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
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23 * questions.
24 */
25package java.util;
26
27import java.util.function.IntConsumer;
28import java.util.function.IntSupplier;
29import java.util.function.Supplier;
30
31// Android-changed: removed ValueBased paragraph.
32/**
33 * A container object which may or may not contain a {@code int} value.
34 * If a value is present, {@code isPresent()} will return {@code true} and
35 * {@code getAsInt()} will return the value.
36 *
37 * <p>Additional methods that depend on the presence or absence of a contained
38 * value are provided, such as {@link #orElse(int) orElse()}
39 * (return a default value if value not present) and
40 * {@link #ifPresent(java.util.function.IntConsumer) ifPresent()} (execute a block
41 * of code if the value is present).
42 *
43 * @since 1.8
44 */
45public final class OptionalInt {
46    /**
47     * Common instance for {@code empty()}.
48     */
49    private static final OptionalInt EMPTY = new OptionalInt();
50
51    /**
52     * If true then the value is present, otherwise indicates no value is present
53     */
54    private final boolean isPresent;
55    private final int value;
56
57    /**
58     * Construct an empty instance.
59     *
60     * @implNote Generally only one empty instance, {@link OptionalInt#EMPTY},
61     * should exist per VM.
62     */
63    private OptionalInt() {
64        this.isPresent = false;
65        this.value = 0;
66    }
67
68    /**
69     * Returns an empty {@code OptionalInt} instance.  No value is present for this
70     * OptionalInt.
71     *
72     * @apiNote Though it may be tempting to do so, avoid testing if an object
73     * is empty by comparing with {@code ==} against instances returned by
74     * {@code Option.empty()}. There is no guarantee that it is a singleton.
75     * Instead, use {@link #isPresent()}.
76     *
77     *  @return an empty {@code OptionalInt}
78     */
79    public static OptionalInt empty() {
80        return EMPTY;
81    }
82
83    /**
84     * Construct an instance with the value present.
85     *
86     * @param value the int value to be present
87     */
88    private OptionalInt(int value) {
89        this.isPresent = true;
90
91        this.value = value;
92    }
93
94    /**
95     * Return an {@code OptionalInt} with the specified value present.
96     *
97     * @param value the value to be present
98     * @return an {@code OptionalInt} with the value present
99     */
100    public static OptionalInt of(int value) {
101        return new OptionalInt(value);
102    }
103
104    /**
105     * If a value is present in this {@code OptionalInt}, returns the value,
106     * otherwise throws {@code NoSuchElementException}.
107     *
108     * @return the value held by this {@code OptionalInt}
109     * @throws NoSuchElementException if there is no value present
110     *
111     * @see OptionalInt#isPresent()
112     */
113    public int getAsInt() {
114        if (!isPresent) {
115            throw new NoSuchElementException("No value present");
116        }
117        return value;
118    }
119
120    /**
121     * Return {@code true} if there is a value present, otherwise {@code false}.
122     *
123     * @return {@code true} if there is a value present, otherwise {@code false}
124     */
125    public boolean isPresent() {
126        return isPresent;
127    }
128
129    /**
130     * Have the specified consumer accept the value if a value is present,
131     * otherwise do nothing.
132     *
133     * @param consumer block to be executed if a value is present
134     * @throws NullPointerException if value is present and {@code consumer} is
135     * null
136     */
137    public void ifPresent(IntConsumer consumer) {
138        if (isPresent)
139            consumer.accept(value);
140    }
141
142    /**
143     * Return the value if present, otherwise return {@code other}.
144     *
145     * @param other the value to be returned if there is no value present
146     * @return the value, if present, otherwise {@code other}
147     */
148    public int orElse(int other) {
149        return isPresent ? value : other;
150    }
151
152    /**
153     * Return the value if present, otherwise invoke {@code other} and return
154     * the result of that invocation.
155     *
156     * @param other a {@code IntSupplier} whose result is returned if no value
157     * is present
158     * @return the value if present otherwise the result of {@code other.getAsInt()}
159     * @throws NullPointerException if value is not present and {@code other} is
160     * null
161     */
162    public int orElseGet(IntSupplier other) {
163        return isPresent ? value : other.getAsInt();
164    }
165
166    /**
167     * Return the contained value, if present, otherwise throw an exception
168     * to be created by the provided supplier.
169     *
170     * @apiNote A method reference to the exception constructor with an empty
171     * argument list can be used as the supplier. For example,
172     * {@code IllegalStateException::new}
173     *
174     * @param <X> Type of the exception to be thrown
175     * @param exceptionSupplier The supplier which will return the exception to
176     * be thrown
177     * @return the present value
178     * @throws X if there is no value present
179     * @throws NullPointerException if no value is present and
180     * {@code exceptionSupplier} is null
181     */
182    public<X extends Throwable> int orElseThrow(Supplier<X> exceptionSupplier) throws X {
183        if (isPresent) {
184            return value;
185        } else {
186            throw exceptionSupplier.get();
187        }
188    }
189
190    /**
191     * Indicates whether some other object is "equal to" this OptionalInt. The
192     * other object is considered equal if:
193     * <ul>
194     * <li>it is also an {@code OptionalInt} and;
195     * <li>both instances have no value present or;
196     * <li>the present values are "equal to" each other via {@code ==}.
197     * </ul>
198     *
199     * @param obj an object to be tested for equality
200     * @return {code true} if the other object is "equal to" this object
201     * otherwise {@code false}
202     */
203    @Override
204    public boolean equals(Object obj) {
205        if (this == obj) {
206            return true;
207        }
208
209        if (!(obj instanceof OptionalInt)) {
210            return false;
211        }
212
213        OptionalInt other = (OptionalInt) obj;
214        return (isPresent && other.isPresent)
215                ? value == other.value
216                : isPresent == other.isPresent;
217    }
218
219    /**
220     * Returns the hash code value of the present value, if any, or 0 (zero) if
221     * no value is present.
222     *
223     * @return hash code value of the present value or 0 if no value is present
224     */
225    @Override
226    public int hashCode() {
227        return isPresent ? Integer.hashCode(value) : 0;
228    }
229
230    /**
231     * {@inheritDoc}
232     *
233     * Returns a non-empty string representation of this object suitable for
234     * debugging. The exact presentation format is unspecified and may vary
235     * between implementations and versions.
236     *
237     * @implSpec If a value is present the result must include its string
238     * representation in the result. Empty and present instances must be
239     * unambiguously differentiable.
240     *
241     * @return the string representation of this instance
242     */
243    @Override
244    public String toString() {
245        return isPresent
246                ? String.format("OptionalInt[%s]", value)
247                : "OptionalInt.empty";
248    }
249}
250