Package nl.markv.result

Class Err<T,E>

java.lang.Object

nl.markv.result.Err<T,E>

All Implemented Interfaces:

Iterable<T>, Result<T,E>

public final class Err<T,E>
extends Object
implements Result<T,E>

Method Summary

Modifier and Type	Method	Description
<F> Result<T,F>	adaptErr()	If this result is Ok, change the generic type for Err.
<U> Result<U,E>	adaptOk()	If this result is Err, change the generic type for Ok.
<U> Result<U,E>	and(java.util.function.Supplier<Result<U,E>> nextSupplier)	Returns the current Result if it is Err, and produces the next result (given by the argument) otherwise.
<U> Result<U,E>	and(Result<U,E> next)	Returns the current Result if it is Err, and the next one otherwise.
<R> R	branch(java.util.function.Function<T,R> okConverter, java.util.function.Function<E,R> errConverter)	Call on of the functions, depending on Ok or Err.
boolean	contains(T ok)	Whether this Result is an Ok that contains an object equal to the argument.
boolean	containsErr(E err)	Whether this Result is an Err that contains an object equal to the argument.
static <T> Err<T,None>	empty()	Create a failed Result where the Err type is None.
boolean	equals(Object other)
boolean	errMatches(java.util.function.Predicate<E> errPredicate)	If this Result is Err, the predicate will be tested against its content.
E	errOr(E alternative)	Like Result.errOrNullable(E), but does not allow null input or output.
E	errOr(java.util.function.Supplier<E> alternativeSupplier)	Like Result.errOrNullable(Supplier), but does not allow null input or output.
E	errOrNull()
E	errOrNullable(E alternative)	If this Result is Err, return the value.
E	errOrNullable(java.util.function.Supplier<E> alternativeSupplier)	If this Result is Err, return the value.
<U> Result<U,E>	flatMap(java.util.function.Function<T,Result<U,E>> converter)	Map the Ok value to a new Result value, flattening the two results to a single one.
<F> Result<T,F>	flatMapErr(java.util.function.Function<E,Result<T,F>> converter)	Map the Err value to a new Result value, flattening the two results to a single one.
E	get()	Returns the value contained by this Ok.
E	getErrOrThrow()	If the Result is Err, return its content.
E	getErrOrThrow(String exceptionMessage)	If the Result is Err, return its content, otherwise throw WrongResultVariantException with the given message.
E	getErrOrThrow(java.util.function.Supplier<RuntimeException> exceptionSupplier)	If the Result is Err, return its content, otherwise throw the given exception.
T	getOrThrow()	Deprecated. Marked as deprecated because calling getOrThrow() on Err always fails.
T	getOrThrow(String exceptionMessage)	Deprecated. Marked as deprecated because calling getOrThrow(String) on Err always fails.
T	getOrThrow(java.util.function.Supplier<RuntimeException> exceptionSupplier)	Deprecated. Marked as deprecated because calling getOrThrow(Supplier) on Err always fails.
Object	getUnified()	Get the content of the result, whether it is inside Ok or Err.
int	hashCode()
void	ifEither(java.util.function.Consumer<T> okAction, java.util.function.Consumer<E> errAction)	Call the action for either Ok or Err.
void	ifErr(java.util.function.Consumer<E> action)	Run an action on the value of Err.
void	ifOk(java.util.function.Consumer<T> action)	Run an action on the value of Ok.
boolean	isOk()	Whether the Result is Ok.
Iterator<T>	iterator()	Returns an iterator containing no values, since this result is not Ok.
<U> Result<U,E>	map(java.util.function.Function<T,U> converter)	Map the Ok value to a new value of a different type.
<F> Result<T,F>	mapErr(java.util.function.Function<E,F> converter)	Map the Err value to a new value of a different type.
boolean	matches(java.util.function.Predicate<T> okPredicate)	If this Result is Ok, the predicate will be tested against its content.
static <T, E> Err<T,E>	of(E value)	Create a new, unsuccessful Result.
T	okOr(java.util.function.Supplier<T> alternativeSupplier)	Like Result.okOrNullable(Supplier), but does not allow null input or output.
T	okOr(T alternative)	Like Result.okOrNullable(T), but does not allow null input or output.
T	okOrNull()
T	okOrNullable(java.util.function.Supplier<T> alternativeSupplier)	If this Result is Ok, return the value.
T	okOrNullable(T alternative)	If this Result is Ok, return the value.
<F> Result<T,F>	or(java.util.function.Supplier<Result<T,F>> nextSupplier)	Returns the current Result if it is Ok, and produces the next result (given by the argument) otherwise.
<F> Result<T,F>	or(Result<T,F> next)	Returns the current Result if it is Ok, and the next one otherwise.
T	recover(java.util.function.Function<E,T> errToOkConverter)	If this Result is Ok, return the value.
java.util.stream.Stream<T>	stream()	Returns a stream containing no values, since this result is not Ok.
String	toString()
Optional<T>	withoutErr()	Drop the Err value, replacing Err by Optional.empty() and replacing Ok by Optional.of(Object).
Optional<E>	withoutOk()	Drop the Ok value, replacing Err by Optional.of(Object) and replacing Ok by Optional.empty().

