Option (Java Scala Utils 1.5 API)

Type Parameters:

T - The type of the value represented by this instance

All Superinterfaces:

Iterable<T>

All Known Implementing Classes:

None, Some
```
public interface Option<T>
extends Iterable<T>
```
Represents optional values.
Instances of Option are either an instance of Some or None.
Some holds a non-null value whilst None holds no value.
The primary use case is to replace ugly null-checks.
Consider the method:
```
 SomeData getDataIfExists(SomeInput input) {
   if(haveData(input) {
      return getSomeDataFromInternalStorage();
   }
   return null;
 }
 
```
The above method causes the user to do null-checks in case the method returned a proper value or not.
A neater way would be:
```
 Option<SomeData> getDataIfExists(SomeInput input) {
   if(haveData(input) {
      return new Some<>(getSomeDataFromInternalStorage());
   }
   return Option.None();
 }
 
```
Another example is the usage of Maps.
Performing a get on a Map will either yield the value of the key or null if no such key existed.
Consider the Map:

Map<String, SomeData> map = ....

To avoid null checks one could do like so:

Option<SomeData> option = Option.apply(map.get("someKey"));
Now you have a guaranteed non-null value with which you can work with without performing constant null-checks.
Statically importing methods from the companion class (OptionCompanion) to Option one can get that Scala feel of declaration.
```
 import static javascalautils.OptionCompanion.Option;
 
 Option<String> option = Option(map.get("someKey"));
 
```
Since:

1.0

Author:

Peter Nerg

Field Summary

Fields
Modifier and Type Field and Description

static None DEFAULT_NONE
This is a singleton None since it anyways cannot represent a state.

Fields
Modifier and Type	Field and Description
`static None`	`DEFAULT_NONE` This is a singleton `None` since it anyways cannot represent a state.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`static <T> Option<T>`	`apply(T value)` Creates an instance of Option.
`default Optional<T>`	`asOptional()` Converts this `Option` to a corresponding `Optional`.
`default boolean`	`contains(T other)` Returns `true` if this is a `Some` containing the provided object, else `false`.
`default int`	`count()` Returns the count which means `1` for nonempty Option's and `0` for empty.
`static <T> Option<T>`	`empty()` Returns an empty Option.
`boolean`	`exists(java.util.function.Predicate<T> predicate)` Returns `true` if this option is nonempty and the predicate p returns `true` when applied to this Option's value.
`default Option<T>`	`filter(java.util.function.Predicate<T> predicate)` Returns this Option if it is nonempty and applying the predicate p to this Option's value returns `true`.
`default Option<T>`	`filterNot(java.util.function.Predicate<T> predicate)` Returns this Option if it is nonempty and applying the predicate p to this Option's value returns `false`.
`<R> Option<R>`	`flatMap(java.util.function.Function<T,Option<R>> function)` Returns an Option consisting of the result of applying the given function to the current `Some`.
`default boolean`	`forall(java.util.function.Predicate<T> predicate)` Returns `true` if the Option is nonempty and the predicate holds `true`, else `false`.
`T`	`get()` Returns this Option's value if such exists, else `NoSuchElementException` is raised.
`T`	`getOrElse(java.util.function.Supplier<T> supplier)` Returns this Option's value if such exists, else the value provided by the supplier.
`default boolean`	`isDefined()` Returns `true` if the option is an instance of `Some`, `false` otherwise.
`default boolean`	`isEmpty()` Returns `true` if the option is an instance of `None`, `false` otherwise
`Iterator<T>`	`iterator()` Returns the Option's value in an `Iterator` if it is nonempty, or an empty `Iterator` if it is empty.
`<R> Option<R>`	`map(java.util.function.Function<T,R> function)` Returns an Option consisting of the result of applying the given function to the current `Some`.
`static <T> Option<T>`	`None()` Returns an empty Option.
`static <T> Option<T>`	`ofOptional(Optional<T> optional)` Converts the `Optional` to a corresponding `Option`.
`Option<T>`	`orElse(java.util.function.Supplier<Option<T>> supplier)` Returns this Option if it is nonempty, otherwise return the result of provided by the supplier.
`default T`	`orNull()` Returns the Option's value if it is nonempty, or `null` if it is empty.
`java.util.stream.Stream<T>`	`stream()` Returns the Option's value in a Stream if it is nonempty, or an empty Stream if it is empty.
`<R> Either<T,R>`	`toLeft(java.util.function.Supplier<R> right)` Returns the value of this `Some` as a `Left`, or in case of `None` a `Right` containing the value from the provided supplier.
`<L> Either<L,T>`	`toRight(java.util.function.Supplier<L> left)` Returns the value of this `Some` as a `Right`, or in case of `None` a `Left` containing the value from the provided supplier.

