Package com.apple.foundationdb.record.query.plan.temp

Class IterableHelpers

java.lang.Object

com.apple.foundationdb.record.query.plan.temp.IterableHelpers

@API(EXPERIMENTAL)
public class IterableHelpers
extends Object

Helper methods for Iterables.

Method Summary

Modifier and Type	Method	Description
static <T,R> Iterable<R>	flatMap(Iterable<T> source, Function<? super T,? extends Iterable<R>> mapper)	Flat-maps given function to the given iterable and returns a new iterable.
static <T,R> Iterable<R>	map(Iterable<T> source, Function<? super T,R> mapper)	Maps given function to the given iterable and returns a new iterable.
static <T> Iterable<T>	orElse(Iterable<T> source, Iterable<T> otherIterable)	Returns an alternative iterable if the given source iterable is empty.
static <T> Iterable<T>	orElseOf(Iterable<T> source, T value)	Returns an alternative singleton iterable if the given source iterable is empty.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

flatMap

public static <T,R> Iterable<R> flatMap(@Nonnull
                                              Iterable<T> source,
                                              @Nonnull
                                              Function<? super T,? extends Iterable<R>> mapper)

Flat-maps given function to the given iterable and returns a new iterable. This is akin to compositions based on Stream, however, allows for restarting the iteration as per general contract in Iterable.

Type Parameters:

T - type of source iterable

R - type the given mapper function returns iterables of

Parameters:

source - source iterable

mapper - mapper function to map from T to Iterable of R

Returns:

an iterable of type R that is the conceptual flat map of source using mapper

map

public static <T,R> Iterable<R> map(@Nonnull
                                          Iterable<T> source,
                                          @Nonnull
                                          Function<? super T,R> mapper)

Maps given function to the given iterable and returns a new iterable. This is akin to compositions based on Stream, however, allows for restarting the iteration as per general contract in Iterable.

Type Parameters:

T - type of source iterable

R - type the given mapper function returns

Parameters:

source - source iterable

mapper - mapper function to map from T to Iterable of R

Returns:

an iterable of type R that is the conceptual map of source using mapper

orElseOf

public static <T> Iterable<T> orElseOf(@Nonnull
                                       Iterable<T> source,
                                       @Nonnull
                                       T value)

Returns an alternative singleton iterable if the given source iterable is empty.

Type Parameters:

T - type parameter of the given iterable

Parameters:

source - source

value - value to use if source is empty

Returns:

an iterable of type T that returns the original iterable if it is not empty, or a singleton iterable composed of just value.

orElse

public static <T> Iterable<T> orElse(@Nonnull
                                     Iterable<T> source,
                                     @Nonnull
                                     Iterable<T> otherIterable)

Returns an alternative iterable if the given source iterable is empty.

Type Parameters:

T - type parameter of the given iterable

Parameters:

source - source

otherIterable - iterable to return if source is empty

Returns:

an iterable of type T that returns the original iterable if it is not empty, or otherIterable