fj.data
Class Option<A>

java.lang.Object
  fj.data.Option<A>

All Implemented Interfaces:

Iterable<A>

public abstract class Option<A>
extends Object
implements Iterable<A>

An optional value that may be none (no value) or some (a value). This type is a replacement for the use of null with better type checks.

Version:

2.17

• $LastChangedRevision$
• $LastChangedDate$

Method Summary

<B> Option<B>	apply(Option<F<A,B>> of) Performs function application within an optional value (applicative functor pattern).
<B> Option<B>	bind(F<A,Option<B>> f) Binds the given function across the element of this optional value with a final join.
<B,C> Option<C>	bind(Option<B> ob, F<A,F<B,C>> f) Binds the given function across the element of this optional value and the given optional value with a final join.
<B,C,D> Option<D>	bind(Option<B> ob, Option<C> oc, F<A,F<B,F<C,D>>> f) Binds the given function across the element of this optional value and the given optional value with a final join.
<B,C,D,E> Option<E>	bind(Option<B> ob, Option<C> oc, Option<D> od, F<A,F<B,F<C,F<D,E>>>> f) Binds the given function across the element of this optional value and the given optional value with a final join.
<B,C,D,E,F$> Option<F$>	bind(Option<B> ob, Option<C> oc, Option<D> od, Option<E> oe, F<A,F<B,F<C,F<D,F<E,F$>>>>> f) Binds the given function across the element of this optional value and the given optional value with a final join.
<B,C,D,E,F$,G> Option<G>	bind(Option<B> ob, Option<C> oc, Option<D> od, Option<E> oe, Option<F$> of, F<A,F<B,F<C,F<D,F<E,F<F$,G>>>>>> f) Binds the given function across the element of this optional value and the given optional value with a final join.
<B,C,D,E,F$,G,H> Option<H>	bind(Option<B> ob, Option<C> oc, Option<D> od, Option<E> oe, Option<F$> of, Option<G> og, F<A,F<B,F<C,F<D,F<E,F<F$,F<G,H>>>>>>> f) Binds the given function across the element of this optional value and the given optional value with a final join.
<B,C,D,E,F$,G,H,I> Option<I>	bind(Option<B> ob, Option<C> oc, Option<D> od, Option<E> oe, Option<F$> of, Option<G> og, Option<H> oh, F<A,F<B,F<C,F<D,F<E,F<F$,F<G,F<H,I>>>>>>>> f) Binds the given function across the element of this optional value and the given optional value with a final join.
boolean	exists(F<A,Boolean> f) Returns true is this optional value has a value and the given predicate function holds on that value, false otherwise.
Option<A>	filter(F<A,Boolean> f) Filters elements from this optional value by returning only elements which produce true when the given function is applied to them.
boolean	forall(F<A,Boolean> f) Returns true if this optional value has no value, or the predicate holds for the given predicate function, false otherwise.
void	foreach(Effect<A> f) Performs a side-effect for the value of this optional value.
Unit	foreach(F<A,Unit> f) Performs a side-effect for the value of this optional value.
static <T> Option<T>	fromNull(T t) Turns an unsafe nullable value into a safe optional value.
static F<String,Option<String>>	fromString() Returns a function that transforms a string to an optional non-empty string, or no value if the string is empty.
static Option<String>	fromString(String s) Returns an optional non-empty string, or no value if the given string is empty.
static <A> F2<F<A,Boolean>,A,Option<A>>	iif() First-class version of the iif function.
static <A> Option<A>	iif(F<A,Boolean> f, A a) Returns an optional value that has a value of the given argument, if the given predicate holds on that argument, otherwise, returns no value.
boolean	isNone() Returns false if this optional value has a value, true otherwise.
boolean	isSome() Returns true if this optional value has a value, false otherwise.
Iterator<A>	iterator() Returns an iterator for this optional value.
static <A> Option<A>	join(Option<Option<A>> o) Joins the given optional value of optional value using a bind operation.
int	length() Returns the length of this optional value; 1 is there is a value, 0 otherwise.
<B> Option<B>	map(F<A,B> f) Maps the given function across this optional value.
static <T> Option<T>	none() Constructs an optional value that has no value.
<B> B	option(B b, F<A,B> f) Performs a reduction on this optional value using the given arguments.
Option<A>	orElse(Option<A> o) Returns this optional value if there is one, otherwise, returns the argument optional value.
Option<A>	orElse(P1<Option<A>> o) Returns this optional value if there is one, otherwise, returns the argument optional value.
A	orSome(A a) Returns the value of this optional value or the given argument.
A	orSome(P1<A> a) Returns the value of this optional value or the given argument.
static <A> Option<List<A>>	sequence(List<Option<A>> a) Sequence through the option monad.
<B> Option<B>	sequence(Option<B> o) Performs a bind across the optional value, but ignores the element value in the function.
static <T> F<T,Option<T>>	some_()
abstract A	some() Returns the value from this optional value, or fails if there is no value.
static <T> Option<T>	some(T t) Constructs an optional value that has a value of the given argument.
static <A> List<A>	somes(List<Option<A>> as) Returns all the values in the given list.
Array<A>	toArray() Returns an array projection of this optional value.
Array<A>	toArray(Class<A[]> c) Returns an array projection of this optional value.
Collection<A>	toCollection() Projects an immutable collection of this optional value.
<X> Either<X,A>	toEither(P1<X> x) Returns an either projection of this optional value; the given argument in Left if no value, or the value in Right.
<X> Either<X,A>	toEither(X x) Returns an either projection of this optional value; the given argument in Left if no value, or the value in Right.
List<A>	toList() Returns a list projection of this optional value.
Stream<A>	toStream() Returns a stream projection of this optional value.

