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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.math.genetics;
18  
19  import java.util.ArrayList;
20  import java.util.List;
21  
22  import org.apache.commons.math.MathRuntimeException;
23  
24  /**
25   * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
26   * of the array representation to a random value uniformly distributed in [0,1].
27   * 
28   * @since 2.0
29   * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $
30   */
31  public class RandomKeyMutation implements MutationPolicy {
32  
33      /**
34       * {@inheritDoc}
35       * 
36       * @throws IllegalArgumentException if <code>original</code> is not a 
37       * {@link RandomKey} instance
38       */
39      public Chromosome mutate(Chromosome original) {
40          if (!(original instanceof RandomKey<?>)) {
41              throw MathRuntimeException.createIllegalArgumentException(
42                      "RandomKeyMutation works only with RandomKeys, got " +
43                      original.getClass().getSimpleName());
44          }
45          
46          RandomKey<?> originalRk = (RandomKey<?>) original;
47          List<Double> repr = originalRk.getRepresentation();
48          int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
49          
50          List<Double> newRepr = new ArrayList<Double> (repr);
51          newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
52          
53          return originalRk.newFixedLengthChromosome(newRepr);
54      }
55  
56  }