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.geometry.core.precision;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.numbers.core.Precision;
22
23 /** Simple {@link DoublePrecisionContext} subclass that uses an absolute epsilon value to
24 * determine equality between doubles.
25 *
26 * <p>This class uses the {@link Precision#compareTo(double, double, double)} method to compare
27 * numbers. Two values are considered equal if there is no floating point
28 * value strictly between them or if their numerical difference is less than or equal
29 * to the configured epsilon value.</p>
30 *
31 * @see Precision#compareTo(double, double, double)
32 */
33 public class EpsilonDoublePrecisionContext extends DoublePrecisionContext implements Serializable {
34 private static final long serialVersionUID = 1L;
35
36 /** Epsilon value. */
37 private final double epsilon;
38
39 /** Simple constructor.
40 * @param eps Epsilon value. Numbers are considered equal if there is no
41 * floating point value strictly between them or if their difference is less
42 * than or equal to this value.
43 * @throws IllegalArgumentException if the given epsilon value is infinite, NaN, or negative
44 */
45 public EpsilonDoublePrecisionContext(final double eps) {
46 if (!Double.isFinite(eps) || eps < 0.0) {
47 throw new IllegalArgumentException("Invalid epsilon value: " + eps);
48 }
49 this.epsilon = eps;
50 }
51
52 /** Get the epsilon value for the instance. Numbers are considered equal if there
53 * is no floating point value strictly between them or if their difference is less
54 * than or equal to this value.
55 * @return the epsilon value for the instance
56 */
57 public double getEpsilon() {
58 return epsilon;
59 }
60
61 /** {@inheritDoc}
62 * This value is equal to the epsilon value for the instance.
63 * @see #getEpsilon()
64 */
65 @Override
66 public double getMaxZero() {
67 return getEpsilon();
68 }
69
70 /** {@inheritDoc} **/
71 @Override
72 public int compare(final double a, final double b) {
73 return Precision.compareTo(a, b, epsilon);
74 }
75
76 /** {@inheritDoc} **/
77 @Override
78 public int hashCode() {
79 int result = 31;
80 result += 17 * Double.hashCode(epsilon);
81
82 return result;
83 }
84
85 /** {@inheritDoc} **/
86 @Override
87 public boolean equals(final Object obj) {
88 if (this == obj) {
89 return true;
90 }
91 if (!(obj instanceof EpsilonDoublePrecisionContext)) {
92 return false;
93 }
94
95 final EpsilonDoublePrecisionContext other = (EpsilonDoublePrecisionContext) obj;
96
97 return Double.compare(this.epsilon, other.epsilon) == 0;
98 }
99
100 /** {@inheritDoc} **/
101 @Override
102 public String toString() {
103 final StringBuilder sb = new StringBuilder();
104 sb.append(this.getClass().getSimpleName())
105 .append("[")
106 .append("epsilon= ")
107 .append(epsilon)
108 .append("]");
109
110 return sb.toString();
111 }
112 }