代码语言：javascript复制
public class SnowflakeIdGenerator {
private final static long START_TIMESTAMP = 1609528800000L; // 2021-01-01 00:00:00
private final static long WORKER_ID_BITS = 5L;
private final static long DATACENTER_ID_BITS = 5L;
private final static long SEQUENCE_BITS = 12L;
private final static long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS);
private final static long MAX_DATACENTER_ID = ~(-1L << DATACENTER_ID_BITS);
private final static long WORKER_ID_SHIFT = SEQUENCE_BITS;
private final static long DATACENTER_ID_SHIFT = SEQUENCE_BITS WORKER_ID_BITS;
private final static long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS WORKER_ID_BITS DATACENTER_ID_BITS;
private final static long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);
private long workerId;
private long datacenterId;
private long sequence = 0L;
private long lastTimestamp = -1L;
public SnowflakeIdGenerator(long workerId, long datacenterId) {
if (workerId > MAX_WORKER_ID || workerId < 0) {
throw new IllegalArgumentException("Worker ID can't be greater than " MAX_WORKER_ID " or less than 0");
}
if (datacenterId > MAX_DATACENTER_ID || datacenterId < 0) {
throw new IllegalArgumentException("Datacenter ID can't be greater than " MAX_DATACENTER_ID " or less than 0");
}
this.workerId = workerId;
this.datacenterId = datacenterId;
}
public synchronized long nextId() {
long timestamp = System.currentTimeMillis();
if (timestamp < lastTimestamp) {
throw new RuntimeException("Clock moved backwards. Refusing to generate id for " (lastTimestamp - timestamp) " milliseconds");
}
if (timestamp == lastTimestamp) {
sequence = (sequence 1) & SEQUENCE_MASK;
if (sequence == 0L) {
timestamp = tilNextMillis(lastTimestamp);
}
} else {
sequence = 0L;
}
lastTimestamp = timestamp;
return ((timestamp - START_TIMESTAMP) << TIMESTAMP_LEFT_SHIFT) |
(datacenterId << DATACENTER_ID_SHIFT) |
(workerId << WORKER_ID_SHIFT) |
sequence;
}
private long tilNextMillis(long lastTimestamp) {
long timestamp = System.currentTimeMillis();
while (timestamp <= lastTimestamp) {
timestamp = System.currentTimeMillis();
}
return timestamp;
}
}使用方式:
代码语言：javascript复制java复制代码SnowflakeIdGeneratoridGenerator=newSnowflakeIdGenerator(workerId, datacenterId);
longid= idGenerator.nextId();其中workerId和datacenterId是分别代表工作机器ID和数据中心ID，需要在不同的机器上设置不同的值。
