org.osgl

Class Osgl.Option<T>

java.lang.Object

org.osgl.Osgl.Option<T>

Type Parameters:

T - the element type

All Implemented Interfaces:

Serializable, Iterable<T>

Direct Known Subclasses:

Osgl.None, Osgl.Some

Enclosing class:

Osgl

public abstract static class Osgl.Option<T>
extends Object
implements Iterable<T>, Serializable

Defines an option of element T. This class can be used to implement the else-if semantic in functional programming and eliminate the null value

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	Osgl.Option.f The runtime/instance function namespace

Field Summary

Fields

Modifier and Type	Field and Description
Osgl.Option.f	f A reference to this runtime function namesapce

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj)
Osgl.Option<T>	filter(Osgl.Function<? super T,Boolean> predicate) If a value is present, and the value matches the given predicate, return an Option describing the value, otherwise return Osgl.NONE.
<B> Osgl.Option<B>	flatMap(Osgl.Function<? super T,Osgl.Option<B>> mapper) If a value is present, apply the provided Option-bearing mapping function to it, return that result, otherwise return Osgl.NONE.
abstract T	get() If a value is present in this Option, returns the value, otherwise throws NoSuchElementException.
int	hashCode()
boolean	isDefined() Returns true if this Option is not Osgl.NONE
<B> Osgl.Option<B>	map(Osgl.Function<? super T,? extends B> mapper) If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Option describing the result.
static <T> Osgl.None<T>	none()
boolean	notDefined() Negate of isDefined()
static <T> Osgl.Option<T>	of(T value) Returns an Option with the specified present value if it is not null or Osgl.NONE otherwise.
T	orElse(Osgl.Func0<? extends T> other) Return the value if present, otherwise invoke other and return the result of that invocation.
T	orElse(T other) Return the value if present, otherwise return other.
void	runWith(Osgl.Function<? super T,?> consumer)
static <T> Osgl.Some<T>	some(T value) Returns an Option with the specified present non-null value.
abstract String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, iterator, spliterator

Field Detail

f

public final Osgl.Option.f f

A reference to this runtime function namesapce

Method Detail

isDefined

public final boolean isDefined()

Returns true if this Option is not Osgl.NONE

Returns:

true if there is a value present, otherwise false

Since:

0.2

notDefined

public boolean notDefined()

Negate of isDefined()

Returns:

true if this option is not defined

Since:

0.2

get

public abstract T get()
               throws NoSuchElementException

If a value is present in this Option, returns the value, otherwise throws NoSuchElementException.

Returns:

the non-null value held by this Option

Throws:

NoSuchElementException - if this Option is Osgl.NONE

filter

public final Osgl.Option<T> filter(Osgl.Function<? super T,Boolean> predicate)

If a value is present, and the value matches the given predicate, return an Option describing the value, otherwise return Osgl.NONE.

Parameters:

predicate - the function to test the value held by this Option

Returns:

an Option describing the value of this Option if a value is present and the value matches the given predicate, otherwise Osgl.NONE

map

public final <B> Osgl.Option<B> map(Osgl.Function<? super T,? extends B> mapper)

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Option describing the result. Otherwise return Osgl.NONE.

Type Parameters:

B - The type of the result of the mapping function

Parameters:

mapper - a mapping function to apply to the value, if present

Returns:

an Optional describing the result of applying a mapping function to the value of this Option, if a value is present, otherwise Osgl.NONE

Throws:

NullPointerException - if the mapper function is null

Since:

0.2

flatMap

public final <B> Osgl.Option<B> flatMap(Osgl.Function<? super T,Osgl.Option<B>> mapper)

If a value is present, apply the provided Option-bearing mapping function to it, return that result, otherwise return Osgl.NONE. This method is similar to map(Osgl.Function), but the provided mapper is one whose result is already an Option, and if invoked, flatMap does not wrap it with an additional Option.

Type Parameters:

B - The type parameter to the Option returned by

Parameters:

mapper - a mapping function to apply to the value,

Returns:

the result of applying an Option-bearing mapping function to the value of this Option, if a value is present, otherwise Osgl.NONE

Throws:

NullPointerException - if the mapping function is null or returns a null result

Since:

0.2

orElse

public final T orElse(T other)

Return the value if present, otherwise return other.

Parameters:

other - the value to be returned if there is no value present, may be null

Returns:

the value, if present, otherwise other

orElse

public final T orElse(Osgl.Func0<? extends T> other)

Return the value if present, otherwise invoke other and return the result of that invocation.

Parameters:

other - the function that is applied when no value is presented

Returns:

the value if present otherwise the result of other.apply()

Throws:

NullPointerException - if value is not present and other is null

Since:

0.2

runWith

public final void runWith(Osgl.Function<? super T,?> consumer)

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public abstract String toString()

Overrides:

toString in class Object

none

public static <T> Osgl.None<T> none()

some

public static <T> Osgl.Some<T> some(T value)

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

Type Parameters:

T - the type of the value

Parameters:

value - the value that cannot be null

Returns:

an Option instance describing the value

Throws:

NullPointerException - if the value specified is null

Since:

0.2

of

public static <T> Osgl.Option<T> of(T value)

Returns an Option with the specified present value if it is not null or Osgl.NONE otherwise.

Type Parameters:

T - the type of the value

Parameters:

value - the value

Returns:

an Option describing the value if it is not null or Osgl.NONE if the value is null

Since:

0.2