Methods inherited from class java.lang.Object

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

Method Detail

iterator

public Iterator<A> iterator()

Returns an iterator for this optional value. This method exists to permit the use in a for-each loop.

Specified by:

iterator in interface Iterable<A>

Returns:

A iterator for this optional value.

some

public abstract A some()

Returns the value from this optional value, or fails if there is no value.

Returns:

The value from this optional value, or fails if there is no value.

isSome

public boolean isSome()

Returns true if this optional value has a value, false otherwise.

Returns:

true if this optional value has a value, false otherwise.

isNone

public boolean isNone()

Returns false if this optional value has a value, true otherwise.

Returns:

false if this optional value has a value, true otherwise.

option

public <B> B option(B b,
                    F<A,B> f)

Performs a reduction on this optional value using the given arguments.

Parameters:

b - The value to return if this optional value has no value.

f - The function to apply to the value of this optional value.

Returns:

A reduction on this optional value.

length

public int length()

Returns the length of this optional value; 1 is there is a value, 0 otherwise.

Returns:

The length of this optional value; 1 is there is a value, 0 otherwise.

orSome

public A orSome(P1<A> a)

Returns the value of this optional value or the given argument.

Parameters:

a - The argument to return if this optiona value has no value.

Returns:

The value of this optional value or the given argument.

orSome

public A orSome(A a)

Returns the value of this optional value or the given argument.

Parameters:

a - The argument to return if this optiona value has no value.

Returns:

The value of this optional value or the given argument.

map

public <B> Option<B> map(F<A,B> f)

Maps the given function across this optional value.

Parameters:

f - The function to map across this optional value.

Returns:

A new optional value after the given function has been applied to its element.

foreach

public Unit foreach(F<A,Unit> f)

Performs a side-effect for the value of this optional value.

Parameters:

f - The side-effect to perform for the given element.

Returns:

The unit value.

foreach

public void foreach(Effect<A> f)

Performs a side-effect for the value of this optional value.

Parameters:

f - The side-effect to perform for the given element.

filter

public Option<A> filter(F<A,Boolean> f)

Filters elements from this optional value by returning only elements which produce true when the given function is applied to them.

Parameters:

f - The predicate function to filter on.

Returns:

A new optional value whose value matches the given predicate if it has one.

bind

public <B> Option<B> bind(F<A,Option<B>> f)

Binds the given function across the element of this optional value with a final join.

Parameters:

f - The function to apply to the element of this optional value.

Returns:

A new optional value after performing the map, then final join.

bind

public <B,C> Option<C> bind(Option<B> ob,
                            F<A,F<B,C>> f)

Binds the given function across the element of this optional value and the given optional value with a final join.

Parameters:

ob - A given optional value to bind the given function with.

f - The function to apply to the element of this optional value and the given optional value.

Returns:

A new optional value after performing the map, then final join.

bind

public <B,C,D> Option<D> bind(Option<B> ob,
                              Option<C> oc,
                              F<A,F<B,F<C,D>>> f)

Binds the given function across the element of this optional value and the given optional value with a final join.

