SnowFlake算法生成id的结果是一个64bit大小的整数。
先将当前时间戳左移，放到41 bit那儿；将机房id左移放到5 bit那儿；将机器id左移放到5 bit那儿；将序号放最后12 bit。 最后拼接起来成一个64 bit的二进制数字，转换成10进制就是个long型。

public class SnowFlakeUtils {/*** 这个就是代表了机器id*/private long workerId;/*** 这个就是代表了机房id* */private long dataCenterId;/*** 这个就是代表了一毫秒内生成的多个id的最新序号*/private long sequence;public SnowFlakeUtils(long workerId, long dataCenterId, long sequence) {// sanity check for workerId// 这儿不就检查了一下，要求就是你传递进来的机房id和机器id不能超过32，不能小于0if (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));}this.workerId = workerId;this.dataCenterId = dataCenterId;this.sequence = sequence;}private long twepoch = 1288834974657L;private long workerIdBits = 5L;private long datacenterIdBits = 5L;// 这个是二进制运算，就是5 bit最多只能有31个数字，也就是说机器id最多只能是32以内private long maxWorkerId = -1L ^ (-1L << workerIdBits);// 这个是一个意思，就是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);private long sequenceBits = 12L;private long workerIdShift = sequenceBits;private long datacenterIdShift = sequenceBits + workerIdBits;private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;private long sequenceMask = -1L ^ (-1L << sequenceBits);private long lastTimestamp = -1L;public long getWorkerId(){return workerId;}public long getDatacenterId() {return dataCenterId;}public long getTimestamp() {return System.currentTimeMillis();}// 这个是核心方法，通过调用nextId()方法，让当前这台机器上的snowflake算法程序生成一个全局唯一的idpublic synchronized long nextId() {// 这儿就是获取当前时间戳，单位是毫秒long timestamp = timeGen();if (timestamp < lastTimestamp) {throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds",lastTimestamp - timestamp));}// 下面是说假设在同一个毫秒内，又发送了一个请求生成一个id// 这个时候就得把seqence序号给递增1，最多就是4096if (lastTimestamp == timestamp) {// 这个意思是说一个毫秒内最多只能有4096个数字，无论你传递多少进来，//这个位运算保证始终就是在4096这个范围内，避免你自己传递个sequence超过了4096这个范围sequence = (sequence + 1) & sequenceMask;if (sequence == 0) {timestamp = tilNextMillis(lastTimestamp);}} else {sequence = 0;}// 这儿记录一下最近一次生成id的时间戳，单位是毫秒lastTimestamp = timestamp;// 这儿就是最核心的二进制位运算操作，生成一个64bit的id// 先将当前时间戳左移，放到41 bit那儿；将机房id左移放到5 bit那儿；将机器id左移放到5 bit那儿；将序号放最后12 bit// 最后拼接起来成一个64 bit的二进制数字，转换成10进制就是个long型return ((timestamp - twepoch) << timestampLeftShift) |(dataCenterId << datacenterIdShift) |(workerId << workerIdShift) | sequence;}private long tilNextMillis(long lastTimestamp) {long timestamp = timeGen();while (timestamp <= lastTimestamp) {timestamp = timeGen();}return timestamp;}private long timeGen(){return System.currentTimeMillis();}}