@GwtCompatible public final class MoreCollectors extends java.lang.Object
java.util.stream.Collectors
that are not otherwise associated
with a com.google.common
type.Modifier and Type | Class and Description |
---|---|
private static class |
MoreCollectors.ToOptionalState
This atrocity is here to let us report several of the elements in the stream if there were more
than one, not just two.
|
Modifier and Type | Field and Description |
---|---|
private static java.lang.Object |
NULL_PLACEHOLDER |
private static java.util.stream.Collector<java.lang.Object,?,java.lang.Object> |
ONLY_ELEMENT |
private static java.util.stream.Collector<java.lang.Object,?,java.util.Optional<java.lang.Object>> |
TO_OPTIONAL |
Modifier | Constructor and Description |
---|---|
private |
MoreCollectors() |
Modifier and Type | Method and Description |
---|---|
static <T> java.util.stream.Collector<T,?,T> |
onlyElement()
A collector that takes a stream containing exactly one element and returns that element.
|
static <T> java.util.stream.Collector<T,?,java.util.Optional<T>> |
toOptional()
A collector that converts a stream of zero or one elements to an
Optional . |
private static final java.util.stream.Collector<java.lang.Object,?,java.util.Optional<java.lang.Object>> TO_OPTIONAL
private static final java.lang.Object NULL_PLACEHOLDER
private static final java.util.stream.Collector<java.lang.Object,?,java.lang.Object> ONLY_ELEMENT
public static <T> java.util.stream.Collector<T,?,java.util.Optional<T>> toOptional()
Optional
. The returned
collector throws an IllegalArgumentException
if the stream consists of two or more
elements, and a NullPointerException
if the stream consists of exactly one element,
which is null.public static <T> java.util.stream.Collector<T,?,T> onlyElement()
IllegalArgumentException
if the stream consists of two or
more elements, and a NoSuchElementException
if the stream is empty.