Module java.base
Package java.util

# Class OptionalDouble

java.lang.Object
java.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()` 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; programmers should treat instances that are equal as interchangeable and should not use instances for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail.

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

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`

## Method Details

### 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 `==` or `!=` against instances returned by `OptionalDouble.empty()`. There is no guarantee that it is a singleton. Instead, use `isEmpty()` or `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`

### 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 `OptionalDouble`s must be unambiguously differentiable.
Returns:
  the string representation of this instance