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    }