package com.consum.base.util;
|
|
public class IdUtil {
|
|
private static IdUtil instance = new IdUtil(0);
|
|
public static IdUtil getInstance() {
|
return instance;
|
}
|
|
public static long generateId() {
|
return instance.nextId();
|
}
|
|
private final static long MACHINE_BIT = 5; // max 31
|
private final static long SEQUENCE_BIT = 8; // 256/10ms
|
|
/**
|
* mask/max value
|
*/
|
private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
|
private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
|
|
private final static long MACHINE_LEFT = SEQUENCE_BIT;
|
private final static long TIMESTMP_LEFT = MACHINE_BIT + SEQUENCE_BIT;
|
|
private long machineId;
|
private long sequence = 0L;
|
private long lastStmp = -1L;
|
|
private IdUtil(long machineId) {
|
if (machineId > MAX_MACHINE_NUM || machineId < 0) {
|
throw new IllegalArgumentException(
|
"machineId can't be greater than " + MAX_MACHINE_NUM + " or less than 0");
|
}
|
this.machineId = machineId;
|
}
|
|
/**
|
* generate new ID
|
*
|
* @return
|
*/
|
public synchronized long nextId() {
|
long currStmp = getTimestamp();
|
if (currStmp < lastStmp) {
|
throw new RuntimeException("Clock moved backwards. Refusing to generate id");
|
}
|
|
if (currStmp == lastStmp) {
|
sequence = (sequence + 1) & MAX_SEQUENCE;
|
if (sequence == 0L) {
|
currStmp = getNextTimestamp();
|
}
|
} else {
|
sequence = 0L;
|
}
|
|
lastStmp = currStmp;
|
|
return currStmp << TIMESTMP_LEFT //
|
| machineId << MACHINE_LEFT //
|
| sequence;
|
}
|
|
private long getNextTimestamp() {
|
long mill = getTimestamp();
|
while (mill <= lastStmp) {
|
mill = getTimestamp();
|
}
|
return mill;
|
}
|
|
private long getTimestamp() {
|
// per 10ms
|
return System.currentTimeMillis() / 10;// 10ms
|
}
|
}
|