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Field Detail
  - DEFAULT_NONE
```
static final None DEFAULT_NONE
```
    This is a singleton None since it anyways cannot represent a state.
    Can also be accessed using empty()
- Method Detail
  - apply
```
static <T> Option<T> apply(T value)
```
    Creates an instance of Option.
    If a null value is provided then None is returned, else Some containing the provided value.
    
    Type Parameters:
    
    T - The type for the value this Option represents
    
    Parameters:
    
    value - The value this Option shall represent
    
    Returns:
    
    The Option representing the provided value
    
    Since:
    
    1.0
  - empty
```
static <T> Option<T> empty()
```
    Returns an empty Option.
    In practice this returns a singleton as it anyways cannot represent a value/state.
    
    Type Parameters:
    
    T - The type for the value this Option represents
    
    Returns:
    
    The default None instance
    
    Since:
    
    1.0
  - None
```
static <T> Option<T> None()
```
    Returns an empty Option.
    This is the same as empty() but with the difference it provides a more Scala like feeling if the method is statically imported.
    One can use None() as if it was a apply method on a companion object in Scala.
    E.g.
    import static javascalautils.Option.None; Option<String> opt = None();
    Type Parameters:
    
    T - The type for the value this Option represents
    
    Returns:
    
    The default None instance
    
    Since:
    
    1.2
  - contains
```
default boolean contains(T other)
```
    Returns true if this is a Some containing the provided object, else false.
    
    Parameters:
    
    other - The other object to compare to
    
    Returns:
    
    If this Some contains the provided object
    
    Since:
    
    1.0
  - count
```
default int count()
```
    Returns the count which means 1 for nonempty Option's and 0 for empty.
    
    Returns:
    
    The count
    
    Since:
    
    1.0
  - exists
```
boolean exists(java.util.function.Predicate<T> predicate)
```
    Returns true if this option is nonempty and the predicate p returns true when applied to this Option's value.
    
    Parameters:
    
    predicate - The predicate
    
    Returns:
    
    If the predicate matches
    
    Since:
    
    1.0
  - filter
```
default Option<T> filter(java.util.function.Predicate<T> predicate)
```
    Returns this Option if it is nonempty and applying the predicate p to this Option's value returns true.
    
    Parameters:
    
    predicate - The predicate
    
    Returns:
    
    The Option representing the match
    
    Since:
    
    1.0
  - filterNot
```
default Option<T> filterNot(java.util.function.Predicate<T> predicate)
```
    Returns this Option if it is nonempty and applying the predicate p to this Option's value returns false.
    
    Parameters:
    
    predicate - The predicate
    
    Returns:
    
    The Option representing the match
    
    Since:
    
    1.0
  - forall
```
default boolean forall(java.util.function.Predicate<T> predicate)
```
    Returns true if the Option is nonempty and the predicate holds true, else false.
    As an Option is a zero-or-one sized collection this is in an essence exactly the same as exists(Predicate).
    
    Parameters:
    
    predicate - The predicate
    
    Returns:
    
    If the predicate matches
    
    Since:
    
    1.0
  - get
```
T get()
```
    Returns this Option's value if such exists, else NoSuchElementException is raised.
    
