bitronix.tm.utils.MonotonicClock Maven / Gradle / Ivy
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/*
* Bitronix Transaction Manager
*
* Copyright (c) 2011, Bitronix Software.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package bitronix.tm.utils;
import java.util.concurrent.atomic.AtomicLong;
/**
* A System.currentTimeMillis() replacement which guarantees monotonic time increment.
*
* @author lorban
*/
public class MonotonicClock {
private static final AtomicLong lastTime = new AtomicLong();
/**
* Return the current time in milliseconds, guaranteeing monotonic time increment.
* @return the current time in milliseconds.
*/
public static long currentTimeMillis() {
long now = System.nanoTime() / 1000000;
long time = lastTime.get();
if (now > time) {
lastTime.compareAndSet(time, now);
return lastTime.get();
}
return time;
}
}