在关闭显示的情况下, 可以达到每毫秒3万个的生成速度
/**
* An Implementation of Twitter Snowflake ID Generator
*/
public class SnowflakeId {
private final static long EPOCH = 0L; // shift for smaller timestamp
private final static long DEVICE_ID_BITS = 2L;
private final static long SEQUENCE_BITS = 16L;
private final static long MAX_WORKER_ID = -1L ^ -1L << DEVICE_ID_BITS; // 与& 非~ 或| 异或^, only the bit on WORKER_ID_BITS are 1
private final static int SEQUENCE_MASK = (int)(-1L ^ -1L << SEQUENCE_BITS); private final long deviceId;
private final RecyclableAtomicInteger atomic = new RecyclableAtomicInteger();
private long lastTimestamp = -1L; public SnowflakeId(final long deviceId) {
if (deviceId > MAX_WORKER_ID || deviceId < 0) {
throw new IllegalArgumentException(
String.format("Device ID should be between 0 and %d", this.MAX_WORKER_ID));
}
this.deviceId = deviceId;
} public long nextId() {
long timestamp = millisecond();
if (timestamp < lastTimestamp) {
throw new IllegalArgumentException(
String.format("Wait %d milliseconds", lastTimestamp - timestamp));
} if (lastTimestamp == timestamp) {
int sequence = atomic.incrementAndRecycle(SEQUENCE_MASK);
if (sequence == 0) {
timestamp = waitTilNextMillis(lastTimestamp);
lastTimestamp = timestamp;
}
return (timestamp - EPOCH << (SEQUENCE_BITS + DEVICE_ID_BITS)) | (deviceId << SEQUENCE_BITS) | sequence;
} else {
atomic.set(0);
lastTimestamp = timestamp;
return (timestamp - EPOCH << (SEQUENCE_BITS + DEVICE_ID_BITS)) | (deviceId << SEQUENCE_BITS);
}
} private long waitTilNextMillis(final long lastTimestamp) {
System.out.print(lastTimestamp);
long timestamp;
for (;;) {
timestamp = this.millisecond();
System.out.print('+');
if (timestamp > lastTimestamp) {
System.out.print("\n");
return timestamp;
}
}
} private long millisecond() {
return System.currentTimeMillis();
} public static void main(String[] args) {
SnowflakeId worker = new SnowflakeId(1);
long start = System.currentTimeMillis();
for (int i = 0; i < 5000000; i ++) {
//System.out.println(worker.nextId());
worker.nextId();
}
long duration = System.currentTimeMillis() - start;
System.out.println("Total: " + duration + "ms, " + 5000000/duration + "/ms");
}
}