    Returns:
    
    The value of the Option
    
    Since:
    
    1.0
  - getOrElse
```
T getOrElse(java.util.function.Supplier<T> supplier)
```
    Returns this Option's value if such exists, else the value provided by the supplier.
    
    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
    
    Since:
    
    1.0
  - isDefined
```
default boolean isDefined()
```
    Returns true if the option is an instance of Some, false otherwise.
    
    Returns:
    
    true this Option is a Some, else false
    
    Since:
    
    1.0
  - isEmpty
```
default boolean isEmpty()
```
    Returns true if the option is an instance of None, false otherwise
    
    Returns:
    
    true this Option is a None, else false
    
    Since:
    
    1.0
  - iterator
```
Iterator<T> iterator()
```
    Returns the Option's value in an Iterator if it is nonempty, or an empty Iterator if it is empty.
    
    Specified by:
    
    iterator in interface Iterable<T>
    
    Returns:
    
    The iterator for the Option
    
    Since:
    
    1.0
  - map
```
<R> Option<R> map(java.util.function.Function<T,R> function)
```
    Returns an Option consisting of the result of applying the given function to the current Some.
    Applying map to None will always yield None.
    
    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
    
    Since:
    
    1.0
  - flatMap
```
<R> Option<R> flatMap(java.util.function.Function<T,Option<R>> function)
```
    Returns an Option consisting of the result of applying the given function to the current Some.
    Applying map to None will always yield None.
    
    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
    
    Since:
    
    1.2
  - orElse
```
Option<T> orElse(java.util.function.Supplier<Option<T>> supplier)
```
    Returns this Option if it is nonempty, otherwise return the result of provided by the supplier.
    
    Parameters:
    
    supplier - The supplier to use in case of None
    
    Returns:
    
    This Option or the one provided by the supplier
    
    Since:
    
    1.0
  - orNull
```
default T orNull()
```
    Returns the Option's value if it is nonempty, or null if it is empty.
    
    Returns:
    
    The value of the Option or null in case of None
    
    Since:
    
    1.0
  - stream
```
java.util.stream.Stream<T> stream()
```
    Returns the Option's value in a Stream if it is nonempty, or an empty Stream if it is empty.
    
    Returns:
    
    The stream for the Option
    
    Since:
    
    1.0
  - toLeft
```
<R> Either<T,R> toLeft(java.util.function.Supplier<R> right)
```
    Returns the value of this Some as a Left, or in case of None a Right containing the value from the provided supplier.
    
    Type Parameters:
    
    R - The type in case Right returned
    
    Parameters:
    
    right - The supplier to use in case this is a None
    
    Returns:
    
    The Either instance
    
    Since:
    
    1.4
  - toRight
```
<L> Either<L,T> toRight(java.util.function.Supplier<L> left)
```
    Returns the value of this Some as a Right, or in case of None a Left containing the value from the provided supplier.
    
    Type Parameters:
    
    L - The type in case Left returned
    
    Parameters:
    
    left - The supplier to use in case this is a None
    
    Returns:
    
    The Either instance
    
    Since:
    
    1.4
  - asOptional
```
default Optional<T> asOptional()
```
    Converts this Option to a corresponding Optional.
    
    Returns:
    
    The Optional instance
    
    Since:
    
    1.0
  - ofOptional
```
static <T> Option<T> ofOptional(Optional<T> optional)
```
    Converts the Optional to a corresponding Option.
    
    Type Parameters:
    
    T - The type for the value this Option represents
    
    Parameters:
    
    optional - The Optional to convert
    
    Returns:
    
    The Option for the provided Optional
    
    Since:
    
    1.0

Interface Option<T>

Field Summary

Method Summary

Methods inherited from interface java.lang.Iterable

Field Detail

DEFAULT_NONE

Method Detail

apply

empty

None

contains

count

exists

filter

filterNot

forall

get

getOrElse

isDefined

isEmpty

iterator

map

flatMap

orElse

orNull

stream

toLeft

toRight

asOptional

ofOptional