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25 package java.util;
26 
27 import java.util.function.IntConsumer;
28 import java.util.function.IntSupplier;
29 import 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  */
45 public 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      */
OptionalInt()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      */
empty()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      */
OptionalInt(int value)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      */
of(int value)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      */
getAsInt()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      */
isPresent()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      */
ifPresent(IntConsumer consumer)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      */
orElse(int other)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      */
orElseGet(IntSupplier other)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      */
orElseThrow(Supplier<X> exceptionSupplier)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
equals(Object obj)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
hashCode()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
toString()244     public String toString() {
245         return isPresent
246                 ? String.format("OptionalInt[%s]", value)
247                 : "OptionalInt.empty";
248     }
249 }
250