Class OptionalLong

java.lang.Object
- java.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. 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 OptionalLong may have unpredictable results and should be avoided.

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

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	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`	`isEmpty()`	If a value is not present, returns `true`, otherwise `false`.
`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.
`long`	`orElseThrow()`	If a value is present, returns the value, otherwise throws `NoSuchElementException`.
`<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 declared in 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.

API Note:: The preferred alternative to this method is orElseThrow().
Returns:: the value described by this OptionalLong
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(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 an LongStream of present longs:

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

Returns:

the optional value as an 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 long orElseThrow()

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
Since:: 10

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
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 OptionalLong 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 OptionalLongs must be unambiguously differentiable.
Returns:: the string representation of this instance