Eithers (Functional Extensions Library 4.5.1 API)

java.lang.Object
- io.atlassian.fugue.Eithers

```
public class Eithers
extends Object
```
Utility functions for Eithers.

Since:

1.2

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static <L,R> Either<L,R>`	`cond(boolean predicate, L left, R right)` Creates an Either based on a boolean expression.
`static <L,R> Iterable<L>`	`filterLeft(Iterable<Either<L,R>> it)` Takes an `Iterable` of `eithers`, and collects the left values of every either which has a left value
`static <L,R> Iterable<R>`	`filterRight(Iterable<Either<L,R>> it)` Takes an `Iterable` of `eithers`, and collects the right values of every either which has a left value
`static <X extends Exception,A> A`	`getOrThrow(Either<X,A> either)` Simplifies extracting a value or throwing a checked exception from an Either.
`static <L,R> Predicate<Either<L,R>>`	`isLeft()` A predicate that tests if the supplied either is a left.
`static <L,R> Predicate<Either<L,R>>`	`isRight()` A predicate that tests if the supplied either is a right.
`static <L,R> Function<Either<L,R>,Option<L>>`	`leftMapper()` A function that maps an either to an option of its left type.
`static <T> T`	`merge(Either<T,T> either)` Extracts an object from an Either, regardless of the side in which it is stored, provided both sides contain the same type.
`static <L,R> Function<Either<L,R>,Option<R>>`	`rightMapper()` A function that maps an either to an option of its right type.
`static <L,R> Either<Iterable<L>,R>`	`sequenceLeft(Iterable<Either<L,R>> eithers)` Collect the left values if there are only lefts, otherwise return the first right encountered.
`static <L,R> Either<L,Iterable<R>>`	`sequenceRight(Iterable<Either<L,R>> eithers)` Collect the right values if there are only rights, otherwise return the first left encountered.
`static <L,R> Function<L,Either<L,R>>`	`toLeft()` Function to convert from an value to a `Either.Left` containing that value.
`static <L,R> Function<L,Either<L,R>>`	`toLeft(Class<L> leftType, Class<R> rightType)` Function to convert from a value to a `Either.Left` containing that value.
`static <L,R> Supplier<Either<L,R>>`	`toLeft(L l)` Supplier returning a `Either.Left`.
`static <L,R> Supplier<Either<L,R>>`	`toLeft(L l, Class<R> rightType)` Supplier returning a `Either.Left`.
`static <L,R> Function<R,Either<L,R>>`	`toRight()` Function to convert from an value to a `Either.Right`.
`static <L,R> Function<R,Either<L,R>>`	`toRight(Class<L> leftType, Class<R> rightType)` Function to convert from a value to a `Either.Right` containing that value.
`static <L,R> Supplier<Either<L,R>>`	`toRight(Class<L> leftType, R r)` Supplier returning a `Either.Right`.
`static <L,R> Supplier<Either<L,R>>`	`toRight(R r)` Supplier returning a `Either.Right`.
`static <LL,L extends LL,R> Either<LL,R>`	`upcastLeft(Either<L,R> e)` Upcasts an `either` of left type L to an either of left type LL, which is a super type of L, keeping the right type unchanged.
`static <L,RR,R extends RR> Either<L,RR>`	`upcastRight(Either<L,R> e)` Upcasts an `either` of right type R to an either of right type RR, which is a super type of R, keeping the left type unchanged.

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

- Method Detail
  - merge
```
public static <T> T merge(Either<T,T> either)
```
    Extracts an object from an Either, regardless of the side in which it is stored, provided both sides contain the same type. This method will never return null.
    
    Type Parameters:
    
    T - the type for both the LHS and the RHS
    
    Parameters:
    
    either - use whichever side holds the value to return
    
    Returns:
    
    the value from whichever side holds it
  - cond
```
public static <L,R> Either<L,R> cond(boolean predicate,
                                     L left,
                                     R right)
```
    Creates an Either based on a boolean expression. If predicate is true, a Right will be returned containing the supplied right value; if it is false, a Left will be returned containing the supplied left value.
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Parameters:
    
    predicate - if predicate is true, a Right will be returned if it is false, a Left will be returned containing the supplied left value.
    
    left - the LHS value
    
    right - the RHS value
    
    Returns:
    
    an either with the appropriately selected value
  - getOrThrow
```
public static <X extends Exception,A> A getOrThrow(Either<X,A> either)
                                            throws X extends Exception
```
    Simplifies extracting a value or throwing a checked exception from an Either.
    
    Type Parameters:
    
    A - the value type
    
    X - the exception type
    
    Parameters:
    
    either - to extract from
    
    Returns:
    
    the value from the RHS
    
    Throws:
    
    X - the exception on the LHS
    
    X extends Exception
  - isLeft
```
public static <L,R> Predicate<Either<L,R>> isLeft()
```
    A predicate that tests if the supplied either is a left.
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Returns:
    
    the predicate testing left-hand-sidedness
  - isRight
```
public static <L,R> Predicate<Either<L,R>> isRight()
```
    A predicate that tests if the supplied either is a right.
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Returns:
    
    the predicate testing right-hand-sidedness
  - leftMapper
```
public static <L,R> Function<Either<L,R>,Option<L>> leftMapper()
```
    A function that maps an either to an option of its left type. The Function will return a defined Option containing the either's left value if {Either#isLeft()} is true, an undefined Option otherwise.
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Returns:
    
    the function returning a defined option for left-hand-sided eithers
  - rightMapper
```
public static <L,R> Function<Either<L,R>,Option<R>> rightMapper()
```
    A function that maps an either to an option of its right type. The Function will return a defined Option containing the either's right value if {Either#isRight()} is true, an undefined Option otherwise.
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Returns:
    
    the function returning a defined option for right-hand-sided eithers
  - toLeft
```
public static <L,R> Function<L,Either<L,R>> toLeft()
```
    Function to convert from an value to a Either.Left containing that value.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Returns:
    
    a Function returning a Either.Left.
  - toLeft
```
public static <L,R> Function<L,Either<L,R>> toLeft(Class<L> leftType,
                                                   Class<R> rightType)
```
    Function to convert from a value to a Either.Left containing that value. Allows hinting the correct types.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Parameters:
    
    leftType - expected left type.
    
    rightType - expected right type.
    
