enumj

Class Nullable<T>

java.lang.Object

enumj.Nullable<T>

Type Parameters:

T - type of contained value.

public final class Nullable<T>
extends Object

Container object which may or may not contain a value. Unlike Optional with which it shares many similarities, Nullable may contain null values.

This is a value-based class.

See Also:

Optional

Method Summary

Modifier and Type	Method and Description
void	clear() Clear the value contained by this Nullable.
static <T> Nullable<T>	empty() Returns an empty Nullable instance.
boolean	equals(Object other)
Nullable<T>	filter(Predicate<? super T> predicate) If a value is present and it matches the given predicate, return a Nullable containing the value, otherwise return an empty Nullable.
<U> Nullable<U>	flatMap(Function<? super T,Nullable<U>> mapper) If a value is present, apply the Nullable-bearing function to it, return that result, otherwise return an empty Nullable.
T	get() If a value is present in this Nullable, returns the value, otherwise throws NoSuchElementException.
int	hashCode()
void	ifPresent(Consumer<? super T> consumer) Return true if a value is present, otherwise false.
boolean	isPresent() Return true if there is a value present, otherwise false.
<U> Nullable<U>	map(Function<? super T,? extends U> mapper) If a value is present, apply the provided mapping function to it and return a Nullable describing the result.
static <T> Nullable<T>	of(Optional<T> value) Returns a Nullable with the value of the specified Optional if any or an empty Nullable otherwise.
static <T> Nullable<T>	of(T value) Returns a Nullable with the specified value.
T	orElse(T other) Return the value if present, otherwise return other.
T	orElseGet(Supplier<? extends T> other) Return the value if present, otherwise invoke other and return the result of that invocation.
<X extends Throwable> T	orElseThrow(Supplier<? extends X> exceptionSupplier) Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.
void	set(T elem) Set a value to this Nullable.
String	toString()

Methods inherited from class java.lang.Object

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

Method Detail

isPresent

public boolean isPresent()

Return true if there is a value present, otherwise false.

Returns:

true if value is present, otherwise false.

get

public T get()

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

Returns:

the value help by this Nullable.

Throws:

NoSuchElementException - if there is no value present.

See Also:

Nullable

set

public void set(T elem)

Set a value to this Nullable.

Parameters:

elem - value to set.

See Also:

Nullable

clear

public void clear()

Clear the value contained by this Nullable.

See Also:

Nullable

orElse

public 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.

Returns:

the value, if present, otherwise other.

orElseGet

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

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

Parameters:

other - a Supplier whose result is returned if no value is present.

Returns:

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

Throws:

NullPointerException - if value is not present and other is null.

orElseThrow

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

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.

Type Parameters:

X - type of exception to be thrown.

Parameters:

exceptionSupplier - the supplier which will return the exception to be thrown.

Returns:

the present value.

Throws:

X - if there is no value present.

X extends Throwable

equals

public boolean equals(Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

empty

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

Returns an empty Nullable instance. No value is present for this Nullable.

Type Parameters:

T - type of the non-existent value.

Returns:

an empty Nullable.

of

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

Returns a Nullable with the specified value.

Type Parameters:

T - the class of value.

Parameters:

value - the value to be present.

Returns:

a Nullable with the value present.

of

public static <T> Nullable<T> of(Optional<T> value)

Returns a Nullable with the value of the specified Optional if any or an empty Nullable otherwise.

Type Parameters:

T - the class of value.

Parameters:

value - Optional value to be present.

Returns:

a Nullable with the value present.

filter

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

If a value is present and it matches the given predicate, return a Nullable containing the value, otherwise return an empty Nullable.

Parameters:

predicate - a predicate to apply to the value, if present.

Returns:

a Nullable describing the value of this Nullable if present and it matches the given predicate, otherwise an empty Nullable.

flatMap

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

If a value is present, apply the Nullable-bearing function to it, return that result, otherwise return an empty Nullable.

Type Parameters:

U - type parameter to the Nullable returned by mapper.

Parameters:

mapper - a mapping Function to apply to the value, if any.

Returns:

the result of applying a Nullable-bearing mapping function to the value of this Nullable, if a value is present, otherwise an empty Nullable.

ifPresent

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

Return true if a value is present, otherwise false.

Parameters:

consumer - block to be executed if a value is present.

map

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

If a value is present, apply the provided mapping function to it and return a Nullable describing the result. Otherwise return an empty Nullable.

Type Parameters:

U - the type of the result of the mapping function.

Parameters:

mapper - a mapping Function to apply to the value, if present.

Returns:

a Nullable describing the result of applying a mapping function to the value of this Nullable, if a value is present, otherwise an empty Nullable.