雪花算法和UUID

时间:2024-06-14 06:58:17
public class SnowFlake { // 数据中心(机房) id private long datacenterId; // 机器ID private long workerId; // 同一时间的序列 private long sequence; public SnowFlake(long workerId, long datacenterId) { this(workerId, datacenterId, 0); } public SnowFlake(long workerId, long datacenterId, long sequence) { // 合法判断 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", timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId); this.workerId = workerId; this.datacenterId = datacenterId; this.sequence = sequence; } // 开始时间戳(2021-10-16 22:03:32) private long twepoch = 1634393012000L; // 机房号,的ID所占的位数 5个bit 最大:11111(2进制)--> 31(10进制) private long datacenterIdBits = 5L; // 机器ID所占的位数 5个bit 最大:11111(2进制)--> 31(10进制) private long workerIdBits = 5L; // 5 bit最多只能有31个数字,就是说机器id最多只能是32以内 private long maxWorkerId = -1L ^ (-1L << workerIdBits); // 5 bit最多只能有31个数字,机房id最多只能是32以内 private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); // 同一时间的序列所占的位数 12个bit 111111111111 = 4095 最多就是同一毫秒生成4096个 private long sequenceBits = 12L; // workerId的偏移量 private long workerIdShift = sequenceBits; // datacenterId的偏移量 private long datacenterIdShift = sequenceBits + workerIdBits; // timestampLeft的偏移量 private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits; // 序列号掩码 4095 (0b111111111111=0xfff=4095) // 用于序号的与运算,保证序号最大值在0-4095之间 private long sequenceMask = -1L ^ (-1L << sequenceBits); // 最近一次时间戳 private long lastTimestamp = -1L; // 获取机器ID public long getWorkerId() { return workerId; } // 获取机房ID public long getDatacenterId() { return datacenterId; } // 获取最新一次获取的时间戳 public long getLastTimestamp() { return lastTimestamp; } // 获取下一个随机的ID public synchronized long nextId() { // 获取当前时间戳,单位毫秒 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)); } // 去重 if (lastTimestamp == timestamp) { sequence = (sequence + 1) & sequenceMask; // sequence序列大于4095 if (sequence == 0) { // 调用到下一个时间戳的方法 timestamp = tilNextMillis(lastTimestamp); } } else { // 如果是当前时间的第一次获取,那么就置为0 sequence = 0; } // 记录上一次的时间戳 lastTimestamp = timestamp; // 偏移计算 return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence; } private long tilNextMillis(long lastTimestamp) { // 获取最新时间戳 long timestamp = timeGen(); // 如果发现最新的时间戳小于或者等于序列号已经超4095的那个时间戳 while (timestamp <= lastTimestamp) { // 不符合则继续 timestamp = timeGen(); } return timestamp; } private long timeGen() { return System.currentTimeMillis(); } public static void main(String[] args) { SnowFlake worker = new SnowFlake(1, 1); long timer = System.currentTimeMillis(); for (int i = 0; i < 10000; i++) { worker.nextId(); } System.out.println(System.currentTimeMillis()); System.out.println(System.currentTimeMillis() - timer); } }