java8.util

Class OptionalLong

java.lang.Object

java8.util.OptionalLong

public final class OptionalLong
extends Object

A container object which may or may not contain a long value. If a value is present, isPresent() returns true and getAsLong() returns the value.

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 OptionalLong may have unpredictable results and should be avoided.

Since:

1.8

Method Summary

Modifier and Type	Method and Description
static OptionalLong	empty() Returns an empty OptionalLong instance.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this OptionalLong.
long	getAsLong() 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(LongConsumer action) If a value is present, performs the given action with the value, otherwise does nothing.
void	ifPresentOrElse(LongConsumer action, Runnable emptyAction) If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
boolean	isPresent() If a value is present, returns true, otherwise false.
static OptionalLong	of(long value) Returns an OptionalLong describing the given value.
long	orElse(long other) If a value is present, returns the value, otherwise returns other.
long	orElseGet(LongSupplier supplier) If a value is present, returns the value, otherwise returns the result produced by the supplying function.
<X extends Throwable> long	orElseThrow(Supplier<? extends X> exceptionSupplier) If a value is present, returns the value, otherwise throws an exception produced by the exception supplying function.
LongStream	stream() If a value is present, returns a sequential LongStream containing only that value, otherwise returns an empty LongStream.
String	toString() Returns a non-empty string representation of this OptionalLong suitable for debugging.

Methods inherited from class java.lang.Object

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

Method Detail

empty

public static OptionalLong empty()

Returns an empty OptionalLong instance. No value is present for this OptionalLong.

API Note:
Though it may be tempting to do so, avoid testing if an object is empty by comparing with == against instances returned by OptionalLong.empty(). There is no guarantee that it is a singleton. Instead, use isPresent().

Returns:

an empty OptionalLong.

of

public static OptionalLong of(long value)

Returns an OptionalLong describing the given value.

Parameters:

value - the value to describe

Returns:

an OptionalLong with the value present

getAsLong

public long getAsLong()

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

Returns:

the value described by this OptionalLong

Throws:

NoSuchElementException - if no value is present

See Also:

isPresent()

isPresent

public boolean isPresent()

If a value is present, returns true, otherwise false.

Returns:

true if a value is present, otherwise false

ifPresent

public void ifPresent(LongConsumer 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(LongConsumer 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 LongStream stream()

If a value is present, returns a sequential LongStream containing only that value, otherwise returns an empty LongStream.

API Note:
This method can be used to transform a Stream of optional longs to a LongStream of present longs:

     Stream<OptionalLong> os = ..
     LongStream s = os.flatMapToLong(OptionalLong::stream)
 

Returns:

the optional value as a LongStream

Since:

9

orElse

public long orElse(long 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 long orElseGet(LongSupplier 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 <X extends Throwable> long 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 OptionalLong. The other object is considered equal if:

• it is also an OptionalLong and;
• both instances have no value present or;
• the present values are "equal to" each other via ==.

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 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

toString

public String toString()

Returns a non-empty string representation of this OptionalLong 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 OptionalLongs must be unambiguously differentiable.

Overrides:

toString in class Object

Returns:

the string representation of this instance