com.cloudhopper.commons.util.Sequencer Maven / Gradle / Ivy
package com.cloudhopper.commons.util;
/*
* #%L
* ch-commons-util
* %%
* Copyright (C) 2012 Cloudhopper by Twitter
* %%
* 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.
* #L%
*/
import java.util.concurrent.atomic.AtomicLong;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This class implements an extremely efficient, thread-safe way to generate a
* simple incrementing sequence of Longs. This class safely resets the sequence
* back to zero to prevent overflow. Internally uses the AtomicLong class.
*
* @author joelauer (twitter: @jjlauer or http://twitter.com/jjlauer)
*/
public class Sequencer {
private static Logger logger = LoggerFactory.getLogger(Sequencer.class);
private AtomicLong sequenceNumber;
/**
* Constructs a new instance of Sequencer a default starting
* sequence number of 0.
*/
public Sequencer() {
sequenceNumber = new AtomicLong(0);
}
/**
* Constructs a new instance of Sequencer with the specified
* starting value.
*/
public Sequencer(long startingValue) {
sequenceNumber = new AtomicLong(startingValue);
}
public long next() {
long seqNum = sequenceNumber.getAndIncrement();
// check if this value is getting close to overflow?
if (seqNum > Long.MAX_VALUE-1000000000) {
sequenceNumber.set(0);
}
return seqNum;
}
}