Not a member of Pastebin yet?
Sign Up,
it unlocks many cool features!
- /**
- * twitter的snowflake算法 -- java实现
- *
- * @author beyond
- * @date 2016/11/26
- */
- public class SnowFlake {
- /**
- * 起始的时间戳
- */
- private final static long START_STMP = 1480166465631L;
- /**
- * 每一部分占用的位数
- */
- private final static long SEQUENCE_BIT = 12; //序列号占用的位数
- private final static long MACHINE_BIT = 5; //机器标识占用的位数
- private final static long DATACENTER_BIT = 5;//数据中心占用的位数
- /**
- * 每一部分的最大值
- */
- private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
- private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
- private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
- /**
- * 每一部分向左的位移
- */
- private final static long MACHINE_LEFT = SEQUENCE_BIT;
- private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
- private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
- private long datacenterId; //数据中心
- private long machineId; //机器标识
- private long sequence = 0L; //序列号
- private long lastStmp = -1L;//上一次时间戳
- public SnowFlake(long datacenterId, long machineId) {
- if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
- throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
- }
- if (machineId > MAX_MACHINE_NUM || machineId < 0) {
- throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
- }
- this.datacenterId = datacenterId;
- this.machineId = machineId;
- }
- /**
- * 产生下一个ID
- *
- * @return
- */
- public synchronized long nextId() {
- long currStmp = getNewstmp();
- if (currStmp < lastStmp) {
- throw new RuntimeException("Clock moved backwards. Refusing to generate id");
- }
- if (currStmp == lastStmp) {
- //相同毫秒内,序列号自增
- sequence = (sequence + 1) & MAX_SEQUENCE;
- //同一毫秒的序列数已经达到最大
- if (sequence == 0L) {
- currStmp = getNextMill();
- }
- } else {
- //不同毫秒内,序列号置为0
- sequence = 0L;
- }
- lastStmp = currStmp;
- return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
- | datacenterId << DATACENTER_LEFT //数据中心部分
- | machineId << MACHINE_LEFT //机器标识部分
- | sequence; //序列号部分
- }
- private long getNextMill() {
- long mill = getNewstmp();
- while (mill <= lastStmp) {
- mill = getNewstmp();
- }
- return mill;
- }
- private long getNewstmp() {
- return System.currentTimeMillis();
- }
- public static void main(String[] args) {
- SnowFlake snowFlake = new SnowFlake(2, 3);
- for (int i = 0; i < (1 << 12); i++) {
- System.out.println(snowFlake.nextId());
- }
- }
- }
Add Comment
Please, Sign In to add comment