org.organicdesign.fp.oneOf

Interface Option<T>

All Superinterfaces:

Serializable

All Known Implementing Classes:

None, Option.Some

public interface Option<T>
extends Serializable

Indicates presence or absence of a value (null is a valid, present value). None often means "end of stream" or "none found". This is NOT a type-safe null (unless you want that, in which case use the someOrNullNoneOf(Object) static factory method). You can think of this class as OneOf1OrNone.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Option.Some<T> Represents the presence of a value, even if that value is null.

Field Summary

Fields

Modifier and Type	Field and Description
static Option	NONE None is a singleton and this is its only instance.

Method Summary

Modifier and Type	Method and Description
T	get() Return the value wrapped in this Option.
T	getOrElse(T t) If this is Some, return the value wrapped in this Option.
boolean	isSome() Is this Some?
<U> U	match(Fn1<T,U> has, Fn0<U> hasNot) Pass in a function to execute if its Some and another to execute if its None.
static <T> Option<T>	none() Calling this instead of referring to NONE directly can make the type infrencer happy.
static <T> Option<T>	of(T t) Deprecated.
static <T> Option<T>	some(T t) Public static factory method for constructing the Some Option.
static <T> Option<T>	someOrNullNoneOf(T t) Construct an option, but if t is null, make it None instead of Some.
<U> Option<U>	then(Fn1<T,Option<U>> f) If this is Some, Apply the given function, else return None.

Field Detail

NONE

static final Option NONE

None is a singleton and this is its only instance.

Method Detail

get

T get()

Return the value wrapped in this Option. Only safe to call this on Some.

getOrElse

T getOrElse(T t)

If this is Some, return the value wrapped in this Option. Otherwise, return the given value.

then

<U> Option<U> then(Fn1<T,Option<U>> f)

If this is Some, Apply the given function, else return None. Use this to chain options together, failing fast at the first none() or continuing through as many operations that return some as possible.

isSome

boolean isSome()

Is this Some?

match

<U> U match(Fn1<T,U> has,
            Fn0<U> hasNot)

Pass in a function to execute if its Some and another to execute if its None.

none

static <T> Option<T> none()

Calling this instead of referring to NONE directly can make the type infrencer happy.

of

@Deprecated
static <T> Option<T> of(T t)

Deprecated.

Would some(Object) be better for your purposes? For some reason, this returns none if you pass it a none. This is like flatmapping Options. Is this good for chaining or is this just weird? If the first, I'm going to rename it flatten() or flatmap() or something. If the second, it should be deleted. Remember, you also have Or for chaining or returning an error which is probably a better choice than Option for that kind of thing.

some

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

Public static factory method for constructing the Some Option.

someOrNullNoneOf

static <T> Option<T> someOrNullNoneOf(T t)

Construct an option, but if t is null, make it None instead of Some.