雪花算法
package com.ccb.utils;
public class SnowflakeIdGenerator {
// 定义雪花 ID 的各部分位数
private static final long TIMESTAMP_BITS = 41L;
private static final long NODE_ID_BITS = 10L;
private static final long SEQUENCE_BITS = 12L;
// 定义起始时间戳(可根据实际情况调整)
private static final long EPOCH = 1609459200000L;
// 定义最大取值范围
private static final long MAX_NODE_ID = (1L << NODE_ID_BITS) - 1;
private static final long MAX_SEQUENCE = (1L << SEQUENCE_BITS) - 1;
// 定义偏移量
private static final long TIMESTAMP_SHIFT = NODE_ID_BITS + SEQUENCE_BITS;
private static final long NODE_ID_SHIFT = SEQUENCE_BITS;
private final long nodeId;
private long lastTimestamp = -1L;
private long sequence = 0L;
public SnowflakeIdGenerator(long nodeId) {
if (nodeId < 0 || nodeId > MAX_NODE_ID) {
throw new IllegalArgumentException("Invalid node ID");
}
this.nodeId = nodeId;
}
public synchronized long generateId() {
long currentTimestamp = timestamp();
if (currentTimestamp < lastTimestamp) {
throw new IllegalStateException("Clock moved backwards");
}
if (currentTimestamp == lastTimestamp) {
sequence = (sequence + 1) & MAX_SEQUENCE;
if (sequence == 0) {
currentTimestamp = untilNextMillis(lastTimestamp);
}
} else {
sequence = 0L;
}
lastTimestamp = currentTimestamp;
return ((currentTimestamp - EPOCH) << TIMESTAMP_SHIFT) |
(nodeId << NODE_ID_SHIFT) |
sequence;
}
private long timestamp() {
return System.currentTimeMillis();
}
private long untilNextMillis(long lastTimestamp) {
long currentTimestamp = timestamp();
while (currentTimestamp <= lastTimestamp) {
currentTimestamp = timestamp();
}
return currentTimestamp;
}
public static void main(String[] args) {
// 创建一个雪花 ID 生成器实例,传入节点 ID
SnowflakeIdGenerator idGenerator = new SnowflakeIdGenerator(1);
// 生成 ID
long id = idGenerator.generateId();
System.out.println(id);
}
}