001/*
002 * Java Genetic Algorithm Library (jenetics-8.1.0).
003 * Copyright (c) 2007-2024 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 * Author:
018 *    Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
019 */
020package io.jenetics.util;
021
022/**
023 * A mixin interface for genes which can have a mean value. This mixin is
024 * required for the {@link io.jenetics.MeanAlterer}.
025 *
026 * @see io.jenetics.MeanAlterer
027 *
028 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
029 * @since 1.0
030 * @version 1.6
031 */
032public interface Mean<T> {
033
034        /**
035         * Return the (usually arithmetic) mean value of {@code this} and
036         * {@code that}. For {@link io.jenetics.NumericGene}s the mean is the
037         * arithmetic mean.
038         *
039         * @param that the second value for calculating the mean.
040         * @return the mean value of {@code this} and {@code that}.
041         * @throws NullPointerException if the argument is {@code null}.
042         */
043        T mean(final T that);
044
045}