com.hazelcast.internal.util.counters.MwCounter Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2018, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.internal.util.counters;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import static java.util.concurrent.atomic.AtomicLongFieldUpdater.newUpdater;
/**
* A {@link Counter} that is thread-safe; so can be incremented by multiple threads concurrently.
*
* The MwCounter is not meant for a huge amount of contention. In that case it would be better to create a counter
* on the {@link java.util.concurrent.atomic.LongAdder}.
*
* This counter does not provide padding to prevent false sharing.
*/
public final class MwCounter implements Counter {
private static final AtomicLongFieldUpdater COUNTER = newUpdater(MwCounter.class, "value");
private volatile long value;
private MwCounter(long initialValue) {
this.value = initialValue;
}
@Override
public long get() {
return value;
}
@Override
public long inc() {
return COUNTER.incrementAndGet(this);
}
@Override
public long inc(long amount) {
return COUNTER.addAndGet(this, amount);
}
@Override
public String toString() {
return "Counter{"
+ "value=" + value
+ '}';
}
/**
* Creates a new MwCounter with 0 as its initial value.
*
* @return the new MwCounter, set to 0.
*/
public static MwCounter newMwCounter() {
return newMwCounter(0);
}
/**
* Creates a new MwCounter with the given initial value.
*
* @param initialValue the initial value of the counter.
* @return the new MwCounter, set to the given initial value.
*/
public static MwCounter newMwCounter(long initialValue) {
return new MwCounter(initialValue);
}
}