一个系统时间缓存代码片段

package com.taobao.metamorphosis.server.utils;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;/** * 系统时间缓存 *  * @author boyan * @Date 2010-9-28 *  */public class SystemTimer {    private final static ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();    private static final long tickUnit = Long.parseLong(System.getProperty("notify.systimer.tick", "50"));    static {        executor.scheduleAtFixedRate(new TimerTicker(), tickUnit, tickUnit, TimeUnit.MILLISECONDS);        Runtime.getRuntime().addShutdownHook(new Thread() {            @Override            public void run() {                executor.shutdown();            }        });    }    private static volatile long time = System.currentTimeMillis();    private static class TimerTicker implements Runnable {        public void run() {            time = System.currentTimeMillis();        }    }    public static long currentTimeMillis() {        return time;    }}