diff -r 816b9df68a9f -r 53619efef3fb jdk/src/share/classes/java/util/OptionalDouble.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/jdk/src/share/classes/java/util/OptionalDouble.java Tue Mar 19 16:05:34 2013 -0700 @@ -0,0 +1,245 @@ +/* + * Copyright (c) 2012, 2013, 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; + +/** + * 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 get()} will return the value. + * + *

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()} (execute a block + * of code if the value is present). + * + * @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; + } + + /** + * 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(DoubleConsumer 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 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 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 double orElseThrow(Supplier exceptionSupplier) throws X { + if (isPresent) { + return value; + } else { + throw exceptionSupplier.get(); + } + } + + /** + * Indicates whether some other object is "equal to" this Optional. The + * other object is considered equal if: + *

+ * + * @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; + } + + /** + * Returns a non-empty string representation of this OptionalDouble 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 OptionalDoubless must be + * unambiguously differentiable. + * + * @return the string representation of this instance + */ + @Override + public String toString() { + return isPresent + ? String.format("OptionalDouble[%s]", value) + : "OptionalDouble.empty"; + } +}