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface nl.markv.result.Result

isErr

Method Details

of

@Nonnull
public static <T,
E> Err<T,E> of(@Nonnull
 E value)

Create a new, unsuccessful Result. Same as Result.err(Object).

empty

@Nonnull
public static <T> Err<T,None> empty()

Create a failed Result where the Err type is None. This is very similar to Optional, which may be preferable.

isOk

public boolean isOk()

Whether the Result is Ok.

Specified by:

isOk in interface Result<T,E>

get

@Nonnull
public E get()

Returns the value contained by this Ok. Since this can only be called ok Ok and not on Result, this is safe - it will always return a non-null result without throwing.

getOrThrow

@Deprecated
@Nonnull
public T getOrThrow()

Deprecated.

Marked as deprecated because calling getOrThrow() on Err always fails. It is not deprecated to call this on Result, but on Err use get().

If the Result is Ok, return its content. Otherwise, throw WrongResultVariantException.

Note that it may be better to get the okay value without chance of exceptions:

 if (result instanceof Ok<List<Integer>, String> ok) {
     var value = ok.get();
 }
 

Specified by:

getOrThrow in interface Result<T,E>

See Also:

• Result.getErrOrThrow()
• Result.getOrThrow(String)
• Result.getOrThrow(Supplier)

getOrThrow

@Deprecated
@Nonnull
public T getOrThrow(@Nonnull
 String exceptionMessage)

Deprecated.

Marked as deprecated because calling getOrThrow(String) on Err always fails. It is not deprecated to call this on Result, but on Err use get().

If the Result is Ok, return its content, otherwise throw WrongResultVariantException with the given message.

Specified by:

getOrThrow in interface Result<T,E>

See Also:

• Result.getOrThrow()
• Result.getOrThrow(Supplier)
• Result.getErrOrThrow()

getOrThrow

@Deprecated
@Nonnull
public T getOrThrow(@Nonnull
 java.util.function.Supplier<RuntimeException> exceptionSupplier)

Deprecated.

Marked as deprecated because calling getOrThrow(Supplier) on Err always fails. It is not deprecated to call this on Result, but on Err use get().

If the Result is Ok, return its content, otherwise throw the given exception.

Specified by:

getOrThrow in interface Result<T,E>

See Also:

• Result.getOrThrow()
• Result.getOrThrow(String)
• Result.getErrOrThrow()

getErrOrThrow

@Nonnull
public E getErrOrThrow()

If the Result is Err, return its content. Otherwise, throw WrongResultVariantException.

This is the dual of Result.getOrThrow(), which describes more details.

Specified by:

getErrOrThrow in interface Result<T,E>

See Also:

• Result.getOrThrow()
• Result.getErrOrThrow(String)
• Result.getErrOrThrow(Supplier)

getErrOrThrow

@Nonnull
public E getErrOrThrow(@Nonnull
 String exceptionMessage)

If the Result is Err, return its content, otherwise throw WrongResultVariantException with the given message.

