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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.math4.legacy.genetics;
18  
19  import java.util.ArrayList;
20  import java.util.List;
21  
22  import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException;
23  import org.apache.commons.math4.legacy.exception.util.LocalizedFormats;
24  
25  /**
26   * Mutation for {@link BinaryChromosome}s. Randomly changes one gene.
27   *
28   * @since 2.0
29   */
30  public class BinaryMutation implements MutationPolicy {
31  
32      /**
33       * Mutate the given chromosome. Randomly changes one gene.
34       *
35       * @param original the original chromosome.
36       * @return the mutated chromosome.
37       * @throws MathIllegalArgumentException if <code>original</code> is not an instance of {@link BinaryChromosome}.
38       */
39      @Override
40      public Chromosome mutate(Chromosome original) throws MathIllegalArgumentException {
41          if (!(original instanceof BinaryChromosome)) {
42              throw new MathIllegalArgumentException(LocalizedFormats.INVALID_BINARY_CHROMOSOME);
43          }
44  
45          BinaryChromosome origChrom = (BinaryChromosome) original;
46          List<Integer> newRepr = new ArrayList<>(origChrom.getRepresentation());
47  
48          // randomly select a gene
49          int geneIndex = GeneticAlgorithm.getRandomGenerator().nextInt(origChrom.getLength());
50          // and change it
51          newRepr.set(geneIndex, origChrom.getRepresentation().get(geneIndex) == 0 ? 1 : 0);
52  
53          return origChrom.newFixedLengthChromosome(newRepr);
54      }
55  }