Optional (Lightweight-Stream-API 1.2.1 API)

java.lang.Object
- com.annimon.stream.Optional<T>

Type Parameters:

T - the type of the inner value
```
public class Optional<T>
extends Object
```
A container object which may or may not contain a non-null value.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`<R> R`	`custom(Function<Optional<T>,R> function)` Applies custom operator on `Optional`.
`static <T> Optional<T>`	`empty()` Returns an empty `Optional`.
`boolean`	`equals(Object obj)`
`Optional<T>`	`executeIfAbsent(Runnable action)` Invokes action function if value is absent.
`Optional<T>`	`executeIfPresent(Consumer<? super T> consumer)` Invokes consumer function with the value if present.
`Optional<T>`	`filter(Predicate<? super T> predicate)` Performs filtering on inner value if it is present.
`Optional<T>`	`filterNot(Predicate<? super T> predicate)` Performs negated filtering on inner value if it is present.
`<U> Optional<U>`	`flatMap(Function<? super T,Optional<U>> mapper)` Invokes mapping function with `Optional` result if value is present.
`T`	`get()` Returns an inner value if present, otherwise throws `NoSuchElementException`.
`int`	`hashCode()`
`void`	`ifPresent(Consumer<? super T> consumer)` Invokes consumer function with value if present.
`void`	`ifPresentOrElse(Consumer<? super T> consumer, Runnable emptyAction)` If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
`boolean`	`isEmpty()` Checks the value is not present.
`boolean`	`isPresent()` Checks value present.
`<U> Optional<U>`	`map(Function<? super T,? extends U> mapper)` Invokes the given mapping function on inner value if present.
`OptionalBoolean`	`mapToBoolean(ToBooleanFunction<? super T> mapper)` Invokes mapping function on inner value if present.
`OptionalDouble`	`mapToDouble(ToDoubleFunction<? super T> mapper)` Invokes mapping function on inner value if present.
`OptionalInt`	`mapToInt(ToIntFunction<? super T> mapper)` Invokes the given mapping function on inner value if present.
`OptionalLong`	`mapToLong(ToLongFunction<? super T> mapper)` Invokes mapping function on inner value if present.
`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` with the specified value, or empty `Optional` if value is null.
`Optional<T>`	`or(Supplier<Optional<T>> supplier)` Returns current `Optional` if value is present, otherwise returns an `Optional` produced by supplier function.
`T`	`orElse(T other)` Returns inner value if present, otherwise returns `other`.
`T`	`orElseGet(Supplier<? extends T> other)` Returns inner value if present, otherwise returns value produced by supplier function.
`T`	`orElseThrow()` Returns inner value if present, otherwise throws `NoSuchElementException`.
`<X extends Throwable> T`	`orElseThrow(Supplier<? extends X> exc)` Returns inner value if present, otherwise throws the exception provided by supplier function.
`<R> Optional<R>`	`select(Class<R> clazz)` Keeps inner value only if is present and instance of given class.
`Stream<T>`	`stream()` Wraps a value into `Stream` if present, otherwise returns an empty `Stream`.
`String`	`toString()`

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Method Detail
 - of
```
public static <T> Optional<T> of(T value)
```
 Returns an Optional with the specified present non-null value.
 
 Type Parameters:
 
 T - the type of value
 
 Parameters:
 
 value - the value to be present, must be non-null
 
 Returns:
 
 an Optional
 
 Throws:
 
 NullPointerException - if value is null
 
 See Also:
 
 ofNullable(java.lang.Object)
 - ofNullable
```
public static <T> Optional<T> ofNullable(T value)
```
 Returns an Optional with the specified value, or empty Optional if value is null.
 
 Type Parameters:
 
 T - the type of value
 
 Parameters:
 
 value - the value which can be null
 
 Returns:
 
 an Optional
 
 See Also:
 
 of(java.lang.Object)
 - empty
```
public static <T> Optional<T> empty()
```
 Returns an empty Optional.
 
 Type Parameters:
 
 T - the type of value
 
 Returns:
 
 an Optional
 - get
```
public T get()
```
 Returns an inner value if present, otherwise throws NoSuchElementException. Since 1.2.0 prefer orElseThrow() method as it has readable name.
 