Specified by:

getErrOrThrow in interface Result<T,E>

See Also:

• Result.getOrThrow()
• Result.getErrOrThrow()
• Result.getErrOrThrow(Supplier)

getErrOrThrow

@Nonnull
public E getErrOrThrow(@Nonnull
 java.util.function.Supplier<RuntimeException> exceptionSupplier)

If the Result is Err, return its content, otherwise throw the given exception.

Specified by:

getErrOrThrow in interface Result<T,E>

See Also:

• Result.getOrThrow()
• Result.getErrOrThrow()
• Result.getErrOrThrow(String)

map

@Nonnull
public <U> Result<U,E> map(@Nonnull
 java.util.function.Function<T,U> converter)

Map the Ok value to a new value of a different type. Does nothing on Err.

Specified by:

map in interface Result<T,E>

See Also:

• Result.mapErr(Function)
• Result.branch(Function, Function)
• Stream.map(Function)

flatMap

@Nonnull
public <U> Result<U,E> flatMap(@Nonnull
 java.util.function.Function<T,Result<U,E>> converter)

Map the Ok value to a new Result value, flattening the two results to a single one. Does nothing on Err.

Specified by:

flatMap in interface Result<T,E>

See Also:

• Result.map(Function)
• Result.flatMapErr(Function)
• Result.flatten(Result)
• Stream.flatMap(Function)

mapErr

@Nonnull
public <F> Result<T,F> mapErr(@Nonnull
 java.util.function.Function<E,F> converter)

Map the Err value to a new value of a different type. Does nothing on Ok.

Specified by:

mapErr in interface Result<T,E>

See Also:

• Result.map(Function)
• Result.branch(Function, Function)
• Stream.map(Function)

flatMapErr

@Nonnull
public <F> Result<T,F> flatMapErr(@Nonnull
 java.util.function.Function<E,Result<T,F>> converter)

Map the Err value to a new Result value, flattening the two results to a single one. Does nothing on Ok.

Specified by:

flatMapErr in interface Result<T,E>

See Also:

• Result.mapErr(Function)
• Result.flatMap(Function)
• Result.flatten(Result)
• Stream.flatMap(Function)

ifOk

public void ifOk(@Nonnull
 java.util.function.Consumer<T> action)

Run an action on the value of Ok. Does nothing on Err.

If the action is a transformation, Result.map(Function) should be preferred, which can take lambdas without side effects.

Specified by:

ifOk in interface Result<T,E>

See Also:

• Result.map(Function)
• Result.ifErr(Consumer)
• Result.ifEither(Consumer, Consumer)
• Optional.ifPresent(Consumer)

ifErr

public void ifErr(@Nonnull
 java.util.function.Consumer<E> action)

Run an action on the value of Err. Does nothing on Ok.

If the action is a transformation, Result.mapErr(Function) should be preferred, which can take lambdas without side effects.

Specified by:

ifErr in interface Result<T,E>

See Also:

• Result.mapErr(Function)
• Result.ifOk(Consumer)
• Result.ifEither(Consumer, Consumer)

ifEither

public void ifEither(@Nonnull
 java.util.function.Consumer<T> okAction,
 @Nonnull
 java.util.function.Consumer<E> errAction)

Call the action for either Ok or Err.

Specified by:

ifEither in interface Result<T,E>

See Also:

• Result.ifOk(Consumer)
• Result.ifErr(Consumer)

branch

@Nonnull
public <R> R branch(@Nonnull
 java.util.function.Function<T,R> okConverter,
 @Nonnull
 java.util.function.Function<E,R> errConverter)

Call on of the functions, depending on Ok or Err. Both should return the same type.

If the functions return nothing, use Result.ifEither(Consumer, Consumer) instead.

Also called: fold

Specified by:

branch in interface Result<T,E>

See Also:

• Result.ifEither(Consumer, Consumer)
• Result.map(Function)
• Result.mapErr(Function)
• Result.recover(Function)

recover

@Nonnull
public T recover(@Nonnull
 java.util.function.Function<E,T> errToOkConverter)

If this Result is Ok, return the value. If it is not, then map the error to something of the same type as Result, and return that.