    Returns:
    
    a Function returning a Either.Left.
  - toLeft
```
public static <L,R> Supplier<Either<L,R>> toLeft(L l)
```
    Supplier returning a Either.Left.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Parameters:
    
    l - value to return inside the left.
    
    Returns:
    
    a Supplier returning a Either.Left..
  - toLeft
```
public static <L,R> Supplier<Either<L,R>> toLeft(L l,
                                                 Class<R> rightType)
```
    Supplier returning a Either.Left. Allows hinting the correct right type.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Parameters:
    
    l - value to return inside the left.
    
    rightType - type hint for the right type of the either.
    
    Returns:
    
    a Supplier returning a Either.Left.
  - toRight
```
public static <L,R> Function<R,Either<L,R>> toRight()
```
    Function to convert from an value to a Either.Right. Allows hinting the correct types.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Returns:
    
    a Function returning a Either.Right.
  - toRight
```
public static <L,R> Function<R,Either<L,R>> toRight(Class<L> leftType,
                                                    Class<R> rightType)
```
    Function to convert from a value to a Either.Right containing that value. Allows hinting the correct types.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Parameters:
    
    leftType - expected left type.
    
    rightType - expected right type.
    
    Returns:
    
    a Function returning a Either.Right.
  - toRight
```
public static <L,R> Supplier<Either<L,R>> toRight(R r)
```
    Supplier returning a Either.Right.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Parameters:
    
    r - value to return inside the right.
    
    Returns:
    
    a Supplier returning a Either.Right..
  - toRight
```
public static <L,R> Supplier<Either<L,R>> toRight(Class<L> leftType,
                                                  R r)
```
    Supplier returning a Either.Right. Allows hinting the correct right type.
    
    Type Parameters:
    
    L - left type.
    
    R - right type.
    
    Parameters:
    
    r - value to return inside the right.
    
    leftType - type hint for the left type of the either.
    
    Returns:
    
    a Supplier returning a Either.Right.
  - upcastLeft
```
public static <LL,L extends LL,R> Either<LL,R> upcastLeft(Either<L,R> e)
```
    Upcasts an either of left type L to an either of left type LL, which is a super type of L, keeping the right type unchanged.
    
    Type Parameters:
    
    L - the base type to upcast
    
    LL - the super type of the contained left type
    
    R - the contained right type
    
    Parameters:
    
    e - the source either
    
    Returns:
    
    an either of left type LL and right type R
    
    Since:
    
    2.0
  - upcastRight
```
public static <L,RR,R extends RR> Either<L,RR> upcastRight(Either<L,R> e)
```
    Upcasts an either of right type R to an either of right type RR, which is a super type of R, keeping the left type unchanged.
    
    Type Parameters:
    
    L - the contained left type
    
    R - the base type to upcast
    
    RR - the super type of the contained right type
    
    Parameters:
    
    e - the source either
    
    Returns:
    
    an either of left type L and right type RR
    
    Since:
    
    2.0
  - filterLeft
```
public static <L,R> Iterable<L> filterLeft(Iterable<Either<L,R>> it)
```
    Takes an Iterable of eithers, and collects the left values of every either which has a left value
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Parameters:
    
    it - iterable of eithers to filter and transform from
    
    Returns:
    
    the left values contained in the contents of it
  - filterRight
```
public static <L,R> Iterable<R> filterRight(Iterable<Either<L,R>> it)
```
    Takes an Iterable of eithers, and collects the right values of every either which has a left value
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Parameters:
    
    it - iterable of eithers to filter and transform from
    
    Returns:
    
    the right values contained in the contents of it
  - sequenceRight
```
public static <L,R> Either<L,Iterable<R>> sequenceRight(Iterable<Either<L,R>> eithers)
```
    Collect the right values if there are only rights, otherwise return the first left encountered.
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Parameters:
    
    eithers - an Iterable of either values
    
    Returns:
    
    either the iterable of right values, or the first left encountered.
  - sequenceLeft
```
public static <L,R> Either<Iterable<L>,R> sequenceLeft(Iterable<Either<L,R>> eithers)
```
    Collect the left values if there are only lefts, otherwise return the first right encountered.
    
    Type Parameters:
    
    L - the LHS type
    
    R - the RHS type
    
    Parameters:
    
    eithers - an Iterable of either values
    
    Returns:
    
    either the iterable of left values, or the first right encountered.

Class Eithers

Method Summary

Methods inherited from class java.lang.Object

Method Detail

merge

cond

getOrThrow

isLeft

isRight

leftMapper

rightMapper

toLeft

toLeft

toLeft

toLeft

toRight

toRight

toRight

toRight

upcastLeft

upcastRight

filterLeft

filterRight

sequenceRight

sequenceLeft