1 package net.bmahe.genetics4j.core.chromosomes;
2
3 import java.util.Arrays;
4
5 import org.apache.commons.lang3.Validate;
6
7 /**
8 * A chromosome implementation that represents genetic information as an array of integer values.
9 *
10 * <p>IntChromosome is widely used for discrete optimization problems where solutions can be
11 * encoded as sequences of integer values within specified ranges. Each position in the array
12 * represents a gene, and the integer value at that position represents the allele.
13 *
14 * <p>This chromosome type is particularly suitable for:
15 * <ul>
16 * <li><strong>Combinatorial optimization</strong>: Problems with discrete decision variables</li>
17 * <li><strong>Parameter optimization</strong>: Integer hyperparameters, configuration settings</li>
18 * <li><strong>Permutation encoding</strong>: When combined with appropriate operators</li>
19 * <li><strong>Resource allocation</strong>: Assignment and scheduling problems</li>
20 * <li><strong>Graph problems</strong>: Node labeling, path encoding</li>
21 * </ul>
22 *
23 * <p>Key features:
24 * <ul>
25 * <li><strong>Bounded values</strong>: All integers are constrained to [minValue, maxValue]</li>
26 * <li><strong>Fixed length</strong>: Chromosome size is determined at creation time</li>
27 * <li><strong>Immutable</strong>: Values cannot be changed after construction</li>
28 * <li><strong>Type-safe</strong>: Compile-time guarantees for integer operations</li>
29 * </ul>
30 *
31 * <p>The chromosome maintains bounds information which is used by genetic operators
32 * to ensure that crossover and mutation operations produce valid offspring within
33 * the specified constraints.
34 *
35 * @see Chromosome
36 * @see net.bmahe.genetics4j.core.spec.chromosome.IntChromosomeSpec
37 * @see net.bmahe.genetics4j.core.chromosomes.factory.IntChromosomeFactory
38 */
39 public class IntChromosome implements Chromosome {
40
41 private final int size;
42 private final int minValue;
43 private final int maxValue;
44 private final int[] values;
45
46 /**
47 * Creates a new integer chromosome with the specified parameters and values.
48 *
49 * @param _size the number of integer values in this chromosome
50 * @param _minValue the minimum allowed value for any integer in this chromosome
51 * @param _maxValue the maximum allowed value for any integer in this chromosome
52 * @param _values the array of integer values for this chromosome
53 * @throws IllegalArgumentException if size is not positive, if minValue > maxValue,
54 * if values array is null, or if the array length
55 * doesn't match the specified size
56 */
57 public IntChromosome(final int _size, final int _minValue, final int _maxValue, final int[] _values) {
58 Validate.isTrue(_size > 0);
59 Validate.isTrue(_minValue <= _maxValue);
60 Validate.notNull(_values);
61 Validate.isTrue(_size == _values.length, "Provided size does not match the size of the content");
62
63 this.size = _size;
64 this.minValue = _minValue;
65 this.maxValue = _maxValue;
66 this.values = Arrays.copyOf(_values, _size);
67 }
68
69 @Override
70 public int getNumAlleles() {
71 return size;
72 }
73
74 /**
75 * Returns the integer value at the specified index.
76 *
77 * @param index the index of the allele to retrieve (0-based)
78 * @return the integer value at the specified position
79 * @throws IllegalArgumentException if index is negative or greater than or equal to the chromosome size
80 */
81 public int getAllele(final int index) {
82 Validate.inclusiveBetween(0, size - 1, index);
83
84 return values[index];
85 }
86
87 /**
88 * Returns the number of integer values in this chromosome.
89 *
90 * @return the chromosome size
91 */
92 public int getSize() {
93 return size;
94 }
95
96 /**
97 * Returns the minimum allowed value for integers in this chromosome.
98 *
99 * @return the minimum value constraint
100 */
101 public int getMinValue() {
102 return minValue;
103 }
104
105 /**
106 * Returns the maximum allowed value for integers in this chromosome.
107 *
108 * @return the maximum value constraint
109 */
110 public int getMaxValue() {
111 return maxValue;
112 }
113
114 /**
115 * Returns a copy of the integer values in this chromosome.
116 *
117 * <p>The returned array is a defensive copy; modifications to it will not
118 * affect this chromosome.
119 *
120 * @return a copy of the integer values array
121 */
122 public int[] getValues() {
123 return values;
124 }
125
126 @Override
127 public int hashCode() {
128 final int prime = 31;
129 int result = 1;
130 result = prime * result + maxValue;
131 result = prime * result + minValue;
132 result = prime * result + size;
133 result = prime * result + Arrays.hashCode(values);
134 return result;
135 }
136
137 @Override
138 public boolean equals(Object obj) {
139 if (this == obj)
140 return true;
141 if (obj == null)
142 return false;
143 if (getClass() != obj.getClass())
144 return false;
145 IntChromosome other = (IntChromosome) obj;
146 if (maxValue != other.maxValue)
147 return false;
148 if (minValue != other.minValue)
149 return false;
150 if (size != other.size)
151 return false;
152 if (!Arrays.equals(values, other.values))
153 return false;
154 return true;
155 }
156
157 @Override
158 public String toString() {
159 return "IntChromosome [size=" + size + ", minValue=" + minValue + ", maxValue=" + maxValue + ", values="
160 + Arrays.toString(values) + "]";
161 }
162 }