If the content of Err is not needed to produce an alternative value, use Result.okOr(Supplier) instead.

Also called: recover

Specified by:

recover in interface Result<T,E>

Parameters:

errToOkConverter - Function that takes the type of Err and returns the type of Ok.

See Also:

• Result.map(Function)
• Result.mapErr(Function)
• Result.branch(Function, Function)
• Result.okOr(Supplier)

okOr

@Nonnull
public T okOr(@Nonnull
 T alternative)

Like Result.okOrNullable(T), but does not allow null input or output.

Specified by:

okOr in interface Result<T,E>

okOr

@Nonnull
public T okOr(@Nonnull
 java.util.function.Supplier<T> alternativeSupplier)

Like Result.okOrNullable(Supplier), but does not allow null input or output.

Specified by:

okOr in interface Result<T,E>

okOrNullable

@Nullable
public T okOrNullable(@Nullable
 T alternative)

If this Result is Ok, return the value. If it is not, return the given alternative.

If the result is heavy to compute, use Result.okOr(Supplier) or Result.recover(Function) instead.

Specified by:

okOrNullable in interface Result<T,E>

Parameters:

alternative - The value that will replace Err.

See Also:

• Result.okOr(Supplier)
• Result.recover(Function)
• Result.errOr(E)

okOrNullable

@Nullable
public T okOrNullable(@Nonnull
 java.util.function.Supplier<T> alternativeSupplier)

If this Result is Ok, return the value. If it is not, produce an alternative using the given supplier.

Specified by:

okOrNullable in interface Result<T,E>

Parameters:

alternativeSupplier - A function that will produce a value to replace Err. Will only be invoked if Err, and only once.

See Also:

• Result.okOr(T)
• Result.recover(Function)
• Result.errOr(E)

okOrNull

@Nullable
public T okOrNull()

Specified by:

okOrNull in interface Result<T,E>

errOr

@Nonnull
public E errOr(@Nonnull
 E alternative)

Like Result.errOrNullable(E), but does not allow null input or output.

Specified by:

errOr in interface Result<T,E>

errOr

@Nonnull
public E errOr(@Nonnull
 java.util.function.Supplier<E> alternativeSupplier)

Like Result.errOrNullable(Supplier), but does not allow null input or output.

Specified by:

errOr in interface Result<T,E>

errOrNullable

@Nonnull
public E errOrNullable(@Nullable
 E alternative)

If this Result is Err, return the value. If it is not, return the given alternative.

If the result is heavy to compute, use Result.errOrNullable(Supplier) instead.

Specified by:

errOrNullable in interface Result<T,E>

Parameters:

alternative - The value that will replace Ok.

See Also:

• Result.errOr(Supplier)
• Result.okOr(T)

errOrNullable

@Nonnull
public E errOrNullable(@Nonnull
 java.util.function.Supplier<E> alternativeSupplier)

If this Result is Err, return the value. If it is not, produce an alternative using the given supplier.

Specified by:

errOrNullable in interface Result<T,E>

Parameters:

alternativeSupplier - A function that will produce a value to replace Ok. Will only be invoked if Ok, and only once.

See Also:

• Result.errOr(E)
• Result.okOr(T)

errOrNull

@Nonnull
public E errOrNull()

Specified by:

errOrNull in interface Result<T,E>

adaptOk

@Nonnull
public <U> Result<U,E> adaptOk()

If this result is Err, change the generic type for Ok.

Specified by:

adaptOk in interface Result<T,E>

See Also:

• Result.adaptErr()
• Result.map(Function)

adaptErr

@Nonnull
public <F> Result<T,F> adaptErr()

If this result is Ok, change the generic type for Err.

Specified by:

adaptErr in interface Result<T,E>

See Also:

• Result.adaptOk()
• Result.mapErr(Function)

withoutErr

@Nonnull
public Optional<T> withoutErr()

Drop the Err value, replacing Err by Optional.empty() and replacing Ok by Optional.of(Object).

Specified by:

withoutErr in interface Result<T,E>

withoutOk

@Nonnull
public Optional<E> withoutOk()

Drop the Ok value, replacing Err by Optional.of(Object) and replacing Ok by Optional.empty().

