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    }