com.diffplug.common.base

Class MoreCollectors

java.lang.Object

com.diffplug.common.base.MoreCollectors

public class MoreCollectors
extends java.lang.Object

Some useful collectors which aren't included as Java 8 built-ins.

Constructor Summary

Constructors

Constructor and Description
MoreCollectors()

Method Summary

Modifier and Type	Method and Description
static <T> java.util.stream.Collector<T,?,java.util.Optional<T>>	singleOrEmpty() Collector which traverses a stream and returns either a single element (if there was only one element) or empty (if there were 0 or more than 1 elements).
static <T> java.util.Optional<T>	singleOrEmptyShortCircuiting(java.util.stream.Stream<T> stream) Same behavior as MoreCollectors.singleOrEmpty(), except that it returns early if it is possible to do so.

Methods inherited from class java.lang.Object

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

Constructor Detail

MoreCollectors

public MoreCollectors()

Method Detail

singleOrEmpty

public static <T> java.util.stream.Collector<T,?,java.util.Optional<T>> singleOrEmpty()

Collector which traverses a stream and returns either a single element (if there was only one element) or empty (if there were 0 or more than 1 elements). It traverses the entire stream, even if two elements have been encountered and the empty return value is now certain. Implementation credit to Misha: http://stackoverflow.com/a/26812693/1153071

singleOrEmptyShortCircuiting

public static <T> java.util.Optional<T> singleOrEmptyShortCircuiting(java.util.stream.Stream<T> stream)

Same behavior as MoreCollectors.singleOrEmpty(), except that it returns early if it is possible to do so. Unfortunately, it is not possible to implement early-return behavior using the Collector interface, so MoreCollectors takes the stream as an argument. Implementation credit to Thomas Jungblut: http://stackoverflow.com/a/26810932/1153071