 Returns:
 
 the inner value of Optional
 
 Throws:
 
 NoSuchElementException - if value is not present
 
 See Also:
 
 orElseThrow()
 - isPresent
```
public boolean isPresent()
```
 Checks value present.
 
 Returns:
 
 true if a value present, false otherwise
 - isEmpty
```
public boolean isEmpty()
```
 Checks the value is not present.
 
 Returns:
 
 true if a value is not present, false otherwise
 
 Since:
 
 1.2.1
 - ifPresent
```
public void ifPresent(Consumer<? super T> consumer)
```
 Invokes consumer function with value if present.
 
 Parameters:
 
 consumer - the consumer function
 - ifPresentOrElse
```
public void ifPresentOrElse(Consumer<? super T> consumer,
 Runnable emptyAction)
```
 If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
 
 Parameters:
 
 consumer - the consumer function to be executed, if a value is present
 
 emptyAction - the empty-based action to be performed, if no value is present
 
 Throws:
 
 NullPointerException - if a value is present and the given consumer function is null, or no value is present and the given empty-based action is null.
 - executeIfPresent
```
public Optional<T> executeIfPresent(Consumer<? super T> consumer)
```
 Invokes consumer function with the value if present. This method same as ifPresent, but does not breaks chaining
 
 Parameters:
 
 consumer - consumer function
 
 Returns:
 
 this Optional
 
 Since:
 
 1.1.2
 
 See Also:
 
 ifPresent(com.annimon.stream.function.Consumer)
 - executeIfAbsent
```
public Optional<T> executeIfAbsent(Runnable action)
```
 Invokes action function if value is absent.
 
 Parameters:
 
 action - action that invokes if value absent
 
 Returns:
 
 this Optional
 
 Since:
 
 1.1.2
 - custom
```
public <R> R custom(Function<Optional<T>,R> function)
```
 Applies custom operator on Optional.
 
 Type Parameters:
 
 R - the type of the result
 
 Parameters:
 
 function - a transforming function
 
 Returns:
 
 a result of the transforming function
 
 Throws:
 
 NullPointerException - if function is null
 
 Since:
 
 1.1.9
 - filter
```
public Optional<T> filter(Predicate<? super T> predicate)
```
 Performs filtering on inner value if it is present.
 
 Parameters:
 
 predicate - a predicate function
 
 Returns:
 
 this Optional if the value is present and matches predicate, otherwise an empty Optional
 - filterNot
```
public Optional<T> filterNot(Predicate<? super T> predicate)
```
 Performs negated filtering on inner value if it is present.
 
 Parameters:
 
 predicate - a predicate function
 
 Returns:
 
 this Optional if the value is present and doesn't matches predicate, otherwise an empty Optional
 
 Since:
 
 1.1.9
 - map
```
public  Optional map(Function<? super T,? extends U> mapper)
```
 Invokes the given mapping function on inner value if present.
 
 Type Parameters:
 
 U - the type of result value
 
 Parameters:
 
 mapper - mapping function
 
 Returns:
 
 an Optional with transformed value if present, otherwise an empty Optional
 
 Throws:
 
 NullPointerException - if value is present and mapper is null
 - mapToInt
```
public OptionalInt mapToInt(ToIntFunction<? super T> mapper)
```
 Invokes the given mapping function on inner value if present.
 
 Parameters:
 
 mapper - mapping function
 
 Returns:
 
 an OptionalInt with transformed value if present, otherwise an empty OptionalInt
 
 Throws:
 
 NullPointerException - if value is present and mapper is null
 
 Since:
 
 1.1.3
 - mapToLong
```
public OptionalLong mapToLong(ToLongFunction<? super T> mapper)
```
 Invokes mapping function on inner value if present.
 
 Parameters:
 
 mapper - mapping function
 
 Returns:
 
 an OptionalLong with transformed value if present, otherwise an empty OptionalLong
 
 Throws:
 
 NullPointerException - if value is present and mapper is null
 
 Since:
 
 1.1.4
 - mapToDouble
```
public OptionalDouble mapToDouble(ToDoubleFunction<? super T> mapper)
```
 Invokes mapping function on inner value if present.
 
