jdk/src/java.base/share/classes/java/util/OptionalDouble.java - platform/libcore - Git at Google

 /*
  * Copyright (c) 2012, 2017, 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()} returns {@code true} and
  * {@code getAsDouble()} returns the value.
  *
  * <p>Additional methods that depend on the presence or absence of a contained
  * value are provided, such as {@link #orElse(double) orElse()}
  * (returns a default value if no value is present) and
  * {@link #ifPresent(DoubleConsumer) ifPresent()} (performs
  * an action if a 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.
  *
  * @apiNote
  * {@code OptionalDouble} is primarily intended for use as a method return type where
  * there is a clear need to represent "no result." A variable whose type is
  * {@code OptionalDouble} should never itself be {@code null}; it should always point
  * to an {@code OptionalDouble} instance.
  *
  * @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 {@code 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 OptionalDouble.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 described value.
      *
      * @param value the double value to describe.
      */
     private OptionalDouble(double value) {
         this.isPresent = true;
         this.value = value;
     }

     /**
      * Returns an {@code OptionalDouble} describing the given value.
      *
      * @param value the value to describe
      * @return an {@code OptionalDouble} with the value present
      */
     public static OptionalDouble of(double value) {
         return new OptionalDouble(value);
     }

     /**
      * If a value is present, returns the value, otherwise throws
      * {@code NoSuchElementException}.
      *
      * @apiNote
      * The methods {@link #orElse(double) orElse} and
      * {@link #orElseGet(DoubleSupplier) orElseGet}
      * are generally preferable to this method, as they return a substitute
      * value if the value is absent, instead of throwing an exception.
      *
      * @return the value described by this {@code OptionalDouble}
      * @throws NoSuchElementException if no value is present
      * @see OptionalDouble#isPresent()
      */
     public double getAsDouble() {
         if (!isPresent) {
             throw new NoSuchElementException("No value present");
         }
         return value;
     }

     /**
      * If a value is present, returns {@code true}, otherwise {@code false}.
      *
      * @return {@code true} if a value is present, otherwise {@code false}
      */
     public boolean isPresent() {
         return isPresent;
     }

     /**
      * If a value is present, performs the given action with the value,
      * otherwise does nothing.
      *
      * @param action the action to be performed, if a value is present
      * @throws NullPointerException if value is present and the given action is
      *         {@code null}
      */
     public void ifPresent(DoubleConsumer action) {
         if (isPresent) {
             action.accept(value);
         }
     }

     /**
      * If a value is present, performs the given action with the value,
      * otherwise performs 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 no value is
      * present
      * @throws NullPointerException if a value is present and the given action
      *         is {@code null}, or no value is present and the given empty-based
      *         action is {@code null}.
      * @since 9
      */
     public void ifPresentOrElse(DoubleConsumer action, Runnable emptyAction) {
         if (isPresent) {
             action.accept(value);
         } else {
             emptyAction.run();
         }
     }

     /**
      * If a value is present, returns a sequential {@link DoubleStream}
      * containing only that value, otherwise returns 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 9
      */
     public DoubleStream stream() {
         if (isPresent) {
             return DoubleStream.of(value);
         } else {
             return DoubleStream.empty();
         }
     }

     /**
      * If a value is present, returns the value, otherwise returns
      * {@code other}.
      *
      * @param other the value to be returned, if no value is present
      * @return the value, if present, otherwise {@code other}
      */
     public double orElse(double other) {
         return isPresent ? value : other;
     }

     /**
      * If a value is present, returns the value, otherwise returns the result
      * produced by the supplying function.
      *
      * @param supplier the supplying function that produces a value to be returned
      * @return the value, if present, otherwise the result produced by the
      *         supplying function
      * @throws NullPointerException if no value is present and the supplying
      *         function is {@code null}
      */
     public double orElseGet(DoubleSupplier supplier) {
         return isPresent ? value : supplier.getAsDouble();
     }

     /**
      * If a value is present, returns the value, otherwise throws an exception
      * produced by the exception supplying function.
      *
      * @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 supplying function that produces an
      *        exception to be thrown
      * @return the value, if present
      * @throws X if no value is present
      * @throws NullPointerException if no value is present and the exception
      *         supplying function is {@code 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
      * {@code 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 of the value, if present, otherwise {@code 0}
      * (zero) if no value is present.
      *
      * @return hash code value of the present value or {@code 0} if no value is
      *         present
      */
     @Override
     public int hashCode() {
         return isPresent ? Double.hashCode(value) : 0;
     }

