me.lucko.helper.utils

Class NullableOptional<T>

java.lang.Object

me.lucko.helper.utils.NullableOptional<T>

public final class NullableOptional<T>
extends Object

A container object which may or may not contain a value.

An extension of Java's Optional, which can hold nullable values.

Method Summary

Modifier and Type	Method and Description
Optional<T>	asOptional() If a value is present in this NullableOptional, returns the result of passing the value to Optional.ofNullable(Object).
static <T> NullableOptional<T>	empty() Returns an empty NullableOptional instance.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this NullableOptional.
NullableOptional<T>	filter(Predicate<? super T> predicate) If a value is present, and the value matches the given predicate, return an NullableOptional describing the value, otherwise return an empty NullableOptional.
<U> NullableOptional<U>	flatMap(Function<? super T,NullableOptional<U>> mapper) If a value is present, apply the provided NullableOptional-bearing mapping function to it, return that result, otherwise return an empty NullableOptional.
static <T> NullableOptional<T>	fromOptional(Optional<T> value) Returns a NullableOptional describing the specified optional.
T	get() If a value is present in this NullableOptional, returns the value, otherwise throws NoSuchElementException.
int	hashCode() Returns the hash code value of the present value, if any, or -1 if no value is present.
void	ifPresent(Consumer<? super T> consumer) If a value is present, invoke the specified consumer with the value, otherwise do nothing.
boolean	isPresent() Return true if there is a value present, otherwise false.
<U> NullableOptional<U>	map(Function<? super T,? extends U> mapper) If a value is present, apply the provided mapping function to it, and return an NullableOptional describing the result.
static <T> NullableOptional<T>	of(T value) Returns a NullableOptional with the specified present 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.
String	toString() Returns a non-empty string representation of this NullableOptional suitable for debugging.

Methods inherited from class java.lang.Object

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

Method Detail

empty

@Nonnull
public static <T> NullableOptional<T> empty()

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

Type Parameters:

T - Type of the non-existent value

Returns:

an empty NullableOptional

of

@Nonnull
public static <T> NullableOptional<T> of(@Nullable
                                                   T value)

Returns a NullableOptional with the specified present value.

Type Parameters:

T - the class of the value

Parameters:

value - the value to be present

Returns:

a NullableOptional with the value present

fromOptional

@Nonnull
public static <T> NullableOptional<T> fromOptional(@Nonnull
                                                             Optional<T> value)

Returns a NullableOptional describing the specified optional.

Type Parameters:

T - the class of the value

Parameters:

value - the possibly-empty value to describe

Returns:

a NullableOptional with a present value if the specified value is present, otherwise an empty NullableOptional

get

@Nullable
public T get()

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

Returns:

the value held by this NullableOptional

Throws:

NoSuchElementException - if there is no value present

See Also:

isPresent()

asOptional

@Nonnull
public Optional<T> asOptional()

If a value is present in this NullableOptional, returns the result of passing the value to Optional.ofNullable(Object). Otherwise returns an empty optional.

Returns:

an Optional representing the value held by this NullableOptional

See Also:

Optional.ofNullable(Object)

isPresent

public boolean isPresent()

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

Returns:

true if there is a value present, otherwise false

ifPresent

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

If a value is present, invoke the specified consumer with the value, otherwise do nothing.

Parameters:

consumer - block to be executed if a value is present

Throws:

NullPointerException - if value is present and consumer is null

filter

@Nonnull
public NullableOptional<T> filter(@Nonnull
                                            Predicate<? super T> predicate)

If a value is present, and the value matches the given predicate, return an NullableOptional describing the value, otherwise return an empty NullableOptional.

Parameters:

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

Returns:

an NullableOptional describing the value of this NullableOptional if a value is present and the value matches the given predicate, otherwise an empty NullableOptional

Throws:

NullPointerException - if the predicate is null

map

@Nonnull
public <U> NullableOptional<U> map(@Nonnull
                                             Function<? super T,? extends U> mapper)

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

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:

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

Throws:

NullPointerException - if the mapping function is null

flatMap

@Nonnull
public <U> NullableOptional<U> flatMap(@Nonnull
                                                 Function<? super T,NullableOptional<U>> mapper)

If a value is present, apply the provided NullableOptional-bearing mapping function to it, return that result, otherwise return an empty NullableOptional. This method is similar to map(Function), but the provided mapper is one whose result is already an NullableOptional, and if invoked, flatMap does not wrap it with an additional NullableOptional.

Type Parameters:

U - The type parameter to the NullableOptional returned by

Parameters:

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

Returns:

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

Throws:

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

orElse

@Nullable
public T orElse(@Nullable
                           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

orElseGet

@Nullable
public T orElseGet(@Nonnull
                              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

@Nullable
public <X extends Throwable> T orElseThrow(@Nonnull
                                                      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 the 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

NullPointerException - if no value is present and exceptionSupplier is null

X extends Throwable

equals

public boolean equals(Object obj)

Indicates whether some other object is "equal to" this NullableOptional. The other object is considered equal if:

• it is also an NullableOptional and;
• both instances have no value present or;
• the present values are "equal to" each other via equals().

Overrides:

equals in class Object

Parameters:

obj - an object to be tested for equality

Returns:

{code true} if the other object is "equal to" this object otherwise false

hashCode

public int hashCode()

Returns the hash code value of the present value, if any, or -1 if no value is present.

Overrides:

hashCode in class Object

Returns:

hash code value of the present value or 0 if no value is present

See Also:

Objects.hashCode(Object)

toString

public String toString()

Returns a non-empty string representation of this NullableOptional suitable for debugging.

Overrides:

toString in class Object

Returns:

the string representation of this instance