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| public class SnowflakeIdGenerator { private final long startTime = 1498608000000L; private final long workerIdBits = 5L; private final long dataCenterIdBits = 5L; private final long maxWorkerId = -1L ^ (-1L << workerIdBits); private final long maxDataCenterId = -1L ^ (-1L << dataCenterIdBits); private final long sequenceBits = 12L; private final long workerIdMoveBits = sequenceBits; private final long dataCenterIdMoveBits = sequenceBits + workerIdBits; private final long timestampMoveBits = sequenceBits + workerIdBits + dataCenterIdBits; private final long sequenceMask = -1L ^ (-1L << sequenceBits);
private long workerId;
private long dataCenterId;
private long sequence = 0L;
private long lastTimestamp = -1L;
public SnowflakeIdGenerator(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 synchronized long nextId() { long timestamp = currentTime(); 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 = blockTillNextMillis(lastTimestamp); } } else { sequence = 0L; } lastTimestamp = timestamp; return ((timestamp - startTime) << timestampMoveBits) | (dataCenterId << dataCenterIdMoveBits) | (workerId << workerIdMoveBits) | sequence; }
protected long blockTillNextMillis(long lastTimestamp) { long timestamp = currentTime(); while (timestamp <= lastTimestamp) { timestamp = currentTime(); } return timestamp; }
protected long currentTime() { return System.currentTimeMillis(); } public static Long getId() { SnowflakeIdGenerator idWorker = new SnowflakeIdGenerator(0, 0); return idWorker.nextId(); } }
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