net.sf.ehcache.search.aggregator.Average Maven / Gradle / Ivy
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/**
* Copyright Terracotta, Inc.
*
* 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 net.sf.ehcache.search.aggregator;
import net.sf.ehcache.search.Attribute;
/**
* Compute the average (arithmetic mean) as a double
*
* @author teck
*/
public class Average implements AggregatorInstance {
private final Attribute attribute;
private Engine engine;
/**
* @param attribute
*/
public Average(Attribute attribute) {
this.attribute = attribute;
}
/**
* {@inheritDoc}
*/
public Average createClone() {
return new Average(attribute);
}
/**
* {@inheritDoc}
*
* NOTE: Null values are ignored and not included in the computation
*/
public void accept(Object input) throws AggregatorException {
if (input == null) {
return;
}
if (input instanceof Number) {
if (engine == null) {
engine = Engine.create((Number) input);
} else {
engine.accept((Number) input);
}
} else {
throw new AggregatorException("Non-number type encountered: " + input.getClass());
}
}
/**
* {@inheritDoc}
*
* NOTE: null is returned if there was no input supplied to this function
*/
public Number aggregateResult() {
if (engine == null) {
return null;
} else {
return engine.result();
}
}
/**
* {@inheritDoc}
*/
public Attribute getAttribute() {
return attribute;
}
/**
* Abstract super-class for all average calculating engines.
*/
abstract static class Engine {
/**
* Create a type specific engine using the given initial value.
*
* @param value initial value
* @return type specific engine
*/
static Engine create(Number value) {
if (value instanceof Float) {
return new FloatEngine(value.floatValue());
} else if (value instanceof Double) {
return new DoubleEngine(value.doubleValue());
} else if (value instanceof Long) {
return new LongEngine(value.longValue());
} else {
return new IntegerEngine(value.intValue());
}
}
/**
* Update the engine with the given value.
*
* @param input data value
*/
abstract void accept(Number input) throws AggregatorException;
/**
* Get the (current) result of this engine.
*
* @return engine result
*/
abstract Number result();
/**
* An int based averaging engine.
*/
static class IntegerEngine extends Engine {
private int count;
private long sum;
/**
* Creates a new instance starting with an initial value
*
* @param value initial value
*/
IntegerEngine(int value) {
this.count = 1;
this.sum = value;
}
@Override
void accept(Number input) throws AggregatorException {
count++;
sum += input.intValue();
}
@Override
Number result() {
return Float.valueOf(((float) sum) / count);
}
}
/**
* A long based averaging engine.
*/
static class LongEngine extends Engine {
private int count;
private long sum;
/**
* Creates a new instance starting with an initial value
*
* @param value initial value
*/
LongEngine(long value) {
this.count = 1;
this.sum = value;
}
@Override
void accept(Number input) throws AggregatorException {
count++;
sum += input.longValue();
}
@Override
Number result() {
return Double.valueOf(((double) sum) / count);
}
}
/**
* A float based averaging engine.
*/
static class FloatEngine extends Engine {
private int count;
private float sum;
/**
* Creates a new instance starting with an initial value
*
* @param value initial value
*/
FloatEngine(float value) {
this.count = 1;
this.sum = value;
}
@Override
void accept(Number input) throws AggregatorException {
count++;
sum += input.floatValue();
}
@Override
Number result() {
return Float.valueOf(sum / count);
}
}
/**
* A double based averaging engine.
*/
static class DoubleEngine extends Engine {
private int count;
private double sum;
/**
* Creates a new instance starting with an initial value
*
* @param value initial value
*/
DoubleEngine(double value) {
this.count = 1;
this.sum = value;
}
@Override
void accept(Number input) throws AggregatorException {
count++;
sum += input.doubleValue();
}
@Override
Number result() {
return Double.valueOf(sum / count);
}
}
}
}