如果你的这个值是用来做数据库的表数据唯一标识的话，建议可以用twitter idworker的算法，支持分布式部署生成，性能极高，也是支持排序的。package com.idworker;

public class IdWorker {

private final long workerId;

private final static long twepoch = 1288834974657L;

private long sequence = 0L;

private final static long workerIdBits = 4L;

public final static long maxWorkerId = -1L ^ -1L << workerIdBits;

private final static long sequenceBits = 10L;

private final static long workerIdShift = sequenceBits;

private final static long timestampLeftShift = sequenceBits + workerIdBits;

public final static long sequenceMask = -1L ^ -1L << sequenceBits;

private long lastTimestamp = -1L;

public IdWorker(final long workerId) {

super();

if (workerId > this.maxWorkerId || workerId < 0) {

throw new IllegalArgumentException(String.format(

"worker Id can't be greater than %d or less than 0",

this.maxWorkerId));

}

this.workerId = workerId;

}

public synchronized long nextId() {

long timestamp = this.timeGen();

if (this.lastTimestamp == timestamp) {

this.sequence = (this.sequence + 1) & this.sequenceMask;

if (this.sequence == 0) {

System.out.println("###########" + sequenceMask);

timestamp = this.tilNextMillis(this.lastTimestamp);

}

} else {

this.sequence = 0;

}

if (timestamp < this.lastTimestamp) {

try {

throw new Exception(

String.format(

"Clock moved backwards. Refusing to generate id for %d milliseconds",

this.lastTimestamp - timestamp));

} catch (Exception e) {

e.printStackTrace();

}

}

this.lastTimestamp = timestamp;

long nextId = ((timestamp - twepoch << timestampLeftShift))

| (this.workerId << this.workerIdShift) | (this.sequence);

System.out.println("timestamp:" + timestamp + ",timestampLeftShift:"

+ timestampLeftShift + ",nextId:" + nextId + ",workerId:"

+ workerId + ",sequence:" + sequence);

return nextId;

}

private long tilNextMillis(final long lastTimestamp) {

long timestamp = this.timeGen();

while (timestamp <= lastTimestamp) {

timestamp = this.timeGen();

}

return timestamp;

}

private long timeGen() {

return System.currentTimeMillis();

}

public static void main(String[] args){

IdWorker worker2 = new IdWorker(2);

System.out.println(worker2.nextId());

}

}