de.larssh.utils

Class Either<A,B>

java.lang.Object

de.larssh.utils.Either<A,B>

Type Parameters:

A - first type of value

B - second type of value

public class Either<A,B>
extends Object

A container object which contains a value matching either one or another type represented by <A> and <B>.

The value can be accessed in a type-safe way using getFirst() and getSecond().

Additional methods to process the value based on its type and resulting in a fixed typed instance are provided, such as map(Function, Function).

This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of Optional may have unpredictable results and should be avoided.

Constructor Summary

Constructors

Constructor and Description
Either(Optional<A> first, Optional<B> second) Creates a new Either instance.

Method Summary

Modifier and Type	Method and Description
protected boolean	canEqual(Object other)
boolean	equals(Object o)
Optional<A>	getFirst() Value of first type
Optional<B>	getSecond() Value of second type
int	hashCode()
void	ifFirstIsPresent(Consumer<? super A> consumer) If the first value is present, invoke the specified consumer with the value, otherwise do nothing.
void	ifPresent(Consumer<? super A> firstConsumer, Consumer<? super B> secondConsumer) Invoke either consumer depending on which value is present..
void	ifSecondIsPresent(Consumer<? super B> consumer) If the second value is present, invoke the specified consumer with the value, otherwise do nothing.
<T> T	map(Function<? super A,? extends T> firstFunction, Function<? super B,? extends T> secondFunction) If value is of first type functionA is applied, else value is of second type and functionB is applied.
B	mapFirst(Function<? super A,? extends B> function) If the value is of second type function is applied and the resulting value is returned else the value is of first type and returned as-is.
A	mapSecond(Function<? super B,? extends A> function) If the value is of first type function is applied and the resulting value is returned else the value is of second type and returned as-is.
static <A,B> Either<A,B>	of(A first, B second) Deprecated. This is a convenience method for special cases only. Use ofFirst(A) and ofSecond(B) where possible.
static <A,B> Either<A,B>	ofFirst(A value) Returns an Either object describing the given value of the first type.
static <A,B> Either<A,B>	ofSecond(B value) Returns an Either object describing the given value of the second type.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Either

public Either(Optional<A> first,
              Optional<B> second)

Creates a new Either instance.

Parameters:

first - Value of first type

second - Value of second type

Method Detail

of

@Deprecated
public static <A,B> Either<A,B> of(@Nullable
                                               A first,
                                               @Nullable
                                               B second)

Deprecated. This is a convenience method for special cases only. Use ofFirst(A) and ofSecond(B) where possible.

Returns an Either object describing the given value. One of both parameters has to be non null (means being set), the other one has to be null (means being not set).

Type Parameters:

A - type of first value

B - type of second value

Parameters:

first - value of first type or null

second - value of second type or null

Returns:

an Either object with the given value

Throws:

NullPointerException - if both parameters are null

IllegalArgumentException - if both parameters are non-null

ofFirst

public static <A,B> Either<A,B> ofFirst(A value)

Returns an Either object describing the given value of the first type.

Type Parameters:

A - first type of value

B - second type of value

Parameters:

value - value to describe

Returns:

an Either object describing the given value

ofSecond

public static <A,B> Either<A,B> ofSecond(B value)

Returns an Either object describing the given value of the second type.

Type Parameters:

A - first type of value

B - second type of value

Parameters:

value - value to describe

Returns:

an Either object describing the given value

ifPresent

public void ifPresent(Consumer<? super A> firstConsumer,
                      Consumer<? super B> secondConsumer)

Invoke either consumer depending on which value is present..

Parameters:

firstConsumer - block to be executed if the first value is present

secondConsumer - block to be executed if the second value is present

ifFirstIsPresent

public void ifFirstIsPresent(Consumer<? super A> consumer)

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

Parameters:

consumer - block to be executed if the first value is present

ifSecondIsPresent

public void ifSecondIsPresent(Consumer<? super B> consumer)

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

Parameters:

consumer - block to be executed if the second value is present

map

@Nullable
public <T> T map(Function<? super A,? extends T> firstFunction,
                           Function<? super B,? extends T> secondFunction)

If value is of first type functionA is applied, else value is of second type and functionB is applied. The resulting value is returned.

Example: The first type is somehow used for user input, while the second one is used for system default values.

 Either<String, Number> either = Either.ofFirst("123");

 String text = either.map(s -> "Changed", n -> "System default");
 long value = either.map(Long::parseLong, Number::longValue);
 

Type Parameters:

T - resulting type

Parameters:

firstFunction - function to map value, if it is of first type

secondFunction - function to map value, if it is of second type

Returns:

result after mapping the value using either functionA or functionB

mapFirst

@Nullable
public B mapFirst(Function<? super A,? extends B> function)

If the value is of second type function is applied and the resulting value is returned else the value is of first type and returned as-is.

Example: The first type is somehow used for user input, while the second one is used for system default values.

 Either<String, Number> either = Either.ofFirst("123");

 String text = either.map(s -> "Changed", n -> "System default");
 Number value = either.mapFirst(Long::parseLong);
 

Parameters:

function - function to map value, if it is of first type

Returns:

value if it is of second type, else result after mapping it using function

mapSecond

@Nullable
public A mapSecond(Function<? super B,? extends A> function)

If the value is of first type function is applied and the resulting value is returned else the value is of second type and returned as-is.

Example: The first type is somehow used for user input, while the second one is used for system default values.

 Either<String, Number> either = Either.ofFirst(123);

 String text = either.map(s -> "Changed", n -> "System default");
 String displayValue = either.mapSecond(Number::toString);
 

Parameters:

function - function to map value, if it is of second type

Returns:

value if it is of first type, else result after mapping it using function

getFirst

public Optional<A> getFirst()

Value of first type

Returns:

value of first type

getSecond

public Optional<B> getSecond()

Value of second type

Returns:

value of second type

toString

@NonNull
public String toString()

Overrides:

toString in class Object

equals

public boolean equals(@Nullable
                      Object o)

Overrides:

equals in class Object

canEqual

protected boolean canEqual(@Nullable
                           Object other)

hashCode

public int hashCode()

Overrides:

hashCode in class Object