Java代码示例：演示Twitter的Snowflake雪花算法的实现

桃扇骨 2024-02-17 10:09 4阅读 0赞

以下是一个Java代码示例，演示了如何实现Twitter的Snowflake算法：

public class Snowflake {
        
        private static final long EPOCH = 1609459200000L; // 设置起始时间戳，2021-01-01 00:00:00 UTC
        private static final long WORKER_ID_BITS = 5L;
        private static final long DATA_CENTER_ID_BITS = 5L;
        private static final long SEQUENCE_BITS = 12L;
    
        private static final long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS);
        private static final long MAX_DATA_CENTER_ID = ~(-1L << DATA_CENTER_ID_BITS);
    
        private static final long WORKER_ID_SHIFT = SEQUENCE_BITS;
        private static final long DATA_CENTER_ID_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS;
        private static final long TIMESTAMP_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATA_CENTER_ID_BITS;
    
        private static final long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);
    
        private final long workerId;
        private final long dataCenterId;
        private long sequence = 0L;
        private long lastTimestamp = -1L;
    
        public Snowflake(long workerId, long dataCenterId) {
        
            if (workerId > MAX_WORKER_ID || workerId < 0) {
        
                throw new IllegalArgumentException("Invalid workerId");
            }
            if (dataCenterId > MAX_DATA_CENTER_ID || dataCenterId < 0) {
        
                throw new IllegalArgumentException("Invalid dataCenterId");
            }
            this.workerId = workerId;
            this.dataCenterId = dataCenterId;
        }
    
        public synchronized long generateId() {
        
            long timestamp = System.currentTimeMillis();
            if (timestamp < lastTimestamp) {
        
                throw new RuntimeException("Invalid system clock!");
            }
            if (timestamp == lastTimestamp) {
        
                sequence = (sequence + 1) & SEQUENCE_MASK;
                if (sequence == 0) {
        
                    timestamp = tilNextMillis(lastTimestamp);
                }
            } else {
        
                sequence = 0L;
            }
            lastTimestamp = timestamp;
    
            return ((timestamp - EPOCH) << TIMESTAMP_SHIFT)
                    | (dataCenterId << DATA_CENTER_ID_SHIFT)
                    | (workerId << WORKER_ID_SHIFT)
                    | sequence;
        }
    
        private long tilNextMillis(long lastTimestamp) {
        
            long timestamp = System.currentTimeMillis();
            while (timestamp <= lastTimestamp) {
        
                timestamp = System.currentTimeMillis();
            }
            return timestamp;
        }
    }

使用示例：

public class Main {
        
        public static void main(String[] args) {
        
            Snowflake snowflake = new Snowflake(1, 1);
            long uniqueId = snowflake.generateId();
            System.out.println(uniqueId);
        }
    }

在实际使用中，需要根据具体的业务需求进行适当的调整和扩展，例如调整位数、处理时钟回拨等。此示例代码仅为演示Snowflake算法的基本原理，并不包含完整的错误处理和容错机制。