/**
* snowflake算法生成唯一ID
*/
public class IdWorker {
private static final long twepoch = 1288834974657L;
private static final long workerIdBits = 5L;
private static final long datacenterIdBits = 5L;
//private static final long maxWorkerId = -1L ^ (-1L << workerIdBits);
//private static final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
private static final long sequenceBits = 12L;
private static final long workerIdShift = sequenceBits;
private static final long datacenterIdShift = sequenceBits + workerIdBits;
private static final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private static final long sequenceMask = -1L ^ (-1L << sequenceBits);
private static final long workerId = 18;
private static final long datacenterId = 01;
private static long sequence = 0L;
private static long lastTimestamp = -1L;
/**
* @param workerId : 机器ID 0--31
* @param datacenterId : 业务ID 0--31
public IdWorker(long workerId, long datacenterId) {
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;
} */
public static synchronized long nextId() {
long timestamp = timeGen();
if (timestamp < lastTimestamp) {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
if (lastTimestamp == timestamp) {
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0) {
timestamp = tilNextMillis(lastTimestamp);
}
} else {
sequence = 0L;
}
lastTimestamp = timestamp;
return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
}
protected static long tilNextMillis(long lastTimestamp) {
long timestamp = timeGen();
while (timestamp <= lastTimestamp) {
timestamp = timeGen();
}
return timestamp;
}
protected static long timeGen() {
return System.currentTimeMillis();
}
public static void main(String[] args) {
long start = System.currentTimeMillis();
for (int i = 0; i < 1000000; i++) {
String.valueOf(IdWorker.nextId());
}
System.out.println(String.valueOf(IdWorker.nextId()));
System.out.println(String.valueOf(IdWorker.nextId()));
System.out.println(String.valueOf(IdWorker.nextId()));
System.out.println(String.valueOf(IdWorker.nextId()));
System.out.println("生成100万个订单耗时:" + (System.currentTimeMillis()-start) + "毫秒");
}
}
snowflake算法生成唯一ID
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转载自blog.csdn.net/qq_17522211/article/details/84544495
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