| /* |
| * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| package java.util; |
| |
| import java.util.function.DoubleConsumer; |
| import java.util.function.DoubleSupplier; |
| import java.util.function.Supplier; |
| import java.util.stream.DoubleStream; |
| |
| /** |
| * A container object which may or may not contain a {@code double} value. |
| * If a value is present, {@code isPresent()} will return {@code true} and |
| * {@code getAsDouble()} will return the value. |
| * |
| * <p>Additional methods that depend on the presence or absence of a contained |
| * value are provided, such as {@link #orElse(double) orElse()} |
| * (return a default value if value not present) and |
| * {@link #ifPresent(java.util.function.DoubleConsumer) ifPresent()} (perform an |
| * action if the value is present). |
| * |
| * <p>This is a <a href="../lang/doc-files/ValueBased.html">value-based</a> |
| * class; use of identity-sensitive operations (including reference equality |
| * ({@code ==}), identity hash code, or synchronization) on instances of |
| * {@code OptionalDouble} may have unpredictable results and should be avoided. |
| * |
| * @since 1.8 |
| */ |
| public final class OptionalDouble { |
| /** |
| * Common instance for {@code empty()}. |
| */ |
| private static final OptionalDouble EMPTY = new OptionalDouble(); |
| |
| /** |
| * If true then the value is present, otherwise indicates no value is present |
| */ |
| private final boolean isPresent; |
| private final double value; |
| |
| /** |
| * Construct an empty instance. |
| * |
| * @implNote generally only one empty instance, {@link OptionalDouble#EMPTY}, |
| * should exist per VM. |
| */ |
| private OptionalDouble() { |
| this.isPresent = false; |
| this.value = Double.NaN; |
| } |
| |
| /** |
| * Returns an empty {@code OptionalDouble} instance. No value is present for this |
| * OptionalDouble. |
| * |
| * @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 OptionalDouble}. |
| */ |
| public static OptionalDouble empty() { |
| return EMPTY; |
| } |
| |
| /** |
| * Construct an instance with the value present. |
| * |
| * @param value the double value to be present. |
| */ |
| private OptionalDouble(double value) { |
| this.isPresent = true; |
| this.value = value; |
| } |
| |
| /** |
| * Return an {@code OptionalDouble} with the specified value present. |
| * |
| * @param value the value to be present |
| * @return an {@code OptionalDouble} with the value present |
| */ |
| public static OptionalDouble of(double value) { |
| return new OptionalDouble(value); |
| } |
| |
| /** |
| * If a value is present in this {@code OptionalDouble}, returns the value, |
| * otherwise throws {@code NoSuchElementException}. |
| * |
| * @return the value held by this {@code OptionalDouble} |
| * @throws NoSuchElementException if there is no value present |
| * |
| * @see OptionalDouble#isPresent() |
| */ |
| public double getAsDouble() { |
| 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; |
| } |
| |
| /** |
| * If a value is present, perform the given action with the value, |
| * otherwise do nothing. |
| * |
| * @param action the action to be performed if a value is present |
| * @throws NullPointerException if a value is present and {@code action} is |
| * null |
| */ |
| public void ifPresent(DoubleConsumer action) { |
| if (isPresent) { |
| action.accept(value); |
| } |
| } |
| |
| /** |
| * If a value is present, perform the given action with the value, |
| * otherwise perform the given empty-based action. |
| * |
| * @param action the action to be performed if a value is present |
| * @param emptyAction the empty-based action to be performed if a value is |
| * not present |
| * @throws NullPointerException if a value is present and {@code action} is |
| * null, or a value is not present and {@code emptyAction} is null. |
| * @since 1.9 |
| */ |
| public void ifPresentOrElse(DoubleConsumer action, Runnable emptyAction) { |
| if (isPresent) { |
| action.accept(value); |
| } else { |
| emptyAction.run(); |
| } |
| } |
| |
| /** |
| * If a value is present return a sequential {@link DoubleStream} containing |
| * only that value, otherwise return an empty {@code DoubleStream}. |
| * |
| * @apiNote This method can be used to transform a {@code Stream} of |
| * optional doubles to a {@code DoubleStream} of present doubles: |
| * |
| * <pre>{@code |
| * Stream<OptionalDouble> os = .. |
| * DoubleStream s = os.flatMapToDouble(OptionalDouble::stream) |
| * }</pre> |
| * |
| * @return the optional value as a {@code DoubleStream} |
| * @since 1.9 |
| */ |
| public DoubleStream stream() { |
| if (isPresent) { |
| return DoubleStream.of(value); |
| } else { |
| return DoubleStream.empty(); |
| } |
| } |
| |
| /** |
| * 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 double orElse(double 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 DoubleSupplier} whose result is returned if no value |
| * is present |
| * @return the value if present otherwise the result of {@code other.getAsDouble()} |
| * @throws NullPointerException if value is not present and {@code other} is |
| * null |
| */ |
| public double orElseGet(DoubleSupplier other) { |
| return isPresent ? value : other.getAsDouble(); |
| } |
| |
| /** |
| * 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 <X> Type of the exception to be thrown |
| * @param exceptionSupplier The supplier which will return the exception to |
| * be thrown |
| * @return the present value |
| * @throws X if there is no value present |
| * @throws NullPointerException if no value is present and |
| * {@code exceptionSupplier} is null |
| */ |
| public<X extends Throwable> double orElseThrow(Supplier<? extends X> exceptionSupplier) throws X { |
| if (isPresent) { |
| return value; |
| } else { |
| throw exceptionSupplier.get(); |
| } |
| } |
| |
| /** |
| * Indicates whether some other object is "equal to" this OptionalDouble. The |
| * other object is considered equal if: |
| * <ul> |
| * <li>it is also an {@code OptionalDouble} and; |
| * <li>both instances have no value present or; |
| * <li>the present values are "equal to" each other via {@code Double.compare() == 0}. |
| * </ul> |
| * |
| * @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 OptionalDouble)) { |
| return false; |
| } |
| |
| OptionalDouble other = (OptionalDouble) obj; |
| return (isPresent && other.isPresent) |
| ? Double.compare(value, other.value) == 0 |
| : 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 ? Double.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("OptionalDouble[%s]", value) |
| : "OptionalDouble.empty"; |
| } |
| } |