MoreCollectors

java.lang.Object
- com.google.common.collect.MoreCollectors

```
@GwtCompatible
public final class MoreCollectors
extends java.lang.Object
```
Collectors not present in java.util.stream.Collectors that are not otherwise associated with a com.google.common type.

Since:

21.0

Nested Class Summary

Nested Classes
Modifier and Type	Class	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.

Field Summary

Fields
Modifier and Type	Field	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`

Constructor Summary

Constructors
Modifier Constructor Description

private MoreCollectors()

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	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`.

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

- Field Detail
  - TO_OPTIONAL
```
private static final java.util.stream.Collector<java.lang.Object,?,java.util.Optional<java.lang.Object>> TO_OPTIONAL
```
  - NULL_PLACEHOLDER
```
private static final java.lang.Object NULL_PLACEHOLDER
```
  - ONLY_ELEMENT
```
private static final java.util.stream.Collector<java.lang.Object,?,java.lang.Object> ONLY_ELEMENT
```
- Constructor Detail
  - MoreCollectors
```
private MoreCollectors()
```
- Method Detail
  - toOptional
```
public 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. 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> java.util.stream.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.