RocketMQ里的一个获取时间的工具类SystemClock

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* http://www.apache.org/licenses/LICENSE-2.0
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package com.alibaba.rocketmq.common;import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;/**
* @author vintage.wang
*/
public class SystemClock { private final long precision;
private final AtomicLong now; public SystemClock(long precision) {
this.precision = precision;
now = new AtomicLong(System.currentTimeMillis());
scheduleClockUpdating();
} private void scheduleClockUpdating() {
ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(new ThreadFactory() {
@Override
public Thread newThread(Runnable runnable) {
Thread thread = new Thread(runnable, "System Clock");
thread.setDaemon(true);
return thread;
}
});
scheduler.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
now.set(System.currentTimeMillis());
}
}, precision, precision, TimeUnit.MILLISECONDS);
} public long now() {
return now.get();
} public long precision() {
return precision;
}
}