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

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.

Methods declared in class java.lang.Object

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

Methods

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 extends Throwable

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

hashCode

public int hashCode()

Returns the hash code of the value, if present, otherwise 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
See Also:
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

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

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https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/OptionalDouble.html