Specified by:

withoutOk in interface Result<T,E>

and

@Nonnull
public <U> Result<U,E> and(@Nonnull
 Result<U,E> next)

Returns the current Result if it is Err, and the next one otherwise.

See Result.and(Supplier) for more details.

Specified by:

and in interface Result<T,E>

See Also:

• Result.and(Supplier)
• Result.or(Result)

and

@Nonnull
public <U> Result<U,E> and(@Nonnull
 java.util.function.Supplier<Result<U,E>> nextSupplier)

Returns the current Result if it is Err, and produces the next result (given by the argument) otherwise.

This simulates '&&' in the sense that the result is Ok if and only if both inputs are Ok.

This returns the last object that had to be evaluated, like 'and' in Python. I.e. if the current Result is Err, the result must be Err, and the supplier is not called.

Specified by:

and in interface Result<T,E>

Parameters:

nextSupplier - Method that supplies the next Result. Only called (once) if current Result is Ok.

See Also:

• Result.and(Result)
• Result.or(Supplier)

or

@Nonnull
public <F> Result<T,F> or(@Nonnull
 Result<T,F> next)

Returns the current Result if it is Ok, and the next one otherwise.

See Result.or(Supplier) for more details.

Specified by:

or in interface Result<T,E>

See Also:

• Result.and(Supplier)
• Result.or(Result)

or

@Nonnull
public <F> Result<T,F> or(@Nonnull
 java.util.function.Supplier<Result<T,F>> nextSupplier)

Returns the current Result if it is Ok, and produces the next result (given by the argument) otherwise.

This simulates '||' in the sense that the result is Ok if at least one of the inputs is Ok.

This returns the last object that had to be evaluated, like 'and' in Python. I.e. if the current Result is Ok, the result must be Ok, and the supplier is not called.

Specified by:

or in interface Result<T,E>

Parameters:

nextSupplier - Method that supplies the next Result. Only called (once) if current Result is Err.

See Also:

• Result.and(Supplier)
• Result.or(Result)

contains

public boolean contains(@Nullable
 T ok)

Whether this Result is an Ok that contains an object equal to the argument.

Specified by:

contains in interface Result<T,E>

Parameters:

ok - The object that will be compared against Ok using Object.equals(Object). The comparison will only be done if this Result is Ok.

See Also:

• Result.containsErr(E)
• Result.matches(Predicate)

containsErr

public boolean containsErr(@Nullable
 E err)

Whether this Result is an Err that contains an object equal to the argument.

Specified by:

containsErr in interface Result<T,E>

Parameters:

err - The object that will be compared against Err using Object.equals(Object). The comparison will only be done if this Result is Err.

See Also:

• Result.contains(T)
• Result.errMatches(Predicate)

matches

public boolean matches(@Nonnull
 java.util.function.Predicate<T> okPredicate)

If this Result is Ok, the predicate will be tested against its content. If this is an Err, returns false without invoking the predicate.

Specified by:

matches in interface Result<T,E>

See Also:

• Result.contains(T)
• Result.errMatches(Predicate)

errMatches

public boolean errMatches(@Nonnull
 java.util.function.Predicate<E> errPredicate)

If this Result is Err, the predicate will be tested against its content. If this is an Ok, returns false without invoking the predicate.

Specified by:

errMatches in interface Result<T,E>

See Also:

• Result.containsErr(E)
• Result.matches(Predicate)

getUnified

@Nonnull
public Object getUnified()

Get the content of the result, whether it is inside Ok or Err.

Since success and failure types are generally different, type information is lost.

Specified by:

getUnified in interface Result<T,E>

equals

public boolean equals(@Nullable
 Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

@Nonnull
public String toString()

Overrides:

toString in class Object

iterator

@Nonnull
public Iterator<T> iterator()

Returns an iterator containing no values, since this result is not Ok.

Specified by:

iterator in interface Iterable<T>

stream

@Nonnull
public java.util.stream.Stream<T> stream()

Returns a stream containing no values, since this result is not Ok.

Specified by:

stream in interface Result<T,E>

See Also:

• ResultCollector
• Iterable.iterator()