     /**
      * Returns a non-empty string representation of this {@code 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 {@code OptionalDouble}s must be
      * unambiguously differentiable.
      *
      * @return the string representation of this instance
      */
     @Override
     public String toString() {
         return isPresent
                 ? String.format("OptionalDouble[%s]", value)
                 : "OptionalDouble.empty";
     }
 }
	/*
	* Copyright (c) 2012, 2017, 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()} returns {@code true} and
	* {@code getAsDouble()} returns the value.
	*
	* <p>Additional methods that depend on the presence or absence of a contained
	* value are provided, such as {@link #orElse(double) orElse()}
	* (returns a default value if no value is present) and
	* {@link #ifPresent(DoubleConsumer) ifPresent()} (performs
	* an action if a 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.
	*
	* @apiNote
	* {@code OptionalDouble} is primarily intended for use as a method return type where
	* there is a clear need to represent "no result." A variable whose type is
	* {@code OptionalDouble} should never itself be {@code null}; it should always point
	* to an {@code OptionalDouble} instance.
	*
	* @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 {@code 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 OptionalDouble.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 described value.
	*
	* @param value the double value to describe.
	*/
	private OptionalDouble(double value) {
	this.isPresent = true;
	this.value = value;
	}

	/**
	* Returns an {@code OptionalDouble} describing the given value.
	*
	* @param value the value to describe
	* @return an {@code OptionalDouble} with the value present
	*/
	public static OptionalDouble of(double value) {
	return new OptionalDouble(value);
	}

	/**
	* If a value is present, returns the value, otherwise throws
	* {@code NoSuchElementException}.
	*
	* @apiNote
	* The methods {@link #orElse(double) orElse} and
	* {@link #orElseGet(DoubleSupplier) orElseGet}
	* are generally preferable to this method, as they return a substitute
	* value if the value is absent, instead of throwing an exception.
	*
	* @return the value described by this {@code OptionalDouble}
	* @throws NoSuchElementException if no value is present
	* @see OptionalDouble#isPresent()
	*/
	public double getAsDouble() {
	if (!isPresent) {
	throw new NoSuchElementException("No value present");
	}
	return value;
	}

	/**
	* If a value is present, returns {@code true}, otherwise {@code false}.
	*
	* @return {@code true} if a value is present, otherwise {@code false}
	*/
	public boolean isPresent() {
	return isPresent;
	}

	/**
	* If a value is present, performs the given action with the value,
	* otherwise does nothing.
	*
	* @param action the action to be performed, if a value is present
	* @throws NullPointerException if value is present and the given action is
	* {@code null}
	*/
	public void ifPresent(DoubleConsumer action) {
	if (isPresent) {
	action.accept(value);
	}
	}

	/**
	* If a value is present, performs the given action with the value,
	* otherwise performs 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 no value is
	* present
	* @throws NullPointerException if a value is present and the given action
	* is {@code null}, or no value is present and the given empty-based
	* action is {@code null}.
	* @since 9
	*/
	public void ifPresentOrElse(DoubleConsumer action, Runnable emptyAction) {
	if (isPresent) {
	action.accept(value);
	} else {
	emptyAction.run();
	}
	}

	/**
	* If a value is present, returns a sequential {@link DoubleStream}
	* containing only that value, otherwise returns 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 9
	*/
	public DoubleStream stream() {
	if (isPresent) {
	return DoubleStream.of(value);
	} else {
	return DoubleStream.empty();
	}
	}

	/**
	* If a value is present, returns the value, otherwise returns
	* {@code other}.
	*
	* @param other the value to be returned, if no value is present
	* @return the value, if present, otherwise {@code other}
	*/
	public double orElse(double other) {
	return isPresent ? value : other;
	}

	/**
	* If a value is present, returns the value, otherwise returns the result
	* produced by the supplying function.
	*
	* @param supplier the supplying function that produces a value to be returned
	* @return the value, if present, otherwise the result produced by the
	* supplying function
	* @throws NullPointerException if no value is present and the supplying
	* function is {@code null}
	*/
	public double orElseGet(DoubleSupplier supplier) {
	return isPresent ? value : supplier.getAsDouble();
	}

	/**
	* If a value is present, returns the value, otherwise throws an exception
	* produced by the exception supplying function.
	*
	* @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 supplying function that produces an
	* exception to be thrown
	* @return the value, if present
	* @throws X if no value is present
	* @throws NullPointerException if no value is present and the exception
	* supplying function is {@code 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
	* {@code 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 of the value, if present, otherwise {@code 0}
	* (zero) if no value is present.
	*
	* @return hash code value of the present value or {@code 0} if no value is
	* present
	*/
	@Override
	public int hashCode() {
	return isPresent ? Double.hashCode(value) : 0;
	}

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