com.annimon.stream

Class Optional<T>

java.lang.Object

com.annimon.stream.Optional<T>

Type Parameters:

T - the type of the inner value

public class Optional<T>
extends Object

A container object which may or may not contain a non-null value.

Method Summary

Modifier and Type	Method and Description
static <T> Optional<T>	empty() Returns an empty Optional.
boolean	equals(Object obj)
Optional<T>	executeIfAbsent(Runnable action) Invokes action function if value is absent.
Optional<T>	executeIfPresent(Consumer<? super T> consumer) Invokes consumer function with value if present.
Optional<T>	filter(Predicate<? super T> predicate) Performs filtering on inner value if present.
<U> Optional<U>	flatMap(Function<? super T,Optional<U>> mapper) Invokes mapping function with Optional result if value is present.
T	get() Returns inner value if present, otherwise throws NoSuchElementException.
int	hashCode()
void	ifPresent(Consumer<? super T> consumer) Invokes consumer function with value if present.
void	ifPresentOrElse(Consumer<? super T> consumer, Runnable emptyAction) If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
boolean	isPresent() Checks value present.
<U> Optional<U>	map(Function<? super T,? extends U> mapper) Invokes mapping function on inner value if present.
OptionalInt	mapToInt(ToIntFunction<? super T> mapper) Invokes mapping function on inner value if present.
static <T> Optional<T>	of(T value) Returns an Optional with the specified present non-null value.
static <T> Optional<T>	ofNullable(T value) Returns an Optional with the specified value, or empty Optional if value is null.
Optional<T>	or(Supplier<Optional<T>> supplier) Returns current Optional if value is present, otherwise returns an Optional produced by supplier function.
T	orElse(T other) Returns inner value if present, otherwise returns other.
T	orElseGet(Supplier<? extends T> other) Returns inner value if present, otherwise returns value produced by supplier function.
<X extends Throwable> T	orElseThrow(Supplier<? extends X> exc) Returns inner value if present, otherwise throws the exception provided by supplier function.
<R> Optional<R>	select(Class<R> clazz) Keeps inner value only if is present and instance of given class.
Stream<T>	stream() Wraps a value into Stream if present, otherwise returns an empty Stream.
String	toString()

Methods inherited from class java.lang.Object

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

Method Detail

of

public static <T> Optional<T> of(T value)

Returns an Optional with the specified present non-null value.

Type Parameters:

T - the type of value

Parameters:

value - the value to be present, must be non-null

Returns:

an Optional

Throws:

NullPointerException - if value is null

See Also:

ofNullable(java.lang.Object)

ofNullable

public static <T> Optional<T> ofNullable(T value)

Returns an Optional with the specified value, or empty Optional if value is null.

Type Parameters:

T - the type of value

Parameters:

value - the value which can be null

Returns:

an Optional

See Also:

of(java.lang.Object)

empty

public static <T> Optional<T> empty()

Returns an empty Optional.

Type Parameters:

T - the type of value

Returns:

an Optional

get

public T get()

Returns inner value if present, otherwise throws NoSuchElementException.

Returns:

inner value of Optional

Throws:

NoSuchElementException - if value is not present

isPresent

public boolean isPresent()

Checks value present.

Returns:

true if value present, false otherwise

ifPresent

public void ifPresent(Consumer<? super T> consumer)

Invokes consumer function with value if present.

Parameters:

consumer - consumer function

ifPresentOrElse

public void ifPresentOrElse(Consumer<? super T> consumer,
                            Runnable emptyAction)

If a value is present, performs the given action with the value, otherwise performs the given empty-based action.

Parameters:

consumer - the consumer function to be executed, 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 consumer function is null, or no value is present and the given empty-based action is null.

executeIfPresent

public Optional<T> executeIfPresent(Consumer<? super T> consumer)

Invokes consumer function with value if present. This method same as ifPresent, but does not break chaining

Parameters:

consumer - consumer function

Returns:

this Optional

Since:

1.1.2

See Also:

ifPresent(com.annimon.stream.function.Consumer)

executeIfAbsent

public Optional<T> executeIfAbsent(Runnable action)

Invokes action function if value is absent.

Parameters:

action - action that invokes if value absent

Returns:

this Optional

Since:

1.1.2

filter

public Optional<T> filter(Predicate<? super T> predicate)

Performs filtering on inner value if present.

Parameters:

predicate - a predicate function

Returns:

an Optional with value if present and matches predicate, otherwise an empty Optional

map

public <U> Optional<U> map(Function<? super T,? extends U> mapper)

Invokes mapping function on inner value if present.

Type Parameters:

U - the type of result value

Parameters:

mapper - mapping function

Returns:

an Optional with transformed value if present, otherwise an empty Optional

mapToInt

public OptionalInt mapToInt(ToIntFunction<? super T> mapper)

Invokes mapping function on inner value if present.

Parameters:

mapper - mapping function

Returns:

an OptionalInt with transformed value if present, otherwise an empty OptionalInt

Since:

1.1.3

flatMap

public <U> Optional<U> flatMap(Function<? super T,Optional<U>> mapper)

Invokes mapping function with Optional result if value is present.

Type Parameters:

U - the type of result value

Parameters:

mapper - mapping function

Returns:

an Optional with transformed value if present, otherwise an empty Optional

stream

public Stream<T> stream()

Wraps a value into Stream if present, otherwise returns an empty Stream.

Returns:

the optional value as a Stream

select

public <R> Optional<R> select(Class<R> clazz)

Keeps inner value only if is present and instance of given class.

Type Parameters:

R - a type of instance to select.

Parameters:

clazz - a class which instance should be selected

Returns:

an Optional with value of type class if present, otherwise an empty Optional

or

public Optional<T> or(Supplier<Optional<T>> supplier)

Returns current Optional if value is present, otherwise returns an Optional produced by supplier function.

Parameters:

supplier - supplier function that produced an Optional to be returned

Returns:

this Optional if value is present, otherwise an Optional produced by supplier function

Throws:

NullPointerException - if value is not present and supplier or value produced by it is null

orElse

public T orElse(T other)

Returns inner value if present, otherwise returns other.

Parameters:

other - the value to be returned if inner value is not present

Returns:

inner value if present, otherwise other

orElseGet

public T orElseGet(Supplier<? extends T> other)

Returns inner value if present, otherwise returns value produced by supplier function.

Parameters:

other - supplier function that produced value if inner value is not present

Returns:

inner value if present, otherwise value produced by supplier function

orElseThrow

public <X extends Throwable> T orElseThrow(Supplier<? extends X> exc)
                                    throws X extends Throwable

Returns inner value if present, otherwise throws the exception provided by supplier function.

Type Parameters:

X - the type of exception to be thrown

Parameters:

exc - supplier function that produced exception to be thrown

Returns:

inner value if present

Throws:

X - if inner value is not present

X extends Throwable

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object