javascalautils

Class None<T>

java.lang.Object

javascalautils.None<T>

Type Parameters:

T - The type of the value represented by this instance

All Implemented Interfaces:

Serializable, Iterable<T>, Option<T>

public final class None<T>
extends Object
implements Option<T>, Serializable

Represents an empty Option.
The None is a replacement for null values representing a non-existing value.
One can consider None as a collection of size 0.
Instances of None should not be created directly, rather use the factory methods provided on Option.

• Option.empty()
• Option.None()

Since None anyways cannot represent a value it is preferable to use it as a singleton saving unnecessary instance creation.
For examples on usage refer to the documentation for Option.

Since:

1.0

Author:

Peter Nerg

See Also:

Serialized Form

Field Summary

Fields inherited from interface javascalautils.Option

DEFAULT_NONE

Constructor Summary

Constructors

Constructor and Description
None()

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object other) Returns true if other is a None as None is stateless comparing it to some other None is therefore always the same, false otherwise.
boolean	exists(java.util.function.Predicate<T> predicate) Always returns false.
<R> Option<R>	flatMap(java.util.function.Function<T,Option<R>> function) Always returns this.
T	get() Always throws NoSuchElementException since None cannot per definition hold any value.
T	getOrElse(java.util.function.Supplier<T> supplier) Always the value provided by the supplier.
int	hashCode() Always returns 0 as None is stateless and has no value.
<R> Option<R>	map(java.util.function.Function<T,R> function) Always returns this.
Option<T>	orElse(java.util.function.Supplier<Option<T>> s) Always the value provided by the supplier.
java.util.stream.Stream<T>	stream() Always returns an empty stream.
String	toString() Returns a String representation of the instance.

Methods inherited from class java.lang.Object

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

Methods inherited from interface javascalautils.Option

apply, asOptional, contains, count, empty, filter, filterNot, forall, isDefined, isEmpty, iterator, None, ofOptional, orNull

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

None

public None()

Method Detail

get

public T get()

Always throws NoSuchElementException since None cannot per definition hold any value.

Specified by:

get in interface Option<T>

Returns:

The value of the Option

getOrElse

public T getOrElse(java.util.function.Supplier<T> supplier)

Always the value provided by the supplier.

Specified by:

getOrElse in interface Option<T>

Parameters:

supplier - The supplier to use in case this is a None

Returns:

The value of the Option or the value provided by the supplier

exists

public boolean exists(java.util.function.Predicate<T> predicate)

Always returns false.
I.e. the predicate is never used as None represents nothing/no value.

Specified by:

exists in interface Option<T>

Parameters:

predicate - The predicate

Returns:

If the predicate matches

map

public <R> Option<R> map(java.util.function.Function<T,R> function)

Always returns this.
I.e. the function is never used as None represents nothing/no value.

Specified by:

map in interface Option<T>

Type Parameters:

R - The type for the return value from the function

Parameters:

function - The function to use

Returns:

The Option containing the mapped value

flatMap

public <R> Option<R> flatMap(java.util.function.Function<T,Option<R>> function)

Always returns this.
I.e. the function is never used as None represents nothing/no value.

Specified by:

flatMap in interface Option<T>

Type Parameters:

R - The type for the return value from the function

Parameters:

function - The function to use

Returns:

The Option containing the mapped value

orElse

public Option<T> orElse(java.util.function.Supplier<Option<T>> s)

Always the value provided by the supplier.

Specified by:

orElse in interface Option<T>

Parameters:

s - The supplier to use in case of None

Returns:

The value provided by the supplier

stream

public java.util.stream.Stream<T> stream()

Always returns an empty stream.

Specified by:

stream in interface Option<T>

Returns:

Empty stream

equals

public boolean equals(Object other)

Returns true if other is a None as None is stateless comparing it to some other None is therefore always the same, false otherwise.

Overrides:

equals in class Object

Parameters:

other - The other object to compare to

Returns:

true if other is None, false otherwise

hashCode

public int hashCode()

Always returns 0 as None is stateless and has no value.

Overrides:

hashCode in class Object

Returns:

0

toString

public String toString()

Returns a String representation of the instance.

Overrides:

toString in class Object