Package cn.xuanyuanli.core.util.snowflake

Class SystemClock

java.lang.Object

cn.xuanyuanli.core.util.snowflake.SystemClock

public class SystemClock
extends Object

高并发场景下System.currentTimeMillis()的性能问题的优化

System.currentTimeMillis()的调用比new一个普通对象要耗时的多（参考：System.currentTimeMillis()性能分析）

System.currentTimeMillis()之所以慢是因为去跟系统打了一次交道

后台定时更新时钟，JVM退出时，线程自动回收

10亿：43410,206,210.72815533980582%

1亿：4699,29,162.0344827586207%

1000万：480,12,40.0%

100万：50,10,5.0%

Author:

lry

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	SystemClock.InstanceHolder

Field Summary

Fields

Modifier and Type	Field	Description
(package private) final AtomicLong	now	当前
(package private) final long	period	周期
(package private) static ScheduledExecutorService	SCHEDULEDPOOL	scheduledpool

Constructor Summary

Constructors

Constructor	Description
SystemClock(long period)	系统时钟

Method Summary

Modifier and Type	Method	Description
(package private) long	currentTimeMillis()	当前时间
(package private) static SystemClock	instance()	实例
static long	now()	当前
(package private) void	scheduleClockUpdating()	安排时间更新

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

period

final long period

周期

now

final AtomicLong now

当前

SCHEDULEDPOOL

static ScheduledExecutorService SCHEDULEDPOOL

scheduledpool

Constructor Details

SystemClock

SystemClock(long period)

系统时钟

Parameters:

period - 期

Method Details

instance

static SystemClock instance()

实例

Returns:

SystemClock

scheduleClockUpdating

void scheduleClockUpdating()

安排时间更新

currentTimeMillis

long currentTimeMillis()

当前时间

Returns:

long

now

public static long now()

当前

Returns:

long