Module java.base
Package java.util

Class OptionalDouble

  • public final class OptionalDouble
extends Object
    A container object which may or may not contain a double value. If a value is present, isPresent() returns true. If no value is present, the object is considered empty and isPresent() returns false.

    Additional methods that depend on the presence or absence of a contained value are provided, such as orElse() (returns a default value if no value is present) and ifPresent() (performs an action if a value is present).

    This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of OptionalDouble may have unpredictable results and should be avoided.

    API Note:
    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 OptionalDouble should never itself be null; it should always point to an OptionalDouble instance.
    Since:
    1.8

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static OptionalDouble empty()
      Returns an empty OptionalDouble instance.
      boolean equals​(Object obj)
      Indicates whether some other object is "equal to" this OptionalDouble.
      double getAsDouble()
      If a value is present, returns the value, otherwise throws NoSuchElementException.
      int hashCode()
      Returns the hash code of the value, if present, otherwise 0 (zero) if no value is present.
      void ifPresent​(DoubleConsumer action)
      If a value is present, performs the given action with the value, otherwise does nothing.
      void ifPresentOrElse​(DoubleConsumer action, Runnable emptyAction)
      If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
      boolean isEmpty()
      If a value is not present, returns true, otherwise false.
      boolean isPresent()
      If a value is present, returns true, otherwise false.
      static OptionalDouble of​(double value)
      Returns an OptionalDouble describing the given value.
      double orElse​(double other)
      If a value is present, returns the value, otherwise returns other.
      double orElseGet​(DoubleSupplier supplier)
      If a value is present, returns the value, otherwise returns the result produced by the supplying function.
      double orElseThrow()
      If a value is present, returns the value, otherwise throws NoSuchElementException.
      <X extends Throwable>
      double      		 orElseThrow​(Supplier<? extends X> exceptionSupplier)
      If a value is present, returns the value, otherwise throws an exception produced by the exception supplying function.
      DoubleStream stream()
      If a value is present, returns a sequential DoubleStream containing only that value, otherwise returns an empty DoubleStream.
      String toString()
      Returns a non-empty string representation of this OptionalDouble suitable for debugging.

    • Method Detail

      • empty

        public static OptionalDouble empty()
        Returns an empty OptionalDouble instance. No value is present for this OptionalDouble.
        API Note:
        Though it may be tempting to do so, avoid testing if an object is empty by comparing with == against instances returned by OptionalDouble.empty(). There is no guarantee that it is a singleton. Instead, use isPresent().
        Returns:
        an empty OptionalDouble.

      • of

        public static OptionalDouble of​(double value)
        Returns an OptionalDouble describing the given value.
        Parameters:
        value - the value to describe
        Returns:
        an OptionalDouble with the value present

      • getAsDouble

        public double getAsDouble()
        If a value is present, returns the value, otherwise throws NoSuchElementException.
        API Note:
        The preferred alternative to this method is orElseThrow().
        Returns:
        the value described by this OptionalDouble
        Throws:
        NoSuchElementException - if no value is present

      • isPresent

        public boolean isPresent()
        If a value is present, returns true, otherwise false.
        Returns:
        true if a value is present, otherwise false

      • isEmpty

        public boolean isEmpty()
        If a value is not present, returns true, otherwise false.
        Returns:
        true if a value is not present, otherwise false
        Since:
        11

      • ifPresent

        public void ifPresent​(DoubleConsumer action)
        If a value is present, performs the given action with the value, otherwise does nothing.
        Parameters:
        action - the action to be performed, if a value is present
        Throws:
        NullPointerException - if value is present and the given action is null

      • ifPresentOrElse

        public void ifPresentOrElse​(DoubleConsumer action,
                            Runnable emptyAction)
        If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
        Parameters:
        action - the action to be performed, if a value is present
        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 null, or no value is present and the given empty-based action is null.
        Since:
        9

      • stream

        public DoubleStream stream()
        If a value is present, returns a sequential DoubleStream containing only that value, otherwise returns an empty DoubleStream.
        API Note:
        This method can be used to transform a Stream of optional doubles to a DoubleStream of present doubles: 
        
     Stream<OptionalDouble> os = ..
     DoubleStream s = os.flatMapToDouble(OptionalDouble::stream)
        Returns:
        the optional value as a DoubleStream
        Since:
        9

      • orElse

        public double orElse​(double other)
        If a value is present, returns the value, otherwise returns other.
        Parameters:
        other - the value to be returned, if no value is present
        Returns:
        the value, if present, otherwise other

      • orElseGet

        public double orElseGet​(DoubleSupplier supplier)
        If a value is present, returns the value, otherwise returns the result produced by the supplying function.
        Parameters:
        supplier - the supplying function that produces a value to be returned
        Returns:
        the value, if present, otherwise the result produced by the supplying function
        Throws:
        NullPointerException - if no value is present and the supplying function is null

      • orElseThrow

        public double orElseThrow()
        If a value is present, returns the value, otherwise throws NoSuchElementException.
        Returns:
        the value described by this OptionalDouble
        Throws:
        NoSuchElementException - if no value is present
        Since:
        10

      • orElseThrow

        public <X extends Throwable> double orElseThrow​(Supplier<? extends X> exceptionSupplier)
                                         throws X
        If a value is present, returns the value, otherwise throws an exception produced by the exception supplying function.
        API Note:
        A method reference to the exception constructor with an empty argument list can be used as the supplier. For example, IllegalStateException::new
        Type Parameters:
        X - Type of the exception to be thrown
        Parameters:
        exceptionSupplier - the supplying function that produces an exception to be thrown
        Returns:
        the value, if present
        Throws:
        X - if no value is present
        NullPointerException - if no value is present and the exception supplying function is null
        X extends Throwable

      • equals

        public boolean equals​(Object obj)
        Indicates whether some other object is "equal to" this OptionalDouble. The other object is considered equal if:
        • it is also an OptionalDouble and;
        • both instances have no value present or;
        • the present values are "equal to" each other via Double.compare() == 0.
        Overrides:
        equals in class Object
        Parameters:
        obj - an object to be tested for equality
        Returns:
        true if the other object is "equal to" this object otherwise false
        See Also:
        Object.hashCode(), HashMap

      • toString

        public String toString()
        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.
        Overrides:
        toString in class Object
        Implementation Requirements:
        If a value is present the result must include its string representation in the result. Empty and present OptionalDoubles must be unambiguously differentiable.
        Returns:
        the string representation of this instance