org.modeshape.jcr.api.monitor.Statistics Maven / Gradle / Ivy
/*
* ModeShape (http://www.modeshape.org)
*
* 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 org.modeshape.jcr.api.monitor;
/**
* The immutable statistics for a sample of values. The statistics include the {@link #getMinimum() minimum},
* {@link #getMaximum() maximum}, {@link #getMean() mean (average)}, {@link #getVariance() variance} and
* {@link #getStandardDeviation() standard deviation}.
*
* The median value is not included in these statistics, since the median value cannot be rolled up given a series of statistics
* without having the original values. It is possible to compute the weighted median, but this loses effectiveness/value the more
* times it is rolled up.
*
*
* @since 3.0
*/
public interface Statistics {
/**
* An empty statistics array.
*/
Statistics[] NO_STATISTICS = new Statistics[0];
/**
* Get the number of samples to which these statistics apply.
*
* @return the number of samples; never negative
*/
int getCount();
/**
* Get the maximum of the sampled values.
*
* @return the maximum value
*/
long getMaximum();
/**
* Get the minimum of the sampled values.
*
* @return the minimum value
*/
long getMinimum();
/**
* The mean (or average) of the sampled values. This is returned as a double to reduce the lost of precision.
*
* @return the mean or average value
*/
double getMean();
/**
* Get the variance of the sampled values, which is the average of the squared differences from the {@link #getMean() mean}.
*
* @return the variance; never negative
*/
double getVariance();
/**
* Get the standard deviation of the sampled values, which is a measure of how spread out the numbers are and is the square
* root of the {@link #getVariance() variance}.
*
* @return the standard deviation; never negative
*/
double getStandardDeviation();
}