Additional methods that depend on the presence or absence of a contained + * value are provided, such as {@link #orElse(int) orElse()} + * (return a default value if value not present) and + * {@link #ifPresent(java.util.function.IntConsumer) ifPresent()} (execute a block + * of code if the value is present). + * + *
This is a value-based
+ * class; use of identity-sensitive operations (including reference equality
+ * ({@code ==}), identity hash code, or synchronization) on instances of
+ * {@code OptionalInt} may have unpredictable results and should be avoided.
+ *
+ * @since 1.8
+ */
+public final class OptionalInt {
+ /**
+ * Common instance for {@code empty()}.
+ */
+ private static final OptionalInt EMPTY = new OptionalInt();
+
+ /**
+ * If true then the value is present, otherwise indicates no value is present
+ */
+ private final boolean isPresent;
+ private final int value;
+
+ /**
+ * Construct an empty instance.
+ *
+ * @implNote Generally only one empty instance, {@link OptionalInt#EMPTY},
+ * should exist per VM.
+ */
+ private OptionalInt() {
+ this.isPresent = false;
+ this.value = 0;
+ }
+
+ /**
+ * Returns an empty {@code OptionalInt} instance. No value is present for this
+ * OptionalInt.
+ *
+ * @apiNote Though it may be tempting to do so, avoid testing if an object
+ * is empty by comparing with {@code ==} against instances returned by
+ * {@code Option.empty()}. There is no guarantee that it is a singleton.
+ * Instead, use {@link #isPresent()}.
+ *
+ * @return an empty {@code OptionalInt}
+ */
+ public static OptionalInt empty() {
+ return EMPTY;
+ }
+
+ /**
+ * Construct an instance with the value present.
+ *
+ * @param value the int value to be present
+ */
+ private OptionalInt(int value) {
+ this.isPresent = true;
+ this.value = value;
+ }
+
+ /**
+ * Return an {@code OptionalInt} with the specified value present.
+ *
+ * @param value the value to be present
+ * @return an {@code OptionalInt} with the value present
+ */
+ public static OptionalInt of(int value) {
+ return new OptionalInt(value);
+ }
+
+ /**
+ * If a value is present in this {@code OptionalInt}, returns the value,
+ * otherwise throws {@code NoSuchElementException}.
+ *
+ * @return the value held by this {@code OptionalInt}
+ * @throws NoSuchElementException if there is no value present
+ *
+ * @see OptionalInt#isPresent()
+ */
+ public int getAsInt() {
+ if (!isPresent) {
+ throw new NoSuchElementException("No value present");
+ }
+ return value;
+ }
+
+ /**
+ * Return {@code true} if there is a value present, otherwise {@code false}.
+ *
+ * @return {@code true} if there is a value present, otherwise {@code false}
+ */
+ public boolean isPresent() {
+ return isPresent;
+ }
+
+ // DIFFBLUE MODEL LIBRARY This method was added in JDK 11; the code and
+ // documentation are those of JDK 11.
+ /**
+ * If a value is not present, returns {@code true}, otherwise
+ * {@code false}.
+ *
+ * @return {@code true} if a value is not present, otherwise {@code false}
+ * @since 11
+ */
+ public boolean isEmpty() {
+ return !isPresent;
+ }
+
+ /**
+ * Have the specified consumer accept the value if a value is present,
+ * otherwise do nothing.
+ *
+ * @param consumer block to be executed if a value is present
+ * @throws NullPointerException if value is present and {@code consumer} is
+ * null
+ */
+ public void ifPresent(IntConsumer consumer) {
+ if (isPresent)
+ consumer.accept(value);
+ }
+
+ /**
+ * Return the value if present, otherwise return {@code other}.
+ *
+ * @param other the value to be returned if there is no value present
+ * @return the value, if present, otherwise {@code other}
+ */
+ public int orElse(int other) {
+ return isPresent ? value : other;
+ }
+
+ /**
+ * Return the value if present, otherwise invoke {@code other} and return
+ * the result of that invocation.
+ *
+ * @param other a {@code IntSupplier} whose result is returned if no value
+ * is present
+ * @return the value if present otherwise the result of {@code other.getAsInt()}
+ * @throws NullPointerException if value is not present and {@code other} is
+ * null
+ */
+ public int orElseGet(IntSupplier other) {
+ return isPresent ? value : other.getAsInt();
+ }
+
+ /**
+ * Return the contained value, if present, otherwise throw an exception
+ * to be created by the provided supplier.
+ *
+ * @apiNote A method reference to the exception constructor with an empty
+ * argument list can be used as the supplier. For example,
+ * {@code IllegalStateException::new}
+ *
+ * @param
+ *
+ *
+ * @param obj an object to be tested for equality
+ * @return {code true} if the other object is "equal to" this object
+ * otherwise {@code false}
+ */
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj) {
+ return true;
+ }
+
+ if (!(obj instanceof OptionalInt)) {
+ return false;
+ }
+
+ OptionalInt other = (OptionalInt) obj;
+ return (isPresent && other.isPresent)
+ ? value == other.value
+ : isPresent == other.isPresent;
+ }
+
+ /**
+ * Returns the hash code value of the present value, if any, or 0 (zero) if
+ * no value is present.
+ *
+ * @return hash code value of the present value or 0 if no value is present
+ */
+ @Override
+ public int hashCode() {
+ return isPresent ? Integer.hashCode(value) : 0;
+ }
+
+ /**
+ * {@inheritDoc}
+ *
+ * Returns a non-empty string representation of this object suitable for
+ * debugging. The exact presentation format is unspecified and may vary
+ * between implementations and versions.
+ *
+ * @implSpec If a value is present the result must include its string
+ * representation in the result. Empty and present instances must be
+ * unambiguously differentiable.
+ *
+ * @return the string representation of this instance
+ */
+ @Override
+ public String toString() {
+ return isPresent
+ ? String.format("OptionalInt[%s]", value)
+ : "OptionalInt.empty";
+ }
+}