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>	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.
boolean	isPresent() Checks value present.
<U> Optional<U>	map(Function<? super T,? extends U> 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.
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.
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

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

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

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