com.hazelcast.util.ItemCounter Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2015, 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.util;
import java.util.HashMap;
import java.util.Map;
/**
* Non Thread-Safe Counter of things. It allows to count items without worrying about nulls.
*
* @param
*/
public final class ItemCounter {
private final Map map = new HashMap();
/**
* Get current counter for an item item
*
* @param item
* @return current state of a counter for item
*/
public long get(T item) {
MutableLong count = map.get(item);
return count == null ? 0 : count.value;
}
/**
* Set counter of item to value
*
* @param item to set set the value for
* @param value a new value
*/
public void set(T item, long value) {
MutableLong entry = map.get(item);
if (entry == null) {
entry = MutableLong.valueOf(value);
map.put(item, entry);
} else {
entry.value = value;
}
}
/**
* Add delta to the item
*
* @param item
* @param delta
*/
public void add(T item, long delta) {
MutableLong entry = map.get(item);
if (entry == null) {
entry = MutableLong.valueOf(delta);
map.put(item, entry);
} else {
entry.value += delta;
}
}
/**
* Reset state of the counter to 0.
* It will NOT necessary remove all data referenced.
*
* Time complexity of this operation is O(n) where n is number of items.
*
*/
public void reset() {
for (MutableLong entry : map.values()) {
entry.value = 0;
}
}
/**
* Set counter for item and return previous value
*
* @param item
* @param value
* @return
*/
public long getAndSet(T item, long value) {
MutableLong entry = map.get(item);
if (entry == null) {
entry = MutableLong.valueOf(value);
map.put(item, entry);
return 0;
}
long oldValue = entry.value;
entry.value = value;
return oldValue;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
ItemCounter that = (ItemCounter) o;
if (!map.equals(that.map)) {
return false;
}
return true;
}
@Override
public int hashCode() {
return map.hashCode();
}
}