no.finntech.lambdacompanion

Class StreamableOptional<T>

java.lang.Object

no.finntech.lambdacompanion.StreamableOptional<T>

public class StreamableOptional<T>
extends Object

Wrapper around an usual Optional that provides the very missed stream() method useful for flatMapping a Stream of Optional (i.e. only keep present values).

example: the good

 
 collection.stream().flatMap(item -> StreamableOptional.ofNullable(item.getNullableProperty()).stream())
 
 

would replace the bad:

 
 collection.stream().map(item -> Optional.ofNullable(item.getNullableProperty())).filter(Optional::isPresent).map(Optional::get)
 
 

or the ugly:

 
 collection.stream().flatMap(item -> Optional.ofNullable(item.getNullableProperty()).map(Stream::of).orElseGet(Stream::empty))
 
 

Method Summary

Modifier and Type	Method and Description
static <T> StreamableOptional<T>	empty()
boolean	equals(Object o)
StreamableOptional<T>	filter(Predicate<? super T> predicate)
<U> StreamableOptional<U>	flatMap(Function<? super T,StreamableOptional<U>> mapper)
int	hashCode()
void	ifPresent(Consumer<? super T> consumer)
<U> StreamableOptional<U>	map(Function<? super T,? extends U> mapper)
static <T> StreamableOptional<T>	of(T value)
static <T> StreamableOptional<T>	ofNullable(T value)
static <T> StreamableOptional<T>	ofOptional(Optional<T> optional) Builds a StreamableOptional around the given Optional
T	orElse(T other)
T	orElseGet(Supplier<? extends T> other)
<X extends Throwable> T	orElseThrow(Supplier<? extends X> exceptionSupplier)
Stream<T>	stream() Turns this optional into a Stream
Optional<T>	toOptional()

Methods inherited from class java.lang.Object

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

Method Detail

ifPresent

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

Parameters:

consumer - consumer

See Also:

Optional.ifPresent(java.util.function.Consumer)

filter

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

Parameters:

predicate - predicate

Returns:

StreamableOptional

See Also:

Optional.filter(java.util.function.Predicate)

map

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

Type Parameters:

U - u

Parameters:

mapper - mapper

Returns:

U

See Also:

Optional.map(java.util.function.Function)

flatMap

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

Type Parameters:

U - u

Parameters:

mapper - mapper

Returns:

U

See Also:

Optional.flatMap(java.util.function.Function)

orElse

public T orElse(T other)

Parameters:

other - other

Returns:

T t

See Also:

Optional.orElse(Object)

orElseGet

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

Parameters:

other - other

Returns:

T t

See Also:

Optional.orElseGet(java.util.function.Supplier)

orElseThrow

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

Type Parameters:

X - x

Parameters:

exceptionSupplier - exceptionSupplier

Returns:

T t

Throws:

X - x

X extends Throwable

See Also:

Optional.orElseThrow(java.util.function.Supplier)

stream

public Stream<T> stream()

Turns this optional into a Stream

Returns:

a Stream of the one value contained within this optional if it is present, an empty stream else

toOptional

public Optional<T> toOptional()

Returns:

the Optional within

of

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

Type Parameters:

T - t

Parameters:

value - value

Returns:

T t

See Also:

Optional.of(Object)

ofNullable

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

Type Parameters:

T - t

Parameters:

value - value

Returns:

T t

See Also:

Optional.ofNullable(Object)

ofOptional

public static <T> StreamableOptional<T> ofOptional(Optional<T> optional)

Builds a StreamableOptional around the given Optional

Type Parameters:

T - t

Parameters:

optional - a regular Optional

Returns:

a StreamableOptional

empty

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

Type Parameters:

T - t

Returns:

T t

See Also:

Optional.empty()

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object