|
@@ -0,0 +1,115 @@
|
|
|
+package net.mooctest.www.android_auto_test.utils;
|
|
|
+
|
|
|
+/**
|
|
|
+ * 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
|
|
|
+ */
|
|
|
+ //序列号占用的位数
|
|
|
+ private final static long SEQUENCE_BIT = 12;
|
|
|
+ //机器标识占用的位数
|
|
|
+ private final static long MACHINE_BIT = 5;
|
|
|
+ //数据中心占用的位数
|
|
|
+ private final static long DATACENTER_BIT = 5;
|
|
|
+
|
|
|
+ /**
|
|
|
+ * 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;
|
|
|
+
|
|
|
+ //数据中心
|
|
|
+ private long datacenterId;
|
|
|
+ //机器标识
|
|
|
+ private long machineId;
|
|
|
+ //序列号
|
|
|
+ private long sequence = 0L;
|
|
|
+ //上一次时间戳
|
|
|
+ private long lastStmp = -1L;
|
|
|
+
|
|
|
+ private static SnowFlake singleton;
|
|
|
+
|
|
|
+ public static SnowFlake getInstance(){
|
|
|
+ if (singleton == null) {
|
|
|
+ synchronized (SnowFlake.class) {
|
|
|
+ if (singleton == null) {
|
|
|
+ singleton = new SnowFlake(2,3);
|
|
|
+ }
|
|
|
+ }
|
|
|
+ }
|
|
|
+ return singleton;
|
|
|
+ }
|
|
|
+
|
|
|
+ private 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();
|
|
|
+ }
|
|
|
+}
|