bitronix.tm.utils.MonotonicClock Maven / Gradle / Ivy
/*
* Copyright (C) 2006-2013 Bitronix Software (http://www.bitronix.be)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package bitronix.tm.utils;
import java.util.concurrent.atomic.AtomicLong;
/**
* A System.currentTimeMillis() replacement which guarantees monotonic time increment.
*
* @author Ludovic Orban
*/
public final class MonotonicClock
{
private static final AtomicLong lastTime = new AtomicLong(Long.MIN_VALUE);
/**
* Constructor MonotonicClock creates a new MonotonicClock instance.
*/
private MonotonicClock()
{
}
/**
* Return the current time in milliseconds, guaranteeing monotonic time increment.
*
* @return the current time in milliseconds.
*/
public static long currentTimeMillis()
{
long now = System.currentTimeMillis();
long time = lastTime.get();
if (now > time)
{
lastTime.compareAndSet(time, now);
return lastTime.get();
}
return time;
}
}