1 /*
2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package java.util;
26
27 import java.util.function.DoubleConsumer;
28 import java.util.function.DoubleSupplier;
29 import java.util.function.Supplier;
30
31 /**
32 * A container object which may or may not contain a {@code double} value.
33 * If a value is present, {@code isPresent()} will return {@code true} and
34 * {@code get()} will return the value.
35 *
36 * <p>Additional methods that depend on the presence or absence of a contained
37 * value are provided, such as {@link #orElse(java.lang.Object) orElse()}
38 * (return a default value if value not present) and
39 * {@link #ifPresent(java.util.function.Consumer) ifPresent()} (execute a block
40 * of code if the value is present.)
41 *
42 * @since 1.8
43 */
44 public final class OptionalDouble {
45 /**
46 * Common instance for {@code empty()}.
47 */
48 private final static OptionalDouble EMPTY = new OptionalDouble();
49
50 /**
51 * If true then the value is present, otherwise indicates no value is present
52 */
53 private final boolean isPresent;
54 private final double value;
55
56 /**
57 * Construct a non-empty instance
58 *
59 * @param value the double value to be present.
60 */
61 private OptionalDouble(double value) {
62 this.isPresent = true;
63 this.value = value;
64 }
65
66 /**
67 * Construct an empty instance.
68 *
69 * @implNote generally only one empty instance, {@link OptionalDouble#EMPTY},
70 * should exist per VM.
71 */
72 private OptionalDouble() {
73 this.isPresent = false;
74 this.value = Double.NaN;
75 }
76
77 /**
78 * Return an empty {@code OptionalDouble}. No value is present for this Optional.
79 *
80 * @apiNote Though it may be tempting to do so, avoid testing if an object
81 * is empty by comparing with {@code ==} against instances returned
82 * {@code Option.empty()}. There is no guarantee that it is a singleton.
83 * Instead, use {@code isPresent()}.
84 *
85 * @return an empty {@code OptionalDouble}.
86 */
87 @SuppressWarnings("unchecked")
88 public static OptionalDouble empty() {
89 return EMPTY;
90 }
91
92 /**
93 * Create a new {@code OptionalDouble} with a present value
94 * @param value The double value
95 * @param value new {@code OptionalDouble} with a present value.
96 */
97 public static OptionalDouble of(double value) {
98 return new OptionalDouble(value);
99 }
100
101 /**
102 * If a value is present in this {@code OptionalDouble}, returns the value,
103 * otherwise throws {@code NoSuchElementException}.
104 *
105 * @return the value held by this {@code OptionalDouble}.
106 * @throws NoSuchElementException if there is no value present.
107 *
108 * @see OptionalDouble#isPresent()
109 */
110 public double getAsDouble() {
111 if (!isPresent) {
112 throw new NoSuchElementException("No value present");
113 }
114 return value;
115 }
116
117 /**
118 * Return {@code true} if there is a value present, otherwise {@code false}.
119 *
120 * @return {@code true} if there is a value present, otherwise {@code false}.
121 */
122 public boolean isPresent() {
123 return isPresent;
124 }
125
126 /**
127 * Execute the specified consumer with the value if a value is present,
128 * otherwise do nothing.
129 *
130 * @param consumer block to be executed if a value is present.
131 * @throws NullPointerException if value is present and {@code consumer} is
132 * null.
133 */
134 public void ifPresent(DoubleConsumer consumer) {
135 if (isPresent)
136 consumer.accept(value);
137 }
138
139 /**
140 * Return the value if present, otherwise return {@code other}.
141 *
142 * @param other value to be returned if there is no value present.
143 * @return the value, if present, otherwise {@code other}.
144 */
145 public double orElse(double other) {
146 return isPresent ? value : other;
147 }
148
149 /**
150 * Return the value if present, otherwise invoke {@code other} and return
151 * the result of that invocation.
152 *
153 * @param other {@code DoubleSupplier} who's result is returned if there is no
154 * value present.
155 * @return the value if present otherwise return result of {@code other}.
156 * @throws NullPointerException if value is absent and {@code other} is null.
157 */
158 public double orElseGet(DoubleSupplier other) {
159 return isPresent ? value : other.getAsDouble();
160 }
161
162 /**
163 * Return the contained value, if present, otherwise throw an exception
164 * to be created by the provided supplier.
165 *
166 * @param <V> Type of the exception to be thrown.
167 * @param exceptionSupplier The supplier which will return the exception to
168 * be thrown.
169 * @return the value.
170 * @throws V if there is no value present.
171 * @throws NullPointerException if value is absent and
172 * {@code exceptionSupplier} is null.
173 */
174 public<V extends Throwable> double orElseThrow(Supplier<V> exceptionSupplier) throws V {
175 if (isPresent) {
176 return value;
177 } else {
178 throw exceptionSupplier.get();
179 }
180 }
181
182 @Override
183 public boolean equals(Object o) {
184 if (this == o) {
185 return true;
186 }
187
188 if (!(o instanceof OptionalDouble)) {
189 return false;
190 }
191
192 OptionalDouble other = (OptionalDouble) o;
193 return (isPresent && other.isPresent)
194 ? Double.compare(value, other.value) == 0
195 : isPresent == other.isPresent;
196 }
197
198 @Override
199 public int hashCode() {
200 return Double.hashCode(value);
201 }
202
203 @Override
204 public String toString() {
205 return isPresent
206 ? String.format("DoubleOptional[%s]", value)
207 : "DoubleOptional.empty";
208 }
209 }