 Parameters:
 
 mapper - mapping function
 
 Returns:
 
 an OptionalDouble with transformed value if present, otherwise an empty OptionalDouble
 
 Throws:
 
 NullPointerException - if value is present and mapper is null
 
 Since:
 
 1.1.4
 - mapToBoolean
```
public OptionalBoolean mapToBoolean(ToBooleanFunction<? super T> mapper)
```
 Invokes mapping function on inner value if present.
 
 Parameters:
 
 mapper - mapping function
 
 Returns:
 
 an OptionalBoolean with transformed value if present, otherwise an empty OptionalBoolean
 
 Throws:
 
 NullPointerException - if value is present and mapper is null
 - flatMap
```
public  Optional flatMap(Function<? super T,Optional> mapper)
```
 Invokes mapping function with Optional result if value is present.
 
 Type Parameters:
 
 U - the type of result value
 
 Parameters:
 
 mapper - mapping function
 
 Returns:
 
 an Optional with transformed value if present, otherwise an empty Optional
 - stream
```
public Stream<T> stream()
```
 Wraps a value into Stream if present, otherwise returns an empty Stream.
 
 Returns:
 
 the optional value as a Stream
 - select
```
public <R> Optional<R> select(Class<R> clazz)
```
 Keeps inner value only if is present and instance of given class.
 
 Type Parameters:
 
 R - a type of instance to select.
 
 Parameters:
 
 clazz - a class which instance should be selected
 
 Returns:
 
 an Optional with value of type class if present, otherwise an empty Optional
 - or
```
public Optional<T> or(Supplier<Optional<T>> supplier)
```
 Returns current Optional if value is present, otherwise returns an Optional produced by supplier function.
 
 Parameters:
 
 supplier - supplier function that produces an Optional to be returned
 
 Returns:
 
 this Optional if value is present, otherwise an Optional produced by supplier function
 
 Throws:
 
 NullPointerException - if value is not present and supplier or value produced by it is null
 - orElse
```
public T orElse(T other)
```
 Returns inner value if present, otherwise returns other.
 
 Parameters:
 
 other - the value to be returned if inner value is not present
 
 Returns:
 
 inner value if present, otherwise other
 - orElseGet
```
public T orElseGet(Supplier<? extends T> other)
```
 Returns inner value if present, otherwise returns value produced by supplier function.
 
 Parameters:
 
 other - supplier function that produces value if inner value is not present
 
 Returns:
 
 inner value if present, otherwise value produced by supplier function
 - orElseThrow
```
public T orElseThrow()
```
 Returns inner value if present, otherwise throws NoSuchElementException.
 
 Returns:
 
 inner value if present
 
 Throws:
 
 NoSuchElementException - if inner value is not present
 
 Since:
 
 1.2.0
 - orElseThrow
```
public <X extends Throwable> T orElseThrow(Supplier<? extends X> exc)
 throws X extends Throwable
```
 Returns inner value if present, otherwise throws the exception provided by supplier function.
 
 Type Parameters:
 
 X - the type of exception to be thrown
 
 Parameters:
 
 exc - supplier function that produces an exception to be thrown
 
 Returns:
 
 inner value if present
 
 Throws:
 
 X - if inner value is not present
 
 X extends Throwable
 - equals
```
public boolean equals(Object obj)
```
 Overrides:
 
 equals in class Object
 - hashCode
```
public int hashCode()
```
 Overrides:
 
 hashCode in class Object
 - toString
```
public String toString()
```
 Overrides:
 
 toString in class Object

Class Optional<T>

Method Summary

Methods inherited from class java.lang.Object

Method Detail

of

ofNullable

empty

get

isPresent

isEmpty

ifPresent

ifPresentOrElse

executeIfPresent

executeIfAbsent

custom

filter

filterNot

map

mapToInt

mapToLong

mapToDouble

mapToBoolean

flatMap

stream

select

or

orElse

orElseGet

orElseThrow

orElseThrow

equals

hashCode

toString