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    
024    /**
025     * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
026     * of the array representation to a random value uniformly distributed in [0,1].
027     *
028     * @since 2.0
029     * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
030     */
031    public class RandomKeyMutation implements MutationPolicy {
032    
033        /**
034         * {@inheritDoc}
035         *
036         * @throws IllegalArgumentException if <code>original</code> is not a
037         * {@link RandomKey} instance
038         */
039        public Chromosome mutate(Chromosome original) {
040            if (!(original instanceof RandomKey<?>)) {
041                throw MathRuntimeException.createIllegalArgumentException(
042                        "RandomKeyMutation works only with RandomKeys, got " +
043                        original.getClass().getSimpleName());
044            }
045    
046            RandomKey<?> originalRk = (RandomKey<?>) original;
047            List<Double> repr = originalRk.getRepresentation();
048            int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
049    
050            List<Double> newRepr = new ArrayList<Double> (repr);
051            newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
052    
053            return originalRk.newFixedLengthChromosome(newRepr);
054        }
055    
056    }