工程里有获取唯一时间戳作为id的需求,想了想用乐观锁cas实现,自旋.
cas原子性操作获得了绝对唯一的时间戳(纳秒版本).单机有效,不能分布式调用.
public class AtomicTimeStamp {
private AtomicLong timeMills = new AtomicLong(0);
private static AtomicLong at = new AtomicLong(0);
public Long getNextNaos(){
while (true){
long currentTimeMillis = System.nanoTime();
long currentMill = timeMills.get();
if(currentTimeMillis > currentMill && timeMills.compareAndSet(currentMill, currentTimeMillis)){
return currentTimeMillis;
//返回唯一时间戳
}
}
}
public static void main(String[] args) {
AtomicTimeStamp stamp = new AtomicTimeStamp();
ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(100, 150, 200, TimeUnit.MILLISECONDS, new PriorityBlockingQueue<>(100),new ThreadFactoryBuilder().build());
long l = System.currentTimeMillis();
//开启三个线程测试成功性,at自增,测试10S会有多少个成功的
poolExecutor.execute(()->{
while (true){
stamp.getNextNaos();
at.getAndIncrement();
long l1 = System.currentTimeMillis();
if(l1 > l + 10000 & l1<l+10010){
System.out.println(at.longValue());
}
}
});
poolExecutor.execute(()->{
while (true){
stamp.getNextNaos();
at.getAndIncrement();
long l1 = System.currentTimeMillis();
if (l1 > l + 10000 & l1 < l + 10010) {
System.out.println(at.longValue());
}
}
});
poolExecutor.execute(()->{
while (true){
stamp.getNextNaos();
at.getAndIncrement();
long l1 = System.currentTimeMillis();
if (l1 > l + 10000 & l1 < l + 10010) {
System.out.println(at.longValue());
}
}
});
}
}