MoreCollectors

java.lang.Object

com.google.common.collect.MoreCollectors

@GwtCompatible public final class MoreCollectors extends Object

Collectors not present in java.util.stream.Collectors that are not otherwise associated with a com.google.common type.

Since:: 21.0
Author:: Louis Wasserman

Method Summary

Modifier and Type

Method

Description

static <T> Collector<T,?,T>

onlyElement()

A collector that takes a stream containing exactly one element and returns that element.

static <T> Collector<T,?,Optional<T>>

toOptional()

A collector that converts a stream of zero or one elements to an Optional.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details
- toOptional
  
  public static <T> Collector<T,?,Optional<T>> toOptional()
  
  A collector that converts a stream of zero or one elements to an 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.
- onlyElement
  
  public static <T> Collector<T,?,T> onlyElement()
  
  A collector that takes a stream containing exactly one element and returns that element. The returned collector throws an IllegalArgumentException if the stream consists of two or more elements, and a NoSuchElementException if the stream is empty.