    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    /**
    023     * Mutation for {@link BinaryChromosome}s. Randomly changes one gene.
    024     *
    025     * @version $Revision: 811685 $ $Date: 2009-09-05 19:36:48 +0200 (sam. 05 sept. 2009) $
    026     * @since 2.0
    027     */
    028    public class BinaryMutation implements MutationPolicy {
    029
    030        /**
    031         * Mutate the given chromosome. Randomly changes one gene.
    032         * @param original the original chromosome.
    033         * @return the mutated chromomsome.
    034         */
    035        public Chromosome mutate(Chromosome original) {
    036            if (!(original instanceof BinaryChromosome)) {
    037                throw new IllegalArgumentException("Binary mutation works on BinaryChromosome only.");
    038            }
    039
    040            BinaryChromosome origChrom = (BinaryChromosome) original;
    041            List<Integer> newRepr = new ArrayList<Integer>(origChrom.getRepresentation());
    042
    043            // randomly select a gene
    044            int geneIndex = GeneticAlgorithm.getRandomGenerator().nextInt(origChrom.getLength());
    045            // and change it
    046            newRepr.set(geneIndex, origChrom.getRepresentation().get(geneIndex) == 0 ? 1 : 0);
    047
    048            Chromosome newChrom = origChrom.newFixedLengthChromosome(newRepr);
    049            return newChrom;
    050        }
    051
    052    }