我一下子说出四种分布式ID生成方案，把面试官给搞懵了

public class IdWorker {   private long workerId; // 这个就是代表了机器id   private long datacenterId; // 这个就是代表了机房id   private long sequence; // 这个就是代表了一毫秒内生成的多个id的最新序号   public IdWorker(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0       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));       }       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id   public 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) {           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));       }              // 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4096       if (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();   }   //---------------测试---------------   public static void main(String[] args) {              IdWorker worker = new IdWorker(1,1,1);              for (int i = 0; i < 30; i++) {           System.out.println(worker.nextId());       }   }}