com.solidfire.core.javautil

Class Optional<T>

Object

Optional<T>

Type Parameters:

T -

All Implemented Interfaces:

Serializable

public final class Optional<T>
extends Object
implements Serializable

An implementation of Optional that should be completely equivalent to the Java 8 Optional type.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static Optional<Double>	EMPTY_DOUBLE
static Optional<Double[]>	EMPTY_DOUBLE_ARRAY
static Optional<Long>	EMPTY_LONG
static Optional<Long[]>	EMPTY_LONG_ARRAY
static Optional<Map<String,Object>>	EMPTY_MAP
static Optional<String>	EMPTY_STRING
static Optional<String[]>	EMPTY_STRING_ARRAY

Method Summary

Methods

Modifier and Type	Method and Description
static <T> Optional<T>	empty() Create an empty Optional value.
boolean	equals(Object obj)
Optional<T>	filter(Predicate<? super T> predicate) If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.
<U> Optional<U>	flatMap(Function<? super T,Optional<U>> mapper) If a value is present, apply the provided Optional-bearing mapping function to it, return that result, otherwise return an empty Optional.
T	get() If a value is present in this Optional, returns the value, otherwise throws NoSuchElementException.
int	hashCode()
void	ifPresent(Consumer<? super T> consumer) If a value is present, invoke the specified consumer with the value, otherwise do nothing.
boolean	isPresent() Returns true if there is a value present, otherwise false.
<U> Optional<U>	map(Function<? super T,? extends U> mapper) If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result.
static <T> Optional<T>	of(T value) Returns an Optional with the specified present non-null value
static <T> Optional<T>	ofNullable(T value) Returns an Optional describing the specified value, if non-null, otherwise returns an empty Optional.
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()

Methods inherited from class Object

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

Field Detail

EMPTY_STRING

public static final Optional<String> EMPTY_STRING

EMPTY_STRING_ARRAY

public static final Optional<String[]> EMPTY_STRING_ARRAY

EMPTY_LONG

public static final Optional<Long> EMPTY_LONG

EMPTY_LONG_ARRAY

public static final Optional<Long[]> EMPTY_LONG_ARRAY

EMPTY_DOUBLE

public static final Optional<Double> EMPTY_DOUBLE

EMPTY_DOUBLE_ARRAY

public static final Optional<Double[]> EMPTY_DOUBLE_ARRAY

EMPTY_MAP

public static final Optional<Map<String,Object>> EMPTY_MAP

Method Detail

empty

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

Create an empty Optional value.

If you are stuck in Java 1.7, you might have to specify the type manually with Optional.empty() or Optional.empty(Class);

Returns:

an empty Optional

of

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

Returns an Optional with the specified present non-null value

Type Parameters:

T - the class of the value

Parameters:

value - the value to be present, which must be non-null

Returns:

an Optional with the value present

ofNullable

public static <T> Optional<T> ofNullable(T value)

Returns an Optional describing the specified value, if non-null, otherwise returns an empty Optional.

Type Parameters:

T - the class of the value

Parameters:

value - the optional value to create

Returns:

an Optional with a present value if the specified value is non-null, otherwise an empty Optional

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

filter

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

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

Parameters:

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

Returns:

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

isPresent

public boolean isPresent()

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

Returns:

true if there is a value present, otherwise false

flatMap

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

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

Type Parameters:

U - The type parameter to the Optional returned by

Parameters:

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

Returns:

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

get

public T get()

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

Returns:

the non-null value held by this Optional

hashCode

public int hashCode()

Overrides:

hashCode in class Object

ifPresent

public void ifPresent(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

map

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

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise return an empty Optional.

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

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, may be null

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()

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 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

X extends Throwable

toString

public String toString()

Overrides:

toString in class Object