    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.math3.genetics;
    018
    019    import java.util.ArrayList;
    020    import java.util.List;
    021
    022    import org.apache.commons.math3.exception.MathIllegalArgumentException;
    023    import org.apache.commons.math3.exception.util.LocalizedFormats;
    024
    025    /**
    026     * Mutation for {@link BinaryChromosome}s. Randomly changes one gene.
    027     *
    028     * @version $Id: BinaryMutation.java 1416643 2012-12-03 19:37:14Z tn $
    029     * @since 2.0
    030     */
    031    public class BinaryMutation implements MutationPolicy {
    032
    033        /**
    034         * Mutate the given chromosome. Randomly changes one gene.
    035         *
    036         * @param original the original chromosome.
    037         * @return the mutated chromosome.
    038         * @throws MathIllegalArgumentException if <code>original</code> is not an instance of {@link BinaryChromosome}.
    039         */
    040        public Chromosome mutate(Chromosome original) throws MathIllegalArgumentException {
    041            if (!(original instanceof BinaryChromosome)) {
    042                throw new MathIllegalArgumentException(LocalizedFormats.INVALID_BINARY_CHROMOSOME);
    043            }
    044
    045            BinaryChromosome origChrom = (BinaryChromosome) original;
    046            List<Integer> newRepr = new ArrayList<Integer>(origChrom.getRepresentation());
    047
    048            // randomly select a gene
    049            int geneIndex = GeneticAlgorithm.getRandomGenerator().nextInt(origChrom.getLength());
    050            // and change it
    051            newRepr.set(geneIndex, origChrom.getRepresentation().get(geneIndex) == 0 ? 1 : 0);
    052
    053            Chromosome newChrom = origChrom.newFixedLengthChromosome(newRepr);
    054            return newChrom;
    055        }
    056
    057    }