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 * https://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
18 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22
23 package org.hipparchus.geometry.spherical.twod;
24
25 import java.io.Serializable;
26
27 import org.hipparchus.exception.MathIllegalArgumentException;
28 import org.hipparchus.geometry.LocalizedGeometryFormats;
29 import org.hipparchus.geometry.Space;
30 import org.hipparchus.geometry.spherical.oned.Sphere1D;
31 import org.hipparchus.util.FastMath;
32
33 /**
34 * This class implements a two-dimensional sphere (i.e. the regular sphere).
35 * <p>
36 * We use here the topologists definition of the 2-sphere (see
37 * <a href="http://mathworld.wolfram.com/Sphere.html">Sphere</a> on
38 * MathWorld), i.e. the 2-sphere is the two-dimensional surface
39 * defined in 3D as x<sup>2</sup>+y<sup>2</sup>+z<sup>2</sup>=1.
40 * </p>
41 */
42 public class Sphere2D implements Serializable, Space {
43
44 /** Smallest tolerance that can be managed.
45 * <p>
46 * Tolerances smaller than this value will generate exceptions.
47 * </p>
48 * @since 1.4
49 */
50 public static final double SMALLEST_TOLERANCE = FastMath.ulp(2 * FastMath.PI);
51
52 /** Serializable version identifier. */
53 private static final long serialVersionUID = 20131218L;
54
55 /** Private constructor for the singleton.
56 */
57 private Sphere2D() {
58 }
59
60 /** Get the unique instance.
61 * @return the unique instance
62 */
63 public static Sphere2D getInstance() {
64 return LazyHolder.INSTANCE;
65 }
66
67 /** Check tolerance against {@link #SMALLEST_TOLERANCE}.
68 * @param tolerance tolerance to check
69 * @exception MathIllegalArgumentException if tolerance is smaller
70 * than {@link #SMALLEST_TOLERANCE}
71 */
72 public static void checkTolerance(final double tolerance)
73 throws MathIllegalArgumentException {
74 if (tolerance < Sphere1D.SMALLEST_TOLERANCE) {
75 throw new MathIllegalArgumentException(LocalizedGeometryFormats.TOO_SMALL_TOLERANCE,
76 tolerance, "Sphere2D.SMALLEST_TOLERANCE", SMALLEST_TOLERANCE);
77 }
78 }
79
80 /** {@inheritDoc} */
81 @Override
82 public int getDimension() {
83 return 2;
84 }
85
86 /** {@inheritDoc} */
87 @Override
88 public Sphere1D getSubSpace() {
89 return Sphere1D.getInstance();
90 }
91
92 // CHECKSTYLE: stop HideUtilityClassConstructor
93 /** Holder for the instance.
94 * <p>We use here the Initialization On Demand Holder Idiom.</p>
95 */
96 private static class LazyHolder {
97 /** Cached field instance. */
98 private static final Sphere2D INSTANCE = new Sphere2D();
99 }
100 // CHECKSTYLE: resume HideUtilityClassConstructor
101
102 /** Handle deserialization of the singleton.
103 * @return the singleton instance
104 */
105 private Object readResolve() {
106 // return the singleton instance
107 return LazyHolder.INSTANCE;
108 }
109
110 }