = 1480166465631L;

/**

* 每一部分占用的位数

*/

private final static long SEQUENCE_BIT = 12; // 序列号占用的位数

private final static long MACHINE_BIT = 5; // 机器标识占用的位数

private final static long DATACENTER_BIT = 5;// 数据中心占用的位数

/**

* 每一部分的最大值

*/

private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);

private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);

private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

/**

* 每一部分向左的位移

*/

private final static long MACHINE_LEFT = SEQUENCE_BIT;

private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;

private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

private long datacenterId; // 数据中心

private long machineId; // 机器标识

private long sequence = 0L; // 序列号

private long lastStmp = -1L;// 上一次时间戳

public SnowflakeUtil(long datacenterId, long machineId) {

if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {

throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");

}

if (machineId > MAX_MACHINE_NUM || machineId < 0) {

throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");

}

this.datacenterId = datacenterId;

this.machineId = machineId;

}

/**

* 产生下一个ID

*

* @return

*/

public synchronized long nextId() {

long currStmp = getNewstmp();

if (currStmp < lastStmp) {

throw new RuntimeException("Clock moved backwards.  Refusing to generate id");

}

if (currStmp == lastStmp) {

// 相同毫秒内，序列号自增

sequence = (sequence + 1) & MAX_SEQUENCE;

// 同一毫秒的序列数已经达到最大

if (sequence == 0L) {

currStmp = getNextMill();

}

} else {

// 不同毫秒内，序列号置为0

sequence = 0L;

}

lastStmp = currStmp;

return (currStmp - START_STMP) << TIMESTMP_LEFT // 时间戳部分

| datacenterId << DATACENTER_LEFT // 数据中心部分

| machineId << MACHINE_LEFT // 机器标识部分

| sequence; // 序列号部分

}

private long getNextMill() {

long mill = getNewstmp();

while (mill <= lastStmp) {

mill = getNewstmp();

}

return mill;

}

private long getNewstmp() {

return System.currentTimeMillis();

}

public static void main(String[] args) {

SnowflakeUtil snowFlake = new SnowflakeUtil(2, 3);

for (int i = 0; i < (1 << 12); i++) {

System.out.println(snowFlake.nextId());

}

}

}

来源：CSDN

作者：Black10086

链接：https://blog.csdn.net/ls_call520/article/details/103897729