org.apache.druid.java.util.common

Class Either<L,R>

java.lang.Object

org.apache.druid.java.util.common.Either<L,R>

public class Either<L,R>
extends Object

Encapsulates either an "error" or a "value". Similar to the Either class in Scala or Haskell, except the possibilities are named "error" and "value" instead of "left" and "right".

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object o)
L	error() Returns the error object.
static <L,R> Either<L,R>	error(L error)
int	hashCode()
boolean	isError()
boolean	isValue()
<T> Either<L,T>	map(Function<R,T> fn) Applies a function to this value, if present.
String	toString()
static <L,R> Either<L,R>	value(R value)
R	valueOrThrow() If this Either represents a value, returns it.

Methods inherited from class java.lang.Object

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

Method Detail

error

public static <L,R> Either<L,R> error(L error)

value

public static <L,R> Either<L,R> value(@Nullable
                                      R value)

isValue

public boolean isValue()

isError

public boolean isError()

error

public L error()

Returns the error object.

Throws:

IllegalStateException - if this instance is not an error

valueOrThrow

@Nullable
public R valueOrThrow()

If this Either represents a value, returns it. If this Either represents an error, throw an error. If the error is a Throwable, it is wrapped in a RuntimeException and thrown. If it is not a throwable, a generic error is thrown containing the string representation of the error object. To retrieve the error as-is, use isError() and error() instead.

map

public <T> Either<L,T> map(Function<R,T> fn)

Applies a function to this value, if present. If the mapping function throws an exception, it is thrown by this method instead of being packed up into the returned Either. If this Either represents an error, the mapping function is not applied.

Throws:

NullPointerException - if the mapping function returns null

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object