    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  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    package org.apache.commons.math.genetics;
    018
    019    import java.util.ArrayList;
    020    import java.util.List;
    021
    022    import org.apache.commons.math.MathRuntimeException;
    023    import org.apache.commons.math.exception.util.LocalizedFormats;
    024
    025    /**
    026     * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
    027     * of the array representation to a random value uniformly distributed in [0,1].
    028     *
    029     * @since 2.0
    030     * @version $Revision: 983921 $ $Date: 2010-08-10 12:46:06 +0200 (mar. 10 ao??t 2010) $
    031     */
    032    public class RandomKeyMutation implements MutationPolicy {
    033
    034        /**
    035         * {@inheritDoc}
    036         *
    037         * @throws IllegalArgumentException if <code>original</code> is not a
    038         * {@link RandomKey} instance
    039         */
    040        public Chromosome mutate(Chromosome original) {
    041            if (!(original instanceof RandomKey<?>)) {
    042                throw MathRuntimeException.createIllegalArgumentException(
    043                        LocalizedFormats.RANDOMKEY_MUTATION_WRONG_CLASS,
    044                        original.getClass().getSimpleName());
    045            }
    046
    047            RandomKey<?> originalRk = (RandomKey<?>) original;
    048            List<Double> repr = originalRk.getRepresentation();
    049            int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
    050
    051            List<Double> newRepr = new ArrayList<Double> (repr);
    052            newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
    053
    054            return originalRk.newFixedLengthChromosome(newRepr);
    055        }
    056
    057    }