java8.util

Class OptionalDouble

java.lang.Object

java8.util.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() will return true and getAsDouble() will return the value.

Additional methods that depend on the presence or absence of a contained value are provided, such as orElse() (return a default value if value not present) and ifPresent() (perform an action if the 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.

Since:

1.8

Method Summary

Modifier and Type	Method and 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 in this OptionalDouble, returns the value, otherwise throws NoSuchElementException.
int	hashCode() Returns the hash code value of the present value, if any, or 0 (zero) if no value is present.
void	ifPresent(DoubleConsumer action) If a value is present, perform the given action with the value, otherwise do nothing.
void	ifPresentOrElse(DoubleConsumer action, Runnable emptyAction) If a value is present, perform the given action with the value, otherwise perform the given empty-based action.
boolean	isPresent() Return true if there is a value present, otherwise false.
static OptionalDouble	of(double value) Return an OptionalDouble with the specified value present.
double	orElse(double other) Return the value if present, otherwise return other.
double	orElseGet(DoubleSupplier other) Return the value if present, otherwise invoke other and return the result of that invocation.
<X extends Throwable> double	orElseThrow(Supplier<? extends X> exceptionSupplier) Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.
DoubleStream	stream() If a value is present return a sequential DoubleStream containing only that value, otherwise return an empty DoubleStream.
String	toString() Returns a non-empty string representation of this object suitable for debugging.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

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 Option.empty(). There is no guarantee that it is a singleton. Instead, use isPresent().

Returns:

an empty OptionalDouble.

of

public static OptionalDouble of(double value)

Return an OptionalDouble with the specified value present.

Parameters:

value - the value to be present

Returns:

an OptionalDouble with the value present

getAsDouble

public double getAsDouble()

If a value is present in this OptionalDouble, returns the value, otherwise throws NoSuchElementException.

Returns:

the value held by this OptionalDouble

Throws:

NoSuchElementException - if there is no value present

See Also:

isPresent()

isPresent

public boolean isPresent()

Return true if there is a value present, otherwise false.

Returns:

true if there is a value present, otherwise false

ifPresent

public void ifPresent(DoubleConsumer action)

If a value is present, perform the given action with the value, otherwise do nothing.

Parameters:

action - the action to be performed if a value is present

Throws:

NullPointerException - if a value is present and action is null

ifPresentOrElse

public void ifPresentOrElse(DoubleConsumer action,
                            Runnable emptyAction)

If a value is present, perform the given action with the value, otherwise perform 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 a value is not present

Throws:

NullPointerException - if a value is present and action is null, or a value is not present and emptyAction is null.

Since:

1.9

stream

public DoubleStream stream()

If a value is present return a sequential DoubleStream containing only that value, otherwise return 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:

1.9

orElse

public double orElse(double other)

Return the value if present, otherwise return other.

Parameters:

other - the value to be returned if there is no value present

Returns:

the value, if present, otherwise other

orElseGet

public double orElseGet(DoubleSupplier other)

Return the value if present, otherwise invoke other and return the result of that invocation.

Parameters:

other - a DoubleSupplier whose result is returned if no value is present

Returns:

the value if present otherwise the result of other.getAsDouble()

Throws:

NullPointerException - if value is not present and other is null

orElseThrow

public <X extends Throwable> double orElseThrow(Supplier<? extends X> exceptionSupplier)
                                         throws X extends Throwable

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.

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 supplier which will return the exception to be thrown

Returns:

the present value

Throws:

X - if there is no value present

NullPointerException - if no value is present and exceptionSupplier 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

hashCode

public int hashCode()

Returns the hash code value of the present value, if any, or 0 (zero) if no value is present.

Overrides:

hashCode in class Object

Returns:

hash code value of the present value or 0 if no value is present

toString

public String toString()

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.

Implementation Requirements:
If a value is present the result must include its string representation in the result. Empty and present instances must be unambiguously differentiable.

Overrides:

toString in class Object

Returns:

the string representation of this instance