Parameters:

ob - A given optional value to bind the given function with.

oc - A given optional value to bind the given function with.

f - The function to apply to the element of this optional value and the given optional value.

Returns:

A new optional value after performing the map, then final join.

bind

public <B,C,D,E> Option<E> bind(Option<B> ob,
                                Option<C> oc,
                                Option<D> od,
                                F<A,F<B,F<C,F<D,E>>>> f)

Binds the given function across the element of this optional value and the given optional value with a final join.

Parameters:

ob - A given optional value to bind the given function with.

oc - A given optional value to bind the given function with.

od - A given optional value to bind the given function with.

f - The function to apply to the element of this optional value and the given optional value.

Returns:

A new optional value after performing the map, then final join.

bind

public <B,C,D,E,F$> Option<F$> bind(Option<B> ob,
                                    Option<C> oc,
                                    Option<D> od,
                                    Option<E> oe,
                                    F<A,F<B,F<C,F<D,F<E,F$>>>>> f)

Binds the given function across the element of this optional value and the given optional value with a final join.

Parameters:

ob - A given optional value to bind the given function with.

oc - A given optional value to bind the given function with.

od - A given optional value to bind the given function with.

oe - A given optional value to bind the given function with.

f - The function to apply to the element of this optional value and the given optional value.

Returns:

A new optional value after performing the map, then final join.

bind

public <B,C,D,E,F$,G> Option<G> bind(Option<B> ob,
                                     Option<C> oc,
                                     Option<D> od,
                                     Option<E> oe,
                                     Option<F$> of,
                                     F<A,F<B,F<C,F<D,F<E,F<F$,G>>>>>> f)

Binds the given function across the element of this optional value and the given optional value with a final join.

Parameters:

ob - A given optional value to bind the given function with.

oc - A given optional value to bind the given function with.

od - A given optional value to bind the given function with.

oe - A given optional value to bind the given function with.

of - A given optional value to bind the given function with.

f - The function to apply to the element of this optional value and the given optional value.

Returns:

A new optional value after performing the map, then final join.

bind

public <B,C,D,E,F$,G,H> Option<H> bind(Option<B> ob,
                                       Option<C> oc,
                                       Option<D> od,
                                       Option<E> oe,
                                       Option<F$> of,
                                       Option<G> og,
                                       F<A,F<B,F<C,F<D,F<E,F<F$,F<G,H>>>>>>> f)

Binds the given function across the element of this optional value and the given optional value with a final join.

Parameters:

ob - A given optional value to bind the given function with.

oc - A given optional value to bind the given function with.

od - A given optional value to bind the given function with.

oe - A given optional value to bind the given function with.

of - A given optional value to bind the given function with.

og - A given optional value to bind the given function with.

f - The function to apply to the element of this optional value and the given optional value.

Returns:

A new optional value after performing the map, then final join.

bind

public <B,C,D,E,F$,G,H,I> Option<I> bind(Option<B> ob,
                                         Option<C> oc,
                                         Option<D> od,
                                         Option<E> oe,
                                         Option<F$> of,
                                         Option<G> og,
                                         Option<H> oh,
                                         F<A,F<B,F<C,F<D,F<E,F<F$,F<G,F<H,I>>>>>>>> f)

Binds the given function across the element of this optional value and the given optional value with a final join.

Parameters:

ob - A given optional value to bind the given function with.

oc - A given optional value to bind the given function with.

od - A given optional value to bind the given function with.

oe - A given optional value to bind the given function with.

of - A given optional value to bind the given function with.

og - A given optional value to bind the given function with.

oh - A given optional value to bind the given function with.

f - The function to apply to the element of this optional value and the given optional value.

Returns:

A new optional value after performing the map, then final join.

sequence

public <B> Option<B> sequence(Option<B> o)

Performs a bind across the optional value, but ignores the element value in the function.

Parameters:

o - The optional value to apply in the final join.

Returns:

A new optional value after the final join.

apply

public <B> Option<B> apply(Option<F<A,B>> of)

Performs function application within an optional value (applicative functor pattern).

Parameters:

of - The optional value of functions to apply.

Returns:

A new optional value after applying the given optional value of functions through this optional value.

orElse

public Option<A> orElse(P1<Option<A>> o)

Returns this optional value if there is one, otherwise, returns the argument optional value.

Parameters:

o - The optional value to return if this optional value has no value.

Returns:

This optional value if there is one, otherwise, returns the argument optional value.

orElse

public Option<A> orElse(Option<A> o)

Returns this optional value if there is one, otherwise, returns the argument optional value.

Parameters:

o - The optional value to return if this optional value has no value.

Returns:

This optional value if there is one, otherwise, returns the argument optional value.

toEither

public <X> Either<X,A> toEither(P1<X> x)

Returns an either projection of this optional value; the given argument in Left if no value, or the value in Right.

Parameters:

x - The value to return in left if this optional value has no value.

Returns:

An either projection of this optional value.

toEither

public <X> Either<X,A> toEither(X x)

Returns an either projection of this optional value; the given argument in Left if no value, or the value in Right.

Parameters:

x - The value to return in left if this optional value has no value.

Returns:

An either projection of this optional value.

toList

public List<A> toList()

Returns a list projection of this optional value.

Returns:

A list projection of this optional value.

toStream

public Stream<A> toStream()

Returns a stream projection of this optional value.

Returns:

A stream projection of this optional value.

toArray

public Array<A> toArray()

Returns an array projection of this optional value.

Returns:

An array projection of this optional value.

toArray

public Array<A> toArray(Class<A[]> c)

Returns an array projection of this optional value.

Parameters:

c - The class type of the array to return.

Returns:

An array projection of this optional value.

forall

public boolean forall(F<A,Boolean> f)

Returns true if this optional value has no value, or the predicate holds for the given predicate function, false otherwise.

Parameters:

f - the predicate function to test on the value of this optional value.

Returns:

true if this optional value has no value, or the predicate holds for the given predicate function, false otherwise.

exists

public boolean exists(F<A,Boolean> f)

Returns true is this optional value has a value and the given predicate function holds on that value, false otherwise.

Parameters:

f - the predicate function to test on the value of this optional value.

Returns:

true is this optional value has a value and the given predicate function holds on that value, false otherwise.

toCollection

public Collection<A> toCollection()

Projects an immutable collection of this optional value.

Returns:

An immutable collection of this optional value.

some_

public static <T> F<T,Option<T>> some_()

some

public static <T> Option<T> some(T t)

Constructs an optional value that has a value of the given argument.

Parameters:

t - The value for the returned optional value.

Returns:

An optional value that has a value of the given argument.

none

public static <T> Option<T> none()

Constructs an optional value that has no value.

Returns:

An optional value that has no value.

fromNull

public static <T> Option<T> fromNull(T t)

Turns an unsafe nullable value into a safe optional value. If t == null then return none, otherwise, return the given value in some.

Parameters:

t - The unsafe nullable value.

Returns:

If t == null then return it in some, otherwise, return none.

join

public static <A> Option<A> join(Option<Option<A>> o)

Joins the given optional value of optional value using a bind operation.

Parameters:

o - The optional value of optional value to join.

Returns:

A new optional value that is the join of the given optional value.

sequence

public static <A> Option<List<A>> sequence(List<Option<A>> a)

Sequence through the option monad.

Parameters:

a - The list of option to sequence.

Returns:

The option of list after sequencing.

iif

public static <A> Option<A> iif(F<A,Boolean> f,
                                A a)

Returns an optional value that has a value of the given argument, if the given predicate holds on that argument, otherwise, returns no value.

Parameters:

f - The predicate to test on the given argument.

a - The argument to test the predicate on and potentially use as the value of the returned optional value.

Returns:

an optional value that has a value of the given argument, if the given predicate holds on that argument, otherwise, returns no value.

iif

public static <A> F2<F<A,Boolean>,A,Option<A>> iif()

First-class version of the iif function.

Returns:

a function that returns an optional value that has a value of the given argument, if the given predicate holds on that argument, or no value otherwise.

somes

public static <A> List<A> somes(List<Option<A>> as)

Returns all the values in the given list.

Parameters:

as - The list of potential values to get actual values from.

Returns:

All the values in the given list.

fromString

public static Option<String> fromString(String s)

Returns an optional non-empty string, or no value if the given string is empty.

Parameters:

s - A string to turn into an optional non-empty string.

Returns:

an optional non-empty string, or no value if the given string is empty.

fromString

public static F<String,Option<String>> fromString()

Returns a function that transforms a string to an optional non-empty string, or no value if the string is empty.

Returns:

a function that transforms a string to an optional non-empty string, or